心脏钠离子通道基因突变与心律失常关系的研究进展

随着基因遗传学和分子生物学技术的发展,发现越来越多的疾病发病与基因突变和遗传因素有关,但具体的作用机制尚未明确,探索基因突变的分子生物学致病机制,利用基因、细胞生物治疗工具,为疾病的靶向治疗开辟了新途径。钠离子通道病是一类与钠离子通道功能障碍相关的疾病,基因突变水平的致病机制在近几年得到深入研究,许多不明原因的致死性心律失常包括Brugada综合征、长QT综合征、孤立型心房颤动、室性心律失常及病态窦房结综合征等均发现与编码心脏钠离子通道的基因突变相关,了解人类心脏钠离子通道基因突变与心律失常关系的研究进展可为心律失常的治疗带来新的靶点。     

Brugada综合征

Brugada综合征是由于编码心室肌离子通道基因突变引起功能异常而导致的综合征。目前认为是编码钠通道 d亚单位 SCN5 A基因发生突变所致 ,通过影响钠通道的功能导致 Brugada综合征。但有的研究指出 :部分 Brugada综合征病人发病与 SCN5 A突变无关 ,提示还存在尚未发现的 Brugada综合征其他的致病基因和 SCN5 A新的突变位点 [1]。1　 Brugada综合征发病机制约 2 0 %～ 2 5 %的 Brugada综合征患者经证实存在 SCN5 A基因突变 ,这些突变均可导致快钠通道电流的减弱。目前从单细胞离子通道到组织多细胞网络基础研究结果发现右心室心外膜…     

心源性猝死相关基因SCN5A的研究进展

SCN5A是钠通道α-亚基的编码基因，近年来的研究表明，SCN5A与长QT间期综合征(long QT syndrome，LQTs)、Brugada综合征(brugada syndrome，BS)以及进行性家族性心脏传导阻滞Ⅰ型(progressive familial heart block，typeⅠ，PFHB Ⅰ)有关。现仅就近年来有关研究进展综述如下。     

Yotiao蛋白在心律失常中的生物学功能研究进展

Yotiao蛋白是A型激酶锚定蛋白(AKAP) 9基因的表达产物,属于AKAP家族成员,是调控缓慢激活延迟整流钾通道(IKs)亚基磷酸化功能的重要蛋白之一。随着基因分子生物学和全外显子测序技术的发展,越来越多的心律失常被证实与基因和遗传因素有关。许多严重的心律失常(心房颤动、长QT综合征、Brugada综合征等)均与编码心脏钾离子通道的基因突变相关。Yotiao蛋白直接与心脏组织的IKs通道KCNQ1亚基结合,并通过招募蛋白激酶A、磷脂酶1、腺苷酸环化酶等重要蛋白激酶形成大分子传导复合体,特异性地调节细胞底物磷酸化过程中的各种信号转导通路。     

在心脏传导障碍伴长QT综合征家系中发现心脏钠离子通道基因SCN5A R1193Q

目的研究心脏传导障碍伴长QT综合征家系中心脏钠离子通道基因(SCN5A)的突变或多态位点。方法该家系有成员19名,进行病史询问、体格检查及做12导联心电图,采集静脉血标本,抽提基因组DNA,聚合酶链反应扩增SCN5A编码区及相邻内含子序列,直接测序寻找基因突变位点。发现突变位点后对所有家系成员的该位点进行测序分析,同时筛查281名无血缘关系的正常人作为对照。结果通过对该家系SCN5A基因的筛查,在其中发现1个位于Exon20的多态性位点(G→A)。碱基的变异造成编码氨基酸的改变,在1 193位置精氨酸由谷胺酰胺代替(R1193Q)。家系中有5例确诊为房室传导阻滞(AVB),至少2例同时存在长Q／c;另有1例虽无AVB,但QTc临界;5例AVB患者中4例携带R1193Q;3名QTc延长或临界的成员均携带R1193Q。281名正常对照者中36名亦存在SCN5A R1193Q,携带率为12．8％。结论SCN5A R1193Q与心脏传导障碍伴长QT综合征存在相关性,这个多态在中国人群的分布约为12．8％,显著高于白种人和日本人(0．2％-2．0％)。     

QT间期与遗传性心律失常综合征研究概况

遗传性心律失常综合征是伴有恶性室性心律失常和猝死而心脏结构正常的一组基因遗传性疾病[1]。包括QT间期异常的长QT间期综合征和短QT间期综合征,现分别对其基因遗传学基础及诊断标准和防治作一综述。一、长QT间期综合征1.发生机制QT间期改变主要与心室的复极化有关。长QT间期综合征(LQTS)是由于心室动作电位的复极时间延长导致心室的易损期延长,从而诱发各种室性心律失常(其中最为凶险的是尖端扭转型室速),在临床上多表现为晕厥和猝死的一组疾病,分先天性和后天性。先天性LQTS是一种遗传性离子通道疾病,是由于编码跨膜钠离子或钾离…     

相同SCN5A基因突变而不同临床表现型两家系报道

目的SCN5A基因突变与各种原因导致的心脏猝死有关,具有各种临床表现的重叠。方法初始诊断为Brugada综合征的两个家系,采用DNA直接测序法,对两家系成员使用候选基因法,对SCN5A行突变检测。结果两个家系成员均分别有各种心电图异常,包括Brugada型心电图表现,长QT间期,窦性心动过缓,右束支、左前半阻滞和完全性房室传导阻滞。两个家系均有重要的心脏猝死史。DNA直接测序发现两个家系分别有两个不同的SCN5A基因突变:一家系是在核苷酸1784位点,由G代替了A的基因突变(A1784G);另一家系在SCN5A片段II插入TG的基因突变(Tgins851)。结论相同基因型和不同表现型的离子通道疾病在一个家系中共存。ICD治疗是目前Brugada综合征的惟一有效治疗,从而提出基因携带而无症状者是否需要临床治疗。     

遗传性心律失常治疗新视野

Brugada综合征Brugada综合征主要表现为右束支传导阻滞与右胸导联ST段抬高,常发生室性心动过速（VT）或心室颤动而导致晕厥与猝死.其心电图无QT延长,与尖端扭转性室速（TdP）发作前长-短序列不同,很少发作前有此现象.其与儿茶酚胺依赖性多形性VT不同,发作前无心率加速现象.2相折返被认为是Brugada综合征发生室性心律失常的机制.Brugada综合征发病主要与SCN5A突变有关.此外,还有钠通道β-亚基突变（SCN1B和SCN3B）,钾通道KCNE3突变,L-型钙通道的α-亚基和β-亚基（CACNA1C和CACNB2B）突变.另外,GPD1L突变产生异常转运蛋白,可抑制细胞膜上钠离子通道的正常表达.     

Brugada综合征致病关联基因突变研究进展

Brugada综合征是一种遗传性心脏病,目前已发现10种导致Brugada综合征的致病基因,分为编码钠离子通道、钙离子通道和钾离子通道蛋白的基因.编码钠离子通道的基因有SCN5A基因、GPD1L基因、SCN1B基因、SCN3B基因;编码钙离子通道的基因有CACNA1C基因、CACNB2基因、CACNA2D1基因;编码钾...     

中国人遗传性长QT综合征KCNQ1和KCNH2基因新突变

目的:遗传性长QT综合征(LQTS)是一种常染色体遗传性心脏病.特征性表现为心电图上QTc延长及尖端扭转性室性心动过速(TdP)导致的晕厥和猝死.近年来随着分子遗传学的发展已明确遗传性LQTS是由于编码离子通道的基因突变造成的,包括编码钠离子通道的基因SCN5A和编码钾离子通道亚单位的基因KCNQ1, KCNH2, KCNE1, KCNE2,和 KCNJ2.目前,中国人LQTS基因突变的报道较少,本研究目的是找到中国LQTS基因突变.方法:应用聚合酶链反应和测序分析,对来自中国14个省、市、自治区的31个遗传性LQTS家系筛查了最常见的2个LQTS致病基因KCNQ1 和 KCNH2.结果:发现了2个KCNQ1 新突变:S5跨膜片段的S277L 和孔区的G306V ;3个KCNH2 新突变:跨膜片段S1的L413P、跨膜片段S5的L559H和发生于跨膜片段S3的L520V.KCNH2 L413P 和L559H突变患者的ECG T波为双峰;KCNQ1 S277L和G306V 突变患者的ECG T 波高尖.结论:本研究发现的突变点丰富了LQTS离子通道突变的基因库资料.本研究的中国LQTS患者的突变率KCNQ1 (6.5%) 和KCNH2 (10%)低于北美和欧洲患者.     

Postmortem molecular analysis of SCN5A defects in sudden infant death syndrome.

CONTEXT: Fatal arrhythmias from occult long QT syndrome may be responsible for some cases of sudden infant death syndrome (SIDS). Because patients who have long QT syndrome with sodium channel gene (SCN5A) defects have an increased frequency of cardiac events during sleep, and a recent case is reported of a sporadic SCN5A mutation in an infant with near SIDS, SCN5A has emerged as the leading candidate ion channel gene for SIDS. OBJECTIVE: To determine the prevalence and functional properties of SCN5A mutations in SIDS. DESIGN, SETTING, AND SUBJECTS: Postmortem molecular analysis of 93 cases of SIDS or undetermined infant death identified by the Medical Examiner's Office of the Arkansas State Crime Laboratory between September 1997 and August 1999. Genomic DNA was extracted from frozen myocardium and subjected to SCN5A mutational analyses. Missense mutations were incorporated into the human heart sodium channel alpha subunit by mutagenesis, transiently transfected into human embryonic kidney cells, and characterized electrophysiologically. MAIN OUTCOME MEASURES: Molecular and functional characterization of SCN5A defects. RESULTS: Two of the 93 cases of SIDS possessed SCN5A mutations: a 6-week-old white male with an A997S missense mutation in exon 17 and a 1-month old white male with an R1826H mutation in exon 28. These 2 distinct mutations occurred in highly conserved regions of the sodium channel and were absent in 400 control patients (800 alleles). Functionally, the A997S and R1826H mutant channels expressed a sodium current characterized by slower decay and a 2- to 3-fold increase in late sodium current. CONCLUSION: Approximately 2% of this prospective, population-based cohort of SIDS cases had an identifiable SCN5A channel defect, suggesting that mutations in cardiac ion channels may provide a lethal arrhythmogenic substrate in some infants at risk for SIDS.     

先天性长QT综合征和Brugada综合征基因突变

目的研究先天性长QT综合征(LQTS,包括JLNS和RWS)和Brugada综合征(BS)家系的基因突变情况.方法采用聚合酶链反应(PCR)和直接测序法,对4个LQTS家系进行KCNQ 1、KCNH2和KCNE1基因检测,对3个BS家系进行SCN5A基因检测.结果在1个LQTS家系中发现1个KCNQ1基因上错义突变940(G→A)(G314S),在Jervell-Longe-Nielsen综合征(JLNS)家系的先证者及其姐姐KCNQ1基因的第15外显子发现单核苷酸多态性(SNPs)G643S,还发现1个突变:KCNQ1基因外显子2a的第227位核苷酸C被T代替,其编码的苏氨酸被异亮氨酸所代替.在1个BS家系中发现1个SCN5A基因上的突变N1774S.其余的LQTS家系及BS家系在以上已知基因中均未发现突变.结论发现和JLNS有关的1个SNPs和1个新突变,并发现1个与欧美人群相同的Romano-Ward综合征相关突变,在BS家系中发现1个新的错义突变,丰富了LQTS及BS离子通道突变的基因库资料.     

QT间期延长与肝移植术后近期心律失常的关系

目的总结和探讨肝移植术前心电图提示QT间期延长与肝移植术后近期各类心律失常的关系。方法回顾性分析北京佑安医院2004年6月～2012年1月500例肝移植患者术前心电图的QT间期与术后近期（术后2周内）各种心律失常的发生率及其诊治资料。结果在500例肝移植患者中有82例（16.4％）发生各类心律失常,其中,病态窦房结综合征（包括持续而显著的窦性心动过缓）35例（7．0％）,阵发性室上性心动过速18例（3．6％）,心房颤动21例（4．2％）,室性心动过速8例（1．6％,包括2例尖端扭转性室性心动过速）;82例心律失常患者中心脏骤停4例（0．8％）,由心律失常引起的死亡2例（0．4％）。根据术前心电图检查结果,将患者分为QT间期延长组共103例,QT间期正常组共397例,其中,QT间期延长组中有28例患者发生心律失常,QT间期正常组中有54例患者发生心律失常,肝移植术后近期心律失常的发生与QT间期延长有明显关系（x^2=11．00,P〈0．01）。结论心律失常是肝移植术后常见的并发症．甚至可导致死亡。术前心电图QT间期延长与肝移植术后近期心律失常的发生有明显关系。因此,对于术前QT间期延长的患者应加强监测和评估,并给予预防性措施,如安置临时心脏起搏器,以防止术中及术后心血管意外的发生。     

Single nucleotide polymorphisms of the SCN5A gene in Han Chinese and their relation with Brugada syndrome

Background Mutations in the cardiac sodium channel gene (SCN5A) may lead to a broad spectrum of familial arrhythmias, including long QT syndrome (LQTS), idiopathic ventricular fibrillation (IVF), and isolated cardiac conduction diseases. Recent studies have shown that polymorphisms in the SCN5A gene also play an important role in the manifestation of disorders involving cardiac excitability. In this study, we investigated the polymorphisms of the SCN5A gene in Han Chinese and its relation to Brugada syndrome (BS).Methods Genomic DNA was isolated from 120 unrelated healthy volunteers and 48 unrelated Brugada syndrome patients by means of standard procedures. All exons including the putative splicing sites of the SCN5A gene were amplified by PCR and sequenced directly or after subcloning using an ABI Prism 377 DNA sequencer. Results A total of 5 single nucleotide polymorphisms (SNPs) were identified in the Han Chinese population, including 3 novel ones: G87A(A29A), 4245＋82A>G, and G6174A. The allele frequencies of each SNP in the Han Chinese population were as follows: G87A (A29A) 27.5%, A1673G (H558R) 10.4%, 4245+82A>G 32.8%, C5457T (D1819D) 41.3%, and G6174A 44.9%. S1102Y and 10 other SNPs identified in other ethnic populations were not detected in this study. There was no significant difference in the allele frequency of A1673G (H558R) between different ethnic populations (all P>0.5). On the other hand, the allele frequency of C5457T (D1819D) among Han Chinese was similar to its frequency among Japanese (P>0.5), but higher than that among Americans (P<0.005). The allele G1673 (R558) was over-represented in BS patients compared to controls (P<0.005), but there was no significant difference in genotype frequencies at this locus. There were also no differences in either the allele or genotype frequencies of the 4 other identified SNPs when comparing BS patients with healthy controls. Conclusions The distribution of SCN5A SNPs may vary between different ethnicities. The polymorphism of A1673G might be associated with BS and may contribute to a susceptibility to BS in Han Chinese.     

Malignant familial long QT syndrome

We report a family with congenital long QT syndrome, an inherited disorder of myocardial repolarization in which affected individuals have prolongation of corrected QT interval on the electrocardiogram and a tendency to develop ventricular arrhythmia, leading to syncope, convulsion or sudden death. Our family is characterized by several affected members (11/16), early onset of symptoms, malignant course prior to diagnosis and good response to beta-blocker therapy. The genetic basis of long QT syndrome has been traced to defective proteins encoding cardiac ion channels. Diagnosis is based on an unexplained prolongation of QT interval >0.45 second in the presence of suggestive symptoms or evidence, or both of a familial pattern. Beta-adrenergic blocker therapy gives symptomatic relief in 80%-85% of patients. Precipitating factors like vigorous exercise especially swimming and exposure to significant emotional or auditory stimuli should be avoided. Occasional patients require in addition, a demand cardiac pacemaker, left cardiac sympathectomy or an implantable cardioverter-defibrillator, or both. Regular follow up is mandatory even after subsidence of symptoms.     

Short QT syndrome

The QT interval on an electrocardiogram signifies the time required for the heart to repolarize after depolarization. It has long been appreciated that a long QT interval predisposes patients to life-threatening ventricular arrhythmia. Short QT syndrome is a newly described disease characterized by a shortened QT interval and by episodes of syncope, paroxysmal atrial fibrillation or life-threatening cardiac arrhythmias. The syndrome usually affects young and healthy people with no structural heart disease and may be present in sporadic cases as well as in families. Our understanding of a new disease has rarely benefitted so quickly from research in genetics, molecular biology and biophysics. It was first described in 2000 in a handful of patients, and since then 3 different genes associated with the disease and the biophysical basis have been described, and therapy has been made available. Here we review the current understanding of the pathophysiology, clinical presentation and treatment of short QT syndrome.     

中国人Brugada综合征SCN5A基因突变K317N的定点诱变及其载体构建

目的 对我们发现的中国人Brugada综合征新的SCN5A基因突变K317N进行体外定点诱变研究，并构建携带有基因突变K317N的pRc／CMV-hH1的表达载体。方法 采用PCR定点突变技术，根据突变位置附近的两个单一限制性内切酶位点AgeI／Sse83871设计一对定点诱变引物，将突变位点设计在引物上，通过PCR扩增，使扩增片段上含有所需要的突变位点，最后将扩增片段克隆人pRc／CMV-hH1载体中。结果 DNA测序表明，在预期位点巳经发生突变，SCN5A基因在第317密码子由赖氨酸(K)突变为天冬氨酸(N)，成功实现定点诱变。结论 PCR技术诱导定点突变，准确、高效。pRc／CMV-hH1(K31714)的成功构建，为进一步进行该突变的结构与功能研究奠定了基础。     

全细胞膜片钳技术在遗传性长QT综合征和不明原因猝死中的研究进展

基因突变导致的心脏离子通道疾病被认为是引起不明原因猝死的首要死因,长QT综合征作为最常见的心脏离子通道疾病之一,其致病基因突变在各类SUD中被不断报道。利用全细胞膜片钳技术进行心脏离子通道功能验证对于评估基因突变的致病性、明确SUD死者的死亡原因、筛查SUD危险人群具有重要的法医学意义。对全细胞膜片钳技术的基本原理及其在长QT综合征的发病机制与不明原因猝死研究中的应用进行综述。     

克山病患者SCN5A基因突变的研究

目的通过观察正常人和克山病患者心脏Na 通道基因SCN5A第28外显子的结构,探讨SCN5A基因突变与克山病发病的分子生物学机制。方法提取正常人和克山病患者的DNA,通过聚合酶链反应(PCR)对正常人和克山病患者的DNA进行扩增,并采用PCR-SSCP法检测克山病患者SCN5A基因28外显子的碱基序列。结果通过PCR-SSCP方法在克山病患者的SCN5A基因28号外显子处发现与正常人不同的单链条带,即克山病患者的28号外显子存在突变。结论克山病患者心肌Na 通道基因SCN5A的结构与正常人存在差异,SCN5A基因突变可能是导致克山病患者对环境因素易感性增加的因素之一。