赤峰市特教学校耳聋患者GJB2和GJB3及GJB6基因突变分析

目的:利用基因诊断的方法调查内蒙古自治区赤峰市特教学校非综合征耳聋患者的常见分子病因,对GJB2、GJB3、GJB6基因编码区突变进行分析.方法:调查对象来自赤峰市特教学校非综合征耳聋患者134例(耳聋组),对照组为中国北方地区(北京、河北、内蒙、山西)听力正常者100例.所有受检者均采集外周血并提取DNA,首先进行GJB2基因编码区测序,对携带GJB2单杂合突变的患者进一步检查GJB6 del(GJB6-D13S1830)突变并进行GJB6编码区测序.对除GJB2基因、线粒体A1555G突变相关性耳聋及前庭水管扩大综合征外的分子病因不明的91例非综合征耳聋患者进行GJB3基因编码区测序.结果:134例非综合征耳聋患者及100例正常对照中共检测到6种GJB2基因新的突变方式.耳聋组41例携带GJB2病理性突变,其中双等位基因突变22例,单等位基因突变19例,在GJB2单等位基因突变的耳聋患者中未检测到GJB6 del(GJB6-D13S1830)及编码区其他突变;对照组4例携带GJB2基因病理性突变.在91例分子病因不明的耳聋患者及100例正常对照中共检测到3种GJB3基因新的突变方式.耳聋组2例携带GJB3基因病理性突变,均为杂合子,其中1例同时携带GJB2单等位基因突变235delC;对照组1例携带GJB3基因病理性突变.结论:通过GJB2、GJB6、GJB3基因编码区突变分析为赤峰市特教学校16.42%(22/134)的非综合征耳聋学生明确了分子病因;新发现的突变和多态丰富了中国人GJB2、GJB3基因突变及多态性图谱,为深入开展耳聋基因筛查奠定了基础.     

携带GJB2单杂合突变非综合征型耳聋患者GJA1突变分析

目的探讨携带GJB2基因单杂合突变非综合征型耳聋患者GJA1基因突变情况。方法对205例GJB2单杂合突变的非综合征型耳聋患者进行GJA1外显子2直接测序,对照组为111例听力正常成年人。结果 205例GJB2单杂合突变患者中,GJA1c.IVS2+1insA杂合突变3例(1.45%),c.456G>A和c.717G>A各1例,都为杂合同义突变。111例对照组中,c.IVS2+1insA杂合突变3例(2.70%),c.466A>G杂合突变1例。两组c.IVS2+1insA突变率无明显差异(校正χ2=0.115,P=0.735>0.05)。结论 GJB2单杂合突变非综合征型耳聋患者中GJA1检测未见致病突变。     

非综合征型聋患者常见耳聋基因突变分析

目的分析重度和极重度非综合征型聋患者常见耳聋基因突变情况,从分子水平了解该人群聋病的遗传病因和特点,为临床防聋治聋提供策略、依据。方法应用遗传性耳聋基因芯片对179例非综合征型聋患者GJB2、GJB3、SLC26A4、线粒体12SrRNA基因中9个热点突变进行检测,同时结合耳聋病因问卷调查、纯音听阈测试、听性脑干反应测试、声导抗、颞骨CT检查。结果 179例患者中,79例存在不同程度的被检测基因位点突变,其中3例同时携带二个基因突变:①42例存在GJB2基因突变,其中:176del16位点纯合突变1例、单杂合突变2例;235delC位点纯合突变17例、单杂合突变9例;299delAT位点纯合突变0例、单杂合突变2例;235delC/299delAT复合杂合突变7例,235delC/176del16复合杂合突变4例。②37例存在SLC26A4基因突变,其中:2168A>G位点单杂合突变4例;IVS7-2A>G位点纯合突变13例,单杂合突变17例;2168A>G/IVS7-2A>G复合杂合突变3例。③3例存在线粒体12SrRNA基因突变,其中2例1555A>G位点均质突变,1例1494C>T位点均质突变;④无GJB3基因突变。在基因水平,明确诊断遗传性聋者48例,占26.80%,遗传性耳聋基因突变携带者31例,占17.32%。结论 GJB2、SLC26A4突变是安徽地区重度和极重度非综合征型聋患者主要突变形式、其次是线粒体12SrRNA基因突变,通过筛查可以明确部分非综合征型聋的病因,可以为患者及其家族成员提供准确的遗传咨询和指导,为再次生育家庭提供产前诊断,从而为防聋治聋提供帮助。     

中国非综合征遗传性聋人群GJB6基因突变分析

目的：研究GJB6基因[连接蛋白30（Cx30）-]在中国非综合征遗传性聋人群中的突变情况。方法：用特定引物对372例非综合征遗传性聋患者（其中295例分子病因不明，77例携带GJB2病理性单等位基因突变）和182例正常对照者进行聚合酶链反应，检测GJB6基因的342kb大片段缺失del（GJB6〉D13S1830），并进行GJB6基因编码区扩增，以产物直接测序方法进行突变检测及鉴定。结果：372例耳聋患者中未发现GJB6 del（GJB6〉D13S1830），其中1例发现携带GJB6基因点突变404C〉A，导致了氨基酸的错义改变T135K，多物种Cx30氨基酸序列进化分析证实该点位于Cx30高度保守的第3跨膜区。对照组中未发现同样突变。结论：GJB6基因突变在中国耳聋人群中整体发生频率较低，GJB6基因可暂不列为第一线耳聋基因检测项目。     

广西壮族135例非综合征性聋常见致病基因的研究

目的分析研究广西地区壮族人群135例非综合征性聋常见致聋基因的突变特点,为防聋治聋工作提供参考。方法采用遗传性耳聋基因芯片试剂盒对广西地区壮族人群135例以及汉族人群44例非综合征性聋患者基因组DNA的4个常见致聋基因的15个突变位点进行检测,比较壮、汉族人群常见耳聋基因突变率的差异性。结果 135例壮族人群非综合征性聋患者常见致聋基因突变率为11.11%(15/135);其中GJB2 235del C纯合突变4例(2.96%),单杂合突变3例(2.22%);GJB2 235del C/109 A>G复合杂合突变2例(1.48%);SLC26A4 IVS7-2 A>G杂合突变1例(0.74%),IVS7-2A>G/IVS11+47T﹥C/1548ins C复合杂合突变2例(1.48%);GJB3 538C>T单杂合突变1例(0.74%),线粒体12S r RNA 1555 A>G异质突变1例(0.74%),GJB2 235 del C杂合突变合并SLC26A4 1226 G>A杂合突变1例(0.74%)。44例汉族非综合征性聋患者常见致聋基因突变率为15.90%(7/44),其中GJB2 235 del C杂合突变3例(6.82%),GJB2 35 del G杂合突变1例(2.27%);SLC26A4 1229C>T纯合突变2例(4.55%),SLC26A4 IVS7-2 A>G杂合突变1例(2.27%)。壮、汉族间耳聋基因突变率比较无统计学意义。结论 GJB2和SLC26A4是广西地区壮族人群非综合征性聋患者最常见的突变基因,GJB2的4个突变位点及SLC26A4的8个突变位点突变率明显低于全国平均水平,其中SLC26A4 IVS11+47T﹥C、1548ins C和GJB2 109 A>G是3个新发现的突变位点。本地区壮汉族之间的耳聋基因突变率无明显的差异性。广西地区壮族人群非综合征性聋患者可能存在罕见的致聋基因或罕见的突变位点,需待进一步研究。     

205例先天性非综合征型聋患儿GJB2基因突变分析

目的探讨先天性非综合征型聋婴幼儿的GJB2基因突变频率、突变热点和听力学表型特点。方法对来自上海及周边地区的205例先天性非综合征型聋患儿GJB2基因PCR扩增产物行酶切鉴定以及直接测序法进行突变检测,对1例GJB2基因235delC纯合突变先证者母亲再次妊娠19周时通过羊水穿刺行产前诊断。结果205例先天性非综合征型聋儿中,共发现GJB2基因移码突变49例,占23.90%（49/205）,其中46例患儿存在GJB2基因235detc突变,占93.88%（46/49）,GJB2基因突变者多为中到极重度听力损失。1例胎儿产前诊断确诊为GJB2基因235delC纯合突变。结论GJB2基因纯合或复合杂合移码突变可导致非综合征型常染色体隐性遗传性聋,听力损失程度多为中度至极重度;235delC突变占所有突变等位基因85.88%。     

GJB2基因在遗传性聋中的检测

目的对遗传性聋家系进行GJB2基因突变检测,为该病的基因诊断提供依据。方法采用PCR直接测序法对20个非综合征型遗传性聋家系的先证者(均为耳聋患者)进行GJB2基因的突变检测。结果发现了三种碱基改变:109G>A、79G>A和341G>A。109G>A是已报道的具有争议的致病突变,本实验在两个隐性遗传性聋家系的先证者中检测到109G>A纯合突变,且与耳聋共分离。79G>A和341G>A是已报道的多态。结论本研究发现了具有争议的致病突变109G>A的纯合突变,极可能导致隐性遗传性聋。     

新疆哈萨克族非综合征型聋GJB2基因突变的研究分析

目的：研究新疆哈萨克族非综合征型聋患者GJB2基因突变的情况。方法：调查对象为来自新疆地区的193例哈萨克族患者,采用直接测序法对非综合征型聋患者97例和健康对照96例进行GJB2基因突变的检测。结果：在编码区耳聋组共发现8种碱基改变：其中35delG纯和12例,79G〉A纯合5例,79G〉A杂合8例,79G〉A与608T〉C复合杂合1例,79G〉A与341A〉G复合杂合5例,235delC杂合4例,341A〉G杂合2例,439T〉G杂合1例,457G〉A杂合1例,521G〉A纯合2例。对照组发现4种已明确的常见多态性碱基改变。结论：本研究提示新疆哈萨克族非综合征型聋患者GJB2基因突变具有种族和地域性特点,该地区哈萨克族耳聋人群中GJB2有较高携带率,在本研究中35 delG为其常见突变方式。     

散发感音神经性聋患者中GJB2基因突变检测的临床意义

目的探讨散发感音神经性聋患者中GJB2基因突变检测的临床指导意义.方法运用聚合酶链反应对解放军总医院听力诊断中心收集的242例散发感音神经性聋患者(135例语前聋患者,107例语后聋患者)的GJB2基因编码区进行扩增,扩增产物纯化后直接测序分析.结果 135例语前聋患者中GJB2基因致病突变的复合杂合和纯合个体有26例,占语前聋个体的19.26%;107例语后聋患者中未发现复合杂合和纯合致病突变,仅发现3例235delC杂合突变携带者、1例176del16杂合突变携带者.结论语前聋者GJB2基因致病突变阳性率明显高于语后聋患者,语前聋患者常规进行GJB2基因检测可从基因水平明确诊断,并为耳聋患者提供重要遗传信息.     

青海省部分聋校学生线粒体DNA12SrRNA A1555G和GJB2基因突变筛查报告

目的 通过对青海省三所聋校非综合征型耳聋(nonsyndromic hearing impairment,NSHI)学生线粒体DNA12SrRNAA1555G突变和GJB2基因突变的调查研究.在分子水平了解青海省非综合征型感音神经性聋发生的病因及其特点.方法 采集青海省特殊教育学校、西宁市聋哑学校和乐都县职业教育学校共278例NSHI患者血样,提取基因组DNA,多聚酶链反应扩增线粒体DNA和GJB2基因目的 片段,Alw26I限制性内切酶检测A1555G点突变,对酶切阳性病例和全部的GJB2基因的PCR产物进行DNA测序.结果 278例感音神经性聋患者中16例(5.76%)存在线粒体DNA12SrRNAA1555G点突变;6例(2.16%)为GJB2 235delC纯合突变,21例(7.55%)为GJB2 235delC杂合及复合杂合突变,其中235delc是GJB2基因致病突变的主要形式.占88.90%(24/27).结论 线粒体DNA12SrRNA A1555G点突变和GJB2基因突变在青海省耳聋人群中的发生率较高,通过其突变筛查可以有效避免高危人群出现耳聋.     

Absence of GJB6 mutations in Indian patients with non-syndromic hearing loss

Objective

Hearing loss is the most frequent sensory defect in human being. Genetic factors account for at least half of all cases of profound congenital deafness. The 13q11-q12 region contains the GJB2 and GJB6 genes, which code connexin 26 (CX26) and connexin 30 (CX30) proteins, respectively. Mutations in the gene GJB2, encoding the gap junction protein connexin 26, are considered to be responsible for up to 50% of familial cases of autosomal recessive non-syndromic hearing loss and for up to 15-30% of the sporadic cases. It has also been reported that mutations in the GJB6 gene contribute to autosomal recessive and autosomal dominant hearing defects in many populations. The 342-kb deletion [del(GJB6-D13S1830)] of the Cx30 gene is the second most common connexin mutation after the CX26 mutations in some NSHL populations. The aim of this study was to screen GJB6 gene mutations in Asian Indian patients with autosomal non-syndromic hearing loss.

Methods

We screened 203 non-syndromic hearing loss patients, who were negative for homozygous mutations in GJB2 gene, for GJB6-D13S1830 deletion and mutations in coding regions of GJB6 using polymerase chain reaction, denaturing high performance liquid chromatography and direct sequencing.

Results

No deleterious mutation in GJB6 gene was detected in our study cohort.

Conclusion

The present data demonstrated that mutations in the GJB6 gene are unlikely to be a major cause of non-syndromic deafness in Asian Indians.     

GJB2 (connexin 26) gene mutations in Moroccan patients with autosomal recessive non-syndromic hearing loss and carrier frequency of the common GJB2-35delG mutation

OBJECTIVE: Mutations in the connexin 26 gene (GJB2), which encodes a gap-junction protein expressed in the inner ear, have been shown to be responsible for a major part of autosomal recessive non-syndromic hearing loss in Caucasians. The aim of our study was to determine the prevalence and spectrum of GJB2 mutations, including the (GJB6-D13S1830) deletion, in Moroccan patients and estimate the carrier frequency of the 35delG mutation in the general population. METHODS: Genomic DNA was isolated from 81 unrelated Moroccan familial cases with moderate to profound autosomal recessive non-syndromic hearing loss and 113 Moroccan control individuals. Molecular studies were performed using PCR-Mediated Site Directed Mutagenesis assay, PCR and direct sequencing to screen for GJB2, 35delG and del(GJB6-D13S1830) mutations. RESULTS: GJB2 mutations were found in 43.20% of the deaf patients. Among these patients 35.80% were 35delG/35delG homozygous, 2.47% were 35delG/wt heterozygous, 3.70% were V37I/wt heterozygous, and 1 patient was E47X/35delG compound heterozygous. None of the patients with one or no GJB2 mutation displayed the common (GJB6-D13S1830) deletion. We found also that the carrier frequency of GJB2-35delG in the normal Moroccan population is 2.65%. CONCLUSIONS: These findings indicate that the GJB2-35delG mutation is the major cause of autosomal recessive non-syndromic hearing loss in Moroccan population. Two other mutations were also detected (V37I and E47X), in agreement with similar studies in other populations showing heterogeneity in the frequencies and types of mutation in connexin 26 gene.     

Prevalence of GJB6 mutations in Chinese patients with non-syndromic hearing loss

Objective

To investigate the distribution of GJB6 mutations in Central Chinese population with non-syndromic hearing loss.

Method

Totally 655 hearing impaired patients in Hubei province of China were screened for del(GJB6-D13S1830) deletions by using multiplex PCR and sequencing of GJB6 whole coding region.

Result

The del(GJB6-D13S1830) and other mutations in GJB6 gene were not observed in our study cohort.

Conclusion

The results suggest that GJB6 mutations is not a common cause among Central Chinese population and screening for the mutations of GJB6 can be ranked as unconventional deaf gene test for this population.     

Occurrence of del(GIB6-D13S1830) mutation in Italian non-syndromic hearing loss patients carrying a single GJB2 mutated allele

Molecular screening for GJB2 (connexin 26) mutations represents the standard diagnostic approach for the genotype definition of non-syndromic deafness. Nevertheless, a single GJB2 pathogenic mutation is detectable in a relevant number of cases, therefore failing to explain the phenotype. We aimed at assessing the occurrence of the recently described del(GIB6-D13S1830) mutation, occurring in the connexin 30 gene, in a group of Italian hearing-impaired patients carrying a single GJB2 mutated allele. A total of 59 non-syndromic hearing loss (NSHL) patients were screened for GJB2 mutations. Among these, nine NSHL patients were found to be heterozygous for a single GJB2 mutation. These patients, heterozygotes for different GJB2 mutated alleles (35delG, L90P, M34T, V153I), together with 11 additional 35delG/neg cases previously described, were studied for the presence of the del(GIB6-D13S1830) mutation. Two double heterozygotes del(GIB6-D13S1830)/35delG were identified. In both cases the degree of hearing loss was profound. Furthermore, GJB2 molecular screening led to the identification of a novel change (T55G) occurring in compound heterozygosity with the V37I mutation. In conclusion, our data suggest a significant frequency of del(GIB6-D13S1830) mutation in Italian hearing-impaired subjects (10% of unexplained GJB2 heterozygotes) similar to that reported in other European countries.     

GJB2 mutations in hearing impairment: identification of a broad clinical spectrum for improved genetic counseling

OBJECTIVES/HYPOTHESIS: Hearing impairment has a high prevalence affecting approximately 1 in 1000 newborn children. Alterations in the gap junction protein beta 2 (GJB2) and gap junction protein beta 6 (GJB6) are associated with nonsyndromic hearing impairment and should have a significant impact on genetic counseling. STUDY DESIGN: Various cases of nonsyndromic hearing impairment were screened for alterations in GJB2 and GJB6 in this clinical study. METHODS: The prevalence of mutations in GJB2 encoding for connexin 26 in a patient group with nonsyndromic hearing impairment comprising 45 families and 57 sporadic cases was initially determined by sequencing. The role of GJB2 was then assessed in individuals with hearing impairment (3 families and 20 sporadic cases) who are usually excluded from analysis because of the presence of additional symptoms or in cases in which a role for nongenetic factors cannot be eliminated. In hearing-impaired individuals with heterozygous GJB2 mutations the recently identified 342-kb deletion truncating GJB6 called del(GJB6-D13S1830) as a digenetic component in hearing impairment was excluded by polymerase chain reaction. RESULTS: Autosomal recessively inherited GJB2 mutations induced hearing impairment in 25.5% of individuals in the nonsyndromic hearing impairment group. GJB2 alterations were also seen in 17.4% of individuals in whom additional symptoms or a role for nongenetic involvement could not be excluded. In all, 15 different alterations in GJB2 were detected, including the previously unknown 154G>C, 557C>T, and 682C>T mutations, and these were correlated to clinical parameters. CONCLUSION: Improved genetic counseling can be performed by screening for GJB2 alterations in patients with nonsyndromic hearing impairment including patients within groups for which a role for exogenetic factors cannot be excluded. Specific genetic counseling for GJB2-linked hearing impairment in heterozygotes will depend on future research.     

A study of GJB2 and delGJB6-D13S1830 mutations in Brazilian non-syndromic deaf children from the Amazon region

Hearing impairment affects about 1 in 1000 newborns. Mutations in the connexin 26 (GJB2) gene rank among the most frequent causes of non-syndromic deafness in different populations, while delGJB6-D13S1830 mutation located in the DFNB30 locus is known to cause sensorineural hearing loss. Despite the many studies on the involvement of GJB2 mutations in hearing impairment in different populations, there is little information on genetic deafness in Brazil, especially in the Amazon region.ObjectiveTo determine the prevalence of GJB2 mutations and delGJB6-D13S1830 in 77 sporadic non-syndromic deaf patients.MethodThe coding region of the GJB2 gene was sequenced and polymerase chain reaction was performed to detect the delGJB6-D13S1830 mutation.ResultsMutant allele 35delG was found in 9% of the patients (7/77). Mutations M34T and V95M were detected in two distinct heterozygous patients. Non-pathogenic mutation V27I was detected in 28.6% of the patients (22/77). None of the deaf patients carried the delGJB6-D13S1830 mutation.ConclusionMutant alleles on gene GJB2 were observed in 40% (31/77) of the subjects in the sample. Pathogenic variants were detected in only 12% (9/77) of the individuals. More studies are required to elucidate the genetic causes of hearing loss in miscegenated populations.     

Prevalence of the GJB2 mutations and the del(GJB6-D13S1830) mutation in Brazilian patients with deafness

Mutations in the GJB2 gene are the most common cause of sensorineural non-syndromic deafness in different populations. One specific mutation, 35delG, has accounted for the majority of the mutations detected in the GJB2 gene in many countries. The aim of this study was to determine the prevalence of GJB2 mutations and the del(GJB6-D13S1830) mutation in non-syndromic deaf Brazilians. The 33 unrelated probands were examined by clinical evaluation to exclude syndromic forms of deafness. Mutation analysis in the GJB2 gene and the testing for the del(GJB6-D13S1830) were performed in both the patients and their family members. The 35delG mutation was found in nine of the probands or in 14 of the mutated alleles. The V37I mutation and the del(GJB6-D13S1830) mutation were also found in two patients, both are compound heterozygote with 35delG mutation. These findings strengthen the importance of genetic diagnosis, providing early treatment, and genetic counseling of deaf patients.     

gjb2 mutation spectrum in inner mongolia and its comparison with other asian populations

Mutations in the GJB2 gene are the most frequently found mutations in patients with nonsyndromic hearing impairment. However, the mutation spectrum and prevalence of mutations vary among different ethnic groups. Every year, 30,000 babies are born with congenital hearing impairment in China. In order to provide appro-pilate genetic testing and counseling to the family, we investigated the molecular etiology of nonsyndromic deafness in 135 unrelated school children attending Chifeng Municipal Special Education School in Inner Mongolia, China. The coding exon of the GJB2 gene was PCR amplified and sequenced. In addition, the 12S rRNA gene and tRNAser UCN of mitochondrial genome were screened for mutations responsible for hearing impairment. Sixty four GJB2 mu-tant alleles, including 60 confirmed pathogenic alleles and 4 unclassified variants, were identified in 31.1% (42/135) of the subjects. Twenty two subjects carried two pathogenic mutations and 20 subjects carried one mutant allele, in-cluding one subject with one autosomal dominant mutation. The 235delC was the most common mutation account-ing for 65.6%(42/64) GJB2 mutant alleles. When compared to other Asian populations, our subject cohort had high-er frequency of 235delC mutation than the Japanese population. The GJB2 mutant alleles account for 23.7% (64/270) of all chromosomes responsible for nonsyndromic heating impairment. Testing of the 4 most prevalent deleterious frame shift mutations(235delC, 299_300delAT, 176191_del16, and 560_605ins46) in this cohort detect-ed 90% of all GJB2 mutant alleles. These results demonstrate that effective genetic testing of the GJB2 gene for pa-tients and families with nonsyndromic hearing impairment is possible in the Chinese population. Since the most common 309kb GJB6 deletion is not detected and only one 1555 A>G mutation in mitochondrial DNA is detected in our patients, investigation of mutations in other nuclear genes and/or environmental factors responsible for non-syndromic heating impairment in the Chinese population is necessary.