Fig. 6. Fgf3 and Fgf8 signaling together is required for otic expression of sox9a but not sox9b or dlx3b. (A-D) Cells of the presumptive otic placodes express sox9a in wild-type embryos (A), at somewhat reduced levels after fgf3-MO injection (B), at more reduced levels in fgf8^– mutant embryos (C) and at undetectable levels in fgf8^– embryos injected with fgf3-MO (D; n=8). (E-H) Cells of the presumptive otic area and cranial neural crest (Li et al., 2002) express sox9b in wild-type embryos (E) and fgf3-MO injected embryos (F). Expression of sox9b in the otic region is slightly reduced in fgf8^– embryos (G) and more significantly reduced, although not completely eliminated, in fgf8^– embryos injected with fgf3-MO (H; n=10). sox9b expression in cranial crest is apparently unaffected by reduced fgf3 and fgf8 expression. (I-L) Otic expression of dlx3b is much less affected by reduction of Fgf signaling (n=16). Similar results were obtained for dlx4b (not shown). Expression of egr2 (krox20) in red indicates the locations of rhombomeres 3 and 5. Four-somite stage. Dorsal views, anterior towards the left. Scale bar: 110 µm.