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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: BACKGROUND, OBJECTIVE, METHODS, RESULTS. Meshes: Animals, Arrhythmogenic Right Ventricular Dysplasia, Gene Expression Regulation, Humans, Mice, Mice, Inbred C57BL, Mice, Transgenic, Mutation, Phenotype, Physical Conditioning, Animal, Plakophilins.
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Does exercise trigger ARVC phenotype in mice expressing a disease-causing mutated version of human plakophilin-2? Context: Exercise has been proposed as a trigger for arrhythmogenic right ventricular cardiomyopathy (ARVC) phenotype manifestation; however, research is hampered by the limited availability of animal models in which disease-associated mutations can be tested. This study evaluated the impact of exercise on ARVC cardiac manifestations in mice after adeno-associated virus (AAV)-mediated gene delivery of mutant human PKP2, which encodes the desmosomal protein plakophilin-2. We developed a new model of cardiac tissue-specific transgenic-like mice on the basis of AAV gene transfer to test the potential of a combination of a human PKP2 mutation and endurance training to trigger an ARVC-like phenotype. Stable cardiac expression of mutant PKP2 (c.2203C>T), encoding the R735X mutant protein, was achieved 4 weeks after a single AAV9-R735X intravenous injection. High-field cardiac magnetic resonance over a 10-month postinfection follow-up did not detect an overt right ventricular (RV) phenotype in nonexercised (sedentary) mice. In contrast, endurance exercise training (initiated 2 weeks after AAV9-R735X injection) resulted in clear RV dysfunction that resembled the ARVC phenotype (impaired global RV systolic function and RV regional wall motion abnormalities on cardiac magnetic resonance). At the histological level, RV samples from endurance-trained R735X-infected mice displayed connexin 43 delocalization at intercardiomyocyte gap junctions, a change not observed in sedentary mice.
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The introduction of the PKP2 R735X mutation into mice resulted in an exercise-dependent ARVC phenotype. The R735X mutation appears to function as a dominant-negative variant. This novel system for AAV-mediated introduction of a mutation into wild-type mice has broad potential for study of the implication of diverse mutations in complex cardiomyopathies. Final Decision: yes