Fig. 1. MyoD and Myogenin but not Myf5 are upregulated in neural tissues under the influence of ectopic mouse Myf5 and MyoD, 1 day after electroporation. Adjacent transverse sections, at the forelimb level of embryos electroporated with either mouse Myf5 (A-D) or MyoD (E-H), 1 day after electroporation were hybridised with the DIG-labelled antisense probes for mouse Myf5 (A), MyoD (E), (chick) Myf5 (B,F), (chick) MyoD (C,G) and (chick) Myogenin (D,H). Myf5 is never induced (B,F), although ectopic expression of MyoD (C,G) and Myogenin (D,H) is observed in the neural tube and in neural crest cells, where ectopic mouse Myf5 (A) or MyoD (E) are detected. Ectopic (chick) MyoD is not observed in neural crest cells in G because of the level of the section. Endogenous expression of chick Myf5 (B,F), MyoD (C,G) and Myogenin (D,H) is normally detected in myotomes.