Abstract 20776: Desmosomal Gene Mutations Perturb Myocardial Differentiation Through Complex Effects On Wnt Signaling
Introduction: Mutations in desmosomal protein genes cause Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC). Prior work has raised inhibition of canonical Wnt signaling as a potential disease mechanism, but the precise pathogenesis remains unclear.
Methods: We tested multiple desmosomal protein gene mutants (Desmocollin (Dsc), Plakoglobin (Pg) and Plakophilin (PKP)) in a validated zebrafish ARVC model. Truncation mutants were recapitulated with antisense morpholino oligos (MO) and we modeled missense mutations in cardiac transgenesis. We assessed the downstream effects of desmosomal mutants on electrophysiology, fractional shortening and canonical and non-canonical Wnt signaling pathways.
Results and Conclusions: Each of the ARVC models demonstrated a dose-dependent bradycardia, contractile dysfunction and perturbed cardiomyocyte differentiation. Heart rate is presented as a linear index of mutant effect, but similar results were seen on contractility and differentiation. Activation of Wnt/beta-catenin signaling using a known lef/tcf activator zebrafish mutant (lik), did not rescue desmosomal mutants, but rather led to synergistic interaction (WT 119±8, n=149; Lik 123±10, n=42; WT+DscMO 107±11, n=69; Lik+DscMO 96±11, n=65; WT+PgMO 108±9, n=60; Lik+PgMO 95±11, n=81; WT+PKPMO 105±11, n=43; Lik+PKPMO 90±16, n=63) (BPM+SD, all p<0.05). Synergistic effects were also observed with the GSK3 inhibitor BIO. These data suggest any Wnt/beta-catenin pathway inhibition in ARVC must occur downstream of beta-catenin or via other pathways. Interestingly, we also observed synergy between ARVC-related mutants and Wnt11 null alleles (WT 119±8, n=149; Wnt11MO 113±9, n=109; WT+DscMO 111±9, n=121; Wnt11MO+DscMO 104±9, n=51; WT+PgMO 108±8, n=101; Wnt11MO+PgMO 89±18, n=22; WT+PKPMO 104±14, n=91; Wnt11MO+PKPMO 81±20, n=31) (BPM+SD, all p<0.05) supporting a parallel role for non-canonical Wnt signaling in ARVC. Together with effects on contractility and differentiation these data define multiple Wnt effectors in the pathogenesis of ARVC. The transgenic models generated will allow scalable genetic or chemical screens for modifiers of proarrhythmia pathways.
- © 2010 by American Heart Association, Inc.