Cell Type-Specific Roles of the Na-Activated K Current in KCNT1-Related Epilepsy

编码Na+激活K+通道的KCNT1基因的变异体， 儿童癫痫病，很大程度上是难以治疗的。此前， 当在非神经元细胞中测定时，显示KCNT1变体增加通道电流， 这就引出了一个基本问题，即如何增加通常与 抑制神经元的兴奋性会导致以过度、同步性为特征的疾病 神经元活动我们建立了两个小鼠模型， KCNT1变异体经常发作。在这两种模型中，皮质抑制性神经元（cIN） 显示膜兴奋性和动作电位产生的强烈损害，而 兴奋性神经元（cENs）则没有。这些数据表明，KCNT1功能获得性（GOF） 变异通过损害cINs的功能引起儿童癫痫，KCNT1通道 在调节神经元兴奋性中发挥细胞类型特异性作用。这份提案将检验这些 通过（1）确定KCNT1阻断和GOF如何影响cIN膜兴奋性 亚型，（2）使用新开发的KCNT1选择性抑制剂来测量电流， 它是如何被cIN亚型中的致病变异体改变的，以及（3）测试它是如何受损的。 cINs亚群的膜兴奋性影响其体内活性，以及这是如何相关的 癫痫发作或皮质兴奋过度确定这些脆弱的细胞类型， 机制，以及其功能障碍的体内效应将使我们能够将细胞缺陷与 癫痫样活动和癫痫发作。研究结果将促进我们对该法规的理解 cIN兴奋性，KCNT1介导电流的生理作用，以及疾病 在癫痫的体内模型中KCNT1 GOF的机制。这将缩小知识差距 离子通道变异体的生物物理效应与由此产生的 网络，并有可能改善严重的精确治疗的靶向 儿童癫痫

Variants in the KCNT1 gene, which encodes a Na+-activated K+ channel, cause several severe childhood epilepsy disorders that are largely refractory to treatment. Previously, pathogenic KCNT1 variants were shown to increase channel current when assayed in non-neuronal cells, leading to the fundamental question of how increasing a current that is usually associated with dampening neuronal excitability leads to disorders characterized by excessive, synchronous neuronal activity. We have created two mouse models with orthologous pathogenic human KCNT1 variants that have frequent seizures. In both models, cortical inhibitory neurons (cINs) show strong impairments in membrane excitability and action potential generation, whereas excitatory neurons (cENs) do not. These data suggest that KCNT1 gain-of-function (GOF) variants cause childhood epilepsy by impairing the function of cINs, and that KCNT1 channels play cell-type-specific roles in regulating neuronal excitability. This proposal will test these hypotheses by (1) determining how KCNT1 block and GOF affect membrane excitability of cIN subtypes, (2) using newly-developed KCNT1-selective inhibitors to measure the current and how it is altered by disease-causing variants in cIN subtypes, and (3) testing how impaired membrane excitability in subpopulations of cINs affects their activity in vivo, and how this relates to seizures or cortical hyperexcitability. Determining these vulnerable cell types, the underlying mechanisms, and the in vivo effects of their dysfunction will allow us to relate cellular deficits to epileptiform activity and seizures. The results will advance our understanding of the regulation of cIN excitability, the physiological roles of the KCNT1-mediated current, and the disease mechanisms of KCNT1 GOF in an in vivo model of epilepsy. This will narrow the knowledge gap between the biophysical effects of ion channel variants and the resulting dysfunction of networks, and has the potential to improve the targeting of precision therapies for severe childhood epilepsies.