The type III TGFβ receptor is required for hyaluronan‐mediated epicardial invasive cell motility (542.5)

Abstract

The epicardium originates from the proepicardial organ (PEO). Both the PEO and epicardium require directed cell‐motility to cover the heart and instruct epicardially derived cells for coronary vasculature formation. The type III transforming growth factor‐beta receptor (Tgfbr3) is required for epicardial cell invasion and development of coronary vasculature in vivo. Utilizing a primary epicardial cell line derived from Tgfbr3(+/+) and Tgfbr3(‐/‐) e13.5 mouse embryos , we show that Tgfbr3(‐/‐) epicardial cells are 34.4% deficient in 2D migration relative to wild type. Furthermore, we show that high‐molecular weight Hyaluronan (HMWHA) drives 3D cellular invasion in wild type epicardial cells, but not Tgfbr3(‐/‐) epicardial cells. We show Src kinase is required for HMWHA stimulated filamentous actin (f‐actin) polymerization in wild‐epicardial cells. Furthermore, HMWHA stimulates Y416Src phosphorylation in wild type, but Src is not activated in Tgfbr3(‐/‐) epicardial cells. RhoA and Rac1 GTPase are downstream of Src kinase, and directly upstream of f‐actin polymerization; HMWHA robustly induces RhoA and Rac1 GTP binding and activity in wild type, but not Tgfbr3(‐/‐) epicardial cells. This deficit in RhoA and Rac1 activation results in reduced formation of f‐actin stress fibers in HMWHA stimulated Tgfbr3(‐/‐) epicardial cells. Taken together, we demonstrate that the type III TGFβ receptor is required for activation of basic cell motility pathways stimulated by Hyaluronan that are required for proper coronary vasculature formation.Grant Funding Source: NIH ES 04940; ES06694; SWEHSC P30ES006694