gene in a family with non-syndromic sensorineural hearing impairment

We describe a family with non-syndromic sensorineural hearing impairment inher- ited in a manner consistent with maternal transmission. AVected members were found to have a novel heteroplasmic mtDNA mutation, T7510C, in the tRNA Ser(UCN) gene. This mutation was not found in 661 controls, is well conserved between species, and disrupts base pairing in the acceptor stem of the tRNA, making it the probable cause of hearing impairment in this family. Sequencing of the other mitochondrial tRNA genes did not show any other pathogenic mutations. Four other mutations causing hearing impair- ment have been reported in the tRNA Ser(UCN) gene, two having been shown to aVect tRNA Ser(UCN) levels. With increasing num- bers of reports of mtDNA mutations caus- ing hearing impairment, screening for such mutations should be considered in all cases unless mitochondrial inheritance can be excluded for certain. (J Med Genet 2000;37:692-694)