Figure 1.

Relationship between gene expression level and protein conservation. Examples of gene expression level versus protein conservation metric correlations (a) for a 20‐year‐old human and (b) for a 91‐year‐old human, in the postcentral gyrus of the brain (data from Berchtold et al., 2008). The analysis includes only age‐related genes detected in this dataset (at q < 0.10). Each point represents a gene (n = 1688). The x‐axis shows the protein sequence conservation metric, where more positive values reflect higher conservation across mammals. The y‐axis shows log2‐transformed gene expression levels. The expression–conservation ρ values (ρEC) are indicated in the inset. To improve visualization, we removed genes with disproportionately low conservation metrics (n = 3) in panels (a) and (b). Note that our correlation statistic, Spearman, is not affected by such potential outliers. (c) Age‐dependent change in expression–conservation ρ values in the human postcentral gyrus, based on age‐related genes in the same dataset as panels (a) and (b). The y‐axis shows expression–conservation ρ values (ρEC) calculated for each individual in this dataset (n = 39). The x‐axis shows the ages of individuals. The ρ value between age and expression–conservation correlation (ρAρEC) is indicated in the inset.