SLC6A3 and Parkinsonism: In fact, some studies showed a reduced DAT binding in the striatum of non-manifest G2019S carriers [127–130] whereas the analysis of the large cohort of Parkinson’s Progression Markers Initiative (PPMI) patients [123,131] revealed that non-manifest G2019S carriers do not show difference in DAT tracer binding with respect to healthy controls [131].