2例CHD2基因突变相关癫痫临床表型及遗传学分析

Clinical phenotype and genetic analysis of CHD2 gene related epilepsy in 2 cases

目的分析2例CHD2基因突变相关癫痫患儿临床资料,探讨其临床表型和基因突变特点。方法收集2例CHD2基因突变相关癫痫患儿(先证者)及其家系临床资料,采集先证者及其父母外周血,提取基因组DNA,采用高通量测序法对先证者外显子及旁侧内含子区域进行测序,确定基因突变位点,采用PCR-Sanger测序法验证。应用UCSC软件分析先证者突变位点保守性,应用Varseak、Mutation Taster软件分析突变位点致病性。结果2例患儿均约3岁出现抽搐。先证者1表现为强直阵挛发作,诊断为癫痫、孤独症谱系障碍,给予丙戊酸钠、左乙拉西坦治疗后发作控制;存在CHD2基因c.2877-1_2877delGCinsAA杂合突变,为剪接受体突变;13个物种c.2877-1位点对应的碱基(C)、c.2877位点对应的氨基酸(天冬酰胺)均呈高度保守性;家系验证及基因数据库提示为新发突变,Varseak软件分析结果提示该突变导致蛋白序列和结构变化,ACMG评级为可能致病。先证者2存在多种癫痫发作形式,合并重度发育迟缓,诊断为Lennox-Gastaut综合征,给予多种药物治疗效果差,后给予左乙拉西坦治疗后发作控制;存在CHD2基因c.361C>T(p.Arg121Ter)杂合突变,为无义突变;13个物种c.361C>T位点对应的121号氨基酸(精氨酸)均呈高度保守性;家系验证为新发突变,Mutation Taster软件分析结果提示为疑似致病性突变,ACMG评级为致病。结论伴发育迟缓、孤独症谱系障碍的癫痫患者应考虑CHD2基因突变,基因检测有助于早期诊断。

Objective To analyze the clinical data of 2 cases of CHD2 gene related epilepsy and to investigate their phenotypes and gene mutation types.Methods The clinical data of 2 probands and their families were collected.The peripheral blood of the probands and their parents was extracted for genomic DNA.High-throughput sequencing was used to detect the exons and their intronic regions to define the gene mutation sites,and the pathogenic variations were verified by PCR-Sanger sequencing.The conservativeness of gene variation sites in the probands was analyzed by UCSC softwares,and the pathogenicity of variation sites was analyzed by using the Varseak and Mutation Taster softwares.Results Convulsions developed in two patients at the age of about 3 years old.Proband 1 was manifested with tonic-clonic seizures,which was controlled by levetiracetam and sodium valproate treatment after being diagnosed as epilepsy and autism spectrum disorder.This proband was detected heterozygous mutation of CHD2 gene c.2877-1_2877delGCinsAA,which was a splicing receptor mutation.The corresponding base(C)at C.2877-1 and the corresponding amino acid(asparagine)at c.2877 were highly conserved in 13 species.Parental verification and query of human gene database indicated that it was a de novo mutation.The analysis results of Varseak predicted that the mutation would lead to changes in protein sequence and structure,and was possibly pathogenic according to the ACMG classification.Proband 2 was diagnosed with Lennox-Gastaut syndrome,with multiple seizure patterns combined with severe developmental delay.Seizures were controlled after treatment with levetiracetam,while other drugs had poor efficacy.There was a heterozygous mutation of CHD2 gene c.361C>T(p.Arg121Ter),which was a nonsense mutation.The 121amino acid(arginine)corresponding to the c.361C>T mutation was highly conserved in 13species.The mutation was verified as a de novo mutation in the pedigree,Mutation Taster software analysis indicated that it was suspected to be pathogenic mutation,and it was pathogenic according to the ACMG classification.Conclusion The children with epilepsy accompanied by developmental delay and autism spectrum disorder should consider the CHD2 gene mutation,and genetic test contributes to the early diagnosis.