Comparison among the mouse lines studied with respect to the presence of cell cycle events (PCNA), tau-phosphorylation (AT8), and beta-amyloid plaque deposition (6E10) in the locus coeruleus. (a) Sagittal section of a wild-type mouse brain indicating the approximate location of the locus coeruleus. (b) PCNA-positive neurons are illustrated by their appearance in this representative section from the APP8.9 mouse model. (c) Minor PCNA immunostaining is seen in wild-type mice as illustrated in this representative micrograph. (d) Quantification of the extent of immunostaining for the cell cycle, phospho-tau, and beta-amyloid plaques in the five transgenic models plus wild type.