WNT3 is a secreted ligand that activates canonical Wnt signaling through frizzled receptor binding, leading to TCF/LEF transcription factor activation 1. During embryogenesis, WNT3 is essential for gastrulation, primitive streak formation, and mesoderm development, with particular importance for limb and apical ectodermal ridge formation 2. In postnatal tissues, WNT3 functions in stem cell maintenance and differentiation across multiple lineages. Within intestinal crypts, Paneth cells produce WNT3 as a critical niche signal supporting Lgr5+ stem cell self-renewal 3. WNT3 also regulates hindgut specification during intestinal development in concert with FGF signaling 4. During cardiac development, WNT3 expression is functionally important at embryonic and newborn stages 5. In liver regeneration, glutamate-reprogrammed macrophages activate WNT3 transcription to promote YAP1-dependent hepatocyte proliferation 6. Clinically, WNT3 dysfunction causes tetraamelia syndrome type 1. Aberrant WNT3 activation contributes to colorectal cancer pathogenesis, where p53-mediated WNT3 upregulation promotes cancer stem cell enrichment following 5-fluorouracil treatment 7.