Fig. 2. k-Means clustering analysis showing additive or antagonistic effects of Hg and TCDD on gene expression. Gene cluster analysis was performed using the k-means clustering (gene cluster n = 5, array cluster n = 1) of genes differentially expressed by (A) low-dose Hg; low-dose TCDD; low-dose Hg and TCDD combination. (B) High-dose Hg; high-dose TCDD; high-dose Hg and TCDD combination. Pathway analysis of the genes in each cluster was performed using ingenuity pathway analysis (IPA). Fischer's exact test (p < 0.05) was used for canonical pathway identification. Blue: low expression; red: high expression.