[GJB2 235delC single allelic mutation modulates the phenotype associated with the mitochondrial A1555G mutation].

OBJECTIVE: To investigate a non-syndromic deafness family in which potential interaction between the GJB2 gene and a mitochondrial gene appeared to be the cause of hearing impairment. METHODS: Audiological examination was performed by pure-tone audiometry (PTA). Blood samples from 8 members of the pedigree were obtained. DNA was extracted from the leukocytes. The coding region of the GJB2 gene and mitochondrial DNA target fragments were amplified by polymerase chain reaction (PCR). The PCR products were analyzed by sequencing. RESULTS: Direct sequencing showed that the proband had both a heterozygous mutation of 235delC in the GJB2 gene and a mitochondrial 1555 A to G mutation. The proband had profound hearing loss. The maternal relatives had sensorineural hearing loss in the higher frequencies or no hearing loss. CONCLUSION: The GJB2 mutations may be an aggravating factor in the phenotypic expression of the non-syndromic hearing loss associated with the A1555G mitochondrial mutation.