Wnt signaling in human development: beta-catenin nuclear translocation in fetal lung, kidney, placenta, capillaries, adrenal, and cartilage.

The Wnt signaling pathway is involved in both normal development and tumorigenesis. Activation of the pathway results in stabilization and nuclear translocation of beta-catenin protein. Nuclear localization of beta-catenin has been used to identify tumors in which mutations in APC or beta-catenin activate Wnt signaling. We analyzed the subcellular localization of beta-catenin immunohistochemically in human fetal and postnatal tissues to identify activation of Wnt signaling during development. Nuclear beta-catenin is present in capillary endothelium, mesenchyme surrounding renal tubules, adrenal cortex, cartilage anlage, placental cytotrophoblast, and pulmonary acinar buds. These investigations suggest a defined role for Wnt signaling in human fetal development and provide a catalogue of non-neoplastic tissues with nuclear beta-catenin staining.