CASQ2基因c.381C>T突变致儿茶酚胺敏感性多形性室性心动过速的分子机制  

The Molecular Mechanism of c.381C>T Mutation in CASQ2 Gene Induced Catecholaminergic Polymorphic Ventricular Tachycardia

作　　者：李翠兰[1] 袁越[2] 刘文玲[1] 胡大一[1] LI Cuilan;YUAN Yue;LIU Wenling;HU Dayi(Department of Cardiology,Peking University People’s Hospital,Beijing,100044,China)

机构地区：[1]北京大学人民医院急性心肌梗死早期预警和干预北京市重点实验室心血管内科,北京市100044 [2]首都医科大学附属北京儿童医院心内科

出　　处：《中国循环杂志》2021年第7期692-699,共8页Chinese Circulation Journal

基　　金：国家自然科学基金(81170089);教育部博士点基金(20110001110046)。

摘　　要：目的:对心电图上有U波,首诊怀疑长QTU综合征(LQTU)的两个家系进行基因筛查和功能检验,以期找到致病突变并结合临床信息作出疾病诊断。方法:筛查对象是2004~2005年来我院就诊的两个初诊为LQTU的家系L79和L104。诊断依据包括临床特征,如交感神经兴奋相关的晕厥,心电图记录到QT间期(或QU间期)延长及室性心动过速,且无器质性心脏病。记录先证者及其父母和一级亲属的病史、心电图和家族史,包括12导联静息心电图、24 h动态心电图和运动试验等。采用全外显子及Sanger测序法进行基因筛查。对发现的突变利用微小基因(minigene)技术进行功能验证。结果:两个家系中共有3例女性患者,皆为5岁左右首次发生晕厥。儿时心电图上有显著U波,随年龄增加U波幅度降低或消失。校正QT间期正常或临界值。基因筛查发现3例患者携带有CASQ2基因上的c.381C>T(p.Gly127=)纯合突变,父母杂合携带。其中L79家系先证者同时携带KCNQ1/c.921+1G>T杂合突变。Minigene实验证实,CASQ2/c.381C>T(p.Gly127=)突变虽未引起编码氨基酸改变,但其改变了3号外显子后面的生理性剪接位点并在380_381位点引入了一个新的剪切位点,致使其后41个核苷酸缺失,并在第128位置产生提前终止密码子。3例患者服用普萘洛尔或联合使用美西律,近3~15年无晕厥。结论:基因筛查及minigene功能验证结合家系临床表现,可确诊这3例患者为CASQ2/c.381C>T(p.Gly127=)纯合突变引起的儿茶酚胺敏感性多形性室性心动过速(CPVT)2型,L79先证者同时伴有KCNQ1/c.921+1G>T杂合突变所致的长QT综合征1型。本研究在中国CPVT患者中发现CASQ2基因编码区内的核苷酸同义变异可导致剪接突变效应。Objectives:To define the genotype and phenotype in two pedigrees suspected as long QTU syndrome with obvious U wave on ECG.Methods:Gene screening was performed using whole exome sequencing and Sanger sequencing techniques.Functional verification was achieved by minigene assay for the detected mutation.Results:Two pedigrees(L79 and L104),admitted to our hospital from 2004 to 2005 suspected of long QTU syndrome with obvious U wave on ECG,were included in this study.There were 3 patients in two families.They all experienced the first syncope episodes at the age of 5 years.Obvious U wave was observed on the childhood ECG,and the amplitude of U wave decreased or disappeared as age increased.QTc was normal or borderline prolonged.Gene screening found that all three patients carried homozygous CASQ2/c.381C>T(p.Gly127=)mutation,and their parents carried heterozygous mutations.Among them,L79 proband simultaneously carried heterozygous KCNQ1/c.921+1G>T variant.Further minigene study confirmed a deletion of the last 41 nucleotides of exon 3 as a consequence of the creation of the cryptic splice donor site at position c.380_381 and the elimination of the physiological splice site of exon 3.This aberrant splicing would induce premature termination code(PTC)at position 128 in cardiac cells.There was no recurrent syncope in these 3 patients for the last 3 to 15 years under propranolol alone or in combination with mexiletine medication.Conclusions:Based on the results of gene screening and minigene functional verification and in combination with clinical manifestations,these 3 patients could be diagnosed as catecholaminergic polymorphic ventricular tachycardia(CPVT)caused by CASQ2/c.381C>T homozygous mutations.L79 proband also had type 1 long QT syndrome caused by KCNQ1/c.921+1G>T variant.This study also shows that a synonymous mutation c.381C>T(p.Gly127=)located in the coding domain of CASQ2 could result in aberrant splicing in Chinese CPVT patients.

关 键 词：儿茶酚胺敏感性多形性室性心动过速 U波 CASQ2基因 c.381C>T 剪接突变 微小基因功能验证 

分 类 号：R541.4[医药卫生—心血管疾病]