Mutations in the connexin 26 (Cx26) gene at the DFNB1 locus on chromosome 13q12 are associated with autosomal recessive non-syndromic hearing loss (ARNSHL). There are many known mutations in this gene that cause hearing loss. A single frameshift, at position 35 (35delG) accounts for 50% of mutations in the Caucasian population with carrier frequencies of 1.5-2.5%. In this study we investigated the prevalence of Cx26 gene mutations by directly sequencing the coding exon of this gene belonging to ARNSHL individuals from 53 families in Qom and Markazi provinces of Iran. Seven different Cx26 variants were identified. Five Cx26 mutations including 35delG, 233delC, 176del16, W24X, L90P were found in 10 of 53 families (18.87%). One olymorphism V153I was also found. One variant A171T with unknown effects was also detected. Six of the 53 families were observed to have GJB2 mutations in both alleles (11.32%). The most common mutation was 35delG. Three out of 10 families (30%) with GJB2 variants contained 35delG mutation in both alleles and the frequency of 35delG allele was 0.50 among 10 out of 53 families. Also screening for the 342-kb GJB6 deletion mutant did not reveal any large deletion among families studied. Thus, in the two provinces, contribution of GJB2 (Gap Junction Protein Beta 2) mutations to familial deafness appears to be less significant. This necessitates further assessment of the other known genes regions as well as a search for new genetic factors in hereditary deafness in the Iranian population
