Close juxtaposition between inducing chordamesoderm and reacting neuroectoderm is a prerequisite for neural induction in Xenopus laevis

1988 ◽  
Vol 24 (1) ◽  
pp. 33-43 ◽  
Author(s):  
Lothar Tacke ◽  
Horst Grunz
Keyword(s):  
Xenopus Laevis ◽  
Neural Induction ◽  
Close Juxtaposition

Expression of N-CAM precedes neural induction in Pleurodeles waltl (urodele, amphibian)

Development ◽  
1989 ◽  
Vol 106 (4) ◽  
pp. 675-683 ◽  
Author(s):  
J.P. Saint-Jeannet ◽  
F. Foulquier ◽  
C. Goridis ◽  
A.M. Duprat
Keyword(s):  
Monoclonal Antibody ◽  
Nervous System ◽  
Xenopus Laevis ◽  
Neural Induction ◽  
Gastrula Stage ◽  
Pleurodeles Waltl ◽  
Early Gastrula

The appearance and localization of N-CAM during neural induction were studied in Pleurodeles waltl embryos and compared with recent contradictory results reported in Xenopus laevis. A monoclonal antibody raised against mouse N-CAM was used. In the nervous system of Pleurodeles, it recognized two glycoproteins of 180 and 140×10(3) M(r) which are the Pleurodeles equivalent of N-CAM-180 and -140. Using this probe for immunohistochemistry and immunocytochemistry, we showed that N-CAM was already expressed in presumptive ectoderm at the early gastrula stage. In late gastrula embryos, a slight increase in staining was observed in the neurectoderm, whereas the labelling persisted in the noninduced ectoderm. When induced ectodermal cells were isolated at the late gastrula stage and cultured in vitro up to 14 days, a faint polarized labelling of cells was observed initially. During differentiation, the staining increased and became progressively restricted to differentiating neurons.

scholarly journals Imaging patterns of calcium transients during neural induction in Xenopus laevis embryos

2000 ◽  
Vol 113 (19) ◽  
pp. 3519-3529 ◽  
Author(s):  
C. Leclerc ◽  
S.E. Webb ◽  
C. Daguzan ◽  
M. Moreau ◽  
A.L. Miller
Keyword(s):  
Xenopus Laevis ◽  
Calcium Signalling ◽  
Neural Induction ◽  
Calcium Transients ◽  
Free Calcium ◽  
Treated Animal ◽  
Cell Stage ◽  
Subsequent Formation ◽  
Xenopus Laevis Embryos

Through the injection of f-aequorin (a calcium-sensitive bioluminescent reporter) into the dorsal micromeres of 8-cell stage Xenopus laevis embryos, and the use of a Photon Imaging Microscope, distinct patterns of calcium signalling were visualised during the gastrulation period. We present results to show that localised domains of elevated calcium were observed exclusively in the anterior dorsal part of the ectoderm, and that these transients increased in number and amplitude between stages 9 to 11, just prior to the onset of neural induction. During this time, however, no increase in cytosolic free calcium was observed in the ventral ectoderm, mesoderm or endoderm. The origin and role of these dorsal calcium-signalling patterns were also investigated. Calcium transients require the presence of functional L-type voltage-sensitive calcium channels. Inhibition of channel activation from stages 8 to 14 with the specific antagonist R(+)BayK 8644 led to a complete inhibition of the calcium transients during gastrulation and resulted in severe defects in the subsequent formation of the anterior nervous system. BayK treatment also led to a reduction in the expression of Zic3 and geminin in whole embryos, and of NCAM in noggin-treated animal caps. The possible role of calcium transients in regulating developmental gene expression is discussed.

Differential gene expression in the anterior neural plate during gastrulation of Xenopus laevis

Development ◽  
1989 ◽  
Vol 105 (4) ◽  
pp. 779-786 ◽  
Author(s):  
M. Jamrich ◽  
S. Sato
Keyword(s):  
Gene Expression ◽  
Xenopus Laevis ◽  
Neural Induction ◽  
Neural Plate ◽  
Cement Gland ◽  
Cdna Clones ◽  
Differential Gene ◽  
Anteroposterior Polarity ◽  
Xenopus Laevis Embryos ◽  
Anterior Neural Plate

We have isolated three cDNA clones that are preferentially expressed in the cement gland of early Xenopus laevis embryos. These clones were used to study processes involved in the induction of this secretory organ. Results obtained show that the induction of this gland coincides with the process of neural induction. Genes specific for the cement gland are expressed very early in the anterior neural plate of stage-12 embryos. This suggests that the anteroposterior polarity of the neural plate is already established during gastrulation. At later stages of development, two of the three genes have secondary sites of expression. The expression of these genes can be induced in isolated animal caps by incubation in 10 mM-NH4Cl, a treatment that is known to induce cement glands.

Neural Induction in the Frog Xenopus laevis

1997 ◽  
pp. 214-219
Author(s):  
Daniel Weinstein ◽  
Chenbei Chang ◽  
Giorgio Lagna ◽  
Atsushi Suzuki ◽  
Paul Wilson ◽  
...  
Keyword(s):  
Xenopus Laevis ◽  
Neural Induction

Neural induction in Xenopus laevis: evidence for the default model

1997 ◽  
Vol 7 (1) ◽  
pp. 7-12 ◽  
Author(s):  
Daniel C Weinstein ◽  
Ali Hemmati-Brivanlou
Keyword(s):  
Xenopus Laevis ◽  
Neural Induction ◽  
Default Model

scholarly journals Dorsalization and neural induction: properties of the organizer in Xenopus laevis

Development ◽  
1983 ◽  
Vol 78 (1) ◽  
pp. 299-317 ◽  
Author(s):  
J. C. Smith ◽  
J. M. W. Slack
Keyword(s):  
Horseradish Peroxidase ◽  
Xenopus Laevis ◽  
Neural Tube ◽  
Marginal Zone ◽  
Neural Induction ◽  
Traditional View ◽  
Posterior Half ◽  
Secondary Embryo ◽  
Graft Tissue ◽  
Host Embryo

We have studied the action of the organizer in Xenopus laevis using grafts labelled with horseradish peroxidase (HRP). Orthotopic grafts of the dorsal marginal zone (the organizer) from an HRP-labelled embryo into an unlabelled host showed that this region contributes to the anterior archenteron wall, to the entire craniocaudal extent of the notochord and to a few cells in the somites. Little or no contribution was made to the neural tube. Orthotopic grafts of the ventral marginal zone (the tissue that responds to a grafted organizer) indicated that it only contributes to the posterior half of the embryo. Within this region it spreads around the entire ventrolateral mesoderm, occasionally contributing a few cells to the somites. The posterior endoderm was also heavily labelled. When the dorsal marginal zone from an HRP-labelled embryo was inserted into a slit cut in the ventral marginal zone of an unlabelled host a mirror-symmetrical double-dorsal duplicated embryo resulted, in which only the notochord and a few cells in the somites of the secondary embryo were derived from the graft. The bulk of the secondary somites was, therefore, derived from host ventral marginal zone tissue which normally makes very little contribution to the somites. This indicates that host ventral marginal zone becomes dorsalized by the graft. The neural tube of the secondary embryo was also unlabelled, showing that it was induced by the influence of the graft on the overlying ectoderm, which normally forms ventral epidermis. We have also grafted ventral marginal zone tissue into a slit cut into the dorsal marginal zone of a host embryo. HRP-labelled tissue was grafted into an unlabelled embryo and vice versa. This graft did not produce a double ventral embryo and this reinforces the traditional view that the dorsal marginal zone is a special signalling region. Instead, the resulting embryos usually had a twinned notochord with the graft tissue in between, differentiated as somite. This confirms that juxtaposing ventral and dorsal marginal zone ‘dorsalizes’ the ventral tissue but does not affect the dorsal tissue which differentiates, as usual, as notochord. Thus, our results allow us to conclude that the organizer mediates two distinct interactions in bringing about the formation of duplicated embryos. The first is dorsalization of adjacent ventral mesoderm and the second is the induction of neuroepithelium from ectoderm overlying the new archenteron roof.

Histological features of neural induction in Xenopus laevis

Development ◽  
1971 ◽  
Vol 26 (3) ◽  
pp. 543-570
Author(s):  
D. Tarin
Keyword(s):  
Xenopus Laevis ◽  
Neural Induction ◽  
Neural Plate ◽  
Paraxial Mesoderm ◽  
Intestinal Tube ◽  
Spinal Cord Regions ◽  
The Central Nervous System ◽  
Dorsal Ectoderm ◽  
Two Stages ◽  
The Brain

It was first established by grafting experiments that neural induction occurs in Xenopus laevis and that it is the mesoderm in the dorsal lip of the blastopore which normally exercises this function. The subsequent histological work provided the following information: At stage 10½ mesodermal invagination was already well under way, in advance of the formation of the archenteric cavity. This confirms the earlier observations of Nieuwkoop & Florschutz(1950). The first evidence of neural induction, thickening of the mid-dorsal ectoderm combined with the development of an inner tier of columnar cells, occurred at stage 11½. By stage 12 there was generalized thickening of the dorsal ectoderm and between stage 12½ and 13 the brain and spinal cord regions of the neural plate became distinguishable. The dorsal mesoderm segregated into notochord rudiment and two lateral masses at stage 13 and the latter further subdivided into paraxial mesoderm and lateral plates by stage 14. The margins of the neural plate were clearly distinguished from presumptive epidermis by stage 15 and the median neural groove was also well marked. In the next two stages the folding of the neural plate in the line of this groove proceeded rapidly. The dorsoventral enlargement of the somites and the relative shrinkage of the notochord were considered to contribute to the mechanism of neurulation. Regionalization of the brain into prosencephalon, mesencephalon and rhombencephalon was in progress at stages 18 and 19. These results indicate that induction consists of an initial activation of dorsal ectoderm (generalized thickening) followed by gradual transformation of the neural plate to form the different parts of the central nervous system (regionalization). Intercellular metachromatic material was noted in various parts of the embryo. This was most plentiful between stage 10½ and stage 13 and thereafter gradually decreased. It was the only feature which persisted long enough to represent a possible inductive agent. At all stages the archenteron was lined with a continuous layer of endoderm. This indicates that the mode of formation of the gastro-intestinal tube in Xenopus is different to that in urodeles. It further implies that the mesoderm is not present on the blastular surface prior to gastrulation but lies in deeper layers.

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