| Background and objectiveThe hearing loss is called deafness in the clinical,and deafness is one of the most common sensory disorders in humans.The second national handicapped person sampling survey in 2006 was showed that: there were 27.8 million people with hearing and speech disable in our country, and in which 20.04 million people with pure hearing disabled, accounting for 24.16% of the total number of the disabled.And incidence rate of neonatal deafness is approximately 1 in 1000 to 3 in 1000 children, and there are 6-80000 late-onset deaf children every year, most of them severely, profound sensorineural hearing impairment, which seriously affects patients with communication and cognition, poses a great burden and economic pressure to individuals, families and socialThere are many factors can cause deafness,which can be roughly divided into environmental factors and genetic factors, about 60% of the congenital sensorineural hearing loss is caused by genetic factors, the remaining 40% may be related to environmental factors.According to accompanied abnormality in other organ systems,genetic deafness can be divided into syndromic hearing loss?SHL? and nonsyndromic hearing loss?NSHL?.NSHL accounts for more than 70% of cases of genetic deafness.To date,more than 140 genetic loci associated with hereditary deafness have been identified, and more than 80 pathogenic gene were cloned.But there were large-scale epidemiological and deafness gene diagnosis studies by the domestic and foreign suggests that a handful of mutations can cause NSHL, And GJB2, SLC26A4 and mitochondrial DNA?mitochondrial, mt DNA? 12 Sr RNA are the most common disease genes which can cause NSHL in our country.According to different modes of hereditary deafness can be divided into autosomal dominant?AD?, autosomal recessive?AR?, X linkage, Y linkage and mitochondrial genetic, of which the autosomal recessive hereditary is the most common, accounts for about 75%-80%.And the mutant form is varied, including shear, nonsense mutations, missense mutation, insertions and deletions which can lead to frameshift mutations, etc.The epidemiological survey in deafness gene is not only beneficial to revealed the epidemiological features of deafness gene mutations in the crowd, and provide theoretical basis and data support for the early diagnosis,intervention, treatment and genetic counseling to people, but also to improve the population quality in our country and the smooth development of the national economy.Hereditary deafness is highly heterogeneous, that is, the same deafness gene may cause different phenotype, or the same phenotype its pathogenesis of deafness genes may be different, but in different nations and regions in the cause of deafness gene mutations were different, therefore, the deafness gene molecular epidemiology investigation in different areas,which can provide guiding significance according to the region of local conditions to carry out genetic counseling, diagnosis and prevention interventions. There were less research of deafness gene mutations in patients with NSHL in Henan province.To preliminarily determine the gene mutation frenquency and the hotspots in Henan province,we screened and analysed the deafness-related gene mutation in 100 patients with non-syndromic hearing loss?NSHL?,and this study will provide a theoretical basis data support to determine the etiology of deafness in Henan province. MethodsWe recruited into the study 100 patients with non-syndromic hearing loss from unrelated families from the Henan province,who were operated cochlear implantation at the Children's Hospital of Zhengzhou City between December 2013 to December 2014.The cohort of patients consisted of 63 malesand 37 females from 12 months to 17 years old,with the median age of 3 years 5 months,and they all Han. The 100 cases were performed with severely, profound sensorineural deafness by audiological examination and infantile behavior test, and they all have no language ability. They all have high-resolution computed tomography?CT? and magnetic resonance imaging?MRI? scanned of the temporal bone and scanned the internal auditory canal, cochlea water imaging, and provided that they all have no acoustic neuroma and other space-occupying lesions. The peripheral venous blood for 3 to 5 ml of all the patients were extracted by professional nurse, EDTA anticoagulant, and the genomic DNA was extracted by DNA extraction kit?TIANGEN Biotechnologies co., LTD,Beijing China?,and DNA extraction methods and procedures were referred to instructions, The DNA concentration and purity weer detected by ultramicro spectrophotometer to satisfy its concentration from 100 to 200 ng/mu l, purity of OD?260 nm / 280 nm? 1.7 2.0, and saved them in- 20 ? refrigerator spare,Then designed the primer of four common deafness gene:GJB2, SLC26A4, GJB3 and mt DNA12 Sr RAN according to the research of the Dai Pu, Yuan Yongyi, and all the primers were designed by Beijing liuhe genomics technology co., LTD.Then PCR amplification, PCR products were sented to Beijing liuhe genomics technology co., LTD.,after testing qualified, the company sequenced the genome DNA of four common deafness gene of the 100 NSHL patients: GJB2 gene?c. 35 de1 G, c. 176 de116, c. 235 de1 C, c. 299300de1AT?, SLC26A4 gene?c.I VS7-2A> G,c.2168A>G?, GJB3?c.538C>T?, mt DNA12 Sr RNA?c. 1555A>G,c.1494C>T?by the method of Sanger sequencing,and the sequence results of the GJB2, SLC26A4, GJB3 and mt DNA12 Sr RNA compared to the reference sequence on the NCBI website by useing the DNAMAN software. Informed consent was obtained from all participants,or their parents,prior to obtian the basic information of all of the patients and the clinical blood samples collection of the study. ResultsThe rate of deafness mutation detection was 40% in 100 patients with non- syndromic hearing loss?1 case also contains GJB2 and SLC26A4 gene mutations?. In these patients 25 cases who have GJB2 gene mutation and the detection rate was 25%, of which 235 delc locus mutation detection rate as high as 19%; 13 cases have SLC26A4 gene mutations, and the detection rate was 13%, including IVS7-2 A> G locus mutation rate is highest, accounting for 27.5% of all mutations in patients?11/40?;and there was no case have GJB3 gene mutation, 3 cases have mt DNA12 Sr RNA gene mutation,including 2 cases have 1555A>G locus homozygous mutationand 1 case have 1494 C> T loci homozygous mutation.There were 2 patients have been definited history of aminoglycoside antibiotics?gentamycin? application, High-resolution temporal bone CT sugested that:Enlarge Vestibular Aqueduct Syndrome? EVAS? patients in 15 cases, including 1 case of unilateral, 14 cases of bilateral,and 3 cases with inner ear malformation, 1 case of patients with a clear history of head injury.This study detected in patients with EVAS carry SLC26A4 deafness gene mutation 13 cases, accounting for 86.7% of the patients with EVAS deafness gene mutation?13/15?, carry IVS7-2 A > G site mutation 11 cases, accounting for 73.3% of the patients with EVAS gene mutation?11/15?. Conclusions1.The rate of deafness mutation was 40% in 100 patients with non-syndromic hearing loss?40/100?,which reflected the high incidence of the hereditary deafness in Henan province.2.GJB2 is the most common mutation in non-syndromic hearing loss in Henan province, and its 235 del C locus has a highest prevalence in Henan non-syndromic hearing loss populations.3.SLC26A4 mutation is the second most common cause of non-syndromic hearing loss in henan province, IVS7-2A>G locus was most common mutation of the SLC26A4 gene in Henan province.4.The genotype of SLC26A4 gene and imaging examination are consistent in enlarged vestibular aqueduct syndrome? EVAS? in Henan non-syndromic hearing loss populations.5. Hereditary deafness caused by mitochondrial DNA mutations which is closely related to the application of aminoglycoside antibiotic drugs, 1555A>G locus was most common mutation of the mt DNA12 Sr RNA gene in Henan province. |
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