Autonomous and Non-autonomous Defects Underlie Hypertrophic Cardiomyopathy in BRAF-Mutant hiPSC-Derived Cardiomyocytes

• Main Authors: Rebecca Josowitz, Sonia Mulero-Navarro, Nelson A. Rodriguez, Christine Falce, Ninette Cohen, Erik M. Ullian, Lauren A. Weiss, Katherine A. Rauen, Eric A. Sobie, Bruce D. Gelb
• Format: Article
• Language: English
• Published: Elsevier 2016-09-01
• Series: Stem Cell Reports
• Online Access: http://www.sciencedirect.com/science/article/pii/S2213671116301424

Germline mutations in BRAF cause cardio-facio-cutaneous syndrome (CFCS), whereby 40% of patients develop hypertrophic cardiomyopathy (HCM). As the role of the RAS/MAPK pathway in HCM pathogenesis is unclear, we generated a human induced pluripotent stem cell (hiPSC) model for CFCS from three patients with activating BRAF mutations. By cell sorting for SIRPα and CD90, we generated a method to examine hiPSC-derived cell type-specific phenotypes and cellular interactions underpinning HCM. BRAF-mutant SIRPα+/CD90− cardiomyocytes displayed cellular hypertrophy, pro-hypertrophic gene expression, and intrinsic calcium-handling defects. BRAF-mutant SIRPα−/CD90+ cells, which were fibroblast-like, exhibited a pro-fibrotic phenotype and partially modulated cardiomyocyte hypertrophy through transforming growth factor β (TGFβ) paracrine signaling. Inhibition of TGFβ or RAS/MAPK signaling rescued the hypertrophic phenotype. Thus, cell autonomous and non-autonomous defects underlie HCM due to BRAF mutations. TGFβ inhibition may be a useful therapeutic option for patients with HCM due to RASopathies or other etiologies.