Autosomal dominant nonsyndromic hearing impairment

Nearly all genes that have been localized for autosomal dominantly inherite d hearing impairment are characterized by postlingual hearing loss that is progressive in nature. This auditory phenotype is in contrast to that of ge nes localized for autosomal recessive hearing impairment, which generally c ause nonprogressive severe-to-profound or profound prelingual hearing loss. In most cases, ex-tended pedigrees have been used to localize autosomal do minant deafness genes, To date, 22 autosomal dominant loci have been mapped , and 10 of these genes have been cloned. The functions of these deafness-c ausing genes are diverse and include transcription factors, extracellular m atrix components, ion channels, cytoskeletal components, and unknown functi ons. Interesting findings include the unexpected expression pattern of some of these genes and the discovery that in some genes, allele variants can c ause either isolated hearing loss or syndromic deafness. The greatest chall enge for future research will be identifying additional deafness-causing ge nes and elucidating their function in the inner ear. (C) 2000 Wiley-Liss, I nc.