SHH and Parkinson disease: Remarkably, germline and especially adult cKO mouse mutants for several of the signaling and TFs discussed in section 3 (Shh, Tgfb/Bmp, Wnt/b-catenin, En1/2, Foxa1/2, Lmx1a/b, Nurr1, Pitx3, and Sox6) display an adult-onset and progressive neurodegenerative process that resembles at least some of the early neuropathological features observed in human PD patients.