OBJECTIVE: The aim of the study is to assess the frequency of mitochondrial DNA mutations in a cohort of individuals with nonsyndromic sensorineural hearing loss. CLINICAL SETTING: Tertiary care otologic practice SUBJECTS AND METHODS: Individuals with nonsyndromic sensorineural hearing loss were recruited for participation between 2002 and 2008. Genomic DNA was subject to PCR -RFLP analysis for A1555G and A7445G mutation. The primers pairs used for PCR amplification and method analysis of the 12SrRNA A1555G and tRNA Ser (UCN) A7445G mutations were previously described by Prezant et al., and confirming the A7445G mutation was completed by direct sequencing. Mutation A3243G was detected by amplification of base pairs 3163 to 3323 and digestion with ApaI. RESULTS: 350 probands (3 mos - 80 years old) were screened for A1555G, G7444A, and A3243G mtDNA mutations. The frequency of common mitochondrial mutations is 1.4% (5/350) in this cohort including A1555G, G7444A, and A3243G being in four patients with nonsyndromic deafness and one patient with Melas syndrome. CONCLUSIONS: The mitochondrial A1555G mutation (0.6%, 2/350), G7444A (0.6%, 2/350) substitution, and A3243G (0.3%, 1/350) are among the significant causes of ARNSD in this population.
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