人類遺傳疾病：第一部份：台灣帕金森氏症的分子遺傳研究； 第二部份：台灣杭丁頓氏症患者IT15基因CAG重複序列的單套型分析

Human Genetic Diseases:Part I: Molecular genetic studies of Parkinson's disease in Taiwan; Part II: DNA haplotype analysis of CAG repeat of the IT15 gene in Taiwanese Huntington's disease patients

王政光(Cheng-Kuang Wang)

指導教授 ： 李桂楨

國立臺灣師範大學/理學院/生命科學研究所/博士(2004年)

摘要

無資料

關鍵字

帕金森氏症 ； 基因多型性 ； 熱休克蛋白 ； 單套型 ； 杭丁頓氏症 ； HASH(0x9e6f948) ； HASH(0x9e6f9c0) ； HASH(0x9e7315c) ； HASH(0x9e731d4)

並列摘要

PartI:Abstract
Parkinson's disease (PD) is the second most common progressive neurodegenerative disorder of the elderly. It is characterized by resting tremor, rigidity, bradykinesia, and postural instability. The characteristic pathological features of PD include juxtanuclear ubiquitinated proteinaceous inclusions (Lewy bodies) in neuronal perikarya and neuronal processes, leading to selective loss of dopaminergic neurons in the substantia nigra pars compacta. alpha-synuclein, the main component of Lewy bodies, is a presynaptic protein encoded by the SNCA gene on chromosome 4q21-23. Previously, point mutations A53T and A30P in the highly conserved N-terminal portion of the Alpha-synuclein protein were shown to be more prone to fibrillogenesis in the transgenic and cellular studies, suggesting that Alpha-synuclein may have an important role in the development of PD. Recently, triplication and duplication of the Alpha-synuclein gene were reported to cause PD in several distinct families, indicating that a mere over-expression of wild-type Alpha-synuclein is sufficient to cause the disease. Although causal mutations in the gene for SNCA, parkin, ubiquitin carboxy-terminal hydrolase, DJ-1, PINK1, and LRRK2 were reported, mutations in these genes do not explain the occurrence of disease in most sporadic patients. Other genetic predisposition, most of which is not yet known, is thought to cause PD. In this study, the genetic variation in the SNCA, parkin, and HSP70 genes were investigated in a case-control study to examine the involvement in the susceptibility of Taiwanese to PD. The potential association of the genetic variation was further examined using a functional study. For the SNCA gene, while no statistically significant difference for the Rep1 microsatellite was observed, the C/C genotype (0.0% vs. 2.3%, P=0.0153) and C allele (8.9% vs.14.2%, P=0.0135) of RsaI T>C substitution were found less frequently in PD patients than in controls. In addition, haplotype analysis using Rep1 microsatellite and RsaI T>C substitution revealed significant difference for 0-T haplotype (29.6% vs. 22.6%, P=0.0287) and 0-C haplotype (6.9% vs. 12.1%, P =0.0082). An increased risk of the 0-T haplotype (odds ratio 1.54; 95% CI 0.36-0.90, P=0.0103) or a reduced risk of the 0-C haplotype (odds ratio 0.57; 95% CI 0.36-0.90, P=0.0177) was evident. In addition, the SNCA mRNA expression was different (although not significantly) between PD patients with RsaI T/T and T/C genotypes and reporter constructs containing the RsaI C allele cloned into a luciferase reporter plasmid drove significantly lower transcriptional activity compared with the RsaI T allele in both IMR32 and 293 cells. For the HSP70 genes, there was no statistically significant difference in genotype distribution between patients and controls for the three coding region polymorphisms in the HSP70-2 and HSP70-hom genes. However, for HSP70-1 gene, the overall genotype distribution was significantly different at the -110 A>C site (P = 0.004) and tended to be different at the +190 G>C site (P = 0.012) between patients and controls. The frequencies of the -110 CC and +190 CC genotypes were significantly higher in PD patients than controls (P = 0.001 and 0.006, respectively). Both -110 CC (odds ratio: 2.91; 95% CI: 1.51-5.96; P = 0.002) and +190 CC (odds ratio: 3.59; 95% CI: 1.53-9.88; P = 0.006) genotypes were significantly associated with PD. Reporter constructs containing the -110 A allele drove marginally higher transcriptional activity of HSP70-1 compared with the -110 C allele in both control and heat shocked IMR32 and 293 cells. For the parkin gene, one missense mutations (P437A) in addition to 3 exonic single nucleotide polymorphisms (SNPs) (S167N, R366W, and V380L) were identified. The association of exonic SNPs with the risk of PD was investigated and no statistically significant difference was found between PD patients and normal controls. The results suggest that the genetic variation in the SNCA and HSP70-1 genes, but not the parkin gene, may have a functional relevance to the susceptibility to sporadic PD.

PartII:Abstract
Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder characterized clinically by mid-life onset, progressive motor impairment, cognitive decline, and psychiatric symptoms. The disease is caused by the abnormal expansion of a CAG trinucleotide repeat (>35) in the first exon of the IT15 gene in chromosome 4p16.3. The normal range of CAG repeats is about 10 ~ 34, and repeats 36 ~ 39 triplets in length are incomplete penetrance. It shows a negative correlation between age of onset and the CAG repeats size. An interesting genetic feature of HD is anticipation which may be defined as worsening disease severity and early disease onset in successive generations. It is caused by CAG repeat expansions in the IT15 gene between generations, particularly when HD is inherited from the father. There is another triplet sequence, a CCG repeat, immediately 3' adjacent to the CAG repeats in the IT15 gene. It had been reported that the western HD chromosomes are strongly associated (CCG)7, and the Japanese HD chromosomes are mostly with (CCG)10. We studied the expanded CAG repeat and adjacent CCG repeat in 53 HD patients and 172 unrelated normal subjects matched to the patients for ethnic origin. The range of the CAG repeat varied from 38 to 109 in the HD patients and from 10 to 29 in the control group. A significant negative correlation was found between the age at onset and the CAG expansion, with no significant influence of the adjacent CCG repeat on the age at onset by multiple regression analysis. Allelic association using CCG repeat and 2 flanking dinucleotide repeat markers (D4S127, D4S412) within 150 kb of the HD gene revealed linkage disequilibrium for 2 of 3 markers. Haplotype analysis of 24 HD families using these markers identified 3 major haplotypes underlying 87.5% of HD chromosomes. The data suggested frequent haplotypes in the Taiwanese population on which one or more mutational events leading to the disease occurred.

並列關鍵字

Parkinson's disease ； polymorphism ； alpha-synuclein ； parkin ； heat-shock protein 70 ； NACP-Rep1 ； haplotype analysis ； polyglutamine disease ； Huntington's disease ； CAG trinucleotide repeat

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