[Studies on the CAG repeat expansion in patients with hereditary spinocerebellar ataxia from Chinese Han].
OBJECTIVE
To investigate the CAG trinucleotide 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); thirty-two 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 SCA7, 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).


CONCLUSIONS
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.
Wang
Junling
J
Department of Neurology, Xiangya Hospital, Central South University, Changsha, Hunan, 410008 PR China.
Xu
Qian
Q
Lei
Lifang
L
Shen
Lu
L
Jiang
Hong
H
Li
Xiaohui
X
Zhou
Yafang
Y
Yi
Jiping
J
Zhou
Jie
J
Yan
Xinxiang
X
Pan
Qian
Q
Xia
Kun
K
Tang
Beisha
B
D000293:Adolescent; D000328:Adult; D000368:Aged; D044466:Asian People / Q000208:ethnology / Q000235:genetics*; D000067719:Ataxin-7; D000067528:Ataxins; D001483:Base Sequence; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics; D054648:Protein Phosphatase 2 / Q000235:genetics; D020754:Spinocerebellar Ataxias / Q000208:ethnology / Q000235:genetics*; D019680:Trinucleotide Repeat Expansion; D055815:Young Adult
C000593829:ATXN7 protein, human; D000067719:Ataxin-7; D000067528:Ataxins; D009419:Nerve Tissue Proteins; C505936:PPP2R2B protein, human; D054648:Protein Phosphatase 2