Cardiomyocyte phenotype and mechanotransduction in Filamin C gene variants causing
arrhythmogenic cardiomyopathy
Project Summary
For over two decades, our laboratories have investigated the genetic basis of cardiomyopathies, heart muscle
diseases that are a major cause of morbidity and mortality in the world. Recently, we discovered a novel
cardiomyopathy disease gene, filamin C (FLNC), and noted that truncating loss-of-function variants (FLNCtv)
in FLNC lead to arrhythmogenic cardiomyopathy (ACM), characterized by a high risk of life-threatening
ventricular arrhythmias and progression to heart failure. However, FLNC function is still poorly understood and
significant knowledge gaps preclude therapeutic development. Notably, (i) the cellular localization and
interactions of FLNC, in particular at the cell-cell junction, are incompletely resolved, (ii) the spectrum of
molecular networks involved in filaminopathies is largely unknown, (iii) the biomechanical properties of
cardiomyocytes with mutant FLNC are also unknown, (iv) the role of FLNC in sarcomere function is not
completely elucidated, and (v) finally, the mechanism by which FLNC variants cause different clinical phenotypes
is unknown. This proposal aims to determine mechanisms of myocardial failure and cardiac arrhythmia
in FLNCtv. Our overarching hypothesis is that FLNCtv perturb mechanotransduction machinery due to
disruption of the sarcomeric cytoskeleton, resulting in stress signaling pathway activation (integrins/hippo
pathway) which in turn triggers fibrogenesis and adipogenesis, ultimately providing the substrate for arrhythmia.
To address these gaps, we have generated human induced pluripotent stem cell-derived cardiomyocytes
(hiPSC-CMs) from FLNCtv patients and from CRISPR/Cas9-edited lines, collected frozen explanted hearts from
FLNCtv patients, and gathered a multidisciplinary research team experienced in experimental modeling of
cardiomyopathies. Based on a series of proof-of-concept experiments and preliminary data, we propose three
Specific Aims: Aim 1. Determine the phenotype and mechanisms of functional impairment and electrical
dysfunction in FLNCtv. We will determine the mechanisms of structural and functional alterations, changes in
electrophysiological function, and dysregulation of the interactome at the sarcomere-cytoskeletal-desmosomal
interface in hiPSC-CMs. Aim 2. Identify the mechanisms of altered biomechanics in FLNCtv human hearts and
hiPSC-CMs. We will determine the mechanisms of altered biomechanics by single cell spectroscopy and
myofibrillar mechanics of mutant FLNC hiPSC-CMs and explanted hearts of FLNCtv patients. Aim 3. Define the
mechanism of gene expression dysregulation in FLNCtv cardiomyopathy. Using cardiac tissue from FLNCtv
patients and FLNC hiPSC-CM models, we will assess role of altered mechanosignaling (Hippo/YAP, TGFß,
Wnt), discover novel transcriptional changes in FLNCtv heart tissue and hiPSC-CMs models, and provide the
mechanistic link with structural, contractile and electrophysiological alterations. The elucidation of molecular
networks activated in FLNCtv will provide the mechanistic link with the structural, contractile and
electrophysiological alterations, and lay the foundation for targeted rescue experiments.
