Tuesday, 15 May 2018 | 12:00 noon
National Research Council (CNR), Institute of Genetic and Biomedical Research (IRGB) – UOS of Milan and Humanitas Clinical and Research Center, Milan, ITALY
iPSC-based models for cardiac diseases: focus on LMNA- dependent Cardiomyopathy
(Host) M. Giacca)
Mutations in LMNA gene, encoding the nuclear lamina proteinsLaminA/C, cause a group of diseases called laminopathies that,at the heart level, manifests with dilated cardiomyopathy (DCM)typically associated with various conduction system defects.LaminA/C proteins regulate many biological processes, frommaintenance of nuclear structure to mechanosensing, chromatinorganization and transcription.
However, studies so far have mainlyfocused on fibroblasts, while the pathophysiological mechanismsunderlying defective LaminA/C in cardiomyocytes (CMs) and theirconsequences in myocardial diseases remain undefined. Withthe advent of induced pluripotent stem cells (iPSC), generation ofhuman disease-specific cardiomyocytes (CMs) in vitro has becomefeasible and allows the creation of cellular models, in whichmolecular mechanisms of disease may be investigated.
In ourstudy, we generated CMs from iPSCs of patients carrying the K219Tmutation, which gives rise to DCM. Using this cellular model, weperformed a comprehensive analysis of the functional properties byelectrophysiological techniques both, at the single cells levels and ina multi-cellular setting.Results from patch-clamp highlighted majorfunctional changes in LMNA-CMs compared to CNTR (i.e. maximalupstroke velocity, action potential amplitude and overshoot),accompanied by a reduction of the peak sodium currents and adiminished conduction velocity.
Molecular studies targeting thesodium channel protein Nav1.5 and its encoding gene, SCN5A,indicated a significant reduction of both transcript and protein inLMNA-CMs; this event was associated with an increased binding toSCN5A gene promoter of LaminA/C, together with the H3K27me3and H3K9me3 repressive marks, and with a preferential localizationof SCN5A gene at the nuclear periphery in mutant cells. Altogether, our findings support an epigenetic regulatory circuitdriven by LaminA/C underlying the reduction of sodium currentsand the consequent slower conduction velocity, which potentiallyjustify for the conduction defects typically observed in patients withLMNA-cardiomyopathy.