Fig. 6.

Pan-nuclear γH2AX signal is selectively observed in NCCR-App^NLF animals. A) immunofluorescence staining for γH2AX, a marker for DNA damage response, in cortex shows pan-nuclear labeling that is restricted to NCCR-App^NLF animals at 9, 12, and 18 months of age (arrows, primary somatosensory areas shown). B) Magnified image showing γH2AX labeled NeuN+and NeuN- cells (arrowhead and arrow, respectively). C) Quantification of pan-nuclear γH2AX labeling shows that pan-nuclear γH2AX signal is present in both NeuN+and NeuN- cells in NCCR-App^NLF animal-specific manner. Pan-nuclear γH2AX labeling was observed more frequently in NeuN+cells compared NeuN- cells. N = 2 animals per genotype/age were evaluated. Four matched coronal sections were measured across the animals. Each data point represents a measure from each section. D) SV40T expression modulates pan-nuclear γH2AX signal. Representative images of SV40T (red), γH2AX (green), and DAPI (blue) staining in CA1 of NCCR mice. Panel “a” shows 3-month-old NCCR mice maintained on regular diet for 2 months displaying increased pan-nuclear γH2AX staining. When NCCR mice are put back on dox diet to halt SV40T expression (panel “b”, pulsed) or continuously maintained on dox diet thus never having expressed SV40T (panel “c”, always on dox), no pan-nuclear γH2AX labeling is detected, demonstrating its modulation by SV40T expression. TAg (TRE-SV40T) animals were used as controls. A complex relationship between neuronal SV40T expression and pan-nuclear γH2AX expression is demonstrated by the staining data. In addition to co-labeling of SV40T and γH2AX (Fig. 6D,a; arrowhead), there are instances of γH2AX labeling in the absence of SV40T (Fig. 6D,a; asterisks) and SV40T labeling in the absence of γH2AX signal (Fig. 6D,a; arrow). Therefore, the effect of neuronal SV40T expression on pan-nuclear γH2AX signal can be non-cell autonomous, but at the same time, the cell-autonomous response to SV40T expression can also be variable. Scale bar 20μm.