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 (PubMed:17488271). Regulates chick apical ectodermal ridge formation (PubMed:17488271). Required for normal embryonic mesoderm development and formation of caudal somites. Required for normal morphogenesis of the developing neural tube (By similarity). Expressed in cornea. Isoform 1 is expressed in the primitive streak, dorsal neural tube, proximal otic vesicle, the apical ectodermal ridge and the epithelium of feather buds. In the eye, the expression was observed at stage 23 in the ocular surface epithelium ventral to the corneal epithelium. Strongly expressed in the entire ocular surface at stage 26 including the corneal epithelium. Remained strongly expressed at stage 30. Palmitoleoylation is required for efficient binding to frizzled receptors (PubMed:22046319). Depalmitoleoylation leads to inhibit the Wnt signaling pathway (By similarity). Disulfide bonds have critical and distinct roles in secretion and activity. Loss of each conserved cysteine in WNT3A results in high molecular weight oxidized Wnt oligomers, which are formed through inter-Wnt disulfide bonding (By similarity). Not secreted. Belongs to the Wnt family. A palmitoylation site was proposed at Cys-77, but it was later shown that this cysteine is engaged in a disulfide bond.