Axolotl Development - Revision history

Z8600021 at 05:51, 26 February 2022

2022-02-26T05:51:05Z

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			* '''Neural control of growth and size in the axolotl limb regenerate'''{{#pmid:34779399\|PMID34779399}} "Upon the completion of the developmental stages of regeneration, when the regenerative organ known as the blastema completes patterning and differentiation, the limb regenerate is proportionally small in size. It then undergoes a phase of regeneration that we have called the 'tiny-limb' stage, which is defined by rapid growth until the regenerate reaches the proportionally appropriate size. In the current study we have characterized this growth and have found that signaling from the limb nerves is required for its maintenance. Using the regenerative assay known as the accessory limb model (ALM), we have found that growth and size of the limb positively correlates with nerve abundance. We have additionally developed a new regenerative assay called the neural modified-ALM (NM-ALM), which decouples the source of the nerves from the regenerating host environment. Using the NM-ALM we discovered that non-neural extrinsic factors from differently sized host animals do not play a prominent role in determining the size of the regenerating limb. We have also discovered that the regulation of limb size is not autonomously regulated by the limb nerves. Together, these observations show that the limb nerves provide essential cues to regulate ontogenetic allometric growth and the final size of the regenerating limb."

	* '''BMP signaling is essential for sustaining proximo-distal progression in regenerating axolotl limbs'''{{#pmid:32665245\|PMID32665245}} "Amputation of a salamander {{limb}} triggers a regeneration process that is perfect. A limited number of genes have been studied in this context and even fewer have been analyzed functionally. In this work, we use the {{BMP}} signaling inhibitor LDN193189 on Ambystoma mexicanum to explore the role of BMPs in regeneration. We find that BMP signaling is required for proper expression of various patterning genes and that its inhibition causes major defects in the regenerated limbs. {{Fgf}}8 is down-regulated when BMP signaling is blocked, but ectopic injection of either human or axolotl protein did not rescue the defects. By administering LDN193189 treatments at different time points during regeneration, we show clearly that limb regeneration progresses in a proximal to distal fashion. This demonstrates that BMPs play a major role in patterning of regenerated limbs and that regeneration is a progressive process like development."		* '''BMP signaling is essential for sustaining proximo-distal progression in regenerating axolotl limbs'''{{#pmid:32665245\|PMID32665245}} "Amputation of a salamander {{limb}} triggers a regeneration process that is perfect. A limited number of genes have been studied in this context and even fewer have been analyzed functionally. In this work, we use the {{BMP}} signaling inhibitor LDN193189 on Ambystoma mexicanum to explore the role of BMPs in regeneration. We find that BMP signaling is required for proper expression of various patterning genes and that its inhibition causes major defects in the regenerated limbs. {{Fgf}}8 is down-regulated when BMP signaling is blocked, but ectopic injection of either human or axolotl protein did not rescue the defects. By administering LDN193189 treatments at different time points during regeneration, we show clearly that limb regeneration progresses in a proximal to distal fashion. This demonstrates that BMPs play a major role in patterning of regenerated limbs and that regeneration is a progressive process like development."
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	* '''Rediscovering the Axolotl as a Model for {{Thyroid}} Hormone Dependent Development'''{{#pmid:31031711\|PMID31031711}} "The Mexican axolotl (Ambystoma mexicanum) is an important model organism in biomedical research. Much current attention is focused on the axolotl's amazing ability to regenerate tissues and whole organs after injury. However, not forgotten is the axolotl's equally amazing ability to thwart aspects of tissue maturation and retain juvenile morphology into the adult phase of life. Unlike close tiger salamander relatives that undergo a thyroid hormone regulated metamorphosis, the axolotl does not typically undergo a metamorphosis. Instead, the axolotl exhibits a paedomorphic mode of development that enables a completely aquatic life cycle. The evolution of paedomorphosis allowed axolotls to exploit relatively permanent habitats in Mexico, and preadapted axolotls for domestication and laboratory study. In this perspective, we first introduce the axolotl and the various meanings of paedomorphosis, and then stress the need to move beyond endocrinology-guided approaches to understand the axolotl's hypothyroid state. With the recent completion of the axolotl genome assembly and established methods to manipulate gene functions, the axolotl is poised to provide new insights about paedomorphosis and the role of thyroid hormone in development and evolution."		* '''Rediscovering the Axolotl as a Model for {{Thyroid}} Hormone Dependent Development'''{{#pmid:31031711\|PMID31031711}} "The Mexican axolotl (Ambystoma mexicanum) is an important model organism in biomedical research. Much current attention is focused on the axolotl's amazing ability to regenerate tissues and whole organs after injury. However, not forgotten is the axolotl's equally amazing ability to thwart aspects of tissue maturation and retain juvenile morphology into the adult phase of life. Unlike close tiger salamander relatives that undergo a thyroid hormone regulated metamorphosis, the axolotl does not typically undergo a metamorphosis. Instead, the axolotl exhibits a paedomorphic mode of development that enables a completely aquatic life cycle. The evolution of paedomorphosis allowed axolotls to exploit relatively permanent habitats in Mexico, and preadapted axolotls for domestication and laboratory study. In this perspective, we first introduce the axolotl and the various meanings of paedomorphosis, and then stress the need to move beyond endocrinology-guided approaches to understand the axolotl's hypothyroid state. With the recent completion of the axolotl genome assembly and established methods to manipulate gene functions, the axolotl is poised to provide new insights about paedomorphosis and the role of thyroid hormone in development and evolution."

	* '''Acquisition and reconstruction of 4D surfaces of axolotl embryos with the flipping stage robotic microscope'''{{#pmid:30554603\|PMID30554603}} "We have designed and constructed a Flipping Stage for a light microscope that can view the whole exterior surface of a 2 mm diameter developing axolotl salamander embryo. It works by rapidly inverting the bottom-heavy embryo, imaging it as it rights itself. The images are then montaged to reconstruct the whole 3D surface versus time, for a full 4D record of the surface. Imaging early stage axolotl development will help discover how cell differentiation and movement takes place in the early embryo. For example, the switch from ectodermal to neural plate cells takes place on the top, animal surface portion the egg/embryo and can be observed using the flipping stage microscope. Detailed pictures of the whole surface need to be obtained so that cell tracking and event histories, such as cell divisions and participation in differentiation waves, of individual cells can be recorded. Imaging the whole exterior of the eggs/embryos will allow for the analysis of cell behavior and the forces the cells experience in their natural setting in the intact or manipulated embryo."
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			* '''Acquisition and reconstruction of 4D surfaces of axolotl embryos with the flipping stage robotic microscope'''{{#pmid:30554603\|PMID30554603}} "We have designed and constructed a Flipping Stage for a light microscope that can view the whole exterior surface of a 2 mm diameter developing axolotl salamander embryo. It works by rapidly inverting the bottom-heavy embryo, imaging it as it rights itself. The images are then montaged to reconstruct the whole 3D surface versus time, for a full 4D record of the surface. Imaging early stage axolotl development will help discover how cell differentiation and movement takes place in the early embryo. For example, the switch from ectodermal to neural plate cells takes place on the top, animal surface portion the egg/embryo and can be observed using the flipping stage microscope. Detailed pictures of the whole surface need to be obtained so that cell tracking and event histories, such as cell divisions and participation in differentiation waves, of individual cells can be recorded. Imaging the whole exterior of the eggs/embryos will allow for the analysis of cell behavior and the forces the cells experience in their natural setting in the intact or manipulated embryo."

	* '''The axolotl genome and the evolution of key tissue formation regulators'''{{#pmid:29364872\|PMID29364872}} "Salamanders serve as important tetrapod models for developmental, regeneration and evolutionary studies. An extensive molecular toolkit makes the Mexican axolotl (Ambystoma mexicanum) a key representative salamander for molecular investigations. Here we report the sequencing and assembly of the 32-gigabase-pair axolotl genome using an approach that combined long-read sequencing, optical mapping and development of a new genome assembler (MARVEL). We observed a size expansion of introns and intergenic regions, largely attributable to multiplication of long terminal repeat retroelements. We provide evidence that intron size in developmental genes is under constraint and that species-restricted genes may contribute to limb regeneration. The axolotl genome assembly does not contain the essential developmental gene Pax3. However, mutation of the axolotl Pax3 paralogue Pax7 resulted in an axolotl phenotype that was similar to those seen in Pax3-/- and Pax7-/- mutant mice." {{Pax}}		* '''The axolotl genome and the evolution of key tissue formation regulators'''{{#pmid:29364872\|PMID29364872}} "Salamanders serve as important tetrapod models for developmental, regeneration and evolutionary studies. An extensive molecular toolkit makes the Mexican axolotl (Ambystoma mexicanum) a key representative salamander for molecular investigations. Here we report the sequencing and assembly of the 32-gigabase-pair axolotl genome using an approach that combined long-read sequencing, optical mapping and development of a new genome assembler (MARVEL). We observed a size expansion of introns and intergenic regions, largely attributable to multiplication of long terminal repeat retroelements. We provide evidence that intron size in developmental genes is under constraint and that species-restricted genes may contribute to limb regeneration. The axolotl genome assembly does not contain the essential developmental gene Pax3. However, mutation of the axolotl Pax3 paralogue Pax7 resulted in an axolotl phenotype that was similar to those seen in Pax3-/- and Pax7-/- mutant mice." {{Pax}}

Z8600021 at 05:47, 26 February 2022

2022-02-26T05:47:24Z

← Older revision		Revision as of 15:47, 26 February 2022
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	{{#pmid:30429597}}		{{#pmid:30429597}}

			{{#pmid:29364872}}

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Z8600021 at 19:19, 27 August 2020

2020-08-27T19:19:21Z

← Older revision		Revision as of 05:19, 28 August 2020
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	==External Links==		==External Links==
	{{External Links}}		{{External Links}}

	* [http://www.ambystoma.de/html/axolotl/axolotl_development.html Axolotl - Developmental stages]		* [http://www.ambystoma.de/html/axolotl/axolotl_development.html Axolotl - Developmental stages]
	* [http://www.axolotl.org/embryo_series.htm Axolotl Org - Developmental stages]		* [http://www.axolotl.org/embryo_series.htm Axolotl Org - Developmental stages]
	* Oxford University Press [http://www.oup.com/us/catalog/general/subject/LifeSciences/?view=usa&ci=9780195050738 Developmental Biology of the Axolotl, John B. Armstrong and George M. Malacinski]		* Oxford University Press [http://www.oup.com/us/catalog/general/subject/LifeSciences/?view=usa&ci=9780195050738 Developmental Biology of the Axolotl, John B. Armstrong and George M. Malacinski]
			* [www.axolotl-omics.org Axolotl-omics] website that allows rapid ortholog searches, and access to genome and transcriptomic resources.

	----		----

Z8600021 at 19:17, 27 August 2020

2020-08-27T19:17:26Z

← Older revision		Revision as of 05:17, 28 August 2020
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			* '''BMP signaling is essential for sustaining proximo-distal progression in regenerating axolotl limbs'''{{#pmid:32665245\|PMID32665245}} "Amputation of a salamander {{limb}} triggers a regeneration process that is perfect. A limited number of genes have been studied in this context and even fewer have been analyzed functionally. In this work, we use the {{BMP}} signaling inhibitor LDN193189 on Ambystoma mexicanum to explore the role of BMPs in regeneration. We find that BMP signaling is required for proper expression of various patterning genes and that its inhibition causes major defects in the regenerated limbs. {{Fgf}}8 is down-regulated when BMP signaling is blocked, but ectopic injection of either human or axolotl protein did not rescue the defects. By administering LDN193189 treatments at different time points during regeneration, we show clearly that limb regeneration progresses in a proximal to distal fashion. This demonstrates that BMPs play a major role in patterning of regenerated limbs and that regeneration is a progressive process like development."

	* '''Rediscovering the Axolotl as a Model for {{Thyroid}} Hormone Dependent Development'''{{#pmid:31031711\|PMID31031711}} "The Mexican axolotl (Ambystoma mexicanum) is an important model organism in biomedical research. Much current attention is focused on the axolotl's amazing ability to regenerate tissues and whole organs after injury. However, not forgotten is the axolotl's equally amazing ability to thwart aspects of tissue maturation and retain juvenile morphology into the adult phase of life. Unlike close tiger salamander relatives that undergo a thyroid hormone regulated metamorphosis, the axolotl does not typically undergo a metamorphosis. Instead, the axolotl exhibits a paedomorphic mode of development that enables a completely aquatic life cycle. The evolution of paedomorphosis allowed axolotls to exploit relatively permanent habitats in Mexico, and preadapted axolotls for domestication and laboratory study. In this perspective, we first introduce the axolotl and the various meanings of paedomorphosis, and then stress the need to move beyond endocrinology-guided approaches to understand the axolotl's hypothyroid state. With the recent completion of the axolotl genome assembly and established methods to manipulate gene functions, the axolotl is poised to provide new insights about paedomorphosis and the role of thyroid hormone in development and evolution."		* '''Rediscovering the Axolotl as a Model for {{Thyroid}} Hormone Dependent Development'''{{#pmid:31031711\|PMID31031711}} "The Mexican axolotl (Ambystoma mexicanum) is an important model organism in biomedical research. Much current attention is focused on the axolotl's amazing ability to regenerate tissues and whole organs after injury. However, not forgotten is the axolotl's equally amazing ability to thwart aspects of tissue maturation and retain juvenile morphology into the adult phase of life. Unlike close tiger salamander relatives that undergo a thyroid hormone regulated metamorphosis, the axolotl does not typically undergo a metamorphosis. Instead, the axolotl exhibits a paedomorphic mode of development that enables a completely aquatic life cycle. The evolution of paedomorphosis allowed axolotls to exploit relatively permanent habitats in Mexico, and preadapted axolotls for domestication and laboratory study. In this perspective, we first introduce the axolotl and the various meanings of paedomorphosis, and then stress the need to move beyond endocrinology-guided approaches to understand the axolotl's hypothyroid state. With the recent completion of the axolotl genome assembly and established methods to manipulate gene functions, the axolotl is poised to provide new insights about paedomorphosis and the role of thyroid hormone in development and evolution."

	* '''Acquisition and reconstruction of 4D surfaces of axolotl embryos with the flipping stage robotic microscope'''{{#pmid:30554603\|PMID30554603}} "We have designed and constructed a Flipping Stage for a light microscope that can view the whole exterior surface of a 2 mm diameter developing axolotl salamander embryo. It works by rapidly inverting the bottom-heavy embryo, imaging it as it rights itself. The images are then montaged to reconstruct the whole 3D surface versus time, for a full 4D record of the surface. Imaging early stage axolotl development will help discover how cell differentiation and movement takes place in the early embryo. For example, the switch from ectodermal to neural plate cells takes place on the top, animal surface portion the egg/embryo and can be observed using the flipping stage microscope. Detailed pictures of the whole surface need to be obtained so that cell tracking and event histories, such as cell divisions and participation in differentiation waves, of individual cells can be recorded. Imaging the whole exterior of the eggs/embryos will allow for the analysis of cell behavior and the forces the cells experience in their natural setting in the intact or manipulated embryo."		* '''Acquisition and reconstruction of 4D surfaces of axolotl embryos with the flipping stage robotic microscope'''{{#pmid:30554603\|PMID30554603}} "We have designed and constructed a Flipping Stage for a light microscope that can view the whole exterior surface of a 2 mm diameter developing axolotl salamander embryo. It works by rapidly inverting the bottom-heavy embryo, imaging it as it rights itself. The images are then montaged to reconstruct the whole 3D surface versus time, for a full 4D record of the surface. Imaging early stage axolotl development will help discover how cell differentiation and movement takes place in the early embryo. For example, the switch from ectodermal to neural plate cells takes place on the top, animal surface portion the egg/embryo and can be observed using the flipping stage microscope. Detailed pictures of the whole surface need to be obtained so that cell tracking and event histories, such as cell divisions and participation in differentiation waves, of individual cells can be recorded. Imaging the whole exterior of the eggs/embryos will allow for the analysis of cell behavior and the forces the cells experience in their natural setting in the intact or manipulated embryo."

	* '''The axolotl genome and the evolution of key tissue formation regulators'''{{#pmid:29364872\|PMID29364872}} "Salamanders serve as important tetrapod models for developmental, regeneration and evolutionary studies. An extensive molecular toolkit makes the Mexican axolotl (Ambystoma mexicanum) a key representative salamander for molecular investigations. Here we report the sequencing and assembly of the 32-gigabase-pair axolotl genome using an approach that combined long-read sequencing, optical mapping and development of a new genome assembler (MARVEL). We observed a size expansion of introns and intergenic regions, largely attributable to multiplication of long terminal repeat retroelements. We provide evidence that intron size in developmental genes is under constraint and that species-restricted genes may contribute to limb regeneration. The axolotl genome assembly does not contain the essential developmental gene Pax3. However, mutation of the axolotl Pax3 paralogue Pax7 resulted in an axolotl phenotype that was similar to those seen in Pax3-/- and Pax7-/- mutant mice." [[Developmental Signals - Pax\|Pax]]

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	\| [[File:Mark_Hill.jpg\|90px\|left]] {{Most_Recent_Refs}}		\| [[File:Mark_Hill.jpg\|90px\|left]] {{Most_Recent_Refs}}

	Search term: [http://www.ncbi.nlm.nih.gov/pubmed/?term=Axolotl+Development ''Axolotl Development'']		Search term: [http://www.ncbi.nlm.nih.gov/pubmed/?term=Axolotl+Development ''Axolotl Development''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Axolotl+Embryology ''Axolotl Embryology''] \| [http://www.ncbi.nlm.nih.gov/pubmed/?term=Axolotl+Limb+Development ''Axolotl Limb Development'']

	\|}		\|}
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	\| {{Older papers}}		\| {{Older papers}}
			* '''The axolotl genome and the evolution of key tissue formation regulators'''{{#pmid:29364872\|PMID29364872}} "Salamanders serve as important tetrapod models for developmental, regeneration and evolutionary studies. An extensive molecular toolkit makes the Mexican axolotl (Ambystoma mexicanum) a key representative salamander for molecular investigations. Here we report the sequencing and assembly of the 32-gigabase-pair axolotl genome using an approach that combined long-read sequencing, optical mapping and development of a new genome assembler (MARVEL). We observed a size expansion of introns and intergenic regions, largely attributable to multiplication of long terminal repeat retroelements. We provide evidence that intron size in developmental genes is under constraint and that species-restricted genes may contribute to limb regeneration. The axolotl genome assembly does not contain the essential developmental gene Pax3. However, mutation of the axolotl Pax3 paralogue Pax7 resulted in an axolotl phenotype that was similar to those seen in Pax3-/- and Pax7-/- mutant mice." {{Pax}}

	* '''Morphological and transcriptomic analyses reveal three discrete primary stages of postembryonic development in the common fire salamander, Salamandra salamandra'''{{#pmid:29504232\|PMID29504232}} "The postembryonic development of amphibians has been characterized as divided into three predominant periods, hereafter named primary developmental stages: premetamorphosis (PreM), prometamorphosis (ProM), metamorphic climax (Meta), and completion of metamorphosis (PostM), largely based on examination of anuran development. ...Our results support that primary stages of postembryonic development in caudates are homologous to those of anurans, and offer a baseline for the study of the evolution of developmental modes."		* '''Morphological and transcriptomic analyses reveal three discrete primary stages of postembryonic development in the common fire salamander, Salamandra salamandra'''{{#pmid:29504232\|PMID29504232}} "The postembryonic development of amphibians has been characterized as divided into three predominant periods, hereafter named primary developmental stages: premetamorphosis (PreM), prometamorphosis (ProM), metamorphic climax (Meta), and completion of metamorphosis (PostM), largely based on examination of anuran development. ...Our results support that primary stages of postembryonic development in caudates are homologous to those of anurans, and offer a baseline for the study of the evolution of developmental modes."

Z8600021 at 19:14, 27 August 2020

2020-08-27T19:14:02Z

← Older revision		Revision as of 05:14, 28 August 2020
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	===Articles===		===Articles===

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	{{#pmid:30429597}}		{{#pmid:30429597}}

Z8600021 at 03:24, 18 July 2019

2019-07-18T03:24:37Z

← Older revision		Revision as of 13:24, 18 July 2019
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	* '''The axolotl genome and the evolution of key tissue formation regulators'''{{#pmid:29364872\|PMID29364872}} "Salamanders serve as important tetrapod models for developmental, regeneration and evolutionary studies. An extensive molecular toolkit makes the Mexican axolotl (Ambystoma mexicanum) a key representative salamander for molecular investigations. Here we report the sequencing and assembly of the 32-gigabase-pair axolotl genome using an approach that combined long-read sequencing, optical mapping and development of a new genome assembler (MARVEL). We observed a size expansion of introns and intergenic regions, largely attributable to multiplication of long terminal repeat retroelements. We provide evidence that intron size in developmental genes is under constraint and that species-restricted genes may contribute to limb regeneration. The axolotl genome assembly does not contain the essential developmental gene Pax3. However, mutation of the axolotl Pax3 paralogue Pax7 resulted in an axolotl phenotype that was similar to those seen in Pax3-/- and Pax7-/- mutant mice." [[Developmental Signals - Pax\|Pax]]		* '''The axolotl genome and the evolution of key tissue formation regulators'''{{#pmid:29364872\|PMID29364872}} "Salamanders serve as important tetrapod models for developmental, regeneration and evolutionary studies. An extensive molecular toolkit makes the Mexican axolotl (Ambystoma mexicanum) a key representative salamander for molecular investigations. Here we report the sequencing and assembly of the 32-gigabase-pair axolotl genome using an approach that combined long-read sequencing, optical mapping and development of a new genome assembler (MARVEL). We observed a size expansion of introns and intergenic regions, largely attributable to multiplication of long terminal repeat retroelements. We provide evidence that intron size in developmental genes is under constraint and that species-restricted genes may contribute to limb regeneration. The axolotl genome assembly does not contain the essential developmental gene Pax3. However, mutation of the axolotl Pax3 paralogue Pax7 resulted in an axolotl phenotype that was similar to those seen in Pax3-/- and Pax7-/- mutant mice." [[Developmental Signals - Pax\|Pax]]

	* '''Morphological and transcriptomic analyses reveal three discrete primary stages of postembryonic development in the common fire salamander, Salamandra salamandra'''{{#pmid:29504232\|PMID29504232}} "The postembryonic development of amphibians has been characterized as divided into three predominant periods, hereafter named primary developmental stages: premetamorphosis (PreM), prometamorphosis (ProM), metamorphic climax (Meta), and completion of metamorphosis (PostM), largely based on examination of anuran development. ...Our results support that primary stages of postembryonic development in caudates are homologous to those of anurans, and offer a baseline for the study of the evolution of developmental modes."

	\|}		\|}
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	\|-		\|-
	\| {{Older papers}}		\| {{Older papers}}
			* '''Morphological and transcriptomic analyses reveal three discrete primary stages of postembryonic development in the common fire salamander, Salamandra salamandra'''{{#pmid:29504232\|PMID29504232}} "The postembryonic development of amphibians has been characterized as divided into three predominant periods, hereafter named primary developmental stages: premetamorphosis (PreM), prometamorphosis (ProM), metamorphic climax (Meta), and completion of metamorphosis (PostM), largely based on examination of anuran development. ...Our results support that primary stages of postembryonic development in caudates are homologous to those of anurans, and offer a baseline for the study of the evolution of developmental modes."

	* '''Dual embryonic origin and patterning of the pharyngeal skeleton in the axolotl'''{{#pmid:25963195\|PMID25963195}} "The impressive morphological diversification of vertebrates was achieved in part by innovation and modification of the pharyngeal skeleton. Extensive fate mapping in amniote models has revealed a primarily cranial neural crest derivation of the pharyngeal skeleton....Our fate map confirms a dual embryonic origin of the pharyngeal skeleton in urodeles, including derivation of basibranchial 2 from mesoderm closely associated with the second heart field. Additionally, heterotopic transplantation experiments reveal lineage restriction of mesodermal cells that contribute to pharyngeal cartilage. The mesoderm-derived component of the pharyngeal skeleton appears to be particularly sensitive to retinoic acid (RA): administration of exogenous RA leads to loss of the second basibranchial, but not the first. Neural crest was undoubtedly critical in the evolution of the vertebrate pharyngeal skeleton, but mesoderm may have played a central role in forming ventromedial elements, in particular. When and how many times during vertebrate phylogeny a mesodermal contribution to the pharyngeal skeleton evolved remain to be resolved."		* '''Dual embryonic origin and patterning of the pharyngeal skeleton in the axolotl'''{{#pmid:25963195\|PMID25963195}} "The impressive morphological diversification of vertebrates was achieved in part by innovation and modification of the pharyngeal skeleton. Extensive fate mapping in amniote models has revealed a primarily cranial neural crest derivation of the pharyngeal skeleton....Our fate map confirms a dual embryonic origin of the pharyngeal skeleton in urodeles, including derivation of basibranchial 2 from mesoderm closely associated with the second heart field. Additionally, heterotopic transplantation experiments reveal lineage restriction of mesodermal cells that contribute to pharyngeal cartilage. The mesoderm-derived component of the pharyngeal skeleton appears to be particularly sensitive to retinoic acid (RA): administration of exogenous RA leads to loss of the second basibranchial, but not the first. Neural crest was undoubtedly critical in the evolution of the vertebrate pharyngeal skeleton, but mesoderm may have played a central role in forming ventromedial elements, in particular. When and how many times during vertebrate phylogeny a mesodermal contribution to the pharyngeal skeleton evolved remain to be resolved."

Z8600021 at 03:23, 18 July 2019

2019-07-18T03:23:19Z

← Older revision		Revision as of 13:23, 18 July 2019
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			* '''Rediscovering the Axolotl as a Model for {{Thyroid}} Hormone Dependent Development'''{{#pmid:31031711\|PMID31031711}} "The Mexican axolotl (Ambystoma mexicanum) is an important model organism in biomedical research. Much current attention is focused on the axolotl's amazing ability to regenerate tissues and whole organs after injury. However, not forgotten is the axolotl's equally amazing ability to thwart aspects of tissue maturation and retain juvenile morphology into the adult phase of life. Unlike close tiger salamander relatives that undergo a thyroid hormone regulated metamorphosis, the axolotl does not typically undergo a metamorphosis. Instead, the axolotl exhibits a paedomorphic mode of development that enables a completely aquatic life cycle. The evolution of paedomorphosis allowed axolotls to exploit relatively permanent habitats in Mexico, and preadapted axolotls for domestication and laboratory study. In this perspective, we first introduce the axolotl and the various meanings of paedomorphosis, and then stress the need to move beyond endocrinology-guided approaches to understand the axolotl's hypothyroid state. With the recent completion of the axolotl genome assembly and established methods to manipulate gene functions, the axolotl is poised to provide new insights about paedomorphosis and the role of thyroid hormone in development and evolution."

	* '''Acquisition and reconstruction of 4D surfaces of axolotl embryos with the flipping stage robotic microscope'''{{#pmid:30554603\|PMID30554603}} "We have designed and constructed a Flipping Stage for a light microscope that can view the whole exterior surface of a 2 mm diameter developing axolotl salamander embryo. It works by rapidly inverting the bottom-heavy embryo, imaging it as it rights itself. The images are then montaged to reconstruct the whole 3D surface versus time, for a full 4D record of the surface. Imaging early stage axolotl development will help discover how cell differentiation and movement takes place in the early embryo. For example, the switch from ectodermal to neural plate cells takes place on the top, animal surface portion the egg/embryo and can be observed using the flipping stage microscope. Detailed pictures of the whole surface need to be obtained so that cell tracking and event histories, such as cell divisions and participation in differentiation waves, of individual cells can be recorded. Imaging the whole exterior of the eggs/embryos will allow for the analysis of cell behavior and the forces the cells experience in their natural setting in the intact or manipulated embryo."		* '''Acquisition and reconstruction of 4D surfaces of axolotl embryos with the flipping stage robotic microscope'''{{#pmid:30554603\|PMID30554603}} "We have designed and constructed a Flipping Stage for a light microscope that can view the whole exterior surface of a 2 mm diameter developing axolotl salamander embryo. It works by rapidly inverting the bottom-heavy embryo, imaging it as it rights itself. The images are then montaged to reconstruct the whole 3D surface versus time, for a full 4D record of the surface. Imaging early stage axolotl development will help discover how cell differentiation and movement takes place in the early embryo. For example, the switch from ectodermal to neural plate cells takes place on the top, animal surface portion the egg/embryo and can be observed using the flipping stage microscope. Detailed pictures of the whole surface need to be obtained so that cell tracking and event histories, such as cell divisions and participation in differentiation waves, of individual cells can be recorded. Imaging the whole exterior of the eggs/embryos will allow for the analysis of cell behavior and the forces the cells experience in their natural setting in the intact or manipulated embryo."

Z8600021 at 11:23, 6 Ocak 2019

2019-01-06T11:23:51Z

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	===Reviews===		===Reviews===

	{{#pmid:30240720}}		{{#pmid:30240720}}

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			{{#pmid:30429597}}

	{{#pmid:22369645}}		{{#pmid:22369645}}

Z8600021 at 11:21, 6 Ocak 2019

2019-01-06T11:21:38Z

← Older revision		Revision as of 21:21, 6 Ocak 2019
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			* '''Acquisition and reconstruction of 4D surfaces of axolotl embryos with the flipping stage robotic microscope'''{{#pmid:30554603\|PMID30554603}} "We have designed and constructed a Flipping Stage for a light microscope that can view the whole exterior surface of a 2 mm diameter developing axolotl salamander embryo. It works by rapidly inverting the bottom-heavy embryo, imaging it as it rights itself. The images are then montaged to reconstruct the whole 3D surface versus time, for a full 4D record of the surface. Imaging early stage axolotl development will help discover how cell differentiation and movement takes place in the early embryo. For example, the switch from ectodermal to neural plate cells takes place on the top, animal surface portion the egg/embryo and can be observed using the flipping stage microscope. Detailed pictures of the whole surface need to be obtained so that cell tracking and event histories, such as cell divisions and participation in differentiation waves, of individual cells can be recorded. Imaging the whole exterior of the eggs/embryos will allow for the analysis of cell behavior and the forces the cells experience in their natural setting in the intact or manipulated embryo."

	* '''The axolotl genome and the evolution of key tissue formation regulators'''{{#pmid:29364872\|PMID29364872}} "Salamanders serve as important tetrapod models for developmental, regeneration and evolutionary studies. An extensive molecular toolkit makes the Mexican axolotl (Ambystoma mexicanum) a key representative salamander for molecular investigations. Here we report the sequencing and assembly of the 32-gigabase-pair axolotl genome using an approach that combined long-read sequencing, optical mapping and development of a new genome assembler (MARVEL). We observed a size expansion of introns and intergenic regions, largely attributable to multiplication of long terminal repeat retroelements. We provide evidence that intron size in developmental genes is under constraint and that species-restricted genes may contribute to limb regeneration. The axolotl genome assembly does not contain the essential developmental gene Pax3. However, mutation of the axolotl Pax3 paralogue Pax7 resulted in an axolotl phenotype that was similar to those seen in Pax3-/- and Pax7-/- mutant mice." [[Developmental Signals - Pax\|Pax]]		* '''The axolotl genome and the evolution of key tissue formation regulators'''{{#pmid:29364872\|PMID29364872}} "Salamanders serve as important tetrapod models for developmental, regeneration and evolutionary studies. An extensive molecular toolkit makes the Mexican axolotl (Ambystoma mexicanum) a key representative salamander for molecular investigations. Here we report the sequencing and assembly of the 32-gigabase-pair axolotl genome using an approach that combined long-read sequencing, optical mapping and development of a new genome assembler (MARVEL). We observed a size expansion of introns and intergenic regions, largely attributable to multiplication of long terminal repeat retroelements. We provide evidence that intron size in developmental genes is under constraint and that species-restricted genes may contribute to limb regeneration. The axolotl genome assembly does not contain the essential developmental gene Pax3. However, mutation of the axolotl Pax3 paralogue Pax7 resulted in an axolotl phenotype that was similar to those seen in Pax3-/- and Pax7-/- mutant mice." [[Developmental Signals - Pax\|Pax]]

	* '''Morphological and transcriptomic analyses reveal three discrete primary stages of postembryonic development in the common fire salamander, Salamandra salamandra'''{{#pmid:29504232\|PMID29504232}} "The postembryonic development of amphibians has been characterized as divided into three predominant periods, hereafter named primary developmental stages: premetamorphosis (PreM), prometamorphosis (ProM), metamorphic climax (Meta), and completion of metamorphosis (PostM), largely based on examination of anuran development. ...Our results support that primary stages of postembryonic development in caudates are homologous to those of anurans, and offer a baseline for the study of the evolution of developmental modes."		* '''Morphological and transcriptomic analyses reveal three discrete primary stages of postembryonic development in the common fire salamander, Salamandra salamandra'''{{#pmid:29504232\|PMID29504232}} "The postembryonic development of amphibians has been characterized as divided into three predominant periods, hereafter named primary developmental stages: premetamorphosis (PreM), prometamorphosis (ProM), metamorphic climax (Meta), and completion of metamorphosis (PostM), largely based on examination of anuran development. ...Our results support that primary stages of postembryonic development in caudates are homologous to those of anurans, and offer a baseline for the study of the evolution of developmental modes."

	* '''Dual embryonic origin and patterning of the pharyngeal skeleton in the axolotl'''{{#pmid:25963195\|PMID25963195}} "The impressive morphological diversification of vertebrates was achieved in part by innovation and modification of the pharyngeal skeleton. Extensive fate mapping in amniote models has revealed a primarily cranial neural crest derivation of the pharyngeal skeleton....Our fate map confirms a dual embryonic origin of the pharyngeal skeleton in urodeles, including derivation of basibranchial 2 from mesoderm closely associated with the second heart field. Additionally, heterotopic transplantation experiments reveal lineage restriction of mesodermal cells that contribute to pharyngeal cartilage. The mesoderm-derived component of the pharyngeal skeleton appears to be particularly sensitive to retinoic acid (RA): administration of exogenous RA leads to loss of the second basibranchial, but not the first. Neural crest was undoubtedly critical in the evolution of the vertebrate pharyngeal skeleton, but mesoderm may have played a central role in forming ventromedial elements, in particular. When and how many times during vertebrate phylogeny a mesodermal contribution to the pharyngeal skeleton evolved remain to be resolved."

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			* '''Dual embryonic origin and patterning of the pharyngeal skeleton in the axolotl'''{{#pmid:25963195\|PMID25963195}} "The impressive morphological diversification of vertebrates was achieved in part by innovation and modification of the pharyngeal skeleton. Extensive fate mapping in amniote models has revealed a primarily cranial neural crest derivation of the pharyngeal skeleton....Our fate map confirms a dual embryonic origin of the pharyngeal skeleton in urodeles, including derivation of basibranchial 2 from mesoderm closely associated with the second heart field. Additionally, heterotopic transplantation experiments reveal lineage restriction of mesodermal cells that contribute to pharyngeal cartilage. The mesoderm-derived component of the pharyngeal skeleton appears to be particularly sensitive to retinoic acid (RA): administration of exogenous RA leads to loss of the second basibranchial, but not the first. Neural crest was undoubtedly critical in the evolution of the vertebrate pharyngeal skeleton, but mesoderm may have played a central role in forming ventromedial elements, in particular. When and how many times during vertebrate phylogeny a mesodermal contribution to the pharyngeal skeleton evolved remain to be resolved."

	* '''Stochastic specification of primordial germ cells from mesoderm precursors in axolotl embryos'''{{#pmid:24917499\|PMID24917499}} "A common feature of development in most vertebrate models is the early segregation of the germ line from the soma. For example, in Xenopus and zebrafish embryos primordial germ cells (PGCs) are specified by germ plasm that is inherited from the egg; in mice, Blimp1 expression in the epiblast mediates the commitment of cells to the germ line. How these disparate mechanisms of PGC specification evolved is unknown. Here, in order to identify the ancestral mechanism of PGC specification in vertebrates, we studied PGC specification in embryos from the axolotl (Mexican salamander), a model for the tetrapod ancestor. In the axolotl, PGCs develop within mesoderm, and classic studies have reported their induction from primitive ectoderm (animal cap). We used an axolotl animal cap system to demonstrate that signalling through FGF and BMP4 induces PGCs. The role of FGF was then confirmed in vivo. We also showed PGC induction by Brachyury, in the presence of BMP4. These conditions induced pluripotent mesodermal precursors that give rise to a variety of somatic cell types, in addition to PGCs. Irreversible restriction of the germ line did not occur until the mid-tailbud stage, days after the somatic germ layers are established. Before this, germline potential was maintained by MAP kinase signalling. We propose that this stochastic mechanism of PGC specification, from mesodermal precursors, is conserved in vertebrates."		* '''Stochastic specification of primordial germ cells from mesoderm precursors in axolotl embryos'''{{#pmid:24917499\|PMID24917499}} "A common feature of development in most vertebrate models is the early segregation of the germ line from the soma. For example, in Xenopus and zebrafish embryos primordial germ cells (PGCs) are specified by germ plasm that is inherited from the egg; in mice, Blimp1 expression in the epiblast mediates the commitment of cells to the germ line. How these disparate mechanisms of PGC specification evolved is unknown. Here, in order to identify the ancestral mechanism of PGC specification in vertebrates, we studied PGC specification in embryos from the axolotl (Mexican salamander), a model for the tetrapod ancestor. In the axolotl, PGCs develop within mesoderm, and classic studies have reported their induction from primitive ectoderm (animal cap). We used an axolotl animal cap system to demonstrate that signalling through FGF and BMP4 induces PGCs. The role of FGF was then confirmed in vivo. We also showed PGC induction by Brachyury, in the presence of BMP4. These conditions induced pluripotent mesodermal precursors that give rise to a variety of somatic cell types, in addition to PGCs. Irreversible restriction of the germ line did not occur until the mid-tailbud stage, days after the somatic germ layers are established. Before this, germline potential was maintained by MAP kinase signalling. We propose that this stochastic mechanism of PGC specification, from mesodermal precursors, is conserved in vertebrates."

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	===Reviews===		===Reviews===
			{{#pmid:30240720}}

	{{#pmid:19030817}}		{{#pmid:19030817}}

Z8600021 at 11:17, 6 Ocak 2019

2019-01-06T11:17:18Z

Show changes