摘要
Objective To make early diagnosis of IT15 gene mutation in a Wuhan juvenile-onset Huntington disease （HD） family, for providing them with genetic counseling, and making preparation for the further research on pathogenesis and experimental therapy of HD. Methods According to the principle of informed consent, we extracted genomic DNA from peripheral blood samples and carried genetic diagnosis of pathogenic exon 1 of IT15 gene by modified touchdown PCR and DNA sequencing methods. Results Eight of twenty-five family members carried abnormal allele： Ⅲ10 Ⅲ12, IIIt4, Ⅳ3, and Ⅴ2 carded （CAG） 48, Ⅳ11 and Ⅳ12 carried （CAG） 67, and Ⅳ14 carried （CAG） 63, in contrast with the 8-25 CAG trinucleotides in the members of control group. Ⅳ14 carried 15 more CAG trinucleotides than her father Ⅲ10. Conclusion The results definitely confirm the diagnosis of HD and indicate the CAG trinucleotide repeat expansion of IT15 gene in this HD family. In addition, CAG expansion results in juvenile-onset and anticipation （characterized by earlier age of onset and increasing severity） of the patientⅣ12.
目的对青少年发病的亨廷顿舞蹈病(Huntington disease)家系进行致病IT15基因早期诊断分析,为家系成员提供遗传咨询, 并为后续的HD发病机制及实验治疗研究提供依据。方法按照知情同意原则抽取家系成员外周血,提取基因组DNA,采用改良的降落PCR方法扩增IT15基因致病区域,DNA测序检测异常等位基因(CAG) n 三核苷酸重复次数。结果在该家系三代25名成员中,共发现8名致病IT15基因携带者,其中,III10、III12、III14、IV3和V2 CAG三核苷酸的拷贝数均为48,IV11和IV12均为(CAG) 67, IV14为(CAG) 63,而对照组35名正常人的CAG三核苷酸的拷贝数为8-25,两者之间没有重叠。结论家系中第四代致病基因携带者IV14与第三代患者III10比较,CAG三核苷酸重复次数增加15次,即本家系IT15基因在传递过程中发生了扩增突变。同时,扩增突变导致该家系出现青少年发病及遗传早现现象。
