GJB2 mutations in Turkish patients with nonsyndromic hearing loss

Abstract

AimMutations in the GJB2 gene are the most common cause of non-syndromic recessive hearing loss all around the world. We aim to describe the genotype distributions and auditory phenotype of Turkish patients with congenital hearing loss in the east of Turkey. Materials and methodsWe screened DNA samples of 56 unrelated patients with autosomal recessive non-syndromic hearing loss. All patients and members of their families were screened for the GJB2 mutations as well as the specific point mutations in the GJB2 gene (splice site mutation, c.-23+1G>A, alternatively called IVS1+1G>A, rs80338940), and m.1555A>G in the MT-RNR1 gene (rs267606617, 12SrRNA) of mitochondrial DNA. Samples of these patients were studied with the Sanger sequencing method upon being screened for prevalent variants of GJB2 with chip-based single nucleotide polymorphism genotyping platforms, as the first step of genetic analysis. We analyzed audiograms of these patients to characterize the audiological features of the GJB2 deafness. ResultsA total of 21.4% of these deaf probands had biallelic GJB2 mutations (either homozygous or compound heterozygous mutations). Five different mutations and two polymorphisms were found in 17 of the patients with severe to profound hearing loss. The c.35delG mutation was the most common mutation that was found in 13.4% of all mutant GJB2 alleles. The c.71G>A, c.358-360delGAG, c.551G>C and a novel mutation, c.327-328delGGinsA were identified. In our study, all patients and members of their families were screened for specific point mutations (splice site mutation c.23+1G>A), m.1555A>G, and it was found that none of them carried these mutations. ConclusionOur results indicate that GJB2 mutations are observed in 25% of Turkish patients with autosomal recessive non-syndromic hearing loss. We found a novel nonsense mutation, named as c.327-328delGGinsA (p.Glu110Argfs*2), in our population.