中文摘要：

目的研究中国汉族人群脊髓小脑性共济失调（spinocerebellarataxia，SCA）1、2、3、6、7、12、17亚型致病基因的CAG三核苷酸病理重复次数范围。方法应用聚合酶链反应、琼脂糖凝胶电泳、T载体克隆重组DNA技术并结合直接测序等技术对559例临床诊断为SCA的患者（363例常染色体显性遗传先证者，196例散发患者）进行SCA1、SCA2、SCA3／马查多-约瑟夫病（Maehado—Josephdisease，MJD）、SCA6、SCA7、SCA12和SCA17致病基因CAG三核苷酸病理重复次数突变分析。结果在559例SCA患者中，共检测出SCA1患者23例，CAG病理重复次数范围39～60次，平均（51．09±4．88）次；SCA2患者32例，CAG病理重复次数范围36～51次，平均（40．34±4．40）次；SCA3／MJD患者305例，CAG病理重复次数范围49～86次，平均（73．84±5．07）次；SCA6患者9例，CAG病理重复次数范围23～29次，平均（25．56±1．94）次；SCA7患者27例，CAG病理重复次数范围38～71次，平均（58．22±10．90）次；SCA12患者3例，CAG病理重复次数范围51～52次，平均（51.33±0．58）次；SCA17患者2例，CAG病理重复次数范围53～55次，平均（54．00±1．41）次。结论SCA1的39次CAG病理重复、SCA3／MJD的49次CAG病理重复和SCAl2的51次CAG病理重复为国内或国外报道的最小CAG病理重复次数；SCA3／MJD的86次CAG病理重复为国内外报道的最大CAG病理重复次数；SCA17为国内首次发现的SCA亚型；首次建立中国汉族人群不同SCA亚型CAG三核苷酸病理重复次数范围标准。

英文摘要：

Objective To investigate the CAG trinueleotide repeat expansion in spinocerebellar ataxia （SCA） types 1, 2, 3, 6, 7, 12, and 17 from Chinese Han. Methods The pathological CAG triplet repeat expansions of the SCA1, SCA2, SCA3/Machado Joseph disease（MJD）, SCA6, SCA7, SCA12 and SCA17 genes were analyzed in a cohort of 559 Mainland Chinese patients affected by spinocerebellar ataxia, including 363 probands from families with autosomal dominant SCA and 196 sporadic cases. Polymerase chain reaction, agarose gel electrophoresis, recombinant DNA technology by T-vector cloning and direct sequencing were performed to detect the CAG-repeat number of abnormal allele. Results Among the 559 SCA patients, twenty three were positive for SCA1, the ranges of expanded CAG repeats were from 39 to 60 （mean： 51.09±4. 88）; thirtytwo were positive for SCA2, the ranges of expanded CAG repeats were from 36 to 51 （mean：40.34±4.40）; three hundred and five were positive for SCA3/MJD, the ranges of expanded CAG repeats were from 49 to 86 （mean：73.84±5.07） ; nine were positive for SCA6, the ranges of expanded CAG repeats were from 23 to 29 （mean：25.56±1.94） ; twenty-seven were positive for SCAT, the ranges of expanded CAG repeats were from 38 to 71 （mean： 58. 22±10. 90）; three were positive for SCA12, the ranges of expanded CAG repeats were from 51 to 52 （mean：51.33±0.58）; and finally , two were positive for SCA17, the range of expanded CAG repeats were from 53 to 55 （mean：54.00± 1.41）. Conclusion The 39 CAG repeats of SCA1, 49 CAG repeats of SCA3 and 51 CAG repeats of SCA12 are all the shortest known causative expanded alleles, while the 86 CAG repeats of SCA3/MJD is the largest full expanded allele that has never been reported. Furthermore, it is the first report of SCA17 subtype in Mainland Chinese and first research that established the abnormal reference standard of CAG repeat number of different subtypes of SCA in Chinese Han.