Center for Interdisciplinary Research on Brain and Learning (CIRCA), Department of Physics and Department of Pharmacology and Physiology, Université de Montréal, Montréal, QC, Canada.
Centre de Recherche Du Centre Hospitalier Universitaire Sainte-Justine, Université de Montréal, Montréal, QC H3T 1C5, Canada.
Am J Hum Genet. 2024 Apr 4;111(4):761-777. doi: 10.1016/j.ajhg.2024.02.014. Epub 2024 Mar 18.
Ion channels mediate voltage fluxes or action potentials that are central to the functioning of excitable cells such as neurons. The KCNB family of voltage-gated potassium channels (Kv) consists of two members (KCNB1 and KCNB2) encoded by KCNB1 and KCNB2, respectively. These channels are major contributors to delayed rectifier potassium currents arising from the neuronal soma which modulate overall excitability of neurons. In this study, we identified several mono-allelic pathogenic missense variants in KCNB2, in individuals with a neurodevelopmental syndrome with epilepsy and autism in some individuals. Recurrent dysmorphisms included a broad forehead, synophrys, and digital anomalies. Additionally, we selected three variants where genetic transmission has not been assessed, from two epilepsy studies, for inclusion in our experiments. We characterized channel properties of these variants by expressing them in oocytes of Xenopus laevis and conducting cut-open oocyte voltage clamp electrophysiology. Our datasets indicate no significant change in absolute conductance and conductance-voltage relationships of most disease variants as compared to wild type (WT), when expressed either alone or co-expressed with WT-KCNB2. However, variants c.1141A>G (p.Thr381Ala) and c.641C>T (p.Thr214Met) show complete abrogation of currents when expressed alone with the former exhibiting a left shift in activation midpoint when expressed alone or with WT-KCNB2. The variants we studied, nevertheless, show collective features of increased inactivation shifted to hyperpolarized potentials. We suggest that the effects of the variants on channel inactivation result in hyper-excitability of neurons, which contributes to disease manifestations.
离子通道介导电压通量或动作电位，这对于神经元等可兴奋细胞的功能至关重要。电压门控钾通道 (Kv) 的 KCNB 家族由两个成员 (KCNB1 和 KCNB2) 组成，分别由 KCNB1 和 KCNB2 编码。这些通道是源自神经元胞体的延迟整流钾电流的主要贡献者，调节神经元的整体兴奋性。在这项研究中，我们在一些个体中发现了 KCNB2 中的几种单等位基因致病性错义变体，这些个体患有伴有癫痫和自闭症的神经发育综合征。反复出现的畸形包括宽额头、连心眉和数字异常。此外，我们从两项癫痫研究中选择了三种尚未评估遗传传递的变体，将其纳入我们的实验。我们通过在非洲爪蟾卵母细胞中表达这些变体并进行切开卵母细胞电压钳电生理学来表征这些变体的通道特性。我们的数据表明，与野生型 (WT) 相比，大多数疾病变体的绝对电导和电导-电压关系没有显著变化，无论是单独表达还是与 WT-KCNB2 共表达时。然而，变体 c.1141A>G (p.Thr381Ala) 和 c.641C>T (p.Thr214Met) 单独表达时完全阻断电流，前者在单独表达或与 WT-KCNB2 共表达时表现出激活中点的左移。然而，我们研究的变体表现出集体的失活增强特征，失活向超极化电位移动。我们认为，变体对通道失活的影响导致神经元过度兴奋，这导致了疾病表现。
