Molecular characterization of autosomal recessive non syndromic hearing loss in selected families from District Mardan, Pakistan.

Deafness is the most common sensory disorder, which affects 1/1000 neonates globally. Genetic factors are major contributors for hearing impairment. This study was conducted to explore the linkage of DFNB loci and their mutations with NSHL in selected Pakistani families. We included 10 families with history of deafness from district Mardan, Pakistan. Blood sample (5ml) along with personal and clinical information was collected from the available family members including both diseased and un-affected individuals. Genomic DNA was amplified using loci specific STR markers to investigate the linkage of DFNB loci. Family found linked with DFNB4 locus was screened for SLC26A4 mutations. One out of the ten explored families was found linked with DFNB4 locus which was further investigated for SLC26A4 gene mutation through direct DNA sequencing. Two novel mutations were observed in the studied family, one at splice donor site (164+2T>G) and the other at position 164+5C>G only in the affected members of the linked family. DFNB4 locus was found linked in the present study which harbors SLC26A4 gene. The novel mutation of SLC26A4 gene at the splice donor site results in skipping of the first coding exon and thus can lead to loss of expression of SLC26A4 product in the inner ear.