A., B. Sox2 expression is similar, but broader in the mutant without a distinct gap between posterior and anterior prosensory patch expression (asterisk in A,B and lower mag. insets). C.-E. At E11.5 wildtype expression is localizing to individual sensory epithelia (Note separate AC and HC), while in the mutant the AC and HC are joined. Note also the PC/PN extending ventrally toward the cochlea (arrows in D, E, G, I). F,G. By E14.5 the wildtype sensory epithelia are clearly segregated (by Lmx1a expressing epithelia – compare Fig. 8H.), while continuities and near continuities are apparent in the mutant. H. In the E18.5 wildtype cochlea, Sox2 expression is most intense in the inner pillar cells. I. Mutant Sox2 expression identifies the fused U-S-C and enlarged PC-PN. J., K. At E18.5, Sox2 expression in the mutant cochlear base is broad and diffuse, while that in the apex (K.) is, like the wildtype, focused on the inner pillar cells (P). All whole ears oriented as in A. Scale bars are 100 µm in A–G and 50 µm in H–K.