[GJB2 (connexin 26) gene mutation screen in patients with nonsydromic hearing loss in Hunan]

To identify the genetic characteristics in patients with nonsydromic hearing loss (NSHL) in Hunan province, to determine the prevalence and spectrum of mutations in GJB2 gene, and to explore the pathogenic mechanism.

A total of 140 sporadic patients with NSHL were enrolled after clinical examination. Molecular studies were performed by amplifing the coding region of GJB2 gene, purifying the PCR products, and sequencing directly. Sequences were analysed by DNAStar software to determine GJB2 mutations in the patients. Special method was designed to confirm the unreported mutation.

We detected GJB2 mutation in 56 out of the 140 patients (40%, 56/140). Both of the 2 alleles were mutated in 29 patients and 1 allele in the other 27 patients, and the rate of allele mutation was 30.4%(85/280). Ten variations were detected, including 7 mutations and 3 polymorphisms. The deaf-causing mutations were nonsense mutation c.139G>T; frameshift mutation c.235delC and c.176-191del16; and missense mutation c.109G>A, c.344T>G, c.550C>T and c.571T>C. The unreported missense mutation was c.344T>G. The c.235delC mutation was the most prevalent mutation found in the 27 patients (19.3%, 27/140). The frequency of c.109G>A mutation was next to c.235delC found in 25 patients (17.9%, 25/140).

GJB2 mutation is a major cause for NSHL. The most common-spot in Chinese patients with NSHL is c.235delC. The unreported missense mutation is c.344T>G.