Abstract 13630: Wnt Activation Reverses Action Potential Phenotype and Decreased Sodium Current in Zebrafish Model of ARVC
Altered Wnt/β-catenin signaling has been implicated in the pathogenesis of arrhythmogenic right ventricular cardiomyopathy (ARVC). Moreover, a decrease in sodium inward current (INa) has been shown in a cultured rat ventricular myocytes with plakophillin-2 knock-down, suggesting ARVC-associated changes in ion currents. The aim of this study was to define the cellular electrical phenotype and to assess the effect of Wnt pathway activation in a zebrafish (ZF) model of ARVC. We generated an AVRC model in ZF by cardiac-specific expression of the 2057del2 mutation in human plakoglobin (implicated in Naxos disease). Ventricular cardiomyocytes were cultured from Naxos (NX) and control heartsisolated at 21-56 days post fertilization (dpf). To activate the canonical Wnt pathway, ZF embryos were incubated at 1 dpf in a specific glycogen synthase kinase-3β inhibitor for 6 days. Action potentials (APs) and INa were recorded from single cells by whole-cell current- and voltage-clamp techniques. In myocytes from NX (vs. control), the maximal upstroke velocity of the AP, dV/dt_max, was reduced (8±1 V/s; n=8 vs. 22±3 V/s; n=8; p <0.001; mean±S.E.), AP duration (APD80) was prolonged (380±38ms; n=8 vs. 192±8ms; n=14; p <0.001), and resting membrane potential (RMP) was more positive (-67±2mV; n=8 vs. -78±1mV; n=16; p<0.001). Accordingly, peak INa density in NX myocytes (vs. control) was reduced (34±4pA/pF; n=8 vs. 196±34pA/pF; n=11; p<0.001). Activation of Wnt signaling resulted in a significant rescue of the action potential phenotype (dV/dt_max to 65% of control, APD80 to 94% of control, and RMP to 103% of control). Peak INa density recovered significantly to 86% of control. Mutant plakoglobin causes significant action potential remodeling and reduction of inward sodium current. This electrical phenotype is almost totally reversed by activation of canonical Wnt signaling. These findings directly link a mutation known to cause human disease to potentially arrhythmogenic changes in cellular electrophysiology, and implicate depressed Wnt signaling in the ARVC-associated cellular electrical phenotype.
- © 2012 by American Heart Association, Inc.