Id2/3 activity inhibits Myf5-induced myogenesis and upregulates FoxC2 transcription. (A) Electroporation of control GFP into the presumptive lateral DM at E2. At 16 hours post-treatment, labeled cells are still confined to the DM epithelium (N = 3). (B) Missexpression of Myf5 induces premature fiber formation (arrows) (N = 3). Co-treatment of Myf5 with Id2 (C, N = 3) or Id3 (D, N = 6) prevents Myf5-induced myogenesis and cells appear scattered instead of epithelial. (E-G) shows 12 hours of control-GFP (E, N = 6), Id2 (F, N = 9) or Id3 (G, N = 7) missexpression in the central DM (left panels). Id2 or Id3 induce transcription of FoxC2 compared to the contralateral sides and to control-GFP. (H-I) Myf5 does not affect FoxC2 transcription. Control-GFP (H, N = 2) or Myf5 (I, N = 13) for 12 hours did not affect transcription of FoxC2 in the lateral DM. Bar: (E-G) 25 μm; (H) 40 μm; (I) 50 μm. DM, dermomyotome; EP, electroporation; NT, neural tube.