The Experts below are selected from a list of 213 Experts worldwide ranked by ideXlab platform
David R Mcclay - One of the best experts on this subject based on the ideXlab platform.
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short range wnt5 signaling initiates specification of sea urchin posterior Ectoderm
Development, 2013Co-Authors: Daniel C Mcintyre, N Seay, Jenifer C Croce, David R McclayAbstract:The border between the posterior Ectoderm and the endoderm is a location where two germ layers meet and establish an enduring relationship that also later serves, in deuterostomes, as the anatomical site of the anus. In the sea urchin, a prototypic deuterostome, the Ectoderm-endoderm boundary is established before gastrulation, and Ectodermal cells at the boundary are thought to provide patterning inputs to the underlying mesenchyme. Here we show that a short-range Wnt5 signal from the endoderm actively patterns the adjacent boundary Ectoderm. This signal activates a unique subcircuit of the Ectoderm gene regulatory network, including the transcription factors IrxA, Nk1, Pax2/5/8 and Lim1, which are ultimately restricted to subregions of the border Ectoderm (BE). Surprisingly, Nodal and BMP2/4, previously shown to be activators of Ectodermal specification and the secondary embryonic axis, instead restrict the expression of these genes to subregions of the BE. A detailed examination showed that endodermal Wnt5 functions as a short-range signal that activates only a narrow band of Ectodermal cells, even though all Ectoderm is competent to receive the signal. Thus, cells in the BE integrate positive and negative signals from both the primary and secondary embryonic axes to correctly locate and specify the border Ectoderm.
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Short-range Wnt5 signaling initiates specification of sea urchin posterior Ectoderm.
Development (Cambridge England), 2013Co-Authors: Daniel C Mcintyre, N Seay, Jenifer C Croce, David R McclayAbstract:The border between the posterior Ectoderm and the endoderm is a location where two germ layers meet and establish an enduring relationship that also later serves, in deuterostomes, as the anatomical site of the anus. In the sea urchin, a prototypic deuterostome, the Ectoderm-endoderm boundary is established before gastrulation, and Ectodermal cells at the boundary are thought to provide patterning inputs to the underlying mesenchyme. Here we show that a short-range Wnt5 signal from the endoderm actively patterns the adjacent boundary Ectoderm. This signal activates a unique subcircuit of the Ectoderm gene regulatory network, including the transcription factors IrxA, Nk1, Pax2/5/8 and Lim1, which are ultimately restricted to subregions of the border Ectoderm (BE). Surprisingly, Nodal and BMP2/4, previously shown to be activators of Ectodermal specification and the secondary embryonic axis, instead restrict the expression of these genes to subregions of the BE. A detailed examination showed that endodermal Wnt5 functions as a short-range signal that activates only a narrow band of Ectodermal cells, even though all Ectoderm is competent to receive the signal. Thus, cells in the BE integrate positive and negative signals from both the primary and secondary embryonic axes to correctly locate and specify the border Ectoderm.
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spdeadringer a sea urchin embryo gene required separately in skeletogenic and oral Ectoderm gene regulatory networks
Developmental Biology, 2003Co-Authors: Gabriele Amore, David R Mcclay, Robert G Yavrouian, Kevin J Peterson, Andrew Ransick, Eric H. DavidsonAbstract:The Spdeadringer (Spdri) gene encodes an ARID-class transcription factor not previously known in sea urchin embryos. We show that Spdri is a key player in two separate developmental gene regulatory networks (GRNs). Spdri is expressed in a biphasic manner, first, after 12 h and until ingression in the skeletogenic descendants of the large micromeres; second, after about 20 h in the oral Ectoderm, where its transcripts remain present at 30–50 mRNA molecules/cell far into development. In both territories, the periods of Spdri expression follow prior territorial specification events. The functional significance of each phase of expression was assessed by determining the effect of an αSpdri morpholino antisense oligonucleotide (MASO) on expression of 17 different mesodermal genes, 8 different oral Ectoderm genes, and 18 other genes expressed specifically during endomesoderm specification. These effects were measured by quantitative PCR, supplemented by whole-mount in situ hybridization and morphological observations. Spdri is shown to act in the micromere descendants in the pathways that result in the expression of batteries of terminal skeletogenic genes. But, in the oral Ectoderm, the same gene participates in the central GRN controlling oral Ectoderm identity. Spdri is linked in the oral Ectoderm GRN with several other genes encoding transcriptional regulators that are expressed specifically in various regions of the oral Ectoderm. If its expression is blocked by treatment with αSpdri MASO, oral-specific features disappear and expression of the aboral Ectoderm marker spec1 encompasses the whole of the Ectoderm. In addition to disappearance of the oral Ectoderm, morphological consequences of αSpdri MASO treatment include failure of spiculogenesis and of correct primary mesenchyme cell (pmc) patterning in the postgastrular embryo, and also failure of gastrulation. To further analyze these phenotypes, chimeric embryos were constructed consisting of two labeled micromeres combined with micromereless 4th cleavage host embryos; either the micromeres or the hosts contained αSpdri MASO. These experiments showed that, while Spdri expression is required autonomously for expression of skeletogenic genes prior to ingression, complete skeletogenesis also requires the expression of oral Ectoderm patterning information. Presentation of this information on the oral side of the blastocoel in turn depends on Spdri expression in the oral Ectoderm. Failure of gastrulation is not due to indirect interference with endomesodermal specification per se, since all endomesodermal genes tested function normally in αSpdri MASO embryos. Part of its cause is interference by αSpdri MASO with a late signaling function on the part of the micromere descendants that is needed to complete clearance of the Soxb1 repressor of gastrulation from the prospective endoderm, but in addition there is a nonautonomous oral Ectoderm effect.
Makoto Asashima - One of the best experts on this subject based on the ideXlab platform.
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endoderm differentiation and inductive effect of activin treated Ectoderm in xenopus
Development Growth & Differentiation, 1999Co-Authors: Hiromasa Ninomiya, Chika Yokota, Shuji Takahashi, Kousuke Tanegashima, Makoto AsashimaAbstract:When presumptive Ectoderm is treated with high concentrations of activin A, it mainly differentiates into axial mesoderm (notochord, muscle) in Xenopus and into yolk-rich endodermal cells in newt (Cynops pyrrhogaster). Xenopus Ectoderm consists of multiple layers, different from the single layer of Cynops Ectoderm. This multilayer structure of Xenopus Ectoderm may prevent complete treatment of activin A and subsequent whole differentiation into endoderm. In the present study, therefore, Xenopus Ectoderm was separated into an outer layer and an inner layer, which were individually treated with a high concentration of activin A (100 ng/mL). Then the differentiation and inductive activity of these Ectodermal cells were examined in explantation and transplantation experiments. In isolation culture, Ectoderm treated with activin A formed endoderm. Ectodermal and mesodermal tissues were seldom found in these explants. The activin-treated Ectoderm induced axial mesoderm and neural tissues, and differentiated into endoderm when it was sandwiched between two sheets of Ectoderm or was transplanted into the ventral marginal zone of other blastulae. These findings suggest that Xenopus Ectoderm treated with a high concentration of activin A forms endoderm and mimics the properties of the organizer as in Cynops.
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Head and trunk-tail organizing effects of the gastrula Ectoderm of Cynops pyrrhogaster after treatment with activin A
Roux's archives of developmental biology, 1995Co-Authors: T. Ariizumi, Makoto AsashimaAbstract:Differentiation tendency and the inducing ability of the presumptive Ectoderm of newt early gastrulae were examined after treatment with activin A at a high concentration (100 ng/ml). The activin-treated Ectoderm differentiated preferentially into yolk-rich endodermal cells. Combination explants consisting of three pieces of activin-treated Ectoderm formed neural tissues and axial mesoderm along with endodermal cells. However, the neural tissue was poorly organized and never showed any central nervous system characteristics. When the activin-treated Ectoderm was sandwiched between two sheets of untreated Ectoderm, the sandwich explants differentiated into trunk-tail or head structures depending on the duration of preculture of activin-treated Ectoderm in Holtfreter's solution. Short-term (0–5 h) precultured Ectoderm induced trunk-tail structures accompanied by axial organs, alimentary canal and beating heart. The arrangement of the explant tissues and organs was similar to that of normal embryos. However, archencephalic structures, such as forebrain and eye, were lacking or deficient. On the other hand, long-term (10–25 h) precultured Ectoderm induced archencephalic structures in addition to axial organs. Lineage analysis of the sandwich explants using fluorescent dyes revealed that the activin-treated Ectoderm mainly differentiated into endodermal cells and induced axial mesoderm and central nervous system in the untreated Ectoderm. These results suggest that activin A is one of the substances involved in triggering endodermal differentiation and that the presumptive Ectoderm induced to form endoderm displays “trunk-tail organizer” or “head organizer” effects, depending on the duration of preculture.
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In Vitro Control of the Embryonic Form of Xenopus laevis by Activin A: Time and Dose-Dependent Inducing Properties of Activin-Treated Ectoderm. (activin/Ectoderm/organizer/Xenopus laevis/neural induction)
Development Growth and Differentiation, 1994Co-Authors: T. Ariizumi, Makoto AsashimaAbstract:The inducing properties of activin-treated Ectoderm of Xenopus laevis were examined by the preculture and sandwich culture methods. Presumptive Ectodermal sheets of the late blastula were treated with 10–100 ng/ml of activin A and precultured for 0–7 hr in Steinberg's solution. They were then sandwiched between two sheets of Ectoderm from other late blastulae. Ectoderm precultured for a short term induced trunk-tail structures, whereas that precultured for a long term induced head structures in addition to trunk-tail structures. These time-dependent changes in inducing properties occurred more rapidly when the concentration of activin A was higher. These results suggest that the activin-treated Ectoderm functioned as a “head organizer” or “trunk-tail organizer” depending upon the concentration of activin A and the duration of preculture. To trace the cell lineage of the sandwich explants, activin-treated Ectoderm labeled with fluorescein-dextran-amine (FDA) was used in this study. The explants sandwiching the long term-precultured Ectoderm formed head structures equipped with non-labeled neural tissues (brain and eye) as well as FDA-labeled mesodermal tissues. These results suggest that the activin-treated Ectoderm mainly differentiates into mesodermal tissues and induces neural tissues as the organizer does in normal development.
Jenifer C Croce - One of the best experts on this subject based on the ideXlab platform.
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short range wnt5 signaling initiates specification of sea urchin posterior Ectoderm
Development, 2013Co-Authors: Daniel C Mcintyre, N Seay, Jenifer C Croce, David R McclayAbstract:The border between the posterior Ectoderm and the endoderm is a location where two germ layers meet and establish an enduring relationship that also later serves, in deuterostomes, as the anatomical site of the anus. In the sea urchin, a prototypic deuterostome, the Ectoderm-endoderm boundary is established before gastrulation, and Ectodermal cells at the boundary are thought to provide patterning inputs to the underlying mesenchyme. Here we show that a short-range Wnt5 signal from the endoderm actively patterns the adjacent boundary Ectoderm. This signal activates a unique subcircuit of the Ectoderm gene regulatory network, including the transcription factors IrxA, Nk1, Pax2/5/8 and Lim1, which are ultimately restricted to subregions of the border Ectoderm (BE). Surprisingly, Nodal and BMP2/4, previously shown to be activators of Ectodermal specification and the secondary embryonic axis, instead restrict the expression of these genes to subregions of the BE. A detailed examination showed that endodermal Wnt5 functions as a short-range signal that activates only a narrow band of Ectodermal cells, even though all Ectoderm is competent to receive the signal. Thus, cells in the BE integrate positive and negative signals from both the primary and secondary embryonic axes to correctly locate and specify the border Ectoderm.
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Short-range Wnt5 signaling initiates specification of sea urchin posterior Ectoderm.
Development (Cambridge England), 2013Co-Authors: Daniel C Mcintyre, N Seay, Jenifer C Croce, David R McclayAbstract:The border between the posterior Ectoderm and the endoderm is a location where two germ layers meet and establish an enduring relationship that also later serves, in deuterostomes, as the anatomical site of the anus. In the sea urchin, a prototypic deuterostome, the Ectoderm-endoderm boundary is established before gastrulation, and Ectodermal cells at the boundary are thought to provide patterning inputs to the underlying mesenchyme. Here we show that a short-range Wnt5 signal from the endoderm actively patterns the adjacent boundary Ectoderm. This signal activates a unique subcircuit of the Ectoderm gene regulatory network, including the transcription factors IrxA, Nk1, Pax2/5/8 and Lim1, which are ultimately restricted to subregions of the border Ectoderm (BE). Surprisingly, Nodal and BMP2/4, previously shown to be activators of Ectodermal specification and the secondary embryonic axis, instead restrict the expression of these genes to subregions of the BE. A detailed examination showed that endodermal Wnt5 functions as a short-range signal that activates only a narrow band of Ectodermal cells, even though all Ectoderm is competent to receive the signal. Thus, cells in the BE integrate positive and negative signals from both the primary and secondary embryonic axes to correctly locate and specify the border Ectoderm.
Daniel C Mcintyre - One of the best experts on this subject based on the ideXlab platform.
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short range wnt5 signaling initiates specification of sea urchin posterior Ectoderm
Development, 2013Co-Authors: Daniel C Mcintyre, N Seay, Jenifer C Croce, David R McclayAbstract:The border between the posterior Ectoderm and the endoderm is a location where two germ layers meet and establish an enduring relationship that also later serves, in deuterostomes, as the anatomical site of the anus. In the sea urchin, a prototypic deuterostome, the Ectoderm-endoderm boundary is established before gastrulation, and Ectodermal cells at the boundary are thought to provide patterning inputs to the underlying mesenchyme. Here we show that a short-range Wnt5 signal from the endoderm actively patterns the adjacent boundary Ectoderm. This signal activates a unique subcircuit of the Ectoderm gene regulatory network, including the transcription factors IrxA, Nk1, Pax2/5/8 and Lim1, which are ultimately restricted to subregions of the border Ectoderm (BE). Surprisingly, Nodal and BMP2/4, previously shown to be activators of Ectodermal specification and the secondary embryonic axis, instead restrict the expression of these genes to subregions of the BE. A detailed examination showed that endodermal Wnt5 functions as a short-range signal that activates only a narrow band of Ectodermal cells, even though all Ectoderm is competent to receive the signal. Thus, cells in the BE integrate positive and negative signals from both the primary and secondary embryonic axes to correctly locate and specify the border Ectoderm.
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Short-range Wnt5 signaling initiates specification of sea urchin posterior Ectoderm.
Development (Cambridge England), 2013Co-Authors: Daniel C Mcintyre, N Seay, Jenifer C Croce, David R McclayAbstract:The border between the posterior Ectoderm and the endoderm is a location where two germ layers meet and establish an enduring relationship that also later serves, in deuterostomes, as the anatomical site of the anus. In the sea urchin, a prototypic deuterostome, the Ectoderm-endoderm boundary is established before gastrulation, and Ectodermal cells at the boundary are thought to provide patterning inputs to the underlying mesenchyme. Here we show that a short-range Wnt5 signal from the endoderm actively patterns the adjacent boundary Ectoderm. This signal activates a unique subcircuit of the Ectoderm gene regulatory network, including the transcription factors IrxA, Nk1, Pax2/5/8 and Lim1, which are ultimately restricted to subregions of the border Ectoderm (BE). Surprisingly, Nodal and BMP2/4, previously shown to be activators of Ectodermal specification and the secondary embryonic axis, instead restrict the expression of these genes to subregions of the BE. A detailed examination showed that endodermal Wnt5 functions as a short-range signal that activates only a narrow band of Ectodermal cells, even though all Ectoderm is competent to receive the signal. Thus, cells in the BE integrate positive and negative signals from both the primary and secondary embryonic axes to correctly locate and specify the border Ectoderm.
Ronald A. Conlon - One of the best experts on this subject based on the ideXlab platform.
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surface Ectoderm is necessary for the morphogenesis of somites
Mechanisms of Development, 2000Co-Authors: Kristen M Correia, Ronald A. ConlonAbstract:Abstract The paraxial mesoderm of the neck and trunk of mouse embryos undergoes extensive morphogenesis in forming somites. Paraxial mesoderm is divided into segments, it elongates along its anterior posterior axis, and its cells organize into epithelia. Experiments were performed to determine if these processes are autonomous to the mesoderm that gives rise to the somites. Presomitic mesoderm at the tailbud stage was cultured in the presence and absence of its adjacent tissues. Somite segmentation occurred in the absence of neural tube, notochord, gut and surface Ectoderm, and occurred in posterior fragments in the absence of anterior presomitic mesoderm. Mesodermal expression of Dll1 and Notch1, genes with roles in segmentation, was largely independent of other tissues, consistent with autonomous segmentation. However, surface Ectoderm was found to be necessary for elongation of the mesoderm along the anterior–posterior axis and for somite epithelialization. To determine if there is specificity in the interaction between Ectoderm and mesoderm, Ectoderm from different sources was recombined with presomitic mesoderm. Surface Ectoderm from only certain parts of the embryo supported somite epithelialization and elongation. Somite epithelialization induced by Ectoderm was correlated with expression of the basic-helix-loop-helix gene Paraxis in the mesoderm. This is consistent with the genetically defined requirement for Paraxis in somite epithelialization. However, trunk Ectoderm was able to induce somite epithelialization in the absence of strong Paraxis expression. We conclude that somitogenesis consists of autonomous segmentation patterned by Notch signaling and nonautonomous induction of elongation and epithelialization by surface Ectoderm.
