Selective activation of FZD2 and FZD7 reveals non-redundant function during mesoderm differentiation.

Abstract

During gastrulation, Wnt-β-catenin signaling dictates lineage bifurcation generating different mesoderm cell types. However, the specific role of Wnt receptors in mesoderm specification remains elusive. Using selective Frizzled (FZD) and LRP5/6 antibody-based agonists, we examined FZD receptors' function during directed mesoderm differentiation of human pluripotent stem cells (hPSCs). We found that FZD2 and FZD7 receptors are expressed at the membrane of hPSCs and that their activation triggers β-catenin signaling with different kinetics, thereby influencing mesoderm patterning choices. Specifically, FZD7 activation enhances both paraxial and lateral mesoderm differentiation, whereas FZD2 activation favors paraxial mesoderm. Mechanistically, FZD2 activation promotes sustained Wnt-β-catenin levels, guiding hPSCs differentiation toward paraxial mesoderm, while blocking lateral mesoderm. In contrast, FZD7 activation kinetics display similar initial activation but more dampening of β-catenin signaling, permitting lateral mesoderm induction in addition to paraxial mesoderm specification. Our findings reveal non-redundant roles for FZD2 and FZD7 in mesoderm specification, offering leverage for precise directed differentiation outcomes.