Familial and sporadic GJB2-related deafness in Iran: review of gene mutations

ABSTRACT

Mutations in the GJB2 gene encoding connexin 26 protein, are the main cause for autosomal recessive and sporadic non syndromic hearing loss in many populations. Here, we have taken together and reviewed results from our six previous publications, our unpublished data from ten Iranian provinces, as well as data from two previous mutation reports to provide a comprehensive collection of data for GJB2 mutations and deafness in Iran. In all, 1095 hearing impaired students and their deaf siblings from 890 families in 10 provinces of Iran were studied. The prevalence and type of the GJB2 gene mutations were investigated using nested PCR pre screening strategy and direct sequencing of the coding exon of the gene. Altogether 31 different genetic variants were detected from which 17 GJB2 mutations were identified. GJB2 mutations were found in 14.6% of deaf families [18.29% of familial and 12.7% of sporadic cases]. We found GJB2 mutations in both alleles in 78% of GJB2 mutations chromosomes. However, 35delG mutation was the most common GJB2 mutation accounting for 74.5% of the mutations in populations studied. Our data indicated that a specific combination of GJB2 mutations types and frequencies was presented in different populations of Iran. These results also highlight the importance of GJB2 mutations in development of hearing loss in familial and sporadic deaf families in different parts of the country and can be used as a basis of genetic counseling and clinical guideline in Iran