Liver from old Polμ^−/− mice shows fewer aging-related features than liver from age-matched wt controls.

<p>(<b>A</b>) Involvement of autophagy activity in the Polμ^−/− lifespan extension phenotype. Heart samples from old (18–25 m; o) and young (8–12 w; y) Polμ^−/− (gray bars) and wt mice (black bars) were analyzed by qRT-PCR for the expression of a panel of genes essential for autophagy (Atg2l, Atg5l, Atg7l and Map11c3b). Results, expressed as 2∧–(DCT), show mean values ± SD (n = 5). (<b>B</b>) Protein carbonyls (Carb) and peroxided lipids (PeroxL; thiobarbituric acid reactive substances, TBARS), as macromolecular oxidative damage, were determined (nmol/mg prot), as described in the supporting information, in perfused liver of old (>20 months) Polμ^−/− (black bars) and wt gray bars) mice Results are mean values ± SD (n = 3). (<b>C</b>) Heat map of microarray expression data for livers from adult (14 m) wt and Polμ^−/− mice. The relative gene expression scale is shown, with normalized scores ranging from 0 to 20. Gene cluster and case cluster dendrograms are plotted to the top and left. (<b>D</b>) Microarray data validation. mRNA levels were determined by TaqMan RT-PCR in livers from adult wt (black) and Polμ^−/− mice (gray). Each determination was performed in triplicate and normalized to β-actin expression. Data are the means ± SEM of 4 samples per genotype, represented relative to expression in age-matched wt liver. (<b>E</b>) Scheme of the interaction network among apoptosis-related or p53-inducible genes downregulated in old Polμ^−/− liver.