Unsupervised hierarchical clustering of Pearson's coefficients of pairwise correlation of gene expression reveal 4 indicated clusters. Violin plots of average Z-scores of genes that belong to the four clusters derived from hierarchical clustering. The thick horizontal dashed lines in each sample set represent median; thin dashed lines represent the quartiles; polygons represent density estimates of data and extend to extreme values. Statistical tests employed were 1-sample t-test or Wilcoxon signed rank test to examine significance of differences from a hypothetical value of 0. 