Mitochondrial deafness mutations reviewed

The first molecular defect for nonsyndromic hearing loss was identified in 1993, and was a mito chondrial mutation. Since then a number of inherited m itochondrial DNA (mtDNA) mutations have been implicated in hearing loss, an d acquired mtDNA mutations have been proposed as one of the causes of the h earing loss associated with aging, presbyacusis. These molecular findings h ave raised as many questions as they have answered, however, since the path ophysiology between the mutations and the clinical phenotype remains poorly understood. This mini-review will, after a short background review of mito chondrial genetics, (1) outline the different mtDNA mutations associated wi th inherited syndromic, nonsyndromic, and ototoxic hearing loss, (2) summar ize the data on acquired mtDNA mutations and their possible association wit h presbyacusis, (3) describe the biochemical consequences of the inherited mtDNA mutations, (4) suggest the clinical implications of the identificatio n of these mutations, and (5) discuss the penetrance and tissue specificity of the hearing associated mtDNA mutations. Hum Mutat 13:261-270, 1999. (C) 1999 Wiley Liss, Inc.