LUMA in cardiac development and function

Elucidating arrhythmogenic right ventricular cardiomyopathy with stem cells

Human stems cells have sparked many novel strategies for treating heart disease and for elucidating their underlying mechanisms. For example, arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited heart muscle disorder that is associated with fatal arrhythmias often occurring in healthy young adults. Fibro-fatty infiltrate, a clinical hallmark, progresses with the disease and can develop across both ventricles. Pathogenic variants in genes have been identified, with most being responsible for encoding cardiac desmosome proteins that reside at myocyte boundaries that are critical for cell-to-cell coupling. Despite some understanding of the molecular signaling mechanisms associated with ARVC mutations, their relationship with arrhythmogenesis is complex and not well understood for a monogenetic disorder. This review article focuses on arrhythmia mechanisms in ARVC based on clinical and animal studies and their relationship with disease causing variants. We also discuss the ways in which stem cells can be leveraged to improve our understanding of the role cardiac myocytes, nonmyocytes, metabolic signals, and inflammatory mediators play in an early onset disease such as ARVC.

Systems Genetics Analysis Defines Importance Of TMEM43/LUMA For Cardiac And Metabolic Related Pathways

Broad cellular functions and diseases including muscular dystrophy, arrhythmogenic right ventricular cardiomyopathy (ARVC5) and cancer are associated with transmembrane protein43 (TMEM43/LUMA). The study aimed to investigate biological roles of TMEM43 through genetic regulation, gene pathways and gene networks, candidate interacting genes, and up- or downstream regulators. Cardiac transcriptomes from 40 strains of recombinant inbred BXD mice and two parental strains representing murine genetic reference population (GRP) were applied for genetic correlation, functional enrichment, and coexpression network analysis using systems genetics approach. The results were validated in a newly created knock-in Tmem43-S358L mutation mouse model (Tmem43^S358L) that displayed signs of cardiac dysfunction, resembling ARVC5 phenotype seen in humans. We found high Tmem43 levels among BXDs with broad variability in expression. Expression of Tmem43 highly negatively correlated with heart mass and heart rate among BXDs, whereas levels of Tmem43 highly positively correlated with plasma high-density lipoproteins (HDL). Through finding differentially expressed genes (DEGs) between Tmem43^S358L mutant and wild-type (Tmem43^WT) lines, 18 pathways (out of 42 found in BXDs GRP) that are involved in ARVC, hypertrophic cardiomyopathy, dilated cardiomyopathy, nonalcoholic fatty liver disease, Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease were verified. We further constructed Tmem43-mediated gene network, in which Ctnna1, Adcy6, Gnas, Ndufs6, and Uqcrc2 were significantly altered in Tmem43^S358L mice versus Tmem43^WT controls. Our study defined the importance of Tmem43 for cardiac- and metabolism-related pathways, suggesting that cardiovascular disease-relevant risk factors may also increase risk of metabolic and neurodegenerative diseases via TMEM43-mediated pathways.