Pendrin knockout mice show profound deafness and marked inner ear malformations [49,55] that, however, are not considered the direct cause of hearing loss, which is rather thought to be the result of acidification of the cochlear endolymph, the consequent loss of endocochlear potential, and elevation of endolymphatic Ca2+ concentration, ultimately leading to degeneration of sensory hair cells in the organ of Corti [49]. The gene discussed is SLC26A4; the disease is deafness.