Plays a key role to hearing function. Required for normal organization and maintenance of the stereocilia bundle and for mechano-electrical transduction. Detected in inner ear, particularly in hair bundles of auditory hair cells and is enriched in apical stereocilia. Detected in eye, but not in brain or muscle. Expression in the cochlea is stable from late embryonic stages to P12 (the onset of hearing in mice), but thereafter increases. Mice homozygous for an ENU-induced allele exhibit an early-onset, progressive hearing loss, with a lack of fast-graded voltage responses. These mice harbor an early truncating nonsense variant (Trp4Ter). By postnatal days 6 (P6), mutants do not exhibit any gross patterning defects, or differences in the overall number of outer hair cells (OHC) and inner hair cells (IHC) bundles compared to controls. However, despite normal shape organization, these mice shown a progressive reduction in height of the middle and shortest row stereocilia, which is evident first in OHCs by P8, and then later in IHCs at P16. Belongs to the clarin family.