Abstract 13146: Cardioprotective Effects of Mtss1 Reduction in Dilated Cardiomyopathy

Introduction: MTSS1 is an I-BAR protein that interacts with the actin cytoskeleton and the cell membrane and is speculated to play a role in cell motility, tumor metastasis, and cardiogenesis. Enhancer variants that reduce the expression of MTSS1 in the human left ventricle have been associated with cardioprotective traits in genome-wide association studies. However, the effect of MTSS1 downregulation on the development of heart disease has not been studied in experimental models. Here we tested the hypothesis that reduction of MTSS1 protects against dilated cardiomyopathy (DCM) in vitro and in vivo. Methods: We used CRISPR-Cas9 to knock out MTSS1 in induced pluripotent stem cells (iPSCs) harboring pathogenic variants from patients with severe DCM. DCM iPSC lines with and without MTSS1 were then differentiated into cardiomyocytes and phenotyped in vitro. A DCM mouse model containing a TPM1 D230N transgene was crossed with a mouse model heterozygous for Mtss1 knockout. Progeny from this F1 cross were assessed for differences in cardiac structure and function via echocardiography. Results: MTSS1 deletion restored the beta-adrenergic response in DCM iPSC cardiomyocytes. In parallel, Mtss1 deletion partially rescued DCM-associated phenotypes including left ventricular dilation and reduced ejection fraction in mice. Conclusions: Our initial results suggest a causal link between MTSS1 reduction and cardioprotection in DCM. Inhibiting cardiac MTSS1 may hold therapeutic potential for DCM, though the cellular mechanisms through which MTSS1 affects cardiac phenotypes remain under investigation.