Understanding the role of sodium channels in epilepsy

描述(由申请人提供)： 项目摘要SCN1A电压门控钠通道(VGSC)突变导致越来越多的疾病，包括遗传性癫痫伴发热性惊厥(GEFS+)、Drave氏综合征(DS，或婴儿时期的严重肌阵挛癫痫)和家族性偏瘫偏头痛。为了更好地了解SCN1A功能障碍导致癫痫的机制，我们产生了带有人类SCN1A突变R1648H的转基因和敲入小鼠。这些突变体表现出自发癫痫发作，癫痫发作阈值降低，寿命缩短。皮层神经元的电生理分析显示，兴奋性神经元和抑制性神经元的功能都降低了，但其生物物理机制不同-兴奋性神经元快速失活的电压负移依赖于抑制性神经元失活的缓慢恢复。我们的结果和来自其他小组的数据导致了这样的假设，即减少GABA能抑制在GEFS+和DS的发病机制中起主要作用。然而，SCN1A在中间神经元或锥体细胞中的功能与癫痫的发生之间的直接因果联系尚未建立。在目标1中，我们将选择性地从中间神经元或锥体细胞中删除Scn1a，以直接确定每种细胞类型对癫痫发生的相对贡献。在目标2中，我们将测试早期热性惊厥(FSS)这一假说，这是GEFS+和DS的一个显著的临床特征，对疾病进展有影响。我们还将探索FSS和疾病结局之间关系的机制基础和可能的药物干预。与我们找到更好的癫痫治疗方法的最终目标进一步相关的是，我们观察到，Scn8a VGSC功能的改变可以恢复正常的癫痫发作阈值和寿命，使其恢复到Scn1a基因敲除的DS模型。这一观察结果使我们假设选择性靶向SCN8A可能成为治疗DS的有效方法，DS通常对现有药物无效。在目标3中，我们将研究改变Scn8a功能是否也可以改善其他遗传形式的癫痫和癫痫类型。本研究将为VGSCs在维持正常神经元兴奋性和癫痫发生发展中的作用提供重要信息。这些实验具有创新性、临床相关性，并将刺激急需的转化性研究。

DESCRIPTION (provided by applicant): PROJECT SUMMARY Mutations in the SCN1A voltage-gated sodium channel (VGSC) are responsible for a growing number of disorders, including genetic epilepsy with febrile seizures plus (GEFS+), Dravet syndrome (DS, or severe myoclonic epilepsy of infancy), and familial hemiplegic migraine. To better understand the mechanism by which SCN1A dysfunction leads to epilepsy, we generated transgenic and knock-in mice with the human SCN1A mutation R1648H. These mutants exhibit spontaneous seizures, reduced seizure thresholds, and shortened life spans. Electrophysiological analysis of cortical neurons revealed reduced function in both excitatory and inhibitory neurons, but the biophysical mechanisms were different - negatively shifted voltage dependence of fast inactivation in excitatory neurons versus slowed recovery from inactivation in inhibitory neurons. Our results and data from other groups led to the hypothesis that reduced GABAergic inhibition plays the major role in the pathogenesis of GEFS+ and DS. However, a direct causal link between SCN1A function in interneurons or pyramidal cells and seizure generation has not yet been established. In Aim 1, we will selectively delete Scn1a from either interneurons or pyramidal cells to directly establish the relative contribution of each cell type to seizure generation. In Aim 2, we will test the hypothesis that early-life febrile seizures (FSs), which are a prominent clinical feature of both GEFS+ and DS, have an impact on disease progression. We will also explore the mechanistic basis for the relationship between FSs and disease outcome and possible pharmacological interventions. Of further relevance to our ultimate goal of finding better treatments for epilepsy is our observation that altered function of the Scn8a VGSC can restore normal seizure thresholds and life spans to an Scn1a knockout model of DS. This observation led us to hypothesize that selective targeting of SCN8A may make an effective treatment for DS, which is often refractory to available medications. In Aim 3 we will investigate whether altering Scn8a function can also ameliorate other genetic forms of epilepsy and types of seizures. This study will provide important information on the role of VGSCs in the maintenance of normal neuronal excitability and in the development of epilepsy. These experiments are innovative, clinically relevant, and will stimulate much-needed translational research.