Mechanistic Insights and Therapeutic Approaches for Plakophilin-2 Driven Arrhythmogenic Right Ventricular Cardiomyopathy

Arrhythmogenic right ventricular cardiomyopathy (ARVC) is a fatal genetic cardiac disease with no available treatments. ARVC is termed a “disease of the desmosome” as 30-60% of ARVC mutations occur in genes of the desmosome, which is a critical cell-cell adhesion structure. The desmosomal component plakophilin-2 (PKP2) is the most frequently mutated gene causal for ARVC and studies highlight altered RNA splicing as a mechanism through which PKP2 patient genetics may drive ARVC. Additional work shows one third of human disease-causing mutations are a result of defects in RNA splicing, highlighting the importance of testing the contribution of this mechanism in ARVC. However, limited models and mechanistic insights exist into how RNA splicing mutations drive ARVC pathogenesis. I have defined disease mechanisms and developed therapeutic approaches for a novel mouse model harboring a PKP2 splice acceptor site mutation (PKP2 IVS10-1 G>C) found in multiple ARVC populations. My work highlighted the sufficiency of this mutation to trigger all classic ARVC disease features including sudden death, ventricular arrhythmias, biventricular dysfunction, and fibro-fatty replacement in PKP2 homozygous mutant (PKP2 Hom) mice. PKP2 Hom mice displayed an early disruption of the desmosome, which extended to the gap junction at the onset of disease features, highlighting a progressive breakdown of the cardiac intercalated disc in disease. RNA analysis in PKP2 Hom hearts revealed an aberrantly spliced mutant transcript and significantly reduced RNA levels, which was translated into a higher molecular weight mutant PKP2 protein at reduced levels in the absence of endogenous PKP2. In vitro mechanistic studies increasing wild-type or mutant PKP2 protein improved desmosomal components, suggesting PKP2 protein dose drives ARVC pathogenesis. Early in vivo restoration of PKP2 with an adeno-associated virus (AAV9 PKP2) was sufficient to prevent intercalated disc dissolution, which provided durable preservation of cardiac function and prevented mortality in PKP2 Hom mice. Late-stage AAV9 PKP2 treatment could similarly reassemble desmosomal proteins, while also improving cardiac mechanical function to avert PKP2 Hom mouse mortality. My studies demonstrate the sufficiency of RNA splicing mutations to drive ARVC and provide critical mechanistic insights into disease pathogenesis, which informed the rational design of ARVC therapeutics