Blastocyst Development: Difference between revisions

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* facilitates transepithelial Na+ and fluid transport for blastocoel formation
* facilitates transepithelial Na+ and fluid transport for blastocoel formation
* transport is driven by Na, K-adenosine triphosphatase (ATPase) in basolateral membranes of the trophectoderm <ref><pubmed>16139691</pubmed></ref>
* transport is driven by Na, K-adenosine triphosphatase (ATPase) in basolateral membranes of the trophectoderm <ref><pubmed>16139691</pubmed></ref>
==Blastocyst Metabolism==
At this stage mammalian development metabolism switches on anaerobic glycolysis metabolism to satisfy metabolic demands of growing blastocyst and formation of the blastocoel. This is driven by facilitative glucose transporter (GLUT) protein expression, shown in a mouse study where GLUT8 is up-regulated following insulin stimulation.<ref><pubmed>10860996</pubmed>| [http://www.ncbi.nlm.nih.gov/pmc/articles/PMC16542 PMC16542] | [http://www.pnas.org/content/97/13/7313.full Proc Natl Acad Sci U S A.]</ref>
* aerobic - oxidation of lactate and pyruvate via the citric acid cycle (Krebs cycle) and oxidative phosphorylation
* glycolysis- converts glucose into pyruvate


==Molecular Factors==
==Molecular Factors==

Revision as of 10:33, 3 December 2010

Introduction

Human Blastocyst (day 5)[1]

(Greek, blastos = sprout + cystos = cavity) or blastula, the term used to describe the hollow cellular mass that forms in early development. The blastocyst consists of cells forming an outer trophoblast layer, an inner cell mass and a fluid-filled cavity. The blastocyst inner cell mass is the source of true embryonic stem cells capable of forming all cell types within the embryo. In humans, this stage occurs in the first and second weeks after the zygote forms a solid cellular mass morula stage) and before implantation.


Links: Fertilization | Week 1 | Morula | Blastocyst

Some Recent Findings

Blastocyst hatching from zona pellucida (mouse)
  • Non-invasive imaging of human embryos before embryonic genome activation predicts development to the blastocyst stage[2] "We report studies of preimplantation human embryo development that correlate time-lapse image analysis and gene expression profiling. By examining a large set of zygotes from in vitro fertilization (IVF), we find that success in progression to the blastocyst stage can be predicted with >93% sensitivity and specificity by measuring three dynamic, noninvasive imaging parameters by day 2 after fertilization, before embryonic genome activation (EGA)."
  • Blastocyst gene expression correlates with implantation potential[3] "Compared with blastocysts that resulted in healthy fetal development, blastocysts that failed to implant (negative) showed decreased B3gnt5 and Eomes gene expression, while blastocysts that resulted in spontaneous pregnancy loss (absorption) displayed decreased Wnt3a and Eomes gene expression."

Movies

Human-blastocyst-day-3-6-icon.jpg

Human Blastocyst Development (day 3-6)

Quicktime version | Flash version

Blastocyst Formation (in vitro)

The table below shows human blastocyst in vitro changes during week 1 development.[4] Human blastocyst formation-in vitro.jpg


Model Human Blastocyst Development

The following figure is from a recent study[2] using video and genetic analysis of in vitro human development during week 1 following fertilization.

Model human blastocyst development.jpg

  • EGA - embryonic genome activation
  • ESSP - embryonic stage–specific pattern, four unique embryonic stage–specific patterns (1-4)
Links: Figure with legend

Mouse Blastocyst Gene Expression

Mouse- preimplantation gene expression.jpg

General gene expression patterns are indicated from genomic profiling.[5]

  • red - loss of maternal mRNAs
  • green - activation of embryonic genome (EGA)
  • purple - maternal gene activation (MGA)
  • orange - continuous expression

Inner Cell Mass

This outer layer of cells is also called the "embryoblast", a cluster of cells located and attached on one wall of the outer trophoblast layer.

Trophoblast Layer

This outer layer of cells is also called the "trophectoderm" (TE) epithelium. A key function is for the transport of sodium (Na+) and chloride (Cl-) ions through this layer into the blastocoel.


Differentiation of this layer has been shown to be regulated by the transcription factors Tead4[6] and then Caudal-related homeobox 2 (Cdx2).


Links: Trophoblast | OMIM -Tead4 | OMIM - Cdx2

Blastocoel Formation

Mouse - blastocoel formation[7]
  • trophectoderm transports of Na+ and Cl- ions through this layer into the blastocoel
  • generates an osmotic gradient driving fluid across this epithelium
  • distinct apical and basolateral membrane domains specific for transport
  • facilitates transepithelial Na+ and fluid transport for blastocoel formation
  • transport is driven by Na, K-adenosine triphosphatase (ATPase) in basolateral membranes of the trophectoderm [8]

Blastocyst Metabolism

At this stage mammalian development metabolism switches on anaerobic glycolysis metabolism to satisfy metabolic demands of growing blastocyst and formation of the blastocoel. This is driven by facilitative glucose transporter (GLUT) protein expression, shown in a mouse study where GLUT8 is up-regulated following insulin stimulation.[9]

  • aerobic - oxidation of lactate and pyruvate via the citric acid cycle (Krebs cycle) and oxidative phosphorylation
  • glycolysis- converts glucose into pyruvate

Molecular Factors

  • TEA DNA- binding domain, these factors bind to the consensus TEA/ATTS cognate binding site[10]
    • TEF-3 - renamed Tead1 and Tead4
    • Tead3 - is expressed in the placental syncytiotrophoblasts
  • E-cadherin - Calcium ion-dependent cell adhesion molecule, a cell membrane adhesive protein required for morula compaction
  • epithin - A type II transmembrane serine protease, identified in mouse for compaction of the morula during preimplantation embryonic development. Expressed from 8-cell stage at blastomere contacts and co-localises in the morula with E-cadherin. PMID: 15848395
  • Na, K-adenosine triphosphatase - A sodium potassium pump that generates an osmotic gradient for fluid flow into the blastocoel
  • Zonula occludens-1 - (ZO-1) Tight junction protein involved in morula to blastocyst transformation in the mouse PMID: 18423437

Blastocyst in Other Species

Mouse Blastocyst

Bovine Blastocyst

References

  1. <pubmed>19924284</pubmed>| PMC2773928 | PLoS One
  2. 2.0 2.1 <pubmed>20890283</pubmed>| Nat Biotechnol.
  3. <pubmed>20864103</pubmed>
  4. <pubmed>10221713</pubmed>
  5. <pubmed>19043080</pubmed>| Mol Hum Reprod.
  6. <pubmed>18083014</pubmed>
  7. <pubmed>19043080</pubmed>| Mol Hum Reprod.
  8. <pubmed>16139691</pubmed>
  9. <pubmed>10860996</pubmed>| PMC16542 | Proc Natl Acad Sci U S A.
  10. <pubmed>8702974</pubmed>
  11. 11.0 11.1 11.2 11.3 11.4 <pubmed>21103067</pubmed>| PMC2980489 | PLoS One.


Reviews

<pubmed>20607796</pubmed> <pubmed>20364097</pubmed> <pubmed>17389140</pubmed>

Articles

<pubmed>20157423</pubmed> <pubmed>19289087</pubmed> <pubmed>18817772</pubmed> <pubmed>18083014</pubmed> <pubmed>16773657</pubmed>| Dev. Dyn.

Search PubMed

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Search Pubmed: blastocyst development | blastocoel development | inner cell mass development | trophectoderm |


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Cite this page: Hill, M.A. (2024, March 28) Embryology Blastocyst Development. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Blastocyst_Development

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G