Arrhythmogenic mechanism of a novel ryanodine receptor mutation underlying sudden cardiac death

AIMS: The ryanodine receptor 2 (RyR2) is essential for cardiac muscle excitation–contraction coupling; dysfunctional RyR2 participates in the development of inherited arrhythmogenic cardiac disease. In this study, a novel RyR2 mutation A690E is identified from a patient with family inheritance of sudden cardiac death, and we aimed to investigate the pathogenic basis of the mutation. METHODS AND RESULTS: We generated a mouse model that carried the A690E mutation. Mice were characterized by adrenergic-induced ventricular arrhythmias similar to clinical manifestation of the patient. Optical mapping studies revealed that isolated A690E hearts were prone to arrhythmogenesis and displayed frequency-dependence calcium transient alternans. Upon β-adrenoceptor challenge, the concordant alternans was shifted towards discordant alternans that favour triggering ectopic beats and Ca(2+) re-entry; similar phenomenon was also found in the A690E cardiomyocytes. In addition, we found that A690E cardiomyocytes manifested abnormal Ca(2+) release and electrophysiological disorders, including an increased sensitivity to cytosolic Ca(2+), an elevated diastolic RyR2-mediated Ca(2+) leak, and an imbalance between Ca(2+) leak and reuptake. Structural analyses reveal that the mutation directly impacts RyR2–FK506 binding protein interaction. CONCLUSION: In this study, we have identified a novel mutation in RyR2 that is associated with sudden cardiac death. By characterizing the function defects of mutant RyR2 in animal, whole heat, and cardiomyocytes, we demonstrated the pathogenic basis of the disease-causing mutation and provided a deeper mechanistic understanding of a life-threatening cardiac arrhythmia.