A schematic diagram of preparing the list of input genes in the three case examples. In case 1, the input human genes are simply mapped to mouse genes by orthology. In case 2, the human genes are expanded by molecular network e.g. protein-protein interaction (PPI). In case 3, the input genes are first, network expanded and then mapped to mouse genes by orthology. Some of the human genes may have no orthologous (E and I) or multiple orthologous genes (H → h, h’) in mouse.