Fig. 4.

Age course of genes altered with aging.A, Chronological aging patterns for the mean expression values of all genes in the five representative functional categories containing the most ACRGs downregulated with aging (Table 1A, on-line Table 3). The expression of each gene was standardized (see Materials and Methods) before category mean values were calculated. Additionally, ACRGs were classified on the basis of the two age points between which 75% of the expression change occurred. Note that most categories of downregulated ACRGs exhibited ≥75% mean change by the mid-aged point (Yng to Mid), tending to level off between the mid-aged and aged groups. However, many downregulated genes also showed a more monotonic pattern (Yng to Age). No category showed a predominantly mid to aged pattern of change. Pie chart inset: Relative distribution of chronological patterns of change for all individual downregulated ACRGs. B, Chronological aging patterns for the mean expression changes of all genes in the five largest functional categories of upregulated ACRGs (Table 1B, on-line Table 4). Calculations and nomenclature as in Figure 4A. Note that in comparison with downregulated genes (A), more upregulated genes (B) exhibited continuing change between mid life and late life (e.g., a monotonic pattern) (pie chart insets).