Ligand for members of the frizzled family of seven transmembrane receptors (Probable). Functions in the canonical Wnt signaling pathway that results in activation of transcription factors of the TCF/LEF family (By similarity). Required for normal gastrulation, formation of the primitive streak, and for the formation of the mesoderm during early embryogenesis (PubMed:10431240). Required for normal formation of the apical ectodermal ridge and for normal embryonic limb development (PubMed:12569130). Forms a soluble 1:1 complex with AFM; this prevents oligomerization and is required for prolonged biological activity. The complex with AFM may represent the physiological form in body fluids (By similarity). Interacts with PORCN (PubMed:10866835). Interacts with WLS (PubMed:19841259). Detected at low levels in adult brain (PubMed:2162045). Dorsal portion of the neural tube, dorsal ectoderm, the branchial arches, and the limb buds. Detected at 6.25 to 7.5 dpc in primitive streak, proximal epiblast, visceral endoderm and at the junction between the embryonic and extraembryonic ectoderm, with higher levels in the posterior region (PubMed:10431240, PubMed:19841259). Detected in the ectoderm at forelimb buds at 9.5 dpc (PubMed:12569130). Detected in all outgrowing limbs and in ectoderm flanking the limbs at least till 11.5 dpc (PubMed:12569130). Highly expressed in embryos at 11.5 and 12.5 dpc, with very low expression levels before and after this period (PubMed:2162045). Palmitoleoylation is required for efficient binding to frizzled receptors. Depalmitoleoylation leads to Wnt signaling pathway inhibition. Some mouse mammary tumors induced by mouse mammary tumor virus (MMTV) contain a provirus integrated into a host cell region which has been named Wnt3. Belongs to the Wnt family.