ITGA2 and cyst: These results strongly imply that stereotypical polycystic disease pattern forms from multiple mutant cells and larger cysts may undergo cyst-fission and “pinch off” to generate smaller, daughter cysts To explore this further, we adapted our ex vivo duct culture and found that as ducts became cysts, BECs expressed ITGA2 protein de novo, which localised to the basal (non-luminal) surface of cysts, whereas non-cultured ducts were ITGA2-negative (Fig. 4C and fig.