FOXI1 is a member of the FOX family of transcription factors. The FOX family is a large group of proteins (consisting of at least 43 members) that share a common DNA binding domain termed winged-helix or forkhead domain. FOX transcription factors play important roles in development, differentiation, aging and hormone responsiveness. Localizing to the nucleus, FOXI1 functions as a transcription factor. Mice with mutated forms of FOXI1 show defects in ear development, implying that FOXI1 plays a significant role in the developmental pathway of ears and, in particular, the cochlea and vestibulum. FOXI1 is an upstream transcription regulator of Pendrin (a protein associated with deafness), suggesting a role for FOXI1 in the pathogenesis of Pendred syndrome (PS), a condition of nonsyndromic hearing loss and enlarged vestibular aqueduct (EVA).