Study of frequency and spectrum of GJB2 gene mutations in non-syndromic hearing loss patients of Semnan province

Abstract Background and aim: The frequency of hearing impairment is one out of 500 newborn babies, worldwide. However, in Iran, due to the high prevalence of consanguineous marriages, this amount is estimated to be two to three times higher. So far, more than 120 genes causing non-syndromic Hearing loss (NSHL) have been identified in the world, of which GJB2 gene mutations are the most common cause of autosomal recessive NSHL. The aim of this study is to investigate the frequency and spectrum of GJB2 gene mutations in the deaf population of Semnan province. Methods: 50 patients with non-syndromic hearing loss from 50 unrelated families were investigated. First, the most common mutation 35delG was screened by ASPCR (Allele-Specific Polymerase Chain Reaction). Then, in order to identify other mutations of the GJB2 gene, patients who were negative or heterozygous for the 35delG mutation were analyzed by Sanger sequencing for all exonic regions and splicing sites of the GJB2 gene. Results: In this research, 100 chromosomes (50 patients) were examined. 12 chromosomes (12%) showed mutations in GJB2 gene. Among these, the contribution of each of the identified mutations 35delG, IVS1+1G>A and c.94C>T:p.Arg32Cys in the deaf population of Semnan province is 7%, 4% and 1%, respectively. Thus, the common mutation 35delG includes 58.34% of all identified mutations. Conclusion: In general, the results of this study showed that GJB2 gene mutations include only 12% of mutations causing hearing loss in the deaf population of Semnan province, emphasizing the importance of using next generation sequencing techniques to identify other genes causing hereditary hearing impairment in this population. Such an approach will significantly help in carrying out genetic counseling, prenatal diagnosis and clinical management of hearing impairment in Semnan province.