Fig. 2. Inhibition of Wnt or Fgf signaling pathway blocks Sox9 expression in the otic placode/vesicle. (A) Sox9 expression is lost in the otic placode (upper panels, stage 17) of embryos injected with 1ng of GSK3ß mRNA (arrows, injected side). Sox9 expression is reduced in the otic vesicle (lower panels, stage 23) of embryos injected with 1 ng of dominant-negative FgfR (XFD) mRNA (arrows, injected side). For comparison, normal expression of Sox9 is shown on the uninjected side of these embryos (arrows, uninjected side) at stage 17 and stage 23. As Fgf signaling is also required for development of posterior structures, XFD/FgfR-injected present a characteristic open blastopore (lower panels). All panels are lateral views, anterior towards the right (left panels) or anterior towards the left (right panels). (B) Transverse section through an embryo injected with GSK3ß (upper panel) or XFD/FgfR (lower panel) mRNA. In both cases the embryos present a reduced otic vesicle on the injected side (left side, arrows). br, brain; no, notochord; ov, otic vesicle.