Phamacogenomic studies for the genetic basis for lethal arrhythmias

对正常志愿者（n=120）、先天性长QT综合征（cLQTS, n=30）、获得性长QT综合征（aLQTS, n=4）、无症状Brugada综合征（aBS, n=30）、有症状Brugada综合征（sBS, n=37）、进行性心传导障碍（PCCD, n=2）和心房静止（AS, n=2）的基因组dna进行遗传筛查。我们在cLQTS中发现了一个心脏占有通道基因KCNH2突变。在心脏钠通道基因（SCN5A）中发现了9个不同的突变；cLQTS (2/30), aLQTS (1/4), aBS(1/30)、sBS (5/37), PCCD(1/2),以及(1/2)。利用哺乳动物培养细胞tsA-201，通过定点诱变和异源表达系统检测8个SCN5A突变的生物物理异常。瞬时转染突变Na通道，记录全细胞Na电流。3个负责cLQTS和aLQTS的突变通道显示出持续的Na电流，这是其他LQT3突变通道的特征。5个sBS突变体中2个突变体通道和AS突变体通道没有可见电流。导致aBS的突变是SCN5A的同一外显子上的双突变，并表现出BS的功能丧失特征。我们在SCN5A中发现了两个新的单核苷酸多态性（SNP）。V1951L和L1988R。TaqMan PCR检测的等位基因频率在正常组和Brugada综合征组之间无显著差异。这些snp对氟氯胺的敏感性几乎与野生型Na通道相同，这表明这些snp不太可能是Na通道阻滞剂敏感性差异的基础。在一例aBS病例中发现的双突变是导致aBS的第一个SCN5A突变（Yokoi等）。《心脏节律》（2005）。导致AS的突变是迄今为止报道的第三个SCN5A突变。在这种情况下，我们在连接蛋白40中发现了一个伴随的SNP，现在正在研究这种心律失常的心房特异性发病机制。

Genetic screening was performed in the genomic DNAs from normal volunteers (n=120), congenital long QT syndrome (cLQTS ; n=30), acquired long QT syndrome (aLQTS ; n=4), asymptomatic Brugada syndrome (aBS ; n=30), symptomatic Brugada syndrome (sBS ; n=37), progressive cardiac conduction disturbance (PCCD ; n=2), and atrial standstill (AS ; n=2).We found a cardiac possatium channel gene KCNH2 mutation in cLQTS. Nine distinct mutations were found in cardiac Na channels genes (SCN5A) ; cLQTS(2/30), aLQTS(1/4), aBS(1/30), sBS(5/37), PCCD(1/2), and AS(1/2). Biophysical abnormalities of the eight SCN5A mutations were determined by site-directed mutagenesis and heterologous expression system using mammalian cultured cell tsA-201. Whole cell Na current were recorded by transient transfection of these mutant Na channels. 3 mutant channels responsible for cLQTS and aLQTS showed persistent Na current that is characteristic for other LQT3 mutant channels. 2 mutant channels out of 5 mutation of sBS and the AS mutant channel showed no observable current. The mutation responsible for aBS was a double mutation at the same exon of SCN5A, and showed loss-of function properties characteristic for BS.We have identified two novel single nucleotide polymorphisms (SNP) in SCN5A. V1951L and L1988R. Allele frequencies determined by TaqMan PCR strategies was not significantly difference between normal group and Brugada syndrome group. Flecainide sensitivities of these SNPs were nearly identical to wild type Na channel, suggesting that these SNPs are unlikely to underlie differences in the sensitivities to Na channel blockers.The double mutation identified in an aBS case is the first SCN5A mutation responsible for aBS (Yokoi et al. Heart Rhythm 2005). The mutation responsible for AS was the third SCN5A mutation reported so far. We found a concomitant SNP in the connexin 40 in this case, and now investigating the pathogenesis of atria-specific nature of this arrhythmia.