遗传性痉挛性截瘫新突变的全基因组外显子测序分析

AN ANALYSIS OF A NOVEL MUTATION IN A CHINESE FAMILY WITH HEREDITARY SPASTIC PARAPLEGIAS BY WHOLE EXOME SEQUENCING

目的通过对一个汉族常染色体显性遗传的痉挛性截瘫家系进行全基因组外显子测序分析,找出致病的基因突变位点,探索基因型-表型关系,为该病产前诊断提供理论依据。方法收集一个汉族遗传性痉挛性截瘫家系,对先证者(Ⅳ11)、先证者患病姐姐(Ⅳ8)和未患病哥哥(Ⅳ9)进行神经系统体格检查,提取基因组DNA并进行全基因组外显子测序分析,将可疑基因突变在50例健康对照和该家系Ⅲ、Ⅳ代6例病人及13例正常人中进行Sanger测序验证,应用DNAMAN生物信息学分析软件预测该可疑突变的危害性。结果该家系中6例病人均在SPG4(SPAST)基因第14外显子的同一位点(c.1606C>T,p.Gln536X)处发生突变,50例健康对照和家系中13例正常人均未发现该突变。生物信息学软件分析第536位氨基酸位于保守序列区域,该突变使SPG4基因编码氨基酸序列缩短,对蛋白质功能具有较强的危害性。结论 SPG4基因c.1606C>T突变是该遗传性痉挛性截瘫家系的致病突变位点,且为首次报道,该发现为遗传性痉挛性截瘫的诊断及产前诊断提供了依据。

Objective To identify the causative gene mutation and explore the genotype-phenotype association through whole exome sequencing（WES）of a Chinese Han family with autosomal dominant hereditary spastic paraplegia（HSP）,and to provide a theoretical basis for prenatal diagnosis of HSP. Methods A Chinese Han family with HSP was selected.Neurological examinations were performed on the proband（Ⅳ11）,proband＇s sister with HSP（Ⅳ8）,and proband＇s brother without HSP（Ⅳ9）.Genomic DNA was extracted for WES.The suspected gene mutation was subjected to Sanger sequencing among 50 healthy controls as well as 6 patients and 13 normal subjects in the third and fourth generations of this family,and its harm was predicted using DNAMAN software. Results A novel nonsense mutation in exon 14 of the SPG4（SPAST）gene（c.1606 CT,p.Gln536 X）was found in the 6 patients of this family,but it was not found in the 50 healthy controls and the 13 normal subjects of this family.The DNAMAN analysis identified a single-nucleotide change from C to T causing a substitution from glutamine to an immature stop codon at codon 536.This mutation co-segregated with the phenotype of HSP patients in this family. Conclusion The novel nonsense mutation in the SPG4 gene（c.1606 CT,p.Gln536 X）is the causative mutation in the family with HSP,which provides a basis for prenatal diagnosis of HSP.