The first five principal components were associated with specific biological factors. (A) First five PCs and their associated variance. Samples were sorted by their tissue of origin (background color) and ordered by increasing age of the individual for each tissue. (B) Sample variables that correlated with the first five PC patterns. Correlations are shown in the gray boxes. Arrows connect PCs with the variables with which they are correlated. BA10, Broadmann area 10; BA20, Broadmann area 20, BA7, Broadmann area 7; PC, principal component; WB, whole blood.