摘要:巴金森氏症(巴病, Parkinson’s disease, PD)為最常見的神經退化性疾病之ㄧ,平均發生率佔60 歲以上老年人口1-2%。目前此病症並無根治之治療方法,臨床上的治療方針仍侷限在多巴胺的補充,病情仍會隨病患年齡增加而益趨惡化。隨著分子遺傳學的進步,目前已有21個巴病易感基因座與12個致病基因的突變被證實是引起少數遺傳性巴病的致病基因。雖然在全球不同族群中已進行了許多巴病致病基因的相關研究,但目前仍有許多問題未獲解答,例如>80%的病患仍沒有確切的基因診斷或是基因危險因子被發現,同時,所有巴病相關基因的檢測在技術上有一定的門檻,只有少數醫學中心能提供檢測而且價錢所費不貲(每人需要大約美金2000到3000元),檢驗需個別基因單獨分析並常需要數星期才能完成所有巴病基因的檢測。此外,許多新近發現的巴病致病基因的個案數太少,例如FBXO7、VPS35、DNAJC6、DNAJC13、SYNJ1基因等,因而無法清楚瞭解其導致多巴胺神經細胞退化的分子機轉,更不可能進一步從其中發現有助於改善巴病病程的方法。目前,在我們華人族群中,巴病的基因研究多侷限在以大規模的病例-對照組方式(case-control study)分析已知基因的變異點位; 探究新穎巴病致病基因的研究並不普遍。本計畫將針對在不明病因的本土遺傳性巴病家族(familial PD pedigree)中找出新穎的致病基因及其突變。吾人團隊在過去10年內已募集約200位彼此不具親屬關係的遺傳性巴病病患(probands),並針對目前所知有可能導致遺傳性巴病的致病基因進行Sanger定序或是copy number variation分析。對於顯性遺傳型巴病的病患,我們檢測分析SNCA、LRRK2、SCA2以及SCA3 等基因。對於隱性遺傳型巴病的病患,我們檢測分析Parkin、PINK1、ATP13A2以及PLA2G6等基因。同時,本計劃預計建立一個以次世代定序(next generation sequencing, NGS)為基礎的PD 基因genetic test panel,以同時進行 12個已知巴病基因的突變分析,希望此穩固的平台架構能夠長久地支援巴病患者的基因診斷與個人化基因體醫療,而且我們也可以提供院內外巴病患者以次世代定序為基礎的基因檢測服務。其次,經過上述廣泛的致病基因分析而找不到已知巴病致病基因突變且為顯性遺傳的家族,如果能召募多位家族成員,其中包括2-3 位以上的巴病患者,我們將進一步利用次世代全外顯子定序技術(whole exome sequencing)方法來尋找此家族所可能帶有的新穎致病基因突變。Whole exome sequencing 即是利用whole exome capture 及next-generation sequencing 的技術,將一個人身上所有基因的exons 都進行定序。近幾年已有許多遺傳疾病運用此方法找出新的致病基因。我們目前已初步完成一個顯性遺傳家族的whole exome sequencing,目前正準備進行下一步的細胞功能性分析。我們預期本計畫除能建立臺灣遺傳性巴病的分子基因診斷策略之外,並且可能發現新的遺傳性巴病致病基因。本研究結果將可提供另一途徑來探究遺傳性巴病的病因,進一步釐清各致病基因在此疾病的分子生理機轉,並將有助於未來發展新型mechanism-based的巴病治療策略。
Abstract: Parkinson disease (PD) is the most common neurodegenerative movement disorder with age-related prevalence and results from interplay between genetic and environmental factors. In the past 15 years there has been substantial progress in the understanding of the genetics of PD. Genome-wide association studies identified common variants in more than 20 loci, modulating the risk of developing PD. Highly-penetrant mutations in different genes (SNCA, LRRK2, VPS35, Parkin, and PINK1) are known to cause rare monogenic forms of the disease. Furthermore, different variants with incomplete penetrance in these PD candidate genes are strong risk factors for PD.Although numerous studies of PD have been conducted worldwide before, many issues still remain unsolved, including that more than 90% of PD patients do not have a clear genetic diagnosis, the pathomechanism of many newly-identified mutations in PD are unclear, and the complete information of genetic factors contributing to PD in Chinese population remains limited.In this project, we plan to conduct a very comprehensive genetic survey of the familial PD patients and, furthermore, identify novel PD causative genes from these families. We have recruited more than 200 unrelated Taiwanese PD patients with positive family history, consisting with either autosomal-recessive or autosomal-dominant inheritance traits. At the first step, we plan to analyze all the recessive and dominant PD-related genes according to their onset age and inheritance patterns. We will evaluate the presence of mutations in genes involved in late-onset and dominantly-inherited PD (SNCA, LRRK2, VPS35, and eIF4G1), early-onset and recessively-inherited PD (Parkin, PINK1, PLA2G6, ATP13A2, FBXO7 and SYNJ1). In addition, boarder-line triplet repeat expansions in SCA2, SCA3, and C9orf72 will also be ruled out. The genotype and phenotype features will be correlated. In the second step of this project, for those genetically unassigned pedigrees with dominant PD, we will utilize the whole exome sequencing-based method, which can sequence all the exons of an individual, to search for novel causative genes. This method had successfully helped identify the causative genes of many other hereditary diseases in recent years. We have previously identified one autosomal-dominant PD pedigree without mutations in any known PD-causing genes after extensive survey. Using whole exome sequencing analysis, we found several potential novel PD candidate genes contributing to this index autosomal-dominant PD family. We will continue to verify the final causative gene for this family and perform functional study to investigate the cellular effect of this novel mutated gene. Our work will establish a comprehensive set of molecular testing for PD patients, and very possibly identify novel causative genes of familial Taiwanese PD. Our study will lead to a better understanding of the underlying genetic mechanism of PD.