Ion channelopathies co-expressed in heart and brain

描述(申请人提供)：神经元的兴奋性，从而致痫能力，是由电压和配基门控离子通道的相互作用决定的，离子通道基因的突变现在被认为是独立定义的遗传性癫痫综合征和心律失常的重要原因。最近的证据表明，这些基因的一个子集在心脏和大脑中共同表达。大量的临床和实验证据支持癫痫发作和心律失常并存，许多临床报道认为“致心律失常性癫痫”是癫痫原因不明猝死的病理生理机制。QT间期延长综合征(LQTS)是引起特发性心律失常和心脏性猝死的重要原因之一。已鉴定出7个LQT基因座和6个LQT基因(SCN5A、KvLQT1、HERG、KCNE1、KCNE2、KCNJ2)。突变改变了通道的电生理特性，从而使心脏易于发生致命的心律失常。来自我们实验室的研究数据表明，SCN5A选择性地在心脏和大脑边缘区域共表达，这是一个天生容易发生癫痫的网络。HERG、KCNE2和-KCNJ2基因在脑内均有表达，但尚未被区域定位。本项目将扩展我们确认LQT基因中枢神经系统表达的初步数据，并通过以下方式测试它们与癫痫的关系：1)使用原位杂交技术在哺乳动物脑中定位已知的LQT基因(KvLQT1、KCNE1、HERG、KCNE2和KCNJ2)，以允许与神经表型相关；2)分析癫痫合并心律失常患者的基因组DNA，包括被诊断为SUDEP的患者，以确定这些基因是否存在突变。 我们的假设是，在心脏和大脑中共表达的离子通道基因突变是心律失常和癫痫的临床表型的基础，并可能最终导致(SUDEP)。在这项研究的过程中，我们将扩大特发性癫痫发作患者的临床数据库，并利用它来筛选离子通道病。我们将分析合并心脏病史的癫痫患者的DNA，以及被诊断为SUDEP的患者的DNA。LQT基因将使用聚合酶链式反应、高效液相色谱和直接测序的方法进行研究。这项研究可能有助于确定LQT基因在癫痫和SUDEP的病因中可能发挥的作用。它还可能有助于确定有猝死风险的癫痫人群，这将使受影响的患者能够启动挽救生命的预防措施和设计针对基因的治疗方法。

DESCRIPTION (provided by applicant): Neuronal excitability, and thus epileptogenicity, is critically governed by the interaction of voltage-and ligand-gated ion channels and mutations of ion channel genes are now recognized as an important cause of independently defined inherited epilepsy syndromes and cardiac arrhythmias. Recent evidence indicates that a subset of these genes is co-expressed in heart and brain. There is extensive clinical and experimental evidence supporting coexistence of seizures and cardiac arrhythmias, and many clinical reports suggest that "arrhythmogenic epilepsy" is the pathophysiological mechanism of sudden unexplained death in epilepsy (SUDEP). Long QT syndrome (LQTS) has been increasingly recognized as a cause for idiopathic cardiac arrhythmia and sudden cardiac death. Seven LQT loci and six LQT genes (SCN5A, KvLQT1, HERG, KCNE1, KCNE2, KCNJ2) have been identified. Mutations alter electrophysiological properties of a channel thus predisposing the heart towards fatal arrhythmias. Research data originating from our laboratory demonstrated that SCN5A is selectively co-expressed in heart and the brain limbic region, a network inherently prone towards epileptogenesis. HERG, KCNE2 and-KCNJ2 genes are expressed in brain, however they have not yet been regionally localized. This project will extend our preliminary data confirming CNS expression of LQT genes and test their involvement in epilepsy by 1) localizing the known LQT genes (KvLQT1, KCNE1, HERG, KCNE2 and KCNJ2) in mammalian brain using in situ hybridization to permit correlation with neurological phenotypes, 2) analyzing the genomic DNA of epilepsy patient with cardiac arrhythmias, including cases diagnosed as SUDEP, for the presence of mutations in these genes. It is our hypothesis that mutations in ion channel genes co-expressed in heart and brain underlie the clinical phenotype of cardiac arrhythmias and seizures, and may ultimately lead to (SUDEP). During the course of this study we will expand a clinical database of seizure patients with idiopathic epilepsies and utilize it to screen for ion channelopathies. We will analyze the DNA of epilepsy patients with concurrent cardiac history, and the DNA of cases diagnosed as SUDEP. The LQT genes will be studied using PCR, dHPLC, and direct sequencing methods. This research may help to determine the roles that LQT genes may play in the etiology of seizures and SUDEP. It may also assist in defining an epilepsy population at risk for sudden death, which would allow initiation of life-saving preventative measures and the design of gene-specific therapy for the affected patients.