一个非CTG非CCTG重复扩展型强直性肌营养不良家系

目的　探讨一个强直性肌营养不良 (myotonic dystrophy,DM)家系的分子遗传学基础。方法　采用长模板 PCR扩增、Southern印迹技术和特定染色体区域的基因组扫描技术 ,检测一个强直性肌营养不良家系成员 DMPK基因中 CTG及 ZNF9基因中 CCTG短串重复拷贝数。结果　家系中接受检测的2 6个成员中 ,两种序列的重复拷贝数均在正常范围内 ,即 :(1)该家系中无 DM1DMPK基因 (CTG) n重复数的异常增加 ;(2 )该家系中无 DM2 ZNF9基因 (CCTG) n重复的异常增加 ;(3)受检者相隔 4年的两次血样标本中 ,DMPK基因 (CTG) n重复的拷贝数无明显差异。DMPK及 ZNF9两侧微卫星标志的 L od值均小于 1。结论　除 CTG、CCTG短串联重复序列异常扩展外 ,可能存在新的强直性肌营养不良的致病基因。

A pedigree with myotonic dystrophy:non-CTG, non-CCTG repeat expansion

Objective Two genetic loci are associated with the myotonic dystrophy (DM) phenotype: DM1 DMPK on chromosome 19, and DM2 ZNF9 on chromosome 3. The aim of this study was to investigate the molecular genetics of a pedigree with DM. Methods In twenty-six individuals from a family with DM, the CTG repeats in DMPK and CCTG repeats in ZNF9 were evaluated genetically, using Long Expand TM Template polymerase chain reaction (PCR), Southern blotting and genomic scanning. Results The numbers of CTG and CCTG repeat were all in normal range. There was no significant difference between the CTG repeat size in DMPK gene and that 4 years later from the same individual. The Lod score values with short tandem repeats STR markers chosen in 19q and 3q were all smaller than 1, which suggested that no STR marker was linked with this DM family. Conclusion There might be some other mutant in this DM pedigree. Further study should be done to find the genetic basis of this pedigree.