Ligand for members of the frizzled family of seven transmembrane receptors (Probable). Acts in the canonical Wnt signaling pathway by promoting beta-catenin-dependent transcriptional activation (PubMed:23499309, PubMed:23656646, PubMed:26902720, PubMed:28528193). In some developmental processes, is also a ligand for the coreceptor RYK, thus triggering Wnt signaling (By similarity). Plays an essential role in the development of the embryonic brain and central nervous system (CNS) (By similarity). Has a role in osteoblast function, bone development and bone homeostasis (PubMed:23499309, PubMed:23656646). {ECO:0000250|UniProtKB:P04426, ECO:0000269|PubMed:23499309, ECO:0000269|PubMed:23656646, ECO:0000269|PubMed:26902720, ECO:0000269|PubMed:28528193, ECO:0000305}. This is the function of WNT1 (Wnt family member 1, ENSG00000125084).