Abstract 3865: Loss Of Plakophilin-2 Expression Leads To A Slowing Of Conduction Velocity In Monolayers Of Rat Neonatal Ventricular Myocytes
Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) is an inherited disease characterized by myocyte loss, fibrofatty infiltration, ventricular arrhythmias and sudden death. Familial ARVC has been associated to mutations in desmosomal proteins. A number of cases have been linked to mutations in the desmosomal protein plakophilin-2 (PKP2). Whether loss of PKP2 integrity affects gap junction-mediated electrical coupling remains to be determined. We have shown internalization of Cx43 in cardiac cells treated with PKP2-silencing constructs. Here, we show that loss of PKP2 expression affects action potential propagation in monolayers of rat neonatal ventricular myocytes. Cells were treated with adenoviral vectors containing a PKP2-silencing sequence. A viral construct that failed to silence PKP2 was used as a negative control. Cells were stained with voltage-sensitive dyes and conduction velocity measured by high resolution optical mapping. Preparations were paced at frequencies ranging between 1– 6 Hz. Results are shown in the graph below. A decrease in conduction velocity was observed at all frequencies. At 2Hz, for example, mean conduction velocity was 23.6±0.9 cm/s in untreated cells (X±SEM;n=9); 28.5±1.25cm/s in control cells ( n=11); and 16.75±1.28cm/s (n=7) in silenced cells (p=7.38E-07). Our data show for the first time that expression of PKP2 is required for normal electrical propagation in cardiac cells. Whether this effect is only due to loss of electrical coupling or it also involves other channel proteins remains to be determined. Our data provide a model to understand the increased propensity for cardiac arrhythmias in ARVC-afflicted patients.