2010年11月23日，由深圳華大基因研究院,、中南大學(xué)湘雅醫(yī)院等單位合作研究的成果“利用全外顯子組測(cè)序技術(shù)發(fā)現(xiàn)小腦共濟(jì)失調(diào)新的致病基因TGM6”在國(guó)際知名雜志Brain上在線發(fā)表,，這是我國(guó)科學(xué)家應(yīng)用外顯子組測(cè)序技術(shù)進(jìn)行單基因病研究的一項(xiàng)突破,，對(duì)促進(jìn)國(guó)內(nèi)單基因病研究的發(fā)展具有重要意義。
該研究對(duì)患有小腦共濟(jì)失調(diào)的同一家系4個(gè)患者進(jìn)行了全外顯子組測(cè)序,，在每個(gè)患者的外顯子區(qū)域平均檢測(cè)到約5800個(gè)潛在影響基因功能的變異,，包括非同義突變（NS）、剪切位點(diǎn)突變（SS）和插入缺失突變（Indel）,，其中包含了大量的罕見(jiàn)變異,。研究人員通過(guò)生物信息學(xué)分析，將候選致病基因突變鎖定為TGM6基因第10外顯子保守區(qū)域的一個(gè)錯(cuò)義突變,。進(jìn)一步研究發(fā)現(xiàn),，在另一個(gè)患有該病的家系里，TGM6基因同樣存在錯(cuò)義突變,，從而證實(shí)TGM6基因是小腦共濟(jì)失調(diào)家族的新致病基因,，屬于SCA23亞型。該研究還對(duì)測(cè)序的家系同步進(jìn)行了定位克隆,，通過(guò)連鎖分析將致病位點(diǎn)定位在20號(hào)染色體短臂的8.4Mb的區(qū)域,，該區(qū)域包含了91個(gè)基因，TGM6基因正是其中之一,。
小腦共濟(jì)失調(diào)是一種常染色體顯性遺傳的神經(jīng)系統(tǒng)疾病,，疾病臨床常表現(xiàn)為運(yùn)動(dòng)失調(diào)。應(yīng)用傳統(tǒng)的定位克隆方法已經(jīng)在人類基因組上定位了對(duì)應(yīng)不同亞型的31個(gè)位點(diǎn),，并確定了其中19個(gè)亞型的致病基因,。但是，定位克隆方法只能將候選致病基因定位到基因組上的一段區(qū)域,，并不能確定致病基因,，因此具有很大的局限性,。而外顯子組測(cè)序技術(shù)不僅可以直接檢測(cè)到包括罕見(jiàn)突變?cè)趦?nèi)的大量突變,，還能進(jìn)一步通過(guò)生物信息分析確定候選致病基因。TGM6基因的發(fā)現(xiàn),，對(duì)今后闡明該病發(fā)病機(jī)制,、遺傳診斷和新藥研發(fā)具有重要的研究和應(yīng)用價(jià)值。
新一代測(cè)序技術(shù)的產(chǎn)生和發(fā)展為疾病研究帶來(lái)了新的機(jī)遇,。作為一種高效,、快速和高性價(jià)比的研究方法，全外顯子組測(cè)序技術(shù)已經(jīng)開(kāi)始應(yīng)用于遺傳病的研究,。自2009年以來(lái),，國(guó)際頂級(jí)雜志上相繼報(bào)道了十多篇將外顯子組測(cè)序技術(shù)應(yīng)用于單基因病的研究成果。華大基因的科學(xué)家采用外顯子測(cè)序技術(shù)也取得多項(xiàng)重要研究成果,。他們對(duì)50個(gè)藏族人的進(jìn)行外顯子測(cè)序和分析找到與藏族人高原適應(yīng)性密切相關(guān)的基因,，文章發(fā)表在《科學(xué)》雜志上,；通過(guò)與丹麥的科研機(jī)構(gòu)合作，華大基因?qū)?00個(gè)丹麥人的外顯子進(jìn)行了測(cè)序研究,，證實(shí)了人群中存在大量低頻率非同義突變,，文章發(fā)表在《自然—遺傳學(xué)》上。外顯子組測(cè)序技術(shù)已經(jīng)得到國(guó)際單基因病領(lǐng)域科學(xué)家的廣泛認(rèn)可,，也將越來(lái)越多的應(yīng)用于單基因疾病的研究中,。這將對(duì)確定單基因病的致病基因的發(fā)現(xiàn)產(chǎn)生巨大推動(dòng)作用。利用測(cè)序技術(shù)替代傳統(tǒng)的定位克隆研究方法,，或?qū)⒍呦嘟Y(jié)合,，已成為研究學(xué)者們進(jìn)行人類遺傳疾病研究的又一新途徑。
華大基因于2010年5月啟動(dòng)了“千種單基因病計(jì)劃”,，希望通過(guò)與國(guó)內(nèi)外單基因病研究領(lǐng)域的科學(xué)家合作,，充分利用華大基因先進(jìn)的基因組測(cè)序技術(shù)和強(qiáng)大的生物信息分析能力，將豐富的單基因病遺傳資源轉(zhuǎn)化為新的科學(xué)發(fā)現(xiàn),，促進(jìn)單基因病研究的發(fā)展,。(生物谷Bioon.com)
生物谷推薦英文摘要：
Brain (2010) doi: 10.1093/brain/awq323
TGM6 identified as a novel causative gene of spinocerebellar ataxias using exome sequencing
Jun Ling Wang1,2,*, Xu Yang3,*, Kun Xia2,*, Zheng Mao Hu2, Ling Weng1, Xin Jin3,4, Hong Jiang1,5, Peng Zhang3, Lu Shen1,5, Ji Feng Guo1,5, Nan li1, Ying Rui Li3, Li Fang Lei1, Jie Zhou1, Juan Du1, Ya Fang Zhou1, Qian Pan2, Jian Wang3, Jun Wang3,6, Rui Qiang Li3,6 and Bei Sha Tang1,2,5
1 Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan province 410008, China
2 National Key Lab of Medical Genetics of China, Changsha, Hunan province 410008, China
3 BGI-Shenzhen, Shenzhen, Guangdong province 518083, China
4 Innovative Program for Undergraduate Students, School of Bioscience and Biotechnology, South China University of Technology, Guangzhou 510641, China
5 Neurodegenerative Disorders Research Center, Central South University, Changsha, Hunan province 410008, China
6 Department of Biology, University of Copenhagen, Copenhagen DK-2200, Denmark
Autosomal-dominant spinocerebellar ataxias constitute a large, heterogeneous group of progressive neurodegenerative diseases with multiple types. To date, classical genetic studies have revealed 31 distinct genetic forms of spinocerebellar ataxias and identified 19 causative genes. Traditional positional cloning strategies, however, have limitations for finding causative genes of rare Mendelian disorders. Here, we used a combined strategy of exome sequencing and linkage analysis to identify a novel spinocerebellar ataxia causative gene, TGM6. We sequenced the whole exome of four patients in a Chinese four-generation spinocerebellar ataxia family and identified a missense mutation, c.1550T–G transition (L517W), in exon 10 of TGM6. This change is at a highly conserved position, is predicted to have a functional impact, and completely cosegregated with the phenotype. The exome results were validated using linkage analysis. The mutation we identified using exome sequencing was located in the same region (20p13–12.2) as that identified by linkage analysis, which cross-validated TGM6 as the causative spinocerebellar ataxia gene in this family. We also showed that the causative gene could be mapped by a combined method of linkage analysis and sequencing of one sample from the family. We further confirmed our finding by identifying another missense mutation c.980A–G transition (D327G) in exon seven of TGM6 in an additional spinocerebellar ataxia family, which also cosegregated with the phenotype. Both mutations were absent in 500 normal unaffected individuals of matched geographical ancestry. The finding of TGM6 as a novel causative gene of spinocerebellar ataxia illustrates whole-exome sequencing of affected individuals from one family as an effective and cost efficient method for mapping genes of rare Mendelian disorders and the use of linkage analysis and exome sequencing for further improving efficiency.
