Screening of Myo7A Mutations in Iranian Patients with Autosomal Recessive Hearing Loss from West of Iran

BACKGROUND: Hearing loss (HL) is the most frequent neurosensory impairment. HL is highly heterogeneous defect. This disorder affects 1 out of 500 newborns. This study aimed to determine the role of DFNB2 locus and frequency of MYO7A gene mutations in a population from west of Iran. METHODS: Thirty families investigated in Shahrekord University of Medical Sciences in 2014, genetic linkage analysis via four short tandem repeat markers linked to MYO7A was performed for two consanguineous families originating from Hamedan (family-13) and Chaharmahal-Bakhtiari (family-32) provinces of Iran, co-segregating autosomal recessive HL and showed no mutation in GJB2 gene in our preliminary investigation. All 49 coding exons and exon- intron boundaries of the MYO7A gene were amplified by PCR and analyzed using direct DNA sequencing. RESULTS: Two of families displayed linkage to DFNB2. Family-13 segregated a homozygous missense mutation (c.6487G>A) in exon 48 that results in a p.G2163S amino acid substitution in C-terminal domain of the myosin VIIA protein. While family-32 segregated a homozygous nonsense mutation (c.448 C>T) in exon five, resulting in a premature truncation at amino acid position 150 (p.Arg150X) in the motor domain of this protein. CONCLUSION: Mutation frequency of MYO7A gene in different populations of Iran as well as cause of HL in most cases are still unknown and more extensive studies have to be done.