Fig. 4. Sox9 depletion prevents expression of late otic vesicle markers. (A) Schematic representation of the expression pattern (purple color) of four markers genes expressed in the epithelium of the otic vesicle at stage 35. Tbx2 is expressed through out the entire otic vesicle. Bmp4 expression is restricted to the anterior and posterior region of the otic vesicle. Wnt3a and Otx2 are expressed at the dorsal and ventral aspect of the otic vesicle, respectively. d, dorsal; v, ventral; a, anterior; p, posterior. (B) Tbx2, Bmp4, Wnt3a and Otx2 expression is lost in the otic vesicle of embryos injected with 2 ng of Sox9-mo in one blastomere at the eight-cell stage (arrows, injected side). RNA encoding the lineage tracer ß-galactosidase was co-injected with the oligo AS to identify the injected side (red staining). For comparison, normal expression of Tbx2, Bmp4, Wnt3a and Otx2 is shown on the uninjected side of these embryos (arrows, control side). (C,D) Transverse section through an embryo injected with 2 ng of Sox9-mo. On the injected side (left side, arrow), the otic vesicle fails to form. br, brain; no, notochord; ov, otic vesicle.