Deciphering the mechanisms of the arrhythmogenic R735X

Abstract

Ventricular arrhythmias (VA) appear during the concealed phase of arrhythmogenic cardiomyopathy (AC). This VA can lead to sudden cardiac death, being in many cases, the first symptom of the disease. Mutations on the desmosomal gene Plakophilin-­‐2 (PKP2) have been described as the most prevalent genetic causes of AC. However, the molecular mechanism underlying these early electrical changes during AC development has not been elucidated. PKP2 integrates into the connexome protein network and may lead to changes in its components. In this thesis project we have demonstrated that R735X (a PKP2 truncation associated to AC phenotype) leads to a decrease of the voltage-­‐gated sodium channel NaV1.5 at the plasma membrane of HEK293T and HL-­‐1 cells. In order to study the effect of R735X on a human context, we have developed an AC model based on human induced pluripotent stem cell-­‐derived cardiomyocytes (hiPSC-­‐CM). We have study the role of R735X in hiPSC-­‐CM electrophysiology by comparing electrical features of AC hiPSC-­‐CMs (expressing R735X) with its hiPSC-­‐CM isogenic control. Patch-­‐clamp measurements indicate that R735X leads to a decrease in the fast depolarizing sodium current generated by NaV1.5 channel in hiPSC-­‐CMs. Optical mapping showed an elongation of the action potential duration (APD) and a slowdown in the conduction velocity (CV) of the electrical impulse in mutant 2D hiPSC-­‐CM monolayers, inducing arrhythmogenics events. These results highlight the arrhythmogenic character of R735X protein and could explain the electrical abnormalities reported in AC patients at early stages of the disease.