浙江沿海一家系脊髓小脑性共济失调的基因突变检测与临床表现

目的 探讨浙江沿海脊髓小脑性共济失调的基因突变检测与临床表现.方法 对该家系18例患者的临床表现、头颅MRI等辅助检查资料分析,并与10名家系中未发病成员及12名非血缘的健康人进行SCA31MJD基因CAG三核苷酸重复数目比较.结果 家系18例患者均为SCA3/MJD型,同时检测出家系中未发病对照组有2例为SCA31MJD型基因携带者.产物测序结果家系对照组与健康对照组CAG重复数为14～27次;SCA患者CAG重复数为67～82次;SCA3/MJD携带者CAG重复数为28～45次.在现存三代18例患者中,每代均有患者,男女均受累,起病年龄平均38岁,以行走不稳、动作笨拙和言语含糊为突出表现,MRI检测结果小脑、脑干明显萎缩.结论 在我国沿海存在SCA3/MJD家系遗传.临床均以共济失调和构音障碍为突出,CAG重复数目检测可为基因诊断和症状前诊断提供依据.     

一个遗传性脊髓小脑型共济失调大家系的致病基因分析

目的探讨一个遗传性脊髓小脑型共济失调（SCA）大家系的遗传特点和基因突变分析。方法对一个遗传性脊髓小脑型共济失调（SCA）大家系进行家系调查,绘制系谱图,抽取家系成员外周血,采用聚合酶链反应和毛细管电泳对致病基因进行分析检测。结果该家系的遗传性脊髓小脑型共济失调（SCA）为常染色体显性遗传,6代45人中有15人为SCA患者,4人为携带致病基因的无症状患者。患者ATX3基因的CAG三核苷酸重复65-73次。结论该家系为常染色体显性遗传的SCA3型（SCA/MJD）,患者基因突变检测分析显示异常扩增的CAG突变数与发病年龄呈明显的负相关。基因突变检测在疾病诊断和早期发现无症状患者方面有重要作用,从遗传生殖角度阻断该病的遗传有重要意义。     

齿状核红核苍白球路易氏体萎缩症家系的临床和基因突变分析

目的 探讨齿状核红核苍白球路易氏体萎缩症(dentatorubral-pallidoluysian atrophy,DRPLA)患者的临床特征和基因突变特点.方法 应用基于荧光标记的毛细管电泳片段分析法对708个常染色体显性遗传脊髓小脑共济失调(spinocerebellar ataxias,SCA)家系的先证者和119例临床拟诊为SCA的散发患者进行DRPLA基因CAG重复次数分析.结果 共检出3例患者存在DRPLA基因CAG重复扩展突变.片段分析显示其CAG重复次数分别为16/58、16/58和14/54次,长片段重复次数达到异常范围.3个家系的先证者均为成年起病,以共济失调为主要症状,患者可伴发抽搐、颈部扭转等表现.结论 在827例共济失调病例中仅发现3例DRPLA,说明该病在中国人群中较为罕见.DRPLA的临床表现复杂多样,存在变异.对DRPLA患者的临床特征和突变特点的细致分析有助于同其他SCA类型进行鉴别诊断.     

脊髓小脑性共济失调12型维吾尔族一家系的基因突变及临床特点

目的 研究新疆地区维吾尔族脊髓小脑性共济失调12亚型(spinocerebellar ataxia type 12,SCA12)致病基因的CAG三核苷酸病理重复次数范围及临床特点.方法 依据Harding标准,收集一个维吾尔族家系,应用聚合酶链反应、琼脂糖凝胶电泳、T载体分子克隆技术并结合酶切鉴定、直接测序等技术对其中6例患者、54例家系"健康"个体进行分子遗传学诊断,基因诊断为SCA12型,同时对致病基因CAG三核苷酸病理重复次数进行突变分析.结果 发现该家系SCA12型患者6例,症状前患者13例.5例经基因重组检测发现:患者异常等位基因CAG重复数目分别是47次、51次、52次、53次;症状前患者是48次;其中在连续CAG重复中间有单个碱基C、A、G的互相替换.结论 SCA12型的47次CAG病理重复次数为国内外报道的最小CAG病理重复次数;国内首次对维吾尔族SCA12型的基因突变特点进行分析,从而对于该类疾病的准确分类、病因探讨、治疗、产前诊断等具有重要的意义.     

脊髓小脑性共济失调12型维吾尔族一家系的基因突变及临床特点

目的 研究新疆地区维吾尔族脊髓小脑性共济失调12亚型(spinocerebellar ataxia type 12,SCA12)致病基因的CAG三核苷酸病理重复次数范围及临床特点.方法 依据Harding标准,收集一个维吾尔族家系,应用聚合酶链反应、琼脂糖凝胶电泳、T载体分子克隆技术并结合酶切鉴定、直接测序等技术对其中6例患者、54例家系"健康"个体进行分子遗传学诊断,基因诊断为SCA12型,同时对致病基因CAG三核苷酸病理重复次数进行突变分析.结果 发现该家系SCA12型患者6例,症状前患者13例.5例经基因重组检测发现:患者异常等位基因CAG重复数目分别是47次、51次、52次、53次;症状前患者是48次;其中在连续CAG重复中间有单个碱基C、A、G的互相替换.结论 SCA12型的47次CAG病理重复次数为国内外报道的最小CAG病理重复次数;国内首次对维吾尔族SCA12型的基因突变特点进行分析,从而对于该类疾病的准确分类、病因探讨、治疗、产前诊断等具有重要的意义.     

常染色体显性小脑性共济失调致病基因动态突变位点三核苷酸重复变异的研究

目的 探讨毛细管电泳技术在动态突变位点检测中的技术问题,并分析常染色体显性小脑性共济失调(autosomal dominant cerebellar ataxias,ADCA)患者与正常对照人群脊髓小脑性共济失调(spinocerebellar ataxia,SCA)1,2,3,6,7亚型的致病基因动态突变位点三核苷酸重复数的分布范围,以期为今后标准化ADCA基因检测技术及中国人群制定相关基因动态突变量化标准提供依据.方法 以263个ADCA家系的先证者及261个无亲缘关系的正常对照为对象,应用荧光PCR-毛细管电泳及DNA测序技术进行上述SCA致病基因内动态突变位点基因分型,统计分析不同对照下各基因动态突变位点毛细管电泳检测重复数与DNA测序结果的差异,以及各基因三核苷酸重复特点及重复次数分布范围.结果 以DNA测序所确定的重复次数为标准,SCA各致病基因动态突变位点的PCR产物在毛细管电泳中,迁移率均大于GC含量相对均衡的分子量内标片段,其中SCA2、6、7亚型基因位点尤为明显.以各基因已知CAG重复数片段为外标计算受检标本CAG重复数,可将误差缩小至±1个拷贝.在各基因CAG正常重复范围内,PCR产物毛细管电泳迁移率主要与CAG拷贝数相关,而与CAG拷贝数变异所致PCR产物GC含量变化的关系不明显.在263个ADCA家系中,发现SCA1家系6个(2.28%),SCA2家系8个(3.04%),SCA3家系81个(30.80%),未发现SCA6和SCA7家系.排除上述突变基因后,正常等位基因重复次数变异范围在SCA1为17～36次,杂合率为76.1%,SCA2为13～30次,杂合率为17.7%,SCA3为14～39次,杂合率为74.4%,SCA6为6～16次,杂合率为72.1%,SCA7为6～13次,杂合率为41.3%.突变等位基因重复次数变化范围在SCA1为49～56次,SCA2为36～41次,SCA3为59～81次.未发现单一位点纯合突变或两位点双重杂合突变患者.结论 通过设置有限数量的已知拷贝数对照,进行荧光PCR-毛细管电泳检测,可以准确地计算出SCA致病基因动态突变位点CAG重复次数.本研究结果支持中国人群中SCA3致病基因突变是导致ADCA的最常见病因.SCA1,2,3,6,7亚型致病基因正常与突变的CAG重复数资料可为中国人ADCA动态突变量化标准的建立提供参考.     

遗传型橄榄桥脑小脑萎缩一家系报告

本室发现一个遗传型橄榄桥脑小脑萎缩（olivopontocerebellar atrophy,OPCA）家系,并呈AD遗传。现报告如下。     

脊髓小脑性共济失调一家系的基因诊断和产前诊断

目的 确定一脊髓小脑性共济失调(spinocerehellar ataxia,SCA)家系具体分型,并开展症状前患者检测和产前诊断.方法 收集该脊髓小脑性共济失调家系中的2例患者的血液标本,结合该家系的临床表现和我国该类疾病的发病率,采用聚合酶链反应对SCA1、SCA2和SCA3/MJD 3个基因的三核苷酸重复片段进行扩增,并通过琼脂糖凝胶电泳和PCR产物测序的方法确定所有正常和异常扩增等位基因内三核苷酸重复次数.明确致病基因后,对患者子女进行症状前检测,并对1例怀孕症状前患者进行了产前诊断.结果 SCA1和SCA2基因内三核苷酸重复次数在正常范围内,SCA3/MJD的2个等位基因中1个等位基因三核苷酸重复次数在正常范围内,另1个等位基因三核苷酸重复次数在异常范围内.患者子女有1人携带异常等位基因,胎儿携带异常等位基因.结论 该家系经基因诊断确诊为SCA3/MJD型,有1人为症状前患者,该症状前患者所孕胎儿也为症状前患者.     

11个脊髓小脑共济失调家系的临床表现和基因型分析

目的 探讨11个脊髓小脑共济失调(spinocerebellar ataxias,SCA)家系的临床特征,并进行基因分型.方法 应用聚合酶链式反应联合毛细管电泳片段分析,对11个家系中SCA患者进行SCA1、SCA2、SCA3、SCA6、SCA7、SCA17亚型致病基因内CAG三核苷酸重复次数检测,从而对临床确诊患者进...     

中国汉族人群脊髓小脑性共济失调1、2、3、6、7、8、10、12、17亚型和齿状核红核苍白球路易体萎缩亚型多核苷酸正常重复次数范围研究

目的 研究中国汉族健康人群中脊髓小脑性共济失调(spinocerebellar ataxias,SCA)1、2、3、6、7、8、10、12、17亚型和齿状核红核苍白球路易体萎缩(dentatorubral-pallidoluysian atrophy,DRPLA)亚型致病基因多核苷酸正常重复次数的范围,以助于SCA各亚型基因诊断平台的建立和诊断标准的确认.方法 应用荧光聚合酶链反应、毛细管凝胶电泳等技术对300名健康个体进行SCA 1、2、3、6、7、8、10、12、17亚型和DRPLA亚型致病基因多核苷酸正常重复次数的检测分析.结果 在300名健康个体中CAG三核苷酸在SCA1亚型中为17～35次,在SCA2亚型中为14～28次,在脊髓小脑性共济失调3型/Machado-Joseph病,SCA3/Machado-Joseph disease,SCA3/MJD亚型中为13～41次,在SCA6亚型中为4～16次,在SCA7亚型中为5～17次,在SCA12亚型中为5～21次,在SCA17亚型中为23～41次,在DRPLA亚型中为12～33次;在SCA8亚型中CTA/CTG三核苷酸的重复次数为12～43次;在SCA10亚型中ATTCT五核苷酸的重复次数为9～32次.其中SCA8的12次CTA/CTG三核苷酸重复,SCA10的9次ATTCT五核苷酸重复,SCA17的23次CAG三核苷酸重复,为目前国内外报道的3种亚型多核苷酸正常重复次数的最小次数.SCA3/MJD亚型的41次CAG三核苷酸重复,SCA10亚型的32次ATTCT五核苷酸重复为目前报道的2种亚型多核苷酸正常重复次数的最大次数.结论 SCA各亚型多核苷酸正常次数范围存在种族差异,与遗传和种族背景相关;首次建立了中国汉族人群10种不同SCA亚型正常核苷酸重复次数范围,可为SCA的诊断提供参考标准.     

遗传性脊髓小脑型共济失调的CAG三核苷酸突变检测

目的 评价ＳＣＡ１、ＳＣＡ２、ＳＣＡ３／ＭｊＤ、ＳＣＡ６、ＳＣＡ７和ＤＲＰＬＡ的ＣＡＧ三核苷酸异常扩增突变「（ＣＡＧ）ｎ」,在中国人遗传性脊髓小脑型共济失调（ｓｐｉｎｏｃｅｒｅｂｅｌｌａｒ ａｔａｘｉａ,ＳＣＡ）患者的分布频率。方法 经聚合酶链反应、变性聚丙烯酰按凝胶电泳和银染显带技术,检测分析了８５个中国人常染色体显性遗传ＳＣＡ家系（其中患者１６７例）和３７例散发ＳＣＡ患者的ＳＣＡ１、ＳＣＡ２、     

Difference in disease-free survival curve and regional distribution according to subtype of spinocerebellar ataxia: a study of 1,286 Japanese patients

Expansions of trinucleotide repeats have been discovered in spinocerebellar ataxia (SCA) types 1, 2, 6, 7, 12, and 17, Machado-Joseph disease (MJD/SCA3), and dentatorubropallidoluysian atrophy (DRPLA). However, the frequency of familial SCA in Japan remains unclear. The number of trinucleotide repeats was determined for 1,286 patients. Three hundred and thirty families (523 cases) were autosomal dominant group (A), and 165 families were positive for family history but not autosomal dominant group (B), while the remaining 598 cases were the sporadic group (C). The frequency of SCA subtypes in autosomal dominant group was: 1) 5.5% for SCA1; 2) 2.4% for SCA2; 3) 27.6% for MJD/SCA3; 4) 25.5% for SCA6; 5) 0.3% for SCA17; and 6) 7.3% for DRPLA. Abnormal expansion of SCA12 was not detected. Another 31.5% of the patients in the autosomal dominant group had unknown genetic abnormalities. Within group B, SCA6 was the most prominent and within the sporadic group MJD/SCA3 and SCA6 were the most common subtypes observed. The disease-free survival curve of SCA6 was different from that of other SCAs and the mean age at onset for SCA6 was found to be later than that of the other types. Regional differences were observed in the relative rate of SCA subtypes. MJD/SCA3 appears more common in the Kanto and Kyushu districts of Japan, whereas SCA6 is most common in the Chugoku district. In order to establish an effective social welfare system for SCA patients, clinical course and regional differences in the prevalence of SCA subtypes must be taken into consideration.     

Difference in disease‐free survival curve and regional distribution according to subtype of spinocerebellar ataxia: A study of 1,286 Japanese patients

Expansions of trinucleotide repeats have been discovered in spinocerebellar ataxia (SCA) types 1, 2, 6, 7, 12, and 17, Machado‐Joseph disease (MJD/SCA3), and dentatorubropallidoluysian atrophy (DRPLA). However, the frequency of familial SCA in Japan remains unclear. The number of trinucleotide repeats was determined for 1,286 patients. Three hundred and thirty families (523 cases) were autosomal dominant group (A), and 165 families were positive for family history but not autosomal dominant group (B), while the remaining 598 cases were the sporadic group (C). The frequency of SCA subtypes in autosomal dominant group was: 1) 5.5% for SCA1; 2) 2.4% for SCA2; 3) 27.6% for MJD/SCA3; 4) 25.5% for SCA6; 5) 0.3% for SCA17; and 6) 7.3% for DRPLA. Abnormal expansion of SCA12 was not detected. Another 31.5% of the patients in the autosomal dominant group had unknown genetic abnormalities. Within group B, SCA6 was the most prominent and within the sporadic group MJD/SCA3 and SCA6 were the most common subtypes observed. The disease‐free survival curve of SCA6 was different from that of other SCAs and the mean age at onset for SCA6 was found to be later than that of the other types. Regional differences were observed in the relative rate of SCA subtypes. MJD/SCA3 appears more common in the Kanto and Kyushu districts of Japan, whereas SCA6 is most common in the Chugoku district. In order to establish an effective social welfare system for SCA patients, clinical course and regional differences in the prevalence of SCA subtypes must be taken into consideration. © 2002 Wiley‐Liss, Inc.     

Frequency analysis of autosomal dominant cerebellar ataxias in Japanese patients and clinical characterization of spinocerebellar ataxia type 6

Using a molecular diagnostic approach, we investigated 101 kindreds with autosomal dominant cerebellar ataxias (ADCAs) from the central Honshu island of Japan, including spinocerebellar ataxia type 1 (SCA1), spinocerebellar ataxia type 2 (SCA2), Machado–Joseph disease (MJD), dentatorubral and pallidoluysian atrophy (DRPLA) and spinocerebellar ataxia type 6 (SCA6). In our unselected series, MJD was the most common type of ADCA, accounting for 33.7% followed by DRPLA (19.8%), SCA2 (5.9%) and SCA6 (5.9%). No SCA1 mutations were identified. We analysed the clinical features of six molecular confirmed SCA6 kindreds: in each family, there was an expanded allele in the α1A-voltage dependent calcium channel comprising between 23 and 25 CAG repeats. The mean age at onset of symptoms was 43±13 years. The clinical features consisted predominantly of cerebellar ataxia, dysarthria and horizontal nystagmus, which was generally consistent with ADCA type 3. However several new clinical features were found in some patients: dramatic anticipation, rapid disease progression, severe ataxia associated with action tremor or action myoclonus, and very early onset, which are not described as the classical features of ADCA type 3.     

Uncloned expanded CAG/CTG repeat sequences in autosomal dominant cerebellar ataxia (ADCA) detected by the repeat expansion detection (RED) method.

In some neurodegenerative diseases, genetic anticipation correlates with expansions of the CAG/CTG repeat sequence above the normal range through the generations of a pedigree. Among these neurodegenerative diseases are late onset autosomal dominant cerebellar ataxias (ADCA). ADCA are genetically heterogeneous disorders with different cloned genes for spinocerebellar ataxia type 1 (SCA1), type 2 (SCA2), type 3 or Machado-Joseph disease (SCA3/MJD), and type 6 (SCA6). Another related dominant ataxia, dentatorubral-pallidoluysian atrophy (DRPLA), also shows CAG/CTG repeat expansions. Genetic anticipation has been reported for all of them except for the recently cloned SCA6 gene. Other, as yet undetected SCA genes may show the same features. We have used the repeat expansion detection (RED) method to detect repeat expansions directly in DNA samples from ADCA patients not resulting from known genes. Our sample consists of 19 affected index cases, corresponding to 52.8% of our ADCA families without CAG/CTG repeat expansions in the SCA1, SCA2, SCA3/MJD, SCA6, or DRPLA genes. Eighty-nine percent of the index cases had expansions of a CAG/CTG sequence greater than 40 repeats by RED, while these were observed in only 26.9% of 78 healthy subjects from the general population (p < 0.0001). The distribution of RED fragments in controls and ADCA patients also shows significant differences with the Mann-Whitney U test (U = 376.5, p = 0.0007). Moreover, there was a significant inverse correlation between the size of expansion and the age of onset (r = -0.54, p = 0.018). These results show CAG/CTG repeat expansions of over 40 repeats in our sample of ADCA families not resulting from known SCA genes.     

Molecular genetic analysis of a new form of spinocerebellar ataxia in a Chinese Han family

The pathological changes of spinocerebellar ataxias (SCAs), mainly include the degeneration of the cerebellum, spinal cord and brainstem. To investigate the genotype of a three-generation Chinese Han pedigree with an autosomal dominant SCA for clinical diagnosis and genetic counseling, direct mutation test and linkage analysis were performed. SCA1–8, SCA10–14, SCA17, SCA27 and dentatorubral-pallidoluysian atrophy (DRPLA) were excluded by mutation analysis while SCA15/16/29, SCA18, SCA19/22, SCA20, SCA21, SCA23, SCA25, SCA26, SCA28 and SCA30 were excluded by linkage analysis. Therefore, we excluded all of the previously identified SCA-associated genes and loci. Interestingly, one patient (III-13) had a novel mutation of the pleckstrin homology domain containing, family G (with RhoGef domain) member 4 gene (PLEKHG4), and another patient (II-7) had a novel mutation of the β-III spectrin gene (SPTBN2) (Genbank accession numbers FJ905766 and FJ811850, respectively). However, mutations of the PLEKHG4 gene and the SPTBN2 gene are not the causes of SCAs in this family. We conclude that this autosomal dominant cerebellar ataxia family is likely a new genotype of SCAs.     

Genomic instability and neurodegenerative disease

The discovery of unstable DNA sequences as the cause of genetic disease is a fascinating new area in human genetics, raising a number of important questions addressing the understanding of both the mechanisms and the effects of this new type of mutation. Trinucleotide repeat expansion mutations have been identified in a number of neurodegenerative diseases, including spinal and bulbar muscular atrophy (SBMA), fragile X syndrome (FRAXA and FRAXE), myotonic dystrophy (DM), Huntington's disease (HD), spinocerebellar ataxia types 1, 2, 3, 6, 7 (SCA1, SCA2, SCA3, SCA6, SCA7), dentatorubral-pallidoluysian atrophy (DRPLA), Friedreich's ataxia (FRDA) and autosomal dominant pure spastic paraplegia (ADPSP). They have been traced to genetic variation in the length of (CTG)n/(CAG)n, (CGG)n/(CCG)n, or (GAA)n/(TTC)n triplet repeats in DNA. In normal individuals these loci contain a short length of triplet repeats (usually 5-40), which is polymorphic within the population. Increases in the lengths of the translated triplet repeats to 40-100 are associated with disease symptoms, whereas the untranslated triplet repeats to 200-3000 are associated with the disease. We concentrated on repeat expansions in myotonic dystrophy. In this symposium, we outline the molecular aspects of myotonic dystrophy including DNA diagnosis and anticipation, and review the similarities and differences among these triplet repeat diseases.     

Analysis of SCA1, DRPLA,MJD, SCA2, and SCA6 CAG repeats in 48 portuguese ataxia families

The spinocerebellar ataxias (SCAs) are clinically and genetically a heterogeneous group of neurodegenerative disorders. To date, eight different loci causing SCA have been identified: SCA1, SCA2, Machado-Joseph disease (MJD)/SCA3, SCA4, SCA5, SCA6, SCA7, and dentatorubropallidoluysian atrophy (DRPLA). Expansion of a CAG repeat in the disease genes has been found in five of these disorders. To estimate the relative frequencies of the SCA1, DRPLA, MJD, SCA2, and SCA6 mutations among Portuguese ataxia patients, we collected DNA samples from 48 ataxia families and performed polymerase chain reaction (PCR) amplification of the CAG repeat mutations on chromosomes 6p, 12p, 14q, 12q, and 19p, respectively. Fifty-five individuals belonging to 34 dominant families (74%) had an expanded CAG repeat at the MJD gene. In five individuals from two kindreds with a dominant pattern of inheritance (4%), an expanded CAG repeat at the SCA2 gene was found. In MJD patients, the normal allele size ranged from 13 to 41, whereas the mutant alleles contained 65 to 80 repeats. For the SCA2 patients, normal alleles had 22 or 23, while expanded alleles had between 36 and 47 CAG units. We did not find the SCA1, DRPLA, or SCA6 mutations in our group of families. The MJD mutation remains the most common cause of SCA in Portugal, while a small number of cases are caused by mutations at the SCA2 gene, and 22% are due to still unidentified genes. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 81:134–138, 1998. © 1998 Wiley-Liss, Inc.