FGF20 and Parkinson disease: During development (both in vivo and in vitro) and in a genetic mouse model of PD (the heterozygous En1 mouse, [247]), this is at least partly due to the downstream induction or maintenance, respectively, of a WNT1/β-catenin-driven neuroprotective gene cascade comprising the TFs Lef1, Lmx1a, and Pitx3, and the neurotrophic factors Bdnf, Fgf20, and Dkk3 [184,246,248,249,250] (Figure 2).