E2F1 and Alzheimer disease: Regarding nuclear staining, pyramidal neurons from the hippocampus of CP-AD individuals demonstrated higher expression levels of Cdk4, cyclin D, phospho-Rb, E2F1, Cdk1, and cyclin B than did those from either P-AD or N subjects (Figure 3A, 3C, 3E, 3G, 3I, and 3K; Table 4; Figures S9–S14).