Frequency of 35delG mutation in GJB2 gene in non-syndromic prelingual hearing loss in 3 provinces of Iran

Hearing loss is the most common inherited sensory disorder. At least 50% of hearing loss is inherited and about half of the genetic hearing loss is autosomal recessive non-syndromic. Mutations in GJB2 gene is the most frequent cause of autosomal recessive non-syndromic hearing loss. A single 35delG mutation is the most common allelic variant of GJB2 in most parts of the world. The aim of this study was to determine the rate of 35delG mutation in non-syndromic prelingual hearing loss in 3 provinces of Iran. In this descriptive experimental study, 240 cases with autosomal recessive non-syndromic hearing loss in 3 provinces of Iran, including Azarbaijan Sharghi (97 cases), Chaharmahal va Bakhtiari (98 cases) and Gilan (45 cases) were screened for 35delG mutation in the GJB2 gene. Blood samples (5 ml) were taken for genomic DNA extraction. The mutation was screened using Nested-PCR method and the positive results were confirmed by subsequent direct sequencing. Results of this study showed that from 240 studied patients (480 chromosomes), 35delG mutation was found in 58 chromosomes (24 patients were homozygote and 10 patients were heterozygote). The frequency of 35delG mutation was 12.08%, including 18.04% in Azarbaijan Sharghi, 3.06% in Chaharmahal va Bakhtiari and 18.88% in Gilan province. Prevalence of 35delG mutation in Chaharmahal va Bakhtiari population was lower than other provinces studied. These results indicate that the other genes or mutations could result in autosomal recessive non-syndromic hearing loss in Chaharmahal va Bakhtiari population. However, as we found a low rate of 35delG in the populations studied, the cause of deafness remains to be detected in other loci or genes.