Spectrum and frequency of GJB2 mutations causing deafness in the northwest of Iran

Abstract

Objective: Mutations in GJB2 and GJB6 which comprise DFNB1 locus cause up to half of all cases of the prelingual autosomal recessive non-syndromic hearing loss (ARNSHL) worldwide. This study has intended to assess the spectrum and frequency of GJB2/GJB6 mutations in northwest of Iran.

Methods: 508 Patients with presumed ARNSHL were analyzed by applying ARMS-PCR, SSCP, PCR-RFLP and sequencing assays.

Results: Seventy-five (14.7%) different homozygous and eighty-seven (17.1%) different compound heterozygous genotypes were detected in this cohort. Concerning the GJB2 gene, c.35delG was the most prevalent mutation, accounting for 16.4% of the samples. In addition 29 sequence variations other than c.35delG mutation were distinguished in GJB2; namely, delE120, Ins A 290-291, R143Q, V37I, R32H, Y155X, V27I + T123N, F154F, 167delT, 312del14, 299-300delA, T8M, W24X, E114G + V27I, 235delC, R184P, V153I, S139N, A171T, M163V (unknown mutation), G127V, E147X, R127H, 35insG, R143W, V27I, G160S, E114G and IVS1 + 1G > A. Moreover, the IVS1 + 1G > A was accounted as a second common mutation.

Conclusions: Overall, the frequency of GJB2 mutations (≥31%) is in agreement with other white population. These findings highlight the importance of the study of GJB2 gene in the diagnosis to provide early treatment and genetic counseling.

Keywords: 35delG; ARNSHL; GJB2 gene; Prelingual hearing loss.