Strain-specific aging gene-expression profiles. (a) Heat-map view of differentially expressed genes between 3- and 16-month-old S8, S10, SR1 and B6J hippocampus. Fold change of old relative to young hippocampus is numerically indicated within each box. Bright red (increase in expression level) and bright green (decrease in expression level) indicate genes that met the most stringent criteria for an expression-level change, including an average WSRR p < 0.01. A gene is colored orange or light green if its expression increased or decreased with an average WSRR p < 0.05. Box 1, genes changed in common with three or more strains; box 2, genes changed in only two strains; box 3, genes with changes unique to a single strain; and box 4, genes with inconsistent patterns of change. (b) Heat-map view of differentially expressed genes between 3-month-old and 16-month-old S8, S10, SR1 and B6J retinas. The analysis was performed as described for the hippocampus.