miR-224 expression in the mouse inner ear sensory epithelia. (A) Schematic diagram of the cochlea and vestibule sensory epithelia (left) and representative miR-224 in situ hybridization (right) of P0 mouse inner ear. In the cochlea, miR-224 is expressed in the hair and supporting cells, as well as in the spiral limbus and the region of the habenula perforate. In the vestibule, expression is detected in the hair cells of the saccule. Scale bar: 20 mm. (B) qRT–PCR analysis of miR-224 in the mouse cochlea sensory epithelia (left panel). miR-224 exhibited higher expression at younger ages, at E16 and P0, and lower expression at P8 in cochlea sensory epithelia. *P < 0.05, whereas the levels were similar at these ages in the vestibule (middle panel). At P0, expression was 33-fold higher in the cochlear than the vestibular sensory epithelia **P < 0.005 (right panel). sv, scala vestibuli; sm, scala media; st, scala tympani; ihc, inner hair cells; ohc, outer hair cells; hc, hair cells; lim, spiral limbus; hp, habenula perforate.