Pendrin Expression in the Inner Ear

Pendrin in the inner ear functions as an exchanger of Cl^- and HCO₃^- and thereby may contribute to an elevated endolymphatic HCO₃^- concentration and an elevated endolymphatic pH (Nakaya et al. 2007; Wangemann et al. 2007; Kim and Wangemann 2011). In the mature inner ear, pendrin is expressed in the apical membrane of nonsensory epithelial cells in the cochlea, the vestibular labyrinth, and the endolymphatic sac (Royaux et al. 2003; Wangemann et al. 2004). During development, the earliest expression of pendrin in the inner ear occurs at E11.5 in the endolymphatic sac (Kim and Wangemann 2011). Between E13.5 and E14.5, expression in the endolymphatic sac increases dramatically. At E14.5, virtually all pendrin expression in the inner ear is located in the endolymphatic sac. In the cochlea, the earliest expression of pendrin is found in the hook region at E14.5. The hook region is the most basal part of the cochlea. Between E14.5 and E17.5, pendrin expression expands from the hook region to the lower and then to the upper turn of the cochlea. The onset of pendrin expression in the vestibular labyrinth occurs at E14.5 in the utricle and at E16.5 in the ampullae.