Abstract 256: Precision Medicine in Cardiac Channelopathy: Integrating Genome Editing and Induced Pluripotent Stem Cells to Decipher Variant of Unknown Significance

Abstract

Background: The long QT syndrome (LQTS) is an arrhythmogenic disorder of QT interval prolongation that predisposes patients to life-threatening ventricular arrhythmias such as Torsade de pointes (TdP) and sudden cardiac death (SCD). Clinical genetic testing has emerged as the standard of care to identify genetic variants in patients suspected of having LQTS. However, these results are often confounded by the discovery of variants of unknown significance (VUS), for which there is insufficient evidence of pathogenicity. Objectives: To demonstrate that genome editing of patient-specific induced pluripotent stem cells (iPSCs) can be a valuable approach to delineate the pathogenicity of VUS in cardiac channelopathy. Methods and Results: Peripheral blood mononuclear cells (PBMCs) were isolated from a carrier with a novel missense variant (T983I) in the KCNH2 (LQT2) gene and an unrelated healthy control subject. iPSCs were generated using an integration-free Sendai virus and differentiated to iPSC-derived cardiomyocytes (iPSC-CMs). Whole-cell patch clamp recordings revealed significant prolongation of the action-potential duration (APD) and reduced rapidly activating delayed rectifier K + current ( I Kr ) density in VUS iPSC-CMs compared to healthy control iPSC-CMs. ICA-105574, a potent I Kr activator, enhanced I Kr magnitude and restored normal APD in VUS iPSC-CMs. Notably, VUS iPSC-CMs exhibited greater propensity to proarrhythmia than healthy control cells in response to high-risk torsadogenic drugs (dofetilide, ibutilide, and azimilide), suggesting a compromised repolarization reserve. Finally, the selective correction of the causal variant in iPSC-CMs using CRISPR/Cas9 gene editing (isogenic control) normalized the aberrant cellular phenotype, whereas the introduction of the homozygous variant in healthy control cells recapitulated hallmark features of the LQTS disorder. Conclusions: Our results suggest that the KCNH2 T983I VUS may be classified as potentially pathogenic.