Figure 3

K-means cluster analysis of differentially expressed genes. Differentially expressed genes were clustered into 30 k-means clusters (JMP Genomics, SAS 9.2) as this is the lowest number of clusters which allows a minimum correlation coefficient of R = 0.7 between any one expression profile and its other cluster members. Male and female data were allowed to cluster independently between the 30 groups such that male and female data might cluster to separate groups for a given gene. The x- and y-axes represent age and relative fold change, respectively. Color is arbitrary and does not represent sex. These data illustrate the various biological patterns of liver expression which exist during pre-pubertal, pubertal, early adult and aged rat life stages.