Each of these components has two counterparts in mammals (Pygo1 and Pygo2, BCL9 and BCL9-2/B9L, respectively, whereby BCL9-2 refers to the murine, and B9L to the human ortholog; below, we shall either name these proteins individually, or refer to them collectively as Pygo and BCL9 proteins); siRNA depletion experiments have indicated a role of Pygo1 and Pygo2, and of BCL9-2/B9L for efficient TCF-mediated transcription in colorectal cancer cells [21,24,25]. Here, BCL9 is linked to colorectal cancer.