Analysis of mutations of 4 common genes among 216 patients with non-syndromic hearing impairment

Objective: To explore the characteristics of mutations 4 common deafness-related genes among 216 patients from Shanghai area with non-syndromic hearing impairment (NSHI).

Methods: Thirteen mutation sites in the four genes, namely GJB2 (c.35delG, c.176del16, c.235delC, c.299delAT, and c.155delTCTG), SLC26A4 (c.IVS7-2A>G, c.2168A>G, and c.1229C>T), mtDNA 12SrRNA (m.1494C>T, m.1555A>G, m.7445A>G, and m.12201T>C) and GJB3 (c.538C>T) were detected among the 216 patients and 41 individuals with normal hearing. The frequency and types of mutations were compared between the two groups.

Results: Among the 216 NSHI patients, the total detection rate was 16.20% (35/216). GJB2 mutations were found in 17(7.87%) of the 216 patients, which included 5 cases with homozygous c.235delC mutation, 5 with homozygous c.235delC mutation, 1 with homozygous c.299delAT mutation, and 1 with homozygous c.299delAT mutation. c.235delC and 299delAT mutations were found in 5 cases. SLC26A4 mutation was found in 12(5.56%) of the 216 patients, which included 2 cases with homozygous c.IVS7-2A>G mutation, 9 with homozygous c.IVS7-2A>G mutation, and 1 with homozygous c.2168A>G mutation. Homogeneous mtDNA 12SrRNA m.1555A>G mutation was found in 6(2.78%) of the 216 patients. No GJB3 gene mutation was detected. No mutation of the 4 genes were detected in the 41 individuals with normal hearing. In 2 cases of the 12 patients with SLC26A4 gene mutation, CT scan of the temporal bone has confirmed expansion of vestibular aqueduct.

Conclusions: Above results indicated that GJB2 and SLC26A4 were the major genes involved with hearing loss in Shanghai area.