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

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.