An Epilepsy-Associated KCNT1 Mutation Enhances Excitability of Human iPSC-Derived Neurons by Increasing Slack KNa Currents
An Epilepsy-Associated KCNT1 Mutation Enhances Excitability of Human iPSC-Derived Neurons by Increasing Slack KNa Currents
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DOI：
10.1523/jneurosci.1628-18.2019
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发表时间：
2019-09-11
影响因子：
5.3
通讯作者：
Kaczmarek, Leonard K.
中科院分区：
文献类型：
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作者：
Quraishi, Imran H.;Stern, Shani;Kaczmarek, Leonard K.
KCNT1 （Slack， K(Na)1.1）钠活化钾通道的突变可导致严重的癫痫性脑病。在异源系统中的表达表明，致病突变会产生电流振幅增加的通道。然而，目前尚不清楚这种功能增益是否发生在人类神经元中，也不知道这种增加的K-Na电流是否有望抑制或增加皮质神经元的兴奋性。利用基因工程人类诱导多能干细胞（iPSC）衍生的神经元，我们现在发现，在携带纯合子P924L突变的神经元中，钠依赖性钾电流增加了数倍。在电流钳记录中，P924L突变的神经元中K-Na电流的增加缩短了动作电位的持续时间，增加了每个动作电位后的超极化幅度。引人注目的是，在表达突变通道的神经元中，去极化电流诱发的动作电位数量和最大放电率都增加了。在自发活动神经元网络中，P924L Slack突变神经元的平均放电率、动作电位快速爆发的发生以及爆发时的放电强度均增加。通过数值模拟验证了增加K-Na电流在不依赖任何补偿变化的情况下提高发射速率的可行性。我们的研究结果表明，Slack K-Na通道的功能获得会导致孤立神经元和神经网络中的超兴奋性，并且通过细胞自主机制发生，不需要网络相互作用。
Mutations in the KCNT1 (Slack, K(Na)1.1) sodium-activated potassium channel produce severe epileptic encephalopathies. Expression in heterologous systems has shown that the disease-causing mutations give rise to channels that have increased current amplitude. It is not known, however, whether such gain of function occurs in human neurons, nor whether such increased K-Na current is expected to suppress or increase the excitability of cortical neurons. Using genetically engineered human induced pluripotent stem cell (iPSC)-derived neurons, we have now found that sodium-dependent potassium currents are increased several-fold in neurons bearing a homozygous P924L mutation. In current-clamp recordings, the increased K-Na current in neurons with the P924L mutation acts to shorten the duration of action potentials and to increase the amplitude of the afterhyperpolarization that follows each action potential. Strikingly, the number of action potentials that were evoked by depolarizing currents as well as maximal firing rates were increased in neurons expressing the mutant channel. In networks of spontaneously active neurons, the mean firing rate, the occurrence of rapid bursts of action potentials, and the intensity of firing during the burst were all increased in neurons with the P924L Slack mutation. The feasibility of an increased K-Na current to increase firing rates independent of any compensatory changes was validated by numerical simulations. Our findings indicate that gain-of-function in Slack K-Na channels causes hyperexcitability in both isolated neurons and in neural networks and occurs by a cell-autonomous mechanism that does not require network interactions.