Sympathetic activation is an established trigger of life-threatening cardiac events in long QT syndrome type 1 (LQT1). KCNQ1 loss-of-function variants, which underlie LQT1, have been associated with both cardiac arrhythmia and neuronal hyperactivity pathologies. However, the LQT1 sympathetic neuronal phenotype is unknown. Here we aimed to study human induced pluripotent stem cell (hiPSC)-derived sympathetic neurons (SNs) to evaluate neuronal functional phenotype in LQT1. We generated hiPSC-SNs from two LQT1 patients with a history of sympathetically triggered arrhythmia and KCNQ1 loss-of-function genotypes (c.781_782delinsTC and p.S349W/p.R518X). Characterisation of hiPSC-SNs was performed using immunohistochemistry, enzyme-linked immunosorbent assay and whole-cell patch clamp electrophysiology, and functional LQT1 hiPSC-SN phenotypes compared to healthy control (WT) hiPSC-SNs. hiPSC-SNs stained positive for tyrosine hydroxylase, peripherin, KCNQ1, and secreted noradrenaline. hiPSC-SNs at 60±2.2 days in vitro had healthy resting membrane potentials (-60±1.3 mV), and fired rapid action potentials with mature kinetics in response to stimulation. Significant hyperactivity in LQT1 hiPSC-SNs was evident via increased noradrenaline release, increased spontaneous action potential frequency, increased total inward current density, and reduced afterhyperpolarisation, compared to age-matched WT hiPSC-SNs. A significantly higher action potential frequency upon current injection and larger synaptic current amplitudes in compound heterozygous p.S349W/p.R518X hiPSC-SNs compared to heterozygous c.781_782delinsTC hiPSC-SNs was also observed, suggesting a potential genotype-phenotype correlation. Together our data reveal increased neurotransmission and excitability in heterozygous and compound heterozygous patient-derived LQT1 sympathetic neurons, suggesting that the cellular arrhythmogenic potential in LQT1 is not restricted to cardiomyocytes.

中文翻译：

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长 QT 综合征 1 型多能干细胞衍生交感神经元的功能亢进

交感神经激活是 1 型长 QT 综合征 (LQT1) 中危及生命的心脏事件的既定触发因素。作为 LQT1 基础的 KCNQ1 功能丧失变体与心律失常和神经元活动过度病理有关。然而，LQT1 交感神经元表型是未知的。在这里，我们旨在研究人类诱导多能干细胞 (hiPSC) 衍生的交感神经元 (SN)，以评估 LQT1 中的神经元功能表型。我们从两名有交感神经触发的心律失常和 KCNQ1 功能丧失基因型（c.781_782delinsTC 和 p.S349W/p.R518X）病史的 LQT1 患者生成 hiPSC-SN。使用免疫组织化学、酶联免疫吸附测定和全细胞膜片钳电生理学对 hiPSC-SNs 进行表征，和功能性 LQT1 hiPSC-SN 表型与健康对照 (WT) hiPSC-SN 相比。hiPSC-SN 对酪氨酸羟化酶、外周蛋白、KCNQ1 和分泌的去甲肾上腺素染色呈阳性。体外 60±2.2 天的 hiPSC-SNs 具有健康的静息膜电位 (-60±1.3 mV)，并以成熟的动力学响应刺激发射快速动作电位。与年龄匹配的 WT hiPSC-SNs 相比，通过增加去甲肾上腺素释放、增加自发动作电位频率、增加总内向电流密度和减少后超极化，LQT1 hiPSC-SNs 的显着过度活跃是显而易见的。还观察到与杂合 c.781_782delinsTC hiPSC-SN 相比，复合杂合 p.S349W/p.R518X hiPSC-SN 中电流注入时的动作电位频率显着更高，突触电流幅度更大，表明潜在的基因型-表型相关性。我们的数据一起显示杂合子和复合杂合子患者来源的 LQT1 交感神经元的神经传递和兴奋性增加，表明 LQT1 中的细胞致心律失常潜能不仅限于心肌细胞。