A spinal cord fate map in the avian embryo: while regressing, Hensen's node lays down the notochord and floor plate thus joining the spinal cord lateral walls

Development ◽  
1996 ◽  
Vol 122 (9) ◽  
pp. 2599-2610 ◽  
Author(s):  
M. Catala ◽  
M.A. Teillet ◽  
E.M. De Robertis ◽  
M.L. Le Douarin
Keyword(s):  
Spinal Cord ◽  
Primitive Streak ◽  
Floor Plate ◽  
Dorsal Side ◽  
Avian Embryo ◽  
Tail Bud ◽  
Fate Map ◽  
In Ovo ◽  
Somite Stage ◽  
Lateral Walls

The spinal cord of thoracic, lumbar and caudal levels is derived from a region designated as the sinus rhomboidalis in the 6-somite-stage embryo. Using quail/chick grafts performed in ovo, we show the following. (1) The floor plate and notochord derive from a common population of cells, located in Hensen's node, which is equivalent to the chordoneural hinge (CNH) as it was defined at the tail bud stage. (2) The lateral walls and the roof of the neural tube originate caudally and laterally to Hensen's node, during the regression of which the basal plate anlage is bisected by floor plate tissue. (3) Primary and secondary neurulations involve similar morphogenetic movements but, in contrast to primary neurulation, extensive bilateral cell mixing is observed on the dorsal side of the region of secondary neurulation. (4) The posterior midline of the sinus rhomboidalis gives rise to somitic mesoderm and not to spinal cord. Moreover, mesodermal progenitors are spatially arranged along the rest of the primitive streak, more caudal cells giving rise to more lateral embryonic structures. Together with the results reported in our study of tail bud development (Catala, M., Teillet, M.-A. and Le Douarin, N.M. (1995). Mech. Dev. 51, 51–65), these results show that the mechanisms that preside at axial elongation from the 6-somite stage onwards are fundamentally similar during the complete process of neurulation.

Defining subregions of Hensen's node essential for caudalward movement, midline development and cell survival

Development ◽  
1999 ◽  
Vol 126 (21) ◽  
pp. 4771-4783 ◽  
Author(s):  
J.B. Charrier ◽  
M.A. Teillet ◽  
F. Lapointe ◽  
N.M. Le Douarin
Keyword(s):  
Primitive Streak ◽  
Floor Plate ◽  
Paraxial Mesoderm ◽  
Avian Embryo ◽  
Tail Bud ◽  
Anterior Portion ◽  
T Box ◽  
Endodermal Cells ◽  
Further Development ◽  
Midline Development

Hensen's node, also called the chordoneural hinge in the tail bud, is a group of cells that constitutes the organizer of the avian embryo and that expresses the gene HNF-3(β). During gastrulation and neurulation, it undergoes a rostral-to-caudal movement as the embryo elongates. Labeling of Hensen's node by the quail-chick chimera system has shown that, while moving caudally, Hensen's node leaves in its wake not only the notochord but also the floor plate and a longitudinal strand of dorsal endodermal cells. In this work, we demonstrate that the node can be divided into functionally distinct subregions. Caudalward migration of the node depends on the presence of the most posterior region, which is closely apposed to the anterior portion of the primitive streak as defined by expression of the T-box gene Ch-Tbx6L. We call this region the axial-paraxial hinge because it corresponds to the junction of the presumptive midline axial structures (notochord and floor plate) and the paraxial mesoderm. We propose that the axial-paraxial hinge is the equivalent of the neuroenteric canal of other vertebrates such as Xenopus. Blocking the caudal movement of Hensen's node at the 5- to 6-somite stage by removing the axial-paraxial hinge deprives the embryo of midline structures caudal to the brachial level, but does not prevent formation of the neural tube and mesoderm located posteriorly. However, the whole embryonic region generated posterior to the level of Hensen's node arrest undergoes widespread apoptosis within the next 24 hours. Hensen's node-derived structures (notochord and floor plate) thus appear to produce maintenance factor(s) that ensures the survival and further development of adjacent tissues.

scholarly journals Signals from the notochord and floor plate regulate the region-specific expression of two Pax genes in the developing spinal cord

Development ◽  
1993 ◽  
Vol 117 (3) ◽  
pp. 1001-1016 ◽  
Author(s):  
M.D. Goulding ◽  
A. Lumsden ◽  
P. Gruss
Keyword(s):  
Gene Expression ◽  
Spinal Cord ◽  
Neural Tube ◽  
Neural Progenitor Cells ◽  
Expression Patterns ◽  
Primitive Streak ◽  
Floor Plate ◽  
Neural Patterning ◽  
Specific Expression ◽  
Early Effect

Members of the paired box (Pax) gene family are expressed in discrete regions of the developing central nervous system, suggesting a role in neural patterning. In this study, we describe the isolation of the chicken homologues of Pax-3 and Pax-6. Both genes are very highly conserved and share extensive homology with the mouse Pax-3 and Pax-6 genes. Pax-3 is expressed in the primitive streak and in two bands of cells at the lateral extremity of the neural plate. In the spinal cord, Pax-6 is expressed later than Pax-3 with the first detectable expression preceding closure of the neural tube. When the neural tube closes, transcripts of both genes become dorsoventrally restricted in the undifferentiated mitotic neuroepithelium. We show that the removal of the notochord, or implantation of an additional notochord, dramatically alter the dorsoventral (DV) expression patterns of Pax-3 and Pax-6. These manipulations suggest that signals from the notochord and floor plate regulate the establishment of the dorsoventrally restricted expression domains of Pax-3 and Pax-6 in the spinal cord. The rapid changes to Pax gene expression that occur in neural progenitor cells following the grafting of an ectopic notochord suggest that changes to Pax gene expression are an early effect of the notochord on spinal cord patterning.

A kinetic study of the effects of δ-aminolevulinic acid upon the synthesis of embryonic and fetal hemoglobins in the blood islands of the developing chick blastodisc

1970 ◽  
Vol 48 (4) ◽  
pp. 400-406 ◽  
Author(s):  
S. D. Wainwright ◽  
Lillian K. Wainwright
Keyword(s):  
Aminolevulinic Acid ◽  
Fetal Hemoglobin ◽  
Primitive Streak ◽  
Stages Of Development ◽  
In Ovo ◽  
Rapid Synthesis ◽  
Somite Stage ◽  
Stage Of Development ◽  
Solid Media

Chick blastodiscs contained and synthesized a functional (embryonic) hemoglobin as early as the stage of the definitive primitive streak. The rate of hemoglobin synthesis in ovo rose dramatically at about the stage of the 3-somite embryo.Embryos explanted onto solid media at the 3-somite stage of development continued to synthesize hemoglobin in vitro for at least 12 h. The rate of synthesis rose markedly at the 6-somite stage of development, coincident with the onset of rapid synthesis of fetal hemoglobin. A supplement of exogenous aminolevulinic acid markedly stimulated the synthesis of hemoglobin before the 6-somite stage of development, but had little or no effect thereafter. These responses were obtained on both minimal and rich media. Levels of hemoglobin formed were characteristic of the final stages of development attained, regardless of initial stage of development, medium used, or time of incubation required to attain the final level of development.A new regulatory process resulting in elimination of a requirement for continuous presence of egg homogenate for maximal rates of hemoglobin was revealed. This took place between the 6- and 8-somite stages of development at the time of onset of rapid synthesis of fetal hemoglobin.

O2 tension in the spinal cord of the avian embryo

1982 ◽  
Vol 53 (6) ◽  
pp. 1455-1460 ◽  
Author(s):  
B. T. Stokes
Keyword(s):  
Spinal Cord ◽  
Significant Decline ◽  
Avian Embryo ◽  
In Ovo ◽  
Absolute Level ◽  
Frequency Distributions ◽  
Tissue Po2 ◽  
Embryonic Spinal Cord ◽  
Motor Columns ◽  
Spontaneous Fluctuations

A small recessed-tip O2 microelectrode was used to construct frequency distributions of PO2 in the chicken embryonic spinal cord during the last week of development (15–20 days). PO2 was remarkably low and stable at a given spinal locus. Electrode movement led to little change in the absolute level of tissue PO2 for a given day in the development. Spontaneous fluctuations occurred, predominantly in the motor columns, whose frequencies were dependent on the stage of incubation. PO2 decreased progressively; the most significant decline occurred between 16 and 17 days in ovo [19.2 +/- 1.7 (SD) to 11.5 +/- 2.7 Torr, respectively]. This decline in tissue PO2 at 16 days precedes dramatic alterations in spinal cord electrical activity and the resulting embryonic behavior.

scholarly journals Avian marginal zone cells function as primitive streak inducers only after their migration into the hypoblast

Development ◽  
1994 ◽  
Vol 120 (9) ◽  
pp. 2501-2509 ◽  
Author(s):  
H. Eyal-Giladi ◽  
T. Lotan ◽  
T. Levin ◽  
O. Avner ◽  
J. Hochman
Keyword(s):  
Incubation Medium ◽  
Marginal Zone ◽  
Electrophoretic Pattern ◽  
Primitive Streak ◽  
Electrophoretic Analysis ◽  
Avian Embryo ◽  
Central Disc ◽  
Induction Process ◽  
Marginal Zones

Hypoblast cells of posterior marginal zone origin have been shown previously to be the inducers of primitive streak in the avian embryo. Here we checked: (1) whether the above cells acquire their inductivity while still whithin the marginal zone; (2) can inductivity be found in supernatants of defined blastodermic regions; (3) can differences in the electrophoretic pattern be shown between inducing and non-inducing tissue fragments and their conditioned media, which might give a clue as to what the inductive substance is. The following observations were made: 1. (a) Stage X chick posterior marginal zone cells prior to their migration into the hypoblast do not induce a primitive streak, when applied to a stage XIII competent epiblast central disc. (b) A posterior marginal zone fragment, when applied to an epiblast central disc, even after being preincubated for up to 9 hours in vitro, is still non-inductive. (c) Mechanically fragmented stage X posterior marginal zones when applied as a layer to epiblast central discs are non-inductive. (d) Hypoblastic tissue in strip form induces a primitive streak. 2. Competent stage XIII epiblast central discs (chick) were incubated for 2 hours in supernatants of stage XIII epiblasts or hypoblasts. Whereas no inductive effect was exerted by the epiblast supernatant, primitive streaks developed in about 50% of the epiblast central discs incubated in the hypoblast supernatant. 3. Electrophoretic analysis (quails) reveals a protein of 28x10-3 Mr that is enriched in both hypoblastic tissue and its incubation medium and not in the epiblast + marginal zone + area opaca and their incubation medium. These findings suggest a possible correlation between this protein and the induction process.

scholarly journals Vasculogenesis in the early quail blastodisc as studied with a monoclonal antibody recognizing endothelial cells

Development ◽  
1987 ◽  
Vol 100 (2) ◽  
pp. 339-349 ◽  
Author(s):  
L. Pardanaud ◽  
C. Altmann ◽  
P. Kitos ◽  
F. Dieterlen-Lievre ◽  
C.A. Buck
Keyword(s):  
Monoclonal Antibody ◽  
Endothelial Cells ◽  
Single Cells ◽  
Primitive Streak ◽  
Vascular Network ◽  
Vascular Tree ◽  
Somite Stage ◽  
Area Vasculosa ◽  
Haemopoietic Cells ◽  
Area Pellucida

QH1, a monoclonal antibody that recognizes quail endothelial and haemopoietic cells, was applied to quail blastodiscs in toto, in order to analyse by immunofluorescence the emergence of the vascular tree. The first endothelial cells were detected in the area opaca at the headfold stage and in the area pellucida at the 1-somite stage. Single cells then interconnected progressively, especially in the anterior intestinal portal and along the somites building up the linings of the heart and dorsal aortas. This study demonstrates that endothelial cells differentiate as single entities 4 h earlier in development than hitherto detected and that the vascular network forms secondarily. The horseshoe shape of the extraembryonic area vasculosa is also a secondary acquisition. A nonvascularized area persists until later (at least the 14-somite stage) in the region of the regressing primitive streak.

scholarly journals Primitive Streak and Tail Bud Progenitor Populations drive Patterning of the Anteroposterior and Mediolateral Axes

2017 ◽  
Vol 145 ◽  
pp. S82
Author(s):  
Filip Wymeersch ◽  
Stavroula Skylaki ◽  
Yali Huang ◽  
Anestis Tsakiridis ◽  
Constantinos Economou ◽  
...  
Keyword(s):  
Primitive Streak ◽  
Tail Bud

De novo induction of the organizer and formation of the primitive streak in an experimental model of notochord reconstitution in avian embryos

Development ◽  
1998 ◽  
Vol 125 (2) ◽  
pp. 201-213 ◽  
Author(s):  
S. Yuan ◽  
G.C. Schoenwolf
Keyword(s):  
Cell Fate ◽  
De Novo ◽  
Primitive Streak ◽  
Model System ◽  
Floor Plate ◽  
Avian Embryos ◽  
New Information ◽  
Derivatives Of ◽  
Novel Model ◽  
Neurula Stage

We have developed a model system for analyzing reconstitution of the notochord using cultured blastoderm isolates lacking Hensen's node and the primitive streak. Despite lacking normal notochordal precursor cells, the notochord still forms in these isolates during the 36 hours in culture. Reconstitution of the notochord involves an inducer, which acts upon a responder, thereby inducing a reconstituted notochord. To better understand the mechanism of notochord reconstitution, we asked whether formation of the notochord in the model system was preceded by reconstitution of Hensen's node, the organizer of the avian neuraxis. Our results show not only that a functional organizer is reconstituted, but that this organizer is induced from the responder. First, fate mapping reveals that the responder forms a density, morphologically similar to Hensen's node, during the first 10–12 hours in culture, and that this density expresses typical markers of Hensen's node. Second, the density, when fate mapped or when labeled and transplanted in place of Hensen's node, forms typical derivatives of Hensen's node such as endoderm, notochord and the floor plate of the neural tube. Third, the density, when transplanted to an ectopic site, induces a secondary neuraxis, identical to that induced by Hensen's node. And fourth, the density acts as a suppressor of notochord reconstitution, as does Hensen's node, when transplanted to other blastoderm isolates. Our results also reveal that the medial edge of the isolate forms a reconstituted primitive streak, which gives rise to the normal derivatives of the definitive primitive streak along its rostrocaudal extent and which expresses typical streak markers. Finally, our results demonstrate that the notochordal inducer also induces the reconstituted Hensen's node and, therefore, acts like a Nieuwkoop Center. These findings increase our understanding of the mechanism of notochord reconstitution, provide new information and a novel model system for studying the induction of the organizer and reveal the potential of the epiblast to regulate its cell fate and patterns of gene expression during late gastrula/early neurula stage in higher vertebrates.

Mouse Cdx-1 expression during gastrulation

Development ◽  
1993 ◽  
Vol 117 (1) ◽  
pp. 191-203 ◽  
Author(s):  
B.I. Meyer ◽  
P. Gruss
Keyword(s):  
Spinal Cord ◽  
Expression Pattern ◽  
Early Development ◽  
Primitive Streak ◽  
Embryonic Axes ◽  
Specific Expression ◽  
Limb Buds ◽  
Process Formation ◽  
Spinal Cord Level ◽  
Anterior Posterior

We describe the expression pattern of the mouse Cdx-1 gene during early development, examined by both RNA and protein analyses. Cdx-1 expression began with the onset of the head process formation (day 7.5) in ectodermal and mesodermal cells of the primitive streak. Expression extended initially to the middle of the prospective hindbrain and subsequently regressed caudad to the spinal cord level by day 9.5. The mesoderm-specific expression was detected in the first somites and could be followed during their differentiation to the myotome of the dorsal somitic edge by day 12. The developing limb buds and the mesonephros exhibited expression up to day 12. No signal could be detected in notochordal cells and cells of the definitive endoderm. Thus, Cdx-1 is expressed during gastrulation when anterior-posterior positional values are established along the embryonic axes. Furthermore, the expression correlates with the formation of segmented tissue in the posterior hindbrain, the spinal cord and structures like the mesonephros.

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