中国两个高IgM综合征家系的基因诊断

Analysis of the Gene Mutations in Two Pedigrees with Hyper-IgM Syndrome

目的 对中国两个高IgM综合征（HIGM）家系进行基因突变检测,并应用生物信息学软件加以分析诊断.方法 该研究以2012年中国贵州省收治的两名HIGM先证者（男孩）及其家系成员为研究对象,对先证者的CD40LG,AICDA,CD40和UNG基因外显子及其侧翼序列进行扩增,PCR产物经纯化后Sanger法测序.应用Mutation Surveyor软件检测序列图谱中所有的基因变异点,并运用Alamut软件预测变异的致病性.同时选取100位排除患有HIGM疾病健康者的DNA,作为基因多态性对照.结果 基因测序分析发现：第1例先证者为7岁男孩,其CD40LG基因第5外显子存在错义突变p.Gly167Arg（c.499G〉C）,该患者母亲携带此错义突变;第2例先证者为3岁男孩,其CD40LG基因第1外显子存在单碱基缺失c.114delG,导致39位后编码氨基酸发生移码突变,并在53位引入终止密码,形成截断型蛋白（p.Ser39GlnfsX14）,患者母亲同样携带此突变.两个突变均未在100位排除患有HIGM疾病健康者中发现.结论 该研究建立了HIGM准确、简便的基因突变筛查办法,CD40LG基因c.114delG突变为国际上首次报道.

Objective To identify the gene mutations of two pedigrees from China with hyper-IgM syndrome（HIGM）and analyze pathogenicity by bioinformaties software. Methods This research included two probands（male） who were admitted to the hospital in 2012 from Guizhou Province,their family members and one hundred healthy people as control. All exons and exon-intron boundaries sequences of CD40LG, AICDA, CD40 and UNG genes were amplified by PCR from the probands＇ genomic DNA. The amplified products were purified and analyzed by direct Sanger sequencing. This research applied Mutation Surveyor software to identify all the mutations in the sequence map and used Alamut software to predict the pathogenicity of these mutations. Results Gene analysis revealed that the first proband was a 7-year-old male who had a c. 499G^C mutation in exon 5 of CD40LG gene, which would cause the missense mutation p. Gly167Arg. A novel single-base deletion （c.114delG） was found in the second proband who was a3-year-old male in exon 1 of CD40LG gene. The mutation caused a frameshift from 39-amino acid site and a premature terminating code was introduced at 53-amino acid site, producing a truncated protein （p. Ser39GlnfsX14）. Two probands＇ mothers carried the same mutations as their children. Same mutations hadn＇t been identified among the 100 healthy people. Conclusion An accurate and simple gene diagnostic method for HIGM was established. One novel CD40LG gene mutation （c. 114delG） was identified.