Fig. 3. Neural crest cell induction by Sox9 is not dependent on BMP or Wnt signals. Panels show embryos electroporated with Sox9 (A-L) or Wnt3a (M-R) and analysed at the indicated times after transfection; images are oriented with the transfected side of the neural tube to the right. Induction of BMP4 (A-C), BMP7 (D-F) and Wnt1 (G-I) was not detected at any time points examined. Expression of BMP4 (A-C), BMP7 (D-F) and Wnt1 (G-I) was reduced in the dorsal neural tube, which might be a consequence of a change in fate of these cells from neural progenitor to neural crest. (J-L) By contrast, Wnt3a is induced throughout the dorsal/ventral region of the neural tube at 6 hpt (J) and 12 hpt (K) but returns to basal levels by 24 hpt (L). (M-O) Ectopic expression of Wnt3a does not induce HNK-1 expression. (P) Wnt3a transfection increases BrdU incorporation in the ventral neural tube (white bracket). Moreover, CyclinD1 (Q) expression is induced ventrally and expression of the neuronal marker TuJ1 (R) is reduced. The increased proliferation results in deformities on the transfected side of the embryo (blue arrowhead).