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= Hedgehog Signalling Pathway =<br />
==Introduction==<br />
[[File:Hedgehog.jpg|thumb|300px|An image of a hedgehog, the animal of which the Hh proteins are named after.]]<br />
The Hedgehog (Hh) signalling pathway is an important part of the early embryo with regards to the patterning and development of the nervous system, limbs and the cranio-facial region in vertebrates and the polarization of the segments in the ''Drosophila'' embryo. It was first identified in 1980 by Christiane Nüsslein-Volhard and Eric Wieschaus, alongside a group of other genes regulating segment polarity in ''Drosophila'' embryonic development<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. The pathway itself consists of Hh proteins, where there are three identified homologs in vertebrates, being sonic hedgehog (SHH), Indian hedgehog (IHH), and desert hedgehog (DHH) <ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. All homologs are expressed at varying levels within different tissues in the body, and also act as a form of redundancy to an extent between one another. <br />
<br />
The signaling pathway is highly conserved between various species<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. and acts via a G protein coupled receptor like receptor, which uninhibited via the action of the Hh proteins. The pathway overall acts via a balance of dephosphorylation<ref name="PMID10966113"><pubmed>10966113</pubmed></ref> and degradation of proteins<ref name="PMID15102702"><pubmed>15102702</pubmed></ref> in order to regulate transcription factor activity to express various genes to carry out its action. The Hh pathway is also highly implicated when it comes to abnormalities in development, as it is implicated in diseases such as holoprosencephaly and cleft lip and palate. Overall Hh signaling pathways play a large role in embryological development, which will be discussed in detail on this page.<br />
<br />
== History ==<br />
{| class="pretty table"<br />
| '''1980'''<br />
|Christiane Nüsslein-Volhard and Eric Wieschaus first identified a group of genes including those related to the Hedgehog signalling pathway and linked them to the segmentation and planning of the embryo in ''Drosophila melanogaster'' by introducing mutagenic substances to the developing embryo<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Multiple researchers including Andrew P. McMahon and Clifford Tabin discovered three equivalent homologs in vertebrates of the ''Drosophila melanogaster'' hedgehog gene, known as sonic hedgehog (Shh), desert hedgehog (Dhh) and indian hedgehog (Ihh), by looking at DNA sequences similar to that of the gene in the fruit fly<ref><pubmed>7916661</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Clifford Tabin and his lab identified the role of Shh in localising the limb bud, where they identified protein to be expressed within a region of the limb bud known as the zone of polarising activity (ZPA), showing that SHH is sufficient to induce the production of a ZPA, and thus limb bud formation in chick embryos<ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|Sonic hedgehog secreted by the notochord was identified to induce ventral cell types in the neural tube during embryonic development, most notably the floor plate cells and the motor neurons as shown in chick embryos. Such differentiation between the two cell types is thought to be a matter of sonic hedgehog concentrations experienced by the neural plate cells<ref name="PMID7736596"><pubmed>7736596</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|A shared Nobel prize in physiology or medicine was awarded to Christiane Nüsslein-Volhard and Eric Wieschaus for their researching regarding the identification of the developmental genes relating to the formation and patterning of the early embryo via genes.<br />
|-<br />
|'''1996'''<br />
|Studies showed that human homologs of the Patched gene, a component of the hedgehog pathway, is a key gene that is mutated in Gorlin Syndrome, which characterised by a predisposition for basal cell carcinomas, the most common cancers in humans and developmental abnormalities<ref name="PMID8658145"><pubmed>8658145 </pubmed></ref>.<br />
|-<br />
|'''1999'''<br />
|Researchers implicated Indian hedgehog as a key signalling molecule for the maturation and differentiation of prehypertrophic chondrocytes, where Indian hedgehog null mice were shown to have a lack of mature chondrocytes and no development of osteoblast cells in endochondrial bone. This was thought to be due to Indian hedgehog having a feedback signal controlling parathyroid hormone related protein, which regulates endochondrial bone development<ref name="PMID10465785"><pubmed>10465785</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Sonic hedgehog was identified to regulate the proliferation of adult neural stem cells as shown in the hippocampus of rats and in vitro for neural progenitor cells isolated from the hippocampus<ref name="PMID12469128"><pubmed>12469128</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Studies on Shh function found that it can act as a chemoattractant in the developing embryo spinal cord, to help guide commissural axons to the midline of the floor plate<ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
|-<br />
|'''2009'''<br />
|Mouse models showed that reduction in hedgehog signalling allows for transient improved response to chemotherapy with regards to mouse models of human pancreatic ductal adenocarcinoma, a cancer with one of the highest mortality rates in humans<ref name="PMID19460966"><pubmed>19460966</pubmed></ref>.<br />
|}<br />
<br />
This time line regarding the discoveries in the hedgehog signalling pathway is by no means exhaustive, but a selection of relatively large discoveries that had a significant impact in the field on the basis of citations.<br />
<br />
== Origin of name ==<br />
<br />
[[File:Bands of denticles in normal and Hh mutant Drosophila embryo.jpeg|thumb|250px|Differences in patterning of the denticle bands in normal and mutated hedgehog gene variant ''Drosophilia'' embryo]]<br />
<br />
The name hedgehog came about when Christiane Nüsslein-Volhard and Eric Wieschaus first identified the group of genes controlling polarization of the segments in the ''Drosophila'' early embryo. They noticed that when they mutated the Hh gene, making it non-functional, that the bands of denticles formed during the early ''Drosophila'' embryo formation became more diffuse as opposed to being distinct normally. The denticles would all clump together forming a single patch on the surface of the embryo, as opposed to normally outlining the distinct segments of the embryo as bands<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. This gave the embryo spiny and prickly look similar to that of the back of a hedgehog.<br />
<br />
From there on in the gene was called the hedgehog gene where homologs in vertebrates discovered along the line kept to this naming structure giving various species of hedgehog names to the genes such as Indian hedgehog, and desert hedgehog, with the exception being sonic hedgehog, which is named after a fictional character in the video game “Sonic the Hedgehog”.<br />
<br />
== Mechanism of signalling ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br>[[File:Hh signalling pathway.jpg|thumb|600px|Diagrammatic representation of the steps and components involved in the hedgehog signalling pathway in both ''Drosophila'' and mammals.]]<br />
<br />
The Hh signaling pathway has been well studied in ''Drosophila melanogaster'', and has been shown the be conserved to an extent across it and mammals making the species a suitable model for Hh signalling in humans<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. In ''Drosophila melanogaster'', the Hh pathway begins when the Hh proteins bind to the extracellular domain of the transmembrane protein known as Patched (PTC). Such binding is thought to be greatly enhanced by the presence of proteins known as interference hedgehog (ihog) and brother of ihog (boi), which have shown to be essential to allowing hedgehog binding to inactivate PTC<ref name="p20048000 "><pubmed>20048000 </pubmed></ref>. It has also been demonstrated heparin sulfate proteoglycans (HSPG) such as dally also aid in the modulation of hedgehog signalling, where they act to localise and transport the hedgehog protein to the target receptors<ref name="p14602684"><pubmed>14602684</pubmed></ref> <ref name="p10549295"><pubmed>10549295</pubmed></ref>. Overall hedgehog binding leads to inactivation of PTC which occurs by Hh trapping PTC in an inactive conformational state<ref><pubmed>27647915</pubmed></ref>. After binding of Hh occurs to PTC and it is inactivated, the receptor and Hh protein is thought to be endocytosed by the cell where they undergo lysosomal degradation in order to limit Hh concentration, thus limiting its spread to other cells and PTC activity<ref name="PMID15102702"><pubmed>15102702</pubmed></ref>. In the absence of Hh, PTC acts to suppress the expression of the Smoothened (SMO), a G-protein coupled receptor like receptor, and thus its signaling. How PTC achieves this inhibition of SMO is currently unclear. Studies have suggested that due to the highly phosphorylated nature of SMO when active, that PTC acts to dephosphorylate SMO in order to repress its signaling. It is thus that binding of Hh to PTC reduces PTCs ability to promote dephosphorylation of SMO, leading to its increased activity and expression on the cell surface <ref name="PMID10966113"><pubmed>10966113</pubmed></ref>. It is thought that the phosphorylation required to activate SMO are dependent on protein kinase A (PKA) and casein kinase I (CKI) <ref><pubmed>15616566 </pubmed></ref>.<br />
<br />
This overall increased phosphorylation of SMO due to a repression of PTC activity by Hh leads to an accumulation of SMO on the cell surface, which collectively allows for SMO to exert its activity. Importantly the phosphorylation also disrupts intramolecular electrostatic interactions between SMO molecules which switches the molecule into its active conformational state <ref><pubmed>17960137 </pubmed></ref>. Generally, SMO has been shown to have very little signal transducing ability, and thus this accumulation allows it to jointly transduce a substantial signal. This occurs by the C terminus of SMO on the intracellular domain interacting with the kinesin like protein Costal-2 (Cos2), which is thought to bind to microtubules in order to acts as a scaffolding protein <ref><pubmed>18691888 </pubmed></ref>. Such interactions induce the formation of a complex including the kinase known as Fused (Fu) and Cos2, which phosphorylates Suppressor of Fused (SUFU) to inhibit it. Without this inhibition SUFU goes onto prevent the translocation of the transcriptional factor Cubitus interruptus (Ci) into the nucleus by leading to its phosphorylation, and subsequently its partial cleavage via the proteosome. The partial cleavage of Ci leaves a lower molecular weight protein known as Ci repressor (CiR) or Ci75, which translocates into the nucleus and acts to repress the target genes of the Hh signalling pathway via Ci<ref><pubmed>9215627</pubmed></ref>. Thus overall inhibition of SUFU increases the amount of Ci entering into the nucleus of the cell, and activating transcription of target genes of the Hh pathway<ref><pubmed>10952898 </pubmed></ref>. Activation of SMO also promotes disassociation of present SUFU-Fu-Cos2-Ci complex which which generally when fully intact leads to cleavage of Ci into its repressor form<ref name="p15063184"><pubmed>15063184</pubmed></ref><ref name="p17881487"><pubmed>17881487</pubmed></ref>.<br />
<br />
At this point Ci is able to activate the transcription of various genes, which include importantly the ''ptc'' gene, which encodes the PTC receptor. It is thus as a result of this, that PTC expression will be increased in response to Hh pathway induction, which negatively feeds back to reduce Ci signaling induction, in order to maintain homeostasis and regulate the intensity and duration of the signaling from Hh<ref><pubmed>9053330</pubmed></ref>. Furthermore the ''wg'' gene, encoding the wingless protein is also activated by Ci, which leads to activation of the Wnt pathway via the Frizzled receptor in adjacent cells expressing the gene ''engrailed'' <ref><pubmed>9502727</pubmed></ref> <ref><pubmed>10457026</pubmed></ref>. This overall stabalizes the boundaries between the segments of the developing ''Drosophila melanogaster'' signalled by the gene ''engrailed''<ref><pubmed>3282172</pubmed></ref>.<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=w1xXD9kss2w</html5media><br />
<br><br><br />
An overview of the hedgehog signalling pathway in ''Drosophila''<ref>YouTube. (2016). The Hedgehog signalling pathway in Drosophila online Available at: https://www.youtube.com/watch?v=w1xXD9kss2w</ref>.<br />
<br />
=== Mammals ===<br />
<br />
Although the Hh signaling pathway has been conserved across species to an extent <ref name="PMID8595881"><pubmed>8595881</pubmed></ref>, key differences exist when observing the pathway within mammalian tissue in contrast to that which has been studied in ''Drosophila melanogaster''. In mammalian cells and all other vertebrates, Hh signalling is dependent on an organelle known as the primary cilia, which are projections outwards from the cells surface. The importance of such an organelle in the signalling pathway comes as a result of PTC1, one of the two PTC receptor homologs in mammals, that binds to the Hh homolog Sonic Hh (Shh), exists within the cilia<ref><pubmed>17641202</pubmed></ref>. Similarities also exist between signalling in the vertebrates and ''Drosophila''. This includes the surface proteins such as Cdo and Brother of cdo (Boc), which act in a similar fashion to ihog and boi in enhancing the binding of the hedgehog protein to PTC<ref><pubmed>16647304</pubmed></ref>. HSPGs such as gylcipans (GPC) 1, 2, 3, 4, 5 and 6 are also thought to play a role in hedgehog signalling in vertebrates with regards to stimulaiton or inhibition of the pathway depending on the isoform<ref><pubmed>26627558</pubmed></ref>. The mechanism of action of SMO inhibition and activation is poorly understood currently, but evidence has suggested that PTC1 acts to inhibit SMO when unbound to Shh by acting as a pump to remove oxysterols from the cilia into the extracellular space<ref><pubmed>PMC1462959</pubmed></ref>. These oxysterols are normally thought to bind and accumulate around the SMO receptors, which in turn prevents internalization and deactivation of SMO, leading to it accumulating on the apical primary cilia<ref><pubmed>16136078</pubmed></ref>. Other studies have also suggested that Shh has a role in increasing phosphorylation of SMO via kinases such as CK1, which causes it to accumulate on the cilia<ref><pubmed>21695114</pubmed></ref>. Overall the net action of Shh initially is believed to cause accumulation of SMO at the cilia by inhibiting PTCH1 and phosphorylation of SMO.<br />
<br />
How SMO acts next is relatively unknown but, it has been shown to promote the disassociation between SUFU and Gli transcription factor, which allows Gli to be transported to the nucleus to activate effector genes of the pathway. Gli is normally bound in the cytoplasm to SUFU, where SUFU promotes the partial degradation of Gli into its repressor form, similar to that in the fruit fly model<ref><pubmed>20360384</pubmed></ref>. Alongside this, Kif7, a Cos2 homolog, has been shown to migrate to the apex of the cilium in response to SMO accumulation at the cilium, where it has been postulated to also promote disassociation of SUFU and Gli<ref><pubmed>19592253</pubmed></ref>. On the other hand, Kif7 is also thought to play an inhibitory role for the signalling pathway as when it is localized at the base of the cilia in the absence of Hh signaling, where it acts to traffic Gli transcription factors away from the cilia<ref><pubmed>19666503</pubmed></ref>. This all leads to an accumulation of active Gli transcription factors which migrate to the nucleus in order either inhibit or activate gene transcription in response to Hh signaling. These Gli transcription factors include Gli1, Gli2, and Gli3, where Gli2 and Gli3 in their activated form are the primary mediators of the pathway, and also act to repress the target genes when hedgehog signalling is absent. Gli3 is considered to be the major repressor of the pathway when the full length version of the Gli3 protein is partially cleaved into its repressor form <ref><pubmed>10433919</pubmed></ref>. Gli1 on the other hand is one of the targets of hedgehog signalling promoted by Gli2 and Gli3 activators, and acts to reinforce the hedgehog pathway through a positive feedback loop <ref><pubmed>10075717</pubmed></ref>. As a result Gl1 is considered as not entirely essential ,where mice models with no production of Gl1 have shown viability with few defects<ref><pubmed>10725236</pubmed></ref>. That being said, other studies have shown the importance of Gl1 as a downstream target of sonic hedgehog, where it is thought to induce ventral neural tube development, as it is on the only Gli factor present in the floor plate during gastrulation<ref><pubmed>9216996</pubmed></ref>. Overall the interactions between such transcription factors are still relatively unknown, where further research is required to elaborate on the specific roles in the hedgehog pathway they each have.<br />
<br />
== Function ==<br />
===Overview===<br />
{| class="pretty table"<br />
|'''Hedgehog protein homolog'''<br />
|'''Function'''<br />
|-<br />
| Sonic hedgehog [http://www.omim.org/entry/600725 OMIM entry] ||<br />
*Expressed in zone of polarizing activity of the limb bud where it plays a role in helping to pattern the anterior and posterior aspect of the limbs <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
*Based on time and concentration of SHH due to diffusion from the point of secretion in the limb bud, SHH also plays a role in determining digit identity <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>.<br />
*Acts as a chemoattractant to guide commissural axons in the floor plate of the neural tube towards the midline <ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
*Patterns the developing cusps of the teeth and their relative positions in the jaw, and is also essential for the growth of the teeth <ref name="PMID11044393"><pubmed>11044393</pubmed></ref>.<br />
*SHH released from the notochord acts to induce formation of the floor plate, motor neurons, and dopaminergic neurons, as well as signalling the induction of the ventral cell types in the neural tube <ref name="PMID8790332"><pubmed>8790332</pubmed></ref>.<br />
|-<br />
| Desert hedgehog [http://www.omim.org/entry/605423 OMIM entry]||<br />
*Plays a possible role in regulating spermatogenesis as due to the highly localised expression in the testes by pre-Sertoli cells, and the fact that mice with no DHH present are infertile, with no mature spermatozoa <ref name="PMID8805249"><pubmed>8805249</pubmed></ref>. <br />
*DHH derived from Schwann cells signal development of peripheral nerves, by inducing the production of a connective tissue sheath around them <ref name="PMID10482238"><pubmed>10482238</pubmed></ref>.<br />
|-<br />
| Indian hedgehog [http://www.omim.org/entry/600726 OMIM entry]||<br />
*Aid in the signalling of proliferating chondrocytes to undergo hypertrophic differentiation during endochondral ossification<ref name="PMID8662546"><pubmed> 8662546</pubmed></ref>.<br />
*Plays a key role in yolk sac angiogenesis, as seen in studies where an absence of IHH leads to death of the embryo due to poor yolk sac vasculature <ref name="PMID11807029"><pubmed>11807029</pubmed></ref>.<br />
|}<br />
<br />
===Limb development===<br />
<br />
====Research background====<br />
<br />
The hedgehog signalling pathway plays a significant role with regards to the embryonic development of the limbs in vertebrates, specifically SHH. For a while the mechanism of which the limb was patterned on the anterior to posterior axis was quite unknown. Early studies had shown that grafting posterior wing bud cells to the anterior region of the wing bud in a chick embryo, an equal amount of extra digits was produced to that of which was normally produced, and in a mirror image pattern<ref name="PMID4390734"><pubmed>4390734</pubmed></ref>. This showed that the pattern of which the digits were produced were polarized with respect to that of the graft from the limb bud, which has become to be described as the zone of polarizing activity (ZPA). Further studies mapped the ZPA, by showing the area of the wing bud on the chick with the highest polarizing activity to be the posterior margin of the wing bud<ref name="PMID4719010"><pubmed>4719010</pubmed></ref>. Furthermore, studies later on found that the amount or concentration of ZPA cells grafted played a role in the amount of digits induced and how polarized they were<ref name="PMID7453825"><pubmed>7453825</pubmed></ref>. This ultimately gave rise to studies regarding a potential morphogen, which could potentially provide this concentration dependent activity of polarization when it comes to the limb bud. Studies to find this morphogen led to the discover of the ability for retinoic acid to mimic the polarizing action of the ZPA when applied locally to the limb bud<ref name="PMID7070499"><pubmed>7070499</pubmed></ref>. This was found to be due to the induction of a second morphogen known as SHH, where when cells that express SHH are grafted onto the limb bud, polarized digit development is induced<ref name="PMID7720566"><pubmed>7720566</pubmed></ref>.<br />
<br />
====Polarizing activity of sonic hedgehog====<br />
[[File: Mechanims of patterning the digits on the posterior to anterior axis of the limb bud by sonic hedgehog.jpg|thumb|450px|Regions of the limb bud and the digits they form based on patterning of the posterior to anterior axis of the limb bud by mechanisms mediated by sonic hedgehog.]]<br />
More recent studies have sought to elucidate how SHH mediates such a polarizing effect in terms of digit identification and its underlying mechanism. It has been suggested that such an effect is heavily concentration dependent similar to that of when transplanting the chick wing bud ZPA cells, acting in a dose dependent matter, due to the ability of SHH to modulate signaling at long ranges via diffusion<ref name="PMID11389830"><pubmed>11389830</pubmed></ref>. This implies that a gradient of varying concentrations of SHH diffused through the mesenchyme of the limb bud leads to the identification of posterior and anterior digits.<br />
<br />
Current research has also suggested that not only is the concentration gradient of SHH important for the patterning of the digits, but also the temporal gradient, being the length of time of exposure of SHH to the mesenchyme of the limb bud. Studies have shown in mice that of the 5 digits, polarization from the posterior end, being digit 5, to the anterior end being digit 1 are due to different mechanisms. Digits 5 and 4 have been shown to be comprised of the SHH expressing cells and thus both experience maximal levels of SHH, and thus cannot be distinguished on the basis of a concentration gradient. As a result, temporal gradients are employed, where the expression of SHH in both regions that become the digits vary, where studies have shown that SHH expression in the primordium of digit 5 is maintained longer than that in digit 4 gradient <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>. When it comes to digit 3 and 2, there is differentiation based on the concentration gradient of SHH from the ZPA, where due to the ZPA being further away to digit 2 than 3, the concentration of SHH will be higher at 3<ref name="PMID15315763"><pubmed>15315763</pubmed></ref> <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>. In terms of digit 1, the levels of SHH are so low at this point that it is said to be SHH independent, and actually reliant on the absence of SHH for normal differentiation. With regards to how SHH actually mediates its action, it is thought to be by a balance between the transcription factor Gli3 and SHH expression, which activates Gli1, Gli2 and Gli3 repressor, effectively counteracting Gli3. Gli3 is considered to promote the inhibition of digit formation and identification, while the downstream targets of SHH are thought to promote it<ref name="PMID17400206"><pubmed>17400206</pubmed></ref>.<br />
<br />
Other research has also shown the possibility of SHH signaling as a way to prime the posterior mesenchyme and induce the production of bone morphogenetic protein 2 (bmp2), which is thought to be the morphogen creating the chemical gradient for digit identification<ref name="PMID10704381"><pubmed>10704381</pubmed></ref>. Overall the mechanism at which SHH work to pattern the posterior anterior axis of the limb bud is still relatively unknown, and further research is being conducted to elucidate how the underlying mechanisms such as the downstream targets of SHH affect digit formation.<br />
<br />
=== Neural development ===<br />
<br />
====Research background====<br />
Research on the role of the notochord, a cartilaginous structure derived from the mesoderm, initially observed its ability to induce the floor plate within the neural tube of chick embryos<ref name="PMID3354847"><pubmed>3354847</pubmed></ref>. This induction of a floor plate occurred in the ventral midline of the neural tube, where the floor plate itself is thought to have signalling effects regarding patterning of the spinal cord. Alongside this, research also noted that the floor plate and notochord collectively had signalling effects that patterned the differentiation of the neural cells in the neural tube<ref name="PMID1991324"><pubmed>1991324</pubmed></ref>. Such observations lead to research being directed at how this patterning of the neural tube is mediated through the notochord. It had been suggested that the morphogen known as Shh was to play due to its high expression within the notochord and floor plate. It also was showed to activate floor plate expressed genes when ectopically expressed in the mouse CNS<ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. Furthermore, observations regarding the Shh also lead to implicating it in the differentiation of distinct cell types in the ventral neural tube such as motor neurons, alongside the already identified floor plate<ref name="PMID8124714"><pubmed>8124714</pubmed></ref>. Studies looking specifically at the targets of Shh signalling in the neural tube also identified that using antibodies to block the protein would lead to blocking of the induction of the motor neurons, and that applying Shh to explants induced floor plate and motor neurons in a variety of vertebrate models<ref name="PMID7753196 "><pubmed>7753196 </pubmed></ref>. This for the most part formed the basis of research on the specific patterning effects of Shh secreted from the notochord and floor plate on the ventral neural tube.<br />
<br />
====Patterning of ventral nerve cell types in the neural tube====<br />
[[File: Regions of varying neural cell types in ventral neural tube.jpg|thumb|400px|Different areas of ventral nerve cell types including inter-neurons and motor neurons on the neural tube induced by the graded signalling of Shh secreted from the floor plate and notochord.]]<br />
As stated, the inductive signals from the notochord in the form of Shh <ref name="PMID7753196"><pubmed>7753196 </pubmed></ref> are primarily responsible for the formation of the floor plate in the ventral midline of the neural tube during embryonic development<ref name="PMID3354847"><pubmed>3354847</pubmed></ref>. The floor plate itself acts in the same fashion as the notochord with regards to expression of Shh for mediatating its signal. Collectively it is thought that the notochord and the floor plate provide a Shh graded response, where there is a gradient of concentrations along the dorsoventral axis of the developing neural tube<ref name="PMID9598380"><pubmed>9598380</pubmed></ref>. As a result, it is believed that the degree of Hh signalling on a cell type is responsible for the differentiation of progenitor cells it to various types. Specifically, with regards to the floor plate, the distinct local signal, given the close proximity of the notochord to the floor plate induction site is responsible for inducing the floor plate<ref name="PMID9598380"><pubmed>9598380</pubmed></ref>. It is thought that through interacting with the receptor PTC, the pathway activates the transcription of hepatocyte nuclear factor 3β (HNF-3β), a gene that has been shown to be commonly expressed in the floor plate. Such a gene is activated by the transcription factors Gli1 and Gli2. Thus HNF-3β is considered to be the downstream target of Shh signalling leading to the induction of the floor plate<ref name="PMID9118802"><pubmed>9118802</pubmed></ref>. It is also believed that HNF-3β is essential for notochord formation as well, as seen in mice models with HNF-3β knocked out, leading to dorsoventral patterning issues<ref name="PMID8069909"><pubmed>8069909</pubmed></ref>. Overall the induced floor plate acts to further aid the notochord in producing a graded Shh response to pattern the ventral neural tube<ref name="PMID1991324"><pubmed>1991324</pubmed></ref>.<br />
<br />
With regards to the patterning of the ventral cell types, Shh is able to differentiation the progenitors within the neural tubes into 5 different classes, which include interneurons V0, V1, V2, V3 and motor neurons. As stated previously, it is thought that such differentiation is via the gradient of Shh along the dorsoventral axis, where more ventrally there is a higher concentration of Shh gradually decreasing as you move dorsally<ref name="PMID9598380"><pubmed>9598380</pubmed></ref>. This gradient acts upon the neural progenitors which cause the expression or inhibition of homeodomain transcription factors depending on the cell type they will differentiate to, acting as intermediaries for the Shh signalling to promote patterning<ref name="PMID15936325"><pubmed>15936325</pubmed></ref>. In the context of these transcription factors and hedgehog signalling, studies have shown that at very low concentrations of Shh initially inhibits the Pax7 transcriptional factor, which allow for the formation of the general ventral population of neural progenitors<ref name="PMID8929535"><pubmed>8929535</pubmed></ref>. The ventral progenitor cells will now express varying different factors in response to the graded Shh signalling leading to the defined boundaries of the 5 different nerve cell types. These boundaries are produced by the interaction of these factors, which are split into two classes, class I and class II. The class I factors are Shh repressed and include Pax7, Irx3, Dbx1, Dbx2, and Pax6, while class II consists of Shh induced proteins such as Nkx6.1 and Nkx2.2<ref name="PMID10830170"><pubmed>10830170</pubmed></ref>. The classes act to repress one another, and when expressed in varying concentrations in response to the interactions between one another and Shh signalling, various distinct domains which represent the various ventral cell types are formed. Specifically, Nkx2.2 identifies the V3 interneurons (most ventral) <ref name="PMID10217145"><pubmed>10217145</pubmed></ref>, while induction of MNR2 and Lim3 via Nkx6.1 in the motor neuron domain produces the motor neurons<ref name="PMID9778248"><pubmed>9778248</pubmed></ref>. Furthermore, Nkx6.1 from the motor neuron domain acts to induce Lim3, while Irx3 in the V2 region inhibits MNR2 to prevent formation of motor neurons to pattern the region containing V2<ref name="PMID10830170"><pubmed>10830170</pubmed></ref>. Finally, Dbx1 is critical for V0 interneuron generation (most dorsal) and Dbx2 is for V1 generation<ref name="PMID11239429"><pubmed>11239429</pubmed></ref>. As described above there are complex interactions between homeobox transcription factors that are activated or inhibited by Shh signalling and are expressed at different concentration given the concentration gradient of Shh. These come together as a whole to produce very distinct regions in the ventral neural tube containing different cell types.<br />
<br />
=== Organogenesis ===<br />
Organogenesis is a term used to describe the process of development of organs within plants or animals. The Hedgehog Signalling pathway is a pathway sending information to embryonic cells which plays an especially important role in the regulation of organogenesis. These processes include the organization of the brain (craniofacial) and the growth of appendages with further studies implicating the Hedgehog Signalling pathway in the development of the small intestine, lungs, the pancreas as well as the skeleton. Research performed via vertebrate model organisms in recent years has lead to an increased understanding of the role of the endoderm in organogenesis, in particular the respiratory and gastrointestinal tracts. As stated previously, there are three Hedgehog protein homologues; Desert Hedgehog Homologue (DHH), the Indian Hedgehog Homologue (IHH) and the Sonic Hedgehog Homologue (SHH) of which SHH is the most extensively studied.<br />
<br />
Previous research has shown that SHH is expressed within the definitive endoderm during the infantile stages of gut organogenesis. Within underlying mesoderm, genes encoding for bone morphogenetic protein 4 (bmp4) and the Abd-B subclass of Hox genes were discovered <ref name="PMID7588051"><pubmed>7588051</pubmed></ref>. Bmp4 is related to Transforming Growth Factor Beta (TGF-β) and functions in normal growth of the visceral mesoderm; studies of knockout mice have shown organ abnormalities upon the removal of said gene <ref name="PMID25401122"><pubmed>25401122</pubmed></ref>. On the other hand, Hox genes are implicated in the regulation of embryonic development. Further research into the nuances of SHH have displayed that SHH by itself allows for induction of bmp4 and Hox genes in the mesoderm itself due to the restriction of SHH expresson to embryonic gut regions alongside the simultaneous detection of proteins <ref name="PMID7588051"><pubmed>7588051</pubmed></ref>. As a result, it is theorized that SHH helps induce epithelial mesenchymal interactions within the process of hindgut organogenesis <ref name="PMID17016847"><pubmed>17016847</pubmed></ref>.<br />
<br />
SHH is found to play an important role in lung organogenesis, evidence relating lowered levels of SHH signalling with pulmonary hypoplasia <ref name="PMID12547712"><pubmed>12547712</pubmed></ref>. It has been found that there is increased expression of SHH at the site of branching of the lung epithelia, suggesting a regulatory role in the progression of the respiratory tract. This is further supported by ectopic expression of SHH showing increased cell proliferation alongside an inhibition of epithelial branching <ref name="PMID9768363"><pubmed>9768363</pubmed></ref>. Experiments conducted with SHH knockout mice display the characteristics of an improperly separated trachea and esophagus alongside a significant structural downgrade of the lung due to the detrimental effect of respiratory tract organogenesis.<br />
<br />
It is well known that DHH is related to testis organogensis, however, it is only recently that researches have elucidated its functions in relation to both Leydig and Sertoli cells. It has been found that DHH signalling causes Leydig Cell differentiaion through the increased expression of Steroidogenic Factor 1 (SF1) and Cholesterol Side Chain Cleavage Enzyme within Protein Patched Homolog 1 (PTCH1) cells which are receptors for SHH outside the testis cordis <ref name="PMID186321"><pubmed>186321</pubmed></ref>. DHH help signal molecules which are expressed exclusively in the testis and are thus thought to play part in spermatogenesis. This is evidenced by research showing female DHH knockout mice displaying no phenotype, contrasted to male DHH knockout mice displaying infertility. The fact that DHH is found to be expressed in pre-Sertoli cells also asserts its role in male sexual differentiation. Futher analysis of embryonic and developing mouse testis highlights the role of DHH in regulation of both infantile and later stages of spermatogenesis <ref name="PMID8805249"><pubmed>8805249</pubmed></ref>.<br />
<br />
Only recently has IHH been implicated in the morphogenesis of the endochondral skeleton, with plenty of factors relating to this subject still yet to be elucidated. IHH signalling has been associated with regulation of chondrocyte maturation through a feedback loop of Parathyroid Hormone related Peptide (PTHrP), occuring at articular surfaces of the skeleton <ref name="PMID316949"><pubmed>316949</pubmed></ref>. PTHrP itself has many functions, one of which is the local reabsorption of bone. Studies performed with IHH knockout mice implicate a larger role of IHH in the development of the adult skeleton, mutants showing significant reduction in chondrocyte proliferation. Other important indicators of reduced skeleton developmental capacity include a failure in osteoblast development as well as mistimed chondrocyte maturation <ref name="PMID316949"><pubmed>316949</pubmed></ref>.<br />
<br />
== Animal models ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br>[[File:Hedgehog signalling on plane polarity of denticles in Drosophila.png|thumb|400px|Image of denticles on the ''drosophila'' embryo used as a model to research plane polarization of cells by looking at the orientation of the denticles on the ''drosophila'' embryo in response to many signalling molecules including hedgehog.]]<br />
<br />
Hedgehog (Hh) protein signal was initially discovered through experimentation on the fruit fly, "Drosophila melanogaster". It is through this model that we are able to discover not only the functional components of this pathway but also understand its role in embryonic development. Through application of this information on the human biological system we are able to find the cause and thus potential treatments of defects and diseases caused by interruption or mutation of the Hedgehog signalling pathway. <br />
<br />
Upon further research on Drosophila it was found that Hh may play a role in germ cell proliferation and in particular, may control the proliferation and activity of somatic cells found within the germarium, which is the most anterior structure within the Drosophila ovary. <ref>Ovaries (Drosophila) definition. (2016). Groups.molbiosci.northwestern.edu. Retrieved 10 September 2016, from http://groups.molbiosci.northwestern.edu/holmgren/Glossary/Definitions/Def-D/Drosophila_Ovaries.html</ref> Thus, the Hh signalling pathway is vital in egg chamber formation and its consequent envelopment, budding and polarisation. It has also been observed that somatic cell proliferation is dependent on this pathway and thus, the number of pre-follicle cells is subject to the effect of the Hh signalling pathway. <ref><pubmed>8620839</pubmed></ref> Further studies have also indicated the role played by this pathway in activating the Epidermal growth factor receptor (EGFR) signalling pathway as seen in the induction of EGFR by Hh in Drosophila head development. <ref><pubmed>10331974</pubmed></ref> In addition, research on Drosophila has indicated the direct effect of Hh signalling on tracheal branch patterning. <ref><pubmed>11290298</pubmed></ref><br />
<br />
Despite ongoing research on "Drosophila melanogaster" to uncover the workings of the Hedgehog signalling pathway, further research is needed to confirm and further current findings. In addition, it is evident that it is through the study of these fruit flies that we are able to gain a basis of understanding of the causes of certain human diseases and thus propel research into treatments for sufferers.<br />
<br />
===Blockage of Shh Signalling in Forebrain Neuroectoderm of Chick Embryos===<br />
<br />
The Hedgehog signalling pathway plays a significant role in embryonic development, particularly of the forebrain. Due to its role in development of craniofacial features by contributing to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm, a disruption in this pathway can result in a variety of birth deformities including holoprosencephaly (HPE), where the prosencephalon (forebrain) fails to divide into 2 separate hemispheres, telencephalon and diencephalon <ref>Holoprosencephaly - NORD (National Organization for Rare Disorders). (2016). NORD (National Organization for Rare Disorders). Retrieved 10 September 2016, from http://rarediseases.org/rare-diseases/holoprosencephaly/</ref>, as well as cleft lip and palate. The function of Sonic Hedgehog (Shh) and its signalling pathway on the formation of forebrain neuroectoderm was studied in chick embryos.<br />
<br />
It was found that the disruption of Shh signalling in the neural tube of chick embryos resulted in the lack of division of the forebrain into the diencephalon and telencephalon. This is in fact, as stated earlier, the fundamental cause of the rare condition, holoprosencephaly. It was discovered that the Shh signalling pathway in the diencephalon was responsible for gene expression in the telencephalon. <br />
<br />
In addition, through experimentation on chick embryos it was found that through Shh signalling the development of the forebrain regulates and controls facial morphogenesis, particularly of the upper and middle face. Therefore, interference with Shh signalling in the forebrain prevents this intrinsic communication, thus hindering Shh expression in facial ectoderm. This results in brain malformation accompanied by facial disfiguration as seen in patients suffering from HPE. Other malformations caused by blockage of Shh signalling in craniofacial development include, hypotelorism (decreased space between the orbits), growth restriction as well as cleft lip and palate as mentioned previously. <br />
<br />
A commonality discovered among all forms of Shh signalling disruption was two facial defects, “the loss of mediolateral expansion of the face and absence of proximodistal outgrowth of the frontonasal prominence”<ref><pubmed>15979605</pubmed></ref>. Through reference to studies performed on chick and mice embryos, it was found that Shh signalling is particularly vital in development of maxillary and frontonasal components of the cranium.<br />
<br />
This breakthrough study on the inhibition of Shh signalling in chick embryos has significantly filled the gap in our understanding of the Sonic Hedgehog signalling pathway. It is evident that this pathway is crucial in the development of the forebrain and in turn regulates and controls the development of the facial skeleton. This is further proven through the observation that in the event of Shh signalling inhibition there is a development of craniofacial malformations.<br />
<br />
=== Shh knockout mice ===<br />
<br />
Extensive research on Shh knockout mice allowed discovery of the roles of Shh in embryonic development and patterning of the limb buds and sclerotomes, and maintenance of the notochord. <ref><pubmed>8837770</pubmed></ref> These mice expressed defects in the cephalic neural tube with the fusion of telencephalic and optic vesicles. Through this research it is evident that Shh is partially responsible for the subdivision of the eye field through forebrain optic stalk development, along with formation of the ventral midline. It is these forebrain abnormalities established in the absence of Shh that results in congenital malformations of holoprosencephaly, development of a single nasal chamber and other facial defects in humans. <br />
<br />
The absence of the vertebral column including, the intervertebral discs and vertebrae along with the medial regions of the ribs were observed within Shh knockout mice. This lack of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population . In addition, though the role of Shh in patterning the anterior-posterior limb axis is evident through anterior limb bud cell death in the absence of Shh, it is also responsible for the development of proximal-distal limb segments, particularly in the patterning of structures at the level of or distal to the latent elbow and knee joints. <ref><pubmed>11476582</pubmed></ref> This was perceived after observing the incomplete formation of distal limb structures with abnormal anterior-posterior axis formation (Chiang et al., 2001). Thus, Shh knockout mice provide great insight into the functions of Shh in embryonic development and the abnormalities formed in the absence of this signalling protein.<br />
<br />
== Clinical Significance ==<br />
<br />
===Gorlin Syndrome===<br />
[[File:1 week year old newborn girl with cleft lip and palate.png|thumb|An image of a 1 week year old newborn girl with cleft lip and palate]]<br />
Gorlin syndrome, also known as nevoid basal cell carcinoma syndrome, is a heritable disease resulting from heterozygousity in Hh receptor, Patched (PTC). The PTC gene encodes a protein which binds sonic hedgehog (Shh) and it is this binding which inhibits the Hh signalling pathway. However mutation of PTC leads to activation of the pathway <ref><pubmed>9620294</pubmed></ref>. The syndrome is characteristic of skin cancer basal cell carcinoma and cerebellum cancer medulloblastoma. 1-2% of medulloblastomas and 0.5% of basal cell carcinomas are attributable to the disease. Patients present with craniofacial and brain abnormalities such as cleft palate, strabismus, macrocephaly, abnormal development of the corpus callosum and frontal bossing, with an overall overgrown appearance. Skeletal defects such as of the shoulder, ribs and vertebrae are often seen, as well immobile thumbs and polydactyly, which is a deformity of the hand or feet in which they have one or more extra fingers or toes. Apart from physical anomalies, patients have an increased risk of tumours throughout the body including cardiac, ovarian fibromas, ovarian dermoid cysts, meningiomas, and fibrosarcomas. Additionally with time, patients eventually undergo intracranial calcification and dyskeratotic pitting of the hands and feet whereby skin cells prematurely convert to keratin <ref><pubmed>8681379</pubmed></ref>.<br />
<br />
===Holoprosencephaly===<br />
<br>[[File:Semilobar holoprosencephaly.jpg|thumb|240px|MRI of fore brain depicting semilobar holoprosencephaly]]<br />
Holoprosencephaly (HPE) is a congenital disease caused by incomplete division of the prosencephalon (embryonic forebrain) into separate lobes of the cerebral hemispheres. The Shh gene has been identified as a HPE-causing gene however recent evidence has also investigated into the PTC gene, which acts to repress Shh signalling. A gain in repressive action of PTC is seen, leading to decreased Shh signalling, and thus HPE <ref><pubmed>11941477</pubmed></ref>. Clinical expression is variable between patients and is dependent upon the 3 forms of increasing severity: lobar, semi-lobar and alobar HPE, where patients can present with right and left ventricles however with a continuous frontal cortex in lobar HPE, to carrying a single cerebral ventricle in alobar HPE. Along with forebrain abnormalities, facial anomalies are also seen including midline cleft lip and/or flat nose, ocular hypotelorism characteristic of a small distance between the eyes. In severe rare cases of cyclopia, a non-functioning nose may be observed in the form of proboscis and the patient may present with a single eye at the root of the nose <ref><pubmed>20583177</pubmed></ref>. Furthermore, patients with HPE often develop a large number of medical issues including epilepsy, mental retardation, thyroid and adrenal hypoplasia due to lack of hypothalamus or pituitary gland development, and diabetes insipidus.<br />
<br />
===Medulloblastoma===<br />
Medulloblastoma is a cancerous tumour of the cerebellum where the cells of origin are the granular cell precursors found in the neonatal cerebellum, explaining its high prevalence in children <ref><pubmed>19171780</pubmed></ref>. Commonly, medulloblastomas are found deep in the cerebellum along the midline, however with desmoplastic medulloblastomas, they are found more laterally and superficial. As seen previously with Gorlin syndrome and holoprosencephaly, PTC is also associated with the development of medulloblastoma, and misregulation of Hh-PTC signalling in cells of the external germinal layer, the layer found on the surface of the cerebellum, is thought to give rise to the tumour. In experimental studies, it has been discovered that PTC is highly transcribed in medulloblastomas and in approximately 30% of PTC heterozygous mice the tumour develops <ref><pubmed>9205058</pubmed></ref> <ref><pubmed>9262482</pubmed></ref>. In patients with medulloblastoma, often children, the most common symptoms seen are vomiting, ataxia, psychomotor regression, drowsiness and anorexia. With age, patients are seen to get more frequent headaches, and show psychological symptoms such as behavioural problems, poor performance in school, and anxiety. In patients exhibiting life-threatening symptoms due to increased intracranial hypertension, bradycardia, convulsions and coma are often seen <ref><pubmed>21537925</pubmed></ref>.<br />
<br />
Watch below for a breakdown on Hedgehog's role in Tumour Development!<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=gFWO3I-oqsE</html5media><br />
<br><br><br />
An overview of the Hedgehog Signalling Pathway in Tumour Development<ref>YouTube. (2016). The Hedgehog Signaling in the Tumor Microenvironment - Research Hedgehog online Available at: https://www.youtube.com/watch?v=gFWO3I-oqsE</ref>.<br />
<br />
<br />
<br />
== Current research ==<br />
As a result of the Hedgehog Pathway's roots in many fundamental processes of embryonic development, there are many pathways that current and future research can take. One such heavily researched pathway today is the implication and subsequent targeting of the Hedgehog Pathway in cancer. What is known is the role of improper activation of the Hedgehog Pathway leading to tumorigenesis and subsequently, basal cell carcinoma or medulloblastoma <ref name="PMID3126020"><pubmed>3126020</pubmed></ref>. Organs reliant on the Hedgehog Pathway for development also display imporper activation of this pathway when stricken with cancer and recent research has also linked an increased propensity for the spread of tumour cells with over activation. It can thus be theorized that inhibition of Hedgehog Pathway signalling could in turn lead to the reduction of tumour spread and indeed, prevention of the cancer as a whole. One such orally applicable Hedehog Signalling Pathway antagonist GDC-0449 or Vismodegib has been shown to novelly cause apoptosis within pancreatic cancer stem cells by caspase-3 activation and Poly ADP ribose polymerase (PARP) cleavage <ref name="PMID22087285 "><pubmed>22087285 </pubmed></ref> . Vismoedgib has also shown promise through a reduction in adverse events in patients with inoperable basal cell carcinoma <ref name="PMID25981813 "><pubmed>25981813 </pubmed></ref><br />
<br />
==Quiz==<br />
<br />
<quiz display=simple><br />
<br />
{Which of the following are the reasons that are thought to allow for the patterning of digits in vertebrates.<br />
|type="[]"}<br />
+ &nbsp;Concentration gradient of sonic hedgehog.<br />
+ &nbsp;Temporal gradient of sonic hedgehog.<br />
- &nbsp;The varying homologs of the hedgehog proteins .<br />
- &nbsp;The length of the hedgehog molecule.<br />
+ &nbsp;No sonic hedgehog signalling.<br />
- &nbsp;The type of cholesterol attached to the hedgehog molecule.<br />
||<br> For differentiation of the individual digits in mice to occur it is thought that each digit requires a different signalling mechanism. Digits 5 and 4 which are most posterior, are derived from the region around the zone of polarising area which contain Shh secreting cells, meaning these regions will experience a saturation of Shh signalling and cannot be differentiated by Shh concentration. As a result it is thought that these digits are identfied based on the temporal gradient, meaning that the length of which Shh is expressed in these regions differentiates the digits from one another with digit 5 expressing Shh for longer. Digits 3 and 2 are further away but still receive Shh signalling due to the diffusible nature of Shh from the ZPA, which forms a concentration gradient. This means the the concentration at digit 2 will be less than digit 3 due to being further away from the ZPA and thus can be differentiated from one another based on this concentration. Finally the digit 1 is differentiated on the basis of not receiving any Shh signalling at all. Thus it is a combination of concentration gradient of Shh, temporal gradient of Shh, and independence from Shh.<br />
<br />
{Which of the following are correct with regards to the hedgehog signalling pathway in ''Drosophila''.<br />
|type="[]"}<br />
-&nbsp;It occurs at the cillum on the cell surface.<br />
-&nbsp;Hedgehog protein binding to the Patched receptor activates it to inhibit Smoothened.<br />
+&nbsp;Hedgehog protein binding to the Patched recetpor inhibits it to activate Smoothened. <br />
+&nbsp;Inhibition of SUFU is critical in allowing Ci to translocate into the nucles and activate downstream targets of the hedgehog pathway.<br />
-&nbsp;The pathway contains 3 homologs including sonic hedgehog, Indian hedgehog, and desert hedgehog.<br />
-&nbsp;The hedgehog protein is initially produced in its fully active form.<br />
||<br> In terms of how the hedgehog protein acts to produce its effect, it must first bind to Patched which activity is inhibiting Smoothened in the absence of the hedgehog protein. The protein acts to trap Patched in its inactive confirmational state cause internalisation and eventually degradation of the receptor. This relives the dephosporylation of the Smoothened, usually induced by Patched, allowing it to accumulate phosphate groups and thus activate. With regards to Ci translocation, SUFU usually inhibits this by leading to phosphorylation of Ci and eventually its cleavage into Ci repressor. During the activation of the hedgehog pathway there is a binding of Fused to Cos2 which phosphorylates SUFU to inactivate it, allowing Ci to translocate into the nucleus and activate downstream targets.<br />
<br />
{What are some of the roles of the Hedgehog signalling pathway in embryonic development as discovered through animal models? (select one or more options)<br />
|type="[]"}<br />
- &nbsp; Development of the hindbrain <br />
+ &nbsp; Activates the Epidermal growth factor receptor (EGFR) signalling pathway<br />
+ &nbsp; Development of craniofacial features<br />
- &nbsp; Development of the spinal nerves and meninges<br />
+ &nbsp; Development and patterning of the limb buds and sclerotomes<br />
||<br> The Hedgehog signalling pathway plays a significant role in forebrain, not hindbrain, development. Absence of this pathway results in holoprosencephaly (HPE), the lack of division of the forebrain into its 2 separate hemispheres, telencephalon and diencephalon.<br />
<br />
Studies on Drosophila melanogaster have indicated the role of the Hedgehog signalling pathway in the activation of the EGFR pathway in Drosophila head development.<br />
<br />
This pathway also plays a significant role in the development of craniofacial features, as it contributes to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm. Blockage of Shh signalling in chick embryos provides inside into the birth defects associated with lack of Shh involvement in craniofacial development. These defects include holoprosencephaly and, cleft lip and palate.<br />
<br />
The role of Hh signalling pathway in development of spinal nerves and meninges has not been observed within animal models but as discussed above, this pathway plays a significant role in other areas of embryonic development, such as forebrain and craniofacial development, germ cell proliferation, subdivision of the eye field, production of sclerotomes and patterning of limb buds.<br />
<br />
The role of this pathway in development and patterning of limb buds and sclerotomes was observed through experimentation on Shh knockout mice. The absence of this pathway resulted in a lack of vertebral column development. This deficiency of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population. Anterior limb bud cell death was also observed in these mice, indicating the role of Shh in patterning the anterior-posterior limb axis and even the proximal-distal limb segments, particularly in patterning of structures at the level of or distal to the latent elbow and knee joints. <br />
<br />
{A patient presents with crossed eyes, a pronounced forehead and an abnormally large head. Through an ultrasound it was also revealed the patient has an ovarian fibroma. Which of the following is the patient diagnosed with?<br />
|type="[]"}<br />
- &nbsp; Holoprosencephaly<br />
- &nbsp; Medulloblastoma<br />
+ &nbsp; Gorlin Syndrome<br />
- &nbsp; Cowden Syndrome<br />
||<br> The symptoms present in the patient correlate with Gorlin Syndrome. The patient is cross-eyed due to suffering from strabismus where the eyes do not properly align with eachother. A pronounced forehead is characteristic of frontal bossing and a large head is due to macrocephaly. Macrocephaly can arise due to an enlarged brain or excessive cerebrospinal fluid in the brain. Hedgehog, as well as being a developmental morphogen, regulates the proliferation and survival of stem cell populations, explaining its involvement in development of tumours. Patients with Gorlin syndrome often develop tumours throughout the body. <br />
<br />
</quiz><br />
<br />
==Glossary==<br />
<br />
{| class="pretty table"<br />
|-<br />
|'''Term'''<br />
|'''Definition'''<br />
|-<br />
|Acyl-transferase<br />
|A protein responsible for catalyzing the transfer of a palmitic acid moiety to the N-terminus of the hedgehog signalling molecule.<br />
|-<br />
|Ataxia<br />
|Lack of voluntary control and coordination of muscle movement often due to damage of the cerebellum, the region of the brain controlling muscle coordination<br />
|-<br />
|Bone morphogenetic protein (bmp)<br />
|Growth factors allowing for the signalling and subsequent structuring of organic tissue within a body.<br />
|-<br />
|Bradycardia<br />
|Disruption of normal electric impulses controlling the pumping of the heart resulting in a slower heart rate<br />
|-<br />
|Brother of ihog (Boi)<br />
|A surface protein that enhances hedgehog signal transduction through PTC in ''Drosophila''.<br />
|-<br />
|Carcinoma<br />
|A malignant tumour of epithelial tissue of skin or tissues lining body organs<br />
|-<br />
|Casein kinase I (CKI)<br />
|A kinase that is thought to phosphorylate the Smoothened receptor to activate it in the hedgehog signalling pathway.<br />
|-<br />
|Cleft Palate<br />
|An opening or split in the roof of the mouth as a result of the palatal shelves not fusing, most often occurring in embryonic development. <br />
|-<br />
|Convulsion<br />
|Sudden, rapid, involuntary contraction of body muscles repeatedly <br />
|-<br />
|Cubitus interruptus (Ci)<br />
|A transcription factor found in the hedgehog signalling pathway of ''Drosophila'', which binds to promoter regions on the DNA in the nucleus to activate target genes of the pathway.<br />
|-<br />
|Costal-2 (Cos2)<br />
|A kinesin like protein which interacts with the C terminus of Smoothened and acts like a scaffolding protein and allows proteins such as Fused to bind to it.<br />
|-<br />
|Denticle<br />
|Bristle like projections off the segments on the ''Drosophila'' embryo.<br />
|-<br />
|Dally<br />
|An HSPG, which mediates loacalizaiton and transportation of the hedgehog protein to its targets in ''Drosophila''<br />
|-<br />
|Desert hedgehog (Dhh)<br />
|A homolog of the ''Drosophila'' hedgehog protein, which is expressed most prominently in the gonads of vertebrates, where it plays a possible role in regulating spermatogenesis. <br />
|-<br />
|Desmoplastic<br />
|A reaction involving growth of dense fibrous tissue around the tumour<br />
|-<br />
|Endochrondral Ossification<br />
|A process by which bone is created within vertebrae.<br />
|-<br />
|Epilepsy<br />
|A neurological disorder whereby nerve cell activity in the brain becomes abnormal resulting in convulsions, or loss of consciousness<br />
|-<br />
|Frizzled<br />
|A receptor that is part of the Wnt signalling pathway, which binds the protein wingless in order to activate signalling cascades. <br />
|-<br />
|Frontal bossing<br />
|A pronounced forehead<br />
|-<br />
|Fused (Fu)<br />
|A kinase that binds to Costal-2 and acts to inhbit Suppressor of Fused by phosphorylating it in the hedgehog signalling pathway.<br />
|-<br />
|Gli<br />
|A family of proteins that acts as transcription factors that were originally isolated in human gliboblastoma. The proteins are important mediators in activating target genes for the hedgehog signalling pathway in vertebrates.<br />
|-<br />
|Glycipan (GPC)<br />
|A family of HSPGs which act in the hedgehog signalling pathway of vertebrates to either enhance or inhibit signal transduction depending on the isoform.<br />
|-<br />
|Hedgehog (Hh) protein<br />
|A signalling protein widely expressed in the tissue during embryonic development of vertebrates and some other species such as ''Drosophila'', and acts to pattern and develop tissue. The protein is the primary mediator of the pathway.<br />
|-<br />
|Heparin sulfate proteoglycan (HSPG)<br />
|A proteoglycan ,which is a heavily glycosolated protein, which in the context of hedgehog signalling is thought to aid in the localization and transport of hedgehog proteins to their targets.<br />
|-<br />
|Heterozygousity<br />
|Having different alleles of one gene<br />
|-<br />
|Hypoplasia<br />
|Arrested, incomplete development of an organ or tissue<br />
|- <br />
|Indian hedgehog (Ihh)<br />
|A signalling protein that is a homolog of the ''Drosophila'' hedgehog protein, that primarily acts in regions where there is endochondrial ossification to aid in the maturation of chondrocytes.<br />
|-<br />
|Interference hedgehog (Ihog)<br />
|A surface protein that enhances hedgehog signal transduction through PTC in ''Drosophila''.<br />
|-<br />
|Kif7<br />
|A homolog of Costal-2 in vertebrates, which acts to regulate the downstream signalling of the hedgehog pathway by causing the disassociation of SUFU and Gli.<br />
|-<br />
|Limb bud<br />
|A structure formed during early embryonic development consisting of ectoderm and mesenchyme representing the early limbs, where signalling processes in the bud will eventually lead to the out growth and patterning of the bud.<br />
|-<br />
|Macrocephaly<br />
|Abnormal enlargement of the head due to an enlarged brain or excessive accumulation of cerebrospinal fluid<br />
|-<br />
|Organogenesis<br />
|The process of the development of the ectoderm, endoderm and mesoderm into the organs of an organism.<br />
|-<br />
|Patched (PTC)<br />
|Patched is a transmembrane receptor expressed on cells that are sensitive to signalling via the hedgehog pathway, where its extracellular domain binds to the hedgehog protein to inactivate it. The receptor it self without hedgehog binding actively inhibits Smoothened. <br />
|-<br />
|Primary cilia<br />
|An organelle that consists of an outward projection from the cell surface, which is thought to be critical for hedgehog signalling in vertebrates as it houses many components of the pathway. <br />
|-<br />
|Protein kinase A (PKA)<br />
|A kinase that is thought to phosphorylate the Smoothened receptor to activate it in hedgehog signalling.<br />
|-<br />
|Smoothened (SMO)<br />
|A G-protein coupled receptor like receptor integral to the hedgehog signalling pathway and acts to set in motion a series of events that lead to the activation of transcriptional factors that activate target genes of the hedgehog pathway.<br />
|-<br />
|Sonic hedgehog (Shh)<br />
|The most widely expressed homolog of the ''Drosophila'' hedgehog protein found in vertebrates, playing a key role in embryonic development of humans.<br />
|-<br />
|Strabismus<br />
|Abnormal alignment of the eyes with eachother resulting in a cross-eyed appearance<br />
|-<br />
|Suppressor of Fused (SUFU)<br />
|A protein in the hedgehog signalling pathway which when active, inhibits the translocation of Cubitus interruptus into the nucleus by leading to its phosphorylation, and eventually degradation via the proteosome.<br />
|-<br />
|Wingless protein<br />
|A protein produced as a downstream target of the hedgehog signalling pathway in ''Drosophila'', which activates the Wnt pathway by binding to the Frizzled receptor.<br />
|-<br />
|Zone of polarizing activity (ZPA)<br />
|The posterior region of the limb bud mesenchyme, which aids in the signalling of it to pattern the posterior anterior axis with respect to the digits through mediators such as sonic hedgehog.<br />
|-<br />
|}<br />
<br />
===Additional Glossary Links===<br />
[[A|A]] | [[B|B]] | [[C|C]] | [[D|D]] | [[E|E]] | [[F|F]] | [[G|G]] | [[H|H]] | [[I|I]] | [[J|J]] | [[K|K]] | [[L|L]] | [[M|M]] | [[N|N]] | [[O|O]] | [[P|P]] | [[Q|Q]] | [[R|R]] | [[S|S]] | [[T|T]] | [[U|U]] | [[V|V]] | [[W|W]] | [[X|X]] | [[Y|Y]] | [[Z|Z]] | [[Numbers|#]]<br />
<br />
== References ==</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=2016_Group_Project_4&diff=255226
2016 Group Project 4
2016-10-27T11:21:59Z
<p>Z5018221: /* Glossary */</p>
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<br />
= Hedgehog signalling pathway =<br />
==Introduction==<br />
[[File:Hedgehog.jpg|thumb|300px|An image of a hedgehog, the animal of which the Hh proteins are named after.]]<br />
The Hedgehog (Hh) signalling pathway is an important part of the early embryo with regards to the patterning and development of the nervous system, limbs and the cranio-facial region in vertebrates and the polarization of the segments in the ''Drosophila'' embryo. It was first identified in 1980 by Christiane Nüsslein-Volhard and Eric Wieschaus, alongside a group of other genes regulating segment polarity in ''Drosophila'' embryonic development<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. The pathway itself consists of Hh proteins, where there are three identified homologs in vertebrates, being sonic hedgehog (SHH), Indian hedgehog (IHH), and desert hedgehog (DHH) <ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. All homologs are expressed at varying levels within different tissues in the body, and also act as a form of redundancy to an extent between one another. <br />
<br />
The signaling pathway is highly conserved between various species<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. and acts via a G protein coupled receptor like receptor, which uninhibited via the action of the Hh proteins. The pathway overall acts via a balance of dephosphorylation<ref name="PMID10966113"><pubmed>10966113</pubmed></ref> and degradation of proteins<ref name="PMID15102702"><pubmed>15102702</pubmed></ref> in order to regulate transcription factor activity to express various genes to carry out its action. The Hh pathway is also highly implicated when it comes to abnormalities in development, as it is implicated in diseases such as holoprosencephaly and cleft lip and palate. Overall Hh signaling pathways play a large role in embryological development, which will be discussed in detail on this page.<br />
<br />
== History ==<br />
{| class="pretty table"<br />
| '''1980'''<br />
|Christiane Nüsslein-Volhard and Eric Wieschaus first identified a group of genes including those related to the Hedgehog signalling pathway and linked them to the segmentation and planning of the embryo in ''Drosophila melanogaster'' by introducing mutagenic substances to the developing embryo<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Multiple researchers including Andrew P. McMahon and Clifford Tabin discovered three equivalent homologs in vertebrates of the ''Drosophila melanogaster'' hedgehog gene, known as sonic hedgehog (Shh), desert hedgehog (Dhh) and indian hedgehog (Ihh), by looking at DNA sequences similar to that of the gene in the fruit fly<ref><pubmed>7916661</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Clifford Tabin and his lab identified the role of Shh in localising the limb bud, where they identified protein to be expressed within a region of the limb bud known as the zone of polarising activity (ZPA), showing that SHH is sufficient to induce the production of a ZPA, and thus limb bud formation in chick embryos<ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|Sonic hedgehog secreted by the notochord was identified to induce ventral cell types in the neural tube during embryonic development, most notably the floor plate cells and the motor neurons as shown in chick embryos. Such differentiation between the two cell types is thought to be a matter of sonic hedgehog concentrations experienced by the neural plate cells<ref name="PMID7736596"><pubmed>7736596</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|A shared Nobel prize in physiology or medicine was awarded to Christiane Nüsslein-Volhard and Eric Wieschaus for their researching regarding the identification of the developmental genes relating to the formation and patterning of the early embryo via genes.<br />
|-<br />
|'''1996'''<br />
|Studies showed that human homologs of the Patched gene, a component of the hedgehog pathway, is a key gene that is mutated in Gorlin Syndrome, which characterised by a predisposition for basal cell carcinomas, the most common cancers in humans and developmental abnormalities<ref name="PMID8658145"><pubmed>8658145 </pubmed></ref>.<br />
|-<br />
|'''1999'''<br />
|Researchers implicated Indian hedgehog as a key signalling molecule for the maturation and differentiation of prehypertrophic chondrocytes, where Indian hedgehog null mice were shown to have a lack of mature chondrocytes and no development of osteoblast cells in endochondrial bone. This was thought to be due to Indian hedgehog having a feedback signal controlling parathyroid hormone related protein, which regulates endochondrial bone development<ref name="PMID10465785"><pubmed>10465785</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Sonic hedgehog was identified to regulate the proliferation of adult neural stem cells as shown in the hippocampus of rats and in vitro for neural progenitor cells isolated from the hippocampus<ref name="PMID12469128"><pubmed>12469128</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Studies on Shh function found that it can act as a chemoattractant in the developing embryo spinal cord, to help guide commissural axons to the midline of the floor plate<ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
|-<br />
|'''2009'''<br />
|Mouse models showed that reduction in hedgehog signalling allows for transient improved response to chemotherapy with regards to mouse models of human pancreatic ductal adenocarcinoma, a cancer with one of the highest mortality rates in humans<ref name="PMID19460966"><pubmed>19460966</pubmed></ref>.<br />
|}<br />
<br />
This time line regarding the discoveries in the hedgehog signalling pathway is by no means exhaustive, but a selection of relatively large discoveries that had a significant impact in the field on the basis of citations.<br />
<br />
== Origin of name ==<br />
<br />
[[File:Bands of denticles in normal and Hh mutant Drosophila embryo.jpeg|thumb|250px|Differences in patterning of the denticle bands in normal and mutated hedgehog gene variant ''Drosophilia'' embryo]]<br />
<br />
The name hedgehog came about when Christiane Nüsslein-Volhard and Eric Wieschaus first identified the group of genes controlling polarization of the segments in the ''Drosophila'' early embryo. They noticed that when they mutated the Hh gene, making it non-functional, that the bands of denticles formed during the early ''Drosophila'' embryo formation became more diffuse as opposed to being distinct normally. The denticles would all clump together forming a single patch on the surface of the embryo, as opposed to normally outlining the distinct segments of the embryo as bands<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. This gave the embryo spiny and prickly look similar to that of the back of a hedgehog.<br />
<br />
From there on in the gene was called the hedgehog gene where homologs in vertebrates discovered along the line kept to this naming structure giving various species of hedgehog names to the genes such as Indian hedgehog, and desert hedgehog, with the exception being sonic hedgehog, which is named after a fictional character in the video game “Sonic the Hedgehog”.<br />
<br />
== Mechanism of signalling ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br>[[File:Hh signalling pathway.jpg|thumb|600px|Diagrammatic representation of the steps and components involved in the hedgehog signalling pathway in both ''Drosophila'' and mammals.]]<br />
<br />
The Hh signaling pathway has been well studied in ''Drosophila melanogaster'', and has been shown the be conserved to an extent across it and mammals making the species a suitable model for Hh signalling in humans<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. In ''Drosophila melanogaster'', the Hh pathway begins when the Hh proteins bind to the extracellular domain of the transmembrane protein known as Patched (PTC). Such binding is thought to be greatly enhanced by the presence of proteins known as interference hedgehog (ihog) and brother of ihog (boi), which have shown to be essential to allowing hedgehog binding to inactivate PTC<ref name="p20048000 "><pubmed>20048000 </pubmed></ref>. It has also been demonstrated heparin sulfate proteoglycans (HSPG) such as dally also aid in the modulation of hedgehog signalling, where they act to localise and transport the hedgehog protein to the target receptors<ref name="p14602684"><pubmed>14602684</pubmed></ref> <ref name="p10549295"><pubmed>10549295</pubmed></ref>. Overall hedgehog binding leads to inactivation of PTC which occurs by Hh trapping PTC in an inactive conformational state<ref><pubmed>27647915</pubmed></ref>. After binding of Hh occurs to PTC and it is inactivated, the receptor and Hh protein is thought to be endocytosed by the cell where they undergo lysosomal degradation in order to limit Hh concentration, thus limiting its spread to other cells and PTC activity<ref name="PMID15102702"><pubmed>15102702</pubmed></ref>. In the absence of Hh, PTC acts to suppress the expression of the Smoothened (SMO), a G-protein coupled receptor like receptor, and thus its signaling. How PTC achieves this inhibition of SMO is currently unclear. Studies have suggested that due to the highly phosphorylated nature of SMO when active, that PTC acts to dephosphorylate SMO in order to repress its signaling. It is thus that binding of Hh to PTC reduces PTCs ability to promote dephosphorylation of SMO, leading to its increased activity and expression on the cell surface <ref name="PMID10966113"><pubmed>10966113</pubmed></ref>. It is thought that the phosphorylation required to activate SMO are dependent on protein kinase A (PKA) and casein kinase I (CKI) <ref><pubmed>15616566 </pubmed></ref>.<br />
<br />
This overall increased phosphorylation of SMO due to a repression of PTC activity by Hh leads to an accumulation of SMO on the cell surface, which collectively allows for SMO to exert its activity. Importantly the phosphorylation also disrupts intramolecular electrostatic interactions between SMO molecules which switches the molecule into its active conformational state <ref><pubmed>17960137 </pubmed></ref>. Generally, SMO has been shown to have very little signal transducing ability, and thus this accumulation allows it to jointly transduce a substantial signal. This occurs by the C terminus of SMO on the intracellular domain interacting with the kinesin like protein Costal-2 (Cos2), which is thought to bind to microtubules in order to acts as a scaffolding protein <ref><pubmed>18691888 </pubmed></ref>. Such interactions induce the formation of a complex including the kinase known as Fused (Fu) and Cos2, which phosphorylates Suppressor of Fused (SUFU) to inhibit it. Without this inhibition SUFU goes onto prevent the translocation of the transcriptional factor Cubitus interruptus (Ci) into the nucleus by leading to its phosphorylation, and subsequently its partial cleavage via the proteosome. The partial cleavage of Ci leaves a lower molecular weight protein known as Ci repressor (CiR) or Ci75, which translocates into the nucleus and acts to repress the target genes of the Hh signalling pathway via Ci<ref><pubmed>9215627</pubmed></ref>. Thus overall inhibition of SUFU increases the amount of Ci entering into the nucleus of the cell, and activating transcription of target genes of the Hh pathway<ref><pubmed>10952898 </pubmed></ref>. Activation of SMO also promotes disassociation of present SUFU-Fu-Cos2-Ci complex which which generally when fully intact leads to cleavage of Ci into its repressor form<ref name="p15063184"><pubmed>15063184</pubmed></ref><ref name="p17881487"><pubmed>17881487</pubmed></ref>.<br />
<br />
At this point Ci is able to activate the transcription of various genes, which include importantly the ''ptc'' gene, which encodes the PTC receptor. It is thus as a result of this, that PTC expression will be increased in response to Hh pathway induction, which negatively feeds back to reduce Ci signaling induction, in order to maintain homeostasis and regulate the intensity and duration of the signaling from Hh<ref><pubmed>9053330</pubmed></ref>. Furthermore the ''wg'' gene, encoding the wingless protein is also activated by Ci, which leads to activation of the Wnt pathway via the Frizzled receptor in adjacent cells expressing the gene ''engrailed'' <ref><pubmed>9502727</pubmed></ref> <ref><pubmed>10457026</pubmed></ref>. This overall stabalizes the boundaries between the segments of the developing ''Drosophila melanogaster'' signalled by the gene ''engrailed''<ref><pubmed>3282172</pubmed></ref>.<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=w1xXD9kss2w</html5media><br />
<br><br><br />
An overview of the hedgehog signalling pathway in ''Drosophila''<ref>YouTube. (2016). The Hedgehog signalling pathway in Drosophila online Available at: https://www.youtube.com/watch?v=w1xXD9kss2w</ref>.<br />
<br />
=== Mammals ===<br />
<br />
Although the Hh signaling pathway has been conserved across species to an extent <ref name="PMID8595881"><pubmed>8595881</pubmed></ref>, key differences exist when observing the pathway within mammalian tissue in contrast to that which has been studied in ''Drosophila melanogaster''. In mammalian cells and all other vertebrates, Hh signalling is dependent on an organelle known as the primary cilia, which are projections outwards from the cells surface. The importance of such an organelle in the signalling pathway comes as a result of PTC1, one of the two PTC receptor homologs in mammals, that binds to the Hh homolog Sonic Hh (Shh), exists within the cilia<ref><pubmed>17641202</pubmed></ref>. Similarities also exist between signalling in the vertebrates and ''Drosophila''. This includes the surface proteins such as Cdo and Brother of cdo (Boc), which act in a similar fashion to ihog and boi in enhancing the binding of the hedgehog protein to PTC<ref><pubmed>16647304</pubmed></ref>. HSPGs such as gylcipans (GPC) 1, 2, 3, 4, 5 and 6 are also thought to play a role in hedgehog signalling in vertebrates with regards to stimulaiton or inhibition of the pathway depending on the isoform<ref><pubmed>26627558</pubmed></ref>. The mechanism of action of SMO inhibition and activation is poorly understood currently, but evidence has suggested that PTC1 acts to inhibit SMO when unbound to Shh by acting as a pump to remove oxysterols from the cilia into the extracellular space<ref><pubmed>PMC1462959</pubmed></ref>. These oxysterols are normally thought to bind and accumulate around the SMO receptors, which in turn prevents internalization and deactivation of SMO, leading to it accumulating on the apical primary cilia<ref><pubmed>16136078</pubmed></ref>. Other studies have also suggested that Shh has a role in increasing phosphorylation of SMO via kinases such as CK1, which causes it to accumulate on the cilia<ref><pubmed>21695114</pubmed></ref>. Overall the net action of Shh initially is believed to cause accumulation of SMO at the cilia by inhibiting PTCH1 and phosphorylation of SMO.<br />
<br />
How SMO acts next is relatively unknown but, it has been shown to promote the disassociation between SUFU and Gli transcription factor, which allows Gli to be transported to the nucleus to activate effector genes of the pathway. Gli is normally bound in the cytoplasm to SUFU, where SUFU promotes the partial degradation of Gli into its repressor form, similar to that in the fruit fly model<ref><pubmed>20360384</pubmed></ref>. Alongside this, Kif7, a Cos2 homolog, has been shown to migrate to the apex of the cilium in response to SMO accumulation at the cilium, where it has been postulated to also promote disassociation of SUFU and Gli<ref><pubmed>19592253</pubmed></ref>. On the other hand, Kif7 is also thought to play an inhibitory role for the signalling pathway as when it is localized at the base of the cilia in the absence of Hh signaling, where it acts to traffic Gli transcription factors away from the cilia<ref><pubmed>19666503</pubmed></ref>. This all leads to an accumulation of active Gli transcription factors which migrate to the nucleus in order either inhibit or activate gene transcription in response to Hh signaling. These Gli transcription factors include Gli1, Gli2, and Gli3, where Gli2 and Gli3 in their activated form are the primary mediators of the pathway, and also act to repress the target genes when hedgehog signalling is absent. Gli3 is considered to be the major repressor of the pathway when the full length version of the Gli3 protein is partially cleaved into its repressor form <ref><pubmed>10433919</pubmed></ref>. Gli1 on the other hand is one of the targets of hedgehog signalling promoted by Gli2 and Gli3 activators, and acts to reinforce the hedgehog pathway through a positive feedback loop <ref><pubmed>10075717</pubmed></ref>. As a result Gl1 is considered as not entirely essential ,where mice models with no production of Gl1 have shown viability with few defects<ref><pubmed>10725236</pubmed></ref>. That being said, other studies have shown the importance of Gl1 as a downstream target of sonic hedgehog, where it is thought to induce ventral neural tube development, as it is on the only Gli factor present in the floor plate during gastrulation<ref><pubmed>9216996</pubmed></ref>. Overall the interactions between such transcription factors are still relatively unknown, where further research is required to elaborate on the specific roles in the hedgehog pathway they each have.<br />
<br />
== Function ==<br />
===Overview===<br />
{| class="pretty table"<br />
|'''Hedgehog protein homolog'''<br />
|'''Function'''<br />
|-<br />
| Sonic hedgehog [http://www.omim.org/entry/600725 OMIM entry] ||<br />
*Expressed in zone of polarizing activity of the limb bud where it plays a role in helping to pattern the anterior and posterior aspect of the limbs <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
*Based on time and concentration of SHH due to diffusion from the point of secretion in the limb bud, SHH also plays a role in determining digit identity <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>.<br />
*Acts as a chemoattractant to guide commissural axons in the floor plate of the neural tube towards the midline <ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
*Patterns the developing cusps of the teeth and their relative positions in the jaw, and is also essential for the growth of the teeth <ref name="PMID11044393"><pubmed>11044393</pubmed></ref>.<br />
*SHH released from the notochord acts to induce formation of the floor plate, motor neurons, and dopaminergic neurons, as well as signalling the induction of the ventral cell types in the neural tube <ref name="PMID8790332"><pubmed>8790332</pubmed></ref>.<br />
|-<br />
| Desert hedgehog [http://www.omim.org/entry/605423 OMIM entry]||<br />
*Plays a possible role in regulating spermatogenesis as due to the highly localised expression in the testes by pre-Sertoli cells, and the fact that mice with no DHH present are infertile, with no mature spermatozoa <ref name="PMID8805249"><pubmed>8805249</pubmed></ref>. <br />
*DHH derived from Schwann cells signal development of peripheral nerves, by inducing the production of a connective tissue sheath around them <ref name="PMID10482238"><pubmed>10482238</pubmed></ref>.<br />
|-<br />
| Indian hedgehog [http://www.omim.org/entry/600726 OMIM entry]||<br />
*Aid in the signalling of proliferating chondrocytes to undergo hypertrophic differentiation during endochondral ossification<ref name="PMID8662546"><pubmed> 8662546</pubmed></ref>.<br />
*Plays a key role in yolk sac angiogenesis, as seen in studies where an absence of IHH leads to death of the embryo due to poor yolk sac vasculature <ref name="PMID11807029"><pubmed>11807029</pubmed></ref>.<br />
|}<br />
<br />
===Limb development===<br />
<br />
====Research background====<br />
<br />
The hedgehog signalling pathway plays a significant role with regards to the embryonic development of the limbs in vertebrates, specifically SHH. For a while the mechanism of which the limb was patterned on the anterior to posterior axis was quite unknown. Early studies had shown that grafting posterior wing bud cells to the anterior region of the wing bud in a chick embryo, an equal amount of extra digits was produced to that of which was normally produced, and in a mirror image pattern<ref name="PMID4390734"><pubmed>4390734</pubmed></ref>. This showed that the pattern of which the digits were produced were polarized with respect to that of the graft from the limb bud, which has become to be described as the zone of polarizing activity (ZPA). Further studies mapped the ZPA, by showing the area of the wing bud on the chick with the highest polarizing activity to be the posterior margin of the wing bud<ref name="PMID4719010"><pubmed>4719010</pubmed></ref>. Furthermore, studies later on found that the amount or concentration of ZPA cells grafted played a role in the amount of digits induced and how polarized they were<ref name="PMID7453825"><pubmed>7453825</pubmed></ref>. This ultimately gave rise to studies regarding a potential morphogen, which could potentially provide this concentration dependent activity of polarization when it comes to the limb bud. Studies to find this morphogen led to the discover of the ability for retinoic acid to mimic the polarizing action of the ZPA when applied locally to the limb bud<ref name="PMID7070499"><pubmed>7070499</pubmed></ref>. This was found to be due to the induction of a second morphogen known as SHH, where when cells that express SHH are grafted onto the limb bud, polarized digit development is induced<ref name="PMID7720566"><pubmed>7720566</pubmed></ref>.<br />
<br />
====Polarizing activity of sonic hedgehog====<br />
[[File: Mechanims of patterning the digits on the posterior to anterior axis of the limb bud by sonic hedgehog.jpg|thumb|450px|Regions of the limb bud and the digits they form based on patterning of the posterior to anterior axis of the limb bud by mechanisms mediated by sonic hedgehog.]]<br />
More recent studies have sought to elucidate how SHH mediates such a polarizing effect in terms of digit identification and its underlying mechanism. It has been suggested that such an effect is heavily concentration dependent similar to that of when transplanting the chick wing bud ZPA cells, acting in a dose dependent matter, due to the ability of SHH to modulate signaling at long ranges via diffusion<ref name="PMID11389830"><pubmed>11389830</pubmed></ref>. This implies that a gradient of varying concentrations of SHH diffused through the mesenchyme of the limb bud leads to the identification of posterior and anterior digits.<br />
<br />
Current research has also suggested that not only is the concentration gradient of SHH important for the patterning of the digits, but also the temporal gradient, being the length of time of exposure of SHH to the mesenchyme of the limb bud. Studies have shown in mice that of the 5 digits, polarization from the posterior end, being digit 5, to the anterior end being digit 1 are due to different mechanisms. Digits 5 and 4 have been shown to be comprised of the SHH expressing cells and thus both experience maximal levels of SHH, and thus cannot be distinguished on the basis of a concentration gradient. As a result, temporal gradients are employed, where the expression of SHH in both regions that become the digits vary, where studies have shown that SHH expression in the primordium of digit 5 is maintained longer than that in digit 4 gradient <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>. When it comes to digit 3 and 2, there is differentiation based on the concentration gradient of SHH from the ZPA, where due to the ZPA being further away to digit 2 than 3, the concentration of SHH will be higher at 3<ref name="PMID15315763"><pubmed>15315763</pubmed></ref> <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>. In terms of digit 1, the levels of SHH are so low at this point that it is said to be SHH independent, and actually reliant on the absence of SHH for normal differentiation. With regards to how SHH actually mediates its action, it is thought to be by a balance between the transcription factor Gli3 and SHH expression, which activates Gli1, Gli2 and Gli3 repressor, effectively counteracting Gli3. Gli3 is considered to promote the inhibition of digit formation and identification, while the downstream targets of SHH are thought to promote it<ref name="PMID17400206"><pubmed>17400206</pubmed></ref>.<br />
<br />
Other research has also shown the possibility of SHH signaling as a way to prime the posterior mesenchyme and induce the production of bone morphogenetic protein 2 (bmp2), which is thought to be the morphogen creating the chemical gradient for digit identification<ref name="PMID10704381"><pubmed>10704381</pubmed></ref>. Overall the mechanism at which SHH work to pattern the posterior anterior axis of the limb bud is still relatively unknown, and further research is being conducted to elucidate how the underlying mechanisms such as the downstream targets of SHH affect digit formation.<br />
<br />
=== Neural development ===<br />
<br />
====Research background====<br />
Research on the role of the notochord, a cartilaginous structure derived from the mesoderm, initially observed its ability to induce the floor plate within the neural tube of chick embryos<ref name="PMID3354847"><pubmed>3354847</pubmed></ref>. This induction of a floor plate occurred in the ventral midline of the neural tube, where the floor plate itself is thought to have signalling effects regarding patterning of the spinal cord. Alongside this, research also noted that the floor plate and notochord collectively had signalling effects that patterned the differentiation of the neural cells in the neural tube<ref name="PMID1991324"><pubmed>1991324</pubmed></ref>. Such observations lead to research being directed at how this patterning of the neural tube is mediated through the notochord. It had been suggested that the morphogen known as Shh was to play due to its high expression within the notochord and floor plate. It also was showed to activate floor plate expressed genes when ectopically expressed in the mouse CNS<ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. Furthermore, observations regarding the Shh also lead to implicating it in the differentiation of distinct cell types in the ventral neural tube such as motor neurons, alongside the already identified floor plate<ref name="PMID8124714"><pubmed>8124714</pubmed></ref>. Studies looking specifically at the targets of Shh signalling in the neural tube also identified that using antibodies to block the protein would lead to blocking of the induction of the motor neurons, and that applying Shh to explants induced floor plate and motor neurons in a variety of vertebrate models<ref name="PMID7753196 "><pubmed>7753196 </pubmed></ref>. This for the most part formed the basis of research on the specific patterning effects of Shh secreted from the notochord and floor plate on the ventral neural tube.<br />
<br />
====Patterning of ventral nerve cell types in the neural tube====<br />
As stated, the inductive signals from the notochord in the form of Shh <ref name="PMID7753196"><pubmed>7753196 </pubmed></ref> are primarily responsible for the formation of the floor plate in the ventral midline of the neural tube during embryonic development<ref name="PMID3354847"><pubmed>3354847</pubmed></ref>. The floor plate itself acts in the same fashion as the notochord with regards to expression of Shh for mediatating its signal. Collectively it is thought that the notochord and the floor plate provide a Shh graded response, where there is a gradient of concentrations along the dorsoventral axis of the developing neural tube<ref name="PMID9598380"><pubmed>9598380</pubmed></ref>. As a result, it is believed that the degree of Hh signalling on a cell type is responsible for the differentiation of progenitor cells it to various types. Specifically, with regards to the floor plate, the distinct local signal, given the close proximity of the notochord to the floor plate induction site is responsible for inducing the floor plate<ref name="PMID9598380"><pubmed>9598380</pubmed></ref>. It is thought that through interacting with the receptor PTC, the pathway activates the transcription of hepatocyte nuclear factor 3β (HNF-3β), a gene that has been shown to be commonly expressed in the floor plate. Such a gene is activated by the transcription factors Gli1 and Gli2. Thus HNF-3β is considered to be the downstream target of Shh signalling leading to the induction of the floor plate<ref name="PMID9118802"><pubmed>9118802</pubmed></ref>. It is also believed that HNF-3β is essential for notochord formation as well, as seen in mice models with HNF-3β knocked out, leading to dorsoventral patterning issues<ref name="PMID8069909"><pubmed>8069909</pubmed></ref>. Overall the induced floor plate acts to further aid the notochord in producing a graded Shh response to pattern the ventral neural tube<ref name="PMID1991324"><pubmed>1991324</pubmed></ref>.<br />
<br />
=== Organogenesis ===<br />
The Hedgehog Signalling pathway is a pathway sending information to embryonic cells which plays an especially important role in the regulation of organogenesis. These processes include the organization of the brain (craniofacial) and the growth of appendages with further studies implicating the Hedgehog Signalling pathway in the development of the small intestine, lungs and the pancreas.<br />
<br />
== Animal models ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br>[[File:Hedgehog signalling on plane polarity of denticles in Drosophila.png|thumb|400px|Image of denticles on the ''drosophila'' embryo used as a model to research plane polarization of cells by looking at the orientation of the denticles on the ''drosophila'' embryo in response to many signalling molecules including hedgehog.]]<br />
<br />
Hedgehog (Hh) protein signal was initially discovered through experimentation on the fruit fly, "Drosophila melanogaster". It is through this model that we are able to discover not only the functional components of this pathway but also understand its role in embryonic development. Through application of this information on the human biological system we are able to find the cause and thus potential treatments of defects and diseases caused by interruption or mutation of the Hedgehog signalling pathway. <br />
<br />
Upon further research on Drosophila it was found that Hh may play a role in germ cell proliferation and in particular, may control the proliferation and activity of somatic cells found within the germarium, which is the most anterior structure within the Drosophila ovary. <ref>Ovaries (Drosophila) definition. (2016). Groups.molbiosci.northwestern.edu. Retrieved 10 September 2016, from http://groups.molbiosci.northwestern.edu/holmgren/Glossary/Definitions/Def-D/Drosophila_Ovaries.html</ref> Thus, the Hh signalling pathway is vital in egg chamber formation and its consequent envelopment, budding and polarisation. It has also been observed that somatic cell proliferation is dependent on this pathway and thus, the number of pre-follicle cells is subject to the effect of the Hh signalling pathway. <ref><pubmed>8620839</pubmed></ref> Further studies have also indicated the role played by this pathway in activating the Epidermal growth factor receptor (EGFR) signalling pathway as seen in the induction of EGFR by Hh in Drosophila head development. <ref><pubmed>10331974</pubmed></ref> In addition, research on Drosophila has indicated the direct effect of Hh signalling on tracheal branch patterning. <ref><pubmed>11290298</pubmed></ref><br />
<br />
Despite ongoing research on "Drosophila melanogaster" to uncover the workings of the Hedgehog signalling pathway, further research is needed to confirm and further current findings. In addition, it is evident that it is through the study of these fruit flies that we are able to gain a basis of understanding of the causes of certain human diseases and thus propel research into treatments for sufferers.<br />
<br />
===Blockage of Shh Signalling in Forebrain Neuroectoderm of Chick Embryos===<br />
<br />
The Hedgehog signalling pathway plays a significant role in embryonic development, particularly of the forebrain. Due to its role in development of craniofacial features by contributing to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm, a disruption in this pathway can result in a variety of birth deformities including holoprosencephaly (HPE), where the prosencephalon (forebrain) fails to divide into 2 separate hemispheres, telencephalon and diencephalon <ref>Holoprosencephaly - NORD (National Organization for Rare Disorders). (2016). NORD (National Organization for Rare Disorders). Retrieved 10 September 2016, from http://rarediseases.org/rare-diseases/holoprosencephaly/</ref>, as well as cleft lip and palate. The function of Sonic Hedgehog (Shh) and its signalling pathway on the formation of forebrain neuroectoderm was studied in chick embryos.<br />
<br />
It was found that the disruption of Shh signalling in the neural tube of chick embryos resulted in the lack of division of the forebrain into the diencephalon and telencephalon. This is in fact, as stated earlier, the fundamental cause of the rare condition, holoprosencephaly. It was discovered that the Shh signalling pathway in the diencephalon was responsible for gene expression in the telencephalon. <br />
<br />
In addition, through experimentation on chick embryos it was found that through Shh signalling the development of the forebrain regulates and controls facial morphogenesis, particularly of the upper and middle face. Therefore, interference with Shh signalling in the forebrain prevents this intrinsic communication, thus hindering Shh expression in facial ectoderm. This results in brain malformation accompanied by facial disfiguration as seen in patients suffering from HPE. Other malformations caused by blockage of Shh signalling in craniofacial development include, hypotelorism (decreased space between the orbits), growth restriction as well as cleft lip and palate as mentioned previously. <br />
<br />
A commonality discovered among all forms of Shh signalling disruption was two facial defects, “the loss of mediolateral expansion of the face and absence of proximodistal outgrowth of the frontonasal prominence”<ref><pubmed>15979605</pubmed></ref> (Ralph et al., 2005). Through reference to studies performed on chick and mice embryos, it was found that Shh signalling is particularly vital in development of maxillary and frontonasal components of the cranium.<br />
<br />
This breakthrough study on the inhibition of Shh signalling in chick embryos has significantly filled the gap in our understanding of the Sonic Hedgehog signalling pathway. It is evident that this pathway is crucial in the development of the forebrain and in turn regulates and controls the development of the facial skeleton. This is further proven through the observation that in the event of Shh signalling inhibition there is a development of craniofacial malformations.<br />
<br />
=== Shh knockout mice ===<br />
<br />
Extensive research on Shh knockout mice allowed discovery of the roles of Shh in embryonic development and patterning of the limb buds and sclerotomes, and maintenance of the notochord. <ref><pubmed>8837770</pubmed></ref> These mice expressed defects in the cephalic neural tube with the fusion of telencephalic and optic vesicles. Through this research it is evident that Shh is partially responsible for the subdivision of the eye field through forebrain optic stalk development, along with formation of the ventral midline. It is these forebrain abnormalities established in the absence of Shh that results in congenital malformations of holoprosencephaly, development of a single nasal chamber and other facial defects in humans. <br />
<br />
The absence of the vertebral column including, the intervertebral discs and vertebrae along with the medial regions of the ribs were observed within Shh knockout mice. This lack of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population (Chiang et al., 1996). In addition, though the role of Shh in patterning the anterior-posterior limb axis is evident through anterior limb bud cell death in the absence of Shh, it is also responsible for the development of proximal-distal limb segments, particularly in the patterning of structures at the level of or distal to the latent elbow and knee joints. <ref><pubmed>11476582</pubmed></ref> This was perceived after observing the incomplete formation of distal limb structures with abnormal anterior-posterior axis formation (Chiang et al., 2001). Thus, Shh knockout mice provide great insight into the functions of Shh in embryonic development and the abnormalities formed in the absence of this signalling protein. <br />
<br />
== Clinical Significance ==<br />
<br />
===Gorlin Syndrome===<br />
[[File:1 week year old newborn girl with cleft lip and palate.png|thumb|An image of a 1 week year old newborn girl with cleft lip and palate]]<br />
Gorlin syndrome, also known as nevoid basal cell carcinoma syndrome, is a heritable disease resulting from heterozygousity in Hh receptor, Patched (PTC). The PTC gene encodes a protein which binds sonic hedgehog (Shh) and it is this binding which inhibits the Hh signalling pathway. However mutation of PTC leads to activation of the pathway <ref><pubmed>9620294</pubmed></ref>. The syndrome is characteristic of skin cancer basal cell carcinoma and cerebellum cancer medulloblastoma. 1-2% of medulloblastomas and 0.5% of basal cell carcinomas are attributable to the disease. Patients present with craniofacial and brain abnormalities such as cleft palate, strabismus, macrocephaly, abnormal development of the corpus callosum and frontal bossing, with an overall overgrown appearance. Skeletal defects such as of the shoulder, ribs and vertebrae are often seen, as well immobile thumbs and polydactyly, which is a deformity of the hand or feet in which they have one or more extra fingers or toes. Apart from physical anomalies, patients have an increased risk of tumours throughout the body including cardiac, ovarian fibromas, ovarian dermoid cysts, meningiomas, and fibrosarcomas. Additionally with time, patients eventually undergo intracranial calcification and dyskeratotic pitting of the hands and feet whereby skin cells prematurely convert to keratin <ref><pubmed>8681379</pubmed></ref>.<br />
<br />
===Holoprosencephaly===<br />
<br>[[File:Semilobar holoprosencephaly.jpg|thumb|240px|MRI of fore brain depicting semilobar holoprosencephaly]]<br />
Holoprosencephaly (HPE) is a congenital disease caused by incomplete division of the prosencephalon (embryonic forebrain) into separate lobes of the cerebral hemispheres. The Shh gene has been identified as a HPE-causing gene however recent evidence has also investigated into the PTC gene, which acts to repress Shh signalling. A gain in repressive action of PTC is seen, leading to decreased Shh signalling, and thus HPE <ref><pubmed>11941477</pubmed></ref>. Clinical expression is variable between patients and is dependent upon the 3 forms of increasing severity: lobar, semi-lobar and alobar HPE, where patients can present with right and left ventricles however with a continuous frontal cortex in lobar HPE, to carrying a single cerebral ventricle in alobar HPE. Along with forebrain abnormalities, facial anomalies are also seen including midline cleft lip and/or flat nose, ocular hypotelorism characteristic of a small distance between the eyes. In severe rare cases of cyclopia, a non-functioning nose may be observed in the form of proboscis and the patient may present with a single eye at the root of the nose <ref><pubmed>20583177</pubmed></ref>. Furthermore, patients with HPE often develop a large number of medical issues including epilepsy, mental retardation, thyroid and adrenal hypoplasia due to lack of hypothalamus or pituitary gland development, and diabetes insipidus.<br />
<br />
===Medulloblastoma===<br />
Medulloblastoma is a cancerous tumour of the cerebellum where the cells of origin are the granular cell precursors found in the neonatal cerebellum, explaining its high prevalence in children <ref><pubmed>19171780</pubmed></ref>. Commonly, medulloblastomas are found deep in the cerebellum along the midline, however with desmoplastic medulloblastomas, they are found more laterally and superficial. As seen previously with Gorlin syndrome and holoprosencephaly, PTC is also associated with the development of medulloblastoma, and misregulation of Hh-PTC signalling in cells of the external germinal layer, the layer found on the surface of the cerebellum, is thought to give rise to the tumour. In experimental studies, it has been discovered that PTC is highly transcribed in medulloblastomas and in approximately 30% of PTC heterozygous mice the tumour develops <ref><pubmed>9205058</pubmed></ref> <ref><pubmed>9262482</pubmed></ref>. In patients with medulloblastoma, often children, the most common symptoms seen are vomiting, ataxia, psychomotor regression, drowsiness and anorexia. With age, patients are seen to get more frequent headaches, and show psychological symptoms such as behavioural problems, poor performance in school, and anxiety. In patients exhibiting life-threatening symptoms due to increased intracranial hypertension, bradycardia, convulsions and coma are often seen <ref><pubmed>21537925</pubmed></ref>.<br />
<br />
Watch below for a breakdown on Hedgehog's role in Tumour Development!<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=gFWO3I-oqsE</html5media><br />
<br><br><br />
An overview of the Hedgehog Signalling Pathway in Tumour Development<ref>YouTube. (2016). The Hedgehog Signaling in the Tumor Microenvironment - Research Hedgehog online Available at: https://www.youtube.com/watch?v=gFWO3I-oqsE</ref>.<br />
<br />
<br />
<br />
== Current research ==<br />
<br />
==Quiz==<br />
<br />
<quiz display=simple><br />
<br />
{Which of the following are the reasons that are thought to allow for the patterning of digits in vertebrates.<br />
|type="[]"}<br />
+ &nbsp;Concentration gradient of sonic hedgehog.<br />
+ &nbsp;Temporal gradient of sonic hedgehog.<br />
- &nbsp;The varying homologs of the hedgehog proteins .<br />
- &nbsp;The length of the hedgehog molecule.<br />
+ &nbsp;No sonic hedgehog signalling.<br />
- &nbsp;The type of cholesterol attached to the hedgehog molecule.<br />
||<br> For differentiation of the individual digits in mice to occur it is thought that each digit requires a different signalling mechanism. Digits 5 and 4 which are most posterior, are derived from the region around the zone of polarising area which contain Shh secreting cells, meaning these regions will experience a saturation of Shh signalling and cannot be differentiated by Shh concentration. As a result it is thought that these digits are identfied based on the temporal gradient, meaning that the length of which Shh is expressed in these regions differentiates the digits from one another with digit 5 expressing Shh for longer. Digits 3 and 2 are further away but still receive Shh signalling due to the diffusible nature of Shh from the ZPA, which forms a concentration gradient. This means the the concentration at digit 2 will be less than digit 3 due to being further away from the ZPA and thus can be differentiated from one another based on this concentration. Finally the digit 1 is differentiated on the basis of not receiving any Shh signalling at all. Thus it is a combination of concentration gradient of Shh, temporal gradient of Shh, and independence from Shh.<br />
<br />
{Which of the following are correct with regards to the hedgehog signalling pathway in ''Drosophila''.<br />
|type="[]"}<br />
-&nbsp;It occurs at the cillum on the cell surface.<br />
-&nbsp;Hedgehog protein binding to the Patched receptor activates it to inhibit Smoothened.<br />
+&nbsp;Hedgehog protein binding to the Patched recetpor inhibits it to activate Smoothened. <br />
+&nbsp;Inhibition of SUFU is critical in allowing Ci to translocate into the nucles and activate downstream targets of the hedgehog pathway.<br />
-&nbsp;The pathway contains 3 homologs including sonic hedgehog, Indian hedgehog, and desert hedgehog.<br />
-&nbsp;The hedgehog protein is initially produced in its fully active form.<br />
||<br> In terms of how the hedgehog protein acts to produce its effect, it must first bind to Patched which activity is inhibiting Smoothened in the absence of the hedgehog protein. The protein acts to trap Patched in its inactive confirmational state cause internalisation and eventually degradation of the receptor. This relives the dephosporylation of the Smoothened, usually induced by Patched, allowing it to accumulate phosphate groups and thus activate. With regards to Ci translocation, SUFU usually inhibits this by leading to phosphorylation of Ci and eventually its cleavage into Ci repressor. During the activation of the hedgehog pathway there is a binding of Fused to Cos2 which phosphorylates SUFU to inactivate it, allowing Ci to translocate into the nucleus and activate downstream targets.<br />
<br />
{What are some of the roles of the Hedgehog signalling pathway in embryonic development as discovered through animal models? (select one or more options)<br />
|type="[]"}<br />
- &nbsp; Development of the hindbrain <br />
+ &nbsp; Activates the Epidermal growth factor receptor (EGFR) signalling pathway<br />
+ &nbsp; Development of craniofacial features<br />
- &nbsp; Development of the spinal nerves and meninges<br />
+ &nbsp; Development and patterning of the limb buds and sclerotomes<br />
||<br> The Hedgehog signalling pathway plays a significant role in forebrain, not hindbrain, development. Absence of this pathway results in holoprosencephaly (HPE), the lack of division of the forebrain into its 2 separate hemispheres, telencephalon and diencephalon.<br />
<br />
Studies on Drosophila melanogaster have indicated the role of the Hedgehog signalling pathway in the activation of the EGFR pathway in Drosophila head development.<br />
<br />
This pathway also plays a significant role in the development of craniofacial features, as it contributes to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm. Blockage of Shh signalling in chick embryos provides inside into the birth defects associated with lack of Shh involvement in craniofacial development. These defects include holoprosencephaly and, cleft lip and palate.<br />
<br />
The role of Hh signalling pathway in development of spinal nerves and meninges has not been observed within animal models but as discussed above, this pathway plays a significant role in other areas of embryonic development, such as forebrain and craniofacial development, germ cell proliferation, subdivision of the eye field, production of sclerotomes and patterning of limb buds.<br />
<br />
The role of this pathway in development and patterning of limb buds and sclerotomes was observed through experimentation on Shh knockout mice. The absence of this pathway resulted in a lack of vertebral column development. This deficiency of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population. Anterior limb bud cell death was also observed in these mice, indicating the role of Shh in patterning the anterior-posterior limb axis and even the proximal-distal limb segments, particularly in patterning of structures at the level of or distal to the latent elbow and knee joints. <br />
<br />
{A patient presents with crossed eyes, a pronounced forehead and an abnormally large head. Through an ultrasound it was also revealed the patient has an ovarian fibroma. Which of the following is the patient diagnosed with?<br />
|type="[]"}<br />
- &nbsp; Holoprosencephaly<br />
- &nbsp; Medulloblastoma<br />
+ &nbsp; Gorlin Syndrome<br />
- &nbsp; Cowden Syndrome<br />
||<br> The symptoms present in the patient correlate with Gorlin Syndrome. The patient is cross-eyed due to suffering from strabismus where the eyes do not properly align with eachother. A pronounced forehead is characteristic of frontal bossing and a large head is due to macrocephaly. Macrocephaly can arise due to an enlarged brain or excessive cerebrospinal fluid in the brain. Hedgehog, as well as being a developmental morphogen, regulates the proliferation and survival of stem cell populations, explaining its involvement in development of tumours. Patients with Gorlin syndrome often develop tumours throughout the body. <br />
<br />
{Question 5<br />
|type="()"}<br />
- &nbsp; <br />
- &nbsp; <br />
- &nbsp; <br />
+ &nbsp; <br />
||Replace with Answer<br />
<br />
{Question 6<br />
|type="()"}<br />
- &nbsp; <br />
- &nbsp; <br />
- &nbsp; <br />
+ &nbsp; <br />
||Replace with Answer<br />
</quiz><br />
<br />
==Glossary==<br />
<br />
{| class="pretty table"<br />
|-<br />
|'''Term'''<br />
|'''Definition'''<br />
|-<br />
|Acyl-transferase<br />
|A protein responsible for catalyzing the transfer of a palmitic acid moiety to the N-terminus of the hedgehog signalling molecule.<br />
|-<br />
|Ataxia<br />
|Lack of voluntary control and coordination of muscle movement often due to damage of the cerebellum, the region of the brain controlling muscle coordination<br />
|-<br />
|Bradycardia<br />
|Disruption of normal electric impulses controlling the pumping of the heart resulting in a slower heart rate<br />
|-<br />
|Brother of ihog (Boi)<br />
|A surface protein that enhances hedgehog signal transduction through PTC in ''Drosophila''.<br />
|-<br />
|Carcinoma<br />
|A malignant tumour of epithelial tissue of skin or tissues lining body organs<br />
|-<br />
|Casein kinase I (CKI)<br />
|A kinase that is thought to phosphorylate the Smoothened receptor to activate it in the hedgehog signalling pathway.<br />
|-<br />
|Cleft Palate<br />
|An opening or split in the roof of the mouth as a result of the palatal shelves not fusing, most often occurring in embryonic development. <br />
|-<br />
|Convulsion<br />
|Sudden, rapid, involuntary contraction of body muscles repeatedly <br />
|-<br />
|Cubitus interruptus (Ci)<br />
|A transcription factor found in the hedgehog signalling pathway of ''Drosophila'', which binds to promoter regions on the DNA in the nucleus to activate target genes of the pathway.<br />
|-<br />
|Costal-2 (Cos2)<br />
|A kinesin like protein which interacts with the C terminus of Smoothened and acts like a scaffolding protein and allows proteins such as Fused to bind to it.<br />
|-<br />
|Denticle<br />
|Bristle like projections off the segments on the ''Drosophila'' embryo.<br />
|-<br />
|Dally<br />
|An HSPG, which mediates loacalizaiton and transportation of the hedgehog protein to its targets in ''Drosophila''<br />
|-<br />
|Desert hedgehog (Dhh)<br />
|A homolog of the ''Drosophila'' hedgehog protein, which is expressed most prominently in the gonads of vertebrates, where it plays a possible role in regulating spermatogenesis. <br />
|-<br />
|Desmoplastic<br />
|A reaction involving growth of dense fibrous tissue around the tumour<br />
|-<br />
|Epilepsy<br />
|A neurological disorder whereby nerve cell activity in the brain becomes abnormal resulting in convulsions, or loss of consciousness<br />
|-<br />
|Frizzled<br />
|A receptor that is part of the Wnt signalling pathway, which binds the protein wingless in order to activate signalling cascades. <br />
|-<br />
|Frontal bossing<br />
|A pronounced forehead<br />
|-<br />
|Fused (Fu)<br />
|A kinase that binds to Costal-2 and acts to inhbit Suppressor of Fused by phosphorylating it in the hedgehog signalling pathway.<br />
|-<br />
|Gli<br />
|A family of proteins that acts as transcription factors that were originally isolated in human gliboblastoma. The proteins are important mediators in activating target genes for the hedgehog signalling pathway in vertebrates.<br />
|-<br />
|Glycipan (GPC)<br />
|A family of HSPGs which act in the hedgehog signalling pathway of vertebrates to either enhance or inhibit signal transduction depending on the isoform.<br />
|-<br />
<br />
|Hedgehog (Hh) protein<br />
|A signalling protein widely expressed in the tissue during embryonic development of vertebrates and some other species such as ''Drosophila'', and acts to pattern and develop tissue. The protein is the primary mediator of the pathway.<br />
|-<br />
|Heparin sulfate proteoglycan (HSPG)<br />
|A proteoglycan ,which is a heavily glycosolated protein, which in the context of hedgehog signalling is thought to aid in the localization and transport of hedgehog proteins to their targets.<br />
|-<br />
|Heterozygousity<br />
|Having different alleles of one gene<br />
|-<br />
|Hypoplasia<br />
|Arrested, incomplete development of an organ or tissue<br />
|- <br />
|Indian hedgehog (Ihh)<br />
|A signalling protein that is a homolog of the ''Drosophila'' hedgehog protein, that primarily acts in regions where there is endochondrial ossification to aid in the maturation of chondrocytes.<br />
|-<br />
|Interference hedgehog (Ihog)<br />
|A surface protein that enhances hedgehog signal transduction through PTC in ''Drosophila''.<br />
|-<br />
|Kif7<br />
|A homolog of Costal-2 in vertebrates, which acts to regulate the downstream signalling of the hedgehog pathway by causing the disassociation of SUFU and Gli.<br />
|-<br />
|Limb bud<br />
|A structure formed during early embryonic development consisting of ectoderm and mesenchyme representing the early limbs, where signalling processes in the bud will eventually lead to the out growth and patterning of the bud.<br />
|-<br />
|Macrocephaly<br />
|Abnormal enlargement of the head due to an enlarged brain or excessive accumulation of cerebrospinal fluid<br />
|-<br />
|Patched (PTC)<br />
|Patched is a transmembrane receptor expressed on cells that are sensitive to signalling via the hedgehog pathway, where its extracellular domain binds to the hedgehog protein to inactivate it. The receptor it self without hedgehog binding actively inhibits Smoothened. <br />
|-<br />
|Primary cilia<br />
|An organelle that consists of an outward projection from the cell surface, which is thought to be critical for hedgehog signalling in vertebrates as it houses many components of the pathway. <br />
|-<br />
|Protein kinase A (PKA)<br />
|A kinase that is thought to phosphorylate the Smoothened receptor to activate it in hedgehog signalling.<br />
|-<br />
|Smoothened (SMO)<br />
|A G-protein coupled receptor like receptor integral to the hedgehog signalling pathway and acts to set in motion a series of events that lead to the activation of transcriptional factors that activate target genes of the hedgehog pathway.<br />
|-<br />
|Sonic hedgehog (Shh)<br />
|The most widely expressed homolog of the ''Drosophila'' hedgehog protein found in vertebrates, playing a key role in embryonic development of humans.<br />
|-<br />
|Strabismus<br />
|Abnormal alignment of the eyes with eachother resulting in a cross-eyed appearance<br />
|-<br />
|Suppressor of Fused (SUFU)<br />
|A protein in the hedgehog signalling pathway which when active, inhibits the translocation of Cubitus interruptus into the nucleus by leading to its phosphorylation, and eventually degradation via the proteosome.<br />
|-<br />
|Wingless protein<br />
|A protein produced as a downstream target of the hedgehog signalling pathway in ''Drosophila'', which activates the Wnt pathway by binding to the Frizzled receptor.<br />
|-<br />
|Zone of polarizing activity (ZPA)<br />
|The posterior region of the limb bud mesenchyme, which aids in the signalling of it to pattern the posterior anterior axis with respect to the digits through mediators such as sonic hedgehog.<br />
|-<br />
|}<br />
<br />
===Additional Glossary Links===<br />
[[A|A]] | [[B|B]] | [[C|C]] | [[D|D]] | [[E|E]] | [[F|F]] | [[G|G]] | [[H|H]] | [[I|I]] | [[J|J]] | [[K|K]] | [[L|L]] | [[M|M]] | [[N|N]] | [[O|O]] | [[P|P]] | [[Q|Q]] | [[R|R]] | [[S|S]] | [[T|T]] | [[U|U]] | [[V|V]] | [[W|W]] | [[X|X]] | [[Y|Y]] | [[Z|Z]] | [[Numbers|#]]<br />
<br />
== References ==</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=2016_Group_Project_4&diff=255224
2016 Group Project 4
2016-10-27T10:37:23Z
<p>Z5018221: /* Quiz */</p>
<hr />
<div>{{ANAT2341Project2016header}}<br />
{{Group Assessment Criteria table}}<br />
<!-- Do not delete the above template from the Group project page. --><br />
<br />
= Hedgehog signalling pathway =<br />
==Introduction==<br />
[[File:Hedgehog.jpg|thumb|300px|An image of a hedgehog, the animal of which the Hh proteins are named after.]]<br />
The Hedgehog (Hh) signalling pathway is an important part of the early embryo with regards to the patterning and development of the nervous system, limbs and the cranio-facial region in vertebrates and the polarization of the segments in the ''Drosophila'' embryo. It was first identified in 1980 by Christiane Nüsslein-Volhard and Eric Wieschaus, alongside a group of other genes regulating segment polarity in ''Drosophila'' embryonic development<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. The pathway itself consists of Hh proteins, where there are three identified homologs in vertebrates, being sonic hedgehog (SHH), Indian hedgehog (IHH), and desert hedgehog (DHH) <ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. All homologs are expressed at varying levels within different tissues in the body, and also act as a form of redundancy to an extent between one another. <br />
<br />
The signaling pathway is highly conserved between various species<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. and acts via a G protein coupled receptor like receptor, which uninhibited via the action of the Hh proteins. The pathway overall acts via a balance of dephosphorylation<ref name="PMID10966113"><pubmed>10966113</pubmed></ref> and degradation of proteins<ref name="PMID15102702"><pubmed>15102702</pubmed></ref> in order to regulate transcription factor activity to express various genes to carry out its action. The Hh pathway is also highly implicated when it comes to abnormalities in development, as it is implicated in diseases such as holoprosencephaly and cleft lip and palate. Overall Hh signaling pathways play a large role in embryological development, which will be discussed in detail on this page.<br />
<br />
== History ==<br />
{| class="pretty table"<br />
| '''1980'''<br />
|Christiane Nüsslein-Volhard and Eric Wieschaus first identified a group of genes including those related to the Hedgehog signalling pathway and linked them to the segmentation and planning of the embryo in ''Drosophila melanogaster'' by introducing mutagenic substances to the developing embryo<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Multiple researchers including Andrew P. McMahon and Clifford Tabin discovered three equivalent homologs in vertebrates of the ''Drosophila melanogaster'' hedgehog gene, known as sonic hedgehog (Shh), desert hedgehog (Dhh) and indian hedgehog (Ihh), by looking at DNA sequences similar to that of the gene in the fruit fly<ref><pubmed>7916661</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Clifford Tabin and his lab identified the role of Shh in localising the limb bud, where they identified protein to be expressed within a region of the limb bud known as the zone of polarising activity (ZPA), showing that SHH is sufficient to induce the production of a ZPA, and thus limb bud formation in chick embryos<ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|Sonic hedgehog secreted by the notochord was identified to induce ventral cell types in the neural tube during embryonic development, most notably the floor plate cells and the motor neurons as shown in chick embryos. Such differentiation between the two cell types is thought to be a matter of sonic hedgehog concentrations experienced by the neural plate cells<ref name="PMID7736596"><pubmed>7736596</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|A shared Nobel prize in physiology or medicine was awarded to Christiane Nüsslein-Volhard and Eric Wieschaus for their researching regarding the identification of the developmental genes relating to the formation and patterning of the early embryo via genes.<br />
|-<br />
|'''1996'''<br />
|Studies showed that human homologs of the Patched gene, a component of the hedgehog pathway, is a key gene that is mutated in Gorlin Syndrome, which characterised by a predisposition for basal cell carcinomas, the most common cancers in humans and developmental abnormalities<ref name="PMID8658145"><pubmed>8658145 </pubmed></ref>.<br />
|-<br />
|'''1999'''<br />
|Researchers implicated Indian hedgehog as a key signalling molecule for the maturation and differentiation of prehypertrophic chondrocytes, where Indian hedgehog null mice were shown to have a lack of mature chondrocytes and no development of osteoblast cells in endochondrial bone. This was thought to be due to Indian hedgehog having a feedback signal controlling parathyroid hormone related protein, which regulates endochondrial bone development<ref name="PMID10465785"><pubmed>10465785</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Sonic hedgehog was identified to regulate the proliferation of adult neural stem cells as shown in the hippocampus of rats and in vitro for neural progenitor cells isolated from the hippocampus<ref name="PMID12469128"><pubmed>12469128</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Studies on Shh function found that it can act as a chemoattractant in the developing embryo spinal cord, to help guide commissural axons to the midline of the floor plate<ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
|-<br />
|'''2009'''<br />
|Mouse models showed that reduction in hedgehog signalling allows for transient improved response to chemotherapy with regards to mouse models of human pancreatic ductal adenocarcinoma, a cancer with one of the highest mortality rates in humans<ref name="PMID19460966"><pubmed>19460966</pubmed></ref>.<br />
|}<br />
<br />
This time line regarding the discoveries in the hedgehog signalling pathway is by no means exhaustive, but a selection of relatively large discoveries that had a significant impact in the field on the basis of citations.<br />
<br />
== Origin of name ==<br />
<br />
[[File:Bands of denticles in normal and Hh mutant Drosophila embryo.jpeg|thumb|250px|Differences in patterning of the denticle bands in normal and mutated hedgehog gene variant ''Drosophilia'' embryo]]<br />
<br />
The name hedgehog came about when Christiane Nüsslein-Volhard and Eric Wieschaus first identified the group of genes controlling polarization of the segments in the ''Drosophila'' early embryo. They noticed that when they mutated the Hh gene, making it non-functional, that the bands of denticles formed during the early ''Drosophila'' embryo formation became more diffuse as opposed to being distinct normally. The denticles would all clump together forming a single patch on the surface of the embryo, as opposed to normally outlining the distinct segments of the embryo as bands<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. This gave the embryo spiny and prickly look similar to that of the back of a hedgehog.<br />
<br />
From there on in the gene was called the hedgehog gene where homologs in vertebrates discovered along the line kept to this naming structure giving various species of hedgehog names to the genes such as Indian hedgehog, and desert hedgehog, with the exception being sonic hedgehog, which is named after a fictional character in the video game “Sonic the Hedgehog”.<br />
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== Mechanism of signalling ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br>[[File:Hh signalling pathway.jpg|thumb|600px|Diagrammatic representation of the steps and components involved in the hedgehog signalling pathway in both ''Drosophila'' and mammals.]]<br />
<br />
The Hh signaling pathway has been well studied in ''Drosophila melanogaster'', and has been shown the be conserved to an extent across it and mammals making the species a suitable model for Hh signalling in humans<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. In ''Drosophila melanogaster'', the Hh pathway begins when the Hh proteins bind to the extracellular domain of the transmembrane protein known as Patched (PTC). Such binding is thought to be greatly enhanced by the presence of proteins known as interference hedgehog (ihog) and brother of ihog (boi), which have shown to be essential to allowing hedgehog binding to inactivate PTC<ref name="p20048000 "><pubmed>20048000 </pubmed></ref>. It has also been demonstrated heparin sulfate proteoglycans (HSPG) such as dally also aid in the modulation of hedgehog signalling, where they act to localise and transport the hedgehog protein to the target receptors<ref name="p14602684"><pubmed>14602684</pubmed></ref> <ref name="p10549295"><pubmed>10549295</pubmed></ref>. Overall hedgehog binding leads to inactivation of PTC which occurs by Hh trapping PTC in an inactive conformational state<ref><pubmed>27647915</pubmed></ref>. After binding of Hh occurs to PTC and it is inactivated, the receptor and Hh protein is thought to be endocytosed by the cell where they undergo lysosomal degradation in order to limit Hh concentration, thus limiting its spread to other cells and PTC activity<ref name="PMID15102702"><pubmed>15102702</pubmed></ref>. In the absence of Hh, PTC acts to suppress the expression of the Smoothened (SMO), a G-protein coupled receptor like receptor, and thus its signaling. How PTC achieves this inhibition of SMO is currently unclear. Studies have suggested that due to the highly phosphorylated nature of SMO when active, that PTC acts to dephosphorylate SMO in order to repress its signaling. It is thus that binding of Hh to PTC reduces PTCs ability to promote dephosphorylation of SMO, leading to its increased activity and expression on the cell surface <ref name="PMID10966113"><pubmed>10966113</pubmed></ref>. It is thought that the phosphorylation required to activate SMO are dependent on protein kinase A (PKA) and casein kinase I (CKI) <ref><pubmed>15616566 </pubmed></ref>.<br />
<br />
This overall increased phosphorylation of SMO due to a repression of PTC activity by Hh leads to an accumulation of SMO on the cell surface, which collectively allows for SMO to exert its activity. Importantly the phosphorylation also disrupts intramolecular electrostatic interactions between SMO molecules which switches the molecule into its active conformational state <ref><pubmed>17960137 </pubmed></ref>. Generally, SMO has been shown to have very little signal transducing ability, and thus this accumulation allows it to jointly transduce a substantial signal. This occurs by the C terminus of SMO on the intracellular domain interacting with the kinesin like protein Costal-2 (Cos2), which is thought to bind to microtubules in order to acts as a scaffolding protein <ref><pubmed>18691888 </pubmed></ref>. Such interactions induce the formation of a complex including the kinase known as Fused (Fu) and Cos2, which phosphorylates Suppressor of Fused (SUFU) to inhibit it. Without this inhibition SUFU goes onto prevent the translocation of the transcriptional factor Cubitus interruptus (Ci) into the nucleus by leading to its phosphorylation, and subsequently its partial cleavage via the proteosome. The partial cleavage of Ci leaves a lower molecular weight protein known as Ci repressor (CiR) or Ci75, which translocates into the nucleus and acts to repress the target genes of the Hh signalling pathway via Ci<ref><pubmed>9215627</pubmed></ref>. Thus overall inhibition of SUFU increases the amount of Ci entering into the nucleus of the cell, and activating transcription of target genes of the Hh pathway<ref><pubmed>10952898 </pubmed></ref>. Activation of SMO also promotes disassociation of present SUFU-Fu-Cos2-Ci complex which which generally when fully intact leads to cleavage of Ci into its repressor form<ref name="p15063184"><pubmed>15063184</pubmed></ref><ref name="p17881487"><pubmed>17881487</pubmed></ref>.<br />
<br />
At this point Ci is able to activate the transcription of various genes, which include importantly the ''ptc'' gene, which encodes the PTC receptor. It is thus as a result of this, that PTC expression will be increased in response to Hh pathway induction, which negatively feeds back to reduce Ci signaling induction, in order to maintain homeostasis and regulate the intensity and duration of the signaling from Hh<ref><pubmed>9053330</pubmed></ref>. Furthermore the ''wg'' gene, encoding the wingless protein is also activated by Ci, which leads to activation of the Wnt pathway via the Frizzled receptor in adjacent cells expressing the gene ''engrailed'' <ref><pubmed>9502727</pubmed></ref> <ref><pubmed>10457026</pubmed></ref>. This overall stabalizes the boundaries between the segments of the developing ''Drosophila melanogaster'' signalled by the gene ''engrailed''<ref><pubmed>3282172</pubmed></ref>.<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=w1xXD9kss2w</html5media><br />
<br><br><br />
An overview of the hedgehog signalling pathway in ''Drosophila''<ref>YouTube. (2016). The Hedgehog signalling pathway in Drosophila online Available at: https://www.youtube.com/watch?v=w1xXD9kss2w</ref>.<br />
<br />
=== Mammals ===<br />
<br />
Although the Hh signaling pathway has been conserved across species to an extent <ref name="PMID8595881"><pubmed>8595881</pubmed></ref>, key differences exist when observing the pathway within mammalian tissue in contrast to that which has been studied in ''Drosophila melanogaster''. In mammalian cells and all other vertebrates, Hh signalling is dependent on an organelle known as the primary cilia, which are projections outwards from the cells surface. The importance of such an organelle in the signalling pathway comes as a result of PTC1, one of the two PTC receptor homologs in mammals, that binds to the Hh homolog Sonic Hh (Shh), exists within the cilia<ref><pubmed>17641202</pubmed></ref>. Similarities also exist between signalling in the vertebrates and ''Drosophila''. This includes the surface proteins such as Cdo and Brother of cdo (Boc), which act in a similar fashion to ihog and boi in enhancing the binding of the hedgehog protein to PTC<ref><pubmed>16647304</pubmed></ref>. HSPGs such as gylcipans (GPC) 1, 2, 3, 4, 5 and 6 are also thought to play a role in hedgehog signalling in vertebrates with regards to stimulaiton or inhibition of the pathway depending on the isoform<ref><pubmed>26627558</pubmed></ref>. The mechanism of action of SMO inhibition and activation is poorly understood currently, but evidence has suggested that PTC1 acts to inhibit SMO when unbound to Shh by acting as a pump to remove oxysterols from the cilia into the extracellular space<ref><pubmed>PMC1462959</pubmed></ref>. These oxysterols are normally thought to bind and accumulate around the SMO receptors, which in turn prevents internalization and deactivation of SMO, leading to it accumulating on the apical primary cilia<ref><pubmed>16136078</pubmed></ref>. Other studies have also suggested that Shh has a role in increasing phosphorylation of SMO via kinases such as CK1, which causes it to accumulate on the cilia<ref><pubmed>21695114</pubmed></ref>. Overall the net action of Shh initially is believed to cause accumulation of SMO at the cilia by inhibiting PTCH1 and phosphorylation of SMO.<br />
<br />
How SMO acts next is relatively unknown but, it has been shown to promote the disassociation between SUFU and Gli transcription factor, which allows Gli to be transported to the nucleus to activate effector genes of the pathway. Gli is normally bound in the cytoplasm to SUFU, where SUFU promotes the partial degradation of Gli into its repressor form, similar to that in the fruit fly model<ref><pubmed>20360384</pubmed></ref>. Alongside this, Kif7, a Cos2 homolog, has been shown to migrate to the apex of the cilium in response to SMO accumulation at the cilium, where it has been postulated to also promote disassociation of SUFU and Gli<ref><pubmed>19592253</pubmed></ref>. On the other hand, Kif7 is also thought to play an inhibitory role for the signalling pathway as when it is localized at the base of the cilia in the absence of Hh signaling, where it acts to traffic Gli transcription factors away from the cilia<ref><pubmed>19666503</pubmed></ref>. This all leads to an accumulation of active Gli transcription factors which migrate to the nucleus in order either inhibit or activate gene transcription in response to Hh signaling. These Gli transcription factors include Gli1, Gli2, and Gli3, where Gli2 and Gli3 in their activated form are the primary mediators of the pathway, and also act to repress the target genes when hedgehog signalling is absent. Gli3 is considered to be the major repressor of the pathway when the full length version of the Gli3 protein is partially cleaved into its repressor form <ref><pubmed>10433919</pubmed></ref>. Gli1 on the other hand is one of the targets of hedgehog signalling promoted by Gli2 and Gli3 activators, and acts to reinforce the hedgehog pathway through a positive feedback loop <ref><pubmed>10075717</pubmed></ref>. As a result Gl1 is considered as not entirely essential ,where mice models with no production of Gl1 have shown viability with few defects<ref><pubmed>10725236</pubmed></ref>. That being said, other studies have shown the importance of Gl1 as a downstream target of sonic hedgehog, where it is thought to induce ventral neural tube development, as it is on the only Gli factor present in the floor plate during gastrulation<ref><pubmed>9216996</pubmed></ref>. Overall the interactions between such transcription factors are still relatively unknown, where further research is required to elaborate on the specific roles in the hedgehog pathway they each have.<br />
<br />
== Function ==<br />
===Overview===<br />
{| class="pretty table"<br />
|'''Hedgehog protein homolog'''<br />
|'''Function'''<br />
|-<br />
| Sonic hedgehog [http://www.omim.org/entry/600725 OMIM entry] ||<br />
*Expressed in zone of polarizing activity of the limb bud where it plays a role in helping to pattern the anterior and posterior aspect of the limbs <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
*Based on time and concentration of SHH due to diffusion from the point of secretion in the limb bud, SHH also plays a role in determining digit identity <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>.<br />
*Acts as a chemoattractant to guide commissural axons in the floor plate of the neural tube towards the midline <ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
*Patterns the developing cusps of the teeth and their relative positions in the jaw, and is also essential for the growth of the teeth <ref name="PMID11044393"><pubmed>11044393</pubmed></ref>.<br />
*SHH released from the notochord acts to induce formation of the floor plate, motor neurons, and dopaminergic neurons, as well as signalling the induction of the ventral cell types in the neural tube <ref name="PMID8790332"><pubmed>8790332</pubmed></ref>.<br />
|-<br />
| Desert hedgehog [http://www.omim.org/entry/605423 OMIM entry]||<br />
*Plays a possible role in regulating spermatogenesis as due to the highly localised expression in the testes by pre-Sertoli cells, and the fact that mice with no DHH present are infertile, with no mature spermatozoa <ref name="PMID8805249"><pubmed>8805249</pubmed></ref>. <br />
*DHH derived from Schwann cells signal development of peripheral nerves, by inducing the production of a connective tissue sheath around them <ref name="PMID10482238"><pubmed>10482238</pubmed></ref>.<br />
|-<br />
| Indian hedgehog [http://www.omim.org/entry/600726 OMIM entry]||<br />
*Aid in the signalling of proliferating chondrocytes to undergo hypertrophic differentiation during endochondral ossification<ref name="PMID8662546"><pubmed> 8662546</pubmed></ref>.<br />
*Plays a key role in yolk sac angiogenesis, as seen in studies where an absence of IHH leads to death of the embryo due to poor yolk sac vasculature <ref name="PMID11807029"><pubmed>11807029</pubmed></ref>.<br />
|}<br />
<br />
===Limb development===<br />
<br />
====Research background====<br />
<br />
The hedgehog signalling pathway plays a significant role with regards to the embryonic development of the limbs in vertebrates, specifically SHH. For a while the mechanism of which the limb was patterned on the anterior to posterior axis was quite unknown. Early studies had shown that grafting posterior wing bud cells to the anterior region of the wing bud in a chick embryo, an equal amount of extra digits was produced to that of which was normally produced, and in a mirror image pattern<ref name="PMID4390734"><pubmed>4390734</pubmed></ref>. This showed that the pattern of which the digits were produced were polarized with respect to that of the graft from the limb bud, which has become to be described as the zone of polarizing activity (ZPA). Further studies mapped the ZPA, by showing the area of the wing bud on the chick with the highest polarizing activity to be the posterior margin of the wing bud<ref name="PMID4719010"><pubmed>4719010</pubmed></ref>. Furthermore, studies later on found that the amount or concentration of ZPA cells grafted played a role in the amount of digits induced and how polarized they were<ref name="PMID7453825"><pubmed>7453825</pubmed></ref>. This ultimately gave rise to studies regarding a potential morphogen, which could potentially provide this concentration dependent activity of polarization when it comes to the limb bud. Studies to find this morphogen led to the discover of the ability for retinoic acid to mimic the polarizing action of the ZPA when applied locally to the limb bud<ref name="PMID7070499"><pubmed>7070499</pubmed></ref>. This was found to be due to the induction of a second morphogen known as SHH, where when cells that express SHH are grafted onto the limb bud, polarized digit development is induced<ref name="PMID7720566"><pubmed>7720566</pubmed></ref>.<br />
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====Polarizing activity of sonic hedgehog====<br />
[[File: Mechanims of patterning the digits on the posterior to anterior axis of the limb bud by sonic hedgehog.jpg|thumb|450px|Regions of the limb bud and the digits they form based on patterning of the posterior to anterior axis of the limb bud by mechanisms mediated by sonic hedgehog.]]<br />
More recent studies have sought to elucidate how SHH mediates such a polarizing effect in terms of digit identification and its underlying mechanism. It has been suggested that such an effect is heavily concentration dependent similar to that of when transplanting the chick wing bud ZPA cells, acting in a dose dependent matter, due to the ability of SHH to modulate signaling at long ranges via diffusion<ref name="PMID11389830"><pubmed>11389830</pubmed></ref>. This implies that a gradient of varying concentrations of SHH diffused through the mesenchyme of the limb bud leads to the identification of posterior and anterior digits.<br />
<br />
Current research has also suggested that not only is the concentration gradient of SHH important for the patterning of the digits, but also the temporal gradient, being the length of time of exposure of SHH to the mesenchyme of the limb bud. Studies have shown in mice that of the 5 digits, polarization from the posterior end, being digit 5, to the anterior end being digit 1 are due to different mechanisms. Digits 5 and 4 have been shown to be comprised of the SHH expressing cells and thus both experience maximal levels of SHH, and thus cannot be distinguished on the basis of a concentration gradient. As a result, temporal gradients are employed, where the expression of SHH in both regions that become the digits vary, where studies have shown that SHH expression in the primordium of digit 5 is maintained longer than that in digit 4 gradient <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>. When it comes to digit 3 and 2, there is differentiation based on the concentration gradient of SHH from the ZPA, where due to the ZPA being further away to digit 2 than 3, the concentration of SHH will be higher at 3<ref name="PMID15315763"><pubmed>15315763</pubmed></ref> <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>. In terms of digit 1, the levels of SHH are so low at this point that it is said to be SHH independent, and actually reliant on the absence of SHH for normal differentiation. With regards to how SHH actually mediates its action, it is thought to be by a balance between the transcription factor Gli3 and SHH expression, which activates Gli1, Gli2 and Gli3 repressor, effectively counteracting Gli3. Gli3 is considered to promote the inhibition of digit formation and identification, while the downstream targets of SHH are thought to promote it<ref name="PMID17400206"><pubmed>17400206</pubmed></ref>.<br />
<br />
Other research has also shown the possibility of SHH signaling as a way to prime the posterior mesenchyme and induce the production of bone morphogenetic protein 2 (bmp2), which is thought to be the morphogen creating the chemical gradient for digit identification<ref name="PMID10704381"><pubmed>10704381</pubmed></ref>. Overall the mechanism at which SHH work to pattern the posterior anterior axis of the limb bud is still relatively unknown, and further research is being conducted to elucidate how the underlying mechanisms such as the downstream targets of SHH affect digit formation.<br />
<br />
=== Neural development ===<br />
<br />
====Research background====<br />
Research on the role of the notochord, a cartilaginous structure derived from the mesoderm, initially observed its ability to induce the floor plate within the neural tube of chick embryos<ref name="PMID3354847"><pubmed>3354847</pubmed></ref>. This induction of a floor plate occurred in the ventral midline of the neural tube, where the floor plate itself is thought to have signalling effects regarding patterning of the spinal cord. Alongside this, research also noted that the floor plate and notochord collectively had signalling effects that patterned the differentiation of the neural cells in the neural tube<ref name="PMID1991324"><pubmed>1991324</pubmed></ref>. Such observations lead to research being directed at how this patterning of the neural tube is mediated through the notochord. It had been suggested that the morphogen known as Shh was to play due to its high expression within the notochord and floor plate. It also was showed to activate floor plate expressed genes when ectopically expressed in the mouse CNS<ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. Furthermore, observations regarding the Shh also lead to implicating it in the differentiation of distinct cell types in the ventral neural tube such as motor neurons, alongside the already identified floor plate<ref name="PMID8124714"><pubmed>8124714</pubmed></ref>. Studies looking specifically at the targets of Shh signalling in the neural tube also identified that using antibodies to block the protein would lead to blocking of the induction of the motor neurons, and that applying Shh to explants induced floor plate and motor neurons in a variety of vertebrate models<ref name="PMID7753196 "><pubmed>7753196 </pubmed></ref>. This for the most part formed the basis of research on the specific patterning effects of Shh secreted from the notochord and floor plate on the ventral neural tube.<br />
<br />
====Patterning of ventral nerve cell types in the neural tube====<br />
As stated, the inductive signals from the notochord in the form of Shh <ref name="PMID7753196"><pubmed>7753196 </pubmed></ref> are primarily responsible for the formation of the floor plate in the ventral midline of the neural tube during embryonic development<ref name="PMID3354847"><pubmed>3354847</pubmed></ref>. The floor plate itself acts in the same fashion as the notochord with regards to expression of Shh for mediatating its signal. Collectively it is thought that the notochord and the floor plate provide a Shh graded response, where there is a gradient of concentrations along the dorsoventral axis of the developing neural tube<ref name="PMID9598380"><pubmed>9598380</pubmed></ref>. As a result, it is believed that the degree of Hh signalling on a cell type is responsible for the differentiation of progenitor cells it to various types. Specifically, with regards to the floor plate, the distinct local signal, given the close proximity of the notochord to the floor plate induction site is responsible for inducing the floor plate<ref name="PMID9598380"><pubmed>9598380</pubmed></ref>. It is thought that through interacting with the receptor PTC, the pathway activates the transcription of hepatocyte nuclear factor 3β (HNF-3β), a gene that has been shown to be commonly expressed in the floor plate. Such a gene is activated by the transcription factors Gli1 and Gli2. Thus HNF-3β is considered to be the downstream target of Shh signalling leading to the induction of the floor plate<ref name="PMID9118802"><pubmed>9118802</pubmed></ref>. It is also believed that HNF-3β is essential for notochord formation as well, as seen in mice models with HNF-3β knocked out, leading to dorsoventral patterning issues<ref name="PMID8069909"><pubmed>8069909</pubmed></ref>. Overall the induced floor plate acts to further aid the notochord in producing a graded Shh response to pattern the ventral neural tube<ref name="PMID1991324"><pubmed>1991324</pubmed></ref>.<br />
<br />
=== Organogenesis ===<br />
The Hedgehog Signalling pathway is a pathway sending information to embryonic cells which plays an especially important role in the regulation of organogenesis. These processes include the organization of the brain (craniofacial) and the growth of appendages with further studies implicating the Hedgehog Signalling pathway in the development of the small intestine, lungs and the pancreas.<br />
<br />
== Animal models ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br>[[File:Hedgehog signalling on plane polarity of denticles in Drosophila.png|thumb|400px|Image of denticles on the ''drosophila'' embryo used as a model to research plane polarization of cells by looking at the orientation of the denticles on the ''drosophila'' embryo in response to many signalling molecules including hedgehog.]]<br />
<br />
Hedgehog (Hh) protein signal was initially discovered through experimentation on the fruit fly, "Drosophila melanogaster". It is through this model that we are able to discover not only the functional components of this pathway but also understand its role in embryonic development. Through application of this information on the human biological system we are able to find the cause and thus potential treatments of defects and diseases caused by interruption or mutation of the Hedgehog signalling pathway. <br />
<br />
Upon further research on Drosophila it was found that Hh may play a role in germ cell proliferation and in particular, may control the proliferation and activity of somatic cells found within the germarium, which is the most anterior structure within the Drosophila ovary. <ref>Ovaries (Drosophila) definition. (2016). Groups.molbiosci.northwestern.edu. Retrieved 10 September 2016, from http://groups.molbiosci.northwestern.edu/holmgren/Glossary/Definitions/Def-D/Drosophila_Ovaries.html</ref> Thus, the Hh signalling pathway is vital in egg chamber formation and its consequent envelopment, budding and polarisation. It has also been observed that somatic cell proliferation is dependent on this pathway and thus, the number of pre-follicle cells is subject to the effect of the Hh signalling pathway. <ref><pubmed>8620839</pubmed></ref> Further studies have also indicated the role played by this pathway in activating the Epidermal growth factor receptor (EGFR) signalling pathway as seen in the induction of EGFR by Hh in Drosophila head development. <ref><pubmed>10331974</pubmed></ref> In addition, research on Drosophila has indicated the direct effect of Hh signalling on tracheal branch patterning. <ref><pubmed>11290298</pubmed></ref><br />
<br />
Despite ongoing research on "Drosophila melanogaster" to uncover the workings of the Hedgehog signalling pathway, further research is needed to confirm and further current findings. In addition, it is evident that it is through the study of these fruit flies that we are able to gain a basis of understanding of the causes of certain human diseases and thus propel research into treatments for sufferers.<br />
<br />
===Blockage of Shh Signalling in Forebrain Neuroectoderm of Chick Embryos===<br />
<br />
The Hedgehog signalling pathway plays a significant role in embryonic development, particularly of the forebrain. Due to its role in development of craniofacial features by contributing to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm, a disruption in this pathway can result in a variety of birth deformities including holoprosencephaly (HPE), where the prosencephalon (forebrain) fails to divide into 2 separate hemispheres, telencephalon and diencephalon <ref>Holoprosencephaly - NORD (National Organization for Rare Disorders). (2016). NORD (National Organization for Rare Disorders). Retrieved 10 September 2016, from http://rarediseases.org/rare-diseases/holoprosencephaly/</ref>, as well as cleft lip and palate. The function of Sonic Hedgehog (Shh) and its signalling pathway on the formation of forebrain neuroectoderm was studied in chick embryos.<br />
<br />
It was found that the disruption of Shh signalling in the neural tube of chick embryos resulted in the lack of division of the forebrain into the diencephalon and telencephalon. This is in fact, as stated earlier, the fundamental cause of the rare condition, holoprosencephaly. It was discovered that the Shh signalling pathway in the diencephalon was responsible for gene expression in the telencephalon. <br />
<br />
In addition, through experimentation on chick embryos it was found that through Shh signalling the development of the forebrain regulates and controls facial morphogenesis, particularly of the upper and middle face. Therefore, interference with Shh signalling in the forebrain prevents this intrinsic communication, thus hindering Shh expression in facial ectoderm. This results in brain malformation accompanied by facial disfiguration as seen in patients suffering from HPE. Other malformations caused by blockage of Shh signalling in craniofacial development include, hypotelorism (decreased space between the orbits), growth restriction as well as cleft lip and palate as mentioned previously. <br />
<br />
A commonality discovered among all forms of Shh signalling disruption was two facial defects, “the loss of mediolateral expansion of the face and absence of proximodistal outgrowth of the frontonasal prominence”<ref><pubmed>15979605</pubmed></ref> (Ralph et al., 2005). Through reference to studies performed on chick and mice embryos, it was found that Shh signalling is particularly vital in development of maxillary and frontonasal components of the cranium.<br />
<br />
This breakthrough study on the inhibition of Shh signalling in chick embryos has significantly filled the gap in our understanding of the Sonic Hedgehog signalling pathway. It is evident that this pathway is crucial in the development of the forebrain and in turn regulates and controls the development of the facial skeleton. This is further proven through the observation that in the event of Shh signalling inhibition there is a development of craniofacial malformations.<br />
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=== Shh knockout mice ===<br />
<br />
Extensive research on Shh knockout mice allowed discovery of the roles of Shh in embryonic development and patterning of the limb buds and sclerotomes, and maintenance of the notochord. <ref><pubmed>8837770</pubmed></ref> These mice expressed defects in the cephalic neural tube with the fusion of telencephalic and optic vesicles. Through this research it is evident that Shh is partially responsible for the subdivision of the eye field through forebrain optic stalk development, along with formation of the ventral midline. It is these forebrain abnormalities established in the absence of Shh that results in congenital malformations of holoprosencephaly, development of a single nasal chamber and other facial defects in humans. <br />
<br />
The absence of the vertebral column including, the intervertebral discs and vertebrae along with the medial regions of the ribs were observed within Shh knockout mice. This lack of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population (Chiang et al., 1996). In addition, though the role of Shh in patterning the anterior-posterior limb axis is evident through anterior limb bud cell death in the absence of Shh, it is also responsible for the development of proximal-distal limb segments, particularly in the patterning of structures at the level of or distal to the latent elbow and knee joints. <ref><pubmed>11476582</pubmed></ref> This was perceived after observing the incomplete formation of distal limb structures with abnormal anterior-posterior axis formation (Chiang et al., 2001). Thus, Shh knockout mice provide great insight into the functions of Shh in embryonic development and the abnormalities formed in the absence of this signalling protein. <br />
<br />
== Clinical Significance ==<br />
<br />
===Gorlin Syndrome===<br />
[[File:1 week year old newborn girl with cleft lip and palate.png|thumb|An image of a 1 week year old newborn girl with cleft lip and palate]]<br />
Gorlin syndrome, also known as nevoid basal cell carcinoma syndrome, is a heritable disease resulting from heterozygousity in Hh receptor, Patched (PTC). The PTC gene encodes a protein which binds sonic hedgehog (Shh) and it is this binding which inhibits the Hh signalling pathway. However mutation of PTC leads to activation of the pathway <ref><pubmed>9620294</pubmed></ref>. The syndrome is characteristic of skin cancer basal cell carcinoma and cerebellum cancer medulloblastoma. 1-2% of medulloblastomas and 0.5% of basal cell carcinomas are attributable to the disease. Patients present with craniofacial and brain abnormalities such as cleft palate, strabismus, macrocephaly, abnormal development of the corpus callosum and frontal bossing, with an overall overgrown appearance. Skeletal defects such as of the shoulder, ribs and vertebrae are often seen, as well immobile thumbs and polydactyly, which is a deformity of the hand or feet in which they have one or more extra fingers or toes. Apart from physical anomalies, patients have an increased risk of tumours throughout the body including cardiac, ovarian fibromas, ovarian dermoid cysts, meningiomas, and fibrosarcomas. Additionally with time, patients eventually undergo intracranial calcification and dyskeratotic pitting of the hands and feet whereby skin cells prematurely convert to keratin <ref><pubmed>8681379</pubmed></ref>.<br />
<br />
===Holoprosencephaly===<br />
<br>[[File:Semilobar holoprosencephaly.jpg|thumb|240px|MRI of fore brain depicting semilobar holoprosencephaly]]<br />
Holoprosencephaly (HPE) is a congenital disease caused by incomplete division of the prosencephalon (embryonic forebrain) into separate lobes of the cerebral hemispheres. The Shh gene has been identified as a HPE-causing gene however recent evidence has also investigated into the PTC gene, which acts to repress Shh signalling. A gain in repressive action of PTC is seen, leading to decreased Shh signalling, and thus HPE <ref><pubmed>11941477</pubmed></ref>. Clinical expression is variable between patients and is dependent upon the 3 forms of increasing severity: lobar, semi-lobar and alobar HPE, where patients can present with right and left ventricles however with a continuous frontal cortex in lobar HPE, to carrying a single cerebral ventricle in alobar HPE. Along with forebrain abnormalities, facial anomalies are also seen including midline cleft lip and/or flat nose, ocular hypotelorism characteristic of a small distance between the eyes. In severe rare cases of cyclopia, a non-functioning nose may be observed in the form of proboscis and the patient may present with a single eye at the root of the nose <ref><pubmed>20583177</pubmed></ref>. Furthermore, patients with HPE often develop a large number of medical issues including epilepsy, mental retardation, thyroid and adrenal hypoplasia due to lack of hypothalamus or pituitary gland development, and diabetes insipidus.<br />
<br />
===Medulloblastoma===<br />
Medulloblastoma is a cancerous tumour of the cerebellum where the cells of origin are the granular cell precursors found in the neonatal cerebellum, explaining its high prevalence in children <ref><pubmed>19171780</pubmed></ref>. Commonly, medulloblastomas are found deep in the cerebellum along the midline, however with desmoplastic medulloblastomas, they are found more laterally and superficial. As seen previously with Gorlin syndrome and holoprosencephaly, PTC is also associated with the development of medulloblastoma, and misregulation of Hh-PTC signalling in cells of the external germinal layer, the layer found on the surface of the cerebellum, is thought to give rise to the tumour. In experimental studies, it has been discovered that PTC is highly transcribed in medulloblastomas and in approximately 30% of PTC heterozygous mice the tumour develops <ref><pubmed>9205058</pubmed></ref> <ref><pubmed>9262482</pubmed></ref>. In patients with medulloblastoma, often children, the most common symptoms seen are vomiting, ataxia, psychomotor regression, drowsiness and anorexia. With age, patients are seen to get more frequent headaches, and show psychological symptoms such as behavioural problems, poor performance in school, and anxiety. In patients exhibiting life-threatening symptoms due to increased intracranial hypertension, bradycardia, convulsions and coma are often seen <ref><pubmed>21537925</pubmed></ref>.<br />
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Watch below for a breakdown on Hedgehog's role in Tumour Development!<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=gFWO3I-oqsE</html5media><br />
<br><br><br />
An overview of the Hedgehog Signalling Pathway in Tumour Development<ref>YouTube. (2016). The Hedgehog Signaling in the Tumor Microenvironment - Research Hedgehog online Available at: https://www.youtube.com/watch?v=gFWO3I-oqsE</ref>.<br />
<br />
<br />
<br />
== Current research ==<br />
<br />
==Quiz==<br />
<br />
<quiz display=simple><br />
<br />
{Which of the following are the reasons that are thought to allow for the patterning of digits in vertebrates.<br />
|type="[]"}<br />
+ &nbsp;Concentration gradient of sonic hedgehog.<br />
+ &nbsp;Temporal gradient of sonic hedgehog.<br />
- &nbsp;The varying homologs of the hedgehog proteins .<br />
- &nbsp;The length of the hedgehog molecule.<br />
+ &nbsp;No sonic hedgehog signalling.<br />
- &nbsp;The type of cholesterol attached to the hedgehog molecule.<br />
||<br> For differentiation of the individual digits in mice to occur it is thought that each digit requires a different signalling mechanism. Digits 5 and 4 which are most posterior, are derived from the region around the zone of polarising area which contain Shh secreting cells, meaning these regions will experience a saturation of Shh signalling and cannot be differentiated by Shh concentration. As a result it is thought that these digits are identfied based on the temporal gradient, meaning that the length of which Shh is expressed in these regions differentiates the digits from one another with digit 5 expressing Shh for longer. Digits 3 and 2 are further away but still receive Shh signalling due to the diffusible nature of Shh from the ZPA, which forms a concentration gradient. This means the the concentration at digit 2 will be less than digit 3 due to being further away from the ZPA and thus can be differentiated from one another based on this concentration. Finally the digit 1 is differentiated on the basis of not receiving any Shh signalling at all. Thus it is a combination of concentration gradient of Shh, temporal gradient of Shh, and independence from Shh.<br />
<br />
{Which of the following are correct with regards to the hedgehog signalling pathway in ''Drosophila''.<br />
|type="[]"}<br />
-&nbsp;It occurs at the cillum on the cell surface.<br />
-&nbsp;Hedgehog protein binding to the Patched receptor activates it to inhibit Smoothened.<br />
+&nbsp;Hedgehog protein binding to the Patched recetpor inhibits it to activate Smoothened. <br />
+&nbsp;Inhibition of SUFU is critical in allowing Ci to translocate into the nucles and activate downstream targets of the hedgehog pathway.<br />
-&nbsp;The pathway contains 3 homologs including sonic hedgehog, Indian hedgehog, and desert hedgehog.<br />
-&nbsp;The hedgehog protein is initially produced in its fully active form.<br />
||<br> In terms of how the hedgehog protein acts to produce its effect, it must first bind to Patched which activity is inhibiting Smoothened in the absence of the hedgehog protein. The protein acts to trap Patched in its inactive confirmational state cause internalisation and eventually degradation of the receptor. This relives the dephosporylation of the Smoothened, usually induced by Patched, allowing it to accumulate phosphate groups and thus activate. With regards to Ci translocation, SUFU usually inhibits this by leading to phosphorylation of Ci and eventually its cleavage into Ci repressor. During the activation of the hedgehog pathway there is a binding of Fused to Cos2 which phosphorylates SUFU to inactivate it, allowing Ci to translocate into the nucleus and activate downstream targets.<br />
<br />
{What are some of the roles of the Hedgehog signalling pathway in embryonic development as discovered through animal models? (select one or more options)<br />
|type="[]"}<br />
- &nbsp; Development of the hindbrain <br />
+ &nbsp; Activates the Epidermal growth factor receptor (EGFR) signalling pathway<br />
+ &nbsp; Development of craniofacial features<br />
- &nbsp; Development of the spinal nerves and meninges<br />
+ &nbsp; Development and patterning of the limb buds and sclerotomes<br />
||<br> The Hedgehog signalling pathway plays a significant role in forebrain, not hindbrain, development. Absence of this pathway results in holoprosencephaly (HPE), the lack of division of the forebrain into its 2 separate hemispheres, telencephalon and diencephalon.<br />
<br />
Studies on Drosophila melanogaster have indicated the role of the Hedgehog signalling pathway in the activation of the EGFR pathway in Drosophila head development.<br />
<br />
This pathway also plays a significant role in the development of craniofacial features, as it contributes to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm. Blockage of Shh signalling in chick embryos provides inside into the birth defects associated with lack of Shh involvement in craniofacial development. These defects include holoprosencephaly and, cleft lip and palate.<br />
<br />
The role of Hh signalling pathway in development of spinal nerves and meninges has not been observed within animal models but as discussed above, this pathway plays a significant role in other areas of embryonic development, such as forebrain and craniofacial development, germ cell proliferation, subdivision of the eye field, production of sclerotomes and patterning of limb buds.<br />
<br />
The role of this pathway in development and patterning of limb buds and sclerotomes was observed through experimentation on Shh knockout mice. The absence of this pathway resulted in a lack of vertebral column development. This deficiency of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population. Anterior limb bud cell death was also observed in these mice, indicating the role of Shh in patterning the anterior-posterior limb axis and even the proximal-distal limb segments, particularly in patterning of structures at the level of or distal to the latent elbow and knee joints. <br />
<br />
{A patient presents with crossed eyes, a pronounced forehead and an abnormally large head. Through an ultrasound it was also revealed the patient has an ovarian fibroma. Which of the following is the patient diagnosed with?<br />
|type="[]"}<br />
- &nbsp; Holoprosencephaly<br />
- &nbsp; Medulloblastoma<br />
+ &nbsp; Gorlin Syndrome<br />
- &nbsp; Cowden Syndrome<br />
||<br> The symptoms present in the patient correlate with Gorlin Syndrome. The patient is cross-eyed due to suffering from strabismus where the eyes do not properly align with eachother. A pronounced forehead is characteristic of frontal bossing and a large head is due to macrocephaly. Macrocephaly can arise due to an enlarged brain or excessive cerebrospinal fluid in the brain. Hedgehog, as well as being a developmental morphogen, regulates the proliferation and survival of stem cell populations, explaining its involvement in development of tumours. Patients with Gorlin syndrome often develop tumours throughout the body. <br />
<br />
{Question 5<br />
|type="()"}<br />
- &nbsp; <br />
- &nbsp; <br />
- &nbsp; <br />
+ &nbsp; <br />
||Replace with Answer<br />
<br />
{Question 6<br />
|type="()"}<br />
- &nbsp; <br />
- &nbsp; <br />
- &nbsp; <br />
+ &nbsp; <br />
||Replace with Answer<br />
</quiz><br />
<br />
==Glossary==<br />
<br />
{| class="pretty table"<br />
|-<br />
|'''Term'''<br />
|'''Definition'''<br />
|-<br />
|Acyl-transferase<br />
|A protein responsible for catalyzing the transfer of a palmitic acid moiety to the N-terminus of the hedgehog signalling molecule.<br />
|-<br />
|Brother of ihog (Boi)<br />
|A surface protein that enhances hedgehog signal transduction through PTC in ''Drosophila''.<br />
|-<br />
|Casein kinase I (CKI)<br />
|A kinase that is thought to phosphorylate the Smoothened receptor to activate it in the hedgehog signalling pathway.<br />
|-<br />
|Cubitus interruptus (Ci)<br />
|A transcription factor found in the hedgehog signalling pathway of ''Drosophila'', which binds to promoter regions on the DNA in the nucleus to activate target genes of the pathway.<br />
|-<br />
|Costal-2 (Cos2)<br />
|A kinesin like protein which interacts with the C terminus of Smoothened and acts like a scaffolding protein and allows proteins such as Fused to bind to it.<br />
|-<br />
|Denticle<br />
|Bristle like projections off the segments on the ''Drosophila'' embryo.<br />
|-<br />
|Dally<br />
|An HSPG, which mediates loacalizaiton and transportation of the hedgehog protein to its targets in ''Drosophila''<br />
|-<br />
|Desert hedgehog (Dhh)<br />
|A homolog of the ''Drosophila'' hedgehog protein, which is expressed most prominently in the gonads of vertebrates, where it plays a possible role in regulating spermatogenesis. <br />
|-<br />
|Frizzled<br />
|A receptor that is part of the Wnt signalling pathway, which binds the protein wingless in order to activate signalling cascades. <br />
|-<br />
|Fused (Fu)<br />
|A kinase that binds to Costal-2 and acts to inhbit Suppressor of Fused by phosphorylating it in the hedgehog signalling pathway.<br />
|-<br />
|Gli<br />
|A family of proteins that acts as transcription factors that were originally isolated in human gliboblastoma. The proteins are important mediators in activating target genes for the hedgehog signalling pathway in vertebrates.<br />
|-<br />
|Glycipan (GPC)<br />
|A family of HSPGs which act in the hedgehog signalling pathway of vertebrates to either enhance or inhibit signal transduction depending on the isoform.<br />
|-<br />
<br />
|Hedgehog (Hh) protein<br />
|A signalling protein widely expressed in the tissue during embryonic development of vertebrates and some other species such as ''Drosophila'', and acts to pattern and develop tissue. The protein is the primary mediator of the pathway.<br />
|-<br />
|Heparin sulfate proteoglycan (HSPG)<br />
|A proteoglycan ,which is a heavily glycosolated protein, which in the context of hedgehog signalling is thought to aid in the localization and transport of hedgehog proteins to their targets.<br />
|-<br />
|Indian hedgehog (Ihh)<br />
|A signalling protein that is a homolog of the ''Drosophila'' hedgehog protein, that primarily acts in regions where there is endochondrial ossification to aid in the maturation of chondrocytes.<br />
|-<br />
|Interference hedgehog (Ihog)<br />
|A surface protein that enhances hedgehog signal transduction through PTC in ''Drosophila''.<br />
|-<br />
|Kif7<br />
|A homolog of Costal-2 in vertebrates, which acts to regulate the downstream signalling of the hedgehog pathway by causing the disassociation of SUFU and Gli.<br />
|-<br />
|Limb bud<br />
|A structure formed during early embryonic development consisting of ectoderm and mesenchyme representing the early limbs, where signalling processes in the bud will eventually lead to the out growth and patterning of the bud.<br />
|-<br />
|Patched (PTC)<br />
|Patched is a transmembrane receptor expressed on cells that are sensitive to signalling via the hedgehog pathway, where its extracellular domain binds to the hedgehog protein to inactivate it. The receptor it self without hedgehog binding actively inhibits Smoothened. <br />
|-<br />
|Primary cilia<br />
|An organelle that consists of an outward projection from the cell surface, which is thought to be critical for hedgehog signalling in vertebrates as it houses many components of the pathway. <br />
|-<br />
|Protein kinase A (PKA)<br />
|A kinase that is thought to phosphorylate the Smoothened receptor to activate it in hedgehog signalling.<br />
|-<br />
|Smoothened (SMO)<br />
|A G-protein coupled receptor like receptor integral to the hedgehog signalling pathway and acts to set in motion a series of events that lead to the activation of transcriptional factors that activate target genes of the hedgehog pathway.<br />
|-<br />
|Sonic hedgehog (Shh)<br />
|The most widely expressed homolog of the ''Drosophila'' hedgehog protein found in vertebrates, playing a key role in embryonic development of humans.<br />
|-<br />
|Suppressor of Fused (SUFU)<br />
|A protein in the hedgehog signalling pathway which when active, inhibits the translocation of Cubitus interruptus into the nucleus by leading to its phosphorylation, and eventually degradation via the proteosome.<br />
|-<br />
|Wingless protein<br />
|A protein produced as a downstream target of the hedgehog signalling pathway in ''Drosophila'', which activates the Wnt pathway by binding to the Frizzled receptor.<br />
|-<br />
|Zone of polarizing activity (ZPA)<br />
|The posterior region of the limb bud mesenchyme, which aids in the signalling of it to pattern the posterior anterior axis with respect to the digits through mediators such as sonic hedgehog.<br />
|-<br />
|}<br />
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===Additional Glossary Links===<br />
[[A|A]] | [[B|B]] | [[C|C]] | [[D|D]] | [[E|E]] | [[F|F]] | [[G|G]] | [[H|H]] | [[I|I]] | [[J|J]] | [[K|K]] | [[L|L]] | [[M|M]] | [[N|N]] | [[O|O]] | [[P|P]] | [[Q|Q]] | [[R|R]] | [[S|S]] | [[T|T]] | [[U|U]] | [[V|V]] | [[W|W]] | [[X|X]] | [[Y|Y]] | [[Z|Z]] | [[Numbers|#]]<br />
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== References ==</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=2016_Group_Project_4&diff=255220
2016 Group Project 4
2016-10-27T10:35:09Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Project2016header}}<br />
{{Group Assessment Criteria table}}<br />
<!-- Do not delete the above template from the Group project page. --><br />
<br />
= Hedgehog signalling pathway =<br />
==Introduction==<br />
[[File:Hedgehog.jpg|thumb|300px|An image of a hedgehog, the animal of which the Hh proteins are named after.]]<br />
The Hedgehog (Hh) signalling pathway is an important part of the early embryo with regards to the patterning and development of the nervous system, limbs and the cranio-facial region in vertebrates and the polarization of the segments in the ''Drosophila'' embryo. It was first identified in 1980 by Christiane Nüsslein-Volhard and Eric Wieschaus, alongside a group of other genes regulating segment polarity in ''Drosophila'' embryonic development<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. The pathway itself consists of Hh proteins, where there are three identified homologs in vertebrates, being sonic hedgehog (SHH), Indian hedgehog (IHH), and desert hedgehog (DHH) <ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. All homologs are expressed at varying levels within different tissues in the body, and also act as a form of redundancy to an extent between one another. <br />
<br />
The signaling pathway is highly conserved between various species<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. and acts via a G protein coupled receptor like receptor, which uninhibited via the action of the Hh proteins. The pathway overall acts via a balance of dephosphorylation<ref name="PMID10966113"><pubmed>10966113</pubmed></ref> and degradation of proteins<ref name="PMID15102702"><pubmed>15102702</pubmed></ref> in order to regulate transcription factor activity to express various genes to carry out its action. The Hh pathway is also highly implicated when it comes to abnormalities in development, as it is implicated in diseases such as holoprosencephaly and cleft lip and palate. Overall Hh signaling pathways play a large role in embryological development, which will be discussed in detail on this page.<br />
<br />
== History ==<br />
{| class="pretty table"<br />
| '''1980'''<br />
|Christiane Nüsslein-Volhard and Eric Wieschaus first identified a group of genes including those related to the Hedgehog signalling pathway and linked them to the segmentation and planning of the embryo in ''Drosophila melanogaster'' by introducing mutagenic substances to the developing embryo<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Multiple researchers including Andrew P. McMahon and Clifford Tabin discovered three equivalent homologs in vertebrates of the ''Drosophila melanogaster'' hedgehog gene, known as sonic hedgehog (Shh), desert hedgehog (Dhh) and indian hedgehog (Ihh), by looking at DNA sequences similar to that of the gene in the fruit fly<ref><pubmed>7916661</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Clifford Tabin and his lab identified the role of Shh in localising the limb bud, where they identified protein to be expressed within a region of the limb bud known as the zone of polarising activity (ZPA), showing that SHH is sufficient to induce the production of a ZPA, and thus limb bud formation in chick embryos<ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|Sonic hedgehog secreted by the notochord was identified to induce ventral cell types in the neural tube during embryonic development, most notably the floor plate cells and the motor neurons as shown in chick embryos. Such differentiation between the two cell types is thought to be a matter of sonic hedgehog concentrations experienced by the neural plate cells<ref name="PMID7736596"><pubmed>7736596</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|A shared Nobel prize in physiology or medicine was awarded to Christiane Nüsslein-Volhard and Eric Wieschaus for their researching regarding the identification of the developmental genes relating to the formation and patterning of the early embryo via genes.<br />
|-<br />
|'''1996'''<br />
|Studies showed that human homologs of the Patched gene, a component of the hedgehog pathway, is a key gene that is mutated in Gorlin Syndrome, which characterised by a predisposition for basal cell carcinomas, the most common cancers in humans and developmental abnormalities<ref name="PMID8658145"><pubmed>8658145 </pubmed></ref>.<br />
|-<br />
|'''1999'''<br />
|Researchers implicated Indian hedgehog as a key signalling molecule for the maturation and differentiation of prehypertrophic chondrocytes, where Indian hedgehog null mice were shown to have a lack of mature chondrocytes and no development of osteoblast cells in endochondrial bone. This was thought to be due to Indian hedgehog having a feedback signal controlling parathyroid hormone related protein, which regulates endochondrial bone development<ref name="PMID10465785"><pubmed>10465785</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Sonic hedgehog was identified to regulate the proliferation of adult neural stem cells as shown in the hippocampus of rats and in vitro for neural progenitor cells isolated from the hippocampus<ref name="PMID12469128"><pubmed>12469128</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Studies on Shh function found that it can act as a chemoattractant in the developing embryo spinal cord, to help guide commissural axons to the midline of the floor plate<ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
|-<br />
|'''2009'''<br />
|Mouse models showed that reduction in hedgehog signalling allows for transient improved response to chemotherapy with regards to mouse models of human pancreatic ductal adenocarcinoma, a cancer with one of the highest mortality rates in humans<ref name="PMID19460966"><pubmed>19460966</pubmed></ref>.<br />
|}<br />
<br />
This time line regarding the discoveries in the hedgehog signalling pathway is by no means exhaustive, but a selection of relatively large discoveries that had a significant impact in the field on the basis of citations.<br />
<br />
== Origin of name ==<br />
<br />
[[File:Bands of denticles in normal and Hh mutant Drosophila embryo.jpeg|thumb|250px|Differences in patterning of the denticle bands in normal and mutated hedgehog gene variant ''Drosophilia'' embryo]]<br />
<br />
The name hedgehog came about when Christiane Nüsslein-Volhard and Eric Wieschaus first identified the group of genes controlling polarization of the segments in the ''Drosophila'' early embryo. They noticed that when they mutated the Hh gene, making it non-functional, that the bands of denticles formed during the early ''Drosophila'' embryo formation became more diffuse as opposed to being distinct normally. The denticles would all clump together forming a single patch on the surface of the embryo, as opposed to normally outlining the distinct segments of the embryo as bands<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. This gave the embryo spiny and prickly look similar to that of the back of a hedgehog.<br />
<br />
From there on in the gene was called the hedgehog gene where homologs in vertebrates discovered along the line kept to this naming structure giving various species of hedgehog names to the genes such as Indian hedgehog, and desert hedgehog, with the exception being sonic hedgehog, which is named after a fictional character in the video game “Sonic the Hedgehog”.<br />
<br />
== Mechanism of signalling ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br>[[File:Hh signalling pathway.jpg|thumb|600px|Diagrammatic representation of the steps and components involved in the hedgehog signalling pathway in both ''Drosophila'' and mammals.]]<br />
<br />
The Hh signaling pathway has been well studied in ''Drosophila melanogaster'', and has been shown the be conserved to an extent across it and mammals making the species a suitable model for Hh signalling in humans<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. In ''Drosophila melanogaster'', the Hh pathway begins when the Hh proteins bind to the extracellular domain of the transmembrane protein known as Patched (PTC). Such binding is thought to be greatly enhanced by the presence of proteins known as interference hedgehog (ihog) and brother of ihog (boi), which have shown to be essential to allowing hedgehog binding to inactivate PTC<ref name="p20048000 "><pubmed>20048000 </pubmed></ref>. It has also been demonstrated heparin sulfate proteoglycans (HSPG) such as dally also aid in the modulation of hedgehog signalling, where they act to localise and transport the hedgehog protein to the target receptors<ref name="p14602684"><pubmed>14602684</pubmed></ref> <ref name="p10549295"><pubmed>10549295</pubmed></ref>. Overall hedgehog binding leads to inactivation of PTC which occurs by Hh trapping PTC in an inactive conformational state<ref><pubmed>27647915</pubmed></ref>. After binding of Hh occurs to PTC and it is inactivated, the receptor and Hh protein is thought to be endocytosed by the cell where they undergo lysosomal degradation in order to limit Hh concentration, thus limiting its spread to other cells and PTC activity<ref name="PMID15102702"><pubmed>15102702</pubmed></ref>. In the absence of Hh, PTC acts to suppress the expression of the Smoothened (SMO), a G-protein coupled receptor like receptor, and thus its signaling. How PTC achieves this inhibition of SMO is currently unclear. Studies have suggested that due to the highly phosphorylated nature of SMO when active, that PTC acts to dephosphorylate SMO in order to repress its signaling. It is thus that binding of Hh to PTC reduces PTCs ability to promote dephosphorylation of SMO, leading to its increased activity and expression on the cell surface <ref name="PMID10966113"><pubmed>10966113</pubmed></ref>. It is thought that the phosphorylation required to activate SMO are dependent on protein kinase A (PKA) and casein kinase I (CKI) <ref><pubmed>15616566 </pubmed></ref>.<br />
<br />
This overall increased phosphorylation of SMO due to a repression of PTC activity by Hh leads to an accumulation of SMO on the cell surface, which collectively allows for SMO to exert its activity. Importantly the phosphorylation also disrupts intramolecular electrostatic interactions between SMO molecules which switches the molecule into its active conformational state <ref><pubmed>17960137 </pubmed></ref>. Generally, SMO has been shown to have very little signal transducing ability, and thus this accumulation allows it to jointly transduce a substantial signal. This occurs by the C terminus of SMO on the intracellular domain interacting with the kinesin like protein Costal-2 (Cos2), which is thought to bind to microtubules in order to acts as a scaffolding protein <ref><pubmed>18691888 </pubmed></ref>. Such interactions induce the formation of a complex including the kinase known as Fused (Fu) and Cos2, which phosphorylates Suppressor of Fused (SUFU) to inhibit it. Without this inhibition SUFU goes onto prevent the translocation of the transcriptional factor Cubitus interruptus (Ci) into the nucleus by leading to its phosphorylation, and subsequently its partial cleavage via the proteosome. The partial cleavage of Ci leaves a lower molecular weight protein known as Ci repressor (CiR) or Ci75, which translocates into the nucleus and acts to repress the target genes of the Hh signalling pathway via Ci<ref><pubmed>9215627</pubmed></ref>. Thus overall inhibition of SUFU increases the amount of Ci entering into the nucleus of the cell, and activating transcription of target genes of the Hh pathway<ref><pubmed>10952898 </pubmed></ref>. Activation of SMO also promotes disassociation of present SUFU-Fu-Cos2-Ci complex which which generally when fully intact leads to cleavage of Ci into its repressor form<ref name="p15063184"><pubmed>15063184</pubmed></ref><ref name="p17881487"><pubmed>17881487</pubmed></ref>.<br />
<br />
At this point Ci is able to activate the transcription of various genes, which include importantly the ''ptc'' gene, which encodes the PTC receptor. It is thus as a result of this, that PTC expression will be increased in response to Hh pathway induction, which negatively feeds back to reduce Ci signaling induction, in order to maintain homeostasis and regulate the intensity and duration of the signaling from Hh<ref><pubmed>9053330</pubmed></ref>. Furthermore the ''wg'' gene, encoding the wingless protein is also activated by Ci, which leads to activation of the Wnt pathway via the Frizzled receptor in adjacent cells expressing the gene ''engrailed'' <ref><pubmed>9502727</pubmed></ref> <ref><pubmed>10457026</pubmed></ref>. This overall stabalizes the boundaries between the segments of the developing ''Drosophila melanogaster'' signalled by the gene ''engrailed''<ref><pubmed>3282172</pubmed></ref>.<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=w1xXD9kss2w</html5media><br />
<br><br><br />
An overview of the hedgehog signalling pathway in ''Drosophila''<ref>YouTube. (2016). The Hedgehog signalling pathway in Drosophila online Available at: https://www.youtube.com/watch?v=w1xXD9kss2w</ref>.<br />
<br />
=== Mammals ===<br />
<br />
Although the Hh signaling pathway has been conserved across species to an extent <ref name="PMID8595881"><pubmed>8595881</pubmed></ref>, key differences exist when observing the pathway within mammalian tissue in contrast to that which has been studied in ''Drosophila melanogaster''. In mammalian cells and all other vertebrates, Hh signalling is dependent on an organelle known as the primary cilia, which are projections outwards from the cells surface. The importance of such an organelle in the signalling pathway comes as a result of PTC1, one of the two PTC receptor homologs in mammals, that binds to the Hh homolog Sonic Hh (Shh), exists within the cilia<ref><pubmed>17641202</pubmed></ref>. Similarities also exist between signalling in the vertebrates and ''Drosophila''. This includes the surface proteins such as Cdo and Brother of cdo (Boc), which act in a similar fashion to ihog and boi in enhancing the binding of the hedgehog protein to PTC<ref><pubmed>16647304</pubmed></ref>. HSPGs such as gylcipans (GPC) 1, 2, 3, 4, 5 and 6 are also thought to play a role in hedgehog signalling in vertebrates with regards to stimulaiton or inhibition of the pathway depending on the isoform<ref><pubmed>26627558</pubmed></ref>. The mechanism of action of SMO inhibition and activation is poorly understood currently, but evidence has suggested that PTC1 acts to inhibit SMO when unbound to Shh by acting as a pump to remove oxysterols from the cilia into the extracellular space<ref><pubmed>PMC1462959</pubmed></ref>. These oxysterols are normally thought to bind and accumulate around the SMO receptors, which in turn prevents internalization and deactivation of SMO, leading to it accumulating on the apical primary cilia<ref><pubmed>16136078</pubmed></ref>. Other studies have also suggested that Shh has a role in increasing phosphorylation of SMO via kinases such as CK1, which causes it to accumulate on the cilia<ref><pubmed>21695114</pubmed></ref>. Overall the net action of Shh initially is believed to cause accumulation of SMO at the cilia by inhibiting PTCH1 and phosphorylation of SMO.<br />
<br />
How SMO acts next is relatively unknown but, it has been shown to promote the disassociation between SUFU and Gli transcription factor, which allows Gli to be transported to the nucleus to activate effector genes of the pathway. Gli is normally bound in the cytoplasm to SUFU, where SUFU promotes the partial degradation of Gli into its repressor form, similar to that in the fruit fly model<ref><pubmed>20360384</pubmed></ref>. Alongside this, Kif7, a Cos2 homolog, has been shown to migrate to the apex of the cilium in response to SMO accumulation at the cilium, where it has been postulated to also promote disassociation of SUFU and Gli<ref><pubmed>19592253</pubmed></ref>. On the other hand, Kif7 is also thought to play an inhibitory role for the signalling pathway as when it is localized at the base of the cilia in the absence of Hh signaling, where it acts to traffic Gli transcription factors away from the cilia<ref><pubmed>19666503</pubmed></ref>. This all leads to an accumulation of active Gli transcription factors which migrate to the nucleus in order either inhibit or activate gene transcription in response to Hh signaling. These Gli transcription factors include Gli1, Gli2, and Gli3, where Gli2 and Gli3 in their activated form are the primary mediators of the pathway, and also act to repress the target genes when hedgehog signalling is absent. Gli3 is considered to be the major repressor of the pathway when the full length version of the Gli3 protein is partially cleaved into its repressor form <ref><pubmed>10433919</pubmed></ref>. Gli1 on the other hand is one of the targets of hedgehog signalling promoted by Gli2 and Gli3 activators, and acts to reinforce the hedgehog pathway through a positive feedback loop <ref><pubmed>10075717</pubmed></ref>. As a result Gl1 is considered as not entirely essential ,where mice models with no production of Gl1 have shown viability with few defects<ref><pubmed>10725236</pubmed></ref>. That being said, other studies have shown the importance of Gl1 as a downstream target of sonic hedgehog, where it is thought to induce ventral neural tube development, as it is on the only Gli factor present in the floor plate during gastrulation<ref><pubmed>9216996</pubmed></ref>. Overall the interactions between such transcription factors are still relatively unknown, where further research is required to elaborate on the specific roles in the hedgehog pathway they each have.<br />
<br />
== Function ==<br />
===Overview===<br />
{| class="pretty table"<br />
|'''Hedgehog protein homolog'''<br />
|'''Function'''<br />
|-<br />
| Sonic hedgehog [http://www.omim.org/entry/600725 OMIM entry] ||<br />
*Expressed in zone of polarizing activity of the limb bud where it plays a role in helping to pattern the anterior and posterior aspect of the limbs <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
*Based on time and concentration of SHH due to diffusion from the point of secretion in the limb bud, SHH also plays a role in determining digit identity <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>.<br />
*Acts as a chemoattractant to guide commissural axons in the floor plate of the neural tube towards the midline <ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
*Patterns the developing cusps of the teeth and their relative positions in the jaw, and is also essential for the growth of the teeth <ref name="PMID11044393"><pubmed>11044393</pubmed></ref>.<br />
*SHH released from the notochord acts to induce formation of the floor plate, motor neurons, and dopaminergic neurons, as well as signalling the induction of the ventral cell types in the neural tube <ref name="PMID8790332"><pubmed>8790332</pubmed></ref>.<br />
|-<br />
| Desert hedgehog [http://www.omim.org/entry/605423 OMIM entry]||<br />
*Plays a possible role in regulating spermatogenesis as due to the highly localised expression in the testes by pre-Sertoli cells, and the fact that mice with no DHH present are infertile, with no mature spermatozoa <ref name="PMID8805249"><pubmed>8805249</pubmed></ref>. <br />
*DHH derived from Schwann cells signal development of peripheral nerves, by inducing the production of a connective tissue sheath around them <ref name="PMID10482238"><pubmed>10482238</pubmed></ref>.<br />
|-<br />
| Indian hedgehog [http://www.omim.org/entry/600726 OMIM entry]||<br />
*Aid in the signalling of proliferating chondrocytes to undergo hypertrophic differentiation during endochondral ossification<ref name="PMID8662546"><pubmed> 8662546</pubmed></ref>.<br />
*Plays a key role in yolk sac angiogenesis, as seen in studies where an absence of IHH leads to death of the embryo due to poor yolk sac vasculature <ref name="PMID11807029"><pubmed>11807029</pubmed></ref>.<br />
|}<br />
<br />
===Limb development===<br />
<br />
====Research background====<br />
<br />
The hedgehog signalling pathway plays a significant role with regards to the embryonic development of the limbs in vertebrates, specifically SHH. For a while the mechanism of which the limb was patterned on the anterior to posterior axis was quite unknown. Early studies had shown that grafting posterior wing bud cells to the anterior region of the wing bud in a chick embryo, an equal amount of extra digits was produced to that of which was normally produced, and in a mirror image pattern<ref name="PMID4390734"><pubmed>4390734</pubmed></ref>. This showed that the pattern of which the digits were produced were polarized with respect to that of the graft from the limb bud, which has become to be described as the zone of polarizing activity (ZPA). Further studies mapped the ZPA, by showing the area of the wing bud on the chick with the highest polarizing activity to be the posterior margin of the wing bud<ref name="PMID4719010"><pubmed>4719010</pubmed></ref>. Furthermore, studies later on found that the amount or concentration of ZPA cells grafted played a role in the amount of digits induced and how polarized they were<ref name="PMID7453825"><pubmed>7453825</pubmed></ref>. This ultimately gave rise to studies regarding a potential morphogen, which could potentially provide this concentration dependent activity of polarization when it comes to the limb bud. Studies to find this morphogen led to the discover of the ability for retinoic acid to mimic the polarizing action of the ZPA when applied locally to the limb bud<ref name="PMID7070499"><pubmed>7070499</pubmed></ref>. This was found to be due to the induction of a second morphogen known as SHH, where when cells that express SHH are grafted onto the limb bud, polarized digit development is induced<ref name="PMID7720566"><pubmed>7720566</pubmed></ref>.<br />
<br />
====Polarizing activity of sonic hedgehog====<br />
[[File: Mechanims of patterning the digits on the posterior to anterior axis of the limb bud by sonic hedgehog.jpg|thumb|450px|Regions of the limb bud and the digits they form based on patterning of the posterior to anterior axis of the limb bud by mechanisms mediated by sonic hedgehog.]]<br />
More recent studies have sought to elucidate how SHH mediates such a polarizing effect in terms of digit identification and its underlying mechanism. It has been suggested that such an effect is heavily concentration dependent similar to that of when transplanting the chick wing bud ZPA cells, acting in a dose dependent matter, due to the ability of SHH to modulate signaling at long ranges via diffusion<ref name="PMID11389830"><pubmed>11389830</pubmed></ref>. This implies that a gradient of varying concentrations of SHH diffused through the mesenchyme of the limb bud leads to the identification of posterior and anterior digits.<br />
<br />
Current research has also suggested that not only is the concentration gradient of SHH important for the patterning of the digits, but also the temporal gradient, being the length of time of exposure of SHH to the mesenchyme of the limb bud. Studies have shown in mice that of the 5 digits, polarization from the posterior end, being digit 5, to the anterior end being digit 1 are due to different mechanisms. Digits 5 and 4 have been shown to be comprised of the SHH expressing cells and thus both experience maximal levels of SHH, and thus cannot be distinguished on the basis of a concentration gradient. As a result, temporal gradients are employed, where the expression of SHH in both regions that become the digits vary, where studies have shown that SHH expression in the primordium of digit 5 is maintained longer than that in digit 4 gradient <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>. When it comes to digit 3 and 2, there is differentiation based on the concentration gradient of SHH from the ZPA, where due to the ZPA being further away to digit 2 than 3, the concentration of SHH will be higher at 3<ref name="PMID15315763"><pubmed>15315763</pubmed></ref> <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>. In terms of digit 1, the levels of SHH are so low at this point that it is said to be SHH independent, and actually reliant on the absence of SHH for normal differentiation. With regards to how SHH actually mediates its action, it is thought to be by a balance between the transcription factor Gli3 and SHH expression, which activates Gli1, Gli2 and Gli3 repressor, effectively counteracting Gli3. Gli3 is considered to promote the inhibition of digit formation and identification, while the downstream targets of SHH are thought to promote it<ref name="PMID17400206"><pubmed>17400206</pubmed></ref>.<br />
<br />
Other research has also shown the possibility of SHH signaling as a way to prime the posterior mesenchyme and induce the production of bone morphogenetic protein 2 (bmp2), which is thought to be the morphogen creating the chemical gradient for digit identification<ref name="PMID10704381"><pubmed>10704381</pubmed></ref>. Overall the mechanism at which SHH work to pattern the posterior anterior axis of the limb bud is still relatively unknown, and further research is being conducted to elucidate how the underlying mechanisms such as the downstream targets of SHH affect digit formation.<br />
<br />
=== Neural development ===<br />
<br />
====Research background====<br />
Research on the role of the notochord, a cartilaginous structure derived from the mesoderm, initially observed its ability to induce the floor plate within the neural tube of chick embryos<ref name="PMID3354847"><pubmed>3354847</pubmed></ref>. This induction of a floor plate occurred in the ventral midline of the neural tube, where the floor plate itself is thought to have signalling effects regarding patterning of the spinal cord. Alongside this, research also noted that the floor plate and notochord collectively had signalling effects that patterned the differentiation of the neural cells in the neural tube<ref name="PMID1991324"><pubmed>1991324</pubmed></ref>. Such observations lead to research being directed at how this patterning of the neural tube is mediated through the notochord. It had been suggested that the morphogen known as Shh was to play due to its high expression within the notochord and floor plate. It also was showed to activate floor plate expressed genes when ectopically expressed in the mouse CNS<ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. Furthermore, observations regarding the Shh also lead to implicating it in the differentiation of distinct cell types in the ventral neural tube such as motor neurons, alongside the already identified floor plate<ref name="PMID8124714"><pubmed>8124714</pubmed></ref>. Studies looking specifically at the targets of Shh signalling in the neural tube also identified that using antibodies to block the protein would lead to blocking of the induction of the motor neurons, and that applying Shh to explants induced floor plate and motor neurons in a variety of vertebrate models<ref name="PMID7753196 "><pubmed>7753196 </pubmed></ref>. This for the most part formed the basis of research on the specific patterning effects of Shh secreted from the notochord and floor plate on the ventral neural tube.<br />
<br />
====Patterning of ventral nerve cell types in the neural tube====<br />
As stated, the inductive signals from the notochord in the form of Shh <ref name="PMID7753196"><pubmed>7753196 </pubmed></ref> are primarily responsible for the formation of the floor plate in the ventral midline of the neural tube during embryonic development<ref name="PMID3354847"><pubmed>3354847</pubmed></ref>. The floor plate itself acts in the same fashion as the notochord with regards to expression of Shh for mediatating its signal. Collectively it is thought that the notochord and the floor plate provide a Shh graded response, where there is a gradient of concentrations along the dorsoventral axis of the developing neural tube<ref name="PMID9598380"><pubmed>9598380</pubmed></ref>. As a result, it is believed that the degree of Hh signalling on a cell type is responsible for the differentiation of progenitor cells it to various types. Specifically, with regards to the floor plate, the distinct local signal, given the close proximity of the notochord to the floor plate induction site is responsible for inducing the floor plate<ref name="PMID9598380"><pubmed>9598380</pubmed></ref>. It is thought that through interacting with the receptor PTC, the pathway activates the transcription of hepatocyte nuclear factor 3β (HNF-3β), a gene that has been shown to be commonly expressed in the floor plate. Such a gene is activated by the transcription factors Gli1 and Gli2. Thus HNF-3β is considered to be the downstream target of Shh signalling leading to the induction of the floor plate<ref name="PMID9118802"><pubmed>9118802</pubmed></ref>. It is also believed that HNF-3β is essential for notochord formation as well, as seen in mice models with HNF-3β knocked out, leading to dorsoventral patterning issues<ref name="PMID8069909"><pubmed>8069909</pubmed></ref>. Overall the induced floor plate acts to further aid the notochord in producing a graded Shh response to pattern the ventral neural tube<ref name="PMID1991324"><pubmed>1991324</pubmed></ref>.<br />
<br />
=== Organogenesis ===<br />
The Hedgehog Signalling pathway is a pathway sending information to embryonic cells which plays an especially important role in the regulation of organogenesis. These processes include the organization of the brain (craniofacial) and the growth of appendages with further studies implicating the Hedgehog Signalling pathway in the development of the small intestine, lungs and the pancreas.<br />
<br />
== Animal models ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br>[[File:Hedgehog signalling on plane polarity of denticles in Drosophila.png|thumb|400px|Image of denticles on the ''drosophila'' embryo used as a model to research plane polarization of cells by looking at the orientation of the denticles on the ''drosophila'' embryo in response to many signalling molecules including hedgehog.]]<br />
<br />
Hedgehog (Hh) protein signal was initially discovered through experimentation on the fruit fly, "Drosophila melanogaster". It is through this model that we are able to discover not only the functional components of this pathway but also understand its role in embryonic development. Through application of this information on the human biological system we are able to find the cause and thus potential treatments of defects and diseases caused by interruption or mutation of the Hedgehog signalling pathway. <br />
<br />
Upon further research on Drosophila it was found that Hh may play a role in germ cell proliferation and in particular, may control the proliferation and activity of somatic cells found within the germarium, which is the most anterior structure within the Drosophila ovary. <ref>Ovaries (Drosophila) definition. (2016). Groups.molbiosci.northwestern.edu. Retrieved 10 September 2016, from http://groups.molbiosci.northwestern.edu/holmgren/Glossary/Definitions/Def-D/Drosophila_Ovaries.html</ref> Thus, the Hh signalling pathway is vital in egg chamber formation and its consequent envelopment, budding and polarisation. It has also been observed that somatic cell proliferation is dependent on this pathway and thus, the number of pre-follicle cells is subject to the effect of the Hh signalling pathway. <ref><pubmed>8620839</pubmed></ref> Further studies have also indicated the role played by this pathway in activating the Epidermal growth factor receptor (EGFR) signalling pathway as seen in the induction of EGFR by Hh in Drosophila head development. <ref><pubmed>10331974</pubmed></ref> In addition, research on Drosophila has indicated the direct effect of Hh signalling on tracheal branch patterning. <ref><pubmed>11290298</pubmed></ref><br />
<br />
Despite ongoing research on "Drosophila melanogaster" to uncover the workings of the Hedgehog signalling pathway, further research is needed to confirm and further current findings. In addition, it is evident that it is through the study of these fruit flies that we are able to gain a basis of understanding of the causes of certain human diseases and thus propel research into treatments for sufferers.<br />
<br />
===Blockage of Shh Signalling in Forebrain Neuroectoderm of Chick Embryos===<br />
<br />
The Hedgehog signalling pathway plays a significant role in embryonic development, particularly of the forebrain. Due to its role in development of craniofacial features by contributing to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm, a disruption in this pathway can result in a variety of birth deformities including holoprosencephaly (HPE), where the prosencephalon (forebrain) fails to divide into 2 separate hemispheres, telencephalon and diencephalon <ref>Holoprosencephaly - NORD (National Organization for Rare Disorders). (2016). NORD (National Organization for Rare Disorders). Retrieved 10 September 2016, from http://rarediseases.org/rare-diseases/holoprosencephaly/</ref>, as well as cleft lip and palate. The function of Sonic Hedgehog (Shh) and its signalling pathway on the formation of forebrain neuroectoderm was studied in chick embryos.<br />
<br />
It was found that the disruption of Shh signalling in the neural tube of chick embryos resulted in the lack of division of the forebrain into the diencephalon and telencephalon. This is in fact, as stated earlier, the fundamental cause of the rare condition, holoprosencephaly. It was discovered that the Shh signalling pathway in the diencephalon was responsible for gene expression in the telencephalon. <br />
<br />
In addition, through experimentation on chick embryos it was found that through Shh signalling the development of the forebrain regulates and controls facial morphogenesis, particularly of the upper and middle face. Therefore, interference with Shh signalling in the forebrain prevents this intrinsic communication, thus hindering Shh expression in facial ectoderm. This results in brain malformation accompanied by facial disfiguration as seen in patients suffering from HPE. Other malformations caused by blockage of Shh signalling in craniofacial development include, hypotelorism (decreased space between the orbits), growth restriction as well as cleft lip and palate as mentioned previously. <br />
<br />
A commonality discovered among all forms of Shh signalling disruption was two facial defects, “the loss of mediolateral expansion of the face and absence of proximodistal outgrowth of the frontonasal prominence”<ref><pubmed>15979605</pubmed></ref> (Ralph et al., 2005). Through reference to studies performed on chick and mice embryos, it was found that Shh signalling is particularly vital in development of maxillary and frontonasal components of the cranium.<br />
<br />
This breakthrough study on the inhibition of Shh signalling in chick embryos has significantly filled the gap in our understanding of the Sonic Hedgehog signalling pathway. It is evident that this pathway is crucial in the development of the forebrain and in turn regulates and controls the development of the facial skeleton. This is further proven through the observation that in the event of Shh signalling inhibition there is a development of craniofacial malformations.<br />
<br />
=== Shh knockout mice ===<br />
<br />
Extensive research on Shh knockout mice allowed discovery of the roles of Shh in embryonic development and patterning of the limb buds and sclerotomes, and maintenance of the notochord. <ref><pubmed>8837770</pubmed></ref> These mice expressed defects in the cephalic neural tube with the fusion of telencephalic and optic vesicles. Through this research it is evident that Shh is partially responsible for the subdivision of the eye field through forebrain optic stalk development, along with formation of the ventral midline. It is these forebrain abnormalities established in the absence of Shh that results in congenital malformations of holoprosencephaly, development of a single nasal chamber and other facial defects in humans. <br />
<br />
The absence of the vertebral column including, the intervertebral discs and vertebrae along with the medial regions of the ribs were observed within Shh knockout mice. This lack of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population (Chiang et al., 1996). In addition, though the role of Shh in patterning the anterior-posterior limb axis is evident through anterior limb bud cell death in the absence of Shh, it is also responsible for the development of proximal-distal limb segments, particularly in the patterning of structures at the level of or distal to the latent elbow and knee joints. <ref><pubmed>11476582</pubmed></ref> This was perceived after observing the incomplete formation of distal limb structures with abnormal anterior-posterior axis formation (Chiang et al., 2001). Thus, Shh knockout mice provide great insight into the functions of Shh in embryonic development and the abnormalities formed in the absence of this signalling protein. <br />
<br />
== Clinical Significance ==<br />
<br />
===Gorlin Syndrome===<br />
[[File:1 week year old newborn girl with cleft lip and palate.png|thumb|An image of a 1 week year old newborn girl with cleft lip and palate]]<br />
Gorlin syndrome, also known as nevoid basal cell carcinoma syndrome, is a heritable disease resulting from heterozygousity in Hh receptor, Patched (PTC). The PTC gene encodes a protein which binds sonic hedgehog (Shh) and it is this binding which inhibits the Hh signalling pathway. However mutation of PTC leads to activation of the pathway <ref><pubmed>9620294</pubmed></ref>. The syndrome is characteristic of skin cancer basal cell carcinoma and cerebellum cancer medulloblastoma. 1-2% of medulloblastomas and 0.5% of basal cell carcinomas are attributable to the disease. Patients present with craniofacial and brain abnormalities such as cleft palate, strabismus, macrocephaly, abnormal development of the corpus callosum and frontal bossing, with an overall overgrown appearance. Skeletal defects such as of the shoulder, ribs and vertebrae are often seen, as well immobile thumbs and polydactyly, which is a deformity of the hand or feet in which they have one or more extra fingers or toes. Apart from physical anomalies, patients have an increased risk of tumours throughout the body including cardiac, ovarian fibromas, ovarian dermoid cysts, meningiomas, and fibrosarcomas. Additionally with time, patients eventually undergo intracranial calcification and dyskeratotic pitting of the hands and feet whereby skin cells prematurely convert to keratin <ref><pubmed>8681379</pubmed></ref>.<br />
<br />
===Holoprosencephaly===<br />
<br>[[File:Semilobar holoprosencephaly.jpg|thumb|240px|MRI of fore brain depicting semilobar holoprosencephaly]]<br />
Holoprosencephaly (HPE) is a congenital disease caused by incomplete division of the prosencephalon (embryonic forebrain) into separate lobes of the cerebral hemispheres. The Shh gene has been identified as a HPE-causing gene however recent evidence has also investigated into the PTC gene, which acts to repress Shh signalling. A gain in repressive action of PTC is seen, leading to decreased Shh signalling, and thus HPE <ref><pubmed>11941477</pubmed></ref>. Clinical expression is variable between patients and is dependent upon the 3 forms of increasing severity: lobar, semi-lobar and alobar HPE, where patients can present with right and left ventricles however with a continuous frontal cortex in lobar HPE, to carrying a single cerebral ventricle in alobar HPE. Along with forebrain abnormalities, facial anomalies are also seen including midline cleft lip and/or flat nose, ocular hypotelorism characteristic of a small distance between the eyes. In severe rare cases of cyclopia, a non-functioning nose may be observed in the form of proboscis and the patient may present with a single eye at the root of the nose <ref><pubmed>20583177</pubmed></ref>. Furthermore, patients with HPE often develop a large number of medical issues including epilepsy, mental retardation, thyroid and adrenal hypoplasia due to lack of hypothalamus or pituitary gland development, and diabetes insipidus.<br />
<br />
===Medulloblastoma===<br />
Medulloblastoma is a cancerous tumour of the cerebellum where the cells of origin are the granular cell precursors found in the neonatal cerebellum, explaining its high prevalence in children <ref><pubmed>19171780</pubmed></ref>. Commonly, medulloblastomas are found deep in the cerebellum along the midline, however with desmoplastic medulloblastomas, they are found more laterally and superficial. As seen previously with Gorlin syndrome and holoprosencephaly, PTC is also associated with the development of medulloblastoma, and misregulation of Hh-PTC signalling in cells of the external germinal layer, the layer found on the surface of the cerebellum, is thought to give rise to the tumour. In experimental studies, it has been discovered that PTC is highly transcribed in medulloblastomas and in approximately 30% of PTC heterozygous mice the tumour develops <ref><pubmed>9205058</pubmed></ref> <ref><pubmed>9262482</pubmed></ref>. In patients with medulloblastoma, often children, the most common symptoms seen are vomiting, ataxia, psychomotor regression, drowsiness and anorexia. With age, patients are seen to get more frequent headaches, and show psychological symptoms such as behavioural problems, poor performance in school, and anxiety. In patients exhibiting life-threatening symptoms due to increased intracranial hypertension, bradycardia, convulsions and coma are often seen <ref><pubmed>21537925</pubmed></ref>.<br />
<br />
Watch below for a breakdown on Hedgehog's role in Tumour Development!<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=gFWO3I-oqsE</html5media><br />
<br><br><br />
An overview of the Hedgehog Signalling Pathway in Tumour Development<ref>YouTube. (2016). The Hedgehog Signaling in the Tumor Microenvironment - Research Hedgehog online Available at: https://www.youtube.com/watch?v=gFWO3I-oqsE</ref>.<br />
<br />
<br />
<br />
== Current research ==<br />
<br />
==Quiz==<br />
<br />
<quiz display=simple><br />
<br />
{Which of the following are the reasons that are thought to allow for the patterning of digits in vertebrates.<br />
|type="[]"}<br />
+ &nbsp;Concentration gradient of sonic hedgehog.<br />
+ &nbsp;Temporal gradient of sonic hedgehog.<br />
- &nbsp;The varying homologs of the hedgehog proteins .<br />
- &nbsp;The length of the hedgehog molecule.<br />
+ &nbsp;No sonic hedgehog signalling.<br />
- &nbsp;The type of cholesterol attached to the hedgehog molecule.<br />
||<br> For differentiation of the individual digits in mice to occur it is thought that each digit requires a different signalling mechanism. Digits 5 and 4 which are most posterior, are derived from the region around the zone of polarising area which contain Shh secreting cells, meaning these regions will experience a saturation of Shh signalling and cannot be differentiated by Shh concentration. As a result it is thought that these digits are identfied based on the temporal gradient, meaning that the length of which Shh is expressed in these regions differentiates the digits from one another with digit 5 expressing Shh for longer. Digits 3 and 2 are further away but still receive Shh signalling due to the diffusible nature of Shh from the ZPA, which forms a concentration gradient. This means the the concentration at digit 2 will be less than digit 3 due to being further away from the ZPA and thus can be differentiated from one another based on this concentration. Finally the digit 1 is differentiated on the basis of not receiving any Shh signalling at all. Thus it is a combination of concentration gradient of Shh, temporal gradient of Shh, and independence from Shh.<br />
<br />
{Which of the following are correct with regards to the hedgehog signalling pathway in ''Drosophila''.<br />
|type="[]"}<br />
-&nbsp;It occurs at the cillum on the cell surface.<br />
-&nbsp;Hedgehog protein binding to the Patched receptor activates it to inhibit Smoothened.<br />
+&nbsp;Hedgehog protein binding to the Patched recetpor inhibits it to activate Smoothened. <br />
+&nbsp;Inhibition of SUFU is critical in allowing Ci to translocate into the nucles and activate downstream targets of the hedgehog pathway.<br />
-&nbsp;The pathway contains 3 homologs including sonic hedgehog, Indian hedgehog, and desert hedgehog.<br />
-&nbsp;The hedgehog protein is initially produced in its fully active form.<br />
||<br> In terms of how the hedgehog protein acts to produce its effect, it must first bind to Patched which activity is inhibiting Smoothened in the absence of the hedgehog protein. The protein acts to trap Patched in its inactive confirmational state cause internalisation and eventually degradation of the receptor. This relives the dephosporylation of the Smoothened, usually induced by Patched, allowing it to accumulate phosphate groups and thus activate. With regards to Ci translocation, SUFU usually inhibits this by leading to phosphorylation of Ci and eventually its cleavage into Ci repressor. During the activation of the hedgehog pathway there is a binding of Fused to Cos2 which phosphorylates SUFU to inactivate it, allowing Ci to translocate into the nucleus and activate downstream targets.<br />
<br />
{What are some of the roles of the Hedgehog signalling pathway in embryonic development as discovered through animal models? (select one or more options)<br />
|type="[]"}<br />
- &nbsp; Development of the hindbrain <br />
+ &nbsp; Activates the Epidermal growth factor receptor (EGFR) signalling pathway<br />
+ &nbsp; Development of craniofacial features<br />
- &nbsp; Development of the spinal nerves and meninges<br />
+ &nbsp; Development and patterning of the limb buds and sclerotomes<br />
||<br> The Hedgehog signalling pathway plays a significant role in forebrain, not hindbrain, development. Absence of this pathway results in holoprosencephaly (HPE), the lack of division of the forebrain into its 2 separate hemispheres, telencephalon and diencephalon.<br />
<br />
Studies on Drosophila melanogaster have indicated the role of the Hedgehog signalling pathway in the activation of the EGFR pathway in Drosophila head development.<br />
<br />
This pathway also plays a significant role in the development of craniofacial features, as it contributes to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm. Blockage of Shh signalling in chick embryos provides inside into the birth defects associated with lack of Shh involvement in craniofacial development. These defects include holoprosencephaly and, cleft lip and palate.<br />
<br />
The role of Hh signalling pathway in development of spinal nerves and meninges has not been observed within animal models but as discussed above, this pathway plays a significant role in other areas of embryonic development, such as forebrain and craniofacial development, germ cell proliferation, subdivision of the eye field, production of sclerotomes and patterning of limb buds.<br />
<br />
The role of this pathway in development and patterning of limb buds and sclerotomes was observed through experimentation on Shh knockout mice. The absence of this pathway resulted in a lack of vertebral column development. This deficiency of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population. Anterior limb bud cell death was also observed in these mice, indicating the role of Shh in patterning the anterior-posterior limb axis and even the proximal-distal limb segments, particularly in patterning of structures at the level of or distal to the latent elbow and knee joints. <br />
<br />
{A patient presents with crossed eyes, a pronounced forehead and an abnormally large head. Through an ultrasound it was also revealed the patient has an ovarian fibroma. Which of the following is the patient diagnosed with?<br />
|type="()"}<br />
- &nbsp; Holoprosencephaly<br />
- &nbsp; Medulloblastoma<br />
+ &nbsp; Gorlin Syndrome<br />
- &nbsp; Cowden Syndrome<br />
||<br> The symptoms present in the patient correlate with Gorlin Syndrome. The patient is cross-eyed due to suffering from strabismus where the eyes do not properly align with eachother. A pronounced forehead is characteristic of frontal bossing and a large head is due to macrocephaly. Macrocephaly can arise due to an enlarged brain or excessive cerebrospinal fluid in the brain. Hedgehog, as well as being a developmental morphogen, regulates the proliferation and survival of stem cell populations, explaining its involvement in development of tumours. Patients with Gorlin syndrome often develop tumours throughout the body. <br />
<br />
{Question 5<br />
|type="()"}<br />
- &nbsp; <br />
- &nbsp; <br />
- &nbsp; <br />
+ &nbsp; <br />
||Replace with Answer<br />
<br />
{Question 6<br />
|type="()"}<br />
- &nbsp; <br />
- &nbsp; <br />
- &nbsp; <br />
+ &nbsp; <br />
||Replace with Answer<br />
</quiz><br />
<br />
==Glossary==<br />
<br />
{| class="pretty table"<br />
|-<br />
|'''Term'''<br />
|'''Definition'''<br />
|-<br />
|Acyl-transferase<br />
|A protein responsible for catalyzing the transfer of a palmitic acid moiety to the N-terminus of the hedgehog signalling molecule.<br />
|-<br />
|Brother of ihog (Boi)<br />
|A surface protein that enhances hedgehog signal transduction through PTC in ''Drosophila''.<br />
|-<br />
|Casein kinase I (CKI)<br />
|A kinase that is thought to phosphorylate the Smoothened receptor to activate it in the hedgehog signalling pathway.<br />
|-<br />
|Cubitus interruptus (Ci)<br />
|A transcription factor found in the hedgehog signalling pathway of ''Drosophila'', which binds to promoter regions on the DNA in the nucleus to activate target genes of the pathway.<br />
|-<br />
|Costal-2 (Cos2)<br />
|A kinesin like protein which interacts with the C terminus of Smoothened and acts like a scaffolding protein and allows proteins such as Fused to bind to it.<br />
|-<br />
|Denticle<br />
|Bristle like projections off the segments on the ''Drosophila'' embryo.<br />
|-<br />
|Dally<br />
|An HSPG, which mediates loacalizaiton and transportation of the hedgehog protein to its targets in ''Drosophila''<br />
|-<br />
|Desert hedgehog (Dhh)<br />
|A homolog of the ''Drosophila'' hedgehog protein, which is expressed most prominently in the gonads of vertebrates, where it plays a possible role in regulating spermatogenesis. <br />
|-<br />
|Frizzled<br />
|A receptor that is part of the Wnt signalling pathway, which binds the protein wingless in order to activate signalling cascades. <br />
|-<br />
|Fused (Fu)<br />
|A kinase that binds to Costal-2 and acts to inhbit Suppressor of Fused by phosphorylating it in the hedgehog signalling pathway.<br />
|-<br />
|Gli<br />
|A family of proteins that acts as transcription factors that were originally isolated in human gliboblastoma. The proteins are important mediators in activating target genes for the hedgehog signalling pathway in vertebrates.<br />
|-<br />
|Glycipan (GPC)<br />
|A family of HSPGs which act in the hedgehog signalling pathway of vertebrates to either enhance or inhibit signal transduction depending on the isoform.<br />
|-<br />
<br />
|Hedgehog (Hh) protein<br />
|A signalling protein widely expressed in the tissue during embryonic development of vertebrates and some other species such as ''Drosophila'', and acts to pattern and develop tissue. The protein is the primary mediator of the pathway.<br />
|-<br />
|Heparin sulfate proteoglycan (HSPG)<br />
|A proteoglycan ,which is a heavily glycosolated protein, which in the context of hedgehog signalling is thought to aid in the localization and transport of hedgehog proteins to their targets.<br />
|-<br />
|Indian hedgehog (Ihh)<br />
|A signalling protein that is a homolog of the ''Drosophila'' hedgehog protein, that primarily acts in regions where there is endochondrial ossification to aid in the maturation of chondrocytes.<br />
|-<br />
|Interference hedgehog (Ihog)<br />
|A surface protein that enhances hedgehog signal transduction through PTC in ''Drosophila''.<br />
|-<br />
|Kif7<br />
|A homolog of Costal-2 in vertebrates, which acts to regulate the downstream signalling of the hedgehog pathway by causing the disassociation of SUFU and Gli.<br />
|-<br />
|Limb bud<br />
|A structure formed during early embryonic development consisting of ectoderm and mesenchyme representing the early limbs, where signalling processes in the bud will eventually lead to the out growth and patterning of the bud.<br />
|-<br />
|Patched (PTC)<br />
|Patched is a transmembrane receptor expressed on cells that are sensitive to signalling via the hedgehog pathway, where its extracellular domain binds to the hedgehog protein to inactivate it. The receptor it self without hedgehog binding actively inhibits Smoothened. <br />
|-<br />
|Primary cilia<br />
|An organelle that consists of an outward projection from the cell surface, which is thought to be critical for hedgehog signalling in vertebrates as it houses many components of the pathway. <br />
|-<br />
|Protein kinase A (PKA)<br />
|A kinase that is thought to phosphorylate the Smoothened receptor to activate it in hedgehog signalling.<br />
|-<br />
|Smoothened (SMO)<br />
|A G-protein coupled receptor like receptor integral to the hedgehog signalling pathway and acts to set in motion a series of events that lead to the activation of transcriptional factors that activate target genes of the hedgehog pathway.<br />
|-<br />
|Sonic hedgehog (Shh)<br />
|The most widely expressed homolog of the ''Drosophila'' hedgehog protein found in vertebrates, playing a key role in embryonic development of humans.<br />
|-<br />
|Suppressor of Fused (SUFU)<br />
|A protein in the hedgehog signalling pathway which when active, inhibits the translocation of Cubitus interruptus into the nucleus by leading to its phosphorylation, and eventually degradation via the proteosome.<br />
|-<br />
|Wingless protein<br />
|A protein produced as a downstream target of the hedgehog signalling pathway in ''Drosophila'', which activates the Wnt pathway by binding to the Frizzled receptor.<br />
|-<br />
|Zone of polarizing activity (ZPA)<br />
|The posterior region of the limb bud mesenchyme, which aids in the signalling of it to pattern the posterior anterior axis with respect to the digits through mediators such as sonic hedgehog.<br />
|-<br />
|}<br />
<br />
===Additional Glossary Links===<br />
[[A|A]] | [[B|B]] | [[C|C]] | [[D|D]] | [[E|E]] | [[F|F]] | [[G|G]] | [[H|H]] | [[I|I]] | [[J|J]] | [[K|K]] | [[L|L]] | [[M|M]] | [[N|N]] | [[O|O]] | [[P|P]] | [[Q|Q]] | [[R|R]] | [[S|S]] | [[T|T]] | [[U|U]] | [[V|V]] | [[W|W]] | [[X|X]] | [[Y|Y]] | [[Z|Z]] | [[Numbers|#]]<br />
<br />
== References ==</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=2016_Group_Project_4&diff=253800
2016 Group Project 4
2016-10-24T08:53:22Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Project2016header}}<br />
{{Group Assessment Criteria table}}<br />
<!-- Do not delete the above template from the Group project page. --><br />
<br />
= Hedgehog signalling pathway =<br />
==Introduction==<br />
[[File:Hedgehog.jpg|thumb|300px|An image of a hedgehog, the animal of which the Hh proteins are named after.]]<br />
The Hedgehog (Hh) signalling pathway is an important part of the early embryo with regards to the patterning and development of the nervous system, limbs and the cranio-facial region in vertebrates and the polarization of the segments in the ''Drosophila'' embryo. It was first identified in 1980 by Christiane Nüsslein-Volhard and Eric Wieschaus, alongside a group of other genes regulating segment polarity in ''Drosophila'' embryonic development<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. The pathway itself consists of Hh proteins, where there are three identified homologs in vertebrates, being sonic hedgehog (SHH), Indian hedgehog (IHH), and desert hedgehog (DHH) <ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. All homologs are expressed at varying levels within different tissues in the body, and also act as a form of redundancy to an extent between one another. <br />
<br />
The signaling pathway is highly conserved between various species<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. and acts via a G protein coupled receptor like receptor, which uninhibited via the action of the Hh proteins. The pathway overall acts via a balance of dephosphorylation<ref name="PMID10966113"><pubmed>10966113</pubmed></ref> and degradation of proteins<ref name="PMID15102702"><pubmed>15102702</pubmed></ref> in order to regulate transcription factor activity to express various genes to carry out its action. The Hh pathway is also highly implicated when it comes to abnormalities in development, as it is implicated in diseases such as holoprosencephaly and cleft lip and palate. Overall Hh signaling pathways play a large role in embryological development, which will be discussed in detail on this page.<br />
<br />
== History ==<br />
{| class="pretty table"<br />
| '''1980'''<br />
|Christiane Nüsslein-Volhard and Eric Wieschaus first identified a group of genes including those related to the Hedgehog signalling pathway and linked them to the segmentation and planning of the embryo in ''Drosophila melanogaster'' by introducing mutagenic substances to the developing embryo<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Multiple researchers including Andrew P. McMahon and Clifford Tabin discovered three equivalent homologs in vertebrates of the ''Drosophila melanogaster'' hedgehog gene, known as sonic hedgehog (Shh), desert hedgehog (Dhh) and indian hedgehog (Ihh), by looking at DNA sequences similar to that of the gene in the fruit fly<ref><pubmed>7916661</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Clifford Tabin and his lab identified the role of Shh in localising the limb bud, where they identified protein to be expressed within a region of the limb bud known as the zone of polarising activity (ZPA), showing that SHH is sufficient to induce the production of a ZPA, and thus limb bud formation in chick embryos<ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|Sonic hedgehog secreted by the notochord was identified to induce ventral cell types in the neural tube during embryonic development, most notably the floor plate cells and the motor neurons as shown in chick embryos. Such differentiation between the two cell types is thought to be a matter of sonic hedgehog concentrations experienced by the neural plate cells<ref name="PMID7736596"><pubmed>7736596</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|A shared Nobel prize in physiology or medicine was awarded to Christiane Nüsslein-Volhard and Eric Wieschaus for their researching regarding the identification of the developmental genes relating to the formation and patterning of the early embryo via genes.<br />
|-<br />
|'''1996'''<br />
|Studies showed that human homologs of the Patched gene, a component of the hedgehog pathway, is a key gene that is mutated in Gorlin Syndrome, which characterised by a predisposition for basal cell carcinomas, the most common cancers in humans and developmental abnormalities<ref name="PMID8658145"><pubmed>8658145 </pubmed></ref>.<br />
|-<br />
|'''1999'''<br />
|Researchers implicated Indian hedgehog as a key signalling molecule for the maturation and differentiation of prehypertrophic chondrocytes, where Indian hedgehog null mice were shown to have a lack of mature chondrocytes and no development of osteoblast cells in endochondrial bone. This was thought to be due to Indian hedgehog having a feedback signal controlling parathyroid hormone related protein, which regulates endochondrial bone development<ref name="PMID10465785"><pubmed>10465785</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Sonic hedgehog was identified to regulate the proliferation of adult neural stem cells as shown in the hippocampus of rats and in vitro for neural progenitor cells isolated from the hippocampus<ref name="PMID12469128"><pubmed>12469128</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Studies on Shh function found that it can act as a chemoattractant in the developing embryo spinal cord, to help guide commissural axons to the midline of the floor plate<ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
|-<br />
|'''2009''<br />
|Mouse models showed that reduction in hedgehog signalling allows for transient improved response to chemotherapy with regards to mouse models of human pancreatic ductal adenocarcinoma, a cancer with one of the highest mortality rates in humans<ref name="PMID19460966"><pubmed>19460966</pubmed></ref>.<br />
|}<br />
<br />
This time line regarding the discoveries in the hedgehog signalling pathway is by no means exhaustive, but a selection of relatively large discoveries that had a significant impact in the field on the basis of citations.<br />
<br />
== Origin of name ==<br />
<br />
[[File:Bands of denticles in normal and Hh mutant Drosophila embryo.jpeg|thumb|250px|Differences in patterning of the denticle bands in normal and mutated hedgehog gene variant ''Drosophilia'' embryo]]<br />
<br />
The name hedgehog came about when Christiane Nüsslein-Volhard and Eric Wieschaus first identified the group of genes controlling polarization of the segments in the ''Drosophila'' early embryo. They noticed that when they mutated the Hh gene, making it non-functional, that the bands of denticles formed during the early ''Drosophila'' embryo formation became more diffuse as opposed to being distinct normally. The denticles would all clump together forming a single patch on the surface of the embryo, as opposed to normally outlining the distinct segments of the embryo as bands<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. This gave the embryo spiny and prickly look similar to that of the back of a hedgehog.<br />
<br />
From there on in the gene was called the hedgehog gene where homologs in vertebrates discovered along the line kept to this naming structure giving various species of hedgehog names to the genes such as Indian hedgehog, and desert hedgehog, with the exception being sonic hedgehog, which is named after a fictional character in the video game “Sonic the Hedgehog”.<br />
<br />
== Function ==<br />
===Overview===<br />
{| class="pretty table"<br />
|'''Hedgehog protein homolog'''<br />
|'''Function'''<br />
|-<br />
| Sonic hedgehog ||<br />
*Expressed in zone of polarizing activity of the limb bud where it plays a role in helping to pattern the anterior and posterior aspect of the limbs <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
*Based on time and concentration of SHH due to diffusion from the point of secretion in the limb bud, SHH also plays a role in determining digit identity <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>.<br />
*Acts as a chemoattractant to guide commissural axons in the floor plate of the neural tube towards the midline <ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
*Patterns the developing cusps of the teeth and their relative positions in the jaw, and is also essential for the growth of the teeth <ref name="PMID11044393"><pubmed>11044393</pubmed></ref>.<br />
*SHH released from the notochord acts to induce formation of the floor plate, motor neurons, and dopaminergic neurons, as well as signalling the induction of the ventral cell types in the neural tube <ref name="PMID8790332"><pubmed>8790332</pubmed></ref>.<br />
|-<br />
| Desert hedgehog ||<br />
*Plays a possible role in regulating spermatogenesis as due to the highly localised expression in the testes by pre-Sertoli cells, and the fact that mice with no DHH present are infertile, with no mature spermatozoa <ref name="PMID8805249"><pubmed>8805249</pubmed></ref>. <br />
*DHH derived from Schwann cells signal development of peripheral nerves, by inducing the production of a connective tissue sheath around them <ref name="PMID10482238"><pubmed>10482238</pubmed></ref>.<br />
|-<br />
| Indian hedgehog ||<br />
*Aid in the signalling of proliferating chondrocytes to undergo hypertrophic differentiation during endochondral ossification<ref name="PMID8662546"><pubmed> 8662546</pubmed></ref>.<br />
*Plays a key role in yolk sac angiogenesis, as seen in studies where an absence of IHH leads to death of the embryo due to poor yolk sac vasculature <ref name="PMID11807029"><pubmed>11807029</pubmed></ref>.<br />
|}<br />
<br />
===Limb development===<br />
<br />
====Research background====<br />
<br />
The hedgehog signalling pathway plays a significant role with regards to the embryonic development of the limbs in vertebrates, specifically SHH. For a while the mechanism of which the limb was patterned on the anterior to posterior axis was quite unknown. Early studies had shown that grafting posterior wing bud cells to the anterior region of the wing bud in a chick embryo, an equal amount of extra digits was produced to that of which was normally produced, and in a mirror image pattern<ref name="PMID4390734"><pubmed>4390734</pubmed></ref>. This showed that the pattern of which the digits were produced were polarized with respect to that of the graft from the limb bud, which has become to be described as the zone of polarizing activity (ZPA). Further studies mapped the ZPA, by showing the area of the wing bud on the chick with the highest polarizing activity to be the posterior margin of the wing bud<ref name="PMID4719010"><pubmed>4719010</pubmed></ref>. Furthermore, studies later on found that the amount or concentration of ZPA cells grafted played a role in the amount of digits induced and how polarized they were<ref name="PMID7453825"><pubmed>7453825</pubmed></ref>. This ultimately gave rise to studies regarding a potential morphogen, which could potentially provide this concentration dependent activity of polarization when it comes to the limb bud. Studies to find this morphogen led to the discover of the ability for retinoic acid to mimic the polarizing action of the ZPA when applied locally to the limb bud<ref name="PMID7070499"><pubmed>7070499</pubmed></ref>. This was found to be due to the induction of a second morphogen known as SHH, where when cells that express SHH are grafted onto the limb bud, polarized digit development is induced<ref name="PMID7720566"><pubmed>7720566</pubmed></ref>.<br />
<br />
====Polarizing activity of sonic hedgehog====<br />
[[File:Digit patterning based on time and concentration of SHH exposure.jpg|thumb|450px|Regions of the limb bud and the digits they form into categorised into how they interact with SHH. The red and green dot represent the 5th and 4th digit region respectively.]]<br />
More recent studies have sought to elucidate how SHH mediates such a polarizing effect in terms of digit identification and its underlying mechanism. It has been suggested that such an effect is heavily concentration dependent similar to that of when transplanting the chick wing bud ZPA cells, acting in a dose dependent matter, due to the ability of SHH to modulate signaling at long ranges via diffusion<ref name="PMID11389830"><pubmed>11389830</pubmed></ref>. This implies that a gradient of varying concentrations of SHH diffused through the mesenchyme of the limb bud leads to the identification of posterior and anterior digits.<br />
<br />
Current research has also suggested that not only is the concentration gradient of SHH important for the patterning of the digits, but also the temporal gradient, being the length of time of exposure of SHH to the mesenchyme of the limb bud. Studies have shown in mice that of the 5 digits, polarization from the posterior end, being digit 5, to the anterior end being digit 1 are due to different mechanisms. Digits 5 and 4 have been shown to be comprised of the SHH expressing cells and thus both experience maximal levels of SHH, and thus cannot be distinguished on the basis of a concentration gradient. As a result, temporal gradients are employed, where the expression of SHH in both regions that become the digits vary, where studies have shown that SHH expression in the primordium of digit 5 is maintained longer than that in digit 4 gradient <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>. When it comes to digit 3 and 2, there is differentiation based on the concentration gradient of SHH from the ZPA, where due to the ZPA being further away to digit 2 than 3, the concentration of SHH will be higher at 3<ref name="PMID15315763"><pubmed>15315763</pubmed></ref> <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>. In terms of digit 1, the levels of SHH are so low at this point that it is said to be SHH independent, and actually reliant on the absence of SHH for normal differentiation. With regards to how SHH actually mediates its action, it is thought to be by a balance between the transcription factor Gli3 and SHH expression, which activates Gli1, Gli2 and Gli3 repressor, effectively counteracting Gli3. Gli3 is considered to promote the inhibition of digit formation and identification, while the downstream targets of SHH are thought to promote it<ref name="PMID17400206"><pubmed>17400206</pubmed></ref>.<br />
<br />
Other research has also shown the possibility of SHH signaling as a way to prime the posterior mesenchyme and induce the production of bone morphogenetic protein 2 (bmp2), which is thought to be the morphogen creating the chemical gradient for digit identification<ref name="PMID10704381"><pubmed>10704381</pubmed></ref>. Overall the mechanism at which SHH work to pattern the posterior anterior axis of the limb bud is still relatively unknown, and further research is being conducted to elucidate how the underlying mechanisms such as the downstream targets of SHH affect digit formation.<br />
<br />
=== Neural development ===<br />
<br />
=== Organogenesis ===<br />
The Hedgehog Signalling pathway is a pathway sending information to embryonic cells which plays an especially important role in the regulation of organogenesis. These processes include the organization of the brain (craniofacial) and the growth of appendages with further studies implicating the Hedgehog Signalling pathway in the development of the small intestine, lungs and the pancreas.<br />
<br />
== Mechanism ==<br />
<br />
=== Processing of precursor ===<br />
<br>[[File:Processing of Hh precurosr.jpg|thumb|250px|Summary of the steps in the processing of the Hh protein precursor into a functional signalling molecule]]<br />
Hedgehog (Hh) proteins are produced as precursors, which must be processed by the cells producing it before being able to perform its signalling function. The process by which the Hh protein is processed begins with its signal sequence at its N terminus directing the translocation of the precursor into the endoplasmic reticulum, where it is removed via signal peptidase<ref><pubmed>1394430</pubmed></ref>. This process allows the C terminus of the Hh protein to catalyze the cleavage and addition of cholesterol on itself to form a C terminal processing domain and an N terminal processing domain associated with a cholesterol group on its C terminus<ref><pubmed>21357747</pubmed></ref>. The portion associated with the cholesterol will go on to form the signalling molecule, while the C terminal processing domain has no known signalling function<ref><pubmed>8824192</pubmed></ref>. <br />
<br />
At this point the Hh protein associated with the cholesterol is able to perform its signalling action, but further modification is still required to ensure efficient signalling. This occurs when the cholesterol group attached to the Hh protein associates with the plasma membrane of the cell, which allows for the addition of a palmitic acid moiety to the N terminal of the protein by an acyl-transferase known as skinny hedgehog<ref><pubmed>11486055</pubmed></ref>. Studies have shown that such an addition allows for an increase in potency in signalling of Hh proteins of 30-fold over its form without palmitic acid added<ref><pubmed>9593755</pubmed></ref>. From this point the Hh protein is now fully active and can either remain associated to the plasma membrane of the cell for autocrine action or be secreted for paracrine action.<br />
<br />
=== Mechanism of signalling ===<br />
<br />
==== ''Drosophila melanogaster'' ====<br />
<br>[[File:Hh Signalling Pathway.jpg|thumb|600px|Steps regarding the processing of the hh protein precursor into the fully functional signalling molecule.]]<br />
<br />
The Hh signaling pathway has been well studied in ''Drosophila melanogaster'', and has been shown the be conserved to an extent across it and mammals making the species a suitable model for Hh signalling in humans<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. In ''Drosophila melanogaster'', the Hh pathway begins when the Hh proteins bind to the extracellular domain of the transmembrane protein known as Patched (PTC) to inactivate it. This inactivation occurs by Hh trapping PTC in an inactive conformational state<ref><pubmed>27647915</pubmed></ref>. After binding of Hh occurs to PTC and it is inactivated, the receptor and Hh protein is thought to be endocytosed by the cell where they undergo lysosomal degradation in order to limit Hh concentration, thus limiting its spread to other cells and PTC activity<ref name="PMID15102702"><pubmed>15102702</pubmed></ref>. In the absence of Hh, PTC acts to suppress the expression of the Smoothened (SMO), a G-protein coupled receptor like receptor, and thus its signaling. How PTC achieves this inhibition of SMO is currently unclear. Studies have suggested that due to the highly phosphorylated nature of SMO when active, that PTC acts to dephosphorylate SMO in order to repress its signaling. It is thus that binding of Hh to PTC reduces PTCs ability to promote dephosphorylation of SMO, leading to its increased activity and expression on the cell surface <ref name="PMID10966113"><pubmed>10966113</pubmed></ref>. It is thought that the phosphorylation required to activate SMO are dependent on protein kinase A (PKA) and casein kinase I (CKI) <ref><pubmed>15616566 </pubmed></ref>.<br />
<br />
This overall increased phosphorylation of SMO due to a repression of PTC activity by Hh leads to an accumulation of SMO on the cell surface, which collectively allows for SMO to exert its activity. Most importantly phosphorylation also disrupts intramolecular electrostatic interactions between SMO molecules which switches the molecule into its active conformational state <ref><pubmed>17960137 </pubmed></ref>. Generally, SMO has been shown to have very little signal transducing ability, and thus this accumulation allows it to jointly transduce as substantial signal. This occurs by the C terminus of SMO on the intracellular domain interacting with the kinesin like protein Costal-2 (Cos2), which is thought to bind to microtubules in order to acts as a scaffolding protein <ref><pubmed>18691888 </pubmed></ref>. Then the kinase known as Fused (Fu) binds to Cos2, which phosphorylates Suppressor of Fused (SUFU) to inhibit it. Without this inhibition SUFU goes onto prevent the translocation of the transcriptional factor Cubitus interruptus (Ci) into the nucleus by leading to its phosphorylation, and subsequently its partial cleavage via the proteosome. The partial cleavage of Ci leaves a lower molecular weight protein known as Ci repressor (CiR) or Ci75, which translocates into the nucleus and acts to repress the target genes of the Hh signalling pathway via Ci<ref><pubmed>9215627</pubmed></ref>. Thus overall inhibition of SUFU increases the amount of Ci entering into the nucleus of the cell, and activating transcription of target genes of the Hh pathway<ref><pubmed>10952898 </pubmed></ref>.<br />
<br />
At this point Ci is able to activate the transcription of various genes, which include importantly the ''ptc'' gene, which encodes the PTC receptor. It is thus as a result of this, that PTC expression will be increased in response to Hh pathway induction, which negatively feeds back to reduce Ci signaling induction, in order to maintain homeostasis and regulate the intensity and duration of the signaling from Hh<ref><pubmed>9053330</pubmed></ref>. Furthermore the ''wg'' gene, encoding the wingless protein is also activated by Ci, which leads to activation of the Wnt pathway via the Frizzled receptor in adjacent cells expressing the gene ''engrailed'' <ref><pubmed>9502727</pubmed></ref> <ref><pubmed>10457026</pubmed></ref>. This overall stabalizes the boundaries between the segments of the developing ''Drosophila melanogaster'' signalled by the gene ''engrailed''<ref><pubmed>3282172</pubmed></ref>.<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=w1xXD9kss2w</html5media><br />
<br><br><br />
An overview of the hedgehog signalling pathway in ''Drosophila''<ref>YouTube. (2016). The Hedgehog signalling pathway in Drosophila online Available at: https://www.youtube.com/watch?v=w1xXD9kss2w</ref>.<br />
<br />
==== Mammals ====<br />
<br />
Although the Hh signaling pathway has been conserved across species to an extent <ref name="PMID8595881"><pubmed>8595881</pubmed></ref>, key differences exist when observing the pathway within mammalian tissue in contrast to that which has been studied in ''Drosophila melanogaster''. In mammalian cells and all other vertebrates, Hh signalling is dependent on an organelle known as the primary cilia, which are projections outwards from the cells surface. The importance of such an organelle in the signalling pathway comes as a result of PTC1, one of the two PTC receptor homologs in mammals, that binds to the Hh homolog Sonic Hh (Shh), exists within the cilia<ref><pubmed>17641202</pubmed></ref>. The mechanism of action of SMO inhibition and activation is poorly understood currently, but evidence has suggested that PTC1 acts to inhibit SMO when unbound to Shh by acting as a pump to remove oxysterols from the cilia into the extracellular space. <ref><pubmed>PMC1462959</pubmed></ref>. These oxysterols are normally thought to bind and accumulate around the SMO receptors, which in turn prevents internalization and deactivation of SMO, leading to it accumulating on the apical primary cilia<ref><pubmed>16136078</pubmed></ref>. Other studies have also suggested that Shh has a role in increasing phosphorylation of SMO, which is required for it to accumulate as well on the cilia<ref><pubmed>21695114</pubmed></ref>. Overall the net action of Shh initially is believed to cause accumulation of SMO at the cilia by inhibiting PTCH1 and phosphorylation of SMO.<br />
<br />
How SMO acts next is relatively unknown but, it has been shown to promote the disassociation between SUFU and Gli3 transcription factor, which allows Gli to be transported to the nucleus to activate effector genes of the pathway. Gli is normally bound in the cytoplasm to SUFU, where SUFU promotes the partial degradation of Gli into its repressor form, similar to that in the fruit fly model<ref><pubmed>20360384</pubmed></ref>. Alongside this, Kif7, a Cos2 homolog, has been shown to migrate to the apex of the cilium in response to SMO accumulation at the cilium, where it has been postulated to also promote disassociation of SUFU and Gli<ref><pubmed>19592253</pubmed></ref>. On the other hand, Kif7 is also thought to play an inhibitory role for the signaling pathway as when it is localized at the base of the cilia in the absence of Hh signaling and traffics Gli factors away from the cilia<ref><pubmed>19666503</pubmed></ref>. This all leads to an accumulation of active Gli transcription factors which migrate to the nucleus in order either inhibit or activate gene transcription in response to Hh signaling.<br />
<br />
== Animal models ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br />
Hedgehog (Hh) protein signal was initially discovered through experimentation on the fruit fly, "Drosophila melanogaster". It is through this model that we are able to discover not only the functional components of this pathway but also understand its role in embryonic development. Through application of this information on the human biological system we are able to find the cause and thus potential treatments of defects and diseases caused by interruption or mutation of the Hedgehog signalling pathway. <br />
<br />
Upon further research on Drosophila it was found that Hh may play a role in germ cell proliferation and in particular, may control the proliferation and activity of somatic cells found within the germarium, which is the most anterior structure within the Drosophila ovary. <ref>Ovaries (Drosophila) definition. (2016). Groups.molbiosci.northwestern.edu. Retrieved 10 September 2016, from http://groups.molbiosci.northwestern.edu/holmgren/Glossary/Definitions/Def-D/Drosophila_Ovaries.html</ref> Thus, the Hh signalling pathway is vital in egg chamber formation and its consequent envelopment, budding and polarisation. It has also been observed that somatic cell proliferation is dependent on this pathway and thus, the number of pre-follicle cells is subject to the effect of the Hh signalling pathway. <ref><pubmed>8620839</pubmed></ref> Further studies have also indicated the role played by this pathway in activating the Epidermal growth factor receptor (EGFR) signalling pathway as seen in the induction of EGFR by Hh in Drosophila head development. <ref><pubmed>10331974</pubmed></ref> In addition, research on Drosophila has indicated the direct effect of Hh signalling on tracheal branch patterning. <ref><pubmed>11290298</pubmed></ref><br />
<br />
Despite ongoing research on "Drosophila melanogaster" to uncover the workings of the Hedgehog signalling pathway, further research is needed to confirm and further current findings. In addition, it is evident that it is through the study of these fruit flies that we are able to gain a basis of understanding of the causes of certain human diseases and thus propel research into treatments for sufferers. <br />
<br />
===Blockage of Shh Signalling in Forebrain Neuroectoderm of Chick Embryos===<br />
<br />
The Hedgehog signalling pathway plays a significant role in embryonic development, particularly of the forebrain. Due to its role in development of craniofacial features by contributing to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm, a disruption in this pathway can result in a variety of birth deformities including holoprosencephaly (HPE), where the prosencephalon (forebrain) fails to divide into 2 separate hemispheres, telencephalon and diencephalon <ref>Holoprosencephaly - NORD (National Organization for Rare Disorders). (2016). NORD (National Organization for Rare Disorders). Retrieved 10 September 2016, from http://rarediseases.org/rare-diseases/holoprosencephaly/</ref>, as well as cleft lip and palate. The function of Sonic Hedgehog (Shh) and its signalling pathway on the formation of forebrain neuroectoderm was studied in chick embryos.<br />
<br />
It was found that the disruption of Shh signalling in the neural tube of chick embryos resulted in the lack of division of the forebrain into the diencephalon and telencephalon. This is in fact, as stated earlier, the fundamental cause of the rare condition, holoprosencephaly. It was discovered that the Shh signalling pathway in the diencephalon was responsible for gene expression in the telencephalon. <br />
<br />
In addition, through experimentation on chick embryos it was found that through Shh signalling the development of the forebrain regulates and controls facial morphogenesis, particularly of the upper and middle face. Therefore, interference with Shh signalling in the forebrain prevents this intrinsic communication, thus hindering Shh expression in facial ectoderm. This results in brain malformation accompanied by facial disfiguration as seen in patients suffering from HPE. Other malformations caused by blockage of Shh signalling in craniofacial development include, hypotelorism (decreased space between the orbits), growth restriction as well as cleft lip and palate as mentioned previously. <br />
<br />
A commonality discovered among all forms of Shh signalling disruption was two facial defects, “the loss of mediolateral expansion of the face and absence of proximodistal outgrowth of the frontonasal prominence”<ref><pubmed>15979605</pubmed></ref> (Ralph et al., 2005). Through reference to studies performed on chick and mice embryos, it was found that Shh signalling is particularly vital in development of maxillary and frontonasal components of the cranium.<br />
<br />
This breakthrough study on the inhibition of Shh signalling in chick embryos has significantly filled the gap in our understanding of the Sonic Hedgehog signalling pathway. It is evident that this pathway is crucial in the development of the forebrain and in turn regulates and controls the development of the facial skeleton. This is further proven through the observation that in the event of Shh signalling inhibition there is a development of craniofacial malformations.<br />
<br />
=== Shh knockout mice ===<br />
<br />
Extensive research on Shh knockout mice allowed discovery of the roles of Shh in embryonic development and patterning of the limb buds and sclerotomes, and maintenance of the notochord. <ref><pubmed>8837770</pubmed></ref> These mice expressed defects in the cephalic neural tube with the fusion of telencephalic and optic vesicles. Through this research it is evident that Shh is partially responsible for the subdivision of the eye field through forebrain optic stalk development, along with formation of the ventral midline. It is these forebrain abnormalities established in the absence of Shh that results in congenital malformations of holoprosencephaly, development of a single nasal chamber and other facial defects in humans. <br />
<br />
The absence of the vertebral column including, the intervertebral discs and vertebrae along with the medial regions of the ribs were observed within Shh knockout mice. This lack of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population (Chiang et al., 1996). In addition, though the role of Shh in patterning the anterior-posterior limb axis is evident through anterior limb bud cell death in the absence of Shh, it is also responsible for the development of proximal-distal limb segments, particularly in the patterning of structures at the level of or distal to the latent elbow and knee joints. <ref><pubmed>11476582</pubmed></ref> This was perceived after observing the incomplete formation of distal limb structures with abnormal anterior-posterior axis formation (Chiang et al., 2001). Thus, Shh knockout mice provide great insight into the functions of Shh in embryonic development and the abnormalities formed in the absence of this signalling protein. <br />
<br />
== Clinical Significance ==<br />
<br />
===Gorlin Syndrome===<br />
[[File:1 week year old newborn girl with cleft lip and palate.png|thumb|An image of a 1 week year old newborn girl with cleft lip and palate]]<br />
Gorlin syndrome, also known as nevoid basal cell carcinoma syndrome, is a heritable disease resulting from heterozygousity in Hh receptor, Patched (PTC). The PTC gene encodes a protein which binds sonic hedgehog (Shh) and it is this binding which inhibits the Hh signalling pathway. However mutation of PTC leads to activation of the pathway <ref><pubmed>9620294</pubmed></ref>. The syndrome is characteristic of skin cancer basal cell carcinoma and cerebellum cancer medulloblastoma. 1-2% of medulloblastomas and 0.5% of basal cell carcinomas are attributable to the disease. Patients present with craniofacial and brain abnormalities such as cleft palate, strabismus, macrocephaly, abnormal development of the corpus callosum and frontal bossing, with an overall overgrown appearance. Skeletal defects such as of the shoulder, ribs and vertebrae are often seen, as well immobile thumbs and polydactyly, which is a deformity of the hand or feet in which they have one or more extra fingers or toes. Apart from physical anomalies, patients have an increased risk of tumours throughout the body including cardiac, ovarian fibromas, ovarian dermoid cysts, meningiomas, and fibrosarcomas. Additionally with time, patients eventually undergo intracranial calcification and dyskeratotic pitting of the hands and feet whereby skin cells prematurely convert to keratin <ref><pubmed>8681379</pubmed></ref>.<br />
<br />
===Holoprosencephaly===<br />
<br>[[File:Semilobar holoprosencephaly.jpg|thumb|240px|MRI of fore brain depicting semilobar holoprosencephaly]]<br />
Holoprosencephaly (HPE) is a congenital disease caused by incomplete division of the prosencephalon (embryonic forebrain) into separate lobes of the cerebral hemispheres. The Shh gene has been identified as a HPE-causing gene however recent evidence has also investigated into the PTC gene, which acts to repress Shh signalling. A gain in repressive action of PTC is seen, leading to decreased Shh signalling, and thus HPE <ref><pubmed>11941477</pubmed></ref>. Clinical expression is variable between patients and is dependent upon the 3 forms of increasing severity: lobar, semi-lobar and alobar HPE, where patients can present with right and left ventricles however with a continuous frontal cortex in lobar HPE, to carrying a single cerebral ventricle in alobar HPE. Along with forebrain abnormalities, facial anomalies are also seen including midline cleft lip and/or flat nose, ocular hypotelorism characteristic of a small distance between the eyes. In severe rare cases of cyclopia, a non-functioning nose may be observed in the form of proboscis and the patient may present with a single eye at the root of the nose <ref><pubmed>20583177</pubmed></ref>. Furthermore, patients with HPE often develop a large number of medical issues including epilepsy, mental retardation, thyroid and adrenal hypoplasia due to lack of hypothalamus or pituitary gland development, and diabetes insipidus.<br />
<br />
===Medulloblastoma===<br />
Medulloblastoma is a cancerous tumour of the cerebellum where the cells of origin are the granular cell precursors found in the neonatal cerebellum, explaining its high prevalence in children <ref><pubmed>19171780</pubmed></ref>. Commonly, medulloblastomas are found deep in the cerebellum along the midline, however with desmoplastic medulloblastomas, they are found more laterally and superficial. As seen previously with Gorlin syndrome and holoprosencephaly, PTC is also associated with the development of medulloblastoma, and misregulation of Hh-PTC signalling in cells of the external germinal layer, the layer found on the surface of the cerebellum, is thought to give rise to the tumour. In experimental studies, it has been discovered that PTC is highly transcribed in medulloblastomas and in approximately 30% of PTC heterozygous mice the tumour develops <ref><pubmed>9205058</pubmed></ref> <ref><pubmed>9262482</pubmed></ref>. In patients with medulloblastoma, often children, the most common symptoms seen are vomiting, ataxia, psychomotor regression, drowsiness and anorexia. With age, patients are seen to get more frequent headaches, and show psychological symptoms such as behavioural problems, poor performance in school, and anxiety. In patients exhibiting life-threatening symptoms due to increased intracranial hypertension, bradycardia, convulsions and coma are often seen <ref><pubmed>21537925</pubmed></ref>.<br />
<br />
Watch below for a breakdown on Hedgehog's role in Tumour Development!<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=gFWO3I-oqsE</html5media><br />
<br><br><br />
An overview of the Hedgehog Signalling Pathway in Tumour Development<ref>YouTube. (2016). The Hedgehog Signaling in the Tumor Microenvironment - Research Hedgehog online Available at: https://www.youtube.com/watch?v=gFWO3I-oqsE</ref>.<br />
<br />
<br />
<br />
== Current research ==<br />
<br />
==Quiz==<br />
<br />
<quiz display=simple><br />
<br />
{1. Which of the following are the reasons that are thought to allow for the patterning of digits in vertebrates.<br />
|type="[]"}<br />
+ &nbsp;Concentration gradient of sonic hedgehog.<br />
+ &nbsp;Temporal gradient of sonic hedgehog.<br />
- &nbsp;The varying homologs of the hedgehog proteins .<br />
- &nbsp;The length of the hedgehog molecule.<br />
+ &nbsp;No sonic hedgehog signalling.<br />
- &nbsp;The type of cholesterol attached to the hedgehog molecule.<br />
||<br> For differentiation of the individual digits in mice to occur it is thought that each digit requires a different signalling mechanism. Digits 5 and 4 which are most posterior, are derived from the region around the zone of polarising area which contain Shh secreting cells, meaning these regions will experience a saturation of Shh signalling and cannot be differentiated by Shh concentration. As a result it is thought that these digits are identfied based on the temporal gradient, meaning that the length of which Shh is expressed in these regions differentiates the digits from one another with digit 5 expressing Shh for longer. Digits 3 and 2 are further away but still receive Shh signalling due to the diffusible nature of Shh from the ZPA, which forms a concentration gradient. This means the the concentration at digit 2 will be less than digit 3 due to being further away from the ZPA and thus can be differentiated from one another based on this concentration. Finally the digit 1 is differentiated on the basis of not receiving any Shh signalling at all. Thus it is a combination of concentration gradient of Shh, temporal gradient of Shh, and independence from Shh.<br />
<br />
{2. Which of the following are correct with regards to the hedgehog signalling pathway in ''Drosophila''.<br />
|type="[]"}<br />
-&nbsp;It occurs at the cillum on the cell surface.<br />
-&nbsp;Hedgehog protein binding to the Patched receptor activates it to inhibit Smoothened.<br />
+&nbsp;Hedgehog protein binding to the Patched recetpor inhibits it to activate Smoothened. <br />
+&nbsp;Inhibition of SUFU is critical in allowing Ci to translocate into the nucles and activate downstream targets of the hedgehog pathway.<br />
-&nbsp;The pathway contains 3 homologs including sonic hedgehog, Indian hedgehog, and desert hedgehog.<br />
-&nbsp;The hedgehog protein is initially produced in its fully active form.<br />
||<br> In terms of how the hedgehog protein acts to produce its effect, it must first bind to Patched which activity is inhibiting Smoothened in the absence of the hedgehog protein. The protein acts to trap Patched in its inactive confirmational state cause internalisation and eventually degradation of the receptor. This relives the dephosporylation of the Smoothened, usually induced by Patched, allowing it to accumulate phosphate groups and thus activate. With regards to Ci translocation, SUFU usually inhibits this by leading to phosphorylation of Ci and eventually its cleavage into Ci repressor. During the activation of the hedgehog pathway there is a binding of Fused to Cos2 which phosphorylates SUFU to inactivate it, allowing Ci to translocate into the nucleus and activate downstream targets.<br />
<br />
{Question 3<br />
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{Question 5 (select one or more options)<br />
|type="[]"}<br />
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+ &nbsp; <br />
+ &nbsp; <br />
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+ &nbsp; <br />
+ &nbsp;<br />
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{Question 6<br />
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+ &nbsp; <br />
||Replace with Answer<br />
</quiz><br />
<br />
==Glossary==<br />
<br />
{| class="pretty table"<br />
|-<br />
|Term<br />
|Definition<br />
|-<br />
|Desert hedgehog (Dhh)<br />
|A homolog of the ''Drosophila'' hedgehog protein, which is expressed most prominently in the gonads of vertebrates, where it plays a possible role in regulating spermatogenesis. <br />
|-<br />
|Hedgehog (Hh) protein<br />
|A signalling protein widely expressed in the tissue during embryonic development of vertebrates and some other species such as ''Drosophila'', and acts to pattern and develop tissue. The protein is the primary mediator of the pathway.<br />
|-<br />
<br />
|Indian hedgehog (Ihh)<br />
|A signalling protein that is a homolog of the ''Drosophila'' hedgehog protein, that primarily acts in regions where there is endochondrial ossification to aid in the maturation of chondrocytes.<br />
|-<br />
|Limb bud<br />
|A structure formed during early embryonic development consisting of ectoderm and mesenchyme representing the early limbs, where signalling processes in the bud will eventually lead to the out growth and patterning of the bud.<br />
|-<br />
|Sonic hedgehog (Shh)<br />
|The most widely expressed homolog of the ''Drosophila'' hedgehog protein found in vertebrates, playing a key role in embryonic development of humans.<br />
|-<br />
|Zone of polarizing activity (ZPA)<br />
|The posterior region of the limb bud mesenchyme, which aids in the signalling of it to pattern the posterior anterior axis with respect to the digits through mediators such as sonic hedgehog.<br />
|-<br />
|}<br />
<br />
===Additional Glossary Links===<br />
[[A|A]] | [[B|B]] | [[C|C]] | [[D|D]] | [[E|E]] | [[F|F]] | [[G|G]] | [[H|H]] | [[I|I]] | [[J|J]] | [[K|K]] | [[L|L]] | [[M|M]] | [[N|N]] | [[O|O]] | [[P|P]] | [[Q|Q]] | [[R|R]] | [[S|S]] | [[T|T]] | [[U|U]] | [[V|V]] | [[W|W]] | [[X|X]] | [[Y|Y]] | [[Z|Z]] | [[Numbers|#]]<br />
<br />
== References ==</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=2016_Group_Project_4&diff=253798
2016 Group Project 4
2016-10-24T08:51:26Z
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= Hedgehog signalling pathway =<br />
==Introduction==<br />
[[File:Hedgehog.jpg|thumb|300px|An image of a hedgehog, the animal of which the Hh proteins are named after.]]<br />
The Hedgehog (Hh) signalling pathway is an important part of the early embryo with regards to the patterning and development of the nervous system, limbs and the cranio-facial region in vertebrates and the polarization of the segments in the ''Drosophila'' embryo. It was first identified in 1980 by Christiane Nüsslein-Volhard and Eric Wieschaus, alongside a group of other genes regulating segment polarity in ''Drosophila'' embryonic development<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. The pathway itself consists of Hh proteins, where there are three identified homologs in vertebrates, being sonic hedgehog (SHH), Indian hedgehog (IHH), and desert hedgehog (DHH) <ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. All homologs are expressed at varying levels within different tissues in the body, and also act as a form of redundancy to an extent between one another. <br />
<br />
The signaling pathway is highly conserved between various species<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. and acts via a G protein coupled receptor like receptor, which uninhibited via the action of the Hh proteins. The pathway overall acts via a balance of dephosphorylation<ref name="PMID10966113"><pubmed>10966113</pubmed></ref> and degradation of proteins<ref name="PMID15102702"><pubmed>15102702</pubmed></ref> in order to regulate transcription factor activity to express various genes to carry out its action. The Hh pathway is also highly implicated when it comes to abnormalities in development, as it is implicated in diseases such as holoprosencephaly and cleft lip and palate. Overall Hh signaling pathways play a large role in embryological development, which will be discussed in detail on this page.<br />
<br />
== History ==<br />
{| class="pretty table"<br />
| '''1980'''<br />
|Christiane Nüsslein-Volhard and Eric Wieschaus first identified a group of genes including those related to the Hedgehog signalling pathway and linked them to the segmentation and planning of the embryo in ''Drosophila melanogaster'' by introducing mutagenic substances to the developing embryo<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Multiple researchers including Andrew P. McMahon and Clifford Tabin discovered three equivalent homologs in vertebrates of the ''Drosophila melanogaster'' hedgehog gene, known as sonic hedgehog (Shh), desert hedgehog (Dhh) and indian hedgehog (Ihh), by looking at DNA sequences similar to that of the gene in the fruit fly<ref><pubmed>7916661</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
|Clifford Tabin and his lab identified the role of Shh in localising the limb bud, where they identified protein to be expressed within a region of the limb bud known as the zone of polarising activity (ZPA), showing that SHH is sufficient to induce the production of a ZPA, and thus limb bud formation in chick embryos<ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|Sonic hedgehog secreted by the notochord was identified to induce ventral cell types in the neural tube during embryonic development, most notably the floor plate cells and the motor neurons as shown in chick embryos. Such differentiation between the two cell types is thought to be a matter of sonic hedgehog concentrations experienced by the neural plate cells<ref name="PMID7736596"><pubmed>7736596</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
|A shared Nobel prize in physiology or medicine was awarded to Christiane Nüsslein-Volhard and Eric Wieschaus for their researching regarding the identification of the developmental genes relating to the formation and patterning of the early embryo via genes.<br />
|-<br />
|'''1996'''<br />
|Studies showed that human homologs of the Patched gene, a component of the hedgehog pathway, is a key gene that is mutated in Gorlin Syndrome, which characterised by a predisposition for basal cell carcinomas, the most common cancers in humans and developmental abnormalities<ref name="PMID8658145"><pubmed>8658145 </pubmed></ref>.<br />
|-<br />
|'''1999'''<br />
|Researchers implicated Indian hedgehog as a key signalling molecule for the maturation and differentiation of prehypertrophic chondrocytes, where Indian hedgehog null mice were shown to have a lack of mature chondrocytes and no development of osteoblast cells in endochondrial bone. This was thought to be due to Indian hedgehog having a feedback signal controlling parathyroid hormone related protein, which regulates endochondrial bone development<ref name="PMID10465785"><pubmed>10465785</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Sonic hedgehog was identified to regulate the proliferation of adult neural stem cells as shown in the hippocampus of rats and in vitro for neural progenitor cells isolated from the hippocampus<ref name="PMID12469128"><pubmed>12469128</pubmed></ref>.<br />
|-<br />
|'''2003'''<br />
|Studies on Shh function found that it can act as a chemoattractant in the developing embryo spinal cord, to help guide commissural axons to the midline of the floor plate<ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
|-<br />
|'''2009''<br />
|Mouse models showed that reduction in hedgehog signalling allows for transient improved response to chemotherapy with regards to mouse models of human pancreatic ductal adenocarcinoma, a cancer with one of the highest mortality rates in humans<ref name="PMID19460966"><pubmed>19460966</pubmed></ref>.<br />
|}<br />
<br />
This time line regarding the discoveries in the hedgehog signalling pathway is by no means exhaustive, but a selection of relatively large discoveries that had a significant impact in the field on the basis of citations.<br />
<br />
== Origin of name ==<br />
<br />
[[File:Bands of denticles in normal and Hh mutant Drosophila embryo.jpeg|thumb|250px|Differences in patterning of the denticle bands in normal and mutated hedgehog gene variant ''Drosophilia'' embryo]]<br />
<br />
The name hedgehog came about when Christiane Nüsslein-Volhard and Eric Wieschaus first identified the group of genes controlling polarization of the segments in the ''Drosophila'' early embryo. They noticed that when they mutated the Hh gene, making it non-functional, that the bands of denticles formed during the early ''Drosophila'' embryo formation became more diffuse as opposed to being distinct normally. The denticles would all clump together forming a single patch on the surface of the embryo, as opposed to normally outlining the distinct segments of the embryo as bands<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. This gave the embryo spiny and prickly look similar to that of the back of a hedgehog.<br />
<br />
From there on in the gene was called the hedgehog gene where homologs in vertebrates discovered along the line kept to this naming structure giving various species of hedgehog names to the genes such as Indian hedgehog, and desert hedgehog, with the exception being sonic hedgehog, which is named after a fictional character in the video game “Sonic the Hedgehog”.<br />
<br />
== Function ==<br />
===Overview===<br />
{| class="pretty table"<br />
|'''Hedgehog protein homolog'''<br />
|'''Function'''<br />
|-<br />
| Sonic hedgehog ||<br />
*Expressed in zone of polarizing activity of the limb bud where it plays a role in helping to pattern the anterior and posterior aspect of the limbs <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
*Based on time and concentration of SHH due to diffusion from the point of secretion in the limb bud, SHH also plays a role in determining digit identity <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>.<br />
*Acts as a chemoattractant to guide commissural axons in the floor plate of the neural tube towards the midline <ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
*Patterns the developing cusps of the teeth and their relative positions in the jaw, and is also essential for the growth of the teeth <ref name="PMID11044393"><pubmed>11044393</pubmed></ref>.<br />
*SHH released from the notochord acts to induce formation of the floor plate, motor neurons, and dopaminergic neurons, as well as signalling the induction of the ventral cell types in the neural tube <ref name="PMID8790332"><pubmed>8790332</pubmed></ref>.<br />
|-<br />
| Desert hedgehog ||<br />
*Plays a possible role in regulating spermatogenesis as due to the highly localised expression in the testes by pre-Sertoli cells, and the fact that mice with no DHH present are infertile, with no mature spermatozoa <ref name="PMID8805249"><pubmed>8805249</pubmed></ref>. <br />
*DHH derived from Schwann cells signal development of peripheral nerves, by inducing the production of a connective tissue sheath around them <ref name="PMID10482238"><pubmed>10482238</pubmed></ref>.<br />
|-<br />
| Indian hedgehog ||<br />
*Aid in the signalling of proliferating chondrocytes to undergo hypertrophic differentiation during endochondral ossification<ref name="PMID8662546"><pubmed> 8662546</pubmed></ref>.<br />
*Plays a key role in yolk sac angiogenesis, as seen in studies where an absence of IHH leads to death of the embryo due to poor yolk sac vasculature <ref name="PMID11807029"><pubmed>11807029</pubmed></ref>.<br />
|}<br />
<br />
===Limb development===<br />
<br />
====Research background====<br />
<br />
The hedgehog signalling pathway plays a significant role with regards to the embryonic development of the limbs in vertebrates, specifically SHH. For a while the mechanism of which the limb was patterned on the anterior to posterior axis was quite unknown. Early studies had shown that grafting posterior wing bud cells to the anterior region of the wing bud in a chick embryo, an equal amount of extra digits was produced to that of which was normally produced, and in a mirror image pattern<ref name="PMID4390734"><pubmed>4390734</pubmed></ref>. This showed that the pattern of which the digits were produced were polarized with respect to that of the graft from the limb bud, which has become to be described as the zone of polarizing activity (ZPA). Further studies mapped the ZPA, by showing the area of the wing bud on the chick with the highest polarizing activity to be the posterior margin of the wing bud<ref name="PMID4719010"><pubmed>4719010</pubmed></ref>. Furthermore, studies later on found that the amount or concentration of ZPA cells grafted played a role in the amount of digits induced and how polarized they were<ref name="PMID7453825"><pubmed>7453825</pubmed></ref>. This ultimately gave rise to studies regarding a potential morphogen, which could potentially provide this concentration dependent activity of polarization when it comes to the limb bud. Studies to find this morphogen led to the discover of the ability for retinoic acid to mimic the polarizing action of the ZPA when applied locally to the limb bud<ref name="PMID7070499"><pubmed>7070499</pubmed></ref>. This was found to be due to the induction of a second morphogen known as SHH, where when cells that express SHH are grafted onto the limb bud, polarized digit development is induced<ref name="PMID7720566"><pubmed>7720566</pubmed></ref>.<br />
<br />
====Polarizing activity of sonic hedgehog====<br />
[[File:Digit patterning based on time and concentration of SHH exposure.jpg|thumb|450px|Regions of the limb bud and the digits they form into categorised into how they interact with SHH. The red and green dot represent the 5th and 4th digit region respectively.]]<br />
More recent studies have sought to elucidate how SHH mediates such a polarizing effect in terms of digit identification and its underlying mechanism. It has been suggested that such an effect is heavily concentration dependent similar to that of when transplanting the chick wing bud ZPA cells, acting in a dose dependent matter, due to the ability of SHH to modulate signaling at long ranges via diffusion<ref name="PMID11389830"><pubmed>11389830</pubmed></ref>. This implies that a gradient of varying concentrations of SHH diffused through the mesenchyme of the limb bud leads to the identification of posterior and anterior digits.<br />
<br />
Current research has also suggested that not only is the concentration gradient of SHH important for the patterning of the digits, but also the temporal gradient, being the length of time of exposure of SHH to the mesenchyme of the limb bud. Studies have shown in mice that of the 5 digits, polarization from the posterior end, being digit 5, to the anterior end being digit 1 are due to different mechanisms. Digits 5 and 4 have been shown to be comprised of the SHH expressing cells and thus both experience maximal levels of SHH, and thus cannot be distinguished on the basis of a concentration gradient. As a result, temporal gradients are employed, where the expression of SHH in both regions that become the digits vary, where studies have shown that SHH expression in the primordium of digit 5 is maintained longer than that in digit 4 gradient <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>. When it comes to digit 3 and 2, there is differentiation based on the concentration gradient of SHH from the ZPA, where due to the ZPA being further away to digit 2 than 3, the concentration of SHH will be higher at 3<ref name="PMID15315763"><pubmed>15315763</pubmed></ref> <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>. In terms of digit 1, the levels of SHH are so low at this point that it is said to be SHH independent, and actually reliant on the absence of SHH for normal differentiation. With regards to how SHH actually mediates its action, it is thought to be by a balance between the transcription factor Gli3 and SHH expression, which activates Gli1, Gli2 and Gli3 repressor, effectively counteracting Gli3. Gli3 is considered to promote the inhibition of digit formation and identification, while the downstream targets of SHH are thought to promote it<ref name="PMID17400206"><pubmed>17400206</pubmed></ref>.<br />
<br />
Other research has also shown the possibility of SHH signaling as a way to prime the posterior mesenchyme and induce the production of bone morphogenetic protein 2 (bmp2), which is thought to be the morphogen creating the chemical gradient for digit identification<ref name="PMID10704381"><pubmed>10704381</pubmed></ref>. Overall the mechanism at which SHH work to pattern the posterior anterior axis of the limb bud is still relatively unknown, and further research is being conducted to elucidate how the underlying mechanisms such as the downstream targets of SHH affect digit formation.<br />
<br />
=== Neural development ===<br />
<br />
=== Organogenesis ===<br />
The Hedgehog Signalling pathway is a pathway sending information to embryonic cells which plays an especially important role in the regulation of organogenesis. These processes include the organization of the brain (craniofacial) and the growth of appendages with further studies implicating the Hedgehog Signalling pathway in the development of the small intestine, lungs and the pancreas.<br />
<br />
== Mechanism ==<br />
<br />
=== Processing of precursor ===<br />
<br>[[File:Processing of Hh precurosr.jpg|thumb|250px|Summary of the steps in the processing of the Hh protein precursor into a functional signalling molecule]]<br />
Hedgehog (Hh) proteins are produced as precursors, which must be processed by the cells producing it before being able to perform its signalling function. The process by which the Hh protein is processed begins with its signal sequence at its N terminus directing the translocation of the precursor into the endoplasmic reticulum, where it is removed via signal peptidase<ref><pubmed>1394430</pubmed></ref>. This process allows the C terminus of the Hh protein to catalyze the cleavage and addition of cholesterol on itself to form a C terminal processing domain and an N terminal processing domain associated with a cholesterol group on its C terminus<ref><pubmed>21357747</pubmed></ref>. The portion associated with the cholesterol will go on to form the signalling molecule, while the C terminal processing domain has no known signalling function<ref><pubmed>8824192</pubmed></ref>. <br />
<br />
At this point the Hh protein associated with the cholesterol is able to perform its signalling action, but further modification is still required to ensure efficient signalling. This occurs when the cholesterol group attached to the Hh protein associates with the plasma membrane of the cell, which allows for the addition of a palmitic acid moiety to the N terminal of the protein by an acyl-transferase known as skinny hedgehog<ref><pubmed>11486055</pubmed></ref>. Studies have shown that such an addition allows for an increase in potency in signalling of Hh proteins of 30-fold over its form without palmitic acid added<ref><pubmed>9593755</pubmed></ref>. From this point the Hh protein is now fully active and can either remain associated to the plasma membrane of the cell for autocrine action or be secreted for paracrine action.<br />
<br />
=== Mechanism of signalling ===<br />
<br />
==== ''Drosophila melanogaster'' ====<br />
<br>[[File:Hh Signalling Pathway.jpg|thumb|600px|Steps regarding the processing of the hh protein precursor into the fully functional signalling molecule.]]<br />
<br />
The Hh signaling pathway has been well studied in ''Drosophila melanogaster'', and has been shown the be conserved to an extent across it and mammals making the species a suitable model for Hh signalling in humans<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. In ''Drosophila melanogaster'', the Hh pathway begins when the Hh proteins bind to the extracellular domain of the transmembrane protein known as Patched (PTC) to inactivate it. This inactivation occurs by Hh trapping PTC in an inactive conformational state<ref><pubmed>27647915</pubmed></ref>. After binding of Hh occurs to PTC and it is inactivated, the receptor and Hh protein is thought to be endocytosed by the cell where they undergo lysosomal degradation in order to limit Hh concentration, thus limiting its spread to other cells and PTC activity<ref name="PMID15102702"><pubmed>15102702</pubmed></ref>. In the absence of Hh, PTC acts to suppress the expression of the Smoothened (SMO), a G-protein coupled receptor like receptor, and thus its signaling. How PTC achieves this inhibition of SMO is currently unclear. Studies have suggested that due to the highly phosphorylated nature of SMO when active, that PTC acts to dephosphorylate SMO in order to repress its signaling. It is thus that binding of Hh to PTC reduces PTCs ability to promote dephosphorylation of SMO, leading to its increased activity and expression on the cell surface <ref name="PMID10966113"><pubmed>10966113</pubmed></ref>. It is thought that the phosphorylation required to activate SMO are dependent on protein kinase A (PKA) and casein kinase I (CKI) <ref><pubmed>15616566 </pubmed></ref>.<br />
<br />
This overall increased phosphorylation of SMO due to a repression of PTC activity by Hh leads to an accumulation of SMO on the cell surface, which collectively allows for SMO to exert its activity. Most importantly phosphorylation also disrupts intramolecular electrostatic interactions between SMO molecules which switches the molecule into its active conformational state <ref><pubmed>17960137 </pubmed></ref>. Generally, SMO has been shown to have very little signal transducing ability, and thus this accumulation allows it to jointly transduce as substantial signal. This occurs by the C terminus of SMO on the intracellular domain interacting with the kinesin like protein Costal-2 (Cos2), which is thought to bind to microtubules in order to acts as a scaffolding protein <ref><pubmed>18691888 </pubmed></ref>. Then the kinase known as Fused (Fu) binds to Cos2, which phosphorylates Suppressor of Fused (SUFU) to inhibit it. Without this inhibition SUFU goes onto prevent the translocation of the transcriptional factor Cubitus interruptus (Ci) into the nucleus by leading to its phosphorylation, and subsequently its partial cleavage via the proteosome. The partial cleavage of Ci leaves a lower molecular weight protein known as Ci repressor (CiR) or Ci75, which translocates into the nucleus and acts to repress the target genes of the Hh signalling pathway via Ci<ref><pubmed>9215627</pubmed></ref>. Thus overall inhibition of SUFU increases the amount of Ci entering into the nucleus of the cell, and activating transcription of target genes of the Hh pathway<ref><pubmed>10952898 </pubmed></ref>.<br />
<br />
At this point Ci is able to activate the transcription of various genes, which include importantly the ''ptc'' gene, which encodes the PTC receptor. It is thus as a result of this, that PTC expression will be increased in response to Hh pathway induction, which negatively feeds back to reduce Ci signaling induction, in order to maintain homeostasis and regulate the intensity and duration of the signaling from Hh<ref><pubmed>9053330</pubmed></ref>. Furthermore the ''wg'' gene, encoding the wingless protein is also activated by Ci, which leads to activation of the Wnt pathway via the Frizzled receptor in adjacent cells expressing the gene ''engrailed'' <ref><pubmed>9502727</pubmed></ref> <ref><pubmed>10457026</pubmed></ref>. This overall stabalizes the boundaries between the segments of the developing ''Drosophila melanogaster'' signalled by the gene ''engrailed''<ref><pubmed>3282172</pubmed></ref>.<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=w1xXD9kss2w</html5media><br />
<br><br><br />
An overview of the hedgehog signalling pathway in ''Drosophila''<ref>YouTube. (2016). The Hedgehog signalling pathway in Drosophila online Available at: https://www.youtube.com/watch?v=w1xXD9kss2w</ref>.<br />
<br />
==== Mammals ====<br />
<br />
Although the Hh signaling pathway has been conserved across species to an extent <ref name="PMID8595881"><pubmed>8595881</pubmed></ref>, key differences exist when observing the pathway within mammalian tissue in contrast to that which has been studied in ''Drosophila melanogaster''. In mammalian cells and all other vertebrates, Hh signalling is dependent on an organelle known as the primary cilia, which are projections outwards from the cells surface. The importance of such an organelle in the signalling pathway comes as a result of PTC1, one of the two PTC receptor homologs in mammals, that binds to the Hh homolog Sonic Hh (Shh), exists within the cilia<ref><pubmed>17641202</pubmed></ref>. The mechanism of action of SMO inhibition and activation is poorly understood currently, but evidence has suggested that PTC1 acts to inhibit SMO when unbound to Shh by acting as a pump to remove oxysterols from the cilia into the extracellular space. <ref><pubmed>PMC1462959</pubmed></ref>. These oxysterols are normally thought to bind and accumulate around the SMO receptors, which in turn prevents internalization and deactivation of SMO, leading to it accumulating on the apical primary cilia<ref><pubmed>16136078</pubmed></ref>. Other studies have also suggested that Shh has a role in increasing phosphorylation of SMO, which is required for it to accumulate as well on the cilia<ref><pubmed>21695114</pubmed></ref>. Overall the net action of Shh initially is believed to cause accumulation of SMO at the cilia by inhibiting PTCH1 and phosphorylation of SMO.<br />
<br />
How SMO acts next is relatively unknown but, it has been shown to promote the disassociation between SUFU and Gli3 transcription factor, which allows Gli to be transported to the nucleus to activate effector genes of the pathway. Gli is normally bound in the cytoplasm to SUFU, where SUFU promotes the partial degradation of Gli into its repressor form, similar to that in the fruit fly model<ref><pubmed>20360384</pubmed></ref>. Alongside this, Kif7, a Cos2 homolog, has been shown to migrate to the apex of the cilium in response to SMO accumulation at the cilium, where it has been postulated to also promote disassociation of SUFU and Gli<ref><pubmed>19592253</pubmed></ref>. On the other hand, Kif7 is also thought to play an inhibitory role for the signaling pathway as when it is localized at the base of the cilia in the absence of Hh signaling and traffics Gli factors away from the cilia<ref><pubmed>19666503</pubmed></ref>. This all leads to an accumulation of active Gli transcription factors which migrate to the nucleus in order either inhibit or activate gene transcription in response to Hh signaling.<br />
<br />
== Animal models ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br />
Hedgehog (Hh) protein signal was initially discovered through experimentation on the fruit fly, "Drosophila melanogaster". It is through this model that we are able to discover not only the functional components of this pathway but also understand its role in embryonic development. Through application of this information on the human biological system we are able to find the cause and thus potential treatments of defects and diseases caused by interruption or mutation of the Hedgehog signalling pathway. <br />
<br />
Upon further research on Drosophila it was found that Hh may play a role in germ cell proliferation and in particular, may control the proliferation and activity of somatic cells found within the germarium, which is the most anterior structure within the Drosophila ovary. <ref>Ovaries (Drosophila) definition. (2016). Groups.molbiosci.northwestern.edu. Retrieved 10 September 2016, from http://groups.molbiosci.northwestern.edu/holmgren/Glossary/Definitions/Def-D/Drosophila_Ovaries.html</ref> Thus, the Hh signalling pathway is vital in egg chamber formation and its consequent envelopment, budding and polarisation. It has also been observed that somatic cell proliferation is dependent on this pathway and thus, the number of pre-follicle cells is subject to the effect of the Hh signalling pathway. <ref><pubmed>8620839</pubmed></ref> Further studies have also indicated the role played by this pathway in activating the Epidermal growth factor receptor (EGFR) signalling pathway as seen in the induction of EGFR by Hh in Drosophila head development. <ref><pubmed>10331974</pubmed></ref> In addition, research on Drosophila has indicated the direct effect of Hh signalling on tracheal branch patterning. <ref><pubmed>11290298</pubmed></ref><br />
<br />
Despite ongoing research on "Drosophila melanogaster" to uncover the workings of the Hedgehog signalling pathway, further research is needed to confirm and further current findings. In addition, it is evident that it is through the study of these fruit flies that we are able to gain a basis of understanding of the causes of certain human diseases and thus propel research into treatments for sufferers. <br />
<br />
===Blockage of Shh Signalling in Forebrain Neuroectoderm of Chick Embryos===<br />
<br />
The Hedgehog signalling pathway plays a significant role in embryonic development, particularly of the forebrain. Due to its role in development of craniofacial features by contributing to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm, a disruption in this pathway can result in a variety of birth deformities including holoprosencephaly (HPE), where the prosencephalon (forebrain) fails to divide into 2 separate hemispheres, telencephalon and diencephalon <ref>Holoprosencephaly - NORD (National Organization for Rare Disorders). (2016). NORD (National Organization for Rare Disorders). Retrieved 10 September 2016, from http://rarediseases.org/rare-diseases/holoprosencephaly/</ref>, as well as cleft lip and palate. The function of Sonic Hedgehog (Shh) and its signalling pathway on the formation of forebrain neuroectoderm was studied in chick embryos.<br />
<br />
It was found that the disruption of Shh signalling in the neural tube of chick embryos resulted in the lack of division of the forebrain into the diencephalon and telencephalon. This is in fact, as stated earlier, the fundamental cause of the rare condition, holoprosencephaly. It was discovered that the Shh signalling pathway in the diencephalon was responsible for gene expression in the telencephalon. <br />
<br />
In addition, through experimentation on chick embryos it was found that through Shh signalling the development of the forebrain regulates and controls facial morphogenesis, particularly of the upper and middle face. Therefore, interference with Shh signalling in the forebrain prevents this intrinsic communication, thus hindering Shh expression in facial ectoderm. This results in brain malformation accompanied by facial disfiguration as seen in patients suffering from HPE. Other malformations caused by blockage of Shh signalling in craniofacial development include, hypotelorism (decreased space between the orbits), growth restriction as well as cleft lip and palate as mentioned previously. <br />
<br />
A commonality discovered among all forms of Shh signalling disruption was two facial defects, “the loss of mediolateral expansion of the face and absence of proximodistal outgrowth of the frontonasal prominence”<ref><pubmed>15979605</pubmed></ref> (Ralph et al., 2005). Through reference to studies performed on chick and mice embryos, it was found that Shh signalling is particularly vital in development of maxillary and frontonasal components of the cranium.<br />
<br />
This breakthrough study on the inhibition of Shh signalling in chick embryos has significantly filled the gap in our understanding of the Sonic Hedgehog signalling pathway. It is evident that this pathway is crucial in the development of the forebrain and in turn regulates and controls the development of the facial skeleton. This is further proven through the observation that in the event of Shh signalling inhibition there is a development of craniofacial malformations.<br />
<br />
=== Shh knockout mice ===<br />
<br />
Extensive research on Shh knockout mice allowed discovery of the roles of Shh in embryonic development and patterning of the limb buds and sclerotomes, and maintenance of the notochord. <ref><pubmed>8837770</pubmed></ref> These mice expressed defects in the cephalic neural tube with the fusion of telencephalic and optic vesicles. Through this research it is evident that Shh is partially responsible for the subdivision of the eye field through forebrain optic stalk development, along with formation of the ventral midline. It is these forebrain abnormalities established in the absence of Shh that results in congenital malformations of holoprosencephaly, development of a single nasal chamber and other facial defects in humans. <br />
<br />
The absence of the vertebral column including, the intervertebral discs and vertebrae along with the medial regions of the ribs were observed within Shh knockout mice. This lack of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population (Chiang et al., 1996). In addition, though the role of Shh in patterning the anterior-posterior limb axis is evident through anterior limb bud cell death in the absence of Shh, it is also responsible for the development of proximal-distal limb segments, particularly in the patterning of structures at the level of or distal to the latent elbow and knee joints. <ref><pubmed>11476582</pubmed></ref> This was perceived after observing the incomplete formation of distal limb structures with abnormal anterior-posterior axis formation (Chiang et al., 2001). Thus, Shh knockout mice provide great insight into the functions of Shh in embryonic development and the abnormalities formed in the absence of this signalling protein. <br />
<br />
== Clinical Significance ==<br />
<br />
===Gorlin Syndrome===<br />
[[File:1 week year old newborn girl with cleft lip and palate.png|thumb|An image of a 1 week year old newborn girl with cleft lip and palate]]<br />
Gorlin syndrome, also known as nevoid basal cell carcinoma syndrome, is a heritable disease resulting from heterozygousity in Hh receptor, Patched (PTC). The PTC gene encodes a protein which binds sonic hedgehog (Shh) and it is this binding which inhibits the Hh signalling pathway. However mutation of PTC leads to activation of the pathway <ref><pubmed>9620294</pubmed></ref>. The syndrome is characteristic of skin cancer basal cell carcinoma and cerebellum cancer medulloblastoma. 1-2% of medulloblastomas and 0.5% of basal cell carcinomas are attributable to the disease. Patients present with craniofacial and brain abnormalities such as cleft palate, strabismus, macrocephaly, abnormal development of the corpus callosum and frontal bossing, with an overall overgrown appearance. Skeletal defects such as of the shoulder, ribs and vertebrae are often seen, as well immobile thumbs and polydactyly, which is a deformity of the hand or feet in which they have one or more extra fingers or toes. Apart from physical anomalies, patients have an increased risk of tumours throughout the body including cardiac, ovarian fibromas, ovarian dermoid cysts, meningiomas, and fibrosarcomas. Additionally with time, patients eventually undergo intracranial calcification and dyskeratotic pitting of the hands and feet whereby skin cells prematurely convert to keratin <ref><pubmed>8681379</pubmed></ref>.<br />
<br />
===Holoprosencephaly===<br />
<br>[[File:Semilobar holoprosencephaly.jpg|thumb|240px|MRI of fore brain depicting semilobar holoprosencephaly]]<br />
Holoprosencephaly (HPE) is a congenital disease caused by incomplete division of the prosencephalon (embryonic forebrain) into separate lobes of the cerebral hemispheres. The Shh gene has been identified as a HPE-causing gene however recent evidence has also investigated into the PTC gene, which acts to repress Shh signalling. A gain in repressive action of PTC is seen, leading to decreased Shh signalling, and thus HPE <ref><pubmed>11941477</pubmed></ref>. Clinical expression is variable between patients and is dependent upon the 3 forms of increasing severity: lobar, semi-lobar and alobar HPE, where patients can present with right and left ventricles however with a continuous frontal cortex in lobar HPE, to carrying a single cerebral ventricle in alobar HPE. Along with forebrain abnormalities, facial anomalies are also seen including midline cleft lip and/or flat nose, ocular hypotelorism characteristic of a small distance between the eyes. In severe rare cases of cyclopia, a non-functioning nose may be observed in the form of proboscis and the patient may present with a single eye at the root of the nose <ref><pubmed>20583177</pubmed></ref>. Furthermore, patients with HPE often develop a large number of medical issues including epilepsy, mental retardation, thyroid and adrenal hypoplasia due to lack of hypothalamus or pituitary gland development, and diabetes insipidus.<br />
<br />
===Medulloblastoma===<br />
Medulloblastoma is a cancerous tumour of the cerebellum where the cells of origin are the granular cell precursors found in the neonatal cerebellum, explaining its high prevalence in children <ref><pubmed>19171780</pubmed></ref>. Commonly, medulloblastomas are found deep in the cerebellum along the midline, however with desmoplastic medulloblastomas, they are found more laterally and superficial. As seen previously with Gorlin syndrome and holoprosencephaly, PTC is also associated with the development of medulloblastoma, and misregulation of Hh-PTC signalling in cells of the external germinal layer, the layer found on the surface of the cerebellum, is thought to give rise to the tumour. In experimental studies, it has been discovered that PTC is highly transcribed in medulloblastomas and in approximately 30% of PTC heterozygous mice the tumour develops <ref><pubmed>9205058</pubmed></ref> <ref><pubmed>9262482</pubmed></ref>. In patients with medulloblastoma, often children, the most common symptoms seen are vomiting, ataxia, psychomotor regression, drowsiness and anorexia. With age, patients are seen to get more frequent headaches, and show psychological symptoms such as behavioural problems, poor performance in school, and anxiety. In patients exhibiting life-threatening symptoms due to increased intracranial hypertension, bradycardia, convulsions and coma are often seen <ref><pubmed>21537925</pubmed></ref>.<br />
<br />
"Watch below for a breakdown on Hedgehog's role in Tumour Development!"<br />
<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=gFWO3I-oqsE</html5media><br />
<br><br><br />
An overview of the Hedgehog Signalling Pathway in Tumour Development<ref>YouTube. (2016). The Hedgehog Signaling in the Tumor Microenvironment - Research Hedgehog online Available at: https://www.youtube.com/watch?v=gFWO3I-oqsE</ref>.<br />
<br />
<br />
<br />
== Current research ==<br />
<br />
==Quiz==<br />
<br />
<quiz display=simple><br />
<br />
{1. Which of the following are the reasons that are thought to allow for the patterning of digits in vertebrates.<br />
|type="[]"}<br />
+ &nbsp;Concentration gradient of sonic hedgehog.<br />
+ &nbsp;Temporal gradient of sonic hedgehog.<br />
- &nbsp;The varying homologs of the hedgehog proteins .<br />
- &nbsp;The length of the hedgehog molecule.<br />
+ &nbsp;No sonic hedgehog signalling.<br />
- &nbsp;The type of cholesterol attached to the hedgehog molecule.<br />
||<br> For differentiation of the individual digits in mice to occur it is thought that each digit requires a different signalling mechanism. Digits 5 and 4 which are most posterior, are derived from the region around the zone of polarising area which contain Shh secreting cells, meaning these regions will experience a saturation of Shh signalling and cannot be differentiated by Shh concentration. As a result it is thought that these digits are identfied based on the temporal gradient, meaning that the length of which Shh is expressed in these regions differentiates the digits from one another with digit 5 expressing Shh for longer. Digits 3 and 2 are further away but still receive Shh signalling due to the diffusible nature of Shh from the ZPA, which forms a concentration gradient. This means the the concentration at digit 2 will be less than digit 3 due to being further away from the ZPA and thus can be differentiated from one another based on this concentration. Finally the digit 1 is differentiated on the basis of not receiving any Shh signalling at all. Thus it is a combination of concentration gradient of Shh, temporal gradient of Shh, and independence from Shh.<br />
<br />
{2. Which of the following are correct with regards to the hedgehog signalling pathway in ''Drosophila''.<br />
|type="[]"}<br />
-&nbsp;It occurs at the cillum on the cell surface.<br />
-&nbsp;Hedgehog protein binding to the Patched receptor activates it to inhibit Smoothened.<br />
+&nbsp;Hedgehog protein binding to the Patched recetpor inhibits it to activate Smoothened. <br />
+&nbsp;Inhibition of SUFU is critical in allowing Ci to translocate into the nucles and activate downstream targets of the hedgehog pathway.<br />
-&nbsp;The pathway contains 3 homologs including sonic hedgehog, Indian hedgehog, and desert hedgehog.<br />
-&nbsp;The hedgehog protein is initially produced in its fully active form.<br />
||<br> In terms of how the hedgehog protein acts to produce its effect, it must first bind to Patched which activity is inhibiting Smoothened in the absence of the hedgehog protein. The protein acts to trap Patched in its inactive confirmational state cause internalisation and eventually degradation of the receptor. This relives the dephosporylation of the Smoothened, usually induced by Patched, allowing it to accumulate phosphate groups and thus activate. With regards to Ci translocation, SUFU usually inhibits this by leading to phosphorylation of Ci and eventually its cleavage into Ci repressor. During the activation of the hedgehog pathway there is a binding of Fused to Cos2 which phosphorylates SUFU to inactivate it, allowing Ci to translocate into the nucleus and activate downstream targets.<br />
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<br />
==Glossary==<br />
<br />
{| class="pretty table"<br />
|-<br />
|Term<br />
|Definition<br />
|-<br />
|Desert hedgehog (Dhh)<br />
|A homolog of the ''Drosophila'' hedgehog protein, which is expressed most prominently in the gonads of vertebrates, where it plays a possible role in regulating spermatogenesis. <br />
|-<br />
|Hedgehog (Hh) protein<br />
|A signalling protein widely expressed in the tissue during embryonic development of vertebrates and some other species such as ''Drosophila'', and acts to pattern and develop tissue. The protein is the primary mediator of the pathway.<br />
|-<br />
<br />
|Indian hedgehog (Ihh)<br />
|A signalling protein that is a homolog of the ''Drosophila'' hedgehog protein, that primarily acts in regions where there is endochondrial ossification to aid in the maturation of chondrocytes.<br />
|-<br />
|Limb bud<br />
|A structure formed during early embryonic development consisting of ectoderm and mesenchyme representing the early limbs, where signalling processes in the bud will eventually lead to the out growth and patterning of the bud.<br />
|-<br />
|Sonic hedgehog (Shh)<br />
|The most widely expressed homolog of the ''Drosophila'' hedgehog protein found in vertebrates, playing a key role in embryonic development of humans.<br />
|-<br />
|Zone of polarizing activity (ZPA)<br />
|The posterior region of the limb bud mesenchyme, which aids in the signalling of it to pattern the posterior anterior axis with respect to the digits through mediators such as sonic hedgehog.<br />
|-<br />
|}<br />
<br />
===Additional Glossary Links===<br />
[[A|A]] | [[B|B]] | [[C|C]] | [[D|D]] | [[E|E]] | [[F|F]] | [[G|G]] | [[H|H]] | [[I|I]] | [[J|J]] | [[K|K]] | [[L|L]] | [[M|M]] | [[N|N]] | [[O|O]] | [[P|P]] | [[Q|Q]] | [[R|R]] | [[S|S]] | [[T|T]] | [[U|U]] | [[V|V]] | [[W|W]] | [[X|X]] | [[Y|Y]] | [[Z|Z]] | [[Numbers|#]]<br />
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== References ==</div>
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= Hedgehog signalling pathway =<br />
==Introduction==<br />
[[File:Hedgehog.jpg|thumb|300px|An image of a hedgehog, the animal of which the Hh proteins are named after.]]<br />
The Hedgehog (Hh) signalling pathway is an important part of the early embryo with regards to the patterning and development of the nervous system, limbs and the cranio-facial region in vertebrates and the polarization of the segments in the ''Drosophila'' embryo. It was first identified in 1980 by Christiane Nüsslein-Volhard and Eric Wieschaus, alongside a group of other genes regulating segment polarity in ''Drosophila'' embryonic development<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. The pathway itself consists of Hh proteins, where there are three identified homologs in vertebrates, being sonic hedgehog (SHH), Indian hedgehog (IHH), and desert hedgehog (DHH) <ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. All homologs are expressed at varying levels within different tissues in the body, and also act as a form of redundancy to an extent between one another. <br />
<br />
The signaling pathway is highly conserved between various species<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. and acts via a G protein coupled receptor like receptor, which uninhibited via the action of the Hh proteins. The pathway overall acts via a balance of dephosphorylation<ref name="PMID10966113"><pubmed>10966113</pubmed></ref> and degradation of proteins<ref name="PMID15102702"><pubmed>15102702</pubmed></ref> in order to regulate transcription factor activity to express various genes to carry out its action. The Hh pathway is also highly implicated when it comes to abnormalities in development, as it is implicated in diseases such as holoprosencephaly and cleft lip and palate. Overall Hh signaling pathways play a large role in embryological development, which will be discussed in detail on this page.<br />
<br />
== History ==<br />
{| class="pretty table"<br />
| '''1980'''<br />
|Christiane Nüsslein-Volhard and Eric Wieschaus first identified a group of genes including those related to the Hedgehog signalling pathway and linked them to the segmentation and planning of the embryo in ''Drosophila melanogaster'' by introducing mutagenic substances to the developing embryo<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
| Multiple researchers including Andrew P. McMahon and Clifford Tabin discovered three equivalent homologs in vertebrates of the ''Drosophila melanogaster'' hedgehog gene, known as sonic hedgehog (SHH), desert hedgehog (DHH) and indian hedgehog (IHH), by looking at DNA sequences similar to that of the gene in the fruit fly<ref><pubmed>7916661</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
| Clifford Tabin and his lab identified the role of SHH in localising the limb bud, where they identified protein to be expressed within a region of the limb bud known as the zone of polarising activity (ZPA), showing that SHH is sufficient to induce the production of a ZPA, and thus limb bud formation in chick embryos<ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
| A shared Nobel prize in physiology or medicine was awarded to Christiane Nüsslein-Volhard and Eric Wieschaus for their researching regarding the identification of the developmental genes relating to the formation and patterning of the early embryo via genes.<br />
|-<br />
|'''2003'''<br />
| Studies on SHH function found that it can act as a chemoattractant in the developing embryo spinal cord, to help guide commissural axons to the midline of the floor plate<ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
|}<br />
<br />
== Origin of name ==<br />
<br />
[[File:Bands of denticles in normal and Hh mutant Drosophila embryo.jpeg|thumb|250px|Differences in patterning of the denticle bands in normal and mutated hedgehog gene variant ''Drosophilia'' embryo]]<br />
<br />
The name hedgehog came about when Christiane Nüsslein-Volhard and Eric Wieschaus first identified the group of genes controlling polarization of the segments in the ''Drosophila'' early embryo. They noticed that when they mutated the Hh gene, making it non-functional, that the bands of denticles formed during the early ''Drosophila'' embryo formation became more diffuse as opposed to being distinct normally. The denticles would all clump together forming a single patch on the surface of the embryo, as opposed to normally outlining the distinct segments of the embryo as bands<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. This gave the embryo spiny and prickly look similar to that of the back of a hedgehog.<br />
<br />
From there on in the gene was called the hedgehog gene where homologs in vertebrates discovered along the line kept to this naming structure giving various species of hedgehog names to the genes such as Indian hedgehog, and desert hedgehog, with the exception being sonic hedgehog, which is named after a fictional character in the video game “Sonic the Hedgehog”.<br />
<br />
== Function ==<br />
===Overview===<br />
{| class="pretty table"<br />
|'''Hedgehog protein homolog'''<br />
|'''Function'''<br />
|-<br />
| Sonic hedgehog ||<br />
*Expressed in zone of polarizing activity of the limb bud where it plays a role in helping to pattern the anterior and posterior aspect of the limbs <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
*Based on time and concentration of SHH due to diffusion from the point of secretion in the limb bud, SHH also plays a role in determining digit identity <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>.<br />
*Acts as a chemoattractant to guide commissural axons in the floor plate of the neural tube towards the midline <ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
*Patterns the developing cusps of the teeth and their relative positions in the jaw, and is also essential for the growth of the teeth <ref name="PMID11044393"><pubmed>11044393</pubmed></ref>.<br />
*SHH released from the notochord acts to induce formation of the floor plate, motor neurons, and dopaminergic neurons, as well as signalling the induction of the ventral cell types in the neural tube <ref name="PMID8790332"><pubmed>8790332</pubmed></ref>.<br />
|-<br />
| Desert hedgehog ||<br />
*Plays a possible role in regulating spermatogenesis as due to the highly localised expression in the testes by pre-Sertoli cells, and the fact that mice with no DHH present are infertile, with no mature spermatozoa <ref name="PMID8805249"><pubmed>8805249</pubmed></ref>. <br />
*DHH derived from Schwann cells signal development of peripheral nerves, by inducing the production of a connective tissue sheath around them <ref name="PMID10482238"><pubmed>10482238</pubmed></ref>.<br />
|-<br />
| Indian hedgehog ||<br />
*Aid in the signalling of proliferating chondrocytes to undergo hypertrophic differentiation during endochondral ossification<ref name="PMID8662546"><pubmed> 8662546</pubmed></ref>.<br />
*Plays a key role in yolk sac angiogenesis, as seen in studies where an absence of IHH leads to death of the embryo due to poor yolk sac vasculature <ref name="PMID11807029"><pubmed>11807029</pubmed></ref>.<br />
|}<br />
<br />
===Limb development===<br />
<br />
====Research background====<br />
<br />
The hedgehog signalling pathway plays a significant role with regards to the embryonic development of the limbs in vertebrates, specifically SHH. For a while the mechanism of which the limb was patterned on the anterior to posterior axis was quite unknown. Early studies had shown that grafting posterior wing bud cells to the anterior region of the wing bud in a chick embryo, an equal amount of extra digits was produced to that of which was normally produced, and in a mirror image pattern<ref name="PMID4390734"><pubmed>4390734</pubmed></ref>. This showed that the pattern of which the digits were produced were polarized with respect to that of the graft from the limb bud, which has become to be described as the zone of polarizing activity (ZPA). Further studies mapped the ZPA, by showing the area of the wing bud on the chick with the highest polarizing activity to be the posterior margin of the wing bud<ref name="PMID4719010"><pubmed>4719010</pubmed></ref>. Furthermore, studies later on found that the amount or concentration of ZPA cells grafted played a role in the amount of digits induced and how polarized they were<ref name="PMID7453825"><pubmed>7453825</pubmed></ref>. This ultimately gave rise to studies regarding a potential morphogen, which could potentially provide this concentration dependent activity of polarization when it comes to the limb bud. Studies to find this morphogen led to the discover of the ability for retinoic acid to mimic the polarizing action of the ZPA when applied locally to the limb bud<ref name="PMID7070499"><pubmed>7070499</pubmed></ref>. This was found to be due to the induction of a second morphogen known as SHH, where when cells that express SHH are grafted onto the limb bud, polarized digit development is induced<ref name="PMID7720566"><pubmed>7720566</pubmed></ref>.<br />
<br />
====Polarizing activity of sonic hedgehog====<br />
[[File:Digit patterning based on time and concentration of SHH exposure.jpg|thumb|450px|Regions of the limb bud and the digits they form into categorised into how they interact with SHH. The red and green dot represent the 5th and 4th digit region respectively.]]<br />
More recent studies have sought to elucidate how SHH mediates such a polarizing effect in terms of digit identification and its underlying mechanism. It has been suggested that such an effect is heavily concentration dependent similar to that of when transplanting the chick wing bud ZPA cells, acting in a dose dependent matter, due to the ability of SHH to modulate signaling at long ranges via diffusion<ref name="PMID11389830"><pubmed>11389830</pubmed></ref>. This implies that a gradient of varying concentrations of SHH diffused through the mesenchyme of the limb bud leads to the identification of posterior and anterior digits.<br />
<br />
Current research has also suggested that not only is the concentration gradient of SHH important for the patterning of the digits, but also the temporal gradient, being the length of time of exposure of SHH to the mesenchyme of the limb bud. Studies have shown in mice that of the 5 digits, polarization from the posterior end, being digit 5, to the anterior end being digit 1 are due to different mechanisms. Digits 5 and 4 have been shown to be comprised of the SHH expressing cells and thus both experience maximal levels of SHH, and thus cannot be distinguished on the basis of a concentration gradient. As a result, temporal gradients are employed, where the expression of SHH in both regions that become the digits vary, where studies have shown that SHH expression in the primordium of digit 5 is maintained longer than that in digit 4 gradient <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>. When it comes to digit 3 and 2, there is differentiation based on the concentration gradient of SHH from the ZPA, where due to the ZPA being further away to digit 2 than 3, the concentration of SHH will be higher at 3<ref name="PMID15315763"><pubmed>15315763</pubmed></ref> <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>. In terms of digit 1, the levels of SHH are so low at this point that it is said to be SHH independent, and actually reliant on the absence of SHH for normal differentiation. With regards to how SHH actually mediates its action, it is thought to be by a balance between the transcription factor Gli3 and SHH expression, which activates Gli1, Gli2 and Gli3 repressor, effectively counteracting Gli3. Gli3 is considered to promote the inhibition of digit formation and identification, while the downstream targets of SHH are thought to promote it<ref name="PMID17400206"><pubmed>17400206</pubmed></ref>.<br />
<br />
Other research has also shown the possibility of SHH signaling as a way to prime the posterior mesenchyme and induce the production of bone morphogenetic protein 2 (bmp2), which is thought to be the morphogen creating the chemical gradient for digit identification<ref name="PMID10704381"><pubmed>10704381</pubmed></ref>. Overall the mechanism at which SHH work to pattern the posterior anterior axis of the limb bud is still relatively unknown, and further research is being conducted to elucidate how the underlying mechanisms such as the downstream targets of SHH affect digit formation.<br />
<br />
=== Neural development ===<br />
<br />
=== Organogenesis ===<br />
The Hedgehog Signalling pathway is a pathway sending information to embryonic cells which plays an especially important role in the regulation of organogenesis. These processes include the organization of the brain (craniofacial) and the growth of appendages with further studies implicating the Hedgehog Signalling pathway in the development of the small intestine, lungs and the pancreas.<br />
<br />
== Mechanism ==<br />
<br />
=== Processing of precursor ===<br />
<br>[[File:Processing of Hh precurosr.jpg|thumb|250px|Summary of the steps in the processing of the Hh protein precursor into a functional signalling molecule]]<br />
Hedgehog (Hh) proteins are produced as precursors, which must be processed by the cells producing it before being able to perform its signalling function. The process by which the Hh protein is processed begins with its signal sequence at its N terminus directing the translocation of the precursor into the endoplasmic reticulum, where it is removed via signal peptidase<ref><pubmed>1394430</pubmed></ref>. This process allows the C terminus of the Hh protein to catalyze the cleavage and addition of cholesterol on itself to form a C terminal processing domain and an N terminal processing domain associated with a cholesterol group on its C terminus<ref><pubmed>21357747</pubmed></ref>. The portion associated with the cholesterol will go on to form the signalling molecule, while the C terminal processing domain has no known signalling function<ref><pubmed>8824192</pubmed></ref>. <br />
<br />
At this point the Hh protein associated with the cholesterol is able to perform its signalling action, but further modification is still required to ensure efficient signalling. This occurs when the cholesterol group attached to the Hh protein associates with the plasma membrane of the cell, which allows for the addition of a palmitic acid moiety to the N terminal of the protein by an acyl-transferase known as skinny hedgehog<ref><pubmed>11486055</pubmed></ref>. Studies have shown that such an addition allows for an increase in potency in signalling of Hh proteins of 30-fold over its form without palmitic acid added<ref><pubmed>9593755</pubmed></ref>. From this point the Hh protein is now fully active and can either remain associated to the plasma membrane of the cell for autocrine action or be secreted for paracrine action.<br />
<br />
=== Mechanism of signalling ===<br />
<br />
==== ''Drosophila melanogaster'' ====<br />
<br>[[File:Hh Signalling Pathway.jpg|thumb|600px|Steps regarding the processing of the hh protein precursor into the fully functional signalling molecule.]]<br />
<br />
The Hh signaling pathway has been well studied in ''Drosophila melanogaster'', and has been shown the be conserved to an extent across it and mammals making the species a suitable model for Hh signalling in humans<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. In ''Drosophila melanogaster'', the Hh pathway begins when the Hh proteins bind to the extracellular domain of the transmembrane protein known as Patched (PTC) to inactivate it. This inactivation occurs by Hh trapping PTC in an inactive conformational state<ref><pubmed>27647915</pubmed></ref>. After binding of Hh occurs to PTC and it is inactivated, the receptor and Hh protein is thought to be endocytosed by the cell where they undergo lysosomal degradation in order to limit Hh concentration, thus limiting its spread to other cells and PTC activity<ref name="PMID15102702"><pubmed>15102702</pubmed></ref>. In the absence of Hh, PTC acts to suppress the expression of the Smoothened (SMO), a G-protein coupled receptor like receptor, and thus its signaling. How PTC achieves this inhibition of SMO is currently unclear. Studies have suggested that due to the highly phosphorylated nature of SMO when active, that PTC acts to dephosphorylate SMO in order to repress its signaling. It is thus that binding of Hh to PTC reduces PTCs ability to promote dephosphorylation of SMO, leading to its increased activity and expression on the cell surface <ref name="PMID10966113"><pubmed>10966113</pubmed></ref>. It is thought that the phosphorylation required to activate SMO are dependent on protein kinase A (PKA) and casein kinase I (CKI) <ref><pubmed>15616566 </pubmed></ref>.<br />
<br />
This overall increased phosphorylation of SMO due to a repression of PTC activity by Hh leads to an accumulation of SMO on the cell surface, which collectively allows for SMO to exert its activity. Most importantly phosphorylation also disrupts intramolecular electrostatic interactions between SMO molecules which switches the molecule into its active conformational state <ref><pubmed>17960137 </pubmed></ref>. Generally, SMO has been shown to have very little signal transducing ability, and thus this accumulation allows it to jointly transduce as substantial signal. This occurs by the C terminus of SMO on the intracellular domain interacting with the kinesin like protein Costal-2 (Cos2), which is thought to bind to microtubules in order to acts as a scaffolding protein <ref><pubmed>18691888 </pubmed></ref>. Then the kinase known as Fused (Fu) binds to Cos2, which phosphorylates Suppressor of Fused (SUFU) to inhibit it. Without this inhibition SUFU goes onto prevent the translocation of the transcriptional factor Cubitus interruptus (Ci) into the nucleus by leading to its phosphorylation, and subsequently its partial cleavage via the proteosome. The partial cleavage of Ci leaves a lower molecular weight protein known as Ci repressor (CiR) or Ci75, which translocates into the nucleus and acts to repress the target genes of the Hh signalling pathway via Ci<ref><pubmed>9215627</pubmed></ref>. Thus overall inhibition of SUFU increases the amount of Ci entering into the nucleus of the cell, and activating transcription of target genes of the Hh pathway<ref><pubmed>10952898 </pubmed></ref>.<br />
<br />
At this point Ci is able to activate the transcription of various genes, which include importantly the ''ptc'' gene, which encodes the PTC receptor. It is thus as a result of this, that PTC expression will be increased in response to Hh pathway induction, which negatively feeds back to reduce Ci signaling induction, in order to maintain homeostasis and regulate the intensity and duration of the signaling from Hh<ref><pubmed>9053330</pubmed></ref>. Furthermore the ''wg'' gene, encoding the wingless protein is also activated by Ci, which leads to activation of the Wnt pathway via the Frizzled receptor in adjacent cells expressing the gene ''engrailed'' <ref><pubmed>9502727</pubmed></ref> <ref><pubmed>10457026</pubmed></ref>. This overall stabalizes the boundaries between the segments of the developing ''Drosophila melanogaster'' signalled by the gene ''engrailed''<ref><pubmed>3282172</pubmed></ref>.<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=w1xXD9kss2w</html5media><br />
<br><br><br />
An overview of the hedgehog signalling pathway in ''Drosophila''<ref>YouTube. (2016). The Hedgehog signalling pathway in Drosophila online Available at: https://www.youtube.com/watch?v=w1xXD9kss2w</ref>.<br />
<br />
==== Mammals ====<br />
<br />
Although the Hh signaling pathway has been conserved across species to an extent <ref name="PMID8595881"><pubmed>8595881</pubmed></ref>, key differences exist when observing the pathway within mammalian tissue in contrast to that which has been studied in ''Drosophila melanogaster''. In mammalian cells and all other vertebrates, Hh signalling is dependent on an organelle known as the primary cilia, which are projections outwards from the cells surface. The importance of such an organelle in the signalling pathway comes as a result of PTC1, one of the two PTC receptor homologs in mammals, that binds to the Hh homolog Sonic Hh (Shh), exists within the cilia<ref><pubmed>17641202</pubmed></ref>. The mechanism of action of SMO inhibition and activation is poorly understood currently, but evidence has suggested that PTC1 acts to inhibit SMO when unbound to Shh by acting as a pump to remove oxysterols from the cilia into the extracellular space. <ref><pubmed>PMC1462959</pubmed></ref>. These oxysterols are normally thought to bind and accumulate around the SMO receptors, which in turn prevents internalization and deactivation of SMO, leading to it accumulating on the apical primary cilia<ref><pubmed>16136078</pubmed></ref>. Other studies have also suggested that Shh has a role in increasing phosphorylation of SMO, which is required for it to accumulate as well on the cilia<ref><pubmed>21695114</pubmed></ref>. Overall the net action of Shh initially is believed to cause accumulation of SMO at the cilia by inhibiting PTCH1 and phosphorylation of SMO.<br />
<br />
How SMO acts next is relatively unknown but, it has been shown to promote the disassociation between SUFU and Gli3 transcription factor, which allows Gli to be transported to the nucleus to activate effector genes of the pathway. Gli is normally bound in the cytoplasm to SUFU, where SUFU promotes the partial degradation of Gli into its repressor form, similar to that in the fruit fly model<ref><pubmed>20360384</pubmed></ref>. Alongside this, Kif7, a Cos2 homolog, has been shown to migrate to the apex of the cilium in response to SMO accumulation at the cilium, where it has been postulated to also promote disassociation of SUFU and Gli<ref><pubmed>19592253</pubmed></ref>. On the other hand, Kif7 is also thought to play an inhibitory role for the signaling pathway as when it is localized at the base of the cilia in the absence of Hh signaling and traffics Gli factors away from the cilia<ref><pubmed>19666503</pubmed></ref>. This all leads to an accumulation of active Gli transcription factors which migrate to the nucleus in order either inhibit or activate gene transcription in response to Hh signaling.<br />
<br />
== Animal models ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br />
Hedgehog (Hh) protein signal was initially discovered through experimentation on the fruit fly, "Drosophila melanogaster". It is through this model that we are able to discover not only the functional components of this pathway but also understand its role in embryonic development. Through application of this information on the human biological system we are able to find the cause and thus potential treatments of defects and diseases caused by interruption or mutation of the Hedgehog signalling pathway. <br />
<br />
Upon further research on Drosophila it was found that Hh may play a role in germ cell proliferation and in particular, may control the proliferation and activity of somatic cells found within the germarium, which is the most anterior structure within the Drosophila ovary. <ref>Ovaries (Drosophila) definition. (2016). Groups.molbiosci.northwestern.edu. Retrieved 10 September 2016, from http://groups.molbiosci.northwestern.edu/holmgren/Glossary/Definitions/Def-D/Drosophila_Ovaries.html</ref> Thus, the Hh signalling pathway is vital in egg chamber formation and its consequent envelopment, budding and polarisation. It has also been observed that somatic cell proliferation is dependent on this pathway and thus, the number of pre-follicle cells is subject to the effect of the Hh signalling pathway. <ref><pubmed>8620839</pubmed></ref> Further studies have also indicated the role played by this pathway in activating the Epidermal growth factor receptor (EGFR) signalling pathway as seen in the induction of EGFR by Hh in Drosophila head development. <ref><pubmed>10331974</pubmed></ref> In addition, research on Drosophila has indicated the direct effect of Hh signalling on tracheal branch patterning. <ref><pubmed>11290298</pubmed></ref><br />
<br />
Despite ongoing research on "Drosophila melanogaster" to uncover the workings of the Hedgehog signalling pathway, further research is needed to confirm and further current findings. In addition, it is evident that it is through the study of these fruit flies that we are able to gain a basis of understanding of the causes of certain human diseases and thus propel research into treatments for sufferers. <br />
<br />
===Blockage of Shh Signalling in Forebrain Neuroectoderm of Chick Embryos===<br />
<br />
The Hedgehog signalling pathway plays a significant role in embryonic development, particularly of the forebrain. Due to its role in development of craniofacial features by contributing to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm, a disruption in this pathway can result in a variety of birth deformities including holoprosencephaly (HPE), where the prosencephalon (forebrain) fails to divide into 2 separate hemispheres, telencephalon and diencephalon <ref>Holoprosencephaly - NORD (National Organization for Rare Disorders). (2016). NORD (National Organization for Rare Disorders). Retrieved 10 September 2016, from http://rarediseases.org/rare-diseases/holoprosencephaly/</ref>, as well as cleft lip and palate. The function of Sonic Hedgehog (Shh) and its signalling pathway on the formation of forebrain neuroectoderm was studied in chick embryos.<br />
<br />
It was found that the disruption of Shh signalling in the neural tube of chick embryos resulted in the lack of division of the forebrain into the diencephalon and telencephalon. This is in fact, as stated earlier, the fundamental cause of the rare condition, holoprosencephaly. It was discovered that the Shh signalling pathway in the diencephalon was responsible for gene expression in the telencephalon. <br />
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In addition, through experimentation on chick embryos it was found that through Shh signalling the development of the forebrain regulates and controls facial morphogenesis, particularly of the upper and middle face. Therefore, interference with Shh signalling in the forebrain prevents this intrinsic communication, thus hindering Shh expression in facial ectoderm. This results in brain malformation accompanied by facial disfiguration as seen in patients suffering from HPE. Other malformations caused by blockage of Shh signalling in craniofacial development include, hypotelorism (decreased space between the orbits), growth restriction as well as cleft lip and palate as mentioned previously. <br />
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A commonality discovered among all forms of Shh signalling disruption was two facial defects, “the loss of mediolateral expansion of the face and absence of proximodistal outgrowth of the frontonasal prominence”<ref><pubmed>15979605</pubmed></ref> (Ralph et al., 2005). Through reference to studies performed on chick and mice embryos, it was found that Shh signalling is particularly vital in development of maxillary and frontonasal components of the cranium.<br />
<br />
This breakthrough study on the inhibition of Shh signalling in chick embryos has significantly filled the gap in our understanding of the Sonic Hedgehog signalling pathway. It is evident that this pathway is crucial in the development of the forebrain and in turn regulates and controls the development of the facial skeleton. This is further proven through the observation that in the event of Shh signalling inhibition there is a development of craniofacial malformations.<br />
<br />
=== Shh knockout mice ===<br />
<br />
Extensive research on Shh knockout mice allowed discovery of the roles of Shh in embryonic development and patterning of the limb buds and sclerotomes, and maintenance of the notochord. <ref><pubmed>8837770</pubmed></ref> These mice expressed defects in the cephalic neural tube with the fusion of telencephalic and optic vesicles. Through this research it is evident that Shh is partially responsible for the subdivision of the eye field through forebrain optic stalk development, along with formation of the ventral midline. It is these forebrain abnormalities established in the absence of Shh that results in congenital malformations of holoprosencephaly, development of a single nasal chamber and other facial defects in humans. <br />
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The absence of the vertebral column including, the intervertebral discs and vertebrae along with the medial regions of the ribs were observed within Shh knockout mice. This lack of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population (Chiang et al., 1996). In addition, though the role of Shh in patterning the anterior-posterior limb axis is evident through anterior limb bud cell death in the absence of Shh, it is also responsible for the development of proximal-distal limb segments, particularly in the patterning of structures at the level of or distal to the latent elbow and knee joints. <ref><pubmed>11476582</pubmed></ref> This was perceived after observing the incomplete formation of distal limb structures with abnormal anterior-posterior axis formation (Chiang et al., 2001). Thus, Shh knockout mice provide great insight into the functions of Shh in embryonic development and the abnormalities formed in the absence of this signalling protein. <br />
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== Clinical Significance ==<br />
<br />
===Gorlin Syndrome===<br />
[[File:1 week year old newborn girl with cleft lip and palate.png|thumb|An image of a 1 week year old newborn girl with cleft lip and palate]]<br />
Gorlin syndrome, also known as nevoid basal cell carcinoma syndrome, is a heritable disease resulting from heterozygousity in Hh receptor, Patched (PTC). The PTC gene encodes a protein which binds sonic hedgehog (Shh) and it is this binding which inhibits the Hh signalling pathway. However mutation of PTC leads to activation of the pathway <ref><pubmed>9620294</pubmed></ref>. The syndrome is characteristic of skin cancer basal cell carcinoma and cerebellum cancer medulloblastoma. 1-2% of medulloblastomas and 0.5% of basal cell carcinomas are attributable to the disease. Patients present with craniofacial and brain abnormalities such as cleft palate, strabismus, macrocephaly, abnormal development of the corpus callosum and frontal bossing, with an overall overgrown appearance. Skeletal defects such as of the shoulder, ribs and vertebrae are often seen, as well immobile thumbs and polydactyly, which is a deformity of the hand or feet in which they have one or more extra fingers or toes. Apart from physical anomalies, patients have an increased risk of tumours throughout the body including cardiac, ovarian fibromas, ovarian dermoid cysts, meningiomas, and fibrosarcomas. Additionally with time, patients eventually undergo intracranial calcification and dyskeratotic pitting of the hands and feet whereby skin cells prematurely convert to keratin <ref><pubmed>8681379</pubmed></ref>.<br />
<br />
===Holoprosencephaly===<br />
<br>[[File:Semilobar holoprosencephaly.jpg|thumb|240px|MRI of fore brain depicting semilobar holoprosencephaly]]<br />
Holoprosencephaly (HPE) is a congenital disease caused by incomplete division of the prosencephalon (embryonic forebrain) into separate lobes of the cerebral hemispheres. The Shh gene has been identified as a HPE-causing gene however recent evidence has also investigated into the PTC gene, which acts to repress Shh signalling. A gain in repressive action of PTC is seen, leading to decreased Shh signalling, and thus HPE <ref><pubmed>11941477</pubmed></ref>. Clinical expression is variable between patients and is dependent upon the 3 forms of increasing severity: lobar, semi-lobar and alobar HPE, where patients can present with right and left ventricles however with a continuous frontal cortex in lobar HPE, to carrying a single cerebral ventricle in alobar HPE. Along with forebrain abnormalities, facial anomalies are also seen including midline cleft lip and/or flat nose, ocular hypotelorism characteristic of a small distance between the eyes. In severe rare cases of cyclopia, a non-functioning nose may be observed in the form of proboscis and the patient may present with a single eye at the root of the nose <ref><pubmed>20583177</pubmed></ref>. Furthermore, patients with HPE often develop a large number of medical issues including epilepsy, mental retardation, thyroid and adrenal hypoplasia due to lack of hypothalamus or pituitary gland development, and diabetes insipidus.<br />
<br />
===Medulloblastoma===<br />
Medulloblastoma is a cancerous tumour of the cerebellum where the cells of origin are the granular cell precursors found in the neonatal cerebellum, explaining its high prevalence in children <ref><pubmed>19171780</pubmed></ref>. Commonly, medulloblastomas are found deep in the cerebellum along the midline, however with desmoplastic medulloblastomas, they are found more laterally and superficial. As seen previously with Gorlin syndrome and holoprosencephaly, PTC is also associated with the development of medulloblastoma, and misregulation of Hh-PTC signalling in cells of the external germinal layer, the layer found on the surface of the cerebellum, is thought to give rise to the tumour. In experimental studies, it has been discovered that PTC is highly transcribed in medulloblastomas and in approximately 30% of PTC heterozygous mice the tumour develops <ref><pubmed>9205058</pubmed></ref> <ref><pubmed>9262482</pubmed></ref>. In patients with medulloblastoma, often children, the most common symptoms seen are vomiting, ataxia, psychomotor regression, drowsiness and anorexia. With age, patients are seen to get more frequent headaches, and show psychological symptoms such as behavioural problems, poor performance in school, and anxiety. In patients exhibiting life-threatening symptoms due to increased intracranial hypertension, bradycardia, convulsions and coma are often seen <ref><pubmed>21537925</pubmed></ref>.<br />
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== Current research ==<br />
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==Glossary==<br />
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== References ==</div>
Z5018221
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===Reference===
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Gassling, V., Holterhus, P. M., Herbers, D., Kulle, A., Niederberger, U., Hedderich, J., Wiltfang, J., and Gerber, W. D. (2012). Stress-coping and co...</p>
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<div>==1 week year old newborn girl with cleft lip and palate==<br />
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===Reference===<br />
<pubmed>22911731</pubmed><br />
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Gassling, V., Holterhus, P. M., Herbers, D., Kulle, A., Niederberger, U., Hedderich, J., Wiltfang, J., and Gerber, W. D. (2012). Stress-coping and cortisol analysis in patients with non-syndromic cleft lip and palate: an explorative study. PloS one, 7(7), e41015.<br />
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===Copyright===<br />
© 2012 Gassling et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.<br />
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= Hedgehog signalling pathway =<br />
==Introduction==<br />
[[File:Hedgehog.jpg|thumb|300px|An image of a hedgehog, the animal of which the Hh proteins are named after.]]<br />
The Hedgehog (Hh) signalling pathway is an important part of the early embryo with regards to the patterning and development of the nervous system, limbs and the cranio-facial region in vertebrates and the polarization of the segments in the ''Drosophila'' embryo. It was first identified in 1980 by Christiane Nüsslein-Volhard and Eric Wieschaus, alongside a group of other genes regulating segment polarity in ''Drosophila'' embryonic development<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. The pathway itself consists of Hh proteins, where there are three identified homologs in vertebrates, being sonic hedgehog (SHH), Indian hedgehog (IHH), and desert hedgehog (DHH) <ref name="PMID7916661"><pubmed>7916661</pubmed></ref>. All homologs are expressed at varying levels within different tissues in the body, and also act as a form of redundancy to an extent between one another. <br />
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The signaling pathway is highly conserved between various species<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. and acts via a G protein coupled receptor like receptor, which uninhibited via the action of the Hh proteins. The pathway overall acts via a balance of dephosphorylation<ref name="PMID10966113"><pubmed>10966113</pubmed></ref> and degradation of proteins<ref name="PMID15102702"><pubmed>15102702</pubmed></ref> in order to regulate transcription factor activity to express various genes to carry out its action. The Hh pathway is also highly implicated when it comes to abnormalities in development, as it is implicated in diseases such as holoprosencephaly and cleft lip and palate. Overall Hh signaling pathways play a large role in embryological development, which will be discussed in detail on this page.<br />
<br />
== History ==<br />
{| class="pretty table"<br />
| '''1980'''<br />
|Christiane Nüsslein-Volhard and Eric Wieschaus first identified a group of genes including those related to the Hedgehog signalling pathway and linked them to the segmentation and planning of the embryo in ''Drosophila melanogaster'' by introducing mutagenic substances to the developing embryo<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
| Multiple researchers including Andrew P. McMahon and Clifford Tabin discovered three equivalent homologs in vertebrates of the ''Drosophila melanogaster'' hedgehog gene, known as sonic hedgehog (SHH), desert hedgehog (DHH) and indian hedgehog (IHH), by looking at DNA sequences similar to that of the gene in the fruit fly<ref><pubmed>7916661</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
| Clifford Tabin and his lab identified the role of SHH in localising the limb bud, where they identified protein to be expressed within a region of the limb bud known as the zone of polarising activity (ZPA), showing that SHH is sufficient to induce the production of a ZPA, and thus limb bud formation in chick embryos<ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
| A shared Nobel prize in physiology or medicine was awarded to Christiane Nüsslein-Volhard and Eric Wieschaus for their researching regarding the identification of the developmental genes relating to the formation and patterning of the early embryo via genes.<br />
|-<br />
|'''2003'''<br />
| Studies on SHH function found that it can act as a chemoattractant in the developing embryo spinal cord, to help guide commissural axons to the midline of the floor plate<ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
|}<br />
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== Origin of name ==<br />
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[[File:Bands of denticles in normal and Hh mutant Drosophila embryo.jpeg|thumb|250px|Differences in patterning of the denticle bands in normal and mutated hedgehog gene variant ''Drosophilia'' embryo]]<br />
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The name hedgehog came about when Christiane Nüsslein-Volhard and Eric Wieschaus first identified the group of genes controlling polarization of the segments in the ''Drosophila'' early embryo. They noticed that when they mutated the Hh gene, making it non-functional, that the bands of denticles formed during the early ''Drosophila'' embryo formation became more diffuse as opposed to being distinct normally. The denticles would all clump together forming a single patch on the surface of the embryo, as opposed to normally outlining the distinct segments of the embryo as bands<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. This gave the embryo spiny and prickly look similar to that of the back of a hedgehog.<br />
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From there on in the gene was called the hedgehog gene where homologs in vertebrates discovered along the line kept to this naming structure giving various species of hedgehog names to the genes such as Indian hedgehog, and desert hedgehog, with the exception being sonic hedgehog, which is named after a fictional character in the video game “Sonic the Hedgehog”.<br />
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== Function ==<br />
===Overview===<br />
{| class="pretty table"<br />
|'''Hedgehog protein homolog'''<br />
|'''Function'''<br />
|-<br />
| Sonic hedgehog ||<br />
*Expressed in zone of polarizing activity of the limb bud where it plays a role in helping to pattern the anterior and posterior aspect of the limbs <ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
*Based on time and concentration of SHH due to diffusion from the point of secretion in the limb bud, SHH also plays a role in determining digit identity <ref name="PMID15315763"><pubmed>15315763</pubmed></ref>.<br />
*Acts as a chemoattractant to guide commissural axons in the floor plate of the neural tube towards the midline <ref name="PMID2679031"><pubmed>2679031</pubmed></ref>.<br />
*Patterns the developing cusps of the teeth and their relative positions in the jaw, and is also essential for the growth of the teeth <ref name="PMID11044393"><pubmed>11044393</pubmed></ref>.<br />
*SHH released from the notochord acts to induce formation of the floor plate, motor neurons, and dopaminergic neurons, as well as signalling the induction of the ventral cell types in the neural tube <ref name="PMID8790332"><pubmed>8790332</pubmed></ref>.<br />
|-<br />
| Desert hedgehog ||<br />
*Plays a possible role in regulating spermatogenesis as due to the highly localised expression in the testes by pre-Sertoli cells, and the fact that mice with no DHH present are infertile, with no mature spermatozoa <ref name="PMID8805249"><pubmed>8805249</pubmed></ref>. <br />
*DHH derived from Schwann cells signal development of peripheral nerves, by inducing the production of a connective tissue sheath around them <ref name="PMID10482238"><pubmed>10482238</pubmed></ref>.<br />
|-<br />
| Indian hedgehog ||<br />
*Aid in the signalling of proliferating chondrocytes to undergo hypertrophic differentiation during endochondral ossification<ref name="PMID8662546"><pubmed> 8662546</pubmed></ref>.<br />
*Plays a key role in yolk sac angiogenesis, as seen in studies where an absence of IHH leads to death of the embryo due to poor yolk sac vasculature <ref name="PMID11807029"><pubmed>11807029</pubmed></ref>.<br />
|}<br />
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=== Neural development ===<br />
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=== Organogenesis ===<br />
The Hedgehog Signalling pathway is a pathway sending information to embryonic cells which plays an especially important role in the regulation of organogenesis. These processes include the organization of the brain (craniofacial) and the growth of appendages with further studies implicating the Hedgehog Signalling pathway in the development of the small intestine, lungs and the pancreas.<br />
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== Mechanism ==<br />
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=== Processing of precursor ===<br />
<br>[[File:Processing of Hh precurosr.jpg|thumb|250px|Summary of the steps in the processing of the Hh protein precursor into a functional signalling molecule]]<br />
Hedgehog (Hh) proteins are produced as precursors, which must be processed by the cells producing it before being able to perform its signalling function. The process by which the Hh protein is processed begins with its signal sequence at its N terminus directing the translocation of the precursor into the endoplasmic reticulum, where it is removed via signal peptidase<ref><pubmed>1394430</pubmed></ref>. This process allows the C terminus of the Hh protein to catalyze the cleavage and addition of cholesterol on itself to form a C terminal processing domain and an N terminal processing domain associated with a cholesterol group on its C terminus<ref><pubmed>21357747</pubmed></ref>. The portion associated with the cholesterol will go on to form the signalling molecule, while the C terminal processing domain has no known signalling function<ref><pubmed>8824192</pubmed></ref>. <br />
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At this point the Hh protein associated with the cholesterol is able to perform its signalling action, but further modification is still required to ensure efficient signalling. This occurs when the cholesterol group attached to the Hh protein associates with the plasma membrane of the cell, which allows for the addition of a palmitic acid moiety to the N terminal of the protein by an acyl-transferase known as skinny hedgehog<ref><pubmed>11486055</pubmed></ref>. Studies have shown that such an addition allows for an increase in potency in signalling of Hh proteins of 30-fold over its form without palmitic acid added<ref><pubmed>9593755</pubmed></ref>. From this point the Hh protein is now fully active and can either remain associated to the plasma membrane of the cell for autocrine action or be secreted for paracrine action.<br />
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=== Mechanism of signalling ===<br />
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==== ''Drosophila melanogaster'' ====<br />
<br>[[File:Hh Signalling Pathway.jpg|thumb|600px|Steps regarding the processing of the hh protein precursor into the fully functional signalling molecule.]]<br />
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The Hh signaling pathway has been well studied in ''Drosophila melanogaster'', and has been shown the be conserved to an extent across it and mammals making the species a suitable model for Hh signalling in humans<ref name="PMID8595881"><pubmed>8595881</pubmed></ref>. In ''Drosophila melanogaster'', the Hh pathway begins when the Hh proteins bind to the extracellular domain of the transmembrane protein known as Patched (PTC) to inactivate it. This inactivation occurs by Hh trapping PTC in an inactive conformational state<ref><pubmed>27647915</pubmed></ref>. After binding of Hh occurs to PTC and it is inactivated, the receptor and Hh protein is thought to be endocytosed by the cell where they undergo lysosomal degradation in order to limit Hh concentration, thus limiting its spread to other cells and PTC activity<ref name="PMID15102702"><pubmed>15102702</pubmed></ref>. In the absence of Hh, PTC acts to suppress the expression of the Smoothened (SMO), a G-protein coupled receptor like receptor, and thus its signaling. How PTC achieves this inhibition of SMO is currently unclear. Studies have suggested that due to the highly phosphorylated nature of SMO when active, that PTC acts to dephosphorylate SMO in order to repress its signaling. It is thus that binding of Hh to PTC reduces PTCs ability to promote dephosphorylation of SMO, leading to its increased activity and expression on the cell surface <ref name="PMID10966113"><pubmed>10966113</pubmed></ref>. It is thought that the phosphorylation required to activate SMO are dependent on protein kinase A (PKA) and casein kinase I (CKI) <ref><pubmed>15616566 </pubmed></ref>.<br />
<br />
This overall increased phosphorylation of SMO due to a repression of PTC activity by Hh leads to an accumulation of SMO on the cell surface, which collectively allows for SMO to exert its activity. Most importantly phosphorylation also disrupts intramolecular electrostatic interactions between SMO molecules which switches the molecule into its active conformational state <ref><pubmed>17960137 </pubmed></ref>. Generally, SMO has been shown to have very little signal transducing ability, and thus this accumulation allows it to jointly transduce as substantial signal. This occurs by the C terminus of SMO on the intracellular domain interacting with the kinesin like protein Costal-2 (Cos2), which is thought to bind to microtubules in order to acts as a scaffolding protein <ref><pubmed>18691888 </pubmed></ref>. Then the kinase known as Fused (Fu) binds to Cos2, which phosphorylates Suppressor of Fused (SUFU) to inhibit it. Without this inhibition SUFU goes onto prevent the translocation of the transcriptional factor Cubitus interruptus (Ci) into the nucleus by leading to its phosphorylation, and subsequently its partial cleavage via the proteosome. The partial cleavage of Ci leaves a lower molecular weight protein known as Ci repressor (CiR) or Ci75, which translocates into the nucleus and acts to repress the target genes of the Hh signalling pathway via Ci<ref><pubmed>9215627</pubmed></ref>. Thus overall inhibition of SUFU increases the amount of Ci entering into the nucleus of the cell, and activating transcription of target genes of the Hh pathway<ref><pubmed>10952898 </pubmed></ref>.<br />
<br />
At this point Ci is able to activate the transcription of various genes, which include importantly the ''ptc'' gene, which encodes the PTC receptor. It is thus as a result of this, that PTC expression will be increased in response to Hh pathway induction, which negatively feeds back to reduce Ci signaling induction, in order to maintain homeostasis and regulate the intensity and duration of the signaling from Hh<ref><pubmed>9053330</pubmed></ref>. Furthermore the ''wg'' gene, encoding the wingless protein is also activated by Ci, which leads to activation of the Wnt pathway via the Frizzled receptor in adjacent cells expressing the gene ''engrailed'' <ref><pubmed>9502727</pubmed></ref> <ref><pubmed>10457026</pubmed></ref>. This overall stabalizes the boundaries between the segments of the developing ''Drosophila melanogaster'' signalled by the gene ''engrailed''<ref><pubmed>3282172</pubmed></ref>.<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=w1xXD9kss2w</html5media><br />
<br><br><br />
An overview of the hedgehog signalling pathway in ''Drosophila''<ref>YouTube. (2016). The Hedgehog signalling pathway in Drosophila online Available at: https://www.youtube.com/watch?v=w1xXD9kss2w</ref>.<br />
<br />
==== Mammals ====<br />
<br />
Although the Hh signaling pathway has been conserved across species to an extent <ref name="PMID8595881"><pubmed>8595881</pubmed></ref>, key differences exist when observing the pathway within mammalian tissue in contrast to that which has been studied in ''Drosophila melanogaster''. In mammalian cells and all other vertebrates, Hh signalling is dependent on an organelle known as the primary cilia, which are projections outwards from the cells surface. The importance of such an organelle in the signalling pathway comes as a result of PTC1, one of the two PTC receptor homologs in mammals, that binds to the Hh homolog Sonic Hh (Shh), exists within the cilia<ref><pubmed>17641202</pubmed></ref>. The mechanism of action of SMO inhibition and activation is poorly understood currently, but evidence has suggested that PTC1 acts to inhibit SMO when unbound to Shh by acting as a pump to remove oxysterols from the cilia into the extracellular space. <ref><pubmed>PMC1462959</pubmed></ref>. These oxysterols are normally thought to bind and accumulate around the SMO receptors, which in turn prevents internalization and deactivation of SMO, leading to it accumulating on the apical primary cilia<ref><pubmed>16136078</pubmed></ref>. Other studies have also suggested that Shh has a role in increasing phosphorylation of SMO, which is required for it to accumulate as well on the cilia<ref><pubmed>21695114</pubmed></ref>. Overall the net action of Shh initially is believed to cause accumulation of SMO at the cilia by inhibiting PTCH1 and phosphorylation of SMO.<br />
<br />
How SMO acts next is relatively unknown but, it has been shown to promote the disassociation between SUFU and Gli3 transcription factor, which allows Gli to be transported to the nucleus to activate effector genes of the pathway. Gli is normally bound in the cytoplasm to SUFU, where SUFU promotes the partial degradation of Gli into its repressor form, similar to that in the fruit fly model<ref><pubmed>20360384</pubmed></ref>. Alongside this, Kif7, a Cos2 homolog, has been shown to migrate to the apex of the cilium in response to SMO accumulation at the cilium, where it has been postulated to also promote disassociation of SUFU and Gli<ref><pubmed>19592253</pubmed></ref>. On the other hand, Kif7 is also thought to play an inhibitory role for the signaling pathway as when it is localized at the base of the cilia in the absence of Hh signaling and traffics Gli factors away from the cilia<ref><pubmed>19666503</pubmed></ref>. This all leads to an accumulation of active Gli transcription factors which migrate to the nucleus in order either inhibit or activate gene transcription in response to Hh signaling.<br />
<br />
== Animal models ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br />
Hedgehog (Hh) protein signal was initially discovered through experimentation on the fruit fly, "Drosophila melanogaster". It is through this model that we are able to discover not only the functional components of this pathway but also understand its role in embryonic development. Through application of this information on the human biological system we are able to find the cause and thus potential treatments of defects and diseases caused by interruption or mutation of the Hedgehog signalling pathway. <br />
<br />
Upon further research on Drosophila it was found that Hh may play a role in germ cell proliferation and in particular, may control the proliferation and activity of somatic cells found within the germarium, which is the most anterior structure within the Drosophila ovary. <ref>Ovaries (Drosophila) definition. (2016). Groups.molbiosci.northwestern.edu. Retrieved 10 September 2016, from http://groups.molbiosci.northwestern.edu/holmgren/Glossary/Definitions/Def-D/Drosophila_Ovaries.html</ref> Thus, the Hh signalling pathway is vital in egg chamber formation and its consequent envelopment, budding and polarisation. It has also been observed that somatic cell proliferation is dependent on this pathway and thus, the number of pre-follicle cells is subject to the effect of the Hh signalling pathway. <ref><pubmed>8620839</pubmed></ref> Further studies have also indicated the role played by this pathway in activating the Epidermal growth factor receptor (EGFR) signalling pathway as seen in the induction of EGFR by Hh in Drosophila head development. <ref><pubmed>10331974</pubmed></ref> In addition, research on Drosophila has indicated the direct effect of Hh signalling on tracheal branch patterning. <ref><pubmed>11290298</pubmed></ref><br />
<br />
Despite ongoing research on "Drosophila melanogaster" to uncover the workings of the Hedgehog signalling pathway, further research is needed to confirm and further current findings. In addition, it is evident that it is through the study of these fruit flies that we are able to gain a basis of understanding of the causes of certain human diseases and thus propel research into treatments for sufferers. <br />
<br />
===Blockage of Shh Signalling in Forebrain Neuroectoderm of Chick Embryos===<br />
<br />
The Hedgehog signalling pathway plays a significant role in embryonic development, particularly of the forebrain. Due to its role in development of craniofacial features by contributing to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm, a disruption in this pathway can result in a variety of birth deformities including holoprosencephaly (HPE), where the prosencephalon (forebrain) fails to divide into 2 separate hemispheres, telencephalon and diencephalon <ref>Holoprosencephaly - NORD (National Organization for Rare Disorders). (2016). NORD (National Organization for Rare Disorders). Retrieved 10 September 2016, from http://rarediseases.org/rare-diseases/holoprosencephaly/</ref>, as well as cleft lip and palate. The function of Sonic Hedgehog (Shh) and its signalling pathway on the formation of forebrain neuroectoderm was studied in chick embryos.<br />
<br />
It was found that the disruption of Shh signalling in the neural tube of chick embryos resulted in the lack of division of the forebrain into the diencephalon and telencephalon. This is in fact, as stated earlier, the fundamental cause of the rare condition, holoprosencephaly. It was discovered that the Shh signalling pathway in the diencephalon was responsible for gene expression in the telencephalon. <br />
<br />
In addition, through experimentation on chick embryos it was found that through Shh signalling the development of the forebrain regulates and controls facial morphogenesis, particularly of the upper and middle face. Therefore, interference with Shh signalling in the forebrain prevents this intrinsic communication, thus hindering Shh expression in facial ectoderm. This results in brain malformation accompanied by facial disfiguration as seen in patients suffering from HPE. Other malformations caused by blockage of Shh signalling in craniofacial development include, hypotelorism (decreased space between the orbits), growth restriction as well as cleft lip and palate as mentioned previously. <br />
<br />
A commonality discovered among all forms of Shh signalling disruption was two facial defects, “the loss of mediolateral expansion of the face and absence of proximodistal outgrowth of the frontonasal prominence”<ref><pubmed>15979605</pubmed></ref> (Ralph et al., 2005). Through reference to studies performed on chick and mice embryos, it was found that Shh signalling is particularly vital in development of maxillary and frontonasal components of the cranium.<br />
<br />
This breakthrough study on the inhibition of Shh signalling in chick embryos has significantly filled the gap in our understanding of the Sonic Hedgehog signalling pathway. It is evident that this pathway is crucial in the development of the forebrain and in turn regulates and controls the development of the facial skeleton. This is further proven through the observation that in the event of Shh signalling inhibition there is a development of craniofacial malformations.<br />
<br />
=== Shh knockout mice ===<br />
<br />
Extensive research on Shh knockout mice allowed discovery of the roles of Shh in embryonic development and patterning of the limb buds and sclerotomes, and maintenance of the notochord. <ref><pubmed>8837770</pubmed></ref> These mice expressed defects in the cephalic neural tube with the fusion of telencephalic and optic vesicles. Through this research it is evident that Shh is partially responsible for the subdivision of the eye field through forebrain optic stalk development, along with formation of the ventral midline. It is these forebrain abnormalities established in the absence of Shh that results in congenital malformations of holoprosencephaly, development of a single nasal chamber and other facial defects in humans. <br />
<br />
The absence of the vertebral column including, the intervertebral discs and vertebrae along with the medial regions of the ribs were observed within Shh knockout mice. This lack of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population (Chiang et al., 1996). In addition, though the role of Shh in patterning the anterior-posterior limb axis is evident through anterior limb bud cell death in the absence of Shh, it is also responsible for the development of proximal-distal limb segments, particularly in the patterning of structures at the level of or distal to the latent elbow and knee joints. <ref><pubmed>11476582</pubmed></ref> This was perceived after observing the incomplete formation of distal limb structures with abnormal anterior-posterior axis formation (Chiang et al., 2001). Thus, Shh knockout mice provide great insight into the functions of Shh in embryonic development and the abnormalities formed in the absence of this signalling protein. <br />
<br />
== Clinical Significance ==<br />
<br />
===Gorlin Syndrome===<br />
Gorlin syndrome, also known as nevoid basal cell carcinoma syndrome, is a heritable disease resulting from heterozygousity in Hh receptor, Patched (PTC). The PTC gene encodes a protein which binds sonic hedgehog (Shh) and it is this binding which inhibits the Hh signalling pathway. However mutation of PTC leads to activation of the pathway <ref><pubmed>9620294</pubmed></ref>. The syndrome is characteristic of skin cancer basal cell carcinoma and cerebellum cancer medulloblastoma. 1-2% of medulloblastomas and 0.5% of basal cell carcinomas are attributable to the disease. Patients present with craniofacial and brain abnormalities such as cleft palate, strabismus, macrocephaly, abnormal development of the corpus callosum and frontal bossing, with an overall overgrown appearance. Skeletal defects such as of the shoulder, ribs and vertebrae are often seen, as well immobile thumbs and polydactyly, which is a deformity of the hand or feet in which they have one or more extra fingers or toes. Apart from physical anomalies, patients have an increased risk of tumours throughout the body including cardiac, ovarian fibromas, ovarian dermoid cysts, meningiomas, and fibrosarcomas. Additionally with time, patients eventually undergo intracranial calcification and dyskeratotic pitting of the hands and feet whereby skin cells prematurely convert to keratin <ref><pubmed>8681379</pubmed></ref>.<br />
<br />
===Holoprosencephaly===<br />
<br>[[File:Semilobar holoprosencephaly.jpg|thumb|240px|MRI of fore brain depicting semilobar holoprosencephaly]]<br />
Holoprosencephaly (HPE) is a congenital disease caused by incomplete division of the prosencephalon (embryonic forebrain) into separate lobes of the cerebral hemispheres. The Shh gene has been identified as a HPE-causing gene however recent evidence has also investigated into the PTC gene, which acts to repress Shh signalling. A gain in repressive action of PTC is seen, leading to decreased Shh signalling, and thus HPE <ref><pubmed>11941477</pubmed></ref>. Clinical expression is variable between patients and is dependent upon the 3 forms of increasing severity: lobar, semi-lobar and alobar HPE, where patients can present with right and left ventricles however with a continuous frontal cortex in lobar HPE, to carrying a single cerebral ventricle in alobar HPE. Along with forebrain abnormalities, facial anomalies are also seen including midline cleft lip and/or flat nose, ocular hypotelorism characteristic of a small distance between the eyes. In severe rare cases of cyclopia, a non-functioning nose may be observed in the form of proboscis and the patient may present with a single eye at the root of the nose <ref><pubmed>20583177</pubmed></ref>. Furthermore, patients with HPE often develop a large number of medical issues including epilepsy, mental retardation, thyroid and adrenal hypoplasia due to lack of hypothalamus or pituitary gland development, and diabetes insipidus.<br />
<br />
===Medulloblastoma===<br />
Medulloblastoma is a cancerous tumour of the cerebellum where the cells of origin are the granular cell precursors found in the neonatal cerebellum, explaining its high prevalence in children <ref><pubmed>19171780</pubmed></ref>. Commonly, medulloblastomas are found deep in the cerebellum along the midline, however with desmoplastic medulloblastomas, they are found more laterally and superficial. As seen previously with Gorlin syndrome and holoprosencephaly, PTC is also associated with the development of medulloblastoma, and misregulation of Hh-PTC signalling in cells of the external germinal layer, the layer found on the surface of the cerebellum, is thought to give rise to the tumour. In experimental studies, it has been discovered that PTC is highly transcribed in medulloblastomas and in approximately 30% of PTC heterozygous mice the tumour develops <ref><pubmed>9205058</pubmed></ref> <ref><pubmed>9262482</pubmed></ref>. In patients with medulloblastoma, often children, the most common symptoms seen are vomiting, ataxia, psychomotor regression, drowsiness and anorexia. With age, patients are seen to get more frequent headaches, and show psychological symptoms such as behavioural problems, poor performance in school, and anxiety. In patients exhibiting life-threatening symptoms due to increased intracranial hypertension, bradycardia, convulsions and coma are often seen <ref><pubmed>21537925</pubmed></ref>.<br />
<br />
<br />
== Current research ==<br />
<br />
==Quiz==<br />
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==Glossary==<br />
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| Insert definition here<br />
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===Additional Glossary Links===<br />
[[A|A]] | [[B|B]] | [[C|C]] | [[D|D]] | [[E|E]] | [[F|F]] | [[G|G]] | [[H|H]] | [[I|I]] | [[J|J]] | [[K|K]] | [[L|L]] | [[M|M]] | [[N|N]] | [[O|O]] | [[P|P]] | [[Q|Q]] | [[R|R]] | [[S|S]] | [[T|T]] | [[U|U]] | [[V|V]] | [[W|W]] | [[X|X]] | [[Y|Y]] | [[Z|Z]] | [[Numbers|#]]<br />
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== References ==</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=2016_Group_Project_4&diff=252656
2016 Group Project 4
2016-10-21T11:25:46Z
<p>Z5018221: </p>
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<div>{{ANAT2341Project2016header}}<br />
{{Group Assessment Criteria table}}<br />
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<br />
= Hedgehog signalling pathway =<br />
==Introduction==<br />
== History ==<br />
{| class="pretty table"<br />
| '''1980'''<br />
|Christiane Nüsslein-Volhard and Eric Wieschaus first identified a group of genes including those related to the Hedgehog signalling pathway and linked them to the segmentation and planning of the embryo in ''Drosophila melanogaster'' by introducing mutagenic substances to the developing embryo<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
| Multiple researchers including Andrew P. McMahon and Clifford Tabin discovered three equivalent homologs in vertebrates of the ''Drosophila melanogaster'' hedgehog gene, known as sonic hedgehog (SHH), desert hedgehog (DHH) and indian hedgehog (IHH), by looking at DNA sequences similar to that of the gene in the fruit fly<ref><pubmed>7916661</pubmed></ref><ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
|-<br />
|'''1993'''<br />
| Clifford Tabin and his lab identified the role of SHH in localising the limb bud, where they identified protein to be expressed within a region of the limb bud known as the zone of polarising activity (ZPA), showing that SHH is sufficient to induce the production of a ZPA, and thus limb bud formation in chick embryos<ref name="PMID8269518"><pubmed>8269518</pubmed></ref>.<br />
|-<br />
|'''1995'''<br />
| A shared Nobel prize in physiology or medicine was awarded to Christiane Nüsslein-Volhard and Eric Wieschaus for their researching regarding the identification of the developmental genes relating to the formation and patterning of the early embryo via genes.<br />
|-<br />
|'''2003'''<br />
| Studies on SHH function found that it can act as a chemoattractant in the developing embryo spinal cord, to help guide commissural axons to the midline of the floor plate<ref><pubmed> 2679031</pubmed></ref>.<br />
|}<br />
<br />
== Origin of name ==<br />
<br />
[[File:Bands of denticles in normal and Hh mutant Drosophila embryo.jpeg|thumb|250px|Differences in patterning of the dentricle bands in normal and mutated hedgehog gene variant ''Drosophilia'' embryo]]<br />
<br />
The name hedgehog came about when Christiane Nüsslein-Volhard and Eric Wieschaus first identified the group of genes controlling polarization of the segments in the ''Drosophila'' early embryo. They noticed that when they mutated the Hh gene, making it non-functional, that the bands of denticles formed during the early ''Drosophila'' embryo formation became more diffuse as opposed to being distinct normally. The denticles would all clump together forming a single patch on the surface of the embryo, as opposed to normally outlining the distinct segments of the embryo as bands<ref name="PMID6776413"><pubmed>6776413</pubmed></ref>. This gave the embryo spiny and prickly look similar to that of the back of a hedgehog.<br />
<br />
From there on in the gene was called the hedgehog gene where homologs in vertebrates discovered along the line kept to this naming structure giving various species of hedgehog names to the genes such as Indian hedgehog, and desert hedgehog, with the exception being sonic hedgehog, which is named after a fictional character in the video game “Sonic the Hedgehog”.<br />
<br />
== Function ==<br />
<br />
=== Neural development ===<br />
<br />
=== Organogenesis ===<br />
The Hedgehog Signalling pathway is a pathway sending information to embryonic cells which plays an especially important role in the regulation of organogenesis. These processes include the organization of the brain (craniofacial) and the growth of appendages with further studies implicating the Hedgehog Signalling pathway in the development of the small intestine, lungs and the pancreas.<br />
<br />
== Mechanism ==<br />
<br />
=== Processing of precursor ===<br />
<br>[[File:Hh Signalling Pathway.jpg|thumb|600px|Overview of the Hedgehog signalling pathway]]<br />
<br />
Hedgehog (Hh) proteins are produced as precursors, which must be processed by the cells producing it before being able to perform its signalling function. The process by which the Hh protein is processed begins with its signal sequence at its N terminus directing the translocation of the precursor into the endoplasmic reticulum, where it is removed via signal peptidase<ref><pubmed>1394430</pubmed></ref>. This process allows the C terminus of the Hh protein to catalyze the cleavage and addition of cholesterol on itself to form a C terminal processing domain and an N terminal processing domain associated with a cholesterol group on its C terminus<ref><pubmed>21357747</pubmed></ref>. The portion associated with the cholesterol will go on to form the signalling molecule, while the C terminal processing domain has no known signalling function<ref><pubmed>8824192</pubmed></ref>. <br />
<br />
At this point the Hh protein associated with the cholesterol is able to perform its signalling action, but further modification is still required to ensure efficient signalling. This occurs when the cholesterol group attached to the Hh protein associates with the plasma membrane of the cell, which allows for the addition of a palmitic acid moiety to the N terminal of the protein by an acyl-transferase known as skinny hedgehog<ref><pubmed>11486055</pubmed></ref>. Studies have shown that such an addition allows for an increase in potency in signalling of Hh proteins of 30-fold over its form without palmitic acid added<ref><pubmed>9593755</pubmed></ref>. From this point the Hh protein is now fully active and can either remain associated to the plasma membrane of the cell for autocrine action or be secreted for paracrine action.<br />
<br />
=== Mechanism of signalling ===<br />
<br />
==== '''''Drosophila melanogaster''''' ====<br />
<br />
The Hh signaling pathway has been well studied in ''Drosophila melanogaster'', and has been shown the be conserved to an extent across it and mammals making the species a suitable model for Hh signalling in humans<ref><pubmed>8595881</pubmed></ref>. In ''Drosophila melanogaster'', the Hh pathway begins when the Hh proteins bind to the extracellular domain of the transmembrane protein known as Patched (PTC) to inactivate it. This inactivation occurs by Hh trapping PTC in an inactive conformational state<ref><pubmed>27647915</pubmed></ref>. After binding of Hh occurs to PTC and it is inactivated, the receptor and Hh protein is thought to be endocytosed by the cell where they undergo lysosomal degradation in order to limit Hh concentration, thus limiting its spread to other cells and PTC activity<ref><pubmed>15102702</pubmed></ref>. In the absence of Hh, PTC acts to suppress the expression of the Smoothened (SMO), a G-protein coupled receptor like receptor, and thus its signaling. How PTC achieves this inhibition of SMO is currently unclear. Studies have suggested that due to the highly phosphorylated nature of SMO when active, that PTC acts to dephosphorylate SMO in order to repress its signaling. It is thus that binding of Hh to PTC reduces PTCs ability to promote dephosphorylation of SMO, leading to its increased activity and expression on the cell surface <ref><pubmed>10966113</pubmed></ref>. It is thought that the phosphorylation required to activate SMO are dependent on protein kinase A (PKA) and casein kinase I (CKI) <ref><pubmed>15616566 </pubmed></ref>.<br />
<br />
This overall increased phosphorylation of SMO due to a repression of PTC activity by Hh leads to an accumulation of SMO on the cell surface, which collectively allows for SMO to exert its activity. Most importantly phosphorylation also disrupts intramolecular electrostatic interactions between SMO molecules which switches the molecule into its active conformational state <ref><pubmed>17960137 </pubmed></ref>. Generally, SMO has been shown to have very little signal transducing ability, and thus this accumulation allows it to jointly transduce as substantial signal. This occurs by the C terminus of SMO on the intracellular domain interacting with the kinesin like protein Costal-2 (Cos2), which is thought to bind to microtubules in order to acts as a scaffolding protein <ref><pubmed>18691888 </pubmed></ref>. Then the kinase known as Fused (Fu) binds to Cos2, which phosphorylates Suppressor of Fused (SUFU) to inhibit it. Without this inhibition SUFU goes onto prevent the translocation of the transcriptional factor Cubitus interruptus (Ci) into the nucleus by leading to its phosphorylation, and subsequently its partial cleavage via the proteosome. The partial cleavage of Ci leaves a lower molecular weight protein known as Ci repressor (CiR) or Ci75, which translocates into the nucleus and acts to repress the target genes of the Hh signalling pathway via Ci<ref><pubmed>9215627</pubmed></ref>. Thus overall inhibition of SUFU increases the amount of Ci entering into the nucleus of the cell, and activating transcription of target genes of the Hh pathway<ref><pubmed>10952898 </pubmed></ref>.<br />
<br />
At this point Ci is able to activate the transcription of various genes, which include importantly the ''ptc'' gene, which encodes the PTC receptor. It is thus as a result of this, that PTC expression will be increased in response to Hh pathway induction, which negatively feeds back to reduce Ci signaling induction, in order to maintain homeostasis and regulate the intensity and duration of the signaling from Hh<ref><pubmed>9053330</pubmed></ref>. Furthermore the ''wg'' gene, encoding the wingless protein is also activated by Ci, which leads to activation of the Wnt pathway via the Frizzled receptor in adjacent cells expressing the gene ''engrailed'' <ref><pubmed>9502727</pubmed></ref> <ref><pubmed>10457026</pubmed></ref>. This overall stabalizes the boundaries between the segments of the developing ''Drosophila melanogaster'' signalled by the gene ''engrailed''<ref><pubmed>3282172</pubmed></ref>.<br />
<br><br><br />
<html5media width="560" height="315">https://www.youtube.com/watch?v=w1xXD9kss2w</html5media><br />
<br><br><br />
An overview of the hedgehog signalling pathway in ''Drosophila''<ref>YouTube. (2016). The Hedgehog signalling pathway in Drosophila online Available at: https://www.youtube.com/watch?v=w1xXD9kss2w</ref>.<br />
<br />
===='''Mammals'''====<br />
<br />
Although the Hh signaling pathway has been conserved across species to an extent <ref><pubmed>8595881</pubmed></ref>, key differences exist when observing the pathway within mammalian tissue in contrast to that which has been studied in Drosophila melanogaster. In mammalian cells and all other vertebrates, Hh signalling is dependent on an organelle known as the primary cilia, which are projections outwards from the cells surface. The importance of such an organelle in the signalling pathway comes as a result of PTC1, one of the two PTC receptor homologs in mammals, that binds to the Hh homolog Sonic Hh (Shh), exists within the cilia<ref><pubmed>17641202</pubmed></ref>. The mechanism of action of SMO inhibition and activation is poorly understood currently, but evidence has suggested that PTC1 acts to inhibit SMO when unbound to Shh by acting as a pump to remove oxysterols from the cilia into the extracellular space. <ref><pubmed>PMC1462959</pubmed></ref>. These oxysterols are normally thought to bind and accumulate around the SMO receptors, which in turn prevents internalization and deactivation of SMO, leading to it accumulating on the apical primary cilia<ref><pubmed>16136078</pubmed></ref>. Other studies have also suggested that Shh has a role in increasing phosphorylation of SMO, which is required for it to accumulate as well on the cilia<ref><pubmed>21695114</pubmed></ref>. Overall the net action of Shh initially is believed to cause accumulation of SMO at the cilia by inhibiting PTCH1 and phosphorylation of SMO.<br />
<br />
How SMO acts next is relatively unknown but, it has been shown to promote the disassociation between SUFU and Gli3 transcription factor, which allows Gli to be transported to the nucleus to activate effector genes of the pathway. Gli is normally bound in the cytoplasm to SUFU, where SUFU promotes the partial degradation of Gli into its repressor form, similar to that in the fruit fly model<ref><pubmed>20360384</pubmed></ref>. Alongside this, Kif7, a Cos2 homolog, has been shown to migrate to the apex of the cilium in response to SMO accumulation at the cilium, where it has been postulated to also promote disassociation of SUFU and Gli<ref><pubmed>19592253</pubmed></ref>. On the other hand, Kif7 is also thought to play an inhibitory role for the signaling pathway as when it is localized at the base of the cilia in the absence of Hh signaling and traffics Gli factors away from the cilia<ref><pubmed>19666503</pubmed></ref>. This all leads to an accumulation of active Gli transcription factors which migrate to the nucleus in order either inhibit or activate gene transcription in response to Hh signaling.<br />
<br />
== Animal models ==<br />
<br />
=== ''Drosophila melanogaster'' ===<br />
<br />
Hedgehog (Hh) protein signal was initially discovered through experimentation on the fruit fly, "Drosophila melanogaster". It is through this model that we are able to discover not only the functional components of this pathway but also understand its role in embryonic development. Through application of this information on the human biological system we are able to find the cause and thus potential treatments of defects and diseases caused by interruption or mutation of the Hedgehog signalling pathway. <br />
<br />
Upon further research on Drosophila it was found that Hh may play a role in germ cell proliferation and in particular, may control the proliferation and activity of somatic cells found within the germarium, which is the most anterior structure within the Drosophila ovary. <ref>Ovaries (Drosophila) definition. (2016). Groups.molbiosci.northwestern.edu. Retrieved 10 September 2016, from http://groups.molbiosci.northwestern.edu/holmgren/Glossary/Definitions/Def-D/Drosophila_Ovaries.html</ref> Thus, the Hh signalling pathway is vital in egg chamber formation and its consequent envelopment, budding and polarisation. It has also been observed that somatic cell proliferation is dependent on this pathway and thus, the number of pre-follicle cells is subject to the effect of the Hh signalling pathway. <ref><pubmed>8620839</pubmed></ref> Further studies have also indicated the role played by this pathway in activating the Epidermal growth factor receptor (EGFR) signalling pathway as seen in the induction of EGFR by Hh in Drosophila head development. <ref><pubmed>10331974</pubmed></ref> In addition, research on Drosophila has indicated the direct effect of Hh signalling on tracheal branch patterning. <ref><pubmed>11290298</pubmed></ref><br />
<br />
Despite ongoing research on "Drosophila melanogaster" to uncover the workings of the Hedgehog signalling pathway, further research is needed to confirm and further current findings. In addition, it is evident that it is through the study of these fruit flies that we are able to gain a basis of understanding of the causes of certain human diseases and thus propel research into treatments for sufferers. <br />
<br />
===Blockage of Shh Signalling in Forebrain Neuroectoderm of Chick Embryos===<br />
<br />
The Hedgehog signalling pathway plays a significant role in embryonic development, particularly of the forebrain. Due to its role in development of craniofacial features by contributing to the epithelia of the frontonasal, maxillary, and pharyngeal ectoderm, a disruption in this pathway can result in a variety of birth deformities including holoprosencephaly (HPE), where the prosencephalon (forebrain) fails to divide into 2 separate hemispheres, telencephalon and diencephalon <ref>Holoprosencephaly - NORD (National Organization for Rare Disorders). (2016). NORD (National Organization for Rare Disorders). Retrieved 10 September 2016, from http://rarediseases.org/rare-diseases/holoprosencephaly/</ref>, as well as cleft lip and palate. The function of Sonic Hedgehog (Shh) and its signalling pathway on the formation of forebrain neuroectoderm was studied in chick embryos.<br />
<br />
It was found that the disruption of Shh signalling in the neural tube of chick embryos resulted in the lack of division of the forebrain into the diencephalon and telencephalon. This is in fact, as stated earlier, the fundamental cause of the rare condition, holoprosencephaly. It was discovered that the Shh signalling pathway in the diencephalon was responsible for gene expression in the telencephalon. <br />
<br />
In addition, through experimentation on chick embryos it was found that through Shh signalling the development of the forebrain regulates and controls facial morphogenesis, particularly of the upper and middle face. Therefore, interference with Shh signalling in the forebrain prevents this intrinsic communication, thus hindering Shh expression in facial ectoderm. This results in brain malformation accompanied by facial disfiguration as seen in patients suffering from HPE. Other malformations caused by blockage of Shh signalling in craniofacial development include, hypotelorism (decreased space between the orbits), growth restriction as well as cleft lip and palate as mentioned previously. <br />
<br />
A commonality discovered among all forms of Shh signalling disruption was two facial defects, “the loss of mediolateral expansion of the face and absence of proximodistal outgrowth of the frontonasal prominence”<ref><pubmed>15979605</pubmed></ref> (Ralph et al., 2005). Through reference to studies performed on chick and mice embryos, it was found that Shh signalling is particularly vital in development of maxillary and frontonasal components of the cranium.<br />
<br />
This breakthrough study on the inhibition of Shh signalling in chick embryos has significantly filled the gap in our understanding of the Sonic Hedgehog signalling pathway. It is evident that this pathway is crucial in the development of the forebrain and in turn regulates and controls the development of the facial skeleton. This is further proven through the observation that in the event of Shh signalling inhibition there is a development of craniofacial malformations.<br />
<br />
=== Shh knockout mice ===<br />
<br />
Extensive research on Shh knockout mice allowed discovery of the roles of Shh in embryonic development and patterning of the limb buds and sclerotomes, and maintenance of the notochord. <ref><pubmed>8837770</pubmed></ref> These mice expressed defects in the cephalic neural tube with the fusion of telencephalic and optic vesicles. Through this research it is evident that Shh is partially responsible for the subdivision of the eye field through forebrain optic stalk development, along with formation of the ventral midline. It is these forebrain abnormalities established in the absence of Shh that results in congenital malformations of holoprosencephaly, development of a single nasal chamber and other facial defects in humans. <br />
<br />
The absence of the vertebral column including, the intervertebral discs and vertebrae along with the medial regions of the ribs were observed within Shh knockout mice. This lack of sclerotome derivatives indicates the role of Shh in maintenance or expansion of sclerotome cell population (Chiang et al., 1996). In addition, though the role of Shh in patterning the anterior-posterior limb axis is evident through anterior limb bud cell death in the absence of Shh, it is also responsible for the development of proximal-distal limb segments, particularly in the patterning of structures at the level of or distal to the latent elbow and knee joints. <ref><pubmed>11476582</pubmed></ref> This was perceived after observing the incomplete formation of distal limb structures with abnormal anterior-posterior axis formation (Chiang et al., 2001). Thus, Shh knockout mice provide great insight into the functions of Shh in embryonic development and the abnormalities formed in the absence of this signalling protein. <br />
<br />
== Clinical significance ==<br />
<br />
===Gorlin Syndrome===<br />
Gorlin syndrome, also known as nevoid basal cell carcinoma syndrome, is a heritable disease resulting from heterozygousity in Hh receptor, Patched (PTC). The PTC gene encodes a protein which binds sonic hedgehog (Shh) and it is this binding which inhibits the Hh signalling pathway. However mutation of PTC leads to activation of the pathway <ref><pubmed>9620294</pubmed></ref>. The syndrome is characteristic of skin cancer basal cell carcinoma and cerebellum cancer medulloblastoma. 1-2% of medulloblastomas and 0.5% of basal cell carcinomas are attributable to the disease. Patients present with craniofacial and brain abnormalities such as cleft palate, strabismus, macrocephaly, abnormal development of the corpus callosum and frontal bossing, with an overall overgrown appearance. Skeletal defects such as of the shoulder, ribs and vertebrae are often seen, as well immobile thumbs and polydactyly, which is a deformity of the hand or feet in which they have one or more extra fingers or toes. Apart from physical anomalies, patients have an increased risk of tumours throughout the body including cardiac, ovarian fibromas, ovarian dermoid cysts, meningiomas, and fibrosarcomas. Additionally with time, patients eventually undergo intracranial calcification and dyskeratotic pitting of the hands and feet whereby skin cells prematurely convert to keratin <ref><pubmed>8681379</pubmed></ref>.<br />
<br />
====Holoprosencephaly====<br />
Holoprosencephaly (HPE) is a congenital disease caused by incomplete division of the prosencephalon (embryonic forebrain) into separate lobes of the cerebral hemispheres. The Shh gene has been identified as a HPE-causing gene however recent evidence has also investigated into the PTC gene, which acts to repress Shh signalling. A gain in repressive action of PTC is seen, leading to decreased Shh signalling, and thus HPE <ref><pubmed>11941477</pubmed></ref>. Clinical expression is variable between patients and is dependent upon the 3 forms of increasing severity: lobar, semi-lobar and alobar HPE, where patients can present with right and left ventricles however with a continuous frontal cortex in lobar HPE, to carrying a single cerebral ventricle in alobar HPE. Along with forebrain abnormalities, facial anomalies are also seen including midline cleft lip and/or flat nose, ocular hypotelorism characteristic of a small distance between the eyes. In severe rare cases of cyclopia, a non-functioning nose may be observed in the form of proboscis and the patient may present with a single eye at the root of the nose <ref><pubmed>20583177</pubmed></ref>. Furthermore, patients with HPE often develop a large number of medical issues including epilepsy, mental retardation, thyroid and adrenal hypoplasia due to lack of hypothalamus or pituitary gland development, and diabetes insipidus. <br />
<br />
====Cleft Lip and Palate====<br />
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=== Diagnosis ===<br />
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== Current research ==<br />
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==Quiz==<br />
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==Glossary==<br />
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{| class="pretty table"<br />
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===Additional Glossary Links===<br />
[[A|A]] | [[B|B]] | [[C|C]] | [[D|D]] | [[E|E]] | [[F|F]] | [[G|G]] | [[H|H]] | [[I|I]] | [[J|J]] | [[K|K]] | [[L|L]] | [[M|M]] | [[N|N]] | [[O|O]] | [[P|P]] | [[Q|Q]] | [[R|R]] | [[S|S]] | [[T|T]] | [[U|U]] | [[V|V]] | [[W|W]] | [[X|X]] | [[Y|Y]] | [[Z|Z]] | [[Numbers|#]]<br />
<br />
== References ==</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=249822
User:Z5018221
2016-10-07T02:54:55Z
<p>Z5018221: /* Lab Attendance */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
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<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 15:19, 2 September 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:21, 9 September 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:05, 16 September 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:43, 23 September 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:54, 7 October 2016 (AEDT)<br />
<br />
==Lab 1 Assessment==<br />
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<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
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Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
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{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
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==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
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Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
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<pubmed>18166081</pubmed><br />
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{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
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Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
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Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
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==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
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PMID 27486480<br />
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http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
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== Lab 3 Assessment ==<br />
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{| width=95%<br />
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| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
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[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
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[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
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[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
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==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
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{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
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{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
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{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
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</quiz><br />
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==Lab 5 Assessment==<br />
Questionnaire completed<br />
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==Lab 6 Assessment==<br />
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Cleft palate, often occurring in conjunction with cleft lip is among the most common congenital malformations and involves abnormal facial development during gestation. Between the 4th week and the 6th-7th weeks of development, migrating neural crest cells of the anterior neural tube with the mesodermal cells form the facial primordia. From here the filtrum and primary palate are formed, by the merging of the nasal prominences to form the intermaxillary segment, which then fuses with the maxillary prominences to form the upper lip. The palatal shelves additionally grow out from the maxillary prominences. <br />
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This complex process involves a variety of signalling molecules, transcriptions factors and cell-cell interactions, and an interference in the cascade can lead to the failure of fusion of the facial primordia, resulting in facial clefting. An important transcription factor expressed primarily in the palatal shelves and tongue during palatogenesis is TBX22. TBX22 is a member of a family of transcriptional regulators containing a common DNA-binding domain, the T-box. Mutations of the TBX22 gene have been strongly linked with syndromic X linked cleft palate producing clefting of the palate and ankyloglossia, otherwise known as tongue-tie. <br />
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Mutations of the TBX22 gene commonly occur as nucleotide alterations where amino acid substitutions, deletions and transitions may occur as well as sequence variants close to splice sites. These mutations lead to formation of truncated proteins, with missense mutations affecting amino acids within the DNA binding T box domain. Missense mutations of TBX22 primarily occur at major areas of contact with the target DNA, affecting and reducing the protein’s ability to bind to the DNA or even other binding proteins in the transcriptional complex. This loss in binding to DNA and other crucial proteins within the transcriptional complex therefore affects the downstream cascade of gene activation, and as a result the development and fusion of the palate. <br />
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Through research it has been shown that a variety of genetic mutations involving genes such as TBX22, PVRL1, and IRF6 lead to facial clefting. However the location and type of mutation does not completely determine the severity of the clefting but rather environmental factors. Environmental factors such as alcohol, tobacco, and toxin exposure during pregnancy can also impact palatogenesis. <br />
<br />
1) <pubmed>14729838</pubmed><br />
2) <pubmed>14722155</pubmed><br />
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==Lab 7 Assessment==<br />
1) What is/are the dystrophin mutation(s)?<br />
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In approximately 65% of patients with Duchenne Muscular Dystrophy (DMD), lack of dystrophin is due to a frameshift mutation caused by gene deletions, which give rise to premature stop codons, hence preventing translation to protein. In the remaining cases, point mutations and small gene insertions/deletions are the underlying causes leading to formation of truncated protein, with exon duplications responsible for approximately 5% of all mutations.<br />
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2) What is the function of dystrophin?<br />
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DMD is caused by the absence of the protein dystrophin in skeletal, smooth and cardiac muscle, a protein present at the membrane of muscle fibres and an important link between the cytoplasmic and extracellular matrix of the muscle fibre. Due to this it has an important mechanical role where it maintains the strength of muscle fibres, as, in fibres lacking dystrophin, normal contraction weakens the fibre and leads to degeneration. As well as playing a mechanical role, it is also involved in signalling pathways such as pathways for production of nitric oxide, and the Ras/MPAK pathway.<br />
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3) What other tissues/organs are affected by this disorder?<br />
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Dystrophin is not only present in skeletal muscle, but also in cardiac muscle. The heart can be affected whereby the conduction tissues can get damaged and lead to abnormal rhythms such as arrthymia and dysrhythmia, or pump abnormally leading to cardiomyopathy. <br />
Weakening of respiratory muscles is additionally seen in patients, leading to difficulties in breathing. At this point ventilation machines are utilized to assist with breathing. <br />
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4) What therapies exist for DMD?<br />
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Over the years, patients with DMD have begun to live longer into their 20s and 30s showing an improvement in treatment. Various factors such as earlier and continuous use of corticosteroids, routine flu and pneumococcal injections, and intense physical therapy have influenced these results. Currently, the therapies available for DMD aim to manage the disease rather than cure it. Corticosteroids are given to the patient to improve muscle function and strength however with continued use into adulthood, side effects such as weight gain, hypertension, hyperglycemia, cataracts and osteoporosis begin to surface. Patients also undergo physiotherapy to maintain function of the limbs, particularly of the upper extremity. A daily stretch routine targeting the muscles of the forearm wrist and fingers is crucial so the patient can still control their wheelchair, for example. <br />
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Research continues in the field of the disease and potential therapies have been proposed, in particular gene therapies. An example of a potential gene therapy for DMD patients is the CRISPR/Cas 9 system. This system is a genome modification technology, first identified in bacteria, re-engineered to 2 components of an RNA guide sequence and a DNA endonuclease. The system has now been modified to function in mammalian cells where it could generate random mutations or targeted repair, hence has been proposed as a potential way of disease modification.<br />
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In order to correct the mutant phenotype of DMD the CRISPR/Cas9 system was recently employed on a mouse MdX model. It was found that the CRISPR/Cas 9 was able to repair a large population of skeletal myocytes, with the myocytes showing a good survival rate. Although the CRISPR/Cas 9 system has been successful in animal studies, further research must now be undertaken for employment in human patients.<br />
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5) What animal models are available for muscular dystrophy?<br />
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Currently, the most common animal model used for DMD research is the MDX mouse, which contains a nonsense mutation abolishing formation of dystrophin. However to bridge the gap between these models and human patients in terms of vector production and immune response, canine models are now being utilized. Dog breeds of the Golden Retriever, Rottweiler and Cavalier King Charles have been reported as dystrophin deficient due to gene deletions. <br />
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References<br />
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1) <pubmed>27515321</pubmed><br />
2) <pubmed>16887341</pubmed><br />
3) <pubmed>27619714 </pubmed><br />
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== Lab 9 Assessment==<br />
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===Team 1===<br />
<br />
In terms of the topic of WnT signalling pathway, the page is beginning to come together with a great amount of information. What I particularly like is how the different concepts introduced in the page have been explained for e.g. the different WnT pathways. However the content for each pathway does not seem to be consistent. While the canonical pathway addresses the mechanism, the non-canonical one doesn’t. I would suggest constructing a table to compare the similarities and differences between the various pathways, and adding images or shorts clips with audio to represent the elements of the pathways in a different form. This would not only enhance the look of your page but also make it more interactive for the audience. <br />
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A great positive is to see links to research articles have been provided for the audience to access if they are interested to read on further. The links are short and easy to see, and direct you straight to the article on Pubmed, a reliable source. An effort has also been made to summarise the article, however the summary should be available as a simple breakdown so the audience can refer to it if they struggle to understand. The summaries include some jargon that can be further simplified. <br />
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In relation to criteria 1, the key points have definitely been highlighted and the signalling pathway has been associated with the fetus, however to make it more interesting and satisfy criteria 5, possibly construct a table or briefly outline how WnT signalling is involved in other areas such as Type 2 Diabetes and Cancer. Furthermore, to relate the topic back to embryological development explore the pathway in areas such as gastrulation rather than only talking about skin development. <br />
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Lastly to satisfy criteria 3, attempt to include in text citations within the paragraphs, instead of displaying references towards the end of the page. Overall, great job in gathering and highlighting key features, and backing up your information with relevant articles!<br />
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===Team 2===<br />
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A job well done with the introduction! The introduction is brief however manages to link the topic to embryonic development, different medical conditions, whilst also outlining the function and elements of the pathway. Being brief and succinct, it allows the viewer to continue exploring the page without experiencing confusion at the first lot of information. Further to this, the history of the pathway is formatted well and is not too overwhelming or boring. It is evident you have decided ‘Current Areas of Research’ will also be included in your page which is a great idea as you have included a section on History. This would ensure your Wiki flows well, and covers the pathway from start to finish. <br />
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Images have been included to visually represent the elements of the general pathway, as well as the elements specific to the pathway in cardiac development, which forms a great aid for viewers in understanding the content. Videos explaining the different canonical and non- canonical pathways could also be included for viewers with a video learning preference. <br />
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Use of in text citations neatens the layout of information and enables viewers to access the article should they find the point interesting. Numerous subheadings have been included which further break down the page into small sections of information. This is a fantastic positive as viewers can locate information in which they are interested in easily instead of having to read through long paragraphs of text. I feel as if linking the topic clinically is extremely important which you have done a great job in! Along with the text explaining the disease, you could possibly include a table stating the disease, the mutation, and the symptoms for viewers after a more easy, accessible format. <br />
<br />
Throughout the topics covered, a lot of jargon is utilized, however a full glossary has not been provided. A glossary should definitely be included for terms such as ‘gastrulation’, ‘kinases’ or ‘cardiogenesis’ in order to satisfy criteria 4. Additionally, the page does not cater for viewers interested in further reading up on the topic. To ensure criteria’s 4 and 5 are met, links to interesting facts or articles could be provided so the audience has access to more information if they would like to further their understanding. With a few improvements this Wiki page can definitely prove helpful in understanding the pathway! <br />
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===Team 3===<br />
<br />
A great introduction to the topic, allowing the reader to slowly transition into the more in-depth points! I particularly like how you have broken down the different constituents of the pathway such as the receptors and protein subtypes and provided a succinct table outlining their function and clinical significance before moving onto the mechanism. Although the ‘FGF Subtype’ table has proven to be effective and helpful, the table on ‘History’ does not seem to be thorough and is very limited. Possibly extending the table by researching more developments in the field of FGF Signalling could make it appear more complete. <br />
<br />
Effort has been made to include a hand drawn image of the signalling pathway, which serves as a great source of aid in understanding how the pathway works whilst reading the text beside it. In saying that, effort should be further made to include a complete glossary and ensure terms such as ‘receptor dimerization’ ‘morphogenesis’ are broken down for the reader in order to satisfy criteria 4. This is not only seen in the ‘Signal Transduction’ section but also throughout the other sections. As you have included a fantastic image on bone development to represent the information visually, it would also be a good idea to post up images covering the other areas of embryonic development, such as kidney and inner ear development! You could even consider including short clips explaining these processes to make the page more interactive. <br />
<br />
It is clear a decision has been made to talk about ‘Animal Models’. As well as including text on the topic, a possible option could be including a table briefly outlining which animal model has contributed to what knowledge in relation to the pathway in order to simplify the information. <br />
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A particular highlight of the Wiki page is the use of a quiz. It is great to see viewers can test their understanding of the topic towards the end and challenge themselves! For the correct option to each question a link to a supporting article or particular section of the page can be provided so the viewer can revisit the information should they have answered the question incorrectly. Overall a great use of tables, images and interactive components!<br />
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===Team 5===<br />
<br />
Well done on constructing a thorough Wiki page on the topic of T-box Genes and their Signalling! Viewing the page it is evident numerous headings and subheadings have been provided to accommodate for the large amount of information gathered. Starting off with the introduction I like how you have included a section on what T’-box exactly means, however the information provided in this section talks about the history significantly, hence to turn this into a positive I would suggest adding a table or timeline outlining the major events and discoveries in the past to present this information in a complete, meaningful way. This issue is also seen with the section ‘Origins of the T-box genes’ where major discoveries are highlighted and in which year they occurred. This information can also merge with the history timeline/table. <br />
<br />
Within the ‘What does T-box mean?’ section you have also added information on which animal studies were undertaken for the discoveries. To avoid spreading of information and causing confusion for the reader, you could either construct a table to show which animal study was completed in which year, and what discovery it led to as 3 columns, or bring this information down to the section ‘Animal Models’. In saying that, you have attempted to utilize a table and the table works very well with the topic of the different T-box genes, and would prove great help for the viewer. <br />
<br />
It is great to see T-box genes and Signalling has been explored further in the field of embryonic development. Extensive information is provided with good use of in- text citations, allowing the reader to navigate to relevant articles. The ability to navigate could be further improved by providing an accessible link to the ‘Abnormalities’ section in a case where you are directing the reader to the section for further information, instead of plain text. Beneath each section for e.g. ‘Limb Development’ Pubmed links have been provided to relevant articles, which is a fantastic idea, however the links have no indication whatsoever of what the article is about. You could add a sentence each next to the links briefly stating what the article is exploring in relation to limb development. <br />
<br />
Overall with a few more images, possibly some interactive components such as clips, and a knowledge testing short exam or quiz this Wiki page will stand out. Remember to ensure your information flows well by placing it within appropriate sections!<br />
<br />
===Team 6===<br />
<br />
It is great to see an in-depth overview of the TGF beta Signalling pathway and it’s mechanism of action. The page is off to a great start and with a few key improvements it can turn into a successful one! Firstly, I like the use of images to aid the reader in understanding the content better should they be a visual learner. By reading the text on the way the pathway works it is clear it is a complicated process hence a suggestion would be to add short clips/animations to simplify it for the viewer. <br />
<br />
Under your introduction an attempt has been made to briefly highlight the main features of the pathway, however a negative of this section is that a lot of the content is basically listed. For example it is mentioned TGF-beta is part of a larger TGF superfamily comprising of different members such as activins and GDFs. Instead of listing, try presenting your information in a different format such as a table with s few columns stating the member, it’s function, and possibly what a mutation could lead to. <br />
<br />
Additionally it is also stated that TGF beta has certain functions such as controlling angiogenesis however doesn’t expand on the ‘other’ functions it has. To turn this into a positive, dedicate different sections on how the pathway is involved in angiogenesis, hormone secretion, proliferation etc. If there are too many functions to fit onto the page, you could shift a few to your ‘Further Reading’ section as an option if the reader would like to explore further into the pathway’s functions, or construct a hidden table that the viewer can expand if they wish to. <br />
<br />
In order to satisfy criteria 3, in text citations should be incorporated within text so the viewer has an option to access the article if they find the statement interesting. A reference list has been posted with a few references however ensure they are cited in the correct format. Overall a good start!</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=249576
User:Z5018221
2016-10-06T11:33:32Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 15:19, 2 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:21, 9 September 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:05, 16 September 2016 (AEST)<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:43, 23 September 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
<br />
<br />
== Lab 3 Assessment ==<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
<br />
[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
<br />
<br />
==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
<br />
{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
<br />
{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
<br />
{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
<br />
</quiz><br />
<br />
==Lab 5 Assessment==<br />
Questionnaire completed<br />
<br />
<br />
==Lab 6 Assessment==<br />
<br />
Cleft palate, often occurring in conjunction with cleft lip is among the most common congenital malformations and involves abnormal facial development during gestation. Between the 4th week and the 6th-7th weeks of development, migrating neural crest cells of the anterior neural tube with the mesodermal cells form the facial primordia. From here the filtrum and primary palate are formed, by the merging of the nasal prominences to form the intermaxillary segment, which then fuses with the maxillary prominences to form the upper lip. The palatal shelves additionally grow out from the maxillary prominences. <br />
<br />
This complex process involves a variety of signalling molecules, transcriptions factors and cell-cell interactions, and an interference in the cascade can lead to the failure of fusion of the facial primordia, resulting in facial clefting. An important transcription factor expressed primarily in the palatal shelves and tongue during palatogenesis is TBX22. TBX22 is a member of a family of transcriptional regulators containing a common DNA-binding domain, the T-box. Mutations of the TBX22 gene have been strongly linked with syndromic X linked cleft palate producing clefting of the palate and ankyloglossia, otherwise known as tongue-tie. <br />
<br />
Mutations of the TBX22 gene commonly occur as nucleotide alterations where amino acid substitutions, deletions and transitions may occur as well as sequence variants close to splice sites. These mutations lead to formation of truncated proteins, with missense mutations affecting amino acids within the DNA binding T box domain. Missense mutations of TBX22 primarily occur at major areas of contact with the target DNA, affecting and reducing the protein’s ability to bind to the DNA or even other binding proteins in the transcriptional complex. This loss in binding to DNA and other crucial proteins within the transcriptional complex therefore affects the downstream cascade of gene activation, and as a result the development and fusion of the palate. <br />
<br />
Through research it has been shown that a variety of genetic mutations involving genes such as TBX22, PVRL1, and IRF6 lead to facial clefting. However the location and type of mutation does not completely determine the severity of the clefting but rather environmental factors. Environmental factors such as alcohol, tobacco, and toxin exposure during pregnancy can also impact palatogenesis. <br />
<br />
1) <pubmed>14729838</pubmed><br />
2) <pubmed>14722155</pubmed><br />
<br />
<br />
==Lab 7 Assessment==<br />
1) What is/are the dystrophin mutation(s)?<br />
<br />
In approximately 65% of patients with Duchenne Muscular Dystrophy (DMD), lack of dystrophin is due to a frameshift mutation caused by gene deletions, which give rise to premature stop codons, hence preventing translation to protein. In the remaining cases, point mutations and small gene insertions/deletions are the underlying causes leading to formation of truncated protein, with exon duplications responsible for approximately 5% of all mutations.<br />
<br />
2) What is the function of dystrophin?<br />
<br />
DMD is caused by the absence of the protein dystrophin in skeletal, smooth and cardiac muscle, a protein present at the membrane of muscle fibres and an important link between the cytoplasmic and extracellular matrix of the muscle fibre. Due to this it has an important mechanical role where it maintains the strength of muscle fibres, as, in fibres lacking dystrophin, normal contraction weakens the fibre and leads to degeneration. As well as playing a mechanical role, it is also involved in signalling pathways such as pathways for production of nitric oxide, and the Ras/MPAK pathway.<br />
<br />
3) What other tissues/organs are affected by this disorder?<br />
<br />
Dystrophin is not only present in skeletal muscle, but also in cardiac muscle. The heart can be affected whereby the conduction tissues can get damaged and lead to abnormal rhythms such as arrthymia and dysrhythmia, or pump abnormally leading to cardiomyopathy. <br />
Weakening of respiratory muscles is additionally seen in patients, leading to difficulties in breathing. At this point ventilation machines are utilized to assist with breathing. <br />
<br />
4) What therapies exist for DMD?<br />
<br />
Over the years, patients with DMD have begun to live longer into their 20s and 30s showing an improvement in treatment. Various factors such as earlier and continuous use of corticosteroids, routine flu and pneumococcal injections, and intense physical therapy have influenced these results. Currently, the therapies available for DMD aim to manage the disease rather than cure it. Corticosteroids are given to the patient to improve muscle function and strength however with continued use into adulthood, side effects such as weight gain, hypertension, hyperglycemia, cataracts and osteoporosis begin to surface. Patients also undergo physiotherapy to maintain function of the limbs, particularly of the upper extremity. A daily stretch routine targeting the muscles of the forearm wrist and fingers is crucial so the patient can still control their wheelchair, for example. <br />
<br />
Research continues in the field of the disease and potential therapies have been proposed, in particular gene therapies. An example of a potential gene therapy for DMD patients is the CRISPR/Cas 9 system. This system is a genome modification technology, first identified in bacteria, re-engineered to 2 components of an RNA guide sequence and a DNA endonuclease. The system has now been modified to function in mammalian cells where it could generate random mutations or targeted repair, hence has been proposed as a potential way of disease modification.<br />
<br />
In order to correct the mutant phenotype of DMD the CRISPR/Cas9 system was recently employed on a mouse MdX model. It was found that the CRISPR/Cas 9 was able to repair a large population of skeletal myocytes, with the myocytes showing a good survival rate. Although the CRISPR/Cas 9 system has been successful in animal studies, further research must now be undertaken for employment in human patients.<br />
<br />
5) What animal models are available for muscular dystrophy?<br />
<br />
Currently, the most common animal model used for DMD research is the MDX mouse, which contains a nonsense mutation abolishing formation of dystrophin. However to bridge the gap between these models and human patients in terms of vector production and immune response, canine models are now being utilized. Dog breeds of the Golden Retriever, Rottweiler and Cavalier King Charles have been reported as dystrophin deficient due to gene deletions. <br />
<br />
References<br />
<br />
1) <pubmed>27515321</pubmed><br />
2) <pubmed>16887341</pubmed><br />
3) <pubmed>27619714 </pubmed><br />
<br />
== Lab 9 Assessment==<br />
<br />
===Team 1===<br />
<br />
In terms of the topic of WnT signalling pathway, the page is beginning to come together with a great amount of information. What I particularly like is how the different concepts introduced in the page have been explained for e.g. the different WnT pathways. However the content for each pathway does not seem to be consistent. While the canonical pathway addresses the mechanism, the non-canonical one doesn’t. I would suggest constructing a table to compare the similarities and differences between the various pathways, and adding images or shorts clips with audio to represent the elements of the pathways in a different form. This would not only enhance the look of your page but also make it more interactive for the audience. <br />
<br />
A great positive is to see links to research articles have been provided for the audience to access if they are interested to read on further. The links are short and easy to see, and direct you straight to the article on Pubmed, a reliable source. An effort has also been made to summarise the article, however the summary should be available as a simple breakdown so the audience can refer to it if they struggle to understand. The summaries include some jargon that can be further simplified. <br />
<br />
In relation to criteria 1, the key points have definitely been highlighted and the signalling pathway has been associated with the fetus, however to make it more interesting and satisfy criteria 5, possibly construct a table or briefly outline how WnT signalling is involved in other areas such as Type 2 Diabetes and Cancer. Furthermore, to relate the topic back to embryological development explore the pathway in areas such as gastrulation rather than only talking about skin development. <br />
<br />
Lastly to satisfy criteria 3, attempt to include in text citations within the paragraphs, instead of displaying references towards the end of the page. Overall, great job in gathering and highlighting key features, and backing up your information with relevant articles!<br />
<br />
===Team 2===<br />
<br />
A job well done with the introduction! The introduction is brief however manages to link the topic to embryonic development, different medical conditions, whilst also outlining the function and elements of the pathway. Being brief and succinct, it allows the viewer to continue exploring the page without experiencing confusion at the first lot of information. Further to this, the history of the pathway is formatted well and is not too overwhelming or boring. It is evident you have decided ‘Current Areas of Research’ will also be included in your page which is a great idea as you have included a section on History. This would ensure your Wiki flows well, and covers the pathway from start to finish. <br />
<br />
Images have been included to visually represent the elements of the general pathway, as well as the elements specific to the pathway in cardiac development, which forms a great aid for viewers in understanding the content. Videos explaining the different canonical and non- canonical pathways could also be included for viewers with a video learning preference. <br />
<br />
Use of in text citations neatens the layout of information and enables viewers to access the article should they find the point interesting. Numerous subheadings have been included which further break down the page into small sections of information. This is a fantastic positive as viewers can locate information in which they are interested in easily instead of having to read through long paragraphs of text. I feel as if linking the topic clinically is extremely important which you have done a great job in! Along with the text explaining the disease, you could possibly include a table stating the disease, the mutation, and the symptoms for viewers after a more easy, accessible format. <br />
<br />
Throughout the topics covered, a lot of jargon is utilized, however a full glossary has not been provided. A glossary should definitely be included for terms such as ‘gastrulation’, ‘kinases’ or ‘cardiogenesis’ in order to satisfy criteria 4. Additionally, the page does not cater for viewers interested in further reading up on the topic. To ensure criteria’s 4 and 5 are met, links to interesting facts or articles could be provided so the audience has access to more information if they would like to further their understanding. With a few improvements this Wiki page can definitely prove helpful in understanding the pathway! <br />
<br />
===Team 3===<br />
<br />
A great introduction to the topic, allowing the reader to slowly transition into the more in-depth points! I particularly like how you have broken down the different constituents of the pathway such as the receptors and protein subtypes and provided a succinct table outlining their function and clinical significance before moving onto the mechanism. Although the ‘FGF Subtype’ table has proven to be effective and helpful, the table on ‘History’ does not seem to be thorough and is very limited. Possibly extending the table by researching more developments in the field of FGF Signalling could make it appear more complete. <br />
<br />
Effort has been made to include a hand drawn image of the signalling pathway, which serves as a great source of aid in understanding how the pathway works whilst reading the text beside it. In saying that, effort should be further made to include a complete glossary and ensure terms such as ‘receptor dimerization’ ‘morphogenesis’ are broken down for the reader in order to satisfy criteria 4. This is not only seen in the ‘Signal Transduction’ section but also throughout the other sections. As you have included a fantastic image on bone development to represent the information visually, it would also be a good idea to post up images covering the other areas of embryonic development, such as kidney and inner ear development! You could even consider including short clips explaining these processes to make the page more interactive. <br />
<br />
It is clear a decision has been made to talk about ‘Animal Models’. As well as including text on the topic, a possible option could be including a table briefly outlining which animal model has contributed to what knowledge in relation to the pathway in order to simplify the information. <br />
<br />
A particular highlight of the Wiki page is the use of a quiz. It is great to see viewers can test their understanding of the topic towards the end and challenge themselves! For the correct option to each question a link to a supporting article or particular section of the page can be provided so the viewer can revisit the information should they have answered the question incorrectly. Overall a great use of tables, images and interactive components!<br />
<br />
===Team 5===<br />
<br />
Well done on constructing a thorough Wiki page on the topic of T-box Genes and their Signalling! Viewing the page it is evident numerous headings and subheadings have been provided to accommodate for the large amount of information gathered. Starting off with the introduction I like how you have included a section on what T’-box exactly means, however the information provided in this section talks about the history significantly, hence to turn this into a positive I would suggest adding a table or timeline outlining the major events and discoveries in the past to present this information in a complete, meaningful way. This issue is also seen with the section ‘Origins of the T-box genes’ where major discoveries are highlighted and in which year they occurred. This information can also merge with the history timeline/table. <br />
<br />
Within the ‘What does T-box mean?’ section you have also added information on which animal studies were undertaken for the discoveries. To avoid spreading of information and causing confusion for the reader, you could either construct a table to show which animal study was completed in which year, and what discovery it led to as 3 columns, or bring this information down to the section ‘Animal Models’. In saying that, you have attempted to utilize a table and the table works very well with the topic of the different T-box genes, and would prove great help for the viewer. <br />
<br />
It is great to see T-box genes and Signalling has been explored further in the field of embryonic development. Extensive information is provided with good use of in- text citations, allowing the reader to navigate to relevant articles. The ability to navigate could be further improved by providing an accessible link to the ‘Abnormalities’ section in a case where you are directing the reader to the section for further information, instead of plain text. Beneath each section for e.g. ‘Limb Development’ Pubmed links have been provided to relevant articles, which is a fantastic idea, however the links have no indication whatsoever of what the article is about. You could add a sentence each next to the links briefly stating what the article is exploring in relation to limb development. <br />
<br />
Overall with a few more images, possibly some interactive components such as clips, and a knowledge testing short exam or quiz this Wiki page will stand out. Remember to ensure your information flows well by placing it within appropriate sections!<br />
<br />
===Team 6===<br />
<br />
It is great to see an in-depth overview of the TGF beta Signalling pathway and it’s mechanism of action. The page is off to a great start and with a few key improvements it can turn into a successful one! Firstly, I like the use of images to aid the reader in understanding the content better should they be a visual learner. By reading the text on the way the pathway works it is clear it is a complicated process hence a suggestion would be to add short clips/animations to simplify it for the viewer. <br />
<br />
Under your introduction an attempt has been made to briefly highlight the main features of the pathway, however a negative of this section is that a lot of the content is basically listed. For example it is mentioned TGF-beta is part of a larger TGF superfamily comprising of different members such as activins and GDFs. Instead of listing, try presenting your information in a different format such as a table with s few columns stating the member, it’s function, and possibly what a mutation could lead to. <br />
<br />
Additionally it is also stated that TGF beta has certain functions such as controlling angiogenesis however doesn’t expand on the ‘other’ functions it has. To turn this into a positive, dedicate different sections on how the pathway is involved in angiogenesis, hormone secretion, proliferation etc. If there are too many functions to fit onto the page, you could shift a few to your ‘Further Reading’ section as an option if the reader would like to explore further into the pathway’s functions, or construct a hidden table that the viewer can expand if they wish to. <br />
<br />
In order to satisfy criteria 3, in text citations should be incorporated within text so the viewer has an option to access the article if they find the statement interesting. A reference list has been posted with a few references however ensure they are cited in the correct format. Overall a good start!</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=Talk:2016_Group_Project_6&diff=249574
Talk:2016 Group Project 6
2016-10-06T11:30:53Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Project2016discussionheader}}<br />
=Peer Review=<br />
<br><br />
<br><br />
<u>Group 6:</u><br />
<br><br />
<br><br />
<b>Positive aspects of the project and suggested improvements:</b><br />
<br><br />
<br><br />
The authors of group 6 have created a variety of subheadings related to the TGF-beta signalling pathway, including the nature of the growth factor, its mechanism of action, history and emerging research (criteria 1). Authors have also provided two diagrams related to TGF-beta signalling which reinforces the description of TGF signalling provided (criteria 2). These diagrams allow for a much simpler interpretation of the signalling process described and assist in teaching at the peer level (criteria 4). It appears that the authors are beginning to conduct investigations into new research surrounding TGF-beta signalling, thus indicating that they are attempting to research beyond formal teaching activities (criteria 5). <br />
<br><br />
<br><br />
<br />
Whilst it is excellent that multiple subheadings have been provided, a possible improvement would be to include a much larger variety of subheadings which cover the scope of TGF-beta’s role in embryonic development, abnormalities, types of TGF receptors and animal models. This may allow audiences to understand the big picture surrounding this signalling pathway which will assist in the understanding of the information already provided. Another improvement to this page would be to include more images under different subheadings. One example would be to include an image or table showing the history of discovery surrounding discovery of this signalling pathway. <br />
<br><br />
<br><br />
<br />
<b>Negative aspects of the project and suggested improvements:</b><br />
<br><br />
<br><br />
<br />
Although there were positive aspects of this project, there were also numerous negative aspects which may be improved. One key negative feature of the page was that the authors did not discuss the role of TGF-beta signalling in the context of embryonic development, hence meaning they failed to meet criteria 6. To ensure that this criterion is met, authors may conduct research into the involvement of TGF-beta in specific processes that occur during embryonic development, perhaps organ development and growth of different primitive structures. In addition, whilst the authors have provided a history of the TGF-beta signalling pathway, the history appears to be very brief. Thus an improvement which may be implemented would be to include a more extensive background regarding the history of discovery of the pathway. It was also noticed that no tables were utilised within the page. A possible improvement would be to include a table describing different abnormalities and their causes in the context of disruption of the TGF-beta pathway. A table may also be utilised to describe different subtypes of TGF-beta receptors as well as their functions during embryonic development. Tables may be utilised as they will assist in the process of teaching at the peer level (criteria 4), particularly because they convey information in an orderly and organised manner. <br />
<br><br />
<br><br />
<br />
The authors of this project also failed to meet criteria 3, in that only one source was referenced in the process of the signalling pathway and also no in-text citations were provided. In addition, authors failed to reference the image file named, “Process of TGF-beta signalling pathway 01”. It is vital that all sources are referenced correctly in order to ensure that the copyright laws regarding the use of information are adhered to. The final negative aspect of the project was that the page did not flow very well, in that subheadings were arranged in a disorderly fashion. An example of this is the inclusion of the subheading labelled, “history of TGF-beta signalling pathway”, towards the end of the page. Since such a subheading provides a background surrounding the pathway, a possible improvement would be to include this subheading at the beginning of the page. By ensuring the orderliness of the page, this creates a sense of coherency between subheadings, thus making the page more appealing and engaging.<br />
<br />
===Group 6===<br />
<br />
It was good to see some progress being made on the project with the development of some subheadings and the inclusion of an image. In saying this, a better selection of headings and sub-headings could be developed to break down the topic of TGF beta signaling pathway. I think the sub-headings provided under the general heading of ‘Introduction’ could form the main headings of this research project and they could then be further broken down into various subheadings. In addition, the subheading of TGF-beta could be eliminated and this definition could be incorporated into the glossary or general introduction of the topic instead. Furthermore, more focus is needed on the influence of this pathway on embryological development and the abnormalities caused by mutations to the pathway and its components. For example, there has been mention of the effect of TGF-beta in ‘development of the embryo and adult organism, as well as cell growth, immune function and hormone secretion’ but further discussion has not been pursued. <br />
<br />
Though a good description of the ‘process of TGF-beta signaling pathway’ has been provided, it could be further improved by referencing the images included in this section in your text (e.g. refer to Figure 1) to aid one’s understanding of the concept being explored. In addition, a timeline of events could be provided to explore the history of this pathway and it would be appropriate to begin with the discovery of TGF-beta. To a reader, information on ‘transformed or malignant cells’ seems unrelated to the TGF-beta signaling pathway even though it may be in fact be related, due to lack of discussion of this pathway or TGF-beta in this description. In regards to the section on ‘Limitations’, what types of limitations are you trying to explore? Limitations in research? This could be better defined by appropriately allocating subheadings to each of the sections.<br />
<br />
Though you are heading in the right direction, spending time to produce a basic layout of your project by creating appropriate headings and subheadings would be useful in breaking down the concepts needed to be explored in this pathway. This could be achieved by communicating with group members through the discussion page and providing feedback and suggestions. In addition, greater focus is required in referencing and citing your work to ensure researchers and authors are acknowledged for their work. Also, by exploring animal models of the TGF-beta pathway and the effect of this research in understanding this pathway in humans and its influence on embryological development, you could greatly increase the quality of your work. You could also try and make your project more interactive and engaging through the inclusion of tables, images and diagrams. I hope this helps! Good luck!<br />
<br />
=== Group 6 Critical Assessment===<br />
It is great to see an in-depth overview of the TGF beta Signalling pathway and it’s mechanism of action. The page is off to a great start and with a few key improvements it can turn into a successful one! Firstly, I like the use of images to aid the reader in understanding the content better should they be a visual learner. By reading the text on the way the pathway works, it is clear it is a complicated process hence a suggestion would be to add short clips/animations to simplify it for the viewer. <br />
<br />
Under your introduction an attempt has been made to briefly highlight the main features of the pathway, however a negative of this section is that a lot of the content is basically listed. For example it is mentioned TGF-beta is part of a larger TGF superfamily comprising of different members such as activins and GDFs. Instead of listing, try presenting your information in a different format such as a table with s few columns stating the member, it’s function, and possibly what a mutation could lead to. <br />
<br />
Additionally it is also stated that TGF beta has certain functions such as controlling angiogenesis however doesn’t expand on the ‘other’ functions it has. To turn this into a positive, dedicate different sections on how the pathway is involved in angiogenesis, hormone secretion, proliferation etc. If there are too many functions to fit onto the page, you could shift a few to your ‘Further Reading’ section as an option if the reader would like to explore further into the pathway’s functions, or construct a hidden table that the viewer can expand if they wish to. <br />
<br />
In order to satisfy criteria 3, in text citations should be incorporated within text so the viewer has an option to access the article if they find the statement interesting. A reference list has been posted with a few references however ensure they are cited in the correct format. Overall a great start!</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=Talk:2016_Group_Project_5&diff=249572
Talk:2016 Group Project 5
2016-10-06T11:29:20Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Project2016discussionheader}}<br />
=Peer Review=<br />
<br><br />
<br><br />
<u>Group 5: </u><br />
<br><br />
<br><br />
<br />
<b>Positive aspects of the project and suggested improvements:</b><br />
<br><br />
<br><br />
Upon reviewing this page, it is clear that group 5 has provided numerous headings and subheadings related to Tbx-genes ranging from origins of the genes, their function in embryonic development, abnormalities, history and animal models (criteria 1 and 6). In doing so, the group has also ventured to provide an in-depth explanation of each subheading. Take for example the subheading named, “limb development”, the authors have provided an in-depth description into the role of T-box transcription factors in limb development whilst utilising a diagram to reinforce this description (criteria 2). It also appears that in-text citations have been correctly used to reference the sources of data in most cases (criteria 3). The authors have utilised diagrams and a table to describe various components of the T-box gene ranging from the different types of T-box genes to its mechanisms in embryonic development (criteria 4). The extensive use of diagrams allows the audience to develop a holistic understanding of the various subheadings included, as these diagrams convey the description provided in a visual manner (criteria 5). It is also evident that the group has conducted research into animal models and evolution of the T-box gene, thus demonstrating that the group has investigated areas of research beyond formal teaching activities (criteria 5).<br />
<br><br />
<br><br />
Improvements which may be made to this page would be to include a timeline regarding the history of the T-box family, as this will display the information in a much more organised and appealing manner. Another improvement which may be made would be to include a YouTube video to introduce the signalling process in development, such as in cardiac and limb development for example. In order to make the wikipage interactive, a further improvement which may be made would be to include a set of multiple choice questions at the end of the page which ask questions about the content covered. <br />
<br><br />
<br><br />
<b>Negative aspects of the project and suggested improvements:</b><br />
<br><br />
<br><br />
<br />
Alongside the various positive aspects of this project, there are few negative aspects. A negative aspect identified includes the use of images from Wikipedia pages more than once. It was stated that only one Wikipedia page was allowed to be included as a source. Therefore a suggestion would be to obtain images and data from research articles rather than from Wikipedia pages, as research articles are often a more reliable source of data. It was also noticed that images were not utilised to describe different abnormalities associated with the TBX gene, hence a possible improvement would be to include images depicting such abnormalities. These images may make this section of the page more appealing and engaging to audiences. <br />
<br><br />
<br><br />
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It was also noticed that the image titled “Evolution of the T box gene family”, was incorrectly referenced. Therefore, it is suggested that the authors of the project ensure that the original author of the image are correctly referenced to ensure that copyright laws are not breached. The final negative aspect of the project was that the “Ancient origins and evolution of the T-box gene family” subheading appeared out of place in the page. Therefore a possible improvement would be to include evolution of the T-box gene under the “Origins of the T-box gene” subheading at the beginning of the page as this will create a sense of consistency in the page.<br />
<br><br />
<br><br />
<br />
===Group 5===<br />
<br />
First of all, well done on making significant progress on your project! You have addressed all aspects of the pathway involving T-Box genes through subdivision into various headings and subheadings. I particularly liked how there was an inclusion of the specific T-Box gene affected in each of the abnormalities in the subheading itself. The only suggestion I would make is to combine the ‘Ancient origins and evolution of the T-Box gene family’ section with the origins of the ‘T-Box genes’ section to provide a more coherent description of the history of these pathway. You could even form a table to create a timeline of events. In addition, I think it would be beneficial to include the ‘What does T-Box mean?’ as an introduction to the ‘origins of the T-box genes’ section as there is overlap between these sections. <br />
<br />
The use of a table to describe the main T-box genes was helpful in providing a brief overview of the components of the pathway and their influence in embryological development. In addition, the link between T-Box genes and embryonic development has been explored considerably. In saying this, greater attention to detail must be paid to explaining abbreviations to aid one’s understanding of the concepts being discussed. For example, what is NKX2-5, Shh and OFT? Though you’ve explained that RA stands for retinoic acid in the ‘Organisms used in animal models for T-Box’ section, this same explanation is not provided in the ‘Limb development’ section where you have discussed that ‘RA and Shh both induced Tbx2’. These small changes will significantly improve the quality of your work. <br />
<br />
The inclusion of abnormalities provides great insight into the role of T-Box genes in development. In saying this, though you have explored the effect of the mutation of these genes in animal models, more information is required to explain the effect of these mutations in humans and how they come about. Furthermore, under the heading of ‘Animal models’ there has been discussion mainly of the ‘brachyury gene’ which seems unrelated to animal models due to the lack of a proper introduction. I found the following section (organisms used in animal models for T-Box) to be a better introduction to the topic of animal models. In addition, there has been mention of a number of animal models ‘Drosophila, Xenopus, zebrafish, avians, and mice’ yet only marsupials and amphioxus has been discussed. This could be potentially misleading to readers. <br />
<br />
Overall, a fantastic effort has been made. Not only have you touched upon nearly every section of the project, but have included some excellent diagrams and tables which aid understanding of this pathway. In saying this, it is noted that two Wikipedia images have been used though it has been suggested that only one of the images utilised can be from Wikipedia. All information provided was also appropriately referenced and cited. In addition, I think it would be useful to utilise the discussion page to encourage interaction between group members as it allows individuals to provide feedback and suggestions. Hope this helps!<br />
<br />
===Group 5 Critical Assessment===<br />
Well done on constructing a thorough Wiki page on the topic of T-box Genes and their Signalling! Viewing the page it is evident numerous headings and subheadings have been provided to accommodate for the large amount of information gathered. Starting off with the introduction I like how you have included a section on what T’-box exactly means, however the information provided in this section talks about the history significantly, hence to turn this into a positive I would suggest adding a table or timeline outlining the major events and discoveries in the past to present this information in a complete, meaningful way. This issue is also seen with the section ‘Origins of the T-box genes’ where major discoveries are highlighted and in which year they occurred. This information can also merge with the history timeline/table. <br />
<br />
Within the ‘What does T-box mean?’ section you have also added information on which animal studies were undertaken for the discoveries. To avoid spreading of information and causing confusion for the reader, you could either construct a table to show which animal study was completed in which year, and what discovery it led to as 3 columns, or bring this information down to the section ‘Animal Models’. In saying that, you have attempted to utilize a table and the table works very well with the topic of the different T-box genes, and would prove great help for the viewer. <br />
<br />
It is great to see T-box genes and Signalling has been explored further in the field of embryonic development. Extensive information is provided with good use of in- text citations, allowing the reader to navigate to relevant articles. The ability to navigate could be further improved by providing an accessible link to the ‘Abnormalities’ section in a case where you are directing the reader to the section for further information, instead of plain text. Beneath each section for e.g. ‘Limb Development’ Pubmed links have been provided to relevant articles, which is a fantastic idea, however the links have no indication whatsoever of what the article is about. You could add a sentence each next to the links briefly stating what the article is exploring in relation to limb development. <br />
<br />
Overall with a few more images, possibly some interactive components such as clips, and a knowledge testing short exam or quiz this Wiki page will stand out. Remember to ensure your information flows well by placing it within appropriate sections!<br />
<br />
<br />
<br />
Some searches to get us started:<br />
[http://www.ncbi.nlm.nih.gov/sites/gquery?term=t-box ''T-box'']<br />
[http://www.ncbi.nlm.nih.gov/sites/gquery?term=tbx ''tbx'']<br />
<br />
[[User:Z5020373|Z5020373]] ([[User talk:Z5020373|talk]]) 14:44, 26 August 2016 (AEST)<br />
PMID 25294936 - a relatively recent article that provides background info on the T-box gene family<br />
PMID 16285859<br />
<br />
[[User:Z3516832|Z3516832]] ([[User talk:Z3516832|talk]]) 14:52, 26 August 2016 (AEST)<br />
http://www.columbia.edu/itc/hs/medical/humandev/2007/HD15/HD15.pdf<br />
<br />
[[User:Z5020373|Z5020373]] ([[User talk:Z5020373|talk]]) 11:32, 16 September 2016 (AEST) Does anyone know how to draw up a table on the page? Thanks.</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=Talk:2016_Group_Project_3&diff=249570
Talk:2016 Group Project 3
2016-10-06T11:27:52Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Project2016discussionheader}}<br />
<br />
==Peer Review==<br />
<br />
===Group 3===<br />
<br />
You guys have made a good start on your project! I particularly liked how the headings were subdivided appropriately into smaller subheadings as it effectively broke down the FGFR pathway and made the page easy to navigate. Though you have included a short and succinct introduction, I think it should address all the sections being discussed to give the reader a better overview of your project. In addition, the use of a table to explore the timeline of research of the FGF pathway was an excellent idea but I think the text above the table could be incorporated into the table itself and a more extensive timeline could be provided. <br />
<br />
Though it was good that you provided a brief overview of the FGFR pathway, you’ve only discussed the components of the pathway rather than the pathway itself. Furthermore, when discussing signal transduction, I think you should be more specific when explaining the process, for example when you mentioned ‘which leads to changes in gene transcription through interactions with DNA’, it causes changes in transcription in which genes and through interactions with which DNA? In saying this, it was wonderful to see the inclusion of a hand-drawn diagram which represents not only your understanding of the pathway but also aids readers understanding of the FGFR pathway. <br />
<br />
A good overview has been provided to explain the role of FGFs in embryonic development. The only suggestion I can make is to provide explanations or full names of the abbreviations to aid understanding of the concepts explored. For example, what is ETV1 and EWSR1? By explaining what these abbreviations are the reader will gain better understanding on how they function to help maintain FGF10 expression. In terms of the section on abnormalities, a succinct and coherent introduction was provided. There was a good description of the morphological changes produced by these mutations along with the cause of these abnormalities. There isn’t much I would change in this section except for maybe explaining FGFR2 mutation. <br />
<br />
Overall, you guys have done a fantastic job! I thought the inclusion of a quiz was particularly innovative as it makes your project interactive and thus, aids the learning process. Everything was well cited and referenced and it was wonderful to see the use of an original diagram. It was also good to see all groups members contributing to the discussion page which indicates effective communication within the team. <br />
<br />
===Group 3 Critical Assessment===<br />
A great introduction to the topic, allowing the reader to slowly transition into the more in-depth points! I particularly like how you have broken down the different constituents of the pathway such as the receptors and protein subtypes and provided a succinct table outlining their function and clinical significance before moving onto the mechanism. Although the ‘FGF Subtype’ table has proven to be effective and helpful, the table on ‘History’ does not seem to be thorough and is very limited. Possibly extending the table by researching more developments in the field of FGF Signalling could make it appear more complete. <br />
<br />
Effort has been made to include a hand drawn image of the signalling pathway, which serves as a great source of aid in understanding how the pathway works whilst reading the text beside it. In saying that, effort should be further made to include a complete glossary and ensure terms such as ‘receptor dimerization’ ‘morphogenesis’ are broken down for the reader in order to satisfy criteria 4. This is not only seen in the ‘Signal Transduction’ section but also throughout the other sections. As you have included a fantastic image on bone development to represent the information visually, it would also be a good idea to post up images covering the other areas of embryonic development, such as kidney and inner ear development! You could even consider including short clips explaining these processes to make the page more interactive. <br />
<br />
It is clear a decision has been made to talk about ‘Animal Models’. As well as including text on the topic, a possible option could be including a table briefly outlining which animal model has contributed to what knowledge in relation to the pathway in order to simplify the information. <br />
<br />
A particular highlight of the Wiki page is the use of a quiz. It is great to see viewers can test their understanding of the topic towards the end and challenge themselves! For the correct option to each question a link to a supporting article or particular section of the page can be provided so the viewer can revisit the information should they have answered the question incorrectly. Overall a great use of tables, images and interactive components!<br />
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<br />
<br />
==<u><font size="4.5">Comments by Group 3</font></u>==<br />
[[User:Z5015686|Z5015686]] ([[User talk:Z5015686|talk]]) 12:36, 19 August 2016 (AEST) I thought looking into how prenatal cannabis exposure influences signalling during development might be interesting<br />
<br />
[[User:Z5017002|Z5017002]] ([[User talk:Z5017002|talk]]) 12:47, 19 August 2016 (AEST) Ooh cool idea, I agree that looks really interesting, there seems to be a lot of literature about its influence on brain development<br />
<br />
[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]])z5015544[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]]) Thats excellent, what about the sonic hedgehog pathway?<br />
<br />
[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]])Other ideas[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]]) WNT Signaling Pathway is another one to look at<br />
<br />
How can we harvest stem cells from the embyro for use in later life - z5015337<br />
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[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]])z5015544[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]]) Ok guys I created a couple of subheadings and provided a brief history. Make sure to use primary research articles that are peer-reviewed because I just spoke to Dr Hill and noticed he stressed that a lot.<br />
<br />
[[User:Z5015337|Z5015337]] ([[User talk:Z5015337|talk]]) I have scoured through the projects of old to get a better idea about what is expected from us for this project - [[User:Z5015337|Z5015337]] ([[User talk:Z5015337|talk]])<br />
<br />
[[User:Z5015337|Z5015337]] ([[User talk:Z5015337|talk]])I found this giant slab of text regarding the structures of the receptors involved from a journal article and I am working through culling it down for a usable structure definition: FGF receptors and FGF signal transduction. FGFRs are modular proteins comprising 3 immunoglobulin domains (IgI, IgII and IgIII). IgI and IgII are separated by an acidic box (AD). IgII contains a heparin binding domain (HBD). The IgIII domain is followed by a unique transmembrane (TM), a juxtamembrane (JM) and a kinase domain (KD) interrupted by an interkinase domain (IKD). FGF ligands linked to heparin sulfate proteoglycan (HSPG) bind to IgII and IgIII of FGFR. This results in the dimerization and the subsequent transactivation by phosphorylation of specific tyrosine residues. The main two transduction pathways involve the phospholipase C-γ (PLCγ) and the Ras/MAP kinase. The SH2 domain of the PLCγ interacts with the phosphorylated Y766 of the activated receptor. The activated PLCγ hydrolyzes the phosphatidyl-inositol-4,5-diphosphate (PIP2) to inositol-1,4,5-triphophate (IP3) and the diacylglycerol (DAG). IP3 releases Ca2+ while DAG activates the protein kinase C-δ (PKCδ). Activated PKCδ activates Raf by phosphorylating its S338 and stimulates the downstream pathway in a Ras independent manner. The main pathway involves the interaction of the docking protein FRS2α with the amino-acid residues 407–433 (Xu et al., 1998). This protein is activated by phosphorylation on multiple tyrosine residues and subsequently interacts and activates Grb2 linked to Sos, a nucleotide exchange factor involved in the activation of Ras. Activated Ras then activates Raf which stimulates MEK which in turn phosphorylates the MAP kinase ERK. This last activated component translocates to the nucleus and phosphorylates specific transcription factors of the Ets family which in turn activate expression of specific FGF target genes. P: phosphorylation<br />
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[[User:Z5015686|Z5015686]] ([[User talk:Z5015686|talk]]) 18:31, 14 September 2016 (AEST) Hey guys I've just changed our subheadings so we can better allocate something for each of us to write on this week. More then happy to change them! Just came across these while I was researching. Did everyone maybe want to put their name next to something they are able to research or chuck in new subheadings that interest them?<br />
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[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]]) 14:31, 16 September 2016 (AEST)Hey guys, here is the link for omim. Type in the name of the gene and it will give you different articles about it: http://www.omim.org/[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]]) 14:31, 16 September 2016 (AEST)<br />
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[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]]) 14:41, 16 September 2016 (AEST)Things to include: Flow diagram of the FGFR pathway, 3D diagram of the FGF protein (can be hand-drawn)[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]]) 14:41, 16 September 2016 (AEST)<br />
<br />
[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]]) 23:22, 28 September 2016 (AEST)Hey guys, hope you're all enjoying the break. Just thought I would let you know I've added a hand drawn diagram and a table too. If anyone finds more information about specific receptor functions in embryo development please add it to the table.[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]]) 23:22, 28 September 2016 (AEST)<br />
<br />
[[User:Z5015686|Z5015686]] ([[User talk:Z5015686|talk]]) 12:35, 29 September 2016 (AEST) '''just moved this from our main page''' Extra Resources<br />
Useful review articles that may be worth a read through: <br />
http://onlinelibrary.wiley.com/doi/10.1002/wdev.176/full<br />
http://www.nature.com.wwwproxy0.library.unsw.edu.au/nrd/journal/v8/n3/pdf/nrd2792.pdf <br />
http://www.sciencedirect.com.wwwproxy0.library.unsw.edu.au/science/article/pii/S0012160605006184<br />
http://www.nature.com.wwwproxy0.library.unsw.edu.au/nrm/journal/v14/n3/full/nrm3528.html<br />
http://onlinelibrary.wiley.com.wwwproxy0.library.unsw.edu.au/doi/10.1002/jcp.24649/full <br />
http://genesdev.cshlp.org/content/29/14/1463.full (FGF signalling and skeletogenesis, specifically how mutations to the FGF signalling pathway may be responsible for skeletal diseases)<br />
<br />
[[User:Z5015544|Z5015544]] ([[User talk:Z5015544|talk]]) 01:14, 4 October 2016 (AEDT)Looking really good guys, I think we should try and expand beyond what has been covered in the lectures. Maybe we can look at new research involving FGF. We can also look at FGF in animals and how it affects limb development. Let me know what you guys think</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=Talk:2016_Group_Project_2&diff=249568
Talk:2016 Group Project 2
2016-10-06T11:26:00Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Project2016discussionheader}}<br />
=Peer Review=<br />
<br><br />
<br><br />
<u>Group 2:</u><br />
<br><br />
<br><br />
<b>Positive aspects of the project and suggested improvements: </b><br />
Group 2 has provided a variety of different topics related to the Notch receptor, such as its molecular pathway, its role in embryonic developing both in humans and animals as well as abnormalities caused by disruption in the receptor’s normal function (criteria 6). This variety is excellent, as it informs the audience of various aspects of the Notch receptor ranging from normal to abnormal development as well as newly emerging research (criteria 1.). Group 2 has also utilised both tables and diagrams to represent Notch receptor’s history and signalling pathway respectively (criteria 2). The use of diagrams is a great idea as it allows peers to understand the complexity of the signalling pathway in a much simpler manner (criteria 4). <br />
<br><br />
<br><br />
In addition, the authors have correctly utilised in text citations when referencing all sources and have created a list of references at the conclusion of the page (criteria 3). Group 2 also investigated specific components of organ development which was another magnificent feature of their page, such that they divided cardiovascular development into different stages including “heart valve development” and “trabeculation” for example. This allows for an in-depth understanding of organ development with respect to the Notch receptor, rather than a general overview of the receptor’s involvement (criteria 5 and 6). The authors also have extended beyond Notch’s involvement in human embryonic development by exploring its role in animal embryonic development (criteria 5).<br />
<br><br />
<br><br />
Although there are many positives, a possible improvement to this outstanding wiki would be to include a table of the different types of Notch receptors that exist and their different roles in embryonic development. This will allow the audience to understand that there is not just a single receptor playing a role in embryonic development but multiple. Another suggestion would be to add more subheadings under the “Central nervous system” development, as this subheading appears to have a lot less information compared to others. Also, it is obvious that there are different pathways for this receptor such as “Canonical” and “Non-canonical”, therefore it would be a great idea to include a youtube video to summarise these pathways and reinforce the in-depth description already provided on the page. <br />
<br><br />
<br><br />
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<b>Negative aspects of the project and suggested improvements:</b><br />
<br><br />
<br><br />
<br />
It was also noticed that a variety of terms were utilised which were not defined in the glossary such as “cyclins”, “pluripotent stem cells” and “ligands” for example. It is important to consider that the wiki should be able to teach at a peer level (criteria 4), as some students may not understand these terms. Therefore it is important to define them so audiences can develop a coherent understanding of the information. Another negative feature of the page was that it lacked interactivity. Indeed the page is very informative, however to further engage the audience, a suggestion would be to include a set of multiple choice questions at the end of the page which tests peers about the content covered.<br />
<br><br />
<br><br />
It was also noticed that the page had a very limited number of subheadings regarding Notch’s involvement in embryonic development. A possible improvement would be to investigate Notch’s involvement in organ systems other than Cardiovascular and central nervous system. This will add a greater variety to the page and provide a greater depth of understanding regarding the role of the Notch signalling pathway in embryonic development.<br />
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<br><br />
<br><br />
<br />
===Group 2===<br />
<br />
Well done on the progress you have made thus far! You guys have chosen appropriate headings and subheadings that effectively break down the Notch signalling pathway. A coherent introduction has been provided, giving a taste of what is to be expected in this project. The use of a table to explore the history of this signalling pathway was particularly useful in making the information understandable and relevant. Though you have done an excellent job, was there any reason you stopped at 1989? It may even be useful to create a brief timeline of events, thus allowing you to better explore current areas of research by considering past studies that have been performed.<br />
<br />
You’ve provided a good overview of the canonical pathway with the appropriate use of a diagram which aids reader’s understanding of the information provided. In saying this, I think it would be useful to expand on how this pathway is tightly controlled, is it through transcriptional regulation or through other means? In addition, it may be useful to explain the differences in the non-canonical and canonical pathways in terms of their significance and role in embryonic development. I’ve noticed that you have provided a general overview of the role of Notch signalling pathway in embryonic development, do these roles differ between the canonical and non-canonical pathways?<br />
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In addition, it’s good that you have included the role of the Notch signalling pathway in animal development as it explores the scope of this pathway beyond human embryology but it may also be useful to explore animal models in research, especially considering that the ‘first description of a “notch” defect’ was discovered in Drosophila. By combining the role of animal models in expanding our knowledge of the Notch signalling pathway with the effect of this pathway in animals, it provides a more rounded approach to explaining and discussing this signalling pathway. <br />
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I particularly like how you have included statistics in the ‘Abnormalities of Notch signalling’ section as it provides insight into the importance of this pathway in embryological development. You have successfully described the type of mutation that results in the particularly disease in most cases except for Alagille syndrome. More detail in how the mutation causes the syndrome would be useful with an explanation of how the mutation is brought about. <br />
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Overall, you guys have done a fantastic job! You have appropriately referenced and cited all the information provided and have included useful flowcharts, tables and diagrams that aid understanding of the text provided. Providing more detail to each of the sections and communicating with all your team members in the discussion page will ensure that you produce an excellent project! Good luck!<br />
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===Group 2 Critical Assessment===<br />
<br />
A job well done with the introduction! The introduction is brief however manages to link the topic to embryonic development, different medical conditions, whilst also outlining the function and elements of the pathway. Being brief and succinct, it allows the viewer to continue exploring the page without experiencing confusion at the first lot of information. Further to this, the history of the pathway is formatted well and is not too overwhelming or boring. It is evident you have decided ‘Current Areas of Research’ will also be included in your page which is a great idea as you have included a section on History. This would ensure your Wiki flows well, and covers the pathway from start to finish. <br />
<br />
Images have been included to visually represent the elements of the general pathway, as well as the elements specific to the pathway in cardiac development, which forms a great aid for viewers in understanding the content. Videos explaining the different canonical and non- canonical pathways could also be included for viewers with a video learning preference. <br />
<br />
Use of in text citations neatens the layout of information and enables viewers to access the article should they find the point interesting. Numerous subheadings have been included which further break down the page into small sections of information. This is a fantastic positive as viewers can locate information in which they are interested in easily instead of having to read through long paragraphs of text. I feel as if linking the topic clinically is extremely important which you have done a great job in! Along with the text explaining the disease, you could possibly include a table stating the disease, the mutation, and the symptoms for viewers after a more easy, accessible format. <br />
<br />
Throughout the topics covered, a lot of jargon is utilized, however a full glossary has not been provided. A glossary should definitely be included for terms such as ‘gastrulation’, ‘kinases’ or ‘cardiogenesis’ in order to satisfy criteria 4. Additionally, the page does not cater for viewers interested in further reading up on the topic. To ensure criteria’s 4 and 5 are met, links to interesting facts or articles could be provided so the audience has access to more information if they would like to further their understanding. With a few improvements this Wiki page can definitely prove helpful in understanding the pathway! <br />
<br />
<br />
<br />
[[User:Z3462474|Z3462474]] ([[User talk:Z3462474|talk]]) 07:15, 23 September 2016 (AEST) Hey no worries I hope you feel better soon! I won't be able to do as much during the midsem break which is why I've been doing lots this week. I'll have a look at that link thanks! Also I tried to make a Glossary but am having trouble with the coding side of it but I'll try fix it later to make it a proper glossary :)<br />
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<br><br />
[[User:Z5015014|Z5015014]] ([[User talk:Z5015014|talk]]) 21:00, 22 September 2016 (AEST) I'm so sorry I've been terrible with putting stuff on our page!! I know I said I would get some done this week but I've been sick these past few days and still recovering so I probably won't make it to the lab tomorrow. I'm having some trouble finding an image that summarises Notch signalling that we can use (most of the good ones I've found don't allow reuse) but I'll keep looking. I'll definitely do a lot more during the midsem break. sorry again! I also found this link: http://www.omim.org/entry/190198 that looks like it has some really good references for different roles in development.<br />
<br />
[[User:Z5015014|Z5015014]] ([[User talk:Z5015014|talk]]) 14:27, 16 September 2016 (AEST) looks like a great picture so I think we can leave it. I just altered the formatting of the image a little bit, but feel free to change it back if you prefer the previous placement! also I think having the copyright info on the file page is enough. thanks for doing that, I'm still hunting out pictures as well. I've been busy this week with another group project but now that it's out of the way I should be able to do a lot more here. :)<br />
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[[User:Z3462474|Z3462474]] ([[User talk:Z3462474|talk]]) 09:21, 16 September 2016 (AEST) I found one that didnt look too complicated and also found that it allowed unrestricted use so I've added it into the cardio section of our page (we can always delete it later if need be), not 100% about my formatting though and whether I should include the legend/copyright notice directly on our page? If you click the image though its all there :) <br />
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[[User:Z5015014|Z5015014]] ([[User talk:Z5015014|talk]]) 23:08, 12 September 2016 (AEST) I've been looking around and found some images, but most of the time they involve a lot more detail than we need and I don't want to overcomplicate it. will keep researching this week and see if I can find some simpler diagrams. :) The images in that book look really good but yeah I'm not sure what the copyright details for that are. if it comes to it I think if we reproduce it by hand and credit the source then it's fine!<br />
<br />
[[User:Z3462474|Z3462474]] ([[User talk:Z3462474|talk]]) 13:50, 12 September 2016 (AEST) Has anyone found any good images to use for our page? I have found a couple of diagrams on cardiac development and Notch in this book chapter: http://www.sciencedirect.com.wwwproxy0.library.unsw.edu.au/science/article/pii/S0070215310920115 but am still looking to the copyright restrictions etc and thought I'd check everyone's opinion<br />
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[[User:Z3462474|Z3462474]] ([[User talk:Z3462474|talk]]) 09:22, 9 September 2016 (AEST) Hey everyone, I have added some of my notes to the main page, they are still a work in progress though! I'll continue to research the roles of Notch in the development of the different systems<br />
<br />
[[User:Z3462474|Z3462474]] ([[User talk:Z3462474|talk]]) 10:04, 2 September 2016 (AEST) Just found this online textbook titled 'Notch Signaling : Methods and Protocols' http://www.springerprotocols.com.wwwproxy0.library.unsw.edu.au/BookToc/doi/10.1007/978-1-4939-1139-4<br />
<br />
This one also looks like it might be helpful: http://www.sciencedirect.com.wwwproxy0.library.unsw.edu.au/science/bookseries/00702153/92<br />
<br />
<br />
[[User:Z3462474|Z3462474]] ([[User talk:Z3462474|talk]]) 14:27, 26 August 2016 (AEST) Here are some reviews I have found that could be a helpful starting point: <br />
<br />
Notch signalling at a glance: http://jcs.biologists.org/content/joces/126/10/2135.full.pdf <br />
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Signalling pathways for neural development: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4369499/pdf/WJSC-7-437.pdf<br />
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Notch's role in diabetic neuropathy https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3677813/pdf/nihms473246.pdf<br />
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Notch in cardio development and disease http://circres.ahajournals.org/content/118/1/e1.full<br />
<br />
[[User:Z5015014|Z5015014]] ([[User talk:Z5015014|talk]]) 14:28, 26 August 2016 (AEST) here's the embryology site page for [[Developmental Signals - Notch|Notch signalling]]!<br />
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[[User:Z5015014|Z5015014]] ([[User talk:Z5015014|talk]]) 14:31, 26 August 2016 (AEST) I also found a review article for Notch signalling in the common fruit fly, which could be a good idea for a subsection: PMID 12369105 ''General outlines of the molecular genetics of the Notch signalling pathway in Drosophila melanogaster: a review''.<br />
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[[User:Z5015014|Z5015014]] ([[User talk:Z5015014|talk]]) 14:44, 26 August 2016 (AEST) and here's some more reviews: PMID 22397947 ''Non-canonical Notch signaling: emerging role and mechanism'' and PMID 21828089 ''Notch signaling: simplicity in design, versatility in function''.<br />
<br />
[[User:Z5014803|Z5014803]] ([[User talk:Z5014803|talk]])<br />
https://www.researchgate.net/publication/264164124_Introduction_to_Notch_Signaling This seems like a good link for the history and discovery of the pathway<br />
<br />
[[User:Z5014803|Z5014803]] ([[User talk:Z5014803|talk]])<br />
https://embryo.asu.edu/pages/notch-signaling-pathway-embryogenesis Can be used for introduction<br />
<br />
<br />
<br />
[[User:Z3462474|Z3462474]] ([[User talk:Z3462474|talk]]) 12:41, 19 August 2016 (AEST) Signalling in neural embryonic development looks interesting! Particularly the paper about NSCs and psychiatric disorders.<br />
<br />
[[User:Z5015014|Z5015014]] ([[User talk:Z5015014|talk]]) 21:59, 18 August 2016 (AEST): Hedgehog signalling (specifically SHH signalling) sounds really interesting!<br />
<br />
[[User:Z5014803|Z5014803]] ([[User talk:Z5014803|talk]]) 22:39, 18 August 2016 (AEST): Bone Morphogenetic Proteins (BMP) signalling in development looks interesting<br />
<br />
[[User:Z3491219|Z3491219]] ([[User talk:Z3491219|talk]]) I think looking at how in utero exposure to cigarette smoke affects fetal ovarian development signalling would be interesting.</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=Talk:2016_Group_Project_1&diff=249566
Talk:2016 Group Project 1
2016-10-06T11:23:24Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Project2016discussionheader}}<br />
=Peer Review=<br />
<font size="4"><u>Group 1:</u></font><br />
<br><br />
<br><br />
<b>Positive aspects of the project and suggested improvements:</b><br />
<br><br><br />
Upon assessment of this project, it appears that the authors have devised a variety of subheadings related to the signalling pathway of the Wnt receptor in embryonic development which is excellent. The group has also began investigating the involvement of Wnt in numerous aspects of embryonic development such as skin formation. The use of subheadings and headings related to the Wnt receptor partially meets criteria 1 and 2 assessment. It also appears that the group has cited and referenced sources for some of the information utilised, particularly when describing the “Caronical Pathway”. This also partially meets criteria 3 for this assessment. The group has also attempted to explore abnormalities in the Wnt pathway by describing interruptions in the pathway and its relation to cancer which is very interesting. They have therefore attempted to research ideas related to this receptor that extend beyond formal teaching activities, by explaining the link between Wnt abnormalities and disease (criteria 5). <br />
<br><br />
<br><br />
Whilst there are the positive aspects of the page, improvements can still be made to ensure that the group satisfies the first five points of the marking criteria. Firstly, although there appears to be subheadings, there only appear to be few and therefore it would be excellent to add more subheadings. Subheadings may relate to the history of the Wnt signalling pathway or even subtypes of the receptor as well as their respective functions. In addition, whilst the group appear to have cited some of their sources, it is important to cite all sources, particularly when gathering data under the “Non-canonical pathway” subheading. Although a series of articles have been referred to, it is vital that the group includes in-text citations in order for the audience to determine the source for each segment of information. A suggestion would be to investigate more examples of diseases caused by abnormalities in the Wnt signalling pathway<br />
<br><br />
<br><br />
<b>Negative aspects of the project and suggested improvements:</b><br />
<br><br />
<br><br />
The group appeared to provide a general description of the abnormalities associated with disruption of the Wnt pathway; however they did not talk about abnormalities in the context of embryonic development. A suggestion would be to discuss Wnt abnormalities to the effect it has on embryonic development. It was also noticed that the group failed to include diagrams, tables or figures to reinforce the information. The use of diagrams would assist the audience in developing a visual understanding of the information presented and also makes the wiki page more appealing too. Therefore, a suggestion would be to use diagrams and figures. For example, a diagram of the signalling pathway would be a suggestion. It was noticed that the page appears to have no introduction or history describing the Wnt receptor. Therefore, a possible improvement would be to include a brief introduction and history at the beginning of the page as well as a few diagrams to provide the audience with an insight into what the receptor’s purpose is before exploring its function in embryonic developing.<br />
<br><br />
<br><br />
In addition, it appears that the group has focused on the role of Wnt in skin development of the embryo only. A possible improvement would be to investigate the involvement of Wnt in other areas of embryonic development, perhaps the development of specific organ systems or other structures.<br />
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<br><br />
<br><br />
<br><br />
To all group members:<br />
*More info on pathway focusing on fetus development, and which pathway it is majorly part of - focus research on those body parts<br />
*Make your section presentable<br />
*At least one picture per section<br />
<br />
===Group 1===<br />
<br />
You guys have made significant progress on your project, managing to touch briefly on each section of your assignment. There have been some good choices of subheadings but I think some improvement can be made. For example, I think it would be useful to breakdown the general heading of ‘introduction’ into smaller subheadings so readers are made aware of what will be discussed in this section. It would also be useful to touch upon the importance of this pathway and thus, highlighting its significance in embryological development. <br />
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In terms of the content of the project, being only in the draft stage a considerable amount of editing is required. For example, there has been mention of the TCF/LEF family and though the use of this abbreviations is useful, I think it would be appropriate to initially include the full name and explain this term in brief detail. In addition, there has been discussion of the ‘canonical’ and ‘non-canonical’ pathways of WnT Signalling Pathway but you could consider discussing the significance of having these two separate pathways. Comparing and contrasting these two pathways may also assist in aiding one’s understanding of the topic. <br />
<br />
Though it is great that you have made progress, I think more detail is required in each section, particularly in linking the effect of these pathways on embryological development. Also, greater attention needs to paid to referencing and utilisation of studies that have dissected this signalling pathway. For example, greater emphasis can be placed on studies performed on ‘embryos of Xenopus laevis’ or the in vitro experiments on mice. Instead of saying ‘a study’ or ‘another study’ acknowledge the researchers of this study as it will increase the validity of your argument while providing readers with the opportunity to refer back to these papers for more information if required or interested. More detail is also required on the effect of this pathway on skin formation. One way this could be done is by expanding on the information already provided, for example, explain how ‘WnT signalling inhibits the ectoderm’s responsiveness to FGFs’ and provide a detailed explanation of the feedback mechanism. Though your topic is focusing on ‘WnT Signalling pathway in the skin of fetus’ It would be beneficial to explore the roles of Wnt signalling in other areas of embryological development as this could provide insight into the abnormalities caused by mutations in this pathway. In terms of the ‘what can go wrong’ section, try breaking this segment into the various embryological deficiencies that can develop through disruption of the WnT pathway and try and make it relevant by providing statistics. <br />
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Overall, you guys have done a fantastic job! It was good to see that all group members had contributed to the project. The main thing that requires improvement is the lack of detail. Through editing and inclusion of appropriate references and citations you can significantly improve the quality of your work. It would be useful to add some diagrams or images to help explain the pathway. In addition, try utilising your discussion page and communicating with your other team members. By providing feedback and suggestions you can assist in efficiently producing an excellent project. I hope this helps!! <br />
<br />
===Group 1 Critical Assessment===<br />
In terms of the topic of WnT signalling pathway, the page is beginning to come together with a great amount of information. What I particularly like is how the different concepts introduced in the page have been explained, for e.g. the different WnT pathways. However the content for each pathway does not seem to be consistent. While the canonical pathway addresses the mechanism, the non-canonical one doesn’t. I would suggest constructing a table to compare the similarities and differences between the various pathways, and adding images or shorts clips with audio to represent the elements of the pathways in a different form. This would not only enhance the look of your page but also make it more interactive for the audience. <br />
<br />
A great positive is to see links to research articles have been provided for the audience to access if they are interested to read on further. The links are short and easy to see, and direct you straight to the article on Pubmed, a reliable source. An effort has also been made to summarise the article, however the summary should be available as a simple breakdown so the audience can refer to it if they struggle to understand. The summaries include some jargon that can be further simplified. <br />
<br />
In relation to criteria 1, the key points have definitely been highlighted and the signalling pathway has been associated with the fetal development, however to make it more interesting and satisfy criteria 5, possibly construct a table or briefly outline how WnT signalling is involved in other areas such as Type 2 Diabetes and Cancer. Furthermore, to relate the topic back to embryological development explore the pathway in other areas such as gastrulation, rather than limiting discussion to skin development.<br />
<br />
Lastly to satisfy criteria 3, attempt to include in text citations within the paragraphs, instead of displaying references towards the end of the page. Overall, great job in gathering and highlighting key features, and backing up your information with relevant articles!<br />
<br />
<br />
==Notes==<br />
Just trying to simplify and understand the process and these are some of my notes !(z3417363)<br />
<br />
The inactive Wnt Pathway In a normal cell:<br />
<br />
In most normal cells the Wnt pathway is inactive. In the cytosol , the destruction complex is formed from the proteins beta catenin, GSK3 beta, Axin,APC, Ck1-alpha. The ubiquitin ligase beta TRCP is able to bind to beta catenin and transfer short ubiquitin peptides to beta-catenin. In other words the beta-catenin is phosphorolated and this beta catenin can then bound and be by a complex of protease (proteasome) . Thus a low level of cellular beta catenin is achieved. <br />
Therefore no beta catenin reaches the nucleus and the transcription factor of the TCF LEF family along with other proteins (groucho) binds to DNA and inhibits gene expression.<br />
So essentially when WnT is inactive, beta canenin is destroyed and does not reach nucleus and transcription is inhibited. <br />
<br />
The Active Wnt Pathway in a normal cell.<br />
<br />
Extracellular(outside cell) Wnt binds with the membrane receptor frizzled (FZD). The wnt pathway is activated and activates the cytosolic protein "dishevelled"(DSH) which induces dissociation of the protein destruction complex. Because the protein complex is destroyed beta- catenin is no longer modified by unbiquitin peptides/phosporolated and is not destroyed. Since the supply of beta catenin continues the level of beta catenin rises, first in the cytosol and later in the nucleus. Once the beta catenin reaches the nuclue it binds to the TCF LEF transcription factor which changes them from a transcriptional repressor into an activator. TCF itself activates an RNA polymerase which induces gene transcription.<br />
So essentially WnT starts gene transcription by allowing beta catenin to reach the nucleus.<br />
<br />
This is actually very similar to a tumour cell where the mutation of the protein complex also inhibits the destruction of beta catenin and allows it to grow in quantity and reach the nucleus and start gene expression. However this is not uncontrolled and can be compared to a car travelling with no brakes. Ultimately this abnormal proliferation leads to malignant adenocarcinoma (cancer).<br />
<br />
Use pubmed, biomedcentral journals==you can find it on pubmed just plug in the title and you will get the pubmed number>BMC developmental biology journal, journal of cell biology(cant use last 6months of research), proceeding national academy of science(can only use after 6months), public library of science omim<br />
include research labs, animations<br />
use the help tab<br />
where the terminlogy came from <br />
this is a student drawn image , based upon and give the reference</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=248864
User:Z5018221
2016-09-23T04:43:16Z
<p>Z5018221: /* Lab Attendance */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 15:19, 2 September 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:21, 9 September 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:05, 16 September 2016 (AEST)<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:43, 23 September 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
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Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
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{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
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==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
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Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
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<pubmed>18166081</pubmed><br />
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{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
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==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
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[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
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PMID 27486480<br />
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http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
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== Lab 3 Assessment ==<br />
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{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
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[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
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[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
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[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
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==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
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{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
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{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
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{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
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</quiz><br />
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==Lab 5 Assessment==<br />
Questionnaire completed<br />
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==Lab 6 Assessment==<br />
<br />
Cleft palate, often occurring in conjunction with cleft lip is among the most common congenital malformations and involves abnormal facial development during gestation. Between the 4th week and the 6th-7th weeks of development, migrating neural crest cells of the anterior neural tube with the mesodermal cells form the facial primordia. From here the filtrum and primary palate are formed, by the merging of the nasal prominences to form the intermaxillary segment, which then fuses with the maxillary prominences to form the upper lip. The palatal shelves additionally grow out from the maxillary prominences. <br />
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This complex process involves a variety of signalling molecules, transcriptions factors and cell-cell interactions, and an interference in the cascade can lead to the failure of fusion of the facial primordia, resulting in facial clefting. An important transcription factor expressed primarily in the palatal shelves and tongue during palatogenesis is TBX22. TBX22 is a member of a family of transcriptional regulators containing a common DNA-binding domain, the T-box. Mutations of the TBX22 gene have been strongly linked with syndromic X linked cleft palate producing clefting of the palate and ankyloglossia, otherwise known as tongue-tie. <br />
<br />
Mutations of the TBX22 gene commonly occur as nucleotide alterations where amino acid substitutions, deletions and transitions may occur as well as sequence variants close to splice sites. These mutations lead to formation of truncated proteins, with missense mutations affecting amino acids within the DNA binding T box domain. Missense mutations of TBX22 primarily occur at major areas of contact with the target DNA, affecting and reducing the protein’s ability to bind to the DNA or even other binding proteins in the transcriptional complex. This loss in binding to DNA and other crucial proteins within the transcriptional complex therefore affects the downstream cascade of gene activation, and as a result the development and fusion of the palate. <br />
<br />
Through research it has been shown that a variety of genetic mutations involving genes such as TBX22, PVRL1, and IRF6 lead to facial clefting. However the location and type of mutation does not completely determine the severity of the clefting but rather environmental factors. Environmental factors such as alcohol, tobacco, and toxin exposure during pregnancy can also impact palatogenesis. <br />
<br />
1) <pubmed>14729838</pubmed><br />
2) <pubmed>14722155</pubmed><br />
<br />
<br />
==Lab 7 Assessment==<br />
1) What is/are the dystrophin mutation(s)?<br />
<br />
In approximately 65% of patients with Duchenne Muscular Dystrophy (DMD), lack of dystrophin is due to a frameshift mutation caused by gene deletions, which give rise to premature stop codons, hence preventing translation to protein. In the remaining cases, point mutations and small gene insertions/deletions are the underlying causes leading to formation of truncated protein, with exon duplications responsible for approximately 5% of all mutations.<br />
<br />
2) What is the function of dystrophin?<br />
<br />
DMD is caused by the absence of the protein dystrophin in skeletal, smooth and cardiac muscle, a protein present at the membrane of muscle fibres and an important link between the cytoplasmic and extracellular matrix of the muscle fibre. Due to this it has an important mechanical role where it maintains the strength of muscle fibres, as, in fibres lacking dystrophin, normal contraction weakens the fibre and leads to degeneration. As well as playing a mechanical role, it is also involved in signalling pathways such as pathways for production of nitric oxide, and the Ras/MPAK pathway.<br />
<br />
3) What other tissues/organs are affected by this disorder?<br />
<br />
Dystrophin is not only present in skeletal muscle, but also in cardiac muscle. The heart can be affected whereby the conduction tissues can get damaged and lead to abnormal rhythms such as arrthymia and dysrhythmia, or pump abnormally leading to cardiomyopathy. <br />
Weakening of respiratory muscles is additionally seen in patients, leading to difficulties in breathing. At this point ventilation machines are utilized to assist with breathing. <br />
<br />
4) What therapies exist for DMD?<br />
<br />
Over the years, patients with DMD have begun to live longer into their 20s and 30s showing an improvement in treatment. Various factors such as earlier and continuous use of corticosteroids, routine flu and pneumococcal injections, and intense physical therapy have influenced these results. Currently, the therapies available for DMD aim to manage the disease rather than cure it. Corticosteroids are given to the patient to improve muscle function and strength however with continued use into adulthood, side effects such as weight gain, hypertension, hyperglycemia, cataracts and osteoporosis begin to surface. Patients also undergo physiotherapy to maintain function of the limbs, particularly of the upper extremity. A daily stretch routine targeting the muscles of the forearm wrist and fingers is crucial so the patient can still control their wheelchair, for example. <br />
<br />
Research continues in the field of the disease and potential therapies have been proposed, in particular gene therapies. An example of a potential gene therapy for DMD patients is the CRISPR/Cas 9 system. This system is a genome modification technology, first identified in bacteria, re-engineered to 2 components of an RNA guide sequence and a DNA endonuclease. The system has now been modified to function in mammalian cells where it could generate random mutations or targeted repair, hence has been proposed as a potential way of disease modification.<br />
<br />
In order to correct the mutant phenotype of DMD the CRISPR/Cas9 system was recently employed on a mouse MdX model. It was found that the CRISPR/Cas 9 was able to repair a large population of skeletal myocytes, with the myocytes showing a good survival rate. Although the CRISPR/Cas 9 system has been successful in animal studies, further research must now be undertaken for employment in human patients.<br />
<br />
5) What animal models are available for muscular dystrophy?<br />
<br />
Currently, the most common animal model used for DMD research is the MDX mouse, which contains a nonsense mutation abolishing formation of dystrophin. However to bridge the gap between these models and human patients in terms of vector production and immune response, canine models are now being utilized. Dog breeds of the Golden Retriever, Rottweiler and Cavalier King Charles have been reported as dystrophin deficient due to gene deletions. <br />
<br />
References<br />
<br />
1) <pubmed>27515321</pubmed><br />
2) <pubmed>16887341</pubmed><br />
3) <pubmed>27619714 </pubmed></div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=248594
User:Z5018221
2016-09-22T10:39:43Z
<p>Z5018221: /* Lab 7 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 15:19, 2 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:21, 9 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:05, 16 September 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
<br />
<br />
== Lab 3 Assessment ==<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
<br />
[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
<br />
<br />
==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
<br />
{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
<br />
{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
<br />
{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
<br />
</quiz><br />
<br />
==Lab 5 Assessment==<br />
Questionnaire completed<br />
<br />
<br />
==Lab 6 Assessment==<br />
<br />
Cleft palate, often occurring in conjunction with cleft lip is among the most common congenital malformations and involves abnormal facial development during gestation. Between the 4th week and the 6th-7th weeks of development, migrating neural crest cells of the anterior neural tube with the mesodermal cells form the facial primordia. From here the filtrum and primary palate are formed, by the merging of the nasal prominences to form the intermaxillary segment, which then fuses with the maxillary prominences to form the upper lip. The palatal shelves additionally grow out from the maxillary prominences. <br />
<br />
This complex process involves a variety of signalling molecules, transcriptions factors and cell-cell interactions, and an interference in the cascade can lead to the failure of fusion of the facial primordia, resulting in facial clefting. An important transcription factor expressed primarily in the palatal shelves and tongue during palatogenesis is TBX22. TBX22 is a member of a family of transcriptional regulators containing a common DNA-binding domain, the T-box. Mutations of the TBX22 gene have been strongly linked with syndromic X linked cleft palate producing clefting of the palate and ankyloglossia, otherwise known as tongue-tie. <br />
<br />
Mutations of the TBX22 gene commonly occur as nucleotide alterations where amino acid substitutions, deletions and transitions may occur as well as sequence variants close to splice sites. These mutations lead to formation of truncated proteins, with missense mutations affecting amino acids within the DNA binding T box domain. Missense mutations of TBX22 primarily occur at major areas of contact with the target DNA, affecting and reducing the protein’s ability to bind to the DNA or even other binding proteins in the transcriptional complex. This loss in binding to DNA and other crucial proteins within the transcriptional complex therefore affects the downstream cascade of gene activation, and as a result the development and fusion of the palate. <br />
<br />
Through research it has been shown that a variety of genetic mutations involving genes such as TBX22, PVRL1, and IRF6 lead to facial clefting. However the location and type of mutation does not completely determine the severity of the clefting but rather environmental factors. Environmental factors such as alcohol, tobacco, and toxin exposure during pregnancy can also impact palatogenesis. <br />
<br />
1) <pubmed>14729838</pubmed><br />
2) <pubmed>14722155</pubmed><br />
<br />
<br />
==Lab 7 Assessment==<br />
1) What is/are the dystrophin mutation(s)?<br />
<br />
In approximately 65% of patients with Duchenne Muscular Dystrophy (DMD), lack of dystrophin is due to a frameshift mutation caused by gene deletions, which give rise to premature stop codons, hence preventing translation to protein. In the remaining cases, point mutations and small gene insertions/deletions are the underlying causes leading to formation of truncated protein, with exon duplications responsible for approximately 5% of all mutations.<br />
<br />
2) What is the function of dystrophin?<br />
<br />
DMD is caused by the absence of the protein dystrophin in skeletal, smooth and cardiac muscle, a protein present at the membrane of muscle fibres and an important link between the cytoplasmic and extracellular matrix of the muscle fibre. Due to this it has an important mechanical role where it maintains the strength of muscle fibres, as, in fibres lacking dystrophin, normal contraction weakens the fibre and leads to degeneration. As well as playing a mechanical role, it is also involved in signalling pathways such as pathways for production of nitric oxide, and the Ras/MPAK pathway.<br />
<br />
3) What other tissues/organs are affected by this disorder?<br />
<br />
Dystrophin is not only present in skeletal muscle, but also in cardiac muscle. The heart can be affected whereby the conduction tissues can get damaged and lead to abnormal rhythms such as arrthymia and dysrhythmia, or pump abnormally leading to cardiomyopathy. <br />
Weakening of respiratory muscles is additionally seen in patients, leading to difficulties in breathing. At this point ventilation machines are utilized to assist with breathing. <br />
<br />
4) What therapies exist for DMD?<br />
<br />
Over the years, patients with DMD have begun to live longer into their 20s and 30s showing an improvement in treatment. Various factors such as earlier and continuous use of corticosteroids, routine flu and pneumococcal injections, and intense physical therapy have influenced these results. Currently, the therapies available for DMD aim to manage the disease rather than cure it. Corticosteroids are given to the patient to improve muscle function and strength however with continued use into adulthood, side effects such as weight gain, hypertension, hyperglycemia, cataracts and osteoporosis begin to surface. Patients also undergo physiotherapy to maintain function of the limbs, particularly of the upper extremity. A daily stretch routine targeting the muscles of the forearm wrist and fingers is crucial so the patient can still control their wheelchair, for example. <br />
<br />
Research continues in the field of the disease and potential therapies have been proposed, in particular gene therapies. An example of a potential gene therapy for DMD patients is the CRISPR/Cas 9 system. This system is a genome modification technology, first identified in bacteria, re-engineered to 2 components of an RNA guide sequence and a DNA endonuclease. The system has now been modified to function in mammalian cells where it could generate random mutations or targeted repair, hence has been proposed as a potential way of disease modification.<br />
<br />
In order to correct the mutant phenotype of DMD the CRISPR/Cas9 system was recently employed on a mouse MdX model. It was found that the CRISPR/Cas 9 was able to repair a large population of skeletal myocytes, with the myocytes showing a good survival rate. Although the CRISPR/Cas 9 system has been successful in animal studies, further research must now be undertaken for employment in human patients.<br />
<br />
5) What animal models are available for muscular dystrophy?<br />
<br />
Currently, the most common animal model used for DMD research is the MDX mouse, which contains a nonsense mutation abolishing formation of dystrophin. However to bridge the gap between these models and human patients in terms of vector production and immune response, canine models are now being utilized. Dog breeds of the Golden Retriever, Rottweiler and Cavalier King Charles have been reported as dystrophin deficient due to gene deletions. <br />
<br />
References<br />
<br />
1) <pubmed>27515321</pubmed><br />
2) <pubmed>16887341</pubmed><br />
3) <pubmed>27619714 </pubmed></div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=248592
User:Z5018221
2016-09-22T10:38:55Z
<p>Z5018221: /* Lab 7 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 15:19, 2 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:21, 9 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:05, 16 September 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
<br />
<br />
== Lab 3 Assessment ==<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
<br />
[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
<br />
<br />
==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
<br />
{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
<br />
{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
<br />
{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
<br />
</quiz><br />
<br />
==Lab 5 Assessment==<br />
Questionnaire completed<br />
<br />
<br />
==Lab 6 Assessment==<br />
<br />
Cleft palate, often occurring in conjunction with cleft lip is among the most common congenital malformations and involves abnormal facial development during gestation. Between the 4th week and the 6th-7th weeks of development, migrating neural crest cells of the anterior neural tube with the mesodermal cells form the facial primordia. From here the filtrum and primary palate are formed, by the merging of the nasal prominences to form the intermaxillary segment, which then fuses with the maxillary prominences to form the upper lip. The palatal shelves additionally grow out from the maxillary prominences. <br />
<br />
This complex process involves a variety of signalling molecules, transcriptions factors and cell-cell interactions, and an interference in the cascade can lead to the failure of fusion of the facial primordia, resulting in facial clefting. An important transcription factor expressed primarily in the palatal shelves and tongue during palatogenesis is TBX22. TBX22 is a member of a family of transcriptional regulators containing a common DNA-binding domain, the T-box. Mutations of the TBX22 gene have been strongly linked with syndromic X linked cleft palate producing clefting of the palate and ankyloglossia, otherwise known as tongue-tie. <br />
<br />
Mutations of the TBX22 gene commonly occur as nucleotide alterations where amino acid substitutions, deletions and transitions may occur as well as sequence variants close to splice sites. These mutations lead to formation of truncated proteins, with missense mutations affecting amino acids within the DNA binding T box domain. Missense mutations of TBX22 primarily occur at major areas of contact with the target DNA, affecting and reducing the protein’s ability to bind to the DNA or even other binding proteins in the transcriptional complex. This loss in binding to DNA and other crucial proteins within the transcriptional complex therefore affects the downstream cascade of gene activation, and as a result the development and fusion of the palate. <br />
<br />
Through research it has been shown that a variety of genetic mutations involving genes such as TBX22, PVRL1, and IRF6 lead to facial clefting. However the location and type of mutation does not completely determine the severity of the clefting but rather environmental factors. Environmental factors such as alcohol, tobacco, and toxin exposure during pregnancy can also impact palatogenesis. <br />
<br />
1) <pubmed>14729838</pubmed><br />
2) <pubmed>14722155</pubmed><br />
<br />
<br />
==Lab 7 Assessment==<br />
1) What is/are the dystrophin mutation(s)?<br />
<br />
In approximately 65% of patients with Duchenne Muscular Dystrophy (DMD), lack of dystrophin is due to a frameshift mutation caused by gene deletions, which give rise to premature stop codons, hence preventing translation to protein. In the remaining cases, point mutations and small gene insertions/deletions are the underlying causes leading to formation of truncated protein, with exon duplications responsible for approximately 5% of all mutations.<br />
<br />
2) What is the function of dystrophin?<br />
<br />
DMD is caused by the absence of the protein dystrophin in skeletal, smooth and cardiac muscle, a protein present at the membrane of muscle fibres and an important link between the cytoplasmic and extracellular matrix of the muscle fibre. Due to this it has an important mechanical role where it maintains the strength of muscle fibres, as, in fibres lacking dystrophin, normal contraction weakens the fibre and leads to degeneration. As well as playing a mechanical role, it is also involved in signalling pathways such as pathways for production of nitric oxide, and the Ras/MPAK pathway.<br />
<br />
3) What other tissues/organs are affected by this disorder?<br />
<br />
Dystrophin is not only present in skeletal muscle, but also in cardiac muscle. The heart can be affected whereby the conduction tissues can get damaged and lead to abnormal rhythms such as arrthymia and dysrhythmia, or pump abnormally leading to cardiomyopathy. <br />
Weakening of respiratory muscles is additionally seen in patients, leading to difficulties in breathing. At this point ventilation machines are utilized to assist with breathing. <br />
<br />
4) What therapies exist for DMD?<br />
<br />
Over the years, patients with DMD have begun to live longer into their 20s and 30s showing an improvement in treatment. Various factors such as earlier and continuous use of corticosteroids, routine flu and pneumococcal injections, and intense physical therapy have influenced these results. Currently, the therapies available for DMD aim to manage the disease rather than cure it. Corticosteroids are given to the patient to improve muscle function and strength however with continued use into adulthood, side effects such as weight gain, hypertension, hyperglycemia, cataracts and osteoporosis begin to surface. Patients also undergo physiotherapy to maintain function of the limbs, particularly of the upper extremity. A daily stretch routine targeting the muscles of the forearm wrist and fingers is crucial so the patient can still control their wheelchair, for example. <br />
Research continues in the field of the disease and potential therapies have been proposed, in particular gene therapies. An example of a potential gene therapy for DMD patients is the CRISPR/Cas 9 system. This system is a genome modification technology, first identified in bacteria, re-engineered to 2 components of an RNA guide sequence and a DNA endonuclease. The system has now been modified to function in mammalian cells where it could generate random mutations or targeted repair, hence has been proposed as a potential way of disease modification.<br />
In order to correct the mutant phenotype of DMD the CRISPR/Cas9 system was recently employed on a mouse MdX model. It was found that the CRISPR/Cas 9 was able to repair a large population of skeletal myocytes, with the myocytes showing a good survival rate. Although the CRISPR/Cas 9 system has been successful in animal studies, further research must now be undertaken for employment in human patients.<br />
<br />
5) What animal models are available for muscular dystrophy?<br />
<br />
Currently, the most common animal model used for DMD research is the MDX mouse, which contains a nonsense mutation abolishing formation of dystrophin. However to bridge the gap between these models and human patients in terms of vector production and immune response, canine models are now being utilized. Dog breeds of the Golden Retriever, Rottweiler and Cavalier King Charles have been reported as dystrophin deficient due to gene deletions. <br />
<br />
References<br />
<br />
1) <pubmed>27515321</pubmed><br />
2) <pubmed>16887341</pubmed><br />
3) <pubmed>27619714 </pubmed></div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=248590
User:Z5018221
2016-09-22T10:37:41Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 15:19, 2 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:21, 9 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:05, 16 September 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
<br />
<br />
== Lab 3 Assessment ==<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
<br />
[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
<br />
<br />
==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
<br />
{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
<br />
{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
<br />
{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
<br />
</quiz><br />
<br />
==Lab 5 Assessment==<br />
Questionnaire completed<br />
<br />
<br />
==Lab 6 Assessment==<br />
<br />
Cleft palate, often occurring in conjunction with cleft lip is among the most common congenital malformations and involves abnormal facial development during gestation. Between the 4th week and the 6th-7th weeks of development, migrating neural crest cells of the anterior neural tube with the mesodermal cells form the facial primordia. From here the filtrum and primary palate are formed, by the merging of the nasal prominences to form the intermaxillary segment, which then fuses with the maxillary prominences to form the upper lip. The palatal shelves additionally grow out from the maxillary prominences. <br />
<br />
This complex process involves a variety of signalling molecules, transcriptions factors and cell-cell interactions, and an interference in the cascade can lead to the failure of fusion of the facial primordia, resulting in facial clefting. An important transcription factor expressed primarily in the palatal shelves and tongue during palatogenesis is TBX22. TBX22 is a member of a family of transcriptional regulators containing a common DNA-binding domain, the T-box. Mutations of the TBX22 gene have been strongly linked with syndromic X linked cleft palate producing clefting of the palate and ankyloglossia, otherwise known as tongue-tie. <br />
<br />
Mutations of the TBX22 gene commonly occur as nucleotide alterations where amino acid substitutions, deletions and transitions may occur as well as sequence variants close to splice sites. These mutations lead to formation of truncated proteins, with missense mutations affecting amino acids within the DNA binding T box domain. Missense mutations of TBX22 primarily occur at major areas of contact with the target DNA, affecting and reducing the protein’s ability to bind to the DNA or even other binding proteins in the transcriptional complex. This loss in binding to DNA and other crucial proteins within the transcriptional complex therefore affects the downstream cascade of gene activation, and as a result the development and fusion of the palate. <br />
<br />
Through research it has been shown that a variety of genetic mutations involving genes such as TBX22, PVRL1, and IRF6 lead to facial clefting. However the location and type of mutation does not completely determine the severity of the clefting but rather environmental factors. Environmental factors such as alcohol, tobacco, and toxin exposure during pregnancy can also impact palatogenesis. <br />
<br />
1) <pubmed>14729838</pubmed><br />
2) <pubmed>14722155</pubmed><br />
<br />
<br />
==Lab 7 Assessment==<br />
1) What is/are the dystrophin mutation(s)?<br />
In approximately 65% of patients with Duchenne Muscular Dystrophy (DMD), lack of dystrophin is due to a frameshift mutation caused by gene deletions, which give rise to premature stop codons, hence preventing translation to protein. In the remaining cases, point mutations and small gene insertions/deletions are the underlying causes leading to formation of truncated protein, with exon duplications responsible for approximately 5% of all mutations.<br />
<br />
2) What is the function of dystrophin?<br />
DMD is caused by the absence of the protein dystrophin in skeletal, smooth and cardiac muscle, a protein present at the membrane of muscle fibres and an important link between the cytoplasmic and extracellular matrix of the muscle fibre. Due to this it has an important mechanical role where it maintains the strength of muscle fibres, as, in fibres lacking dystrophin, normal contraction weakens the fibre and leads to degeneration. As well as playing a mechanical role, it is also involved in signalling pathways such as pathways for production of nitric oxide, and the Ras/MPAK pathway.<br />
<br />
3) What other tissues/organs are affected by this disorder?<br />
Dystrophin is not only present in skeletal muscle, but also in cardiac muscle. The heart can be affected whereby the conduction tissues can get damaged and lead to abnormal rhythms such as arrthymia and dysrhythmia, or pump abnormally leading to cardiomyopathy. <br />
Weakening of respiratory muscles is additionally seen in patients, leading to difficulties in breathing. At this point ventilation machines are utilized to assist with breathing. <br />
<br />
4) What therapies exist for DMD?<br />
Over the years, patients with DMD have begun to live longer into their 20s and 30s showing an improvement in treatment. Various factors such as earlier and continuous use of corticosteroids, routine flu and pneumococcal injections, and intense physical therapy have influenced these results. Currently, the therapies available for DMD aim to manage the disease rather than cure it. Corticosteroids are given to the patient to improve muscle function and strength however with continued use into adulthood, side effects such as weight gain, hypertension, hyperglycemia, cataracts and osteoporosis begin to surface. Patients also undergo physiotherapy to maintain function of the limbs, particularly of the upper extremity. A daily stretch routine targeting the muscles of the forearm wrist and fingers is crucial so the patient can still control their wheelchair, for example. <br />
Research continues in the field of the disease and potential therapies have been proposed, in particular gene therapies. An example of a potential gene therapy for DMD patients is the CRISPR/Cas 9 system. This system is a genome modification technology, first identified in bacteria, re-engineered to 2 components of an RNA guide sequence and a DNA endonuclease. The system has now been modified to function in mammalian cells where it could generate random mutations or targeted repair, hence has been proposed as a potential way of disease modification.<br />
In order to correct the mutant phenotype of DMD the CRISPR/Cas9 system was recently employed on a mouse MdX model. It was found that the CRISPR/Cas 9 was able to repair a large population of skeletal myocytes, with the myocytes showing a good survival rate. Although the CRISPR/Cas 9 system has been successful in animal studies, further research must now be undertaken for employment in human patients.<br />
<br />
5) What animal models are available for muscular dystrophy?<br />
Currently, the most common animal model used for DMD research is the MDX mouse, which contains a nonsense mutation abolishing formation of dystrophin. However to bridge the gap between these models and human patients in terms of vector production and immune response, canine models are now being utilized. Dog breeds of the Golden Retriever, Rottweiler and Cavalier King Charles have been reported as dystrophin deficient due to gene deletions. <br />
<br />
References<br />
1) <pubmed>27515321</pubmed><br />
2) <pubmed>16887341</pubmed><br />
3) <pubmed>27619714 </pubmed></div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=247784
User:Z5018221
2016-09-16T03:05:25Z
<p>Z5018221: /* Lab Attendance */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 15:19, 2 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:21, 9 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:05, 16 September 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
<br />
<br />
== Lab 3 Assessment ==<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
<br />
[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
<br />
<br />
==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
<br />
{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
<br />
{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
<br />
{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
<br />
</quiz><br />
<br />
==Lab 5 Assessment==<br />
Questionnaire completed<br />
<br />
<br />
==Lab 6 Assessment==<br />
<br />
Cleft palate, often occurring in conjunction with cleft lip is among the most common congenital malformations and involves abnormal facial development during gestation. Between the 4th week and the 6th-7th weeks of development, migrating neural crest cells of the anterior neural tube with the mesodermal cells form the facial primordia. From here the filtrum and primary palate are formed, by the merging of the nasal prominences to form the intermaxillary segment, which then fuses with the maxillary prominences to form the upper lip. The palatal shelves additionally grow out from the maxillary prominences. <br />
<br />
This complex process involves a variety of signalling molecules, transcriptions factors and cell-cell interactions, and an interference in the cascade can lead to the failure of fusion of the facial primordia, resulting in facial clefting. An important transcription factor expressed primarily in the palatal shelves and tongue during palatogenesis is TBX22. TBX22 is a member of a family of transcriptional regulators containing a common DNA-binding domain, the T-box. Mutations of the TBX22 gene have been strongly linked with syndromic X linked cleft palate producing clefting of the palate and ankyloglossia, otherwise known as tongue-tie. <br />
<br />
Mutations of the TBX22 gene commonly occur as nucleotide alterations where amino acid substitutions, deletions and transitions may occur as well as sequence variants close to splice sites. These mutations lead to formation of truncated proteins, with missense mutations affecting amino acids within the DNA binding T box domain. Missense mutations of TBX22 primarily occur at major areas of contact with the target DNA, affecting and reducing the protein’s ability to bind to the DNA or even other binding proteins in the transcriptional complex. This loss in binding to DNA and other crucial proteins within the transcriptional complex therefore affects the downstream cascade of gene activation, and as a result the development and fusion of the palate. <br />
<br />
Through research it has been shown that a variety of genetic mutations involving genes such as TBX22, PVRL1, and IRF6 lead to facial clefting. However the location and type of mutation does not completely determine the severity of the clefting but rather environmental factors. Environmental factors such as alcohol, tobacco, and toxin exposure during pregnancy can also impact palatogenesis. <br />
<br />
1) <pubmed>14729838</pubmed><br />
2) <pubmed>14722155</pubmed></div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=247532
User:Z5018221
2016-09-15T11:17:15Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 15:19, 2 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:21, 9 September 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
<br />
<br />
== Lab 3 Assessment ==<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
<br />
[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
<br />
<br />
==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
<br />
{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
<br />
{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
<br />
{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
<br />
</quiz><br />
<br />
==Lab 5 Assessment==<br />
Questionnaire completed<br />
<br />
<br />
==Lab 6 Assessment==<br />
<br />
Cleft palate, often occurring in conjunction with cleft lip is among the most common congenital malformations and involves abnormal facial development during gestation. Between the 4th week and the 6th-7th weeks of development, migrating neural crest cells of the anterior neural tube with the mesodermal cells form the facial primordia. From here the filtrum and primary palate are formed, by the merging of the nasal prominences to form the intermaxillary segment, which then fuses with the maxillary prominences to form the upper lip. The palatal shelves additionally grow out from the maxillary prominences. <br />
<br />
This complex process involves a variety of signalling molecules, transcriptions factors and cell-cell interactions, and an interference in the cascade can lead to the failure of fusion of the facial primordia, resulting in facial clefting. An important transcription factor expressed primarily in the palatal shelves and tongue during palatogenesis is TBX22. TBX22 is a member of a family of transcriptional regulators containing a common DNA-binding domain, the T-box. Mutations of the TBX22 gene have been strongly linked with syndromic X linked cleft palate producing clefting of the palate and ankyloglossia, otherwise known as tongue-tie. <br />
<br />
Mutations of the TBX22 gene commonly occur as nucleotide alterations where amino acid substitutions, deletions and transitions may occur as well as sequence variants close to splice sites. These mutations lead to formation of truncated proteins, with missense mutations affecting amino acids within the DNA binding T box domain. Missense mutations of TBX22 primarily occur at major areas of contact with the target DNA, affecting and reducing the protein’s ability to bind to the DNA or even other binding proteins in the transcriptional complex. This loss in binding to DNA and other crucial proteins within the transcriptional complex therefore affects the downstream cascade of gene activation, and as a result the development and fusion of the palate. <br />
<br />
Through research it has been shown that a variety of genetic mutations involving genes such as TBX22, PVRL1, and IRF6 lead to facial clefting. However the location and type of mutation does not completely determine the severity of the clefting but rather environmental factors. Environmental factors such as alcohol, tobacco, and toxin exposure during pregnancy can also impact palatogenesis. <br />
<br />
1) <pubmed>14729838</pubmed><br />
2) <pubmed>14722155</pubmed></div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=246804
User:Z5018221
2016-09-11T06:01:39Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 15:19, 2 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:21, 9 September 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
<br />
<br />
== Lab 3 Assessment ==<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
<br />
[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
<br />
<br />
==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
<br />
{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
<br />
{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
<br />
{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
<br />
</quiz><br />
<br />
==Lab 5 Assessment==<br />
Questionnaire completed</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=246672
User:Z5018221
2016-09-09T03:21:18Z
<p>Z5018221: /* Lab Attendance */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 15:19, 2 September 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 13:21, 9 September 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
<br />
<br />
== Lab 3 Assessment ==<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
<br />
[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
<br />
<br />
==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
<br />
{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
<br />
{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
<br />
{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
<br />
</quiz></div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=245746
User:Z5018221
2016-09-02T05:20:00Z
<p>Z5018221: /* Lab Attendance */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 15:19, 2 September 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
<br />
<br />
== Lab 3 Assessment ==<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
<br />
[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
<br />
<br />
==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
<br />
{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
<br />
{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
<br />
{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
<br />
</quiz></div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=245594
User:Z5018221
2016-09-02T00:40:56Z
<p>Z5018221: /* Lab 4 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
<br />
<br />
== Lab 3 Assessment ==<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
<br />
[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
<br />
<br />
==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===<br />
<quiz display=simple><br />
{During embryonic folding, a piece of the yolk sac pinches off to become the primitive gut. The yolk sac however, remains connected to the gut tube via the vitelline duct.<br />
|type="()"}<br />
+True<br />
-False<br />
|| This statement is true, the yolk sac remains connected via the vitelline duct, also known as the umbilical vesicle. The yolk sac provides nutrients and functions as the circulatory system for the early embryo.<br />
<br />
{Which is the correct sequence in liver development:<br />
|type="()"}<br />
-Hepatic diverticulum→ Ventral foregut endoderm→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
-Ventral foregut endoderm→ Hepatic buds→ Hepatocytes→ Hepatic diverticulum→ Gallbladder<br />
-Gallbladder→ Hepatocytes→ Hepatic buds→ Hepatic diverticulum→ Ventral foregut endoderm<br />
+Ventral foregut endoderm→ Hepatic diverticulum→ Gallbladder→ Hepatic buds→ Hepatocytes<br />
|| Correct, the liver of the embryo first originates from the ventral foregut endoderm, which then becomes the hepatic diverticulum, the first morphological sign of an embryonic liver. The anterior portion of the diverticulum gives rise to the liver, whereas the posterior portion then gives rise to the gallbladder. The hepatoblasts of the anterior portion invade the adjacent septum transversum mesenchyme, to form left and right hepatic buds. Through growth of the buds, hepatocytes are then formed.<br />
<br />
{All of the following function as a site of hematopoiesis during embryonic development EXCEPT:<br />
|type="()"}<br />
-Yolk Sac<br />
-Bone Marrow<br />
+Spleen<br />
-Liver<br />
|| The spleen during embryonic development functions as a major immune organ. It's hematopoietic function is lost in embryonic development , however maturation and proliferation of lymphoid precursor cells occur within the organ.<br />
<br />
{Which of the following is TRUE:<br />
|type="()"}<br />
+The cloaca forms the anterior urinary and dorsal rectal regions by formation of a septum within a common urinary, genital, GIT space<br />
-The foregut is supplied by the superior mesenteric artery<br />
-Abnormalities such as atresia and stenosis can lead to recanalization<br />
-Somatic and splanchnic mesoderm arise from intermediate mesoderm <br />
|| Correct, the cloaca membrane is found at lower end of the gastrointestinal tract which forms the urinary and rectal regions. The foregut is supplied by the celiac artery NOT the superior mesenteric artery, abnormalities of atresia and stenosis ARISE from complications in the process of recanalization, which is the process whereby the gut tube undergoes change from a hollow, to a solid and back to a hollow tube. Somatic and splanchnic mesoderm arise from the lateral plate mesoderm, NOT the intermediate mesoderm. <br />
<br />
</quiz></div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=245572
User:Z5018221
2016-09-02T00:04:33Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 29 August 2016 - All information Reference, Copyright and Student Image template correctly included with the file and referenced on your page here. Note though to display the reference citation correctly with the legend. You need to include the ref name for a citation, as shown below.<br />
<br />
Code: <nowiki><ref name="PMID18166081"><pubmed>18166081</pubmed></ref></nowiki><br />
<br />
Ago2 in Mammalian Gastrulation<ref name="PMID18166081"><pubmed>18166081</pubmed></ref><br />
| Assessment 5/5<br />
|}<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1<br />
<br />
<br />
== Lab 3 Assessment ==<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 31 August 2016 - Lab 3 Assessment Quiz - [[Lecture_-_Mesoderm_Development|Mesoderm]] and [[Lecture_-_Ectoderm_Development|Ectoderm]] development.<br />
<br />
[[Lecture_-_Mesoderm_Development#Somite_Formation|Question 1 - somites]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Primary_Vesicles|Question 3 - brain vesicles]]<br />
<br />
[[Lecture_-_Ectoderm_Development#Maternal_Diet|Question 5 - maternal diet]]<br />
| Assessment 3/5<br />
|}<br />
<br />
<br />
==Lab 4 Assessment==<br />
===Gastrointestinal Development in the Embryo===</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=244168
User:Z5018221
2016-08-26T04:13:37Z
<p>Z5018221: /* Lab Attendance */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:13, 26 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242541
User:Z5018221
2016-08-19T04:06:28Z
<p>Z5018221: /* Lab Attendance */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:06, 19 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242477
User:Z5018221
2016-08-19T03:16:21Z
<p>Z5018221: /* Lab Attendance */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]])<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242145
User:Z5018221
2016-08-18T12:20:49Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242143
User:Z5018221
2016-08-18T12:20:31Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242141
User:Z5018221
2016-08-18T12:20:10Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242139
User:Z5018221
2016-08-18T12:19:47Z
<p>Z5018221: /* Lab 2 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242137
User:Z5018221
2016-08-18T12:19:28Z
<p>Z5018221: /* Lab 2 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<pubmed>18166081</pubmed><br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242135
User:Z5018221
2016-08-18T12:18:16Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242133
User:Z5018221
2016-08-18T12:17:41Z
<p>Z5018221: /* Lab 2 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242131
User:Z5018221
2016-08-18T12:16:39Z
<p>Z5018221: /* Lab 2 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|thumb|Ago2 in Mammalian Gastrulation]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242123
User:Z5018221
2016-08-18T12:12:09Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|300px]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242121
User:Z5018221
2016-08-18T12:11:50Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|300px]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242117
User:Z5018221
2016-08-18T12:11:08Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|300px]]<br />
<br />
Ago2 and it's Importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
<br />
<br />
<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242115
User:Z5018221
2016-08-18T12:10:28Z
<p>Z5018221: /* Lab 2 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png|left|300px]]<br />
<br />
Ago2 and it's importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242113
User:Z5018221
2016-08-18T12:08:37Z
<p>Z5018221: /* Lab 2 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[File:Ago2 in Mammalian Gastrulation.png]]<br />
<br />
Ago2 and it's importance in FGF Signalling in Mammalian Gastrulation <br />
<br />
<pubmed>18166081</pubmed><br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242103
User:Z5018221
2016-08-18T12:03:36Z
<p>Z5018221: /* Lab 2 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[Ago2 in Mammalian Gastrulation.jpg]]<br />
<br />
<pubmed>18166081</pubmed><br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=242095
User:Z5018221
2016-08-18T12:01:29Z
<p>Z5018221: </p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
<br />
{| width=95%<br />
|-bgcolor="FAF5FF"<br />
| [mailto:m.hill@unsw.edu.au Mark Hill] 18 August 2016 - You have added the citation correctly and written a good descriptive summary of the article findings. I guess I am am wondering why the researchers expected human endometriotic fluid to have an effect on mice? Note the house mouse generally only lives about a year.<br />
| width=100px| Assessment 5/5<br />
|}<br />
<br />
<br />
==Lab 2 Assessment==<br />
[[Ago2 in Mammalian Gastrulation.png]]<br />
<br />
<pubmed>18166081</pubmed><br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=File:Ago2_in_Mammalian_Gastrulation.png&diff=242059
File:Ago2 in Mammalian Gastrulation.png
2016-08-18T11:47:12Z
<p>Z5018221: ==The Homozygous Disruption of Ago2 Results in a Disruption of FGF Signaling==
(A−F) Whole-mount in situ hybridization using an antisense probe against Fgf8, Eomesodermin, or Bmp4 on e7.5 wild-type (A, C, E) and Ago2–/– (B, D, F) embryo litterma...</p>
<hr />
<div>==The Homozygous Disruption of Ago2 Results in a Disruption of FGF Signaling==<br />
<br />
(A−F) Whole-mount in situ hybridization using an antisense probe against Fgf8, Eomesodermin, or Bmp4 on e7.5 wild-type (A, C, E) and Ago2–/– (B, D, F) embryo littermates. The Ago2–/– embryos exhibit a lateral expansion of Fgf8 and Eomesodermin expression away from the primitive streak (B, D; block-arrow). In contrast, the localization of Bmp4 expression is indistinguishable between wild-type (E) and Ago2–/– (F) embryo littermates.<br />
(A−D) Embryos imaged with reflective light.<br />
(E, F) Embryos imaged with reflective and transmitted light. The scale bar represents 200 μm.<br />
<br />
http://dx.doi.org/10.1371/journal.pgen.0030227.g004<br />
<br />
===Reference===<br />
<pubmed>18166081</pubmed><br />
<br />
===Copyright===<br />
© 2007 Alisch et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.<br />
<br />
{{Template:Student Image}}</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=240785
User:Z5018221
2016-08-12T04:41:37Z
<p>Z5018221: /* Lab Attendance */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:41, 12 August 2016 (AEST)<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=240453
User:Z5018221
2016-08-11T10:18:09Z
<p>Z5018221: /* Lab 1 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
During the process of oocyte retrieval, a technique used in in vitro fertilization (IVF), oocytes may become exposed to ovarian endometriotic fluid, an event that is unlikely however possible in the clinical environment. Hashin et al. investigated the effect of various concentrations of human endometriotic fluid exposure on mice cumulus-oocyte complexes (COCs) by measuring fertilization, blastocyst formation and hatched blastocyst rate. COCs obtained from 46-week-old female mice were randomly divided into 5 groups and each exposed to differing concentrations of endometriotic fluid obtained from a 29-year-old patient during aspiration, for 5 minutes. Final concentrations were 0.625%, 1.25%, 2.5% and 5%. COCs were then inseminated with sperm retrieved from male mice. Fertilisation was assessed day 1 following insemination by formation of 2-cell, and blastocyst formation on day 5. <br />
<br />
Results indicated no apparent difference between the endometriotic fluid treated groups and the non-exposed control group except for the 0.625% exposure group which had a higher fertilization rate. Blastocyst formation rate and hatched blastocyst rates were also similar between exposed and non-exposed groups, overall indicating no detrimental impact on fertilization, blastocyst formation, and hatched blastocyst rates, following exposure to differing concentrations of endometriotic fluid. Previous experiments have generated results proving otherwise such as an experiment by Piromlertamorn et al. using mice. It was shown that use of a single concentration of endometriotic fluid leads to similar results in fertilization and blastocyst formation rate, however a significant decrease in blastocyst hatching rate. Despite the result, the authors noted this decrease was also observed in serum-treated groups, providing conflicting results. Hashin et al. have additionally noted a few limitations to their experiment where the endometriotic fluid utilised was only from a single patient, and pregnancy and implantation rates were not analysed. The authors of the study stress that to truly assess the effect of endometriotic fluid on oocyte and embryonic development, the contents of the fluid should be studied further to determine cytoxic effect, and its effect on pregnancy and implantation.<br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221
https://embryology.med.unsw.edu.au/embryology/index.php?title=User:Z5018221&diff=240451
User:Z5018221
2016-08-11T10:02:23Z
<p>Z5018221: /* Lab 1 Assessment */</p>
<hr />
<div>{{ANAT2341Student2016}}<br />
<br />
<br />
==Lab Attendance==<br />
<br />
<br />
==Lab 1 Assessment==<br />
<br />
<pubmed>27462598</pubmed><br />
<br />
==Referencing==<br />
[http://www.ncbi.nlm.nih.gov/sites/entrez?db=pubmed&cmd=search&term=fertilization fertilization]<br />
<br />
[[User:Z5018221|Z5018221]] ([[User talk:Z5018221|talk]]) 14:34, 5 August 2016 (AEST)<br />
<br />
PMID 27486480<br />
<br />
http://molecularcytogenetics.biomedcentral.com/articles/10.1186/s13039-016-0269-1</div>
Z5018221