FREQUENCY OF 35DELG MUTATION IN GJB2 GENE IN AUTOSOMAL RECESSIVE NON-SYNDROMIC HEARING LOSS (ARNSHL)

Hearing loss is the most common inherited sensory disorder affecting approximately one child in every 1000 births. At least 50% of hearing loss is inherited and about half of the genetic hearing loss is autosomal recessive non-syndromic. Several hundred genes have been identified being responsible both for syndromic and non-syndromic deafness. DFNB1 due to mutation of GJB2 gene is the most frequent autosomal recessive non-syndromic hearing loss. Although many mutations have been found in GJB2, a single mutation, i.e. 35delG is responsible for the majority of cases in different populations. The identification of GJB2 mutations in a population would provide a diagnostic tool for a common genetic form of deafness and can be used in prenatal diagnosis and also would be helpful in the risk assessment for family members of the proband. The aim of this study was to determine the rate of 35delG mutation of GJB2 gene in non-syndromic prelingual hearing loss in West Azerbaijan population. 103 cases from 81 families with autosomal recessive non-syndromic hearing loss were screened for 35delG mutation in the GJB2 gene. 3-5 ml of whole blood was taken for genomic DNA extraction. The mutation was screened using a semi-nested PCR method. RFLP analysis with EcoNI carried out on the PCR product and subsequently visualized on a 2% agarose gel. Homozygote 35delG mutation was detected in 5 patients. Sixty-nine out of 103 (67%) studied cases were sporadic, and 33% were familial. Four out of five cases with 35delG mutation were offsprings of consanguineous union. 206 chromosomes from 103 patients with autosomal recessive non-syndromic hearing loss were studied and 35delG mutation was found in 10 chromosomes (5 patients were homozygote). The frequency of 35delG mutation was 4.85%. Based on the results of this study it can be concluded that the other genes or mutations could result in autosomal recessive non-syndromic hearing loss in West Azerbaijani population