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

Area of Science:

• Cardiovascular Research
• Molecular Cardiology
• Genetics of Cardiac Disease

Background:

• Ryanodine receptor 2 (RyR2) is critical for cardiac excitation-contraction coupling.
• RyR2 dysfunction is implicated in inherited arrhythmogenic cardiac diseases and sudden cardiac death.
• Identifying novel mutations and their mechanisms is crucial for understanding these conditions.

Purpose of the Study:

• To investigate the pathogenic basis of a novel RyR2 mutation, A690E, identified in a patient with a family history of sudden cardiac death.
• To characterize the functional consequences of the A690E mutation in RyR2.

Main Methods:

• Generation of a mouse model harboring the RyR2 A690E mutation.
• In vivo characterization of arrhythmias and ex vivo optical mapping of hearts and isolated cardiomyocytes.
• Analysis of calcium handling, RyR2-mediated calcium leak, and RyR2-FK506 binding protein interaction.

Main Results:

• The A690E mutation induced adrenergic-dependent ventricular arrhythmias in mice, mirroring patient symptoms.
• Isolated A690E hearts and cardiomyocytes exhibited arrhythmogenesis, frequency-dependent calcium transient alternans, and a shift towards discordant alternans.
• Mutant RyR2 displayed increased sensitivity to calcium, elevated diastolic calcium leak, and impaired calcium leak-reuptake balance, impacting RyR2-FKBP interaction.

Conclusions:

• The novel RyR2 A690E mutation is pathogenic and associated with sudden cardiac death.
• The study provides mechanistic insights into RyR2-mediated calcium release defects underlying life-threatening cardiac arrhythmias.
• Understanding these molecular defects is vital for developing therapeutic strategies for inherited cardiac diseases.