Pcl does not regulate proliferation, and thus differs from some PcG members, such as the PRC1 components Posterior sex combs and Suppressor of zeste 2, loss of which causes tumor-like growth in imaginal discs (Classen et al., 2009) and the optic lobe (H.A. and I.S., unpublished). Here, PRC1 is linked to neoplasm.