Cardiomyocytes generated from CPVT^D307H patients are arrhythmogenic in response to β‐adrenergic stimulation

Abstract

Sudden cardiac death caused by ventricular arrhythmias is a disastrous event, especially when it occurs in young individuals. Among the five major arrhythmogenic disorders occurring in the absence of a structural heart disease is catecholaminergic polymorphic ventricular tachycardia (CPVT), which is a highly lethal form of inherited arrhythmias. Our study focuses on the autosomal recessive form of the disease caused by the missense mutation D307H in the cardiac calsequestrin gene, CASQ2. Because CASQ2 is a key player in excitation contraction coupling, the derangements in intracellular Ca2+ handling may cause delayed afterdepolarizations (DADs), which constitute the mechanism underlying CPVT. To investigate catecholamine-induced arrhythmias in the CASQ2 mutated cells, we generated for the first time CPVT-derived induced pluripotent stem cells (iPSCs) by reprogramming fibroblasts from skin biopsies of two patients, and demonstrated that the iPSCs carry the CASQ2 mutation. Next, iPSCs were differentiated to cardiomyocytes (iPSCs-CMs), which expressed the mutant CASQ2 protein. The major findings were that the β-adrenergic agonist isoproterenol caused in CPVT iPSCs-CMs (but not in the control cardiomyocytes) DADs, oscillatory arrhythmic prepotentials, after-contractions and diastolic [Ca2+]i rise. Electron microscopy analysis revealed that compared with control iPSCs-CMs, CPVT iPSCs-CMs displayed a more immature phenotype with less organized myofibrils, enlarged sarcoplasmic reticulum cisternae and reduced number of caveolae. In summary, our results demonstrate that the patient-specific mutated cardiomyocytes can be used to study the electrophysiological mechanisms underlying CPVT.

RyR2R420Q catecholaminergic polymorphic ventricular tachycardia mutation induces bradycardia by disturbing the coupled clock pacemaker mechanism

“…The RyR 2 R420Q loses the capacity to bind Cl -, which maintains the three regions of the N terminal domain in place (45), although the functional consequences remained to be elucidated. In a previous study on induced pluripotent cardiac myocytes (iPS-CM), including the RyR 2 R420Q mutation, a decrease of spontaneous beating rate was observed, which is consistent with our data (47). However, most of the RyR 2…”

Induced pluripotent stem cell–derived cardiomyocytes in studies of inherited arrhythmias

“…Novak et al (43) studied iPS-derived myocytes obtained from patients with the D307H mutation in the gene encoding for cardiac calsequestrin. This mutation has been extensively characterized, and it is associated with a very severe form of CPVT (44).…”

Disease Models for the Genetic Cardiac Diseases

“…Multiple iPS-based CPVT disease models have been published, most of them having the disease specific mutation in the RyR2 gene while [83][84][85] and one having the mutation in the CASQ2 gene [86]. The congruent result from these CPVT model studies was the occurrence of delayed after depolarizations (DADs) and arrhythmias which are caused by the aberrant diastolic Ca 2+ from the SR.…”