Shore Amy N, Li Keyong, Safari Mona, Qunies Alshaima'a M, Spitznagel Brittany D, Weaver C David, Emmitte Kyle A, Frankel Wayne N, Weston Matthew C
Fralin Biomedical Research Institute at Virginia Tech Carilion, Center for Neurobiology Research, Roanoke, VA, USA.
Department of Neurological Sciences, University of Vermont, Burlington, VT, USA.
bioRxiv. 2024 Aug 2:2023.10.11.561953. doi: 10.1101/2023.10.11.561953.
More than twenty recurrent missense gain-of-function (GOF) mutations have been identified in the sodium-activated potassium (K) channel gene in patients with severe developmental and epileptic encephalopathies (DEEs), most of which are resistant to current therapies. Defining the neuron types most vulnerable to KCNT1 GOF will advance our understanding of disease mechanisms and provide refined targets for precision therapy efforts. Here, we assessed the effects of heterozygous expression of a GOF variant (Y777H) on K currents and neuronal physiology among cortical glutamatergic and GABAergic neurons in mice, including those expressing vasoactive intestinal polypeptide (VIP), somatostatin (SST), and parvalbumin (PV), to identify and model the pathogenic mechanisms of autosomal dominant GOF variants in DEEs. Although the -Y777H variant had no effects on glutamatergic or VIP neuron function, it increased subthreshold K currents in both SST and PV neurons but with opposite effects on neuronal output; SST neurons became hypoexcitable with a higher rheobase current and lower action potential (AP) firing frequency, whereas PV neurons became hyperexcitable with a lower rheobase current and higher AP firing frequency. Further neurophysiological and computational modeling experiments showed that the differential effects of the Y777H variant on SST and PV neurons are not likely due to inherent differences in these neuron types, but to an increased persistent sodium current in PV, but not SST, neurons. The Y777H variant also increased excitatory input onto, and chemical and electrical synaptic connectivity between, SST neurons. Together, these data suggest differential pathogenic mechanisms, both direct and compensatory, contribute to disease phenotypes, and provide a salient example of how a pathogenic ion channel variant can cause opposite functional effects in closely related neuron subtypes due to interactions with other ionic conductances.
在患有严重发育性和癫痫性脑病（DEE）的患者中，已在钠激活钾（K）通道基因中鉴定出二十多种复发性错义功能获得性（GOF）突变，其中大多数对当前治疗具有抗性。确定对KCNT1 GOF最敏感的神经元类型将增进我们对疾病机制的理解，并为精准治疗提供更精确的靶点。在此，我们评估了一种GOF变体（Y777H）的杂合表达对小鼠皮质谷氨酸能和γ-氨基丁酸能神经元（包括表达血管活性肠肽（VIP）、生长抑素（SST）和小白蛋白（PV）的神经元）的K电流和神经元生理学的影响，以识别和模拟DEE中常染色体显性GOF变体的致病机制。虽然-Y777H变体对谷氨酸能或VIP神经元功能没有影响，但它增加了SST和PV神经元的阈下K电流，但对神经元输出有相反的影响；SST神经元变得兴奋性降低，具有更高的阈电流和更低的动作电位（AP）发放频率，而PV神经元变得兴奋性增加，具有更低的阈电流和更高的AP发放频率。进一步的神经生理学和计算建模实验表明，Y777H变体对SST和PV神经元的不同影响不太可能是由于这些神经元类型的固有差异，而是由于PV神经元而非SST神经元中持续钠电流增加。Y777H变体还增加了对SST神经元的兴奋性输入以及SST神经元之间的化学和电突触连接。总之，这些数据表明，直接和代偿性的不同致病机制导致了疾病表型，并提供了一个突出的例子，说明致病离子通道变体如何由于与其他离子电导的相互作用而在密切相关的神经元亚型中引起相反的功能效应。
