Prevalence and range of GJB2 and SLC26A4 mutations in patients with autosomal recessive non‑syndromic hearing loss.

The frequency and distribution of genetic mutations that cause deafness differ significantly according to ethnic group and region. Zhejiang is a province in the southeast of China, with an exceptional racial composition of the population caused by mass migration in ancient China. The purpose of the present study was to investigate the prevalence and spectrum of gap junction‑β2 (GJB2), solute carrier family 26 (anion exchanger) member 4 (SLC26A4) and GJB3 mutations in patients with autosomal recessive non‑syndromic hearing loss (ARNHL) in this area. A total of 176 unrelated pediatric patients with ARNHL were enrolled in the study. A genomic DNA sample was extracted from the peripheral blood. Polymerase chain reaction was employed, and the products were sequenced to screen for mutations in GJB2. In addition, a SNaPshot sequencing method was utilized to detect four hotspot mutations in SLC26A4 (IVS7‑2A>G and c.2168A>G) and GJB3 (c.538C>T and c.547G>A). All patients were subjected to a temporal bone computed tomography scan to identify enlarged vestibular aqueducts (EVA). In total, 14 different mutations, including two new mutations (p.W44L and p.D66N) of GJB2, were detected. The most common pathogenic mutation of GJB2 was c.235delC (15.1%), followed by c.176_191del16 (1.7%), c.299_300delAT (1.7%), c.508_511dup (0.85%) and c.35delG (0.28%) of the total alleles. Mutation analysis of SLC26A4 demonstrated that 13.6% (24/176) of patients carried at least one mutant allele. The patients with EVA (84.2%) had SLC26A4 mutations, and 31% had homozygous mutations. Only one patient carried a heterozygous mutation of GJB3 (c.538C>T). Compared with the other regions of China, in the present population cohort, the prevalence and spectrum of mutations in GJB2 was unique, and in patients with EVA the frequency of a homozygous mutation in SLC26A4 was significantly lower. These findings may be of benefit in genetic counseling and risk assessment for families from this area of China.