[Analysis of the hereditary etiology of 336 patients with non-syndromic sensorineural hearing loss from Ningxia Hui Autonomous Region of China].

Objective: To investigate the molecular genetic causes and their characteristics of deafness in Ningxia province, we established screening of three common hereditary deafness genes in 336 deaf and hard-of-hearing patients in this district.

Methods: Peripheral blood samples were obtained from a total of 336 patients with non-syndromic sensorineural hearing loss in parts of special education schools in Ningxia province to extract genomic DNA. The mitochondrial DNA 12S rRNA m.1555A > G mutation was screened by PCR Alw26I digestion and sequence analysis PCR and direct sequencing were used to analyze the coding region of GJB2 and exons 8 and 19 of SLC26A4. Statistical analysis was performed by using SPSS 11.0 software. Frequencies of different GJB2 or SLC26A4 mutations were compared between Han and Hui people.

Results: Among these 336 patients, seven cases (2.08%, 7/336) were found to carry mtDNA 12S rRNA m.1555A > G homozygous mutation, 45 cases (13.39%) were caused by GJB2 mutations and 28 cases (8.33%) had two mutated alleles (homozygote and compound heterozygote) of SLC26A4. In detail, 16.67% (56/336) patients carried GJB2 mutations including 11 single mutant carriers. The allele frequency of c.235delC and c.299_300delAT were 9.52% (64/672) and 2.68% (18/672), respectively, making up 81.19% (82/101) of all pathogenic mutated alleles for GJB2. The single mutant allele carriers of SLC26A4 is 32, and two types (c.919-2A > G and c.2168A > G) accounted for 95.29% (24/27) mutations, totally. We also found that statistically significant differences in c.919-2A > G and c.2168A > G frequencies between Han and Hui people (c.919-2A > G, χ(2) = 8.229, P = 0.004; c.2168A > G, χ(2) = 5.277, P = 0.022). However, there was no statistically significant difference in GJB2 mutation between Han and Hui people.

Conclusions: GJB2 mutation was a primary cause for non-syndromic sensorineural hearing loss in Ningxia province, and c.235delC was the most common mutant forms of GJB2. c.919-2A > G and c.2168A > G were common mutant forms of SLC26A4, their frequencies were also statistically significant differences between Han and Hui people.