中国羌族人群强直性肌营养不良症基因CTG重复序列多态性研究

Studies of the Polymorphism of CTG Trinucleotide Repeats of Myotonic Dystrophy Gene in Qiang Nationality in China

强直性肌营养不良症是由于ＭＴ－ＰＫ基因３′非编码区ＣＴＧ三核苷酸重复序列的过度扩展所致。正常人群中ＣＴＧ的拷贝数为５～３０，而患者在５０以上，且具民族差异。目前尚无我国羌族人群的有关资料。为了解中国羌族人群该基因３′ＵＴＲＣＴＧ三核苷重复序列的分布情况，作者采用ＰＣＲ、聚丙烯酰胺凝胶电泳、银染和测序等技术，对６０例正常羌族人的ＣＴＧ重复序列进行了分析。共发现８种等位基因，其中ＣＴＧ拷贝数为５的等位基因最为常见，占３０８３％，其余依次为１３拷贝（２２５％）、１２（１９１７％）、１１（１５８３％）、１４（５８３％）和１５（４１７％）；拷贝数大于１５的等位基因极少，仅检测到一例，为２７拷贝；ＣＴＧ拷贝数在６～１０之间的等位基因也很少，仅发现一例为９拷贝，而该等位基因在其它人群尚无报道。６０名个体中共发现纯合子１８例，其中９例为５／５，２例为１１／１１，２例为１２／１２，４例１３／１３和１例为１５／１５，杂合率为７０％。本系统的多态信息量（ＰＩＣ）为０７７。羌族和汉族人群该位点的多态性无显著差异。

Myotonic dystrophy is associated with an increased number of CTG repeats in the 3′UTR of the myotonic protein kinase gene(MT-PK) located on chromosome 19q13.3 The triplet repeats region of the gene of 60 healthy Qiang subjects from Sichuan province was analyzed by polymerase chain reaction and polyacrylamide gel electrophoresis A total of 8 alleles were found ranging in size from 5 to 27 copies with the most common allele of 5 copies (3083%) The other major alleles were 11, 12 and 13 copies with frequency of 15.83%, 19.17% and 22.5%, respectively An allele of 9 copies was found in a Qiang individual which has never been reported before in other populations Only 5.83% of alleles were longer than 14 copies and one longer than 15 copies Heterozygote frequency in this population was 70% The CTG repeats is highly informative with a PIC value of 0.77 There is no significant difference between Qiang and Han population in the distribution of the CTG allele frequencies