De novo missense mutations in SCN8A gene encoding voltage-gated sodium channel Na_V1.6 are linked to a severe form of early infantile epileptic encephalopathy named early infantile epileptic encephalopathy type13 (EIEE13). The majority of the patients with EIEE13 does not respond favorably to the antiepileptic drugs (AEDs) in clinic and has a significantly increased risk of death. Although more than 60 EIEE13-associated mutations have been discovered, only few mutations have been functionally analyzed. In this study we investigated the functional influences of mutations N1466T and N1466K, two EIEE13-associated mutations located in the inactivation gate, on sodium channel properties. Sodium currents were recorded from CHO cells expressing the mutant and wide-type (WT) channels using the whole-cell patch-clamp technique. We found that, in comparison with WT channels, both the mutant channels exhibited increased window currents, persistent currents (I_NaP) and ramp currents, suggesting that N1466T and N1466K were gain-of-function (GoF) mutations. Sodium channel inhibition is one common mechanism of currently available AEDs, in which topiramate (TPM) was effective in controlling seizures of patients carrying either of the two mutations. We found that TPM (100 µM) preferentially inhibited I_NaP and ramp currents but did not affect transient currents (I_NaT) mediated by N1466T or N1466K. Among the other 6 sodium channel-inhibiting AEDs tested, phenytoin and carbamazepine displayed greater efficacy than TPM in suppressing both I_NaP and ramp currents. Functional characterization of mutants N1466T and N1466K is beneficial for understanding the pathogenesis of EIEE13. The divergent effects of sodium channel-inhibiting AEDs on I_NaP and ramp currents provide insight into the development of therapeutic strategies for the N1466T and N1466K-associated EIEE13.

_{编码电压门控钠通道 Na V}的 SCN8A 基因的新生错义突变1.6 与称为早期婴儿癫痫性脑病 13 型 (EIEE13) 的严重形式的早期婴儿癫痫性脑病有关。大多数 EIEE13 患者对临床抗癫痫药物 (AED) 反应不佳，死亡风险显着增加。尽管已发现 60 多个 EIEE13 相关突变，但仅对少数突变进行了功能分析。在这项研究中，我们调查了突变 N1466T 和 N1466K 对钠通道特性的功能影响，这两个 EIEE13 相关突变位于失活门中。使用全细胞膜片钳技术从表达突变体和宽型 (WT) 通道的 CHO 细胞中记录钠电流。我们发现，与 WT 通道相比，两个突变通道都表现出增加的窗口电流，I _NaP ) 和斜坡电流，表明 N1466T 和 N1466K 是功能获得 (GoF) 突变。钠通道抑制是目前可用的 AED 的一种常见机制，其中托吡酯 (TPM) 可有效控制携带两种突变之一的患者的癫痫发作。我们发现 TPM (100 µM) 优先抑制I _NaP和斜坡电流，但不影响由 N1466T 或 N1466K 介导的瞬态电流 ( I _{NaT )。}在测试的其他 6 种钠通道抑制 AED 中，苯妥英钠和卡马西平在抑制I _{NaP方面显示出比 TPM 更大的功效}和斜坡电流。突变体 N1466T 和 N1466K 的功能表征有助于理解 EIEE13 的发病机制。钠通道抑制 AEDs 对I _NaP和斜坡电流的不同影响提供了对 N1466T 和 N1466K 相关 EIEE13 治疗策略发展的洞察力。