Mitochondrial defects and hearing loss

The techniques of human molecular genetics have been rapidly applied to the study of hearing loss. These studies have implicated more than 60 loci as causes of nonsyndromic hearing loss. Mutations at more than a dozen nuclear genes have been demonstrated to cause hearing loss, and these have been co vered in recent reviews. However, a perhaps unexpected feature of the molec ular characterization of human hearing loss has been the occurrence of muta tions in the mitochondrial DNA (mtDNA). The importance of mitochondrial fun ction in hearing is emphasized by the recent discovery of mutations in a nu clear-encoded mitochondrial protein which results in hearing loss. This art icle reviews the current status of our knowledge of mtDNA mutations that ha ve been shown to cause hearing loss, and the suggestion of potential molecu lar, cellular and tissue-specific pathophysiological mechanisms by which dy sfunction of mitochondria may lead to a loss of hearing.