Compelling evidence for a deregulated WNT/b-catenin signaling pathway in PD-related mDA neurodegeneration was also provided by the analyses of PARK gene-encoded proteins, especially LRRK2, the parkin E3 ubiquitin protein ligase (PRKN/PARK2) and the VPS35 retromer complex component (VPS35/PARK17; Berwick and Harvey, 2014). Here, LRRK2 is linked to Parkinson disease.