Patient-specific iPSC-derived cardiomyocytes reveal variable phenotypic severity of Brugada syndrome.

BACKGROUND: Brugada syndrome (BrS) is a cardiac channelopathy that can result in sudden cardiac death (SCD). SCN5A is the most frequent gene linked to BrS, but the genotype-phenotype correlations are not completely matched. Clinical phenotypes of a particular SCN5A variant may range from asymptomatic to SCD. Here, we used comparison of induced pluripotent stem cell-derived cardiomyocytes (iPSC-CMs) derived from a SCN5A mutation-positive (D356Y) BrS family with severely affected proband, asymptomatic mutation carriers (AMCs) and healthy controls to investigate this variation. METHODS: 26 iPSC lines were generated from skin fibroblasts using nonintegrated Sendai virus. The generated iPSCs were differentiated into cardiomyocytes using a monolayer-based differentiation protocol. FINDINGS: D356Y iPSC-CMs exhibited increased beat interval variability, slower depolarization, cardiac arrhythmias, defects of Na+ channel function and irregular Ca2+ signaling, when compared to controls. Importantly, the phenotype severity observed in AMC iPSC-CMs was milder than that of proband iPSC-CMs, an observation exacerbated by flecainide. Interestingly, the iPSC-CMs of the proband exhibited markedly decreased Ca2+ currents in comparison with control and AMC iPSC-CMs. CRISPR/Cas9-mediated genome editing to correct D356Y in proband iPSC-CMs effectively rescued the arrhythmic phenotype and restored Na+ and Ca2+ currents. Moreover, drug screening using established BrS iPSC-CM models demonstrated that quinidine and sotalol possessed antiarrhythmic effects in an individual-dependent manner. Clinically, venous and oral administration of calcium partially reduced the malignant arrhythmic events of the proband in mid-term follow-up. INTERPRETATION: Patient-specific and genome-edited iPSC-CMs can recapitulate the varying phenotypic severity of BrS. Our findings suggest that preservation of the Ca2+ currents might be a compensatory mechanism to resist arrhythmogenesis in BrS AMCs. FUNDING: National Key R&D Program of China (2017YFA0103700), National Natural Science Foundation of China (81922006, 81870175), Natural Science Foundation of Zhejiang Province (LD21H020001, LR15H020001), National Natural Science Foundation of China (81970269), Key Research and Development Program of Zhejiang Province (2019C03022) and Natural Science Foundation of Zhejiang Province (LY16H020002).

Generation of an induced pluripotent stem cell line from a long QT syndrome patient carrying KCNH2/1956C > A mutation.

Long QT syndrome (LQT) is an inherited primary arrhythmic disorder characterized by prolonged QT interval on the surface electrocardiogram and life-threatening arrhythmia. In this study, a skin biopsy was obtained from an LQT type 2 (LQT2) patient, who carried a nonsense mutation (c.1956C > A; p.Y652X) in the potassium voltage-gated channel subfamily H member 2 (KCNH2) gene. The skin fibroblasts were reprogrammed by non-integrated Sendai viral method to generate a patient-specific induced pluripotent stem cell (iPSC) line. The generated iPSC line showed typical embryonic stem cell-like morphology, exhibited normal karyotype, expressed pluripotency markers, and was capable to differentiate into three germ layers.