Analysis of common deafness gene mutations in deaf people from unique ethnic groups in Gansu Province, China

Analysis of GJB2 Gene Mutations in 1330 Deafness Cases of Major Ethnic Groups in Northwest China

Background: The GJB2 gene is the most common deafness gene, and epidemic characteristics have obvious racial specificity. Our study aimed to investigate the prevalence and ethnic specificity of the GJB2 gene in deafness in major ethnic groups in Northwest China, evaluate the value of molecular screening for deafness in minority populations, and explore the strategies and methods for genetic diagnosis. Methods: Ethics approval was obtained to collect 1330 cases of moderate to very severe nonsyndromic sensorineural deafness in northwestern China. The mutation characteristics of ethnic minorities were analyzed and compared with those of 464 patients with nonsyndromic sensorineural deafness among ethnic Han in the northwestern from research group by Sequence Scanner V25.0. Then, we analyzed the ethnic specificity of the mutations. Results: A total of 15 GJB2 sequence changes were detected in 1330 minority patients. The study showed that the allele frequency in Tibetan patients was significantly lower than that in Hui and Dongxiang patients, that in Uygur patients was significantly lower than that in Han and Hui patients, and that in Kazak and Tibetan patients was significantly lower than that in Han patients, and the differences between other ethnic groups were not statistically significant. Each ethnic group has a unique GJB2 gene mutation spectrum, and its hotspot mutation distribution has its own characteristics, with c.235delC, c.109 G > A, c.299-300delAT, and c.35delG being common. Conclusions: It has been confirmed that GJB2 gene mutation has a high prevalence in patients with nonsyndromic sensorineural hearing loss in Northwest China. Each ethnic group has a unique mutation spectrum for the GJB2 gene, which is related to its genetic background. It is necessary to develop a corresponding gene diagnosis strategy according to the hotspot mutations and mutation spectrum of each ethnic group.

Pregestational screening of hereditary deafness genes carriers in 10,684 normal pregnant women in Zhuzhou, China

BACKGROUND

Mutations in genes associated with deafness differ between ethnic groups and regions in China. In this study, we investigated the genes associated with deafness in pregnant women to analyze the distribution of mutations leading to deafness in Zhuzhou, China.

METHODS

A total of 10,684 pregnant women were enrolled in this study. DNA samples were collected to detect the 14 common mutations in deafness genes (at 108 sites).

RESULTS

Prevalence of mutations in deafness genes in pregnant women with normal hearing in Zhuzhou was 4.92% (526/10,684). Among these 526 pregnant women with deafness gene mutations, the frequencies of mutated GJB2, GJB3, SLC26A4, and mtDNA 12S rRNA were 40.11, 7.22, 40.68, and 11.98%, respectively. The hotspots for mutations in the deafness genes were: c.235delC in GJB2 (31.18%), c.919-2A > G in SLC26A4 (18.44%), c.299_300delAT in GJB2 (5.70%), m.7444G > A in mtDNA 12S rRNA (5.70%), c.1229C > T in SLC26A4 (5.51%), m.1555A > G in mtDNA 12S rRNA (5.32%), accounting for 71.85%. Moreover, husbands of the 526 pregnant women who carried the deafness gene mutations were also included in the analysis to detect deafness gene mutations. Among the 526 husbands, 23 husbands carried mutations in deafness genes, accounting for 4.37%. The deafness gene mutations of the husbands and pregnant wives were not the same. In addition, the results of the neonatal follow-up hearing tests were all normal.

CONCLUSION

Our study identified the prevalence of mutations in GJB2, SLC26A4, mtDNA 12S rRNA, and GJB3 genes in pregnant women from Zhuzhou, China.

Prevalence of the mitochondrial 1555 A>G and 1494 C>T mutations in a community-dwelling population in Japan

Single nucleotide polymorphisms in mitochondrial DNA, such as mitochondrial 1555 A>G (m.1555 A>G) and mitochondrial 1494 C>T (m.1494 C>T), are known to be causative mutations of nonsyndromic hearing loss following exposure to aminoglycoside antibiotics. The prevalence of the m.1555 A>G and m.1494 C>T mutations has not been reported for the general population in Japan. The purpose of this study was to investigate the prevalence of m.1555 A>G and m.1494 C>T mutations in a community-dwelling population in Japan in order to prevent aminoglycoside-induced hearing loss. We recruited participants older than 20 years of age to the Iwaki Health Promotion Project in 2014, 2015, and 2016, resulting in the recruitment of 1,683 participants. For each participant, we performed a hearing test and a genetic test for the m.1555 A>G and m.1494 C>T mutations using the TaqMan genotyping method. The m.1555 A>G mutation was detected in only 1 of the 1,683 participants (0.06%). This carrier of the m.1555 A>G mutation was a 69-year-old male with bilateral, symmetric, and high-frequency hearing loss. We provided genetic counseling and distributed a drug card advising him to avoid the administration of aminoglycoside antibiotics. In contrast, the m.1494 C>T mutation was not detected in this study population.

Mutations in GJB2 as Major Causes of Autosomal Recessive Non-Syndromic Hearing Loss: First Report of c.299-300delAT Mutation in Kurdish Population of Iran

Background and Objectives

Autosomal recessive non-syndromic hearing loss (ARNSHL) with genetic origin is common (1/2000 births). ARNSHL can be associated with mutations in gap junction protein beta 2 (GJB2). To this end, this cohort investigation aimed to find the contribution of GJB2 gene mutations with the genotype-phenotype correlations in 45 ARNSHL cases in the Kurdish population.

Subjects and Methods

Genomic DNA was extracted from a total of 45 ARNSHL families. The linkage analysis with 3 short tandem repeat markers linked to GJB2 was performed on 45 ARNSHL families. Only 9 of these families were linked to the DFNB1 locus. All the 45 families who took part were sequenced for confirmation linkage analysis (to perform a large project).

Results

A total of three different mutations were determined. Two of which [c.35delG and c.-23+1G>A (IVS1+1G>A)] were previously reported but (c.299-300delAT) mutation was novel in the Kurdish population. The homozygous pathogenic mutations of GJB2 gene was observed in nine out of the 45 families (20%), also heterozygous genotype (c.35delG/N)+(c.-23+1G>A/c.-23+1G>A) were observed in 4/45 families (8.8%). The degree of hearing loss (HL) in patients with other mutations was less severe than patients with c.35delG homozygous mutation (p<0.001).

Conclusions

Our data suggest that GJB2 mutations constitute 20% of the etiology of ARNSHL in Iran; moreover, the c.35delG mutation is the most common HL cause in the Kurdish population. Therefore, these mutations should be included in the molecular testing of HL in this population.

Genetic mutations in non-syndromic deafness patients in Hainan Province have a different mutational spectrum compared to patients from Mainland China

OBJECTIVES

To provide appropriate genetic testing and counseling for non-syndromic hearing impairment patients in Hainan Province, an island in the South China Sea.

METHODS

299 unrelated students with non-syndromic hearing loss who attended a special education school in Hainan Province were enrolled in this study. Three prominent deafness-related genes (GJB2, SLC26A4, and mtDNA 12S rRNA) were analyzed using Sanger sequencing.

RESULTS

GJB2 mutations were detected in 32.78% (98/299) of the entire cohort; however, only 5.69% (17/299) had two confirmed pathogenic mutations. The most common mutation observed in this population was c.109G > A in the GJB2 gene, with an allelic frequency of 15.05% (90/598), which is significantly higher than that reported in previous cohorts. A total of 16 patients had two confirmed pathogenic SLC26A4 gene mutations, and 16 patients had one. The IVS7-2A > G mutation was the most commonly observed, with an allelic frequency of 3.51% (21/598). Three patients had a m.1555A > G mutation in the mtDNA 12S rRNA gene.

CONCLUSIONS

These results reveal that genetic etiology occurred in 11.71% (35/299) of patients, suggesting that Hainan province have a different mutational spectrum compare to Mainland China in non-syndromic deafness patients, which provide useful information to genetic counseling in Hainan province.

Association between polymorphisms in the APOB gene and hyperlipidemia in the Chinese Yugur population

We investigated the influence of apolipoprotein B gene (APOB) variants on the risk of hyperlipidemia (HL) in 631 middle-aged and elderly members of the Chinese Yugur population (HL, n=336; normolipidemia, n=295). APOB polymorphisms were identified using mass spectrometry, and five single nucleotide polymorphisms (rs1042034, rs2163204, rs512535, rs676210, and rs679899) and serum lipids were further analyzed. rs1042034 and rs676210 were significantly associated with HL (P<0.05). Compared with the GG or AA genotype, individuals with AG and AG+AA in rs1042034 and with AG and AG+GG in rs676210 had a 1.67-fold (95%CI=1.20-2.33),1.63-fold (95%CI=1.19-2.24), 1.72-fold (95%CI=1.24-2.40), and 1.67-fold (95%CI=1.21-2.291) increased risk of high HL, respectively. rs2163204 was in strong linkage disequilibrium with rs1042034, rs676210, and rs679899, and strong disequilibrium was observed between rs1042034 and rs676210 (D'>0.9). Compared with the GTGAA haplotype, haplotypes ATGGA and ATAGG were more strongly associated with HL [odds ratio (OR)=1.46, 95%CI=0.02-2.11; OR=1.63, 95%CI=1.03-2.60, respectively]. The risk factors age (P=0.008), body mass index (P<0.0001), GA+GG genotype in rs676210 (P=0.009), and alcohol consumption (P=0.056) contributed strongly to HL development. The A allele of rs1042034 and the G allele of rs676210 may thus predispose middle-aged and elderly members of the Chinese Yugur population to HL in combination with other genetic or nutritional factors, and could be used as new genetic markers for HL screening.