Kinocilin (KNCN)

Kinocilin has an N-terminal signal peptide and 2 transmembrane domains, but no significant homology to other known proteins. Northern blot and RT-PCR analysis detected expression in mouse inner ear, testis, kidney, liver, heart, with lower expression in brain, lung, and eye. Immunofluorescence and immunoelectron microscopy localized Kncn protein in the kinocilia of sensory cells of the inner ear. Expression was first observed in the kinocilia of vestibular hair cells and auditory hair cells at embryonic day 14.5 and 18.5, respectively. During postnatal development, when the auditory hair cells began to lose kinocilia, kinocilin was redistributed in a belt-like pattern at the apex of these cells, where it colocalized with the tubulin belt. In mature auditory hair cells, kinocilin was present in the cuticular plate at the base of the stereocilia.