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Fig. 4. Floor plate and neuronal induction assays. Normal (A) and
ectopic (B) expression of HNF-3b protein in control uninjected (A)
and Gli1-injected (B) approx. stage 34 tadpoles. The embryo shown
in B is an example of the floor-plate-induction assay used in this
study (see Lee et al., 1997; Ruiz i Altaba, 1998). Arrows in B point
to sites of ectopic expression anterior and dorsal to the floor plate
(fp). The panels show side views of cleared whole-mount-labeled
specimens with anterior to the top in A and to the left in B.
(C-F) Ectopic neurogenesis marked by the ectopic expression of Ntubulin
in neurulae (approx. stage 14) injected unilaterally with Gli2
(C), NLSGli2 (D), Gli3 (E) of an N-terminal deletion of Gli3. In (F),
N-tub expression is restricted ventrally. (C) Dorsal view with anterior
end to the top. Endogenous labeling in primary neuronal stripes is
evident in the non-injected sides. (D,E) Dorso-lateral views with
anterior end to the top. (F) Ventral views. Arrows point to sites of
ectopic expression and the myc label depicts the localization of Myctagged
Gli proteins, coincident with the sites of ectopic N-tub
expression. (G,H) Gli3C¢æCla (H), but not Gli1C¢æPstI (G), inhibits
ectopic and endogenous neurogenesis. The region inheriting the
injected protein is labeled (myc) and arrows in H point to absence of
N-tub expression in the injected side. The motor neuron (m),
interneuron (i) and sensory neuron (s) stripes are identified. Dashed
lines depict axes of bilateral symmetry. |
