Localization of alpha-fetoprotein in developing chick amniotic membrane
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Lateral plate mesoderm
Germ layer
Intermediate mesoderm
Histogenesis
AbstractIn situ hybridization was used to detect the expression of the c-ets1 protooncogene during formation of the germ layers in the chick blastodisc. c-ets1 transcripts were present during the gastrulation process, i.e. when the mesodermal cells invaginated. The expression became down-regulated in lateral plate and the dorsal part of the somites while an intense signal was retained in the intermediate cell mass. When vascujogenesis started, c-ets1 transcripts labelled blood islands and endothelial cells. Before the mesoderm split, transcripts were present over the whole layer, more abundant however on its ventral side in contact with the endoderm. After the mesoderm split, silver grains became distributed asymmetrically: splanchnopleural mesoderm expressed c-ets1 messengers all over while expression in the somatopleural mesoderm was restricted to a few profiles corresponding to small endothelial cell groups. This asymmetrical distribution of c-ets1 transcripts is in agreement with our previous experimental findings establishing the different potentialities of the two mesodermal layers regarding hemopoiesis, vasculogenesis and angiogenesis processes.Key Words: chick embryoc-ets1mesodermendothelial precursors
Germ layer
Lateral plate mesoderm
Intermediate mesoderm
Notochord
Epiblast
Primitive streak
Vasculogenesis
Blastoderm
Nodal signaling
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Germ layer
Intermediate mesoderm
Nodal signaling
Paraxial mesoderm
Lateral plate mesoderm
Primitive streak
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Mesodermal differentiation of dorsal marginal zone (DMZ) before and after invagination was analyzed by a series of combination experiments with different kinds of ectoderm. Lower DMZ of early gastrula didn't show any axial-mesoderm (notochord and somitic mesoderm) but lateral mesoderm (mesenchyme, mesothelium, or blood cells) in combinant with non-competent ventral ectoderm, while combinant with competent ectoderm was found to have well-differentiated axial-mesoderm with deutero-spinocaudal neurals. The axial-mesoderms have origin in the ectoderm. Uninvaginated DMZ of middle gastrula also showed difference in mesodermal differentiation between competent and non-competent ectoderms; axial-mesoderm differentiation was much better in competent than in non-competent. The axial-mesoderm originated from the uninvaginated DMZ. Archenteron roof of late gastrula showed regional difference in mesodermal differentiation in both combinants with competent and non-competent. The present study further demonstrated that there was regionality in promoting effect of induced neurectoderm on axial-mesoderm differentiation of invaginated archenteron roof. The present experiments suggest that the cranio-caudal and dorso-ventral axis formations of amphibian mesoderm are finally determined by sequential and reciprocal interactions between the mesodermal anlage and the overlying ectoderm. It should be also shown that lower DMZ acts to trigger a series of the sequential interactions during primary embryonic induction.
Germ layer
Intermediate mesoderm
Lateral plate mesoderm
Epiblast
Paraxial mesoderm
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Germ layer
Intermediate mesoderm
Histogenesis
Lateral plate mesoderm
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Notochord
Mesenchyme
Intermediate mesoderm
Paraxial mesoderm
Ingression
Lateral plate mesoderm
Limb bud
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Abstract The segregation of cells into germ layers is one of the earliest events in the establishment of cell fate in the embryo. In the zebrafish, endoderm and mesoderm are derived from cells that involute into an internal layer, the hypoblast, whereas ectoderm is derived from cells that remain in the outer layer, the epiblast. In this study, we examine the origin of the zebrafish endoderm and its separation from the mesoderm. By labeling individual cells located at the margin of the blastula, we demonstrate that all structures that are endodermal in origin are derived predominantly from the more dorsal and lateral cells of the blastoderm margin. Frequently marginal cells give rise to both endodermal and mesodermal derivatives, demonstrating that these two lineages have not yet separated. Cells located farther than 4 cell diameters from the margin give rise exclusively to mesoderm, and not to endoderm. Following involution, we see a variety of cellular changes indicating the differentiation of the two germ layers. Endodermal cells gradually flatten and extend filopodial processes forming a noncontiguous inner layer of cells against the yolk. At this time, they also begin to express Forkhead-domain 2 protein. Mesodermal cells form a coherent layer of round cells separating the endoderm and ectoderm. In cyclops-mutant embryos that have reduced mesodermal anlage, we demonstrate that by late gastrulation not only mesodermal but also endodermal cells are fewer in number. This suggests that a common pathway initially specifies germ layers together before a progressive sequence of determinative events segregate endoderm and mesoderm into morphologically distinct germ layers.
Germ layer
Epiblast
Blastula
Blastoderm
Lateral plate mesoderm
Histogenesis
Intermediate mesoderm
Polarity in embryogenesis
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Germ layer
Lateral plate mesoderm
Intermediate mesoderm
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Citations (90)
Lateral plate mesoderm
Germ layer
Intermediate mesoderm
Histogenesis
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Intermediate mesoderm
Germ layer
Lateral plate mesoderm
Primitive streak
Paraxial mesoderm
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Citations (45)
Intermediate mesoderm
Lateral plate mesoderm
Germ layer
PDX1
Paraxial mesoderm
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Citations (246)