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Conclusions: The mutation c.508_511dup in GJB2 gene has been incorrectly named as other mutations. It is essential to standardize mutation nomenclature to describe complex mutations. Objectives: This paper aimed to verify a series of patients with the frame-shift mutation c.508_511dup in the GJB2 gene and review the literature on related mutations. Methods: All the included patients with non-syndromic hearing loss (NSHL) carried the 504insAACG or c.508_511dup mutation of the GJB2 gene in the present study. Their parents were encouraged to participate. After written informed consent and clinic data had been obtained, genomic DNA was extracted from venous blood of participants. The target fragments were amplified by polymerase chain reaction (PCR) and subjected to bidirectional sequencing to identify sequence variations. Results: A total of 14 patients with prelingual NSHL and 6 normal parents were recruited. Genotyping revealed that one mutation, c.508_511dup (not 504insAACG), was homozygous in 1 patient, heterozygous in 2 patients and 3 parents, and compound heterozygous in 11 patients. Twelve patients had hearing loss caused by c.508_511dup in a homozygous or compound heterozygous form, and further study showed that it was wrongly named as 504insAACG. Additionally, according to the standard nomenclature, the previously reported mutations with distinct names from the literature review may be replaced by c.508_511dup. [ABSTRACT FROM AUTHOR]

Conclusions: The GJB2 gene mutation characteristic of Dongxiang was the interaction result of ethnic background and geographical environment, and Yugur exhibited the typical founder effect. The SLC26A4 gene mutation characteristic of Dongxiang was related to caucasian backgrounds and selection of purpose exons, i.e. ethnic background and the penetrance of ethnic specificity caused the low mtDNA1555A>G mutation frequency in Dongxiang. Objectives: To determine the prevalence of GJB2 and SLC26A4 genes and mtDNA1555A>G mutations and analyze the ethnic specificity in the non-syndromic sensorineural hearing loss (NSHL) of unique ethnic groups in Gansu Province. Methods: Peripheral blood samples were obtained from Dongxiang, Yugur, Bonan, and ethnic Han groups with moderately severe to profound NSHL in Gansu Province. Bidirectional sequencing (or enzyme digestion) was applied to identify the sequence variations. Results: The pathogenic allele frequency of the three gene mutations was different. The frequency of the GJB2 gene among the Dongxiang, Yugur, Bonan, and ethnic Han groups was 9.03%, 12.5%, 5.88%, and 12.17%, respectively. No difference was found between the ethnic groups. The frequencies of the SLC26A4 genes were 3.23%, 8.33%, 0%, and 9.81%, respectively. The mutation frequency of mtDNA1555A>G was 0%, 0%, 0%, and 6.03%, respectively. No difference was found between the ethnic groups, except for the Dongxiang and ethnic Han groups, both in SLC26A4 gene and mtDNA1555A>G. [ABSTRACT FROM AUTHOR]

Conclusion: In the northwest of China, the prevalence of mutations of the three prominent deafness-related genes, GJB2, SLC26A4, and mitochondrial DNA (mtDNA) 12S rRNA, among Tibetan, Tu nationality, and Mongolian subjects is high, at 19%, 28.57%, and 21.05%, respectively. Molecular genetic screening for these mutations and genetic counseling are effective methods to prevent the occurrence of hereditary hearing loss. Objective: To analyze the prevalence of the three common deafness genes GJB2, mtDNA, and SLC26A4 gene mutations in Tibetan, Tu nationality, and Mongolian patients with nonsyndromic hearing impairment in the Northwest region of China. Methods: Genomic DNA was extracted from a total of 189 Tibetan, Tu nationality, and Mongolian probands from the northwest of China. PCR and direct sequencing were used to analyze the coding region of GJB2, mtDNA, and SLC26A4 genes. Results: The mutant allele rate of GJB2 gene was 6.2% in Tibetan and 11.22% in Tu nationality patients, c.235delC was the most prevalent mutation, accounting for 75% of the mutant GJB2 alleles. Mutant allele frequency of SLC26A4 in Tibetan, Tu nationality, and Mongolian subjects was 4.54%, 6.12%, and 15.79% respectively; p.IVS7-2A>G was the most common form. Mongolian cases were significantly higher than Tibetan cases (χ2 = 7.281, p = 0.007 and p < 0.05). mtDNA A1555G mutation was detected in six Tibetan, five Tu nationality, and one Mongolian subject; one Tibetan patient carried the C1494T mutation. [ABSTRACT FROM AUTHOR]