<p>(A) The relative expression of senescence-associated genes in cortices from young and old brains was analyzed by Q-PCR. Results are Mean ± s.d. (n = 3; *<i>P</i><0.05; **<i>P</i><0.01). The dashed line represents the basal gene expression level measured in young mice. (B) The relative expression of antioxidant genes in cortices from young and old brains, and from P25 <i>Bmi1<sup>−/−</sup></i> and WT mice was analyzed by Q-PCR. The dashed line represents the basal gene expression level measured in young compared to old and to WT compared to <i>Bmi1<sup>−/−</sup></i> mice. Results are Mean ± s.d. (n = 3; *<i>P</i><0.05; **<i>P</i><0.01). (C) Coronal sections from the cerebral cortex of young and old mice, and of P25 WT and <i>Bmi1<sup>−/−</sup></i> mice were labeled with antibodies against 8-oxo-guanine (8-OG; brown) and GFAP (pink). Note the increase in 8-oxo-guanine labeling in neurons from old and <i>Bmi1<sup>−/−</sup></i> mice compared to respective controls. Scale bars; 50 µm. (D) ChIP analysis of young and old brains revealing accumulation of p53 and heterochromatin marks (histone H3 K27<sup>me2</sup> or H3 k9<sup>me2</sup>) at the <i>xCT</i>, <i>Sod1</i> and <i>Sod2</i> promoters in old brains. Antibodies against acetylated histone H4 and IgG were used as control. The <i>β-major</i> promoter region of <i>globin</i> was use as negative control. Results are Mean ± s.d. (n = 3; *<i>P</i><0.05).</p
