Vangl2-dependent regulation of membrane protrusions and directed migration requires a fibronectin extracellular matrix

During zebrafish gastrulation the planar cell polarity (PCP) protein Vang-like 2 (Vangl2) regulates polarization of cells engaged in directed migration. However, it is unclear whether Vangl2 influences membrane-protrusive activities in migrating gastrula cells and if these processes require the fibronectin extracellular matrix. We report that Vangl2 modulates formation and polarization of actin-rich filopodia-like and large lamellipodia-like protrusions in ectodermal cells. By contrast, disrupted Glypican4/PCP signaling affects protrusion polarity but not protrusion number or directed migration. Analysis of fluorescent fusion protein expression suggests widespread Vangl2 symmetry in migrating cells but enrichment at membrane domains with developing large protrusions compared to non-protrusive domains. We show the fibronectin extracellular matrix is essential for cell surface Vangl2 expression, membrane-protrusive activity, and directed migration. Manipulation of fibronectin protein levels rescues protrusion and directed migration phenotypes in vangl2 mutant embryos, but is not sufficient to restore PCP and convergence and extension movements. Together, our findings identify distinct roles for Vangl2 and Glypican4/PCP signaling during membrane protrusion formation and demonstrate cell-matrix interactions underlie Vangl2-dependent regulation of protrusive activities in migrating gastrula cells.