Fig. 1. pRb expression in hair cells of the inner ear. pRb immunostaining; Rb in situ hybridization. (A,B) pRb staining in the early- and later-differentiating HCs of the embryonic saccule. (C,D) pRb and Rb expressions in HCs of the late-embryonic utricle. (E) A subpopulation of HCs is pRb-positive in the adult utricle. (F,G) pRb expression in inner and outer HCs of the cochlea at birth and early postnatal life. In addition to HCs, the greater epithelial ridge shows weak expression at birth. (H) In the mature organ of Corti, pRb expression is detected only in inner HCs. Supporting cells are negative at all stages. (I,J) pRb is not expressed in the hyperplastic sensory epithelium of utricle and cochlea of mgRb:Rb^-/- mutants at E18.5. Abbreviations: wt, wild type; sac, saccule; ut, utricle; co, cochlea; IHC, inner hair cell; OHCs, outer hair cells; GER, greater epithelial ridge; HCs, hair cells; SCs, supporting cells. Arrows in G,H,J indicate HCs. Scale bar: 70 µm.