K-means cluster analysis of differentially expressed genes.

<p>Differentially expressed genes were clustered into 28-means clusters (JMP Genomics, SAS 9.2) as this is the lowest number of clusters which allows a minimum correlation coefficient of R = 0.6 between any one expression profile and its other cluster members. The x- and y-axes represent age in weeks and relative fold change, respectively. Cluster color is arbitrary. These data illustrate the various biological patterns of kidney expression which exist during pre-pubertal, early adult and aged rat life stages.