Mutation analysis of the GJB2 gene of patients with non-syndromic hearing impairment in the Kurdish population in Sulaimani province, Iraq

Approximately 60% of all cases of congenital bilateral sensorineural hearing impairment are due to genetic factors, and about 50% of hearing impairment cases at a later stage are caused by a mutation in a single gene. Because of the high frequency of gap junction beta-2 protein gene (GJB2) mutations, mutation analysis of this gene is widely used in hearing impairment research and diagnosis. This study aimed to determine the prevalence of common GJB2 mutations in patients with profound non-syndromic sensorineural hearing impairment. Sixty-one patients (32 male and 29 female) included in this study had above 90 decibels of bilateral sensorineural hearing impairment. Patient DNA was isolated from buccal cells. The 1st and 2nd exons of the GJB2 gene were amplified with specific primers after gel purification of both regions. Sanger DNA sequencing analysis was used for investigation of changes in these gene regions. The pathological variant was found in nine patients (15%). This variation involved a frameshift mutation in GJB2 (homozygous 35delG) of the 2nd exon; no mutation was detected in the 1st exon. This study is the first report of a genetic investigation of hearing impairment in the Kurdish population in Sulaimani province, northeastern Iraq, near the Iraq-Iran border. The results show that 35delG mutation has a high prevalence in patients with non-syndromic sensorineural hearing impairment.