Screening for Autosomal Recessive Nonsyndromic Hearing Loss(DFNB1) among Deaf Patients of East and west Azarbaijan Provinces

Hereditary hearing loss(HHL) affects one in 1000-2000 newborns and more than 50% of these cases have a genetic base. About 70% of HHL are nonsyndromic with autosomal recessive forms accounting for 85% of the genetic load. Different genes have been reported to be involved, but mutations in GJB2 gene at DFNB1 locus have been established as the basis of autosomal recessive nonsyndromic hearing loss. In addition to GJB2 mutations, the deletion of ∆(GJB6-D13S1830) involving GJB6 gene (also localizes to DFNB1 interval) has been detected in many patients heterozygous for one mutation in GJB2 gene. The aim of this project was to study the prevalence of GJB2 mutations in Turk deaf population living in East and West Azarbaijan provinces of Iran. Mutation screening began by Amplification Refractory Mutation System(ARMS) - PCR for the detection of 35delG then, we analyzed all samples excluding 35delG homozygotes by DHPLC and Direct Sequencing for other GJB2 mutations. We screened 276 chromosomes (138 probands) for GJB2 mutations. Seventy - five chromosomes (27%) carried GJB2 mutations including 35delG, delE120,-3170G>A, W24X, 363delC, E129k, Q80L, and Y155X. Among them, 35delG had the highest frequency, and Q80L and 363delC were novel mutations which have not been reported in any other populations. Thirty-five patients(25.3%) had biallelic GJB2 mutations and five probands had monoallelic GJB2 mutations. The ∆(GJB6-D13S1830) mutation was not found in heterozygous patients. Polymorphisms found were V1531 and V271. Regarding high prevalence of DFNB1-related hearing loss in the north east of Iran, screening this population for this locus is recommended. Also, in comparison with other countries, our results suggest that other loci and genes can be responsible for nonsyndromic deafness in this population.