Chordin regulates primitive streak development and the stability of induced neural cells, but is not sufficient for neural induction in the chick embryo

Development ◽  
1998 ◽  
Vol 125 (3) ◽  
pp. 507-519 ◽  
Author(s):  
A. Streit ◽  
K.J. Lee ◽  
I. Woo ◽  
C. Roberts ◽  
T.M. Jessell ◽  
...  
Keyword(s):  
Neural Induction ◽  
Neural Tissue ◽  
Primitive Streak ◽  
Neural Plate ◽  
Neural Cells ◽  
Morphogenetic Protein ◽  
Neural Markers ◽  
Bmp Signalling ◽  
The Stability ◽  
Area Pellucida

We have investigated the role of Bone Morphogenetic Protein 4 (BMP-4) and a BMP antagonist, chordin, in primitive streak formation and neural induction in amniote embryos. We show that both BMP-4 and chordin are expressed before primitive streak formation, and that BMP-4 expression is downregulated as the streak starts to form. When BMP-4 is misexpressed in the posterior area pellucida, primitive streak formation is inhibited. Misexpression of BMP-4 also arrests further development of Hensen's node and axial structures. In contrast, misexpression of chordin in the anterior area pellucida generates an ectopic primitive streak that expresses mesoderm and organizer markers. We also provide evidence that chordin is not sufficient to induce neural tissue in the chick. Misexpression of chordin in regions outside the future neural plate does not induce the early neural markers L5, Sox-3 or Sox-2. Furthermore, neither BMP-4 nor BMP-7 interfere with neural induction when misexpressed in the presumptive neural plate before or after primitive streak formation. However, chordin can stabilise the expression of early neural markers in cells that have already received neural inducing signals. These results suggest that the regulation of BMP signalling by chordin plays a role in primitive streak formation and that chordin is not sufficient to induce neural tissue.

scholarly journals Experiments on the Development of the Head of the Chick Embryo

1936 ◽  
Vol 13 (2) ◽  
pp. 219-236
Author(s):  
C. H. WADDINGTON ◽  
A. COHEN
Keyword(s):  
Thin Sheet ◽  
Neural Tissue ◽  
Primitive Streak ◽  
Neural Plate ◽  
Head Region ◽  
Process Stage ◽  
Optic Vesicles ◽  
Lens Formation ◽  
Embryonic Ectoderm

1. Experiments were made on the development of the head of chicken embryos cultivated in vitro. 2. Defects in the presumptive head region of primitive streak embryos are regulated completely if the wound fills up before the histogenesis of neural tissue begins in the head-process stage. Different methods by which the hole is filled are described. 3. No repair occurs in the head-process and head-fold stages, and in this period two masses of neural tissue cannot heal together. 4. Median defects, even if repaired as regards neural tissue, cause a failure of the ventral closure of the foregut. The lateral evaginations of the gut develop typically in atypical situations. The headfold may break through and join up with the endoderm in such a way that the gut acquires an anterior opening. 5. The paired heart rudiments may develop separately. The separate vesicles begin to contract at a time appropriate to the development of the embryo as a whole. The two hearts are mirror images, the left one having the normal curvature, but the embryos do not survive long enough for the hearts to acquire a very definite shape. 6. The forebrain has a considerable capacity for repair in the early somite stages (five to twenty-five somites). One-half of the forebrain can remodel itself into a complete forebrain. In some cases the neural plate and epidermis grow together over the wound, in others the epidermis and mesenchyme make the first covering, leaving a space along the inside of which the neural tissue grows. The neural tissue may become a very thin sheet. 7. The repaired forebrain may induce the formation of a nasal placode from the non-presumptive nasal epidermis which covers the wound. 8. If the optic vesicle is entirely removed, a new one is not formed, but parts of the vesicle can regulate to complete eye-cups, either when still attached to the forebrain or after being isolated in the extra-embryonic regions of another embryo. 9. Injured optic vesicles induce lenses from the non-presumptive epidermis which grows over the wound. Transplanted optic neural tissue from embryos of about five somites induces the formation of lentoids from extra-embryonic ectoderm, but only in a small proportion of cases. 10. The presumptive lens epidermis can produce a slight thickening even when contact with the optic cup is prevented. 11. The significance of periods of minimum regulatory power for the concept of determination is discussed. 12. The data concerning lens formation are discussed in terms of the field concept.

Early posterior neural tissue is induced by FGF in the chick embryo

Development ◽  
1998 ◽  
Vol 125 (3) ◽  
pp. 473-484 ◽  
Author(s):  
K.G. Storey ◽  
A. Goriely ◽  
C.M. Sargent ◽  
J.M. Brown ◽  
H.D. Burns ◽  
...  
Keyword(s):  
Chick Embryo ◽  
Cell Fate ◽  
Neural Induction ◽  
Neural Tissue ◽  
Primitive Streak ◽  
Specific Aspect ◽  
Amphibian Embryo ◽  
Fgf Signalling ◽  
Unique Cell ◽  
Neural Cell Fate

Signals that induce neural cell fate in amniote embryos emanate from a unique cell population found at the anterior end of the primitive streak. Cells in this region express a number of fibroblast growth factors (FGFs), a group of secreted proteins implicated in the induction and patterning of neural tissue in the amphibian embryo. Here we exploit the large size and accessibility of the early chick embryo to analyse the function of FGF signalling specifically during neural induction. Our results demonstrate that extraembryonic epiblast cells previously shown to be responsive to endogenous neural-inducing signals express early posterior neural genes in response to local, physiological levels of FGF signal. This neural tissue does not express anterior neural markers or undergo neuronal differentiation and forms in the absence of axial mesoderm. Prospective mesodermal tissue is, however, induced and we present evidence for both the direct and indirect action of FGFs on prospective posterior neural tissue. These findings suggest that FGF signalling underlies a specific aspect of neural induction, the initiation of the programme that leads to the generation of the posterior central nervous system.

scholarly journals XASH genes promote neurogenesis in Xenopus embryos

Development ◽  
1994 ◽  
Vol 120 (12) ◽  
pp. 3649-3655 ◽  
Author(s):  
B. Ferreiro ◽  
C. Kintner ◽  
K. Zimmerman ◽  
D. Anderson ◽  
W.A. Harris
Keyword(s):  
Neural Development ◽  
Neural Induction ◽  
Neural Tissue ◽  
Neural Plate ◽  
Binding Partner ◽  
Helix Loop Helix ◽  
Neural Genes ◽  
Dorsal Ectoderm ◽  
Bhlh Transcription Factors ◽  
Beta Tubulin Gene

Neural development in Drosophila is promoted by a family of basic helix-loop-helix (bHLH) transcription factors encoded within the Achaete Scute-Complex (AS-C). XASH-3, a Xenopus homolog of the Drosophila AS-C genes, is expressed during neural induction within a portion of the dorsal ectoderm that gives rise to the neural plate and tube. Here, we show that XASH-3, when expressed with the promiscuous binding partner XE12, specifically activates the expression of neural genes in naive ectoderm, suggesting that XASH-3 promotes neural development. Moreover, XASH-3/XE12 RNA injections into embryos lead to hypertrophy of the neural tube. Interestingly, XASH-3 misexpression does not lead to the formation of ectopic neural tissue in ventral regions, suggesting that the domain of XASH proneural function is restricted in the embryo. In contrast to the neural inducer noggin, which permanently activates the NCAM gene, the activation of neural genes by XASH-3/XE12 is not stable in naive ectoderm, yet XASH-3/XE12 powerfully and stably activates NCAM, Neurofilament and type III beta-tubulin gene expression in noggin-treated ectoderm. These results show that the XASH-3 promotes neural development, and suggest that its activity depends on additional factors which are induced in ectoderm by factors such as noggin.

Timing and cell interactions underlying neural induction in the chick embryo

Development ◽  
1999 ◽  
Vol 126 (11) ◽  
pp. 2505-2514
Author(s):  
D.K. Darnell ◽  
M.R. Stark ◽  
G.C. Schoenwolf
Keyword(s):  
Neural Induction ◽  
Primitive Streak ◽  
Model System ◽  
Neural Plate ◽  
Neural Specification ◽  
Organizer Activity ◽  
Plate Morphology ◽  
Improved Model ◽  
Differentiation Event ◽  
Early Gastrula

Previous studies on neural induction have identified regionally localized inducing activities, signaling molecules, potential competence factors and various other features of this important, early differentiation event. In this paper, we have developed an improved model system for analyzing neural induction and patterning using transverse blastoderm isolates obtained from gastrulating chick embryos. We use this model to establish the timing of neural specification and the spatial distribution of perinodal cells having organizer activity. We show that a tissue that acts either as an organizer or as an inducer of an organizer is spatially co-localized with the prospective neuroectoderm immediately rostral to the primitive streak in the early gastrula. As the primitive streak elongates, this tissue with organizing activity and the prospective neuroectoderm rostral to the streak separate. Furthermore, we show that up to and through the mid-primitive streak stage (i.e., stage 3c/3+), the prospective neuroectoderm cannot self-differentiate (i.e., express neural markers and acquire neural plate morphology) in isolation from tissue with organizer activity. Signals from the organizer and from other more caudal regions of the primitive streak act on the rostral prospective neuroectoderm and the latter gains potency (i.e., is specified) by the fully elongated primitive streak stage (i.e., stage 3d). Transverse blastoderm isolates containing non-specified, prospective neuroectoderm provide an improved model system for analyzing early signaling events involved in neuraxis initiation and patterning.

scholarly journals Trpc1 as the Missing Link Between the Bmp and Ca2+ Signalling Pathways During Neural Specification in Amphibians

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Isabelle Néant ◽  
Ho Chi Leung ◽  
Sarah E. Webb ◽  
Andrew L. Miller ◽  
Marc Moreau ◽  
...  
Keyword(s):  
Transient Receptor Potential ◽  
Neural Induction ◽  
Receptor Potential ◽  
Physical Interaction ◽  
Morphogenetic Protein ◽  
Voltage Dependent ◽  
Neural Specification ◽  
Trpc1 Channels ◽  
Bmp Signalling ◽  
Transient Receptor

Abstract In amphibians, the inhibition of bone morphogenetic protein (BMP) in the dorsal ectoderm has been proposed to be responsible for the first step of neural specification, called neural induction. We previously demonstrated that in Xenopus laevis embryos, the BMP signalling antagonist, noggin, triggers an influx of Ca2+ through voltage-dependent L-type Ca2+ channels (LTCCs), mainly via CaV1.2, and we showed that this influx constitutes a necessary and sufficient signal for triggering the expression of neural genes. However, the mechanism linking the inhibition of BMP signalling with the activation of LTCCs remained unknown. Here, we demonstrate that the transient receptor potential canonical subfamily member 1, (Trpc1), is an intermediate between BMP receptor type II (BMPRII) and the CaV1.2 channel. We show that noggin induces a physical interaction between BMPRII and Trpc1 channels. This interaction leads to the activation of Trpc1 channels and to an influx of cations, which depolarizes the plasma membrane up to a threshold sufficient to activate Cav1.2. Together, our results demonstrate for the first time that during neural induction, Ca2+ entry through the CaV1.2 channel results from the noggin-induced interaction between Trpc1 and BMPRII.

scholarly journals The Behaviour of Epiblast Grafts Beneath the Primitive Streak of the Chick

1937 ◽  
Vol 14 (3) ◽  
pp. 302-318
Author(s):  
M. ABERCROMBIE
Keyword(s):  
Neural Induction ◽  
Neural Tissue ◽  
Primitive Streak ◽  
Active Movement ◽  
Side Plate ◽  
Long Time ◽  
Epithelial Structure ◽  
Break Up ◽  
High Degree

1. Grafts consisting of area opaca ectoderm, presumptive epidermis, presumptive neural tissue, or presumptive mesoderm (axial or side-plate), were transplanted to a position immediately under the primitive streak of chick blastoderms in the primitive streak stage. 2. The grafts, though they sometimes remained as a non-neural epithelium, were usually neurally induced, contemporaneously and co-extensively with the neural induction of the host. The graft-derived neural tissue is often much thicker than the host neural tissue, and though usually forming an autonomous structure, it is frequently arranged with a high degree of symmetry relative to the host. If, however, the graft remains for a long time uninduced, lying in the host mesenchyme, it tends to break up into mesenchyme itself. 3. It is probable that all parts of the epiblast, whatever their presumptive fate, are competent to form neural tissue, provided their epithelial structure is maintained; and it is notable that this is true of presumptive mesoderm. 4. The dorso-ventral polarity of the grafts is maintained whatever their orientation in the host; but the irreversible determination of this polarity was probably not tested. The antero-posterior polarity of the grafts was without effect on their differentiation. 5. An elongation of the graft along the antero-posterior axis of the host usually occurred. It was often very marked, and generally consisted in the posterior end of the graft accompanying the host primitive node as it moved backwards. It is believed to be due to the induction of an active movement in the graft itself. 6. The host is considerably modified by the presence of the graft. In particular, the head-fold is usually suppressed. The formation of the foregut is frequently upset, but the closed foregut shows a considerable power of regulation.

scholarly journals Fgf/Ets signalling in Xenopus ectoderm initiates neural induction and patterning in an autonomous and paracrine manners

2020 ◽  
Author(s):  
Ikuko Hongo ◽  
Harumasa Okamoto
Keyword(s):  
Neural Development ◽  
Neural Induction ◽  
Dominant Negative ◽  
Neural Patterning ◽  
Paracrine Signalling ◽  
Neural Genes ◽  
Morphogenetic Protein ◽  
Bmp Signalling

ABSTRACTFibroblast growth factor (Fgf) and anti-bone morphogenetic protein (Bmp) signals are derived from the organiser of mesoderm origin and cooperate to promote Xenopus neural development from the gastrula ectoderm. Using antisense oligos to Fgf2 and Fgf8 and dominant-negative Ets transcription factors, we showed that the expression of Fgf2, Fgf8, and Ets in ectoderm cells is essential to initiate neural induction both in vivo and in vitro. Our findings show that neural induction is initiated primarily by autonomous signalling in ectoderm cells, rather than by paracrine signalling from organiser cells. The signalling in ectoderm cells is transduced via the Fgf/Ras/Mapk/Ets pathway, independent of Bmp signal inhibition via the Fgf/Ras/Mapk/Smad1 route, as indicated by earlier studies. Through the same pathway, Fgfs activated position-specific neural genes dose-dependently along the anteroposterior axis in cultured ectoderm cells. The expression of these genes coincides with the establishment of the activated Ets gradient within the gastrula ectoderm. Organiser cells, being located posteriorly to the ectoderm, secrete Fgfs as gastrulation proceeds, which among several candidate molecules initially promote neural patterning of the induced neuroectoderm as morphogens.Summary statementFgf/Ets signalling in ectodermal cells is required to initiate the expression of both anterior and posterior neural genes from the late blastula to gastrula stages, independent of anti-Bmp signalling.

A role for HGF/SF in neural induction and its expression in Hensen's node during gastrulation

Development ◽  
1995 ◽  
Vol 121 (3) ◽  
pp. 813-824 ◽  
Author(s):  
A. Streit ◽  
C.D. Stern ◽  
C. Thery ◽  
G.W. Ireland ◽  
S. Aparicio ◽  
...  
Keyword(s):  
Neural Induction ◽  
Primitive Streak ◽  
Neural Plate ◽  
Neuronal Morphology ◽  
Collagen Gels ◽  
Scatter Factor ◽  
Neuronal Markers ◽  
Hepatocyte Growth ◽  
Overnight Culture

It was previously shown (Roberts, C., Platt, N., Streit, A., Schachner, M. and Stern, C. D. (1991) Development 112, 959–970) that grafts of Hensen's node into chick embryos enhanced and maintain expression of the L5 carbohydrate in neighbouring epiblast cells, and that antibodies against L5 inhibit neural induction by such a graft. We now show that L5 is initially widely expressed in the epiblast, but as neural induction proceeds it gradually becomes confined to and up-regulated in the early neural plate. L5 can therefore be considered as a marker for cells that are competent to respond to neural induction. We also show that Hepatocyte Growth Factor/Scatter Factor (HGF/SF) promotes the expression of L5 by extraembryonic epiblast in collagen gels after overnight culture. Explants cultured for several days in the presence of HGF/SF, as well as explants of prospective neural plate, can differentiate into cells with neuronal morphology expressing neuronal markers. To investigate whether HGF/SF is expressed in the chick embryo at appropriate stages of development, we produced specific cDNA probes and used them for in situ hybridization. We find that at the primitive streak stage, HGF/SF is expressed specifically in Hensen's node. We therefore propose that HGF/SF plays a role during the early steps of neural induction, perhaps by inducing or maintaining the competence of the epiblast to respond to neural inducing signals.

Neural induction and regionalisation by different subpopulations of cells in Hensen's node

Development ◽  
1995 ◽  
Vol 121 (2) ◽  
pp. 417-428 ◽  
Author(s):  
K.G. Storey ◽  
M.A. Selleck ◽  
C.D. Stern
Keyword(s):  
Chick Embryo ◽  
Cell Lineage ◽  
Neural Induction ◽  
Neural Tissue ◽  
Cell Types ◽  
Neural Cells ◽  
Cell Type ◽  
Prechordal Plate ◽  
Gut Endoderm ◽  
Lineage Analysis

Cell lineage analysis has revealed that the amniote organizer, Hensen's node, is subdivided into distinct regions, each containing a characteristic subpopulation of cells with defined fates. Here, we address the question of whether the inducing and regionalising ability of Hensen's node is associated with a specific subpopulation. Quail explants from Hensen's node are grafted into an extraembryonic site in a host chick embryo allowing host- and donor-derived cells to be distinguished. Cell-type- and region-specific markers are used to assess the fates of the mesodermal and neural cells that develop. We find that neural inducing ability is localised in the epiblast layer and the mesendoderm (deep portion) of the medial sector of the node. The deep portion of the posterolateral part of the node does not have neural inducing ability. Neural induction also correlates with the presence of particular prospective cell types in our grafts: chordamesoderm (notochord/head process), definitive (gut) endoderm or neural tissue. However, only grafts that include the epiblast layer of the node induce neural tissue expressing a complete range of anteroposterior characteristics, although prospective prechordal plate cells may also play a role in specification of the forebrain.

Directing Axonal Growth: A Review on the Fabrication of Fibrous Scaffolds That Promotes the Orientation of Axons

Gels ◽  
2021 ◽  
Vol 8 (1) ◽  
pp. 25
Author(s):  
Devindraan Sirkkunan ◽  
Belinda Pingguan-Murphy ◽  
Farina Muhamad
Keyword(s):  
Tissue Engineering ◽  
Extracellular Matrix ◽  
Neuronal Cells ◽  
Neural Tissue ◽  
Axonal Growth ◽  
Structural Proteins ◽  
Neural Cells ◽  
Neural Tissue Engineering ◽  
Fibrous Scaffolds ◽  
Specialized Function

Tissues are commonly defined as groups of cells that have similar structure and uniformly perform a specialized function. A lesser-known fact is that the placement of these cells within these tissues plays an important role in executing its functions, especially for neuronal cells. Hence, the design of a functional neural scaffold has to mirror these cell organizations, which are brought about by the configuration of natural extracellular matrix (ECM) structural proteins. In this review, we will briefly discuss the various characteristics considered when making neural scaffolds. We will then focus on the cellular orientation and axonal alignment of neural cells within their ECM and elaborate on the mechanisms involved in this process. A better understanding of these mechanisms could shed more light onto the rationale of fabricating the scaffolds for this specific functionality. Finally, we will discuss the scaffolds used in neural tissue engineering (NTE) and the methods used to fabricate these well-defined constructs.

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