Genetic study of 45 big hearing loss pedigrees and GJB2 gene mutations frequency in Chaharmahal va Bakhtiari province, Iran, 2008

Hearing loss is the most common sensorineural disorder in human. Despite the contribution of several different genes in causing deafness, mutations in the GJB2 gene have been involved in deafness in many populations. This study aims to investigate genetic epidemiology and frequency of GJB2 gene mutations in 45 big deaf pedigrees. In this genetic epidemiology study we have investigated 45 big deaf pedigrees concerning inheritance patterns, consanguinity and diversity of deafness severity among siblings using data collected by questionnaires and audiograms. We examined also the frequency and profile of GJB2 gene mutations in 45 probands using direct sequencing strategy. Our study revealed 73% of consanguinity in the deaf pedigrees studied. The most common type of first cousins marriage was found between first cousins who were the children of two brothers. We found autosomal recessive and X-linked recessive pattern in 94-97% and 3-6% of the pedigrees studied respectively. Regarding molecular analysis, GJB2 mutations were found in 11% of population studied including 35delG, 167delT, 299-300delAT and 363delC. A high rate of consanguineous marriage determined in this study could raise the rate of autosomal recessive patterns up to 94-97% of the overall pedigree and would be the main cause to prepare the way for congenital deafness. This study revealed a low contribution of GJB2 gene mutations in causing deafness in Chaharmahal va Bakhtiari province.