Frog Development - Revision history

Z8600021 at 07:12, 7 December 2021

2021-12-07T07:12:20Z

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 * '''Pinhead antagonizes Admp to promote {{notochord}} formation'''{{#pmid:34142034|PMID34142034}} "Dorsoventral patterning of a vertebrate embryo critically depends on the activity of Smad1 that mediates signaling by BMP proteins, anti-dorsalizing morphogenetic protein (Admp), and their antagonists. Pinhead (Pnhd), a cystine-knot-containing secreted protein, is expressed in the ventrolateral {{mesoderm}} during Xenopus gastrulation; however, its molecular targets and signaling mechanisms have not been fully elucidated. Our mass spectrometry-based screen of the gastrula secretome identified Admp as Pnhd-associated protein. We show that Pnhd binds Admp and inhibits its ventralizing activity by reducing Smad1 phosphorylation and its transcriptional targets. Importantly, Pnhd depletion further increased phospho-Smad1 levels in the presence of Admp. Furthermore, Pnhd synergized with Chordin and a truncated {{BMP4}} receptor in the induction of notochord markers in {{ectoderm}} cells, and Pnhd-depleted embryos displayed notochord defects. Our findings suggest that Pnhd binds and inactivates Admp to promote notochord development. We propose that the interaction between Admp and Pnhd refines Smad1 activity gradients during vertebrate {{gastrulation}}."
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 * '''Endocrine disruption by environmental gestagens in amphibians - A short review supported by new in vitro data using gonads of Xenopus laevis'''{{#pmid:28431277|PMID28431277}} "Endocrine disruption caused by various anthropogenic compounds is of persisting concern, especially for aquatic wildlife, because surface waters are the main sink of these so-called endocrine disruptors (ED). In the past, research focused on (anti)estrogenic, (anti)androgenic, and (anti)thyroidal substances, affecting primarily reproduction and development in vertebrates; however, other endocrine systems might be also targeted by ED. Environmental gestagens, including natural progestogens (e.g. progesterone (P4)) and synthetic progestins used for contraception, are supposed to affect vertebrate reproduction via progesterone receptors. In the present paper, we review the current knowledge about gestagenic effects in amphibians, focussing on reproduction and the thyroid system. In addition, we support the literature data with results of recent in vitro experiments, demonstrating direct impacts of the gestagens levonorgestrel (LNG) and P4 on sexually differentiated gonads of larval Xenopus laevis. The results showed a higher susceptibility of female over male gonads to gestagenic ED. Only in female gonads LNG, but not P4, had direct inhibitory effects on gene expression of steroidogenic acute regulatory protein and P450 side chain cleavage enzyme, whereas aromatase expression decreased in reaction to both gestagens. Surprisingly, beyond the expected ED effects of gestagens on reproductive physiology in amphibians, LNG drastically disrupted the thyroid system, which resembles direct effects on thyroid glands and pituitary along the pituitary-thyroid axis disturbing metamorphic development. In amphibians, environmental gestagens not only affect the reproductive system but at least LNG can impact also development by disruption of the thyroid system." [[Endocrine - Gonad Development|Gonad Development]] | [[Endocrine - Thyroid Development|Thyroid Development]]

Z8600021 at 07:10, 7 December 2021

2021-12-07T07:10:11Z

← Older revision		Revision as of 18:10, 7 December 2021
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			* '''Pinhead antagonizes Admp to promote {{notochord}} formation'''{{#pmid:34142034\|PMID34142034}} "Dorsoventral patterning of a vertebrate embryo critically depends on the activity of Smad1 that mediates signaling by BMP proteins, anti-dorsalizing morphogenetic protein (Admp), and their antagonists. Pinhead (Pnhd), a cystine-knot-containing secreted protein, is expressed in the ventrolateral {{mesoderm}} during Xenopus gastrulation; however, its molecular targets and signaling mechanisms have not been fully elucidated. Our mass spectrometry-based screen of the gastrula secretome identified Admp as Pnhd-associated protein. We show that Pnhd binds Admp and inhibits its ventralizing activity by reducing Smad1 phosphorylation and its transcriptional targets. Importantly, Pnhd depletion further increased phospho-Smad1 levels in the presence of Admp. Furthermore, Pnhd synergized with Chordin and a truncated {{BMP4}} receptor in the induction of notochord markers in {{ectoderm}} cells, and Pnhd-depleted embryos displayed notochord defects. Our findings suggest that Pnhd binds and inactivates Admp to promote notochord development. We propose that the interaction between Admp and Pnhd refines Smad1 activity gradients during vertebrate {{gastrulation}}."

	* '''Anosmin-1 is essential for neural crest and cranial placodes formation in Xenopus'''{{#pmid:29277616\|PMID29277616}} "During embryogenesis vertebrates develop a complex craniofacial skeleton associated with sensory organs. These structures are primarily derived from two embryonic cell populations the neural crest and cranial placodes, respectively. ...Anos1 was identified as a target of Pax3 and Zic1, two transcription factors necessary and sufficient to generate neural crest and cranial placodes. Anos1 is expressed in cranial neural crest progenitors at early neurula stage and in cranial placode derivatives later in development. We show that Anos1 function is required for neural crest and sensory organs development in Xenopus, consistent with the defects observed in Kallmann syndrome patients carrying a mutation in ANOS1."		* '''Anosmin-1 is essential for neural crest and cranial placodes formation in Xenopus'''{{#pmid:29277616\|PMID29277616}} "During embryogenesis vertebrates develop a complex craniofacial skeleton associated with sensory organs. These structures are primarily derived from two embryonic cell populations the neural crest and cranial placodes, respectively. ...Anos1 was identified as a target of Pax3 and Zic1, two transcription factors necessary and sufficient to generate neural crest and cranial placodes. Anos1 is expressed in cranial neural crest progenitors at early neurula stage and in cranial placode derivatives later in development. We show that Anos1 function is required for neural crest and sensory organs development in Xenopus, consistent with the defects observed in Kallmann syndrome patients carrying a mutation in ANOS1."

Z8600021 at 00:02, 16 April 2019

2019-04-16T00:02:18Z

← Older revision		Revision as of 11:02, 16 April 2019
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	{{#pmid:17606898}}		{{#pmid:17606898}}


			===Articles===

			{{#pmid:21013391}}

	===Search Pubmed===		===Search Pubmed===

Z8600021 at 01:05, 17 April 2018

2018-04-17T01:05:15Z

← Older revision		Revision as of 12:05, 17 April 2018
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	* '''118 hours''' - early heart beat, development of gill buds		* '''118 hours''' - early heart beat, development of gill buds
	* '''140 hours''' - hatching and gill circulation		* '''140 hours''' - hatching and gill circulation
	* '''162 hours''' - mouth opens and cornea becomes transparent		* '''162 hours''' - mouth opens and {{cornea}} becomes transparent
	* '''192 hours''' - tail fin circulation established		* '''192 hours''' - tail fin circulation established
	* '''216 hours''' - degeneration of external gills, formation of operculum, development of embryonic teeth		* '''216 hours''' - degeneration of external gills, formation of operculum, development of embryonic teeth
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	==Cornea==		==Cornea==
	[[File:Xenopus_cornea_development_timeline.jpg\|thumb\|400px\|alt=Xenopus cornea development timeline\|Xenopus cornea development timeline\|{{#pmid:23896054\|PMID23896054}}]]		[[File:Xenopus_cornea_development_timeline.jpg\|thumb\|400px\|alt=Xenopus cornea development timeline\|Xenopus cornea development timeline\|{{#pmid:23896054\|PMID23896054}}]]
	~~This developmental timeline is from a recent Xenopus laevis cornea study{{#pmid:23896054\|PMID23896054}}~~

	{{Frog Cornea Timeline table}}		{{Frog Cornea Timeline table}}
	* '''stage 25''' - cornea starts from a simple embryonic epidermis overlying the developing optic vesicle.
	* '''stage 30''' - detachment of the lens placode, cranial neural crest cells start to invade the space between the lens and the embryonic epidermis to construct the corneal endothelium.
	* '''stage 41''' - a second wave of migratory cells containing presumptive keratocytes invades the matrix leading to the formation of inner cornea and outer cornea. A unique cell mass (stroma attracting center) connects the two layers like the center pole of a tent.
	* '''stage 48''' - many secondary stromal keratocytes individually migrate to the center and form the stroma layer.
	* '''stage 60''' - the stroma space is filled by collagen lamellae and keratocytes, and the stroma attracting center disappears. At early metamorphosis, the embryonic epithelium gradually changes to the adult corneal epithelium, which is covered by microvilli.
	* '''stage 62''' - the embryonic epithelium thickens and cell death is observed in the epithelium, coinciding with eyelid opening.
	* '''After metamorphosis''' - cornea has attained the adult structure of three cellular layers, epithelium, stroma, and endothelium, and between the cellular layers lie two acellular layers (Bowman's layer and Descemet's membrane)

Z8600021 at 00:36, 17 April 2018

2018-04-17T00:36:17Z

← Older revision		Revision as of 11:36, 17 April 2018
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	[[File:Adult frogs 01.jpg\|thumb\|250px\|Adult Frogs]]		[[File:Adult frogs 01.jpg\|thumb\|250px\|Adult Frogs]]
	[[File:Hans Spemann.jpg\|thumb\|[[Embryology History - Hans Spemann\|Hans Spemann]] discoverer of the organiser region (primitive node) for gastrulation.]]		[[File:Hans Spemann.jpg\|thumb\|[[Embryology History - Hans Spemann\|Hans Spemann]] discoverer of the organiser region (primitive node) for gastrulation.]]
	The frog has been historically been used as an amphibian animal model of development due to the ease of observation from the fertilized egg through to tadpole stage. The later metamorphosis of the tadpole to frog has also been studied for hormonal controls and limb development. There have also been many different species used in these developmental studies.		The {{frog}} has been historically been used as an amphibian animal model of development due to the ease of observation from the fertilized egg through to tadpole stage. The later metamorphosis of the tadpole to frog has also been studied for hormonal controls and limb development. There have also been many different species used in these developmental studies.


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	The African clawed frog (''Xenopus laevis'') has been used in many embryological and electrophysiological studies as well as the basis of a historic ~~[[Pregnancy Test\|~~pregnancy test]]. The advantages of this frog is the fertility cycle can be easliy controlled and the eggs develop entirely independently and easily visible to the investigator. You can see an overview of the [[Frog_Development#Frog_Life_Cycle\|frog life cycle]] with links to specific stages as well as movies of the early process of gastrulation. This animal model has also shown that localization of maternal messenger RNA (eg vegetal and review) appears to play a key role in the development of early embryological patterns.		The African clawed frog (''Xenopus laevis'') has been used in many embryological and electrophysiological studies as well as the basis of a historic {{pregnancy test}}. The advantages of this frog is the fertility cycle can be easliy controlled and the eggs develop entirely independently and easily visible to the investigator. You can see an overview of the [[Frog_Development#Frog_Life_Cycle\|frog life cycle]] with links to specific stages as well as movies of the early process of gastrulation. This animal model has also shown that localization of maternal messenger RNA (eg vegetal and review) appears to play a key role in the development of early embryological patterns.


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	This developmental timeline is from a recent Xenopus laevis cornea study{{#pmid:23896054\|PMID23896054}}		This developmental timeline is from a recent Xenopus laevis cornea study{{#pmid:23896054\|PMID23896054}}

			{{Frog Cornea Timeline table}}
	* '''stage 25''' - cornea starts from a simple embryonic epidermis overlying the developing optic vesicle.		* '''stage 25''' - cornea starts from a simple embryonic epidermis overlying the developing optic vesicle.
	* '''stage 30''' - detachment of the lens placode, cranial neural crest cells start to invade the space between the lens and the embryonic epidermis to construct the corneal endothelium.		* '''stage 30''' - detachment of the lens placode, cranial neural crest cells start to invade the space between the lens and the embryonic epidermis to construct the corneal endothelium.

Z8600021 at 21:15, 12 March 2018

2018-03-12T21:15:32Z

← Older revision		Revision as of 08:15, 13 March 2018
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	* '''Anosmin-1 is essential for neural crest and cranial placodes formation in Xenopus'''{{#pmid:29277616\|PMID29277616}} "During embryogenesis vertebrates develop a complex craniofacial skeleton associated with sensory organs. These structures are primarily derived from two embryonic cell populations the neural crest and cranial placodes, respectively. ...Anos1 was identified as a target of Pax3 and Zic1, two transcription factors necessary and sufficient to generate neural crest and cranial placodes. Anos1 is expressed in cranial neural crest progenitors at early neurula stage and in cranial placode derivatives later in development. We show that Anos1 function is required for neural crest and sensory organs development in Xenopus, consistent with the defects observed in Kallmann syndrome patients carrying a mutation in ANOS1."		* '''Anosmin-1 is essential for neural crest and cranial placodes formation in Xenopus'''{{#pmid:29277616\|PMID29277616}} "During embryogenesis vertebrates develop a complex craniofacial skeleton associated with sensory organs. These structures are primarily derived from two embryonic cell populations the neural crest and cranial placodes, respectively. ...Anos1 was identified as a target of Pax3 and Zic1, two transcription factors necessary and sufficient to generate neural crest and cranial placodes. Anos1 is expressed in cranial neural crest progenitors at early neurula stage and in cranial placode derivatives later in development. We show that Anos1 function is required for neural crest and sensory organs development in Xenopus, consistent with the defects observed in Kallmann syndrome patients carrying a mutation in ANOS1."

			* '''EphA7 regulates claudin6 and pronephros development in Xenopus'''{{#pmid:29223398\|PMID29223398}} "Here we studied the roles of the Eph receptor EphA7 and its soluble form in Xenopus pronephros development. EphA7 is specifically expressed in pronephric tubules at tadpole stages and knockdown of EphA7 by a translation blocking morpholino led to defects in tubule cell differentiation and morphogenesis. A soluble form of EphA7 (sEphA7) was also identified. ...Our work suggests a role of EphA7 in the regulation of cell adhesion during pronephros development, whereas sEphA7 works as an antagonist."

	* '''N1-Src kinase is required for primary neurogenesis in Xenopus tropicalis'''{{#pmid:28765332\|PMID28765332}} "The presence of the neuronal-specific N1-Src splice variant of the C-Src tyrosine kinase is conserved through vertebrate evolution, suggesting an important role in complex nervous systems. The Src family of non-receptor tyrosine kinases act in signalling pathways that regulate cell migration, cell adhesion and proliferation. Srcs are also enriched in the brain where they play key roles in neuronal development and neurotransmission. Vertebrates have evolved a neuron-specific splice variant of C-Src, N1-Src, which differs from C-Src by just five or six amino acids. N1-Src is poorly understood and its high similarity to C-Src has made it difficult to delineate its function. Using antisense knockdown of the n1-src microexon, we have studied neuronal development in the Xenopus embryo in the absence of n1-src, whilst preserving c-src Loss of n1-src causes a striking absence of primary neurogenesis, implicating n1-src in the specification of neurons early in neural development." [[Neural System Development]]		* '''N1-Src kinase is required for primary neurogenesis in Xenopus tropicalis'''{{#pmid:28765332\|PMID28765332}} "The presence of the neuronal-specific N1-Src splice variant of the C-Src tyrosine kinase is conserved through vertebrate evolution, suggesting an important role in complex nervous systems. The Src family of non-receptor tyrosine kinases act in signalling pathways that regulate cell migration, cell adhesion and proliferation. Srcs are also enriched in the brain where they play key roles in neuronal development and neurotransmission. Vertebrates have evolved a neuron-specific splice variant of C-Src, N1-Src, which differs from C-Src by just five or six amino acids. N1-Src is poorly understood and its high similarity to C-Src has made it difficult to delineate its function. Using antisense knockdown of the n1-src microexon, we have studied neuronal development in the Xenopus embryo in the absence of n1-src, whilst preserving c-src Loss of n1-src causes a striking absence of primary neurogenesis, implicating n1-src in the specification of neurons early in neural development." [[Neural System Development]]

Z8600021 at 21:13, 12 March 2018

2018-03-12T21:13:30Z

← Older revision		Revision as of 08:13, 13 March 2018
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			* '''Anosmin-1 is essential for neural crest and cranial placodes formation in Xenopus'''{{#pmid:29277616\|PMID29277616}} "During embryogenesis vertebrates develop a complex craniofacial skeleton associated with sensory organs. These structures are primarily derived from two embryonic cell populations the neural crest and cranial placodes, respectively. ...Anos1 was identified as a target of Pax3 and Zic1, two transcription factors necessary and sufficient to generate neural crest and cranial placodes. Anos1 is expressed in cranial neural crest progenitors at early neurula stage and in cranial placode derivatives later in development. We show that Anos1 function is required for neural crest and sensory organs development in Xenopus, consistent with the defects observed in Kallmann syndrome patients carrying a mutation in ANOS1."

	* '''N1-Src kinase is required for primary neurogenesis in Xenopus tropicalis'''{{#pmid:28765332\|PMID28765332}} "The presence of the neuronal-specific N1-Src splice variant of the C-Src tyrosine kinase is conserved through vertebrate evolution, suggesting an important role in complex nervous systems. The Src family of non-receptor tyrosine kinases act in signalling pathways that regulate cell migration, cell adhesion and proliferation. Srcs are also enriched in the brain where they play key roles in neuronal development and neurotransmission. Vertebrates have evolved a neuron-specific splice variant of C-Src, N1-Src, which differs from C-Src by just five or six amino acids. N1-Src is poorly understood and its high similarity to C-Src has made it difficult to delineate its function. Using antisense knockdown of the n1-src microexon, we have studied neuronal development in the Xenopus embryo in the absence of n1-src, whilst preserving c-src Loss of n1-src causes a striking absence of primary neurogenesis, implicating n1-src in the specification of neurons early in neural development." [[Neural System Development]]		* '''N1-Src kinase is required for primary neurogenesis in Xenopus tropicalis'''{{#pmid:28765332\|PMID28765332}} "The presence of the neuronal-specific N1-Src splice variant of the C-Src tyrosine kinase is conserved through vertebrate evolution, suggesting an important role in complex nervous systems. The Src family of non-receptor tyrosine kinases act in signalling pathways that regulate cell migration, cell adhesion and proliferation. Srcs are also enriched in the brain where they play key roles in neuronal development and neurotransmission. Vertebrates have evolved a neuron-specific splice variant of C-Src, N1-Src, which differs from C-Src by just five or six amino acids. N1-Src is poorly understood and its high similarity to C-Src has made it difficult to delineate its function. Using antisense knockdown of the n1-src microexon, we have studied neuronal development in the Xenopus embryo in the absence of n1-src, whilst preserving c-src Loss of n1-src causes a striking absence of primary neurogenesis, implicating n1-src in the specification of neurons early in neural development." [[Neural System Development]]

Z8600021 at 21:08, 12 March 2018

2018-03-12T21:08:54Z

@@ Line 30: / Line 30: @@
 * '''N1-Src kinase is required for primary neurogenesis in Xenopus tropicalis'''{{#pmid:28765332|PMID28765332}} "The presence of the neuronal-specific N1-Src splice variant of the C-Src tyrosine kinase is conserved through vertebrate evolution, suggesting an important role in complex nervous systems. The Src family of non-receptor tyrosine kinases act in signalling pathways that regulate cell migration, cell adhesion and proliferation. Srcs are also enriched in the brain where they play key roles in neuronal development and neurotransmission. Vertebrates have evolved a neuron-specific splice variant of C-Src, N1-Src, which differs from C-Src by just five or six amino acids. N1-Src is poorly understood and its high similarity to C-Src has made it difficult to delineate its function. Using antisense knockdown of the n1-src microexon, we have studied neuronal development in the Xenopus embryo in the absence of n1-src, whilst preserving c-src Loss of n1-src causes a striking absence of primary neurogenesis, implicating n1-src in the specification of neurons early in neural development." [[Neural System Development]]
 * '''Endocrine disruption by environmental gestagens in amphibians - A short review supported by new in vitro data using gonads of Xenopus laevis'''{{#pmid:28431277|PMID28431277}} "Endocrine disruption caused by various anthropogenic compounds is of persisting concern, especially for aquatic wildlife, because surface waters are the main sink of these so-called endocrine disruptors (ED). In the past, research focused on (anti)estrogenic, (anti)androgenic, and (anti)thyroidal substances, affecting primarily reproduction and development in vertebrates; however, other endocrine systems might be also targeted by ED. Environmental gestagens, including natural progestogens (e.g. progesterone (P4)) and synthetic progestins used for contraception, are supposed to affect vertebrate reproduction via progesterone receptors. In the present paper, we review the current knowledge about gestagenic effects in amphibians, focussing on reproduction and the thyroid system. In addition, we support the literature data with results of recent in vitro experiments, demonstrating direct impacts of the gestagens levonorgestrel (LNG) and P4 on sexually differentiated gonads of larval Xenopus laevis. The results showed a higher susceptibility of female over male gonads to gestagenic ED. Only in female gonads LNG, but not P4, had direct inhibitory effects on gene expression of steroidogenic acute regulatory protein and P450 side chain cleavage enzyme, whereas aromatase expression decreased in reaction to both gestagens. Surprisingly, beyond the expected ED effects of gestagens on reproductive physiology in amphibians, LNG drastically disrupted the thyroid system, which resembles direct effects on thyroid glands and pituitary along the pituitary-thyroid axis disturbing metamorphic development. In amphibians, environmental gestagens not only affect the reproductive system but at least LNG can impact also development by disruption of the thyroid system." [[Endocrine - Gonad Development|Gonad Development]] | [[Endocrine - Thyroid Development|Thyroid Development]]
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 * '''Repression of zygotic gene expression in the Xenopus germline.'''{{#pmid:20110330|PMID20110330}} "Primordial germ cells (PGCs) in Xenopus are specified through the inheritance of germ plasm. During gastrulation, PGCs remain totipotent while surrounding cells in the vegetal mass become committed to endoderm through the action of the vegetal localized maternal transcription factor VegT. We find that although PGCs contain maternal VegT RNA, they do not express its downstream targets at the mid-blastula transition (MBT)."
 |}
 ==Taxon==

Z8600021 at 21:06, 12 March 2018

2018-03-12T21:06:33Z

Show changes

Z8600021 at 05:20, 12 August 2017

2017-08-12T05:20:44Z

← Older revision		Revision as of 16:20, 12 August 2017
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			* '''N1-Src kinase is required for primary neurogenesis in Xenopus tropicalis'''<ref name=PMID28765332><pubmed>28765332</pubmed></ref> "The presence of the neuronal-specific N1-Src splice variant of the C-Src tyrosine kinase is conserved through vertebrate evolution, suggesting an important role in complex nervous systems. The Src family of non-receptor tyrosine kinases act in signalling pathways that regulate cell migration, cell adhesion and proliferation. Srcs are also enriched in the brain where they play key roles in neuronal development and neurotransmission. Vertebrates have evolved a neuron-specific splice variant of C-Src, N1-Src, which differs from C-Src by just five or six amino acids. N1-Src is poorly understood and its high similarity to C-Src has made it difficult to delineate its function. Using antisense knockdown of the n1-src microexon, we have studied neuronal development in the Xenopus embryo in the absence of n1-src, whilst preserving c-src Loss of n1-src causes a striking absence of primary neurogenesis, implicating n1-src in the specification of neurons early in neural development." [[Neural System Development]]

	\|
	* '''Endocrine disruption by environmental gestagens in amphibians - A short review supported by new in vitro data using gonads of Xenopus laevis'''<ref name=PMID28431277><pubmed>28431277</pubmed></ref> "Endocrine disruption caused by various anthropogenic compounds is of persisting concern, especially for aquatic wildlife, because surface waters are the main sink of these so-called endocrine disruptors (ED). In the past, research focused on (anti)estrogenic, (anti)androgenic, and (anti)thyroidal substances, affecting primarily reproduction and development in vertebrates; however, other endocrine systems might be also targeted by ED. Environmental gestagens, including natural progestogens (e.g. progesterone (P4)) and synthetic progestins used for contraception, are supposed to affect vertebrate reproduction via progesterone receptors. In the present paper, we review the current knowledge about gestagenic effects in amphibians, focussing on reproduction and the thyroid system. In addition, we support the literature data with results of recent in vitro experiments, demonstrating direct impacts of the gestagens levonorgestrel (LNG) and P4 on sexually differentiated gonads of larval Xenopus laevis. The results showed a higher susceptibility of female over male gonads to gestagenic ED. Only in female gonads LNG, but not P4, had direct inhibitory effects on gene expression of steroidogenic acute regulatory protein and P450 side chain cleavage enzyme, whereas aromatase expression decreased in reaction to both gestagens. Surprisingly, beyond the expected ED effects of gestagens on reproductive physiology in amphibians, LNG drastically disrupted the thyroid system, which resembles direct effects on thyroid glands and pituitary along the pituitary-thyroid axis disturbing metamorphic development. In amphibians, environmental gestagens not only affect the reproductive system but at least LNG can impact also development by disruption of the thyroid system." [[Endocrine - Gonad Development\|Gonad Development]] \| [[Endocrine - Thyroid Development\|Thyroid Development]]		* '''Endocrine disruption by environmental gestagens in amphibians - A short review supported by new in vitro data using gonads of Xenopus laevis'''<ref name=PMID28431277><pubmed>28431277</pubmed></ref> "Endocrine disruption caused by various anthropogenic compounds is of persisting concern, especially for aquatic wildlife, because surface waters are the main sink of these so-called endocrine disruptors (ED). In the past, research focused on (anti)estrogenic, (anti)androgenic, and (anti)thyroidal substances, affecting primarily reproduction and development in vertebrates; however, other endocrine systems might be also targeted by ED. Environmental gestagens, including natural progestogens (e.g. progesterone (P4)) and synthetic progestins used for contraception, are supposed to affect vertebrate reproduction via progesterone receptors. In the present paper, we review the current knowledge about gestagenic effects in amphibians, focussing on reproduction and the thyroid system. In addition, we support the literature data with results of recent in vitro experiments, demonstrating direct impacts of the gestagens levonorgestrel (LNG) and P4 on sexually differentiated gonads of larval Xenopus laevis. The results showed a higher susceptibility of female over male gonads to gestagenic ED. Only in female gonads LNG, but not P4, had direct inhibitory effects on gene expression of steroidogenic acute regulatory protein and P450 side chain cleavage enzyme, whereas aromatase expression decreased in reaction to both gestagens. Surprisingly, beyond the expected ED effects of gestagens on reproductive physiology in amphibians, LNG drastically disrupted the thyroid system, which resembles direct effects on thyroid glands and pituitary along the pituitary-thyroid axis disturbing metamorphic development. In amphibians, environmental gestagens not only affect the reproductive system but at least LNG can impact also development by disruption of the thyroid system." [[Endocrine - Gonad Development\|Gonad Development]] \| [[Endocrine - Thyroid Development\|Thyroid Development]]