Wnt signaling during the central nervous system and mesodiencephalic dopaminergic neuron development. (A) Wnt signaling is critical in embryonic development, controlling diverse processes, such as cell proliferation and cell polarity. It is involved during early central nervous system (CNS) development in gastrulation, early pattern formation, morphogenesis and precursor proliferation, in late CNS development in processes such as neuronal differentiation and migration, and in adult organisms, where it plays a central role in the maintenance of tissue homeostasis and stem cell regulation. Wnt signaling controls diverse processes, such as cell proliferation, cell polarity, cell death and cell fate specification Wnts can also function as morphogens in both short- and long-range signaling, modulating target cells in a dose- and distance-dependent manner. (B) Wnt signaling is involved in mesodiencephalic dopaminergic (mdDA) neuron development from early on, where it is involved in morphogenesis, and later on as well in mdDA differentiation.