Postdoctoral Researcher University of Oxford, England, United Kingdom
Abstract: Long QT Syndrome Type 1 (LQT1) is a heritable cardiac disorder that can affect individuals of all ages. While often asymptomatic, it can lead to life-threatening arrhythmias, particularly under stress or intense physical activity. The condition is typically marked by prolonged action potential duration (APD) caused by mutations in the KCNQ1 gene, which encodes a cardiac potassium channel. Nitric Oxide Synthase Adaptor Protein (NOS1AP) – a chaperone involved in NO signalling in both cardiomyocytes (CMs) and sympathetic neurons – is a common variant in QT prolongation. Overexpression of NOS1AP shortens APD by accelerating repolarisation in guinea-pig ventricular myocytes. Here, we investigated the therapeutic utility of NOS1AP in a human model of LQT1, by differentiating induced pluripotent stem cells (iPSCs) into CMs for use at day 30-35 and transducing them with an adenoviral vector encoding NOS1AP marked by mCherry fluorescence, or the empty vector. Structural properties were assessed via scanning ion conductance microscopy and confocal microscopy, while functional analyses include optical mapping and multielectrode array (MEA) recordings. First, western blot confirmed overexpression of NOS1AP in CMs. Preliminary results show that LQT1-CMs exhibit significantly reduced cell area and decreased membrane stiffness compared to healthy CMs, reflecting the fragility of the disease phenotype. NOS1AP caused an increase in membrane stiffness of LQT1-CMs, comparable to that of healthy CMs. Confocal imaging revealed an inversion of alpha and beta-tubulin expression in LQT1-CM, signifying disruption of the microtubule complex; which were reversed to levels comparable to healthy CMs with NOS1AP. Optical mapping showed increased calcium transient amplitudes in LQT1-CMs, and MEAs demonstrated prolonged field potential duration and RR intervals (decreased beat rate). Notably, NOS1AP treatment shortened MEA electrograms in LQT1-CMs, approaching those of healthy controls. This study highlights key structural and functional features of hiPSC derived LQT1-CMs. We further show that NOS1AP gene transfer in a human model of LQT1 syndrome may provide a therapeutic opportunity to restore a normal electrophysiological phenotype.
