Inherited hearing impairment is a highly heterogeneous genetic trait. To date, 22 and 27 genes have been associated with autosomal dominant and recessive non-syndromic hearing loss, respectively (ADNHSL, ARNSHL)(1). Mutations in seven of these genes–GJB2, GJB3, GJB6, MYO6, MYO7A, COL11A2 and TMC1–cause both ADNSHL and ARNSHL.

TMC1 belongs to a large TMC (Trans Membrane Channel-like) gene family. Its eight members encode transmembrane proteins with intracellular amino-and carboxyl-termini and multiple transmembrane domains. In the inner ear, murine Tmc1 is expressed in outer and inner hair cells after P3. Tmc1 deficiency in the recessive deafness mouse mutant dn leads to complete deafness and hair cell degeneration, while the Tmc1 p. M412K missense mutation in the semidominant Bth mutant causes progressive hearing loss and hair cell degeneration in heterozygotes and early-onset deafness in homozygotes (2, 3). These data suggest that Tmc1 is necessary for maturation and survival of hair cells in the murine cochlea (4).