Uncovering the transmembrane protein 43 life cycle to provide insight into arrhythmogenic right ventricular cardiomyopathy

Abstract

Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC) is an inherited heart failure featuring sudden cardiac death. ARVC type 5 is caused by an autosomal dominant mutation in the transmembrane protein 43 (TMEM43) gene (c.1073C>T, p.S358L) widespread throughout the Newfoundland population. Although this mutation is known to cause ARVC type 5, very little is known about the wild type TMEM43 protein. In order to shed light on the basic functions of TMEM43, we used CRISPR-Cas9 to genetically ablate TMEM43 in AD293 reference cells as well as human induced pluripotent stem cells (iPSCs). Cycloheximide pulse-chase experiments demonstrate that wild type TMEM43 has a relatively long half-life of more than 8 hours. Interestingly, while TMEM43 was localized to the nuclear envelope of AD293 cells, it was distributed primarily in large punctae throughout the cytoplasm of human iPSCs. Furthermore, TMEM43 may be more highly expressed in male (XY) iPSC-derived cardiomyocytes compared to female (XX) cells which could shed light on the sex differences observed in ARVC disease severity. These findings highlight some of the most basic features of the TMEM43 protein while future studies using the TMEM43 knockout cells may shed light on how TMEM43 genetic mutation causes ARVC in Newfoundland.