Pathomechanisms of SCN3A-related neurodevelopmental disorder

项目总结 最近报道的SCN3A相关神经发育障碍(SCN3A-NDD)是由致病因素引起的 编码钠(Na+)通道亚单位Nav1.3的SCN3A基因的变体。SCN3A-NDD是 以难治性癫痫和严重/严重智力残疾(ID)为定义的破坏性状况； 令人惊讶的是，许多患者还表现出皮质发育畸形(MCD)，这是一种发育性 大脑皮层结构形成障碍，提示Nav1.3的功能作用 在胚胎发育过程中。SCN3A基因变异如何导致癫痫和神经发育 残疾以及SCN3A变异是如何导致MCD的，目前尚不清楚。需要研究来澄清其功能作用 在早期大脑发育中的Nav1.3，并向新的治疗或预防措施进展 用于SCN3A-NDD，这是目前无法治疗的疾病。 这个为期5年的协作应用程序使用新的工具和创新的神经科学方法来测试 假设SCN3A致病变异导致一种疾病，包括癫痫和MCD通过 发育中的大脑皮层迁移神经元上的Na+电流失调。 异种细胞系统的电生理记录表明，在异种细胞系统中发现的致病SCN3A变体 SCN3A-NDD患者主要产生Na+通道，由于增加而表现出功能增强 持续电流和通道激活的电压依赖性的变化，这增加了通道 活动。然而，所观察到的癫痫严重程度和有无癫痫的变异性的机制基础 MCD，目前尚不清楚。而改变的通道活动如何影响神经元的功能还没有被研究过。 拟议的实验将确定特定的SCN3A变异与相关临床的关系 大量人类SCN3A-NDD患者的表型(癫痫、MCD、ID的严重程度)。要链接 SCN3A变异到离子通道和神经元的功能障碍，我们将比较它们的生物物理特性 正常Na+通道到含有变异Nav1.3的通道；测试SCN3A变异对细胞的内在影响 从人SCN3A-NDD患者诱导的多能干细胞产生的神经元；以及 小鼠胚胎宫内电穿孔变异型过表达及脑内电记录 切片(目标1)。SCN3A变异对未成熟神经元形态和细胞构筑的影响 发育中的大脑皮层将告知SCN3A在发育中的作用(目标2)。要翻译这些内容 临床应用的研究结果，我们将尝试在高级模型中改进SCN3A-NND的特征 系统，包括新产生的条件性点突变小鼠，通过靶向操作致病 Nav1.3介导的钠电流(Aim 3)。 研究结果将提供有关Nav1.3在大脑发育过程中的作用的新信息，并将定义 SCN3A-NDD的致病机制对人类患者新的靶向治疗的开发。

PROJECT SUMMARY Recently-described SCN3A-related neurodevelopmental disorder (SCN3A-NDD) is caused by pathogenic variants in the gene SCN3A, which encodes the sodium (Na+) channel subunit Nav1.3. SCN3A-NDD is a devastating condition defined by treatment-resistant epilepsy and severe/profound intellectual disability (ID); surprisingly, many patients also exhibit malformation of cortical development (MCD), a developmental disturbance in the structural formation of the cerebral cortex of the brain, suggesting functional roles for Nav1.3 during embryological development. How genetic variants in SCN3A leads to epilepsy and neurodevelopmental disability, and how SCN3A variants lead to MCD, is unknown. Research is required to clarify the functional role of Nav1.3 during early brain development and to progress towards novel therapies or preventative measures for SCN3A-NDD, which is currently and untreatable disorder. This 5-year collaborative application employs novel tools and innovative neuroscience approaches to test the hypothesis that pathogenic variants in SCN3A lead to a disorder that includes epilepsy and MCD via dysregulated Na+ currents in migrating neurons of the developing cerebral cortex. Electrophysiological recordings in heterologous cell systems indicate that pathogenic SCN3A variants found in patients with SCN3A-NDD largely produce Na+ channels that exhibit gain of function due to increased persistent current and alterations in the voltage dependence of channel activation, which increase channel activity. However, the mechanistic basis of observed variability in epilepsy severity and presence or absence of MCD, is unclear. And how altered channel activity impacts the function of neurons has not been investigated. Proposed experiments will determine the relationship between specific SCN3A variants and correlated clinical phenotype (epilepsy, MCD, severity of ID) in a large cohort of human patients with SCN3A-NDD. To link SCN3A variants to dysfunction of ion channels and neurons, we will compare the biophysical properties of normal Na+ channels to channels containing variant Nav1.3; test cell-intrinsic effects of SCN3A variants in neurons generated from induced pluripotent stem cells from human SCN3A-NDD patients; and test effects of variant overexpression via in utero electroporation of mouse embryo followed by electrical recording in brain slices (Aim 1). The impact of variant SCN3A on the morphology of immature neurons and cytoarchitecture of the developing cerebral cortex will inform the role of SCN3A in development (Aim 2). To translate these findings towards clinical applications, we will attempt to ameliorate features of SCN3A-NND in advanced model systems, including a newly generated conditional point mutant mouse, via targeted manipulation of pathogenic Nav1.3-mediated Na+ current (Aim 3). Results will provide novel information on the role of Nav1.3 during brain development, and will define the pathogenic mechanisms of SCN3A-NDD towards development of novel, targeted therapies in human patients.