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Updated: May 16, 2026
Dual-Dye Optical Mapping of Hearts from RyR2R2474S Knock-In Mice of Catecholaminergic Polymorphic Ventricular Tachycardia
Published on: December 22, 2023
Heterogeneity of ryanodine receptor dysfunction in a mouse model of catecholaminergic polymorphic ventricular
Randall Loaiza1, Nancy A Benkusky, Patricia P Powers
1Center for Arrhythmia Research, Cardiovascular Division, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA.
Rationale:
Most cardiac ryanodine receptor (RyR2) mutations associated with catecholaminergic polymorphic ventricular tachycardia (CPVT) are postulated to cause a distinctive form of Ca(2+) release dysfunction. Considering the spread distribution of CPVT mutations, we hypothesized that dysfunctional heterogeneity also was feasible.
Objective:
To determine the molecular and cellular mechanisms by which a novel RyR2-V2475F mutation associated with CPVT in humans triggers Ca(2+)-dependent arrhythmias in whole hearts and intact mice.
Methods And Results:
Recombinant channels harboring CPVT-linked RyR2 mutations were functionally characterized using tritiated ryanodine binding and single-channel recordings. Homologous recombination was used to generate a knock-in mouse bearing the RyR2-V2475F mutation. Ventricular myocytes from mice heterozygous for the mutation (RyR2-V2475F(+/-)) and their wild-type littermates were Ca(2+)-imaged by confocal microscopy under conditions that mimic stress. The propensity of wild-type and RyR2-V2475F(+/-) mice to have development of arrhythmias was tested at the whole heart level and in intact animals. Recombinant RyR2-V2475F channels displayed increased cytosolic Ca(2+) activation, abnormal protein kinase A phosphorylation, and increased activation by luminal Ca(2+). The RyR2-V2475F mutation appears embryonic-lethal in homozygous mice, but heterozygous mice have no alterations at baseline. Spontaneous Ca(2+) release events were more frequent and had shorter latency in isoproterenol-stimulated cardiomyocytes from RyR2-V2475F(+/-) hearts, but their threshold was unchanged with respect to wild-type. Adrenergically triggered tachyarrhythmias were more frequent in RyR2-V2475F(+/-) mice.
Conclusions:
The mutation RyR2-V2475F is phenotypically strong among other CPVT mutations and produces heterogeneous mechanisms of RyR2 dysfunction. In living mice, this mutation appears too severe to be harbored in all RyR2 channels but remains undetected under basal conditions if expressed at relatively low levels. β-adrenergic stimulation breaks the delicate Ca(2+) equilibrium of RyR2-V2475F(+/-) hearts and triggers life-threatening arrhythmias.
Insights
A novel RyR2-V2475F mutation causes catecholaminergic polymorphic ventricular tachycardia (CPVT) by disrupting cardiac calcium handling. This mutation triggers arrhythmias under stress, highlighting RyR2 dysfunction in CPVT.
Area of Science:
- Cardiovascular Research
- Molecular Cardiology
- Genetics
Background:
- Catecholaminergic polymorphic ventricular tachycardia (CPVT) is linked to cardiac ryanodine receptor 2 (RyR2) mutations causing calcium release dysfunction.
- Heterogeneous RyR2 dysfunction is a potential mechanism for CPVT given mutation spread.
Purpose of the Study:
- To investigate the molecular and cellular mechanisms of a novel RyR2-V2475F mutation in CPVT.
- To determine how this mutation triggers calcium-dependent arrhythmias in mice.
Main Methods:
- Functional characterization of RyR2-V2475F using recombinant channels and single-channel recordings.
- Generation of RyR2-V2475F knock-in mice and analysis of ventricular myocytes.
- In vivo assessment of arrhythmias in heterozygous mice under basal and stimulated conditions.
Main Results:
- RyR2-V2475F channels showed increased calcium activation and abnormal phosphorylation.
- Heterozygous RyR2-V2475F mice exhibited more frequent spontaneous calcium release in cardiomyocytes under stress.
- Adrenergic stimulation in heterozygous mice led to increased tachyarrhythmias.
Conclusions:
- The RyR2-V2475F mutation is a potent CPVT mutation with heterogeneous RyR2 dysfunction mechanisms.
- While homozygous RyR2-V2475F is embryonic-lethal, heterozygous expression causes arrhythmias under adrenergic stress.
- This mutation disrupts cardiac calcium homeostasis, leading to life-threatening arrhythmias in CPVT patients.
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