Given that PSP, PD, and FTD are neuropathologically characterized by degeneration in the midbrain, cerebellum, and (to a lesser extent) neocortical regions1,2,61, our findings may suggest that subtle alterations of CXCR4 and MAPT may predispose to regionally specific brain degeneration in later life. The gene discussed is CXCR4; the disease is Parkinson disease.