Comparison and Analysis of Common Mutations in Uighur and Han Patients with Non-syndromic Deafness in Xinjiang
|School||Xinjiang Medical University|
|Keywords||GJB2gene SLC26A4 gene 12srRNA gene GJB3 gene deafness Xinjiang mutation|
objective:50%of childhood deafness is considered to be related with genetic factors. So far,62 genes, connecting with non-syndromic deafness, have been identified. Among the large number of deafness genes, each one of them distributing in numerous mutation sites possesses a high level of loci and genetic heterogeneity. The dominant mutations and mutation spectrums are different in regions and ethics. As a cultural interchange of the central and western Asia in the northwest border of China, Xinjiang is a Uighur-based multi-ethnic area. During the national migration and integration for thousands of years, the gene mutation spectrum of deafness and dominant mutation for the Xinjiang Uighur may have their own features. This research scans the mutation sites of deafness genes in Uighur and Han patients of non-syndromic deafness to reveal the mutation characteristics of common deafness genes in Uighur patients and the differences from the Han counterparts.Methods:Select typical Uighur and Han deaf patients in Xinjiang, who are centered in the schools, hospitals, and social assistance agencies, including the Special Education School of Kashi, the Federations of the Disabled in Kashi, the Language Training School of Kashi, the Special Education School of Changji, the Federations of the Disabled in Xinjiang Uighur Autonomous Region, the Language Training School of Urumqi, and the Otolaryngological Department of the First Affiliated Hospital of Xijiang Medical University, as the screening objects of non-syndromic deafness. And then the patients of non-syndromic deafness will be selected after collecting their basic information, audiological testing, and general physical checkup. Meanwhile,103 Uighur and 70 Han people with normal hearing are selected as the control subjects.3-5ml forearm venous blood samples are taken from the selected study objects and DNA of whole blood is extracted. The gene mutations in hearing loss of the selected study objects are examined by the Crystal Core" nine hereditary deafness gene microarray (detection chip) designed and developed by CapitalBio Corporation. The chip consists of 4 genes (GJB2, SLC26A4, mtDNA 12s rRNA, and GJB3m) which include 9 loci (35delQ 176de116,235delC,299-300delAT,538C>T,1555A>G,1494C>T, 2168A>G, and IVS7-2A>G. T). As for the samples with absent signals at some loci, we performed DNA sequence analysis. ABI 3730 sequencer in the United States is applied for the further study on gene sequencing to identify new mutations.Results:350 non-syndromic deafness patients with no consanguinity are screened from 441 deaf patients, including 119 Uighur and 151Han. Among the 350 selected subjects with moderately severe bilateral sensorineural deafness,33patients have family history of deafness, that is, there are deaf patients in their siblings and parents, consisting of 22 Uighur and 11 Han.Test for mutant genes is performed in the study objects and the control group. As for the 4 samples with absent signals at some loci, we performed gene sequence analysis. Mutation rates of common deafness genes in Uighur study group and Han study group are 13.06%and 32.45%, with significant difference; mutation rates of GJB2 gene in Uighur and Han patients are 9.05%and 16.56%respectively, with no significant difference. 235delC is the hotspot mutation in Uighur and Han patients, while 35delG is a hotspot mutation in Uighur patients only.187delG identified only in Uighur patients is a novel pathological mutation of GJB2 gene. Mutation rates of SLC26A4 gene in Uighur and Han patients are 2.01%and 14.57%, with significant difference. Mutation rate of SLC26A4 gene in Uighur patients is much lower than their Han counterparts. Mutation rates of mtDNA 12srRNA gene in Uighur and Han patients are 2.01%and 2.65%, with no significant difference. Mutation rate of GJB3 gene mutation is lower in the two ethnic groups.Among the 22 Uighur subjects with family history of deafness,3 cases of mutations are detected. The detected positive rate is 13.64%(3/22). Among the 22 Uighur subjects with family history of deafness,6 cases of mutation are detected. The detected positive rate is 54.55%(6/11). Compared with the detected positive rate in Uighur subjects with family history of deafness, that of Han patients is higher, with significant difference.Conclusion:The Uighur and Han screening objects of non-syndromic deafness in this research come from the Special Education School of Kashi, the Federations of the Disabled in Kashi, the Language Training School of Kashi, the Special Education School of Changji, the Federations of the Disabled in Xinjiang Uighur Autonomous Region, the Language Training School of Urumqi, and the Otolaryngological Department of the First Affiliated Hospital of Xijiang Medical University. As a result, these screening objects not only include the deaf patients in Uighur-based areas, such as Kashi and Hetian, but also in the Han-based areas around Urumqi.Mutation rates of common deafness genes in Uighur study group and its control group, Han study group and its control group are 13.06%,1.94%,32.45%, and 4.28% respectively. The comparison of mutation rates in these four groups has significant difference. The mutation rates of study groups are much higher than that of the control groups, which show that test for common deafness genes has positive meaning to the diagnosis of deafness. The mutation rate of the Uighur control group is much lower than that of the Han control group, which shows that gene mutation spectrum in Uighur patients with non-syndromic deafness is not completely consistent with that in Han patients. GJB2 gene is still the major gene connecting with non-syndromic deafness in both ethnic groups. The hotspot mutation is different. For SLC26A4 gene, mutation rate in Uighur patients is significantly lower, so it can be speculated that the hotspot mutation of SLC26A4 gene may be different from the Mongols’. Whether there is a consistence with the hotspot mutation of Caucasians still needs further research. It is necessary to further analyze the gene sequence and investigate family line of Uighur deaf patients in order to enrich the Uighur deafness genes and identify the superior mutations.Inspection on common mutation of deafness gene is not the objective of the study. Based on the diagnosis of deafness gene, we serve consultation on genetic deafness to the deafness and their family members and communicate on issues such as cause, inheritance mode, diagnose, prevention and prognosis. Assessment on the risk of deafness of their filial generation and further suggestion and instruction should be proposed. The following prenatal counseling and interventions will prevent and block the birth of deaf infants and eventually enhance the overall quality of people in our country. Thereby, consultation on genetic deafness is essential to the whole prevention and cure of deafness.