经测序证实的广东马查多-约瑟夫病的临床及基因突变特征研究

目的了解广东脊髓小脑型共济失调3型(Spinocerebellar ataxia type3,SCA3)/马查多-约瑟夫病(Machado-Joseph disease,MJD)的临床以及基因突变特征。方法应用聚合酶链式反应(PCR)和琼脂糖凝胶电泳以及测序技术,检测分析了广东省12个经临床诊断为SCA家系的21名患者、3名家系"正常人"以及8名散发SCA患者的SCA3/MJD基因三核苷酸重复突变,并分析基因确诊的SCA3/MJD患者的临床特征。结果检出10个SCA3/MJD家系15例患者,2例症状前患者,散发病例未检出SCA3/MJD患者。测序证实异常SCA3/MJD基因三核苷酸重复突变次数为70～81次,正常等位基因重复次数为14～36次,SCA3/MJD常见的临床表现除进行性加重的小脑性共济失调外,还常常合并锥体系以及锥体外系异常,发现一个SCA3/MJD家系患者表现为"纯"小脑性共济失调。结论 SCA3/MJD是广东最常见的SCA亚型,SCA3/MJD具有明显的临床异质性。     

脊髓小脑性共济失调3型、7型患者三家系的临床表现和基因突变

目的 探讨脊髓小脑性共济失调3型、7型的基因突变特点及临床表现.方法 总结3个家系中13例患者的临床表现,对13例患者、4例＂健康＂成员和4例普通成员,采用PCR法、琼脂糖凝胶电泳检测扩增产物、基因测序等技术分析SCA3、7型基因内CAG三核苷酸重复序列的长度和扩增数.结果 1个家系中4例患者存在SCA3/MJD（CAG）n扩增突变,CAG重复数为65～74次;2个家系中9例患者存在SCA7（CAG）n扩增突变,CAG重复数为40～52次.两亚型在神经系统受累部位等方面存在差异.结论 SCA3/MJD和SCA7型患者临床表现存在一定的差异,有利于鉴别及分型,但是基因检测是SCA患者确诊的唯一有效的诊断方法.     

一个早逝型脊髓小脑共济失调家系ATXN3基因动态突变的研究

目的:对早逝型脊髓小脑性共济失调(SCA)家系患者进行表型评价及分子遗传学诊断。方法:采用病例回顾和体检方法对家系进行调查,对存活并配合的家系成员进行基因检测。采用聚合酶链反应分别扩增SCA1、SCA2、SCA3/MJD、SCA6及SCA7致病基因的CAG重复序列,用8%变性聚丙烯酰胺凝胶电泳及荧光标记引物进行突变分析。结果:家系5代,目前共有14例发病,现患者仅存活4例,最早发病者信息不详,对其余13例进行表型评价。发病年龄33.5±7.71岁,病程11.6±4.03年,去世年龄46.0±7.16岁,遗传早现和遗传印记现象明显。对核心家系7例进行基因检测,5例为兄妹(包括3名患者),2例为其中2例患者的无症状未婚子女。3例患者SCA3/MJD致病基因ATXN3 CAG重复分别为72/29、74/29和73/29,2例患者子女分别为73/29和75/14,2例正常成员未携带异常重复突变,未发现SCA1、SCA2、SCA3/MJD、SCA6及SCA7基因中CAG突变性扩增。结论:ATXN3基因中CAG三核苷酸重复拷贝数的异常扩增是早逝型SCA3/MJD家系致病原因,CAG重复在传递过程中极不稳定是否导致该家系患者早逝,还有待进一步证实。2例未发病成员携带异常突变基因,预测将来可能发病。     

脊髓小脑共济失调2型家系的临床表现和基因型分析

目的探讨脊髓小脑共济失调2型(spinocerebellar ataxia 2,SCA2)患者的临床表现和分子遗传学特征。方法描述一家系4代SCA2部分成员的临床表现,总结其特点,并检测基因分型。结果该家系4代共15例患者发病,均符合常染色体显性遗传特征,14例(除先证者的外婆发病情况不详外)均以步态不稳为首发症状,伴不同程度构音障碍,均有明显的腱反射减弱、四肢远端肌肉萎缩,部分患者伴慢眼动、动作性震颤、不自主摇头、癫痫等。其中第1代患者发病年龄不详,第2代患者于50岁左右发病,第3代患者于36~47岁发病,第4代患者于21岁发病,发病年龄呈逐代提前现象。先证者及其同胞兄弟患者SCA2/ATXN2基因(CAG)n重复数目为39次,其侄子(CAG)n重复数目为50次,发病明显提前且症状重。结论 SCA2家系中存在遗传早现现象,除小脑性共济失调外,还可伴有其他特征性表现。这些临床特征有助于诊断与鉴别诊断,但明确诊断依靠基因学检测。     

脊髓小脑性共济失调1例分析并文献复习

目的:讨论1例脊髓小脑性共济失调患者的临床表现及家族遗传情况.方法:对1例脊髓小脑性共济失调患者的病史资料进行分析,总结临床表现及遗传情况.结果:脊髓小脑性共济失调以共济失调为主要临床表现,经过基因测序发现,主要为CAG的重复顺序扩增所致.结论:脊髓小脑性共济失调是一种常染色体显性遗传疾病,共济失调为其主要临床表现.     

2个范德伍德综合征家系的IRF6基因突变检测

目的对2个中国范德伍德综合征(Van der Woude syndrome,VWS)家系进行临床和遗传特点分析,并进行IRF6基因的突变检测,明确中国人VWS致病基因IRF6的突变情况,并发现可疑的突变热点区域。方法通过先证者及现场家系调查、临床检查和系谱分析收集2个VWS家系成员24人的外周血样本,提取DNA用于IRF6基因的聚合酶链扩增反应(polymerase chain reaction,PCR)。采用Sanger测序法对所有VWS家系成员的IRF6基因的编码区7个外显子进行测序,使用mutation surveyor软件对测序结果与参考序列进行比对分析。结果 2个家系24人中受累患者6名,5名(83.3%)患者有唇腭裂,5名(83.3%)患者有唇瘘,6名患者均无牙齿发育不全表现,唇瘘伴唇腭裂表型常见,无其他组织器官畸形。24名成员均进行了IRF6基因第3至第9外显子的测序,6名患者均存在基因突变,家系1的3名患者均携带位于第9外显子的c.1234CT杂合突变;家系2的3名患者均携带位于第9外显子的c.1210GA杂合突变;未发现其他非患者的家系成员携带IRF6基因突变。结论 VWS综合征存在遗传异质性和临床表型复杂性,患者的表型与致病突变有关。通过基因检测可以对VWS患者进行遗传分析和产前诊断,弥补产前超声容易漏诊的不足。     

MYO7A、CDH23、SLC26A4基因新突变位点导致先天性耳聋分子诊断与产前诊断

目的通过3个先天性耳聋家系的致病基因突变分析,查找耳聋未知致病突变,帮助高风险家庭进行产前诊断。方法对5名经过常见突变位点聋病易感基因筛查阴性,但临床诊断为耳聋的患者及核心家系成员,进行听力、视力相关检查,使用基因组全外显子测序方法及基因测序方法进行检测;采集高风险家庭孕18周母亲胎儿羊水20ml1份,行产前基因分析。结果一个家系致病基因为MYO7A基因的c.397dupC和c.4937C>A两个位点复合杂合突变致病;一个家系致病基因为CDH23基因的c.7240-1G>A和c.7252G>A两个位点复合杂合突变致病;一个家系致病基因为SLC26A4基因的c.259G>T和IVS7-2A>G(c.919-2A>G)两个位点复合杂合突变致病,孕18周胎儿基因检测与先证者携带相同的致病基因。其中检出MYO7A基因的c.397dupC位点突变和CDH23基因的c.7252G>A位点突变为国内首报新突变位点。结论通过基因测序、家系临床资料分析,基因突变携带者高风险家庭产前诊断,减少出生缺陷,丰富广西耳聋突变谱。     

一个Waardenburg综合征家系的致病基因突变分析

目的分析一个Waardenburg综合征(WS)家系成员的临床表型和基因突变。方法收集一个WS综合征患者家系的临床资料,采用Sanger测序法对家系成员进行WS综合征相关基因的外显子测序分析。结果家系中共有2例患者,先证者及其弟弟具有WSⅡ的先天性感音神经性耳聋和虹膜色素异常的临床特征,均携带SOX10基因新发c.52GT(p.E18X)杂合致病突变;先证者父亲、母亲和姐姐SOX10基因序列测序分析均未见异常。结论在一个Waardenburg综合征家系中发现未见报道的SOX10基因新发突变,对于该病遗传咨询和产前诊断具有重要意义。     

靶向捕获-高通量测序法对一个先天性白内障家系致病基因的研究

目的:应用靶向高通量测序技术鉴定一个常染色体显性遗传先天性白内障家系的致病基因。方法:采用靶向捕获已知白内障致病基因并行高通量测序,筛选出候选基因,并对其进行家系内外的共分离检验。结果:该家系符合常染色体显性遗传规律,所有患者均为核性白内障。靶向基因测序发现,位于主要内源性蛋白MIP基因的一个杂合突变c.97CT(p.R33C)可能是该家系的致病突变,该变异造成MIP基因编码的水通道蛋白氨基酸序列错义改变,并引起蛋白质结构异常,从而影响其功能。通过一代测序验证并确定该杂合突变为该家系的致病突变。结论:MIP基因c.97CT(p.R33C)突变是造成该先天性白内障家系致病的分子机制。     

14个遗传性非综合征型耳聋家系基因分析

目的明确14个遗传性非综合征型耳聋(NSHL)家系的致病基因并开展产前诊断。方法选取2011年5月-2016年8月来江西省妇幼保健院产前诊断中心进行遗传咨询的14个NSHL家系,对14个家系的46名成员进行基因芯片检测,检测位点为GJB2、GJB3、SLC26A4及线粒体DNA 12S rRNA 4个基因上的9个突变热点。颞部CT显示前庭水管扩大但基因芯片检测为阴性或携带SLC26A4突变的患者行SLC26A4基因测序,对需产前诊断的12个家系的孕妇行产前诊断,预测胎儿听力状态。结果 14个家系46名成员和12份胎儿羊水样本中,检出携带GJB2基因突变33例,SLC26A4已知突变19例,新发突变2例,分别为SLC26A4 1242 GA与SLC26A4 2089AG,线粒体DNA 12S rRNA突变3例,均为12S rRNA 1555AG均质突变,未发现GJB3突变。结论基因芯片技术结合基因测序技术能明确大部分NSHL家系病因并提供生育指导,GJB2与SLC26A4突变为我国NSHL最常见的致病基因。     

The pathogenesis of Machado Joseph Disease: a high manganese/low magnesium initiated CAG expansion mutation in susceptible genotypes?

The origin of the progressive spinocerebellar ataxic disorder 'Machado Joseph Disease (MJD)' has been attributed solely to an expansion mutation resulting from an autosomal dominant inheritance of an unstable CAG repeat in chromosome 14q32.1 of the MJD gene that encodes for the synthesis of ataxin 3. The faulty gene has purportedly been disseminated since the Middle Ages into Azorean, Dutch and Makassan communities by an international trading community based in NE-central Portugal. However, following improvements in MJD surveillance, the MJD afflicted families that have been identified in increasing numbers of familial clusters of MJD being discovered around the world--e.g. in Aboriginal, Yemenite, Asian and Japanese populations--cannot be connected back to the original Portuguese founder families, but rather implicates an environmental factor, superimposed on a genetic flaw. An analytical study of the isolated ecosystems supporting both the Portuguese and non-Portuguese MJD affected communities demonstrates a common abnormal hallmark of high manganese (Mn)/low magnesium (Mg) status, suggesting that this aberrant mineral ratio inactivates the Mn/Mg catalyzed endonuclease 1 enzyme in the biosystems of those who are dependent upon these ecosystems. Endonuclease activity is crucial for protecting against the expansion/contraction of the trinucleotide repeats in the genes that encode for proteins such as Ataxin 3--the 'mutant' chaperone protein that hallmarks the central nervous system (CNS) of MJD sufferers. It is proposed that MJD, and possibly the other more common expansion mutation diseases such as Friedrich's Ataxia and Huntingdon's Chorea, are multifactorial diseases caused by a hitherto unrecognised autosomal dominant inherited failure to regulate Mn/Mg metabolism in populations living in high Mn/low Mg ecosystems. Mg supplementation of the 'at risk' populations during the 'in utero' developmental stages could be all that is required to maintain healthy endonuclease turnover, thereby protecting MJD susceptible genotypes against this fatal, progressive neurodegenerative disease.     

Molecular physiopathology of the spinocerebellar ataxia type 6 (SCA6)

Spinocerebellar ataxia type 6 (SCA6) is a neurodegenerative, monogenic, and autosomic dominant disease which is characterized by a global cerebellar atrophy. Typically the onset is at mature age and undergoes a moderate evolution. This illness has been associated with a mutation in the gene CACNA1A, that encodes for subunit alpha1A of P/Q type voltage/dependent calcium channel. The mutation results in the expansion of a CAG triplet repeat located in the last exon of the gene, which is translated into a polyglutamine chain in the carboxyl tail of the calcium channel subunit. Several studies have been made to clarify the mechanism for the toxicity of polyglutamines in cerebellar neurons; SCA6 could be considered a polyglutamine proteinopathy linked to caspases mediated death pathway. However, SCA6 is also considered a channelopathy, like paroxysmal diseases as hemiplegic familiar migraine and episodic ataxia type 2. The goal of this review is to analyze the intracellular mechanism triggering neuronal death in cerebellum, and the subsequent neurodegeneration.     

The Pathogenesis of Machado Joseph Disease: A High Manganese/Low Magnesium Initiated CAG Expansion Mutation in Susceptible Genotypes?

The origin of the progressive spinocerebellar ataxic disorder ‘Machado Joseph Disease (MJD)’ has been attributed solely to an expansion mutation resulting from an autosomal dominant inheritance of an unstable CAG repeat in chromosome 14q32.1 of the MJD gene that encodes for the synthesis of ataxin 3. The faulty gene has purportedly been disseminated since the Middle Ages into Azorean, Dutch and Makassan communities by an international trading community based in NE-central Portugal. However, following improvements in MJD surveillance, the MJD afflicted families that have been identified in increasing numbers of familial clusters of MJD being discovered around the world—e.g. in Aboriginal, Yemenite, Asian and Japanese populations—cannot be connected back to the original Portuguese founder families, but rather implicates an environmental factor, superimposed on a genetic flaw. An analytical study of the isolated ecosystems supporting both the Portuguese and non-Portuguese MJD affected communities demonstrates a common abnormal hallmark of high manganese (Mn)/low magnesium (Mg) status, suggesting that this aberrant mineral ratio inactivates the Mn/Mg catalyzed endonuclease 1 enzyme in the biosystems of those who are dependent upon these ecosystems. Endonuclease activity is crucial for protecting against the expansion/contraction of the trinucleotide repeats in the genes that encode for proteins such as Ataxin 3—the ‘mutant’ chaperone protein that hallmarks the central nervous system (CNS) of MJD sufferers. It is proposed that MJD, and possibly the other more common expansion mutation diseases such as Friedrich’s Ataxia and Huntingdon’s Chorea, are multifactorial diseases caused by a hitherto unrecognised autosomal dominant inherited failure to regulate Mn/Mg metabolism in populations living in high Mn/low Mg ecosystems. Mg supplementation of the ‘at risk’ populations during the ‘in utero’ developmental stages could be all that is required to maintain healthy endonuclease turnover, thereby protecting MJD susceptible genotypes against this fatal, progressive neurodegenerative disease.     

A case of Friedreich's ataxia confirmed by DNA-analysis

The first case of DNA-confirmed Friedreich's ataxia in Bulgaria is presented. The results from the DNA studies of the index patient revealed two alleles with an expansion between 500 and 1500 repeats of the GAA trinucleotide in the first intron of the X25 gene. The parents had one normal allele with 7-22 repeats and one allele with a similar expansion to that of the patient in the first intron of the X25 gene. These results confirm the homozygous mode of transmission of the abnormal alleles (with an expansion of the GAA trinucleotide in the first intron of the X25 gene) from the two normal heterozygous parents to their affected offspring.     

From gene to disease; HD gene and Huntington disease]

Huntington's disease (HD) is a late onset, incurable, autosomal dominantly-inherited, progressive neuropsychiatric disease, characterised by chorea, changes in personality, mood and behaviour, and dementia. Huntington's disease is a clinical diagnosis. The advent of DNA diagnosis has made predictive, prenatal and preimplantation testing possible for at-risk persons or asymptomatic carriers. The prevalence is estimated to be 3-10/100,000 among individuals of European descent; HD is less common in other ethnic groups. Huntington's disease is caused by an expanded trinucleotide CAG repeat in the HD gene on chromosome 4. The gene encodes for the protein huntingtin, with an as yet unknown function. The mutated huntingtin has an elongated stretch of glutamines which leads to a gain of function such as overactivity, excitotoxicity, or to interactions with other proteins.     

Progressive ataxia and cognitive deficits caused by premutation in the fragile-X-mental retardation gene

A 75-year-old man had progressive difficulty with walking, intention tremor, ataxia, and mild cognitive deficits. MRI scan ofthe brain showed symmetrical hyperintensities in the middle cerebellar peduncles. DNA analysis ofthe fragile-X gene revealed an expansion of 150-200 repetitions in the FMR1-gene, compatible with a premutation in the fragile-X gene. Two years later, after progression of the symptoms, the patient was admitted to a nursing home. The clinical picture of intention tremor, parkinsonism and ataxia with white matter lesions and atrophy on MRI occurs in carriers of this premutation and has recently been described as the fragile-X-associated tremor/ataxia syndrome. Recognition of this clinical picture is important for the patient but also for the relatives, since female carriers of the premutation have an increased risk of offspring with the fragile-X syndrome.