P450 gene regulatory Bayesian subnetwork. (A) A P450 gene regulatory subnetwork composed of both the P450 genes and the genes that are two-edges away from any P450 gene. P450 genes and the known P450 regulators in the subnetwork are highlighted as red circles and blue squares, respectively. (B) The same subnetwork highlighted with liver genes responsive to ligands of known regulators of P450s, namely, AHR, CAR, or PXR (Slatter et al. 2006) in mouse (cyan nodes), rat (green nodes), and both species (red nodes). (C) A pruned P450 subnetwork composed of the key regulators identified in A and their downstream P450 targets. The known regulators and P450 genes are shown as blue rectangles and red ovals, respectively.