Ligand for members of the frizzled family of seven transmembrane receptors (Probable). Plays an important role in embryonic development (PubMed:8541205). Caudal forebrain and neural keel, the floor plate, the gill slit and the developing pronephros. First detected at the end of gastrulation in the anterior neuroectoderm. Expression increases in the developing brain during somitogenesis but has gone by 36 hours. Expression in the floor plate begins at the 10 somite stage and persists at 72 hours. Palmitoleoylation is required for efficient binding to frizzled receptors. Depalmitoleoylation leads to Wnt signaling pathway inhibition. Belongs to the Wnt family.