Interestingly, entering the cell cycle has been linked to cell death in neurons (Herrup et al., 2004; Herrup and Yang, 2007), and, moreover, Höglinger et al. (2007) found that the pRb/E2F pathway caused neuronal cell death in a chemical model of PD, consistent with the over-representation of mitotic gene sets in dj-1−/− brains, reflecting their neurodegenerative pathology. This evidence concerns the gene RB1 and Parkinson disease.