Endodermal Gpc4 aids in filopodia-mediated transport of endodermal Wnts to mesoderm to facilitate morphogenesis. Cell-surface Gpc4 is required for Wnt transport from endoderm to mesoderm in zebrafish embryos. Wnt transport occurs on actin-rich signaling filopodia, and Gpc4 is required for proper filopodial morphology to effectively transport Wnts.