Ligand for members of the frizzled family of seven transmembrane receptors (Probable). Functions in the canonical Wnt/beta-catenin signaling pathway (PubMed:19686689). Plays a redundant role in embryonic lung development (PubMed:19686689). 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 FZD4 and FZD5 (By similarity). Detected at the dorsal midline at the level of the diencephalon and mesencephalon at 9.5 dpc. Detected at the level of the optic and otic vesicles at 9.5 dpc (PubMed:9545553). Detected in the lateral plate mesoderm surrounding the ventral aspect of the anterior foregut at 9.5 dpc (PubMed:19686689). Detected in the mesothelium encasing the lung, and at lower levels in the distal mesenchyme from 12.5 dpc to 14.5 dpc (PubMed:19686689). Palmitoleoylation is required for efficient binding to frizzled receptors. Depalmitoleoylation leads to Wnt signaling pathway inhibition. No visible phenotype at birth (PubMed:19686689). Combined disruption of Wnt2 and Wnt2b leads to lung agenesis (PubMed:19686689). Belongs to the Wnt family.