Complex genetic interactions in mouse model of sudden death in epilepsy (SUDEP)

描述（由申请人提供）：这项工作的总体目标是研究癫痫猝死（SUDEP）背景下Kcna1和Scn2a离子通道基因突变之间的基因相互作用。癫痫患者因未知病理原因突然死亡的可能性是一般人群的24倍；这些死亡被归类为猝死症，是癫痫相关死亡的主要原因。有几个基因与SUDEP有关，但其遗传病因在很大程度上是未知的，可能涉及多个易感基因变异的共同遗传。本研究旨在研究亚临床Scn2a-null杂合性在Kcna1敲除小鼠SUDEP模型中作为癫痫和过早死亡的保护性遗传修饰因子的能力。Scn2a是一种人类癫痫基因，编码Nav1.2电压门控钠通道α亚基，但尚未发现这里使用的敲除突变会导致癫痫。Kcna1也是一种人类癫痫基因，它编码Kv1.1电压门控钾通道α亚基，这种亚基通常起到抑制神经元兴奋性的作用。Kcna1基因敲除小鼠通过表现出严重癫痫、脑驱动性心功能障碍和过早死亡来准确地模拟人类SUDEP。考虑到这两个基因的表达重叠和相互对立的兴奋性作用，本研究提出了一个假设，即亚临床Scn2a-null杂合性通过抑制与Kv1.1通道缺失相关的神经心脏功能障碍和神经元高兴奋性来降低Kcna1-null小鼠的SUDEP发病率。初步数据显示，Scn2a-null杂合性可阻止Kcna1基因敲除的SUDEP，使其存活增加三倍。在Aim 1中，视频脑电图-心电图（EEG-ECG）用于确定Scn2a-null杂合性是否会减少Kcna1-null小鼠的癫痫样放电和/或心脏异常。Aim 2旨在通过分析与异常神经元激活相关的分子生物标志物（如c-Fos）的表达变化，识别Scn2a和Kcna1之间表现出功能相互作用的神经网络。本研究利用一种新的基因小鼠模型作为了解SUDEP背后复杂的遗传相互作用的重要第一步，最终目标是改善基于基因型的癫痫风险预测、预防和治疗。scn2a -零杂合性抑制Kcna1 SUDEP表型的能力将证明，在评估癫痫患者的遗传风险谱时，即使没有明显表型的亚临床基因变异也必须考虑，因为这些等位基因也可能是疾病易感性的关键修饰因子。此外，在这种基因模型中检查分子生物标志物的内表型有可能识别出以前未被识别的大脑网络，这些网络对SUDEP的病理生理和未来研究的候选治疗靶点很重要。

DESCRIPTION (provided by applicant): The overall goal of this work is to examine digenic interactions between mutations in the Kcna1 and Scn2a ion channel genes in the context of sudden unexpected death in epilepsy (SUDEP). People with epilepsy are 24 times more likely than the general population to die suddenly for unknown pathological reasons; these deaths are classified as SUDEP and represent the leading cause of epilepsy-related mortality. Several genes have been linked anecdotally to SUDEP, but its genetic etiology is largely unknown and likely complex involving the co-inheritance of multiple susceptibility gene variants. This proposal investigates the ability of subclinical Scn2a-null heterozygosity to act as a protective genetic modifier of epilepsy and premature death in the Kcna1 knockout mouse model of SUDEP. Scn2a, a human epilepsy gene, encodes Nav1.2 voltage-gated sodium channel Alpha-subunits but the knockout mutation utilized here has not been found to cause epilepsy. Kcna1, also a human epilepsy gene, encodes Kv1.1 voltage-gated potassium channel Alpha-subunits that normally act to dampen neuronal excitability. Kcna1 knockout mice accurately model human SUDEP by exhibiting severe epilepsy, brain-driven cardiac dysfunction, and premature death. Given the expression overlap and mutually opposing excitability effects of the two genes, the proposed research tests the hypothesis that subclinical Scn2a-null heterozygosity reduces SUDEP incidence in Kcna1-null mice by suppressing neurocardiac dysfunction and neuronal hyperexcitability associated with the absence of Kv1.1 channels. Preliminary data shows that Scn2a-null heterozygosity prevents SUDEP in Kcna1 knockouts increasing their survival threefold. In Aim 1, video electroencephalography-electrocardiography (EEG-ECG) is used to determine whether Scn2a-null heterozygosity reduces epileptiform discharges and/or cardiac abnormalities in Kcna1-null mice. Aim 2 seeks to identify neuronal networks exhibiting functional interaction between Scn2a and Kcna1 by analyzing changes in expression of molecular biomarkers associated with abnormal neuronal activation, such as c-Fos. This research utilizes a novel digenic mouse model as an important first step towards understanding the complex genetic interactions underlying SUDEP with the ultimate goal of improving genotype-based risk prediction, prevention, and therapy in epilepsy. The ability of Scn2a-null heterozygosity to suppress the Kcna1 SUDEP phenotype would demonstrate a proof-of-principle that even subclinical gene variants without obvious phenotypes must be considered when evaluating the genetic risk profiles of epilepsy patients since those alleles can also be critical modifiers of disease susceptibility. Furthermore, the examination of molecular biomarker endophenotypes in this digenic model has the potential to identify previously unrecognized brain networks that are important for SUDEP pathophysiology and candidate therapeutic targets for future studies.