A. In the E18.5 Lmx1a mutant, Fgf10 is strongly expressed in the entire organ of Corti, but more weakly in the vestibular sensory epithelia. B. Mutant Fgf10 expression extends from the greater epithelial ridge (GER) laterally to the inner hair cells in a pattern similar to that of the wildtype. This pattern is the same in the base and the apex. C., D. Fgf8 expression in the base (C) and apex (D) of the mutant. Note expression is confined to the inner hair cells (IHC) in the apex, but scatters among the excess hair cells of the base. F. In the wildtype, Fgf8 expression is neatly confined to the inner hair cells. E. In the E18.5 mutant, Gata3 expression is present in the basal cochlea, but not the saccule. G. Similar Gata3 expression in the wildtype cochlea. Sgl, spiral ganglion; OHC, outer hair cells. Scale bars are 100µm.