ABSTRACT
Various frequencies of the mtDNA mutations have been reported from different population world wild. Three mitochondrial DNA [mtDNA] mutations including A1555G, A 3243G, and A7445G which occurred in MTRNR1, MTTL1 and MTTS1 genes were considered as the main causes of mitochondrial hearing loss in some populations. To determine the frequency of the A1555G, A3243G, and A7445G mutations in nonsyndromic sensorineural hearing loss subjects in Gilan. Forty six subjects with nonsyndromic sensorineural hearing loss were screened by provided questionnaire and audiogram from Gillan Welfare Organization. PCR-RFLP procedure was used in order to presence the MtDNA of A1555GA 3243G and A7445G mutations and was confirmed by subsequent direct sequencing. There was no MtDNA of A1555G, A3243G and A7445G mutation in the cohort study of 46 deaf individuals. Investigation of PCR-RFLP of the MTTL1 gene for existence A3243G mutation lead to identification a G3316A variant that destroyed other restriction site, in the other site of PCR fragment. Our finding indicated that possibility the association of mitochondrial mutations with deafness is very low in deaf subjects in north of Iran. According to existence the G3316A that its pathogenesis in relation to hearing loss phenotype has not stabilized, the frequency of G3316A is 1.46% that can be had highlights role of mitochondrial mutation in deafness