Restoration of the organizer after radical ablation of Hensen's node and the anterior primitive streak in the chick embryo

Development ◽  
1996 ◽  
Vol 122 (10) ◽  
pp. 3263-3273 ◽  
Author(s):  
D. Psychoyos ◽  
C.D. Stern
Keyword(s):  
Sonic Hedgehog ◽  
System Analysis ◽  
Cell Movement ◽  
Complete Removal ◽  
Primitive Streak ◽  
Normal Embryo ◽  
Spemann's Organizer ◽  
Prechordal Mesoderm ◽  
Left Right Asymmetry ◽  
Gut Endoderm

The region of the amniote embryo corresponding to Spemann's organizer in amphibians is Hensen's node, which lies at the tip of the primitive streak during gastrulation. It is a special site in the embryo that can be defined by the presence of progenitors of several axial tissues (notochord, prechordal mesoderm, somites, gut endoderm), by characteristic cell movements, by specific patterns of gene expression (e.g. goosecoid, HNF-3beta, Sonic hedgehog) and, most importantly, by its ability to induce a complete axis, including host-derived neural tissue, when transplanted to an ectopic site. Here, we show that complete removal not only of the node but also of the anterior 40% of the primitive streak leads to the development of normal embryos containing cells with all the fates normally produced by the node. Cell movement pathways through the regenerated node are identical to those seen in the normal embryo. The patterns of expression of HNF-3beta and Sonic hedgehog are also restored, as is their left/right asymmetry, but goosecoid expression is not. When the regenerated node is transplanted to an ectopic site, it induces a complete embryonic axis that includes a fully patterned, host-derived central nervous system. Analysis of the properties of cells surrounding the site of ablation shows that they acquire these properties gradually. We suggest that the organizer is a region of the embryo that is defined by cell interactions and that the node normally inhibits the organizer state in neighbouring cells.

Sonic hedgehog signaling at gastrula stages specifies ventral telencephalic cells in the chick embryo

Development ◽  
2000 ◽  
Vol 127 (15) ◽  
pp. 3283-3293 ◽  
Author(s):  
L. Gunhaga ◽  
T.M. Jessell ◽  
T. Edlund
Keyword(s):  
Sonic Hedgehog ◽  
Neural Tube ◽  
Hedgehog Signaling ◽  
Early Stage ◽  
Primitive Streak ◽  
Cell Types ◽  
Neural Cells ◽  
Sonic Hedgehog Signaling ◽  
Ventral Telencephalon ◽  
Prechordal Mesoderm

A secreted signaling factor, Sonic hedgehog (Shh), has a crucial role in the generation of ventral cell types along the entire rostrocaudal axis of the neural tube. At caudal levels of the neuraxis, Shh is secreted by the notochord and floor plate during the period that ventral cell fates are specified. At anterior prosencephalic levels that give rise to the telencephalon, however, neither the prechordal mesoderm nor the ventral neural tube expresses Shh at the time that the overt ventral character of the telencephalon becomes evident. Thus, the precise role and timing of Shh signaling relevant to the specification of ventral telencephalic identity remains unclear. By analysing neural cell differentiation in chick neural plate explants we provide evidence that neural cells acquire molecular properties characteristic of the ventral telencephalon in response to Shh signals derived from the anterior primitive streak/Hensen's node region at gastrula stages. Exposure of prospective anterior prosencephalic cells to Shh at this early stage is sufficient to initiate a temporal program of differentiation that parallels that of neurons generated normally in the medial ganglionic eminence subdivision of the ventral telencephalon.

Induction of primitive streak and Hensen's node by the posterior marginal zone in the early chick embryo

Development ◽  
1998 ◽  
Vol 125 (17) ◽  
pp. 3521-3534 ◽  
Author(s):  
R.F. Bachvarova ◽  
I. Skromne ◽  
C.D. Stern
Keyword(s):  
Chick Embryo ◽  
Marginal Zone ◽  
Lower Layer ◽  
Primitive Streak ◽  
Normal Embryo ◽  
Anterior Pole ◽  
Posterior Edge ◽  
Amphibian Embryo ◽  
Midline Cells ◽  
Marginal Zones

In the preprimitive streak chick embryo, the search for a region capable of inducing the organizer, equivalent to the Nieuwkoop Center of the amphibian embryo, has focused on Koller's sickle, the hypoblast and the posterior marginal zone. However, no clear evidence for induction of an organizer without contribution from the inducing tissue has been provided for any of these structures. We have used DiI/DiO labeling to establish the fate of midline cells in and around Koller's sickle in the normal embryo. In the epiblast, the boundary between cells that contribute to the streak and those that do not lies at the posterior edge of Koller's sickle, except at stage X when it lies slightly more posteriorly in the epiblast. Hypoblast and endoblast (a second lower layer formed under the streak) have distinct origins in the lower layer, and goosecoid expression distinguishes between them. We then used anterior halves of chick prestreak embryos as recipients for grafts of quail posterior marginal zone; quail cells can be identified subsequently with a quail-specific antibody. Anterior halves alone usually formed a streak, most often from the posterior edge. Quail posterior marginal zones without Koller's sickle were grafted to the anterior side of anterior halves. These grafts were able to increase significantly the frequency of streaks arising from the anterior pole of stage X-XI anterior halves without contributing to the streak or node. Stage XII anterior halves no longer responded. A goosecoid-expressing hypoblast did not form under the induced streak, indicating that it is not required for streak formation. We conclude that the marginal zone posterior to Koller's sickle can induce a streak and node, without contributing cells to the induced streak.

The marginal zone and its contribution to the hypoblast and primitive streak of the chick embryo

Development ◽  
1990 ◽  
Vol 109 (3) ◽  
pp. 667-682 ◽  
Author(s):  
C.D. Stern
Keyword(s):  
Chick Embryo ◽  
Marginal Zone ◽  
Primitive Streak ◽  
Time Lapse ◽  
Study Time ◽  
Fate Mapping ◽  
Deep Part ◽  
Germ Layers ◽  
Gut Endoderm ◽  
Transplantation Experiments

The marginal zone of the chick embryo has been shown to play an important role in the formation of the hypoblast and of the primitive streak. In this study, time-lapse filming, fate mapping, ablation and transplantation experiments were combined to study its contribution to these structures. It was found that the deep (endodermal) portion of the posterior marginal zone contributes to the hypoblast and to the junctional endoblast, while the epiblast portion of the same region contributes to the epiblast of the primitive streak and to the definitive (gut) endoderm derived from it. Within the deep part of the posterior marginal zone, a subpopulation of HNK-1-positive cells contributes to the hypoblast. Removal of the deep part of the marginal zone prevents regeneration of the hypoblast but not the formation of a primitive streak. Removal of both layers of the marginal zone leads to a primitive streak of abnormal morphology but mesendodermal cells nevertheless differentiate. These results show that the two main properties of the posterior marginal zone (contributing to the hypoblast and controlling the site of primitive streak formation) are separable, and reside in different germ layers. This conclusion does not support the idea that the influence of the posterior marginal zone on the development of axial structures is due to it being the source of secondary hypoblast cells.

Hedgehog signals regulate multiple aspects of gastrointestinal development

Development ◽  
2000 ◽  
Vol 127 (12) ◽  
pp. 2763-2772 ◽  
Author(s):  
M. Ramalho-Santos ◽  
D.A. Melton ◽  
A.P. McMahon
Keyword(s):  
Gastrointestinal Tract ◽  
Sonic Hedgehog ◽  
Hedgehog Signaling ◽  
Target Genes ◽  
Critical Role ◽  
Indian Hedgehog ◽  
Cell Proliferation And Differentiation ◽  
Proliferation And Differentiation ◽  
Mesodermal Origin ◽  
Gut Endoderm

The gastrointestinal tract develops from the embryonic gut, which is composed of an endodermally derived epithelium surrounded by cells of mesodermal origin. Cell signaling between these two tissue layers appears to play a critical role in coordinating patterning and organogenesis of the gut and its derivatives. We have assessed the function of Sonic hedgehog and Indian hedgehog genes, which encode members of the Hedgehog family of cell signals. Both are expressed in gut endoderm, whereas target genes are expressed in discrete layers in the mesenchyme. It was unclear whether functional redundancy between the two genes would preclude a genetic analysis of the roles of Hedgehog signaling in the mouse gut. We show here that the mouse gut has both common and separate requirements for Sonic hedgehog and Indian hedgehog. Both Sonic hedgehog and Indian hedgehog mutant mice show reduced smooth muscle, gut malrotation and annular pancreas. Sonic hedgehog mutants display intestinal transformation of the stomach, duodenal stenosis (obstruction), abnormal innervation of the gut and imperforate anus. Indian hedgehog mutants show reduced epithelial stem cell proliferation and differentiation, together with features typical of Hirschsprung's disease (aganglionic colon). These results show that Hedgehog signals are essential for organogenesis of the mammalian gastrointestinal tract and suggest that mutations in members of this signaling pathway may be involved in human gastrointestinal malformations.

scholarly journals Gut endoderm is involved in the transfer of left-right asymmetry from the node to the lateral plate mesoderm in the mouse embryo

Development ◽  
2012 ◽  
Vol 139 (13) ◽  
pp. 2426-2435 ◽  
Author(s):  
R. S. Saund ◽  
M. Kanai-Azuma ◽  
Y. Kanai ◽  
I. Kim ◽  
M. T. Lucero ◽  
...  
Keyword(s):  
Mouse Embryo ◽  
Lateral Plate Mesoderm ◽  
Lateral Plate ◽  
Left Right Asymmetry ◽  
Gut Endoderm

scholarly journals FGF signalling through RAS/MAPK and PI3K pathways regulates cell movement and gene expression in the chicken primitive streak without affecting E-cadherin expression

2011 ◽  
Vol 11 (1) ◽  
pp. 20 ◽  
Author(s):  
Katharine M Hardy ◽  
Tatiana A Yatskievych ◽  
JH Konieczka ◽  
Alexander S Bobbs ◽  
Parker B Antin
Keyword(s):  
Gene Expression ◽  
Cell Movement ◽  
Primitive Streak ◽  
Fgf Signalling ◽  
E Cadherin

scholarly journals Experiments on Embryonic Induction

1934 ◽  
Vol 11 (3) ◽  
pp. 212-217
Author(s):  
C. H. WADDINGTON
Keyword(s):  
Primitive Streak ◽  
Neural Plate ◽  
Chick Embryos ◽  
Embryonic Induction ◽  
Gut Endoderm

It is shown that the ectoderm of the area opaca of chick embryos of the primitive streak stage can react to primitive streak grafts by the formation of an induced neural plate. The conclusion is drawn that the competence to form neural plate is not conferred on ectoderm by the gut endoderm, which determines the formation of the primitive streak.

scholarly journals Differential patterning of ventral midline cells by axial mesoderm is regulated by BMP7 and chordin

Development ◽  
1999 ◽  
Vol 126 (2) ◽  
pp. 397-408 ◽  
Author(s):  
K. Dale ◽  
N. Sattar ◽  
J. Heemskerk ◽  
J.D. Clarke ◽  
M. Placzek ◽  
...  
Keyword(s):  
Sonic Hedgehog ◽  
Floor Plate ◽  
Neural Plate ◽  
Ventral Midline ◽  
Molecular Events ◽  
Morphogenetic Protein ◽  
Explant Cultures ◽  
Prechordal Mesoderm ◽  
Midline Cells ◽  
Bmp Antagonist

Ventral midline cells in the neural tube have distinct properties at different rostrocaudal levels, apparently in response to differential signalling by axial mesoderm. Floor plate cells are induced by sonic hedgehog (SHH) secreted from the notochord whereas ventral midline cells of the rostral diencephalon (RDVM cells) appear to be induced by the dual actions of SHH and bone morphogenetic protein 7 (BMP7) from prechordal mesoderm. We have examined the cellular and molecular events that govern the program of differentiation of RDVM cells under the influence of the axial mesoderm. By fate mapping, we show that prospective RDVM cells migrate rostrally within the neural plate, passing over rostral notochord before establishing register with prechordal mesoderm at stage 7. Despite the co-expression of SHH and BMP7 by rostral notochord, prospective RDVM cells appear to be specified initially as caudal ventral midline neurectodermal cells and to acquire RDVM properties only at stage 7. We provide evidence that the signalling properties of axial mesoderm over this period are regulated by the BMP antagonist, chordin. Chordin is expressed throughout the axial mesoderm as it extends, but is downregulated in prechordal mesoderm coincident with the onset of RDVM cell differentiation. Addition of chordin to conjugate explant cultures of prechordal mesoderm and neural tissue prevents the rostralization of ventral midline cells by prechordal mesoderm. Chordin may thus act to refine the patterning of the ventral midline along the rostrocaudal axis.

Abstract 132: CD13 and ROR2 Mediated Isoloation of hESC Derived Cardiac Mesoderm

2013 ◽  
Vol 113 (suppl_1) ◽  
Author(s):  
Bevin Brady ◽  
Rhys J Skelton ◽  
David A Elliott ◽  
Irving L Weissman ◽  
Reza Ardehali
Keyword(s):  
Embryonic Stem ◽  
Complete Removal ◽  
Primitive Streak ◽  
Hesc Line ◽  
Surface Markers ◽  
Double Positive ◽  
Cardiac Progenitors ◽  
Gene And Protein Expression ◽  
Hesc Lines ◽  
Cardiac Mesoderm

The human heart has a limited regenerative capacity and there is an unmet demand for improved therapies for myocardial disease. Human embryonic stem cell (hESC) derived cardiomyocytes have potential to facilitate the development of both cell-based and pharmaceutical treatments. To date many studies have focused on the efficient generation of cardiomyocytes from hESCs. However, its clinical use has been limited by technical challenges, including the inability to isolate a pure population of cardiovascular progenitors capable of robust engraftment and regeneration. To this end, we have attempted to identify surface markers that facilitate isolation of cardiac mesoderm and cardiovascular progenitors from differentiating hESCs. Lineage-specific reporter hESC lines (MIXL1-GFP and NKX2.5-GFP) were utilized to test prospective isolation of early cardiac progenitors using two novel cell surface markers, CD13 and ROR2. A distinct population of cells co-expressing CD13 and ROR2 was isolated after 3 days of hESC differentiation which exhibited a transcriptional profile similar to primitive streak/mesoderm cells. Gene expression analysis and immunostaining confirmed the enrichment of mesodermal cells and near complete removal of endodermal, ectodermal and undifferentiated cells. To quantify the extent of cardiovascular progenitors generated from CD13/ROR2 expressing cells, an NKX2.5-GFP reporter hESC line was used and the double positive cells were sorted after 3 days and maintained in culture for 14 days. The majority of these cells showed enrichment for cardiovascular cells based on gene and protein expression, phenotype, and transplantation studies. By enabling retrieval of early mesoderm precursors from heterogeneous differentiated hESC populations, we anticipate CD13 and ROR2 should have utility in enriching for subsequent cardiac potential_the necessary first developmental step towards creating purified cardiomyocytes from hESC.

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