Local Fluid Shear Stress Operates a Molecular Switch to Drive Fetal Semilunar Valve Extension

While much is known about the genetic regulation of early valvular morphogenesis, mechanisms governing fetal valvular growth and remodeling remain unclear. Hemodynamic forces strongly influence morphogenesis, but it is unknown whether or how they interact with valvulogenic signaling programs. Side‐specific activity of valvulogenic programs motivates the hypothesis that shear stress pattern‐specific endocardial signaling controls the elongation of leaflets.