Characterization of A Novel Mouse Model of Arrhythmogenic Right Ventricular Cardiomyopathy Harboring Plakophilin-2 Patient Genetics

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a genetic cardiac disease and a leading cause of sudden cardiac death (SCD) in young athletes, often triggered by exercise (adrenergic stress). Through genetic studies, 40% of ARVC patients have mutations withindesmosomal genes, a mechanical junction that helps anchor cells together. Plakophilin-2 (PKP2) is the most mutated desmosomal gene; however, there are limited insights on underlying mechanisms that drive ARVC due to PKP2 patient genetics. In my studies, I have characterized a newly generated knockin mouse model that harbors a prevalent human PKP2 splice site mutation (c.2146-1G>C) that we show recapitulates the full spectrum of ARVC in mice. PKP2 Homozygous (Hom) mutant mice are viable at birth butexhibit SCD starting at 4 weeks while encompassing full disease features of ARVC. I hypothesized that neonatal PKP2 Hom mutant mice will represent a stage where early ARVC disease features are observed in the absence of overt structural disease. My thesis studies have shown that neonatal PKP2 Hom mutant hearts do not exhibit significant differences in (i) gross morphology as evidenced by similar heart weight to body weight ratios to controls and (ii) gene expression of cardiac stress markers and pro-fibrotic geneswhen compared to controls. However, upon protein blot analysis, I discovered neonatal PKP2 mutant cardiomyocytes harbored a larger molecular weight PKP2 mutant protein, in the absence of endogenous PKP2 alongside specific loss of desmosomal junctional proteins (desmoplakin, desmoglein-2) when compared to controls. These defects were observed in the absence of effects on other mechanical junction (fascia adherens junction) genes as evidenced by intact localization of N-cadherin. Furthermore, I observed baseline arrhythmias in neonatal PKP2 Hom mutant cardiomyocytes, which are reminiscent of the early electrical dysfunction seen in ARVCpatients, in the absence of overt structural disease. In conclusion, my thesis studies have identified a stage in our PKP2 Hom mutant model that will help define early disease driving pathways, thus providing insights into mechanisms driving electrical dysfunction and SCD inARVC