Homozygosity mapping and CDH23 mutation analysis in Iranian deaf families

Objective: Cadherin-related 23 (CDH23) gene encodes a cell-cell adhesion protein which is required for the proper development of hair cells. Previous studies have shown that different mutations in this gene are associated with Usher syndrome, autosomal recessive nonsyndromic deafness (DFNB12) and age-related hearing loss. In this study the contribution of CDH23 mutations in hearing loss has been investigated. Study design: The homosygosity mapping, using microsatellite markers linked to DFNB12 locus was performed for a population of 45 GJB2 negative Iranian families with autosomal recessive non-syndromic form of hearing loss. Coding region and exon-intron boundaries of all 69 exons of the CDH23 gene were investigated using Sanger sequencing. Results: The homozygosity mapping showed co-segregation of the hearing loss with four STR markers linked to the DFNB12 locus in one family. Assessing pathogenicity of identified variations in this gene showed that previously reported mutation c. 2968G>A (p.Asp990Asn) can be the cause of hearing loss in this family. Conclusion: This study suggests that CDH23 mutations may have a significant role in causing hearing loss in Iran. More studies should be performed to determine frequency of this gene in the Iranian population.