Pierre Marion, Djemai Mohammed, Pouliot Valérie, Poulin Hugo, Gollob Michael H, Chahine Mohamed
CERVO Brain Research Centre, Quebec City, Quebec, Canada.
Inherited Arrhythmia and Cardiomyopathy Program, Division of Cardiology, University of Toronto, Toronto, Ontario, Canada.
Heart Rhythm. 2025 Jun;22(6):1574-1587. doi: 10.1016/j.hrthm.2024.09.013. Epub 2024 Sep 10.
Atrial fibrillation (AF) poses a major risk for heart failure, myocardial infarction, and stroke. Several studies have linked SCN5A variants to AF, but their precise mechanistic contribution remains unclear. Human induced pluripotent stem cells (hiPSCs) provide a promising platform for modeling AF-linked SCN5A variants and their functional alterations.
The purpose of this study was to assess the electrophysiological impact of 3 AF-linked SCN5A variants (K1493R, M1875T, N1986K) identified in 3 unrelated individuals.
CRISPR-Cas9 was used to generate a new hiPSC line in which Na1.5 was knocked out. Following differentiation into specific atrial cardiomyocyte by using retinoic acid, the adult wild-type (WT) and 3 AF variants were introduced into the Na1.5 knockout (KO) line through transfection. Subsequent analysis including molecular biology, optical mapping, and electrophysiology were performed.
The absence of Na1.5 channels altered the expression of key cardiac genes. Na1.5 KO atrial-like cardiomyocytes derived from human induced pluripotent stem cells displayed slower conduction velocities, altered action potential (AP) parameters, and impaired calcium transient propagation. The transfection of the WT channel restored sodium current density, AP characteristics and the expression of several cardiac genes. Among the AF variants, 1 induced a loss of function (N1986K) while the other 2 induced a gain of function in Na1.5 channel activity. Cellular excitability alterations and early afterdepolarizations were observed in AF variants.
Our findings suggest that distinct alterations in Na1.5 channel properties may trigger altered atrial excitability and arrhythmogenic activity in AF. Our KO model offers an innovative approach for investigating SCN5A variants in an adult human cardiac environment.
心房颤动（AF）是心力衰竭、心肌梗死和中风的主要风险因素。多项研究已将SCN5A变异与AF联系起来，但其确切的机制作用仍不清楚。人类诱导多能干细胞（hiPSC）为模拟与AF相关的SCN5A变异及其功能改变提供了一个有前景的平台。
本研究的目的是评估在3名无关个体中鉴定出的3种与AF相关的SCN5A变异（K1493R、M1875T、N1986K）的电生理影响。
使用CRISPR-Cas9生成一个新的hiPSC系，其中Na1.5被敲除。通过使用视黄酸将其分化为特定的心房心肌细胞后，通过转染将成人野生型（WT）和3种AF变异引入Na1.5敲除（KO）系。随后进行包括分子生物学、光学映射和电生理学在内的分析。
Na1.5通道的缺失改变了关键心脏基因的表达。源自人类诱导多能干细胞的Na1.5 KO心房样心肌细胞表现出较慢的传导速度、改变的动作电位（AP）参数和受损的钙瞬变传播。WT通道的转染恢复了钠电流密度、AP特征和几种心脏基因的表达。在AF变异中，1种诱导功能丧失（N1986K），而另外2种诱导Na1.5通道活性功能增强。在AF变异中观察到细胞兴奋性改变和早期后去极化。
我们的研究结果表明，Na1.5通道特性的不同改变可能触发AF中心房兴奋性改变和致心律失常活性。我们的KO模型为在成人心脏环境中研究SCN5A变异提供了一种创新方法。
