CRISPR/Cas9 gene editing of patient-specific iPSC-derived cardiomyocytes corrected the aberrant cellular phenotype of the KCNH2 T983I variant, demonstrating its potential pathogenicity in LQTS.
CRISPR/Cas9 genome editing of patient-specific iPSCs can effectively determine the pathogenicity of variants of uncertain significance in cardiac channelopathies like Long QT syndrome.
BACKGROUND: The long QT syndrome (LQTS) is an arrhythmogenic disorder of QT interval prolongation that predisposes patients to life-threatening ventricular arrhythmias such as Torsades de pointes and sudden cardiac death. 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 uncertain significance (VUS), for which there is insufficient evidence of pathogenicity. OBJECTIVES: The purpose of this study was 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: Peripheral blood mononuclear cells 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 (CMs). RESULTS: Whole-cell patch clamp recordings revealed significant prolongation of the action potential duration (APD) and reduced rapidly activating delayed rectifier K+ current (IKr) density in VUS iPSC-CMs compared with healthy control iPSC-CMs. ICA-105574, a potent IKr activator, enhanced IKr magnitude and restored normal action potential duration 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: The results suggest that the KCNH2T983I VUS may be classified as potentially pathogenic.
“This is a really big problem. If someone tells me I have a genetic variant that could cause sudden cardiac death, I'm going to be very scared. The result could be a lifetime of unnecessary worry for a patient when, in fact, the variant may be completely benign.”
Garg et al. (2018) studied Long QT syndrome (LQTS) (n=2). CRISPR/Cas9 gene editing vs. Healthy control cells / Isogenic control was evaluated on Action potential duration (APD) and rapidly activating delayed rectifier K+ current (IKr) density. CRISPR/Cas9 gene editing of patient-specific iPSC-derived cardiomyocytes corrected the aberrant cellular phenotype of the KCNH2 T983I variant, demonstrating its potential pathogenicity in LQTS.
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