Cytoneme-mediated transport of active Wnt5b/Ror2 complexes in zebrafish gastrulation

Abstract

Chemical signaling is the primary means by which cells communicate in the embryo. The underlying principle refers to a group of ligand-producing cells and a group of cells that respond to this signal because they express the appropriate receptors. In the zebrafish embryo, Wnt5b binds to the receptor Ror2 to trigger the Wnt/Planar Cell Polarity (Wnt/PCP) signaling pathway to regulate tissue polarity and cell migration. However, it is still unclear how this lipophilic ligand is transported from the source cells through the aqueous extracellular space to the target tissue. Here we show that Wnt5b, together with Ror2, is loaded on long protrusions. The active Wnt5b/Ror2 complexes are handed over from these cytonemes to the receiving cell to trigger Wnt/PCP signaling, regardless of whether the cell expresses functional receptors. On the tissue level, we show that cytoneme-dependent spreading of active Wnt5b/Ror2 affects convergence and extension in the zebrafish gastrula.