Molecular analysis of mitochondrial DNA A1555G and connexin 26 gene(GJB2) in Chinese Northwest population with nonsyndromic sensorineural hearing loss

OBJECTIVE To investigate the incidence of the mitochondrial DNA 12SrRNA A1555G and connexin 26 gene (GJB2) in Chinese northwest population with nonsyndromic sensorineural hearing loss,and to explore the relationship between mitochondrial DNA A1555G and mutation of GJB2 gene. METHODS Blood samples were obtained from 221 patients with nonsyndromic sensorineural hearing loss in Northwest of China; Genomic DNA was extracted from the isolated leukocytes ; Screening the mitochondrial A1555G mutation by PCR-Alw26l digestion and sequence analysis, PCR and direct sequencing were used to analyze the coding region of GJB2 gene. RESULTS The homoplasmic A1555G mutation was found in 21 individuals of 221 patients,17 of these 21 patients had been treated with aminoglycosides. Eleven different variants of GJB2 were found in all patients ,the disease-causing mutations of GJB2 were 44 individuals in these patients(44/221), The mutation 235delC is found in 54.54 % of all disease-causing mutations ; Among 21 patients with the A1555G mutation, 11 cases were found polymorphic change in GJB2 gene ,only 1 case had V37I heterozygous mutations ,other 9 cases were not found any nucleotide changes of GJB2 gene. CONCLUSION The mtDNA 12SrRNA A1555G mutation has a high incidence in Chinese northwest population with non-syndromic sensorineural hearing loss.The 235delC mutation in the GJB2 gene is most frequent mutations responsible for non-syndromic hearing impairment in this region .It is unlikely that the GJB2 gene is a major modulatory factor for hearing loss due to the A1555G mutation in Chinese population.