Phenotypic Characterization of a New Rat Model of Catecholaminergic Polymorphic Ventricular Tachycardia Type 3

Abstract

A spectrum of inherited and acquired cardiovascular disease can cause sudden cardiac death from calcium (Ca2+)-dependent ventricular arrhythmias. These arrhythmias are largely driven by hyperactivity of the sarcoplasmic reticulum (SR) Ca2+ release channel, the cardiac ryanodine receptor (RyR2). Treatment options to attenuate arrhythmia are limited or of poor efficacy. Therefore, it remains a priority to understand molecular mechanisms underlying RyR2 hyperactivity in disease for improved therapeutic design. Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare type of arrhythmia that has a lethal phenotype associated with Ca2+ mishandling. The disease typically presents in juveniles as ventricular tachycardia and fibrillation after stress or exercise, which can lead to sudden cardiac death. Mutations associated with CPVT are typically in RyR2 or its accessory proteins. CPVT3 is a recently reported subtype of the condition associated with mutations in trans-2,3-enoyl-CoA reductase-like protein (TECRL). Little is known about the function of TECRL in the heart, other than its localization to the sarcoplasmic reticulum. It remains entirely unknown how mutations in TECRL lead to an arrhythmogenic phenotype associated with intracellular Ca2+ mishandling and RyR2 hyperactivity. Here, we developed a new rat model of CPVT3 using CRISPR-Cas9 to introduce a patient-asssociated TECRL mutation, the single nucleotide polymorphism c.331+1G?A. Our studies with homozygous TECRL-SNP rats revealed no global cardiac remodeling, typical of the CPVT phenotype. Importantly, the rat exhibits a strong arrhythmogenic phenotype, presenting with VTs after challenge with epinephrine and caffeine. In contrast to other types of CPVT, these rats also presented with premature ventricular contractions even at baseline conditions. Confocal microscopy revealed that TECRL-SNP leads to RyR2 hyperactivity and intracellular Ca2+ mishandling, although the molecular mechanism underlying this remains unclear. Overall, we demonstrate that the TECRL-SNP rat has a strong arrhythmogenic phenotype for future studies of CPVT3.