WNT1 and Parkinson disease: Here, using three different in vitro models of DA toxicity (i.e.: serum deprivation, SD, 6-OHDA and MPP+ exposure) in purified neurons and astrocyte-neuron co-culture paradigms, using pharmacological antagonism or RNA silencing along with functional studies in both intact and SN lesioned mice, we highlight an intrinsic Wnt1/Fzd-1/β-catenin tone critically contributing to the survival and protection of adult midbrain DA neurons with potential implications for drug design or drug action in PD.