Abstract 14836: Dual Dysfunction of Kir2.1 at the Sarcolemma and the Sarcoplasmic Reticulum Underlies Arrhythmogenesis in a Mouse Model of the Andersen-Tawil Syndrome Type 1

Abstract

Introduction: Andersen-Tawil syndrome type 1 (ATS1) is associated with fatal cardiac arrhythmias. However, the underlying mechanisms are poorly understood. Hypothesis: Cardiac-specific expression of trafficking deficient Kir2.1 channels in mice in-vivo recapitulates the cardiac electrical phenotype of ATS1 and investigate the underlying mechanisms. Methods: We generated a new mouse model of ATS1 by a single i.v. injection of cardiac specific adeno-associated viral (AAV) transduction with Kir2.1 Δ314-315 , which recapitulated the ATS1 ECG phenotype without modifying ventricular function. The animal and cellular, structural and functional analyses were carried out by ECG, intracardiac stimulation, patch-clamping, membrane fractionation, western blot, immunolocalization and live calcium imaging. Results: AAV-Kir2.1 Δ314-315 mice were significantly more sensitive to flecainide than control, increasing the PR and QRS intervals over time. Kir2.1 Δ314-315 mice had increased vulnerability to cardiac fibrillation. Patch-clamping in ventricular cardiomyocytes from Kir2.1 Δ314-315 mice demonstrated significantly reduced I K1 and I Na , depolarized resting membrane potential and prolonged action potential. Immunolocalization in control mice revealed two bands of Kir2.1 staining, one colocalizing with Na V 1.5 and AP1 near the Z disk, the other near the H zone. Membrane fractionation and western blot experiments demonstrated two distinct levels of Kir2.1 protein expression, one at the sarcolemmal fraction together with Na V 1.5 and the other at the sarcoplasmi creticulum (SR). Kir2.1 Δ314-315 cardiomyocytes showed disruption of the Kir2.1-Nav1.5 channelosome at the sarcolemma, indicating dysfunctional trafficking o fboth channels. In addition, the SR Kir2.1 was disrupted and calcium transient dynamics were altered, resulting in frequent abnormal spontaneous calcium release events, and revealing an excitation-contraction coupling defect. Conclusions: Cardiac-specific AAV transduction with Kir2.1 Δ314-315 in mice recapitulates the ATS1 phenotype by disrupting localization and function of Kir2.1at the SR, and the Kir2.1-Na V 1.5 channelosome at the sarcolemma, revealing anovel dual mechanism of arrhythmogenesis.