常见耳聋相关基因在非综合征型聋中的研究进展

耳聋是一种很普遍的感音神经功能紊乱的耳部疾病,是人类最常见的致残原因之一,严重影响人类生活质量。在耳聋患者中遗传性聋约占60%。遗传性聋可分为综合征型聋和非综合征型聋。综合征型聋是指以耳聋合并其他临床症状的遗传综合征,而非综合征型聋是指以单一听力缺失为临床症状的遗传性疾病。本文对非综合征型聋的遗传性基因研究进展做一综述,以期从分子水平探讨耳聋的病因及发病机制。     

Wolfram综合征Ⅰ型基因异质性突变引起低频非综合征型聋

目的分析常染色体显性遗传的低频非综合征感音神经性聋与Wolfram综合征Ⅰ型（wolfram syndrome 1，WFSl）基因WFS1的关系以及WFS1基因突变特性，从分子遗传学水平探讨其致病机理。方法收集6个低频非综合征感音神经性聋家系中28例成员以及140例健康对照个体的外周血DNA样本；采用聚合酶链反应，直接序列分析和限制性片断长度多态性分析方法，进行WFS1基因编码区的筛查。结果发现2个家系6例耳聋成员测序结果异常。1个家系发现所有耳聋患者WFS1基因的编码区2379位碱基G杂合性改变成A，导致错义突变；另1家系先证者WFS1基因的编码区2016位碱基G杂合性改变成T，先证者之妹2776位碱基G杂合性改变成A，导致错义突变；先证者之母为一Wolfram综合征伴有心理障碍患者，发现其为2016位2776位碱基复合型错义突变。这2个家系听力正常者及健康对照者中无此突变。结论WFS1基因异质性突变引起低频非综合征感音神经性聋，主要突变为错义突变，遗传咨询和基因检测对该类型耳聋诊治具有指导意义。     

非综合征型聋患者及家庭成员耳聋基因MYO15A检测及其产前诊断意义北大核心CSCD

目的分析2例汉族非综合征型聋(nonsyndromic sensorineural hearingloss,NSHL)患者及家庭成员中耳聋基因MYO15A的突变位点,探讨MYO15A基因检测用于产前诊断的可行性。方法采集2例汉族非综合征型感音神经性聋患儿(均为男性,年龄分别为2岁8个月和3岁6个月)及两个家庭(编号为NSHL-01和NSHL-02)成员血样并记录临床资料。应用芯片捕获高通量测序(targeted genomic capturing and next-generation sequencing,targeted DNA-Hiseq)对2例NSHL患儿进行127个耳聋基因检测,获得变异序列后,针对所检出变异序列对家庭成员和健康对照个体的MYO15A基因序列进行变异验证分析,确定致病性突变后,使用sanger测序法对NSHL-02家庭中的高危胎儿进行孕中期产前诊断。结果在NSHL-01家庭的患儿中检测出MYO15A基因复合杂合突变,即:内含子18亚区c.5134-1G>A(p.-)杂合突变和外显子20亚区c.5324A>C(p.Gln1775Pro)杂合突变,本地收集的200例正常测序样本中无关于此SNP的频率信息;患儿的父亲携带c.5134-1G>A杂合突变,而患儿的母亲携带c.5324A>C杂合突变。在NSHL-02家庭的患儿检出MYO15A基因复合杂合突变,第二外显子c.374delG(Arg125ArgfsX319)杂合突变和外显子56亚区c.9358C>T(p.Gln3120Ter)杂合突变,本地收集的200例正常测序样本中无关于此SNP的频率信息;患儿的父亲携带c.9358C>T杂合突变,而患儿的母亲携带c.374delG杂合突变;该家庭高危胎儿携带c.9358C>T杂合突变,不携带c.374delG杂合突变,出生后表型正常。结论 MYO15A基因内含子18亚区c.5134-1G>A杂合突变和外显子20c.5324A>C杂合突变,及第二外显子c.374delG杂合突变和外显子56亚区c.9358C>T杂合突变是2个NSHL家庭的致病原因,芯片捕获高通量测序及数据分析技术可对2个NSHL家庭进行有效的基因诊断,结合sanger技术可进行产前诊断。     

非综合征型聋患者耳聋相关基因检测结果分析

目的 探讨遗传性耳聋基因芯片用于非综合征型聋患者检测的临床意义.方法 采用遗传性聋基因芯片试剂盒对177例非综合征型耳聋患者基因组DNA的GJB2、SLC26A4、GJB3和mtDNA12s rRNA四个耳聋相关基因的9个致聋突变位点进行榆测;对部分携带SLC26A4基因突变的患者进行颞骨CT扫描;选取26位听力正常且...     

Wolfram 综合征I型基因异质性突变引起低频非综合征型聋

目的分析常染色体显性遗传的低频非综合征感音神经性聋与Wolfram 综合征Ⅰ型(wolfram syndrome 1, WFS1)基因WFS1的关系以及WFS1基因突变特性,从分子遗传学水平探讨其致病机理.方法收集 6个低频非综合征感音神经性聋家系中28例成员以及140例健康对照个体的外周血DNA样本;采用聚合酶链反应,直接序列分析和限制性片断长度多态性分析方法,进行WFS1基因编码区的筛查.结果发现2个家系6例耳聋成员测序结果异常.1个家系发现所有耳聋患者WFS1基因的编码区2379位碱基G杂合性改变成A,导致错义突变;另1家系先证者WFS1基因的编码区2016位碱基G杂合性改变成T,先证者之妹2776位碱基G杂合性改变成A,导致错义突变;先证者之母为一Wolfram综合征伴有心理障碍患者,发现其为2016位2776位碱基复合型错义突变.这2个家系听力正常者及健康对照者中无此突变.结论 WFS1基因异质性突变引起低频非综合征感音神经性聋,主要突变为错义突变,遗传咨询和基因检测对该类型耳聋诊治具有指导意义.     

新疆地区非综合征型聋患者耳聋相关基因检测结果分析

目的探讨新疆地区非综合征型耳聋患者常见耳聋基因突变热点,为该地区更好地开展耳聋基因诊断工作提供参考。方法通过问卷、健康体检及听力检测筛选出新疆地区399例非综合征型耳聋患者为研究对象,所有受检者均采集外周血并提取基因组DNA,应用分子生物学方法检测GJB2(c.35delG,c.167delT,c.176_191del16,c.235delC,c.299_300delAT)、SLC26A4(c.281C>T,c.589G>A,c.IVS7-2A>G,c.1174A>T,c.1226G>A,c.1229C>T,c.IVS15+5G>A,c.1975G>C,c.2027T>A,c.2162C>T,c.2168A>G)、mtDNA12SrRNA(c.1494C>T,c.1555A>G,c.1585A>G,c.1047A>G,c.1095T>C,c.960_961insC/c.961delT)基因22个位点突变情况。结果399例非综合征型耳聋患者中GJB2、SLC26A4、mtDAN12SrRNA基因的突变携带率分别为11.28%(45/399)、10.78%(43/399)、4.76%(19/399),致病突变率分别为6.52%(26/399)、3.76%(15/399)、3.51%(14/399)。c.235delC和c.IVS7-2A>G在汉族(16/92,11/92)和维吾尔族(18/273,10/273)中都是突变热点,在汉族中c.2168A>G也呈现突变热点趋势,而在维吾尔族中c.1174A>T、c.35delG、c.2027T>A等多个位点都呈现出突变热点的趋势。在汉族c.235delC(χ^2=9.498,P=0.002)、c.IVS7-2A>G(χ^2=8.729,P=0.003)和c.2168 A>G(P=0.001)突变率高于维吾尔族。结论GJB2、SLC26A4、mtDNA12SrRNA为新疆非综合征型耳聋常见致病基因,c.235delC和c.IVS7-2A>G是汉族和维吾尔族突变热点,汉族中c.235delC、c.IVS7-2A>G和c.2168A>G突变率显著高于维吾尔族。     

非综合征型聋相关基因研究进展

非综合征型聋是由遗传因素引起的最常见的感音神经性聋。深入了解耳聋分子病因学的特点,不仅有助于我们对耳聋患者进行病因诊断、遗传咨询、产前诊断和新生儿听力筛查,还可以及时干预和治疗,为防聋治聋提供帮助。目前人类研究发现的致聋基因已有百余种,中国最常见的致聋基因为GJB2、SLC26A4、线粒体DNA12S rRNA和GJB3。本文对非综合征型聋相关基因的研究进展予以综述。     

陕西省800例非综合征型聋患者常见致聋基因突变分析

目的：分析陕西省非综合征型聋患者常见耳聋基因突变方式及频率,了解其耳聋发病的分子机制。方法采集陕西省800例非综合征型聋患者外周血,提取基因组DNA ,采用聚合酶链式反应（PCR）扩增GJB2基因、GJB3基因、SLC26A4基因以及线粒体12S rRNA 1494和1555位点进行直接测序,序列与NCBI网站公布的标准序列进行比对分析。结果800例非综合征型聋患者中,共353例（44．13％）患者携带耳聋致病基因突变,其中153例（19．13％）携带GJB2基因双等位基因突变,GJB2基因最常见的突变方式为235delC ,检出率为13．5％（216／1600）;123例（15．38％）携带SLC26A4基因双等位基因突变,SLC26A4基因最常见突变方式为IVS7－2A＞G ,检出率为7．44％（119／1600）;1例携带线粒体12S rRNA1494C＞ T均质性突变,15例携带1555A＞G均质性突变;2例患者携带GJB3基因c ．538C＞ T杂合突变。294例（36．75％,294／800）患者由上述基因突变导致耳聋。结论陕西省非综合征型聋患者中,GJB2基因以及SLC26A4基因的突变携带率与全国以及西北地区平均水平较为一致,而线粒体基因突变的携带率偏低。     

与Connexin26基因突变相关的综合征耳聋和非综合征耳聋

Connexin26基因其编码的产物为一种缝隙连接蛋白，组成的质膜通道蛋白，在细胞间的连接和递质的传递中起着重要的作用。近年来的研究发现此基因的突变与遗传性综合征耳聋和非综合征耳聋密切相关，对这一基因的研究可使我们对耳聋的致病机理有更加深入的了解。     

CX31.1基因在遗传性聋家系中的突变分析

目的：通过对非综合征型聋家系进行CX31．1基因的突变分析,以鉴定CX31．1基因是否为遗传性聋的致病基因。方法：通过对从全国10多个省收集到的遗传性聋家系61个,其中常染色体隐性非综合征型聋家系37个,常染色体显性非综合征型聋家系24个的106例成员及50例正常人进行聚合酶链反应(polymerasc chain reaction,PCR)及直接测序,对遗传性聋个体进行CX31．1基因的突变检测。结果：发现CX31．1的同义突变1种,多态1种,内含子缺失2种。结论：我们目前的检测虽未能证明CX31．1基冈突变是上述聋家系的致病基因,但根据基因结构分析该基因与遗传性聋的关系不能排除,有待收集更多的家系做进一步的研究。     

Connexin26 mutations associated with nonsyndromic hearing loss

OBJECTIVE: Mutations in the GJB2 gene are a major cause of autosomal recessive and sporadic types of congenital deafness. The 35delG mutation is the most frequent type of mutation in white populations. However, several other forms were reported, such as 167delT among Ashkenazi Jews and R143W in Africans. The present study investigated the mutations of connexin26 (Cx26) found in patients with nonsyndromic hearing loss (NSHL) and newborns in the Korean population. STUDY DESIGN: The sequencing data for 147 unrelated patients with congenital NSHL and 100 audiologically screened newborns were included in this prospective study. METHODS: Genomic DNA samples from all patients and newborns were sequenced in both directions for detection of Cx26 mutations. RESULTS: Thirteen different types of mutations were found in the patients and newborns. V27I and E114G are the popular types of polymorphic mutations in both groups. 235delC-deletion and frameshift--was detected in patients (15 in 294 alleles) and newborns (1 in 200 alleles). 35delG was rarely found in both group. In addition to above mutations, several types of mutations--S85P, K41R, S72C, V84A, 176-191del, and 299-300del-were identified. The family study of the 235delC showed a typical autosomal recessive trait of NSHL in their audiological evaluation of hearing threshold. CONCLUSION: The frequency of 235delC allele showed much higher in the patients (5%) than in newborns (0.5%). We rarely found 35delC mutant in both groups. These results suggest that the different types of Cx26 mutations affect autosomal recessive NSHL according to ethnic background.     

Connexin 26 and connexin 30 mutations in children with nonsyndromic hearing loss

OBJECTIVES/HYPOTHESIS: Mutations in the connexin 26 (Cx26) or gap junction beta 2 gene are the leading cause of hereditary nonsyndromic sensorineural hearing loss in Caucasians. The Cx26 coding region of 68 children with nonsyndromic sensorineural hearing loss was sequenced to determine the frequency and type of Cx26 mutations in this population. Screening was also performed for a common connexin 30 (Cx30) or gap junction beta 6 mutation (del [GJB6-D13S1830]). Children also underwent audiological testing to determine whether any correlation exists between Cx26 mutations and severity of hearing loss. STUDY DESIGN: In all, 68 children with nonsyndromic sensorineural hearing loss were screened for Cx26 and Cx30 mutations by polymerase chain reaction and direct sequencing. METHODS: Genomic DNA was amplified by polymerase chain reaction using primers that flank the entire Cx26 coding region. Screening for the 342-kb Cx30 deletion was performed using primers that amplified the breakpoint junction of the deletion. The amplicons were then sequenced in both directions and analyzed for mutations. Audiometric testing, including pure-tone audiometry and auditory evoked brainstem response, was also performed to determine the degree of hearing loss. RESULTS: Twenty-seven of 68 children tested had mutations in Cx26 with 35delG being the most prevalent. Ten additional Cx26 mutations were detected including a novel compound heterozygote. Two children were heterozygous for the Cx30 del (GJB6-D13S1830) mutation. CONCLUSION: Cx26 and Cx30 mutations were present in 41.2% of children tested in the study population. Audiometric data supported previous studies demonstrating a greater degree of hearing loss in subjects who are homozygous for the 35delG mutation.     

ACEMg supplementation ameliorates progressive Connexin 26 hearing loss in a child

Mutations in the gene encoding Connexin 26 are the most common cause of genetic hearing loss. The hearing loss is typically stable but may be progressive. The reason for progression is unknown. Antioxidants have been associated with attenuation of hearing loss from other insults. One antioxidant regimen consists of beta-carotene (metabolized to vitamin A), vitamin C, vitamin E, and magnesium (ACEMg). We present a child with Connexin 26 related hearing loss who experienced progressive hearing loss over 7 years of observation. He was given ACEMg daily for 3 years, during which time his progressive hearing loss was ameliorated.     

Familial nonsyndromic hearing loss with incomplete partition type II caused by novel DSPP gene mutations

Background: Familial nonsyndromic hearing loss (NSHL) with incomplete partition type II (IP-II) is a very rare condition.

Aims/Objectives: To determine the audiological feature, inheritance patterns and genetic etiology of familial NSHL with IP-II in a Chinese family with eight family members.

Material and methods: Clinical data were collected from all eight family members, selected deafness genes were sequenced in proband and whole genome sequencing of seven family members was performed.

Results: The proband were a pair of male nonidentical twins (III:1, III:2). Three patients in this family, including the twins and their father (II:1), were diagnosed with bilateral NSHL with IP-II, and no mutation was found in the genes of SLC26A4, GJB2, GJB3, mitochondrial 12S rRNA, and MITF. Whole genome sequencing data indicated de novo mutations of the gene DSPP, c.3085A?>?G and c.3087C?>?T, which resulted in p.N1029D and co-segregated with deafness phenotype, were the underlying genetic etiology.

Conclusion and significance: Familial NSHL with IP-II is extremely rare. In this family, de novo DSPP gene mutations, were considered to be the most probable genetic etiology. And this is the first report to reveal DSPP gene mutations leading to familial NSHL with IP-II.     

A novel missense mutation in the Connexin 26 gene associated with autosomal recessive nonsyndromic sensorineural hearing loss in a consanguineous Tunisian family

Nonsyndromic sensorineural hearing impairment is inherited in a predominantly autosomal recessive manner in up to 70% of cases. The gene more often involved is GJB2, encoding the gap junction protein Connexin 26. We report here a novel missense mutation in the GJB2 gene found in a Tunisian family. A homozygous change C/G at nucleotide 263 was detected in the 4-year-old girl of this family, affected by congenital moderate hearing loss. This transversion leads to the replacement of a highly conserved alanine with glycine at codon 88 (A88G). The consanguineous parents of the child are healthy carriers of the mutation.     

Genetic counseling and prenatal diagnosis for hereditary hearing loss in high-risk families

Objective

Genetic counseling and prenatal diagnosis are very necessary and accurate to detect hereditary hearing loss, especially in high-risk families. Prenatal diagnosis is testing for diseases or conditions in fetuses before born, which gives parents the chance to prepare psychologically, financially and medically for the probable health and educational needs of the affected neonates.

Methods

54 unrelated families with children affected with non-syndromic sensorineural hearing loss were enrolled in the study and received genetic analysis with microarray and DNA sequencing technologies. Genetic counseling was provided to each participating families, and prenatal diagnosis was given to those at risk and would like to know their fetuses’ genotypes and probable hearing statuses.

Results

Half the cases in the present study were diagnosed with confirmed pathogenic mutations and clear inheritance patterns. After receiving genetic counseling, 24 carrier couples with pathogenic mutations chose to proceed prenatal diagnosis, the results of which were in accordance with the pregnancy outcomes. Infants prenatally detected to be monoallelic mutation carriers and those harbored neither deafness-causing mutations form their parents passed newborn hearing screening and six-month follow-ups, while neonates prenatally detected to be carriers of diallelic or compound heterozygous mutations developed hearing loss after birth.

Conclusions

With appropriate genetic counseling and support services provided, the genetic testing and the prenatal diagnosis of hearing loss were valued by carrier couples for the information provided for future family planning and probably the preparation for the health and educational needs of the affected neonates.     

Identification of novel variants in the Myosin VIIA gene of patients with nonsyndromic hearing loss from Taiwan

Objective

To determine whether variants of exons 7, 11, 22 and 28 of the MYO7A gene are causes of nonsyndromic deafness in Taiwanese.

Methods

We screened a total of 331 unrelated Taiwanese individuals (age range, 4-22 years), including 231 patients with severe to profound nonsyndromic hearing loss and 100 individuals with normal hearing. Genomic DNA was extracted from peripheral blood leukocytes and then subjected to PCR to amplify selected exons and flanking introns of the MYO7A gene; the amplified products were screened for base mutations by autosequence. Data from the two groups were then compared using the chi-square (χ²) test.

Results

The analysis revealed six variants in 3 out of 4 screened exons and flanking intronic sequences of the MYO7A gene (exons 7, 11, and 22). Three missense variants were found only in patients with hearing loss and were heterozygous, including Arg206Cys, Arg206His and Thr381Met. A variant, c.IVS22+58G>A, was found in intron 22 of the MYO7A gene from both patients and control group. Allele frequencies of c.IVS22+58G>A were shown to be significant between the two groups using χ² test (P < 0.05).

Conclusion

Our results indicate that Arg206 and Thr381 residues in the motor head region of MYO7A protein are critical sites and the mutations of these residues may lead to the development of nonsyndromic deafness.     

国人conneXin 2 6基因突变与先天性感音神经性耳聋的相关性研究

目的探讨国人耳聋人群中connexm26基因的突变频率和位点.方法收集15例有遗传性耳聋家族史的病例和252例散发性先天性耳聋病例血液样本,使用PCR-SSCP方法分析connexin26基因编码区突变.同时采用PSDM和BsBsiYI酶切的方法,直接检测异常connexin26基因35delG的突变.结果检出突变样本46例,其中散发耳聋患者中38例,突变率为15.1%;有家族史的聋儿15例中8例,突变率为53.3%.46例中5份有相似的异常电泳带,PCR产物直接测序,其形式为79位G→A的突变;另外在散发耳聋患者中还发现2例251delT和233delC,PDSM分析未发现有35delG的突变.结论国人先天性耳聋患者中存在着connexin26基因的高突变率,但突变热点与国外报道的不同,推测connexin26基因突变有明显的种族特异性.