两个常染色体显性遗传先天性白内障家系突变热点筛查

[目的]对2个常染色体显性遗传先天性白内障中国家系进行基因突变热点筛查,以了解这两个家系的先天性白内障是否与文献报道的17个突变热点相关.[方法]对两个家系共20名成员(包括患者11人,非患者9人)抽取外周血提取基因组DNA,针对截至2003年1月为止国外文献报道的与常染色体显性遗传先天性白内障发病相关的10个基因上的17个突变热点,包括CRYAA(ARG116CYS),CRYAB(del450A),CRYBA1(EX3-4 DEL),CRYBB2(GLN155TER),CRYGC(THR5PRO,5-BP DUP at NT226),CRYGD(ARG14-CYS,PRO23THR,ARG58HIS,ARG36SER),GJA3(ASN63SER,PRO187LEU),GJA8(GLU48LYS,PRO88SER),BFSP2(ARG287TRP)及MIP(GLU134GLY,THR138ARG),设计引物使PCR扩增片段涵盖上述热点,对扩增产物进行序列分析,检测这11名患者在突变热点上是否有相应的序列改变.[结果]20名被检者的10个基因片段序列与GenBank发表序列相同,在17个突变热点均未发现相应基因突变.[结论]初步排除这个家系的先天性白内障与17个突变热点相关.     

A missense mutation S228P in the CRYBB1 gene causes autosomal dominant congenital cataract

Background Congenital cataract is a highly heterogeneous disorder at both the genetic and phenotypic levels. This study was conducted to identify disease locus for autosomal dominant congenital cataracts in a four generation Chinese family. Methods Family history and clinical data were recorded. All the members were genotyped with microsatellite markers which are close to the known genetic loci for autosomal congenital cataracts. Two-point Lod scores were obtained using the MLINK of the LINKAGE program package （vet 5.1）. Candidate genes were amplified by polymerase chain reaction （PCR） and direct cycle sequencing. Results The maximum Lod score of Zmax=2.11 was obtained with three microsatellite markers D22S258, D22S315, and D22S1163 at recombination fraction θ= 0. Haplotype analysis showed that the disease gene was localized to a 18.5 Mbp region on chromosome 22 flanked by markers D22S1174 and D22S270, spanning the β-crystallin gene cluster. A c.752T→C mutation in exon 6 of CRYBB1 gene, which resulted in a heterozygous S228P mutation in predicted protein, was found to cosegregate with cataract in the family. Conclusions This study identified a novel mutation in CRYBB1 gene in a Chinese family with autosomal dominant congenital cataract. These results provide strong evidence that CRYBB1 is a pathogenic gene for congenital cataract.     

GJA8基因错义突变致先天性白内障一家系遗传分析

  目的  通过使用外显子测序定位分析一先天性白内障家系中GJA8基因致病错义突变。  方法  对2020年6月在昆明医科大学第二附属医院就诊的一个先天性白内障家系全体成员进行详细的临床眼科检查及全身查体。采集先证者及6个亲属外周血并提取基因组DNA,应用全外显子测序筛查可疑致病基因,使用生物信息工具对可疑基因突变进行致病性分析,并对家系全部成员进行Sanger测序验证候选致病突变。  结果  外显子测序及生物信息学分析显示GJA8基因存在一个错义突变c.593G > A,p.R198Q,导致其第198位氨基酸残基由谷氨酰胺取代了原有的脯氨酸。氨基酸保守性分析显示该突变影响的氨基酸在物种间高度保守。在家系全部受检者中进行的Sanger测序结果表明该突变与疾病表型共分离,可以认定该突变是该突变为该家系的致病性突变,系谱分析显示该突变所致先天性白内障呈现常染色体显性遗传。  结论  位于GJA8基因的错义突变c.593G > A,p.R198Q是导致该家系出现先天性白内障的遗传病因,遗传方式为常染色体显性遗传。     

Autosomal dominant coralliform cataract related to a missense mutation of the γD-crystallin gene

Background Congenital cataract is a sight-threatening disease that affects about 1 -6 cases per 10 000 live births and causes 10% -30% of all blindness in children. About 25% of all cases are due to genetic defects. We identified autosomal dominant congenital coralliform cataracts-related genetic defect in a four-generation Chinese family.Methods Complete ophthalmological examinations were performed prior to lens extraction. Lens samples were then studied by electron microscopy. Genomic DNA from family members were examined using whole-genomic linkage analysis, with two-point logarithm of odds (LOD) scores calculated using the Linkage program package (version 5. 1 ). Mutation analysis of candidate genes was performed by direct sequencing. Finally, a three-dimensional protein model was predicted using Swiss-Model (version 2.0).Results Eleven of the 23 examined individuals had congenital cataracts. Ultrastructure studies revealed crystal deposits in the lens, and granules extensively dispersed in transformed lens fiber cells. The maximum two-point LOD score, 3. 5 at θ = 0. 1, was obtained for the marker D2S,325.Mutation analysis of the γ-crystallin (CRYG) gene cluster identified a mutation (P23T) in exon 2 of γD-crystallin (CRYGD). Protein structure modeling demonstrated that the P23T mutation caused a subtle change on the surface of the γD protein.Conclusions The results suggest that the coralliform cataract phenotype is due to a mutated CRYGD gene, and that this sequence change is identical to one reported by Santhiya to be related to another distinct clinical condition, lamellar cataract. This study provides evidence that this same genetic defect may be associated with a different phenotype. This is the first report identifying the genetic defect associated with an autosomal dominant congenital coralliform cataract.     

常染色体显性先天性白内障大家系致病基因定位的初步研究

目的:报道1个涉及5代17例患者的常染色体显性先天性白内障(ADCC)大家系,并进行致病基因的定位. 方法:对家系中8例患者进行眼科检查后明确临床表型,并提取所有血样的基因组DNA.首先对已报道的中国ADCC家系致病位点(9个基因的16个突变位点)进行DNA测序,然后根据已报道的17个ADCC候选基因和13个染色体区域,选取27个微卫星分子标记,应用LINKAGE软件进行连锁分析. 结果:8例患者均为先天性核性白内障.直接DNA测序未发现有已报道的中国家系基因突变.所选取的27个微卫星分子标记与该家系致病基因均不连锁. 结论:该ADCC家系致病基因不在已报道的17个ADCC候选基因和13个染色体区域,该家系中可能存在一个新的ADCC致病基因.     

基于基因诊断的耳聋遗传咨询、指导作用的初步观察

目的利用基因诊断方法分析耳聋家庭的分子致病机制,并通过产前诊断进行胎儿耳聋基因型的鉴别,为不同发病原因的耳聋家庭提供准确的遗传咨询、指导和干预。方法共有5个耳聋家庭参加研究,其中3个家庭（家系1～3）均为父母听力正常,这3个家庭均有一个子女为中重度感音神经性聋患儿,受检时母亲均怀孕（6～18周）。1个家庭（家系4）夫妇均为聋哑人;1个家庭（家系5）丈夫为听力正常个体、妻子为重度耳聋个体。所有受检患者均采集外周血并提取DNA,进行GJB2、SLC26A4（PDS）基因分析和线粒体DNA 1555位点突变检测。结果家系1先证者携带GJB2复合突变,父母为携带者,产前诊断显示胎儿仅携带一个父系突变,出生后随访听力正常;家系2先证者携带SLC26A4（PDS）复合突变,父母为携带者,产前诊断显示胎儿仅携带一个父系突变,出生后随访听力正常;家系3先证者及其父母均未检出常见耳聋突变,第二胎出生后随访听力正常;家系4丈夫为GJB2 235delC纯合突变,妻子为线粒体DNA A1555G突变阳性,建议其后代严格禁用氨基糖甙类抗生素;家系5妻子为SLC26A4（PDS）复合突变,丈夫为SLC26A4（PDS）杂合突变携带者,预测其后代患大前庭水管综合征（EVAS）的风险达到50％。结论耳聋基因诊断配合产前诊断在预防耳聋家庭再次生育聋儿上可以起明确的指导作用,并可引入正确的干预机制。     

先天性肾性尿崩症患者精氨酸加压素受体2基因突变的检测分析

目的　探讨并检测先天性尿崩症患者精氨酸加压素受体 2 (AVPR2 )基因突变的临床意义。方法　对临床诊断为先天性尿崩症的 7例患者及 2 4名亲属的血液样本 ,提取基因组DNA ,通过PCR扩增AVPR2基因的 6个片断 ,用单链构象多肽性 (SSCP)进行基因突变的筛查 ,再对异常条带进行DNA测序证实基因的突变。结果　在 7例先天性尿崩症的患者中 ,发现 6例患者存在 5种类型共8个AVPR2的突变点 ,2例患者有AVPR2基因的双点突变 ,其余为单突变点 ,1例患者的母亲为AVPR2基因突变的携带者。其中 4个突变点国际尚未报道 ,它们分别是 :G 4 6 9 4 93del 2 4 ,G 5 4 1insT ,G 4 6 2delC和G 935T >C ,分别导致AVPR2受体蛋白A37 L4 4del(缺失突变 ) ,A6 1G 190X(插入移码突变 ,无义突变 ) ,P34R 36X(缺失移码突变和无义突变 ) ,C192R(错义突变 )。结论　发现了 4种新的AVPR2基因突变类型。采用PCR SSCP的方法可以对尿崩症的患者进行基因突变的粗筛 ,最后经过DNA测序可以做出基因突变的诊断。     

先天性无痛无汗症家系致病基因的研究

目的明确遗传性感觉和自主神经病Ⅳ型[又称先天性无痛无汗症(CIPA)]患者的临床诊断。对该家系成员NTRK1基因及FAM134B基因进行外显子测序,明确该家系的致病基因状态。方法采集CIPA患者皮肤及皮下组织,进行HE染色及免疫组织化学检测,明确该CIPA患者诊断;通过外显子测序的方法,检测该家系NTRK 1基因和FAM134B基因突变情况,判断其是否为该CIPA家系的致病基因。结果该患者具有全身皮肤无汗、高热、痛觉消失及发育迟缓等典型CIPA临床症状,其表皮及真皮无毛囊、汗腺萎缩,皮肤周围神经无髓鞘,同时伴随细小有髓鞘纤维缺失。检测CIPA家系NTRK 1和FAM134B基因,发现FAM134B基因无有意义突变,患者和父亲以及弟弟出现NTRK1基因内含子2中Indel突变,患者和母亲NTRK1基因外显子15存在突变。结论通过病史采集、痛觉和温度觉实验及皮肤病理活检等,可以临床确诊该患者为CIPA。通过外显子测序方法,发现NTRK1基因内含子2中Indel突变和外显子15中679位氨基酸缬氨酸GTG(缬氨酸,V)→ATG(蛋氨酸,M)突变,推测在此两种突变共同作用下,可能会导致该疾病的发病。FAM134B基因未发现有意义突变,可能存在其他致病基因,需要进一步的研究。     

Congenital deafness: high prevalence of a V37I mutation in the GJB2 gene among deaf school children in Alor Setar

Twenty percent of all childhood deafness is due to mutations in the GJB2 gene (Connexin 26). The aim of our study was to determine the prevalence and spectrum of GJB2 mutations in childhood deafness in Malaysia. We analyzed the GJB2 gene in 51 deaf students from Sekolah Pendidikan Khas Alor Setar, Kedah. Bidirectional sequencing indicates that 25% of our childhood deafness has mutation in their GJB2 gene. Sixty two percent of these children demonstrate V37I missense mutation. Interestingly, V37I mutation in the GJB2 gene have been reported as polymorphism in Western countries, however in our country it behaved as a potentially disease-causing missense mutation, causing childhood deafness as it was not found in the normal control.     

GJB2 (Cx26) gene mutations in Chinese patients with congenital sensorineural deafness and a report of one novel mutation

Background Mutations in GJB2 gene are a major cause of autosomal recessive congenital hearing loss and the cause in some rare cases of the autosomal dominant form. The purpose of this study was to investigate the frequency and the features of GJB2 mutations in the Chinese patients with congenital sensorineural deafness.Methods Using PCR amplifying the entire coding region of GJB2 gene and direct DNA sequencing to analyze mutations in this gene among unrelated 69 cases with autosomal recessive congenital nonsyndromic deafness and 27 cases of dominant congenital deafness and 35 sporadic cases. We also detected mutations in GJB2 in 100 control subjects with normal hearing.Results 17. 4% (12/69) of the probands in the autosomal recessive, 7. 4% (2/27) of dominant families and 5.7% ( 2/35 ) of the sporadic congenital deafness patients had deafness-causing mutations in GJB2, respectively. Nine types of the mutations in GJB2 were detected in the recessive and sporadic group. They consisted of five types of polymorphism, and four types of deafness-causing mutation with homozygous 35delG in 1 sporadic (1/35), and 235delC frameshift mutation in 1 sporadic (homozygotes) and 10 recessive patients (2 heterozygotes and 8 homozygotes), and homozygous 442G→A missense mutation and homozygous 465T→A nonsense mutation in 1 different recessive proband, respectively. The 465T→A that related to recessive deafness was a novel mutation found by this study. The homozygous (10/69, 14. 5%) and the heterozygous (2/69,2.9%) GJB2 mutation in the recessive patients (12/69, 17.4%) and the homozygotes in the sporadic patient (2/35, 5. 7%) all had congenital severe to profound sensorineural hearing loss.511G→A missense mutation and 299 -300delAT frameshift mutation were found in two autosomal dominant congenital deafness families (2/27, 7.4%). The total mutation frequency of GJB2 was 12.2% (16/131) in the Chinese patients with congenital sensorineural deafness and 235delC was the most common deafness-causing mutation. Six types of mutation-5 types of polymorphism and 1 type of heterozygous deletion (235delC) mutation were found in the 100 control subjects. The carry rate of the most frequent type of mutation 235delC was 0. 5% in the controls(1/200 alleles). 109G→A was the most frequent (15/100, 15%) and 79G→A was the second common (8/100, 8%) polymorphism in this population.Conclusions The general mutation rate of GJB2 is 12.2% (16/131) and the 235delC is the most common type of deafness-causing mutation in Chinese patients with congenital hearing loss. 465T→A nonsense mutation that is associated to autosomal recessive deafness is a novel mutation found by this screening. 511G→A and 299-300delAT mutations contribute to autosomal dominant hearing loss. The study further supports the view that the common types of mutation in GJB2 according to different ethnic background and that the mutation prevalence in the East Asian deafness population is lower than that in the white population.     

非综合征型耳聋GJB2基因和mtDNA 12SrRNA A1555G位点的突变分析

目的:分析南京聋校散发性耳聋患者GJB2基因突变率和线粒体DNA(mtDNA)12SrRNA A1555G基因突变率.方法:收集聋校学生135名和健康对照人群162名外周血样本,PCR扩增GJB2和mtDNA 12SrRNA基因,通过限制性内切酶酶切鉴定突变热点,对PCR产物直接测序进行突变确定.结果:对GJB2检测结果显示:散发性耳聋患者样本中发现9种碱基改变(V27I、E114G、I203T V37I、176-191del16、235delC、299-300delAT、T123N和504insGCAA),其中235delC为主要突变方式,携带率为27.41%,其中纯合突变18例,杂合突变19例;162例正常对照中发现了15种碱基改变,其中4种为常见多态.散发聋135例和正常对照162例共计297例样本中未发现有mtDNA 12SrRNA A1555G位点突变存在;结论:GJB2基因突变是引起散发性非综合征耳聋患者听力损失发生的重要原因,不同人种GJB2基因的突变热点存在差异,235delC是GJB2基因在中国人中的主要致病突变位点;GJB2基因在人群中存在较多类型的突变和较多形式的多态性;在散发性耳聋中mtDNA 12SrRNA A1555G位点的突变率明显低于全国平均水平.     

KCNQ1和KCNH2基因与先天性长QT综合征的关系

目的　分析离子通道基因KCNQ1和KCNH2与先天性长QT综合征 (long QTsyndrome ,LQTS)的关系 ,以探讨LQTS发生的分子遗传机制。方法　在一个LQTS(JervellLange -Nielsen综合征型 )大家系中 ,采用PCR -直接测序技术 ,对KCNQ1和KCNH2基因的所有外显子和附近的部分内含子进行序列测定。结果　KCNQ1基因存在两种突变 ,其中一个位于外显子区域 ,但为同义突变 ,另外一个位于内含子区域 ;KCNH2基因也存在两种突变 ,均位于内含子区域。这四种单核苷酸有多态性 ,与现有报道不同。结论　在该LQTS家系中 ,KCNQ1和KCNH2基因存在四种突变 ,但均为非致病突变 ,提示KCNQ1和KCNH2基因以外的基因可能才是LQTS致病基因。KCNQ1基因和KCNH2基因存在新的单核苷酸多态性。     

dHMN-V型家系BSCL2基因和GARS基因突变分析

目的 报告1个远端型遗传性运动神经病V型(distal hereditary motor neuronopathy V, dHMN-V) 家系, 并探讨与BSCL2 (berardinelli-seip congenital lipody- strophy 2)基因和GARS基因 (glycyl tRNA synthetase)突变的关系.方法 对该家系进行临床及电生理检查,并应用PCR 直接测序法对先证者及其部分家系成员进行GARS基因全部17个外显子和BSCL2基因3号外显子突变检测.结果 该家系5代共13例患者,临床主要表现为成年起病,开始为单或双手大鱼际肌萎缩,逐渐出现小鱼际肌、手部骨间肌萎缩,遇冷挛缩,继而出现足趾骨间肌萎缩;肌电图提示运动神经神经传导速度降低,而感觉神经神经传导速度基本正常;突变分析结果显示该家系BSCL2基因3号外显子糖基化位点无突变,在GARS基因也未发现致病突变,仅在内含子区和外显子非编码区发现3个多态,分别为IVS18+136G→A, IVS17-6C→T和 C.-39G>C,其中IVS18+136G→A, IVS17-6C→T为新发现的2个多态.结论 dHMN-V具有临床和遗传异质性,其可能存在除BSCL2基因和GARS基因外的新的基因位点.     

遗传性先天性白内障与αA-晶体蛋白基因相关性研究

目的 分析遗传性先天性核性和绕核性白内障与定位于21q22．3的αA-晶体蛋白（CRYAA）基因之间的关系。同时对比单链构象多态性（SSCP）和变性高效液相色谱法（DHPLC）两种方法检测单核苷酸多态性（SNP）。方法 用PCR方法扩增CRYAA基因的3个外显子,分别用SSCP和DHPLC两种方法分析扩增产物,对异常者进行DNA测序,寻找基因变异情况。结果用SSCP分析15个样本,未见异常条带;同时用DHPLC检测15个样本,其中1个样本出现双峰,将该样本扩增产物测序鉴定,发现在5’端第6个核苷酸为G／A杂合,二者是同一氨基酸的2个密码子,该核苷酸为CRYAA基因的多态性位点。未发现该基因突变。结论 实验中未发现15例先天性白内障患者与CRYAA基因之间有关联。应用SSCP与DHPLC同时分析,DHPLC检测出1个多态性位点。DHPLC对杂合子检出的敏感性要高于SSCP。     

Mutation analysis and prenatal diagnosis of EXT1 gene mutations in Chinese patients with multiple osteochondromas

Background  Multiple osteochondromas (MO), an inherited autosomal dominant disorder, is characterized by the presence of multiple exostoses on the long bones. MO is caused by mutations in the EXT1 or EXT2 genes which encode glycosyltransferases implicated in heparin sulfate biosynthesis.

Methods  In this study, efforts were made to identify the underlying disease-causing mutations in patients from two MO families in China.

Results  Two novel EXT1 gene mutations were identified and no mutation was found in EXT2 gene. The mutation c.497T>A in exon 1 of the EXT1 gene was cosegregated with the disease phenotype in family 1 and formed a stop codon at amino acid site 166. The fetus of the proband was diagnosed negative. In family 2, the mutation c.1430-1431delCC in exon 6 of the EXT1 gene would cause frameshift and introduce a premature stop codon after the reading frame being open for 42 amino acids. The fetus of this family inherited this mutation from the father.

Conclusions  Mutation analysis of two MO families in this study demonstrates its further application in MO genetic counseling and prenatal diagnosis.

     

新生儿中常见的9个耳聋基因突变位点筛查分析

目的采用遗传性耳聋基因芯片对新生儿进行突变筛查,评估新生儿中9个常见耳聋基因突变的频率、突变类型以及其与耳聋的相关性。方法经产妇及家属的知情同意,并自愿要求行耳聋基因检测,收集本科室2010年8月至2011年9月出生的新生儿脐带血756例,提取DNA,用遗传性耳聋基因芯片检测中国人群中常见的4个耳聋相关基因的9个突变位点,包括GJB2(35 del G、176 del 16、235 del C、299 del AT)、GJB3(538 C>T)、SLC26A4(IVS7-2A>G、2168 A>G)、线粒体DNA 12S rRNA(1555 A>G、1494 C>T),对阳性结果进行测序验证。结果 756例新生儿检测出GJB2(235del C)突变15例,GJB2(176 del 16)突变1例,GJB2(299 del AT)突变4例,SLC26A4(IVS 7-2 A>G)突变13例,SLC26A4(2168 A>G)突变1例,12S rRNA(1555 A>G)均质突变型1例,测序结果与基因芯片结果一致。结论在没有耳聋家族史的新生儿中,GJB2基因的杂合突变率高于SLC26A4基因突变率,GJB3基因的突变较为少见。     

眼皮肤白化病近亲婚配一家系的MATP基因致病性新突变

目的 对1例近亲婚配所致的眼皮肤白化病(OCA)患者相关基因进行研究,确定致病基因并阐明突变类型.方法 应用聚合酶链反应、DNA序列测定、基于PCR的染色体步移技术(PCR-Walking)、横跨越断裂点的单管多重PCR(Gap-PCR)和生物信息学分析方法,对患者家系进行突变筛查和新突变鉴定.结果 患者膜相关转运蛋白(MATP)基因存在包含整个外显子3在内的6365 bp大片段缺失,缺失范围为c.562-1118(±2)_c.885+ 4923(±2).该突变为OCA4型致病性突变,患者基因型为该缺失突变纯合子.结论 首次发现并确定了一种OCA4型大片段缺失突变.     

腓骨肌萎缩症患者致病基因突变特点的研究

目的探讨腓骨肌萎缩症(Charcot-Marie-Tooth disease,CMT)致病基因的突变特点。方法应用实时荧光定量PCR方法、聚合酶链反应-单链构象多态性分析(PCR—SSCP)或PCR直接测序等方法对113个确诊的CMT家系进行了PMP22、MPZ、CX32、EGR2、GDAP1、NEFL、HSP22、HSP27等致病基因进行突变检测。结果发现有36个家系为PMP22重复突变所致,7个家系为CX32基因突变所致,1个家系为MPZ基因突变所致,1个家系为GDAP1基因突变所致,1个家系为HSP22基因突变所致,1个家系为HSP27基因突变所致,未发现PMP22、EGR2和NEFL基因点突变。结论CMT的PMP22基因重复突变所占比例为31．9％,CX32基因突变所占比例为6．2％,HSP22、HSP27、MPZ和GDAP1基因点突变所占比例均为0．9％,PMP22、EGR2和NEFL基因点突变少见。     

遗传性白内障与晶体蛋白基因

先天性白内障严重影响着视觉的发育。白内障的产生是大量基因通过不同机制相互作用导致突变的最终结果,大多数遗传性白内障与晶体蛋白基因的突变有关,这些晶体蛋白基因对维持晶状体的透明性和稳定性起着至关重要的作用。现对与遗传性白内障相关的晶体蛋白基因定位、晶体蛋白的组成与结构、翻译后修饰和突变蛋白的功能进行综述。