A novel variant of SLC26A4 and first report of the c.716T>A variant in Iranian pedigrees with non-syndromic sensorineural hearing loss

The autosomal recessive non-syndromic hearing loss (ARNSHL) can be associated with variants in solute carrier family 26, member 4 (SLC26A4) gene and is the second most common cause of ARNSHL worldwide. Therefore, this study aims to determine the contribution of the SLC26A4 genotype in the hearing loss (HL) of 40 ARNSHL pedigrees in Iran. A cohort of the 40 Iranian pedigrees with ARNSHL, having no mutation in the GJB2 gene, was selected. The linkage analysis with five short tandem repeat (STR) markers linked to SLC26A4 was performed for the 40 ARNSHL pedigrees. Then, two out of the 40 pedigrees with ARNSHL that linked to DFNB4 locus were further screened to determine the variants in all exons of SLC26A4 gene by direct DNA sequencing. The 21 exons of SCL26A4 were analyzed for the two pedigrees. A known variant (c.716T>A homozygote), it is the first reported incidence in Iran, a novel variant (c.493A>C homozygote) were detected in the two pedigrees and pathogenesis of c.493A>C confirmed in this study with review 100 hearing ethnically matched controls by PCR-RFLP analysis. The present study suggests that the SLC26A4 gene plays a crucial role in the HL occurring in Iranian pedigrees. Also, the results probably support the specificity and unique spectrum of SLC26A4 variants among Iranian HL patients. Molecular study of SLC26A4 gene may lead to elucidation of the profile of the population-specific variants which has importance in diagnostics of HL

Mutations in GJB2 as Major Causes of Autosomal Recessive Non-Syndromic Hearing Loss: First Report of c.299-300delAT Mutation in Kurdish Population of Iran

Background and Objectives: : Autosomal recessive non-syndromic hearing loss (ARNSHL) with genetic origin is common (1/2000 births). ARNSHL can be associated with mutations in gap junction protein beta 2 (GJB2). To this end, this cohort investigation aimed to find the contribution of GJB2 gene mutations with the genotype-phenotype correlations in 45 ARNSHL cases in the Kurdish population. Subjects and Methods: : Genomic DNA was extracted from a total of 45 ARNSHL families. The linkage analysis with 3 short tandem repeat markers linked to GJB2 was performed on 45 ARNSHL families. Only 9 of these families were linked to the DFNB1 locus. All the 45 families who took part were sequenced for confirmation linkage analysis (to perform a large project). Results: : A total of three different mutations were determined. Two of which [c.35delG and c.-23+1G>A (IVS1+1G>A)] were previously reported but (c.299-300delAT) mutation was novel in the Kurdish population. The homozygous pathogenic mutations of GJB2 gene was observed in nine out of the 45 families (20%), also heterozygous genotype (c.35delG/N)+(c.-23+1G>A/c.-23+1G>A) were observed in 4/45 families (8.8%). The degree of hearing loss (HL) in patients with other mutations was less severe than patients with c.35delG homozygous mutation (p<0.001). Conclusions: : Our data suggest that GJB2 mutations constitute 20% of the etiology of ARNSHL in Iran; moreover, the c.35delG mutation is the most common HL cause in the Kurdish population. Therefore, these mutations should be included in the molecular testing of HL in this populatio

Update of spectrum c.35delG and c.-23+1G>A mutations on the GJB2 gene in individuals with autosomal recessive nonsyndromic hearing loss

Hearing loss (HL) is the most common birth defect and the most prevalent sensorineural condition worldwide. It is associated with more than 1,000 mutations in at least 90 genes. Mutations of the gap junction beta-2 protein (GJB2) gene located in the nonsyndromic hearing loss and deafness (DFNB1) locus (chromosome 13q11-12) are the main causes of autosomal recessive nonsyndromic hearing loss worldwide, but important differences exist between various populations. In the present article, two common mutations of the GJB2 gene are compared for ethnic-specific allele frequency, their function, and their contribution to genetic HL in different populations. The results indicated that mutations of the GJB2 gene could have arisen during human migration. Updates on the spectrum of mutations clearly show that frequent mutations in the GJB2 gene are consistent with the founder mutation hypothesis