Finally, a decrease in the number of proliferating cell nuclear antigen (PCNA) positive cells (a marker of cell proliferation) in SVZ and a reduction in the number of nestin- and βIII-tubulin-positive cells in the DG of the hippocampus have also been found in postmortem tissue from PD patients, presumably as a consequence of dopaminergic denervation of these neurogenic regions [108], providing further evidence of altered hippocampal neurogenesis in the human PD brain. This evidence concerns the gene PCNA and Parkinson disease.