The Genetic Basis of Novel Loci Influencing Myocardial Repolarization

描述(由申请人提供)：项目摘要心脏复极在心肌细胞中被评估为动作电位(AP)持续时间，在心电图上被评估为QT间期，需要多个离子通道及其附属蛋白的严格调控功能。在过去的十年中，复极的扰动直接与药物引起的心律失常和心源性猝死(SCD)的发生有关。虽然QT间期是心律失常和猝死的预测指标，但很明显，QT间期延长本身不足以导致这样的灾难性事件；通常需要额外的环境侮辱。有几个可识别的触发因素，包括心肌缺血、电解质失衡(特别是低钾血症)和儿茶酚胺状态升高，但可能对心脏复极的最大环境挑战来自于处方药的形式。在过去的十年里，已经上市的药物退出或限制的最常见原因是不受欢迎的QT延长。虽然QT间期是一种可遗传的数量性状，但影响QT间期的基因以及对延长QT的药物的反应仍不清楚。长期以来，人们一直认为常见的变异在这种复杂的特征中扮演着重要的角色，通过最近的全基因组关联研究，现在有几个新的基因座与QT间期相关。除了识别新基因座的能力外，全基因组关联研究也有局限性：它们不能区分给定基因座上的哪个基因是因果关系，也不能揭示机械的洞察力。随着我们开始揭开环球航空研究的发现，第一步将是确定每个相关基因座的功能基因(S)。我们建议使用一个易于处理的斑马鱼模型，该模型忠实地概括了人类心肌复极的关键特征。使用一种允许将人类基因发现转化为易于处理的相关模型的方法，我们将检验这样一个假设，即斑马鱼的基因敲除将确认五个新的人类复极基因座中的每一个的候选基因。一旦识别出新的复极化基因，我们将在我们的模型中对它们进行基因x药物相互作用测试。我们提出了以下具体目标：目的1：在斑马鱼心脏复极模型中，验证最近发现的五个新遗传位点的候选心肌复极基因。这将涉及到有针对性地敲除这五个基因座的基因，并使用光学电压标测来确定对心肌复极的影响。目的2：定量鉴定心肌复极过程中基因与药物的相互作用。临床上对心肌复极最重要的环境暴露是延长QT的药物。所有25个候选复极基因将在基因x药物实验中与延长QT的药物进行相互作用测试。 公共卫生相关性：心电图上的QT间期是心律问题和猝死的预测指标，但控制这一过程的基因在很大程度上仍不清楚。最近，大规模的基于人群的研究缩小了对这些基因的搜索范围，确定了这些基因所在的五个遗传社区。我们建议使用斑马鱼模型系统地敲除这些社区的基因，并测量其对相当于QT间期的影响；我们希望最终确定改变QT间期的基因，并实现对心率问题和猝死的更好理解。

DESCRIPTION (provided by applicant): Project Summary Cardiac repolarization, assessed in myocytes as action potential (AP) duration and on the electrocardiogram as the QT interval, requires the tightly regulated function of multiple ion channels and their accessory proteins. In the last decade, perturbations of repolarization have been directly implicated in the genesis of drug-induced arrhythmias and sudden cardiac death (SCD). While QT interval is a predictor of arrhythmias and sudden death, it is clear that a prolonged QT interval by itself is insufficient to cause such catastrophic events; additional environmental insults are usually required. There are several identified triggers including, myocardial ischemia, electrolyte imbalances (especially hypokalemia), and elevated catecholamine states, but perhaps the greatest environmental challenge to cardiac repolarization comes in the form of prescribed drugs. In the past decade, the single most common cause of the withdrawal or restriction of drugs that have already been marketed has been undesired QT prolongation. While the QT interval is a heritable quantitative trait, the genes that influence the QT interval as well as the response to QT prolonging drugs remain unknown. Common variants have long been thought to play a significant role in this complex trait and there are now several novel loci associated with QT interval through recent genome-wide association studies. Along with the power to identify novel loci, genome wide association studies do have limitations: they cannot distinguish which gene at a given locus is causal, nor do they reveal mechanistic insights. As we begin to unravel the discoveries of GWA studies, the first step will be to identify the functional gene(s) at each associated locus. We propose the use of a tractable zebrafish model that faithfully recapitulates key features of human myocardial repolarization. Using an approach that allows translation of human genetic discoveries into a tractable relevant model, we will test the hypothesis that gene knockdown in zebrafish will confirm candidate genes for each of five novel human repolarization loci. Once novel repolarization genes are identified, they will be tested for gene x drug interactions in our model. We propose the following specific aims: Aim 1: Validate candidate myocardial repolarization genes from five recently discovered novel genetic loci in a zebrafish model of cardiac repolarization. This will involve targeted knockdown of genes from these five loci and determination of effects on myocardial repolarization using optical voltage mapping. Aim 2: Quantitatively identify gene x drug interactions in myocardial repolarization. The most clinically important environmental exposures to myocardial repolarization are QT prolonging drugs. All 25 candidate repolarization genes will be tested for interactions in gene x drug experiments with QT prolonging drugs. PUBLIC HEALTH RELEVANCE: The QT interval on the electrocardiogram is a predictor of cardiac rhythm problems and sudden death, but the genes that govern this process remain largely unknown. Recently, large population-based studies have narrowed the search for these genes, identifying five genetic neighborhoods where these genes lie. We propose to use a zebrafish model to systematically knockdown the genes in these neighborhoods and measure the impact on the equivalent of the QT interval; we hope to conclusively identify the genes that modify the QT interval and achieve a better understanding of heart rhythm problems and sudden death.