中国人遗传性脊髓小脑型共济失调患者三核苷酸突变频率的分布

SCA 1, SCA2, MJD/SCA3 (CAG)n mutation detection and analysis in patients with hereditary spinocerebellar ataxia from Chinese families

目的评价ＳＣＡ１、ＳＣＡ２、ＭＪＤ／ＳＣＡ３ＣＡＧ三核苷酸扩增突变（ＣＡＧ）ｎ在中国人遗传性脊髓小脑型共济失调（ＳＣＡ）患者的分布频率。方法应用聚合酶链式反应（ＰＣＲ）和变性聚丙烯胺凝胶电泳技术，检测分析了５０名中国人常染色体显性遗传ＳＣＡ家系（其中患者７９例）的ＳＣＡ１、ＳＣＡ２、ＭＪＤ／ＳＣＡ３（ＣＡＧ）ｎ。结果在５０个ＳＣＡ家系中，１个ＳＣＡ家系有ＳＣＡ１（ＣＡＧ）ｎ突变，３个ＳＣＡ家系有ＳＣＡ２（ＣＡＧ）ｎ突变，２４个ＳＣＡ家系有ＭＪＤ／ＳＣＡ３（ＣＡＧ）ｎ突变，阳性率分别为２．０％、６．０％、４８．０％。２例ＳＣＡ１患者ＣＡＧ三核苷酸重复数为５３和６２次，而正常人为１２～３６次。７例ＳＣＡ２患者ＣＡＧ三核苷酸重复数４３～４７次，而正常人为２２～３０次。４２例ＭＪＤ／ＳＣＡ３患者ＣＡＧ三核苷酸重复数６３～７８次，而正常人为１５～３８次。另有２２个ＳＣＡ家系２８例患者，ＳＣＡ１、ＳＣＡ２、ＭＪＤ／ＳＣＡ３（ＣＡＧ）ｎ突变检测在正常范围内。结论中国ＳＣＡ主要为ＭＪＤ／ＳＣＡ３型，属于非葡萄牙型ＭＪＤ；而ＳＣＡ１型、ＳＣＡ２型少见。

bjective To assess the frequency of the SCA1, SCA2, MJD/SCA3 CAG trinucleotide repeat expansions ((CAG)n) among individuals diagnosed with hereditary spinocerebellar ataxia (SCA) from Chinese families. Method The SCA1, SCA2, MJD/SCA3 (CAG)n mutation were detected with the polymerose chain reaction (PCR), denaturing polyacrylamide gel and silver staining technique in 79 patients with autosomal dominant SCA from 50 Chinese families. Results Among 50 kindreds, 2%(1/50) had the SCA1 (CAG)n, 6% (3/50) had the SCA2 (CAG)n, whereas 48%(24/50) were positive for the MJD/SCA3 (CAG)n. Thus, together SCA1, SCA2 and MJD/SCA3 represent 56%(28/50) of the autosomal dominant ataxias in our group. In two SCA1 patients the CAG repeat was expanded to 53～62 repeats, whereas in normal ivdividuals was 12～36 repeats. In seven SCA2 patients the CAG repeat was expanded to 43～47 repeats, whereas in normal ivdividuals was 22～30 repeats. In fortytwo MJD/SCA3 patients the CAG repeat was expanded to 63～78 repeats, whereas in normal ivdividuals was 15～38 repeats. The SCA1, SCA2,MJD/SCA3(CAG)n mutation were excluded in the other 28 SCA patients from 22 families. Conclusion The frequency of MJD/SCA3 is substantially higher than that of SCA1 and SCA2 in the autosomal dominant SCA from Chinese families. Chinese patients with MJD/SCA3 are nonPortuguese patients with MJD/SCA3. Clinical expressions of the various SCAs overlap one another, making a diagnostic classification based on phenotype inaccurate in many instances. It is important for SCA clinical study to make a SCA gene diagnosis and genomic classification.