H2BC21 and infection: By co-infecting A coated virus (RCASA) harboring the Fzd7-ΔPDB mutant together with RCASB-H2B-GFP-2A-mCherry into chicken limbs, we achieved super-infection, such that many fluorescently labeled cells became rounder and disorganized (Figure 3—figure supplement 1) undergoing cell division in arbitrary directions rather than along the mediolateral axis (Figure 3a) (Figure 3—figure supplement 2) (Video 4).