Fig. 2. Fgf signalling dorsalises the embryo by inhibiting Bmp gene expression. (A-D) Inhibition of Bmp signalling or Fgf overexpression cause dorsalisation phenotypes. Early segmentation stage morphology of wild-type (A), nog1-injected (B), fgf3-injected (C) and fgf24-injected (D) embryos. (E-N) Blastula stage Bmp gene expression is unaffected by inactivation of Bmp proteins, but lost following Fgf overexpression. All embryos are at 30% epiboly. Expression of bmp2b in wild-type (E), nog1-injected (F) and fgf8-injected (G,H) embryos (H is a lateral view of G, dorsal toward the right). (I,J) bmp7 expression in wild-type (I) and fgf8-injected embryos (J). (K,L) bmp4 expression in wild-type (K) and fgf8-injected embryos (L). (M,N) Loss of bmp2b expression following injection of fgf3 (M) or fgf24 (N). (O,P) fgf8 overexpression dorsalises chd-depleted embryos. Characteristic dorsalised morphology (O) and loss of bmp2b expression at blastula stage (P) following co-injection of mo-chd and fgf8 RNA. (Q,S) Ectopic expression of spry4 expression after localised misexpression of RNA encoding Erm1 (Q) or Pea3 (S). (R,T) Local inhibition of bmp2b expression (asterisk) after localised misexpression of RNA encoding Erm1 (R) or Pea3 (T). (A-D,O) Dorsal views, anterior towards the left; (E-G,I-N,P-T) Animal pole views, dorsal towards the right.