Click here to close
Hello! We notice that you are using Internet Explorer, which is not supported by Xenbase and may cause the site to display incorrectly.
We suggest using a current version of Chrome,
FireFox, or Safari.
???displayArticle.abstract???
The mechanisms involved in the first step of neurogenesis, i.e. neural induction, are poorly understood, particularly in terms of the signalling pathway. In a recent work it has been shown that in urodeles the activation of L-type calcium channels is sufficient to trigger neural induction. In order to substantiate a possible role of this channel in early development in anurans, we have detailed the kinetics of the expression and the localization of the alpha 1 subunit of L-type calcium channel in the early stages of Xenopus laevis embryogenesis using immunological techniques. We observed that the expression of the alpha 1 subunit started during blastulation, where a cytoplasmic labeling was observed. At the onset of gastrulation alpha 1 was targeted to the plasma membrane of the dorsal and the ventralectoderm. Some labeling was found in the mesoderm but never in the endoderm. This expression seems to be general, since similar results have been obtained in anurans (Xenopus) and in urodeles (Pleurodeles). In addition, we found that the alpha 0 subunit of the G(o) protein is expressed simultaneously and strictly colocalized with the alpha 1 subunit of the L-type calcium channel. The role of this channel and its regulation by G(o) protein during early neurogenesis is discussed.
Fig. 1. In situ immunofluores.
cence analysis of MAB 427 on
paraffin-embedded Xenopus
embryo sections. Stage 5
embryos were fixed as previously
described (Levi et al..
1987) and immunohistochemisrry was carried our on 70 jJn1 serial sections.
No labeling was observed in the animal (a) or rhe vegeral (bl half
of the embryo. Bar, 50 jJm.
Fig. 2. Immunohistochemistry on seri.
al sections of a stage 7 embryo. In
stage 7 embryos (treated as for Fig. 1J.
mesectoderm is positIVe. whereas endoderm
is not labeled. (al Ectoderm; (b.cl
marginal zone; (dl endoderm. Bar, 50
jJm.
Fig. 3.lmmunolabeling at stage 10'/4 Stage-l01/4 embryos were treated as
described in Fig. 1. Ectoderm and mesoderm are labeled, whereas endoderm
is negative. There is no difference between the dorsal and ventral sides of
the embryo. (a) Ectoderm; (b) ventral marginal zone; (e) endoderm; (d) dorsal
marginal zone. Note the appearance of the blastopore lip (bl). Bar. 50/..lm.
Fig. 4. Immunocytochemistry on
dissociated cells. Ectoderms were
dissected at the precise stages indicated
and incubated in a Ca2+jMg2+-
free medium before fixing.
Immunodetectlon was carried out
as described. (a) Dissection was
earned out at stage 7. Only part of a
cell is shown. The apparently very
large diameter observed is due to
compression between two covers/
ips dunng the mounting procedure.
Labeling is seen deep in the
cytoplasm (asterisk) and at the plasma
membrane (arrow); (b) ectoderm
dissected at stage 8. No labeling
remains deep in the cytoplasm.
aJ is at the plasma membrane
(arrows) and in the cytoplasm near it
(asterisk); (e) stage 10114(external
layer of ectoderm); (d! stage 10114
(internal/ayer of ectoderm). At this
stage, for both cell layers. labeling is
at the plasma membrane (arrow)
and in the cytoplasm just beneath
{asterisk}. Bar, 50 ~m for a; 25 ;Jm
for b.G and d.
Fig. 5. Colocalization
of a, subunit of L-type
Ca2+ channel and a
subunit of Go protein.
Animal cap of stage 7
(a), stage 8 (bl and
stage 10 Ic) were dissected
and ceffs dissociated
in a Ca2+/Mg2+
free medium before fixing.
Double labeling on
the same cell was carried
out as described in
Experimental procedures.
Left panel: a,
immunolabeling; right
panel: GaD immunolabeling.
Note that the
two different antibodies
labeled the same region
of the plasma membrane.
However some
slight differences may
exit in the colocalization.
Arrowhead in fb)
poinrs to a I positive and
GaD negative domains.
Conversely arrow in (c)
poinrs to aJ negative
and GaD positive
domains_ Bar. 35 pm.
