Li Lin, Liu Zili, Yang Haiyang, Li Yang, Zeng Qi, Chen Li, Liu Yidi, Chen Yan, Zhu Fengjun, Cao Dezhi, Hu Jun, Shen Xuefeng
Surgery Division, Epilepsy Center, Shenzhen Children's Hospital, Shenzhen, Guangdong 518038, China.
The Brain Cognition and Brain Disease Institute (BCBDI), Shenzhen Institute of Advanced Technology (SIAT), Chinese Academy of Sciences (CAS), Shenzhen-Hong Kong Institute of Brain Science-Shenzhen Fundamental Research Institutions, Shenzhen, Guangdong 518055, China.
Seizure. 2022 Oct;101:218-224. doi: 10.1016/j.seizure.2022.09.004. Epub 2022 Sep 5.
Purpose The voltage-gated potassium channel K3.2, encoded by KCNC2, facilitates fast-spiking GABAergic interneurons to fire action potentials at high frequencies. It is pivotal to maintaining excitation/inhibition balance in mammalian brains. This study identified two novel de novo KCNC2 variants, p.Pro470Ser (P470S) and p.Phe382Leu (F382L), in patients with early onset developmental and epileptic encephalopathy (DEE). Methods To examine the molecular basis of DEE, we studied the functional characteristics of variant channels using patch-clamp techniques and computational modeling. Results Whole-cell patch clamp recordings from infected HEK293 cells revealed that channel activation and deactivation kinetics strongly decreased in both K3.2 P470S and F382L variant channels. This decrease also occurred in K3.2 p.Val471Leu (V471L) channels, known to be associated with DEE. In addition, K3.2 F382L and V471L variants exhibited a significant increase in channel conductance and a ∼20 mV negative shift in the threshold for voltage-dependent activation. Simulations of model GABAergic interneurons revealed that all variants decreased neuronal firing frequency. Thus, the variants' net loss-of-function effects disinhibited neural networks. Conclusion Our findings provide compelling evidence supporting the role of KCNC2 as a disease-causing gene in human neurodevelopmental delay and epilepsy.
目的 由KCNC2编码的电压门控钾通道K3.2有助于快速发放动作电位的GABA能中间神经元以高频发放动作电位。它对于维持哺乳动物大脑中的兴奋/抑制平衡至关重要。本研究在早发性发育性和癫痫性脑病（DEE）患者中鉴定出两个新的KCNC2新生变异体，即p.Pro470Ser（P470S）和p.Phe382Leu（F382L）。方法 为了研究DEE的分子基础，我们使用膜片钳技术和计算模型研究了变异通道的功能特性。结果 来自感染的HEK293细胞的全细胞膜片钳记录显示，K3.2 P470S和F382L变异通道的通道激活和失活动力学均显著降低。这种降低在已知与DEE相关的K3.2 p.Val471Leu（V471L）通道中也出现。此外，K3.2 F382L和V471L变异体的通道电导显著增加，电压依赖性激活阈值负移约20 mV。对模型GABA能中间神经元的模拟显示，所有变异体均降低了神经元放电频率。因此，这些变异体的净功能丧失效应解除了神经网络的抑制。结论 我们的研究结果提供了令人信服的证据，支持KCNC2作为人类神经发育迟缓及癫痫致病基因的作用。
