Bypass of cell cycle exit is limited in the absence of E2F–DP function. (A–H) GFP-marked control or e2f2- or Dp-null mutant clones expressing the indicated cell cycle regulators were generated using the MARCM system and examined for ectopic mitoses by staining for PH3 (A and C–H) or ectopic CycE–Cdk2 activity indicated by MPM2 foci (B). Neurons are shown by staining for Elav (blue). Dp^−/− cells expressing CycE–Cdk2 do not bypass exit in wings (A) or eyes (B) after 36 h APF (40–44 h shown) and arrest with high levels of CycE–Cdk2 activity, as evident by MPM2-positive nuclear foci (eyes shown; arrows point to examples of foci in B). Some Dp^−/− cells expressing CycE and the G2-M regulator Stg continue cycling at 40 h APF, as indicated by PH3 (C and D) with a mitotic index of 0.9% and 3% in the wing and eye, respectively. A few mitoses are also observed in e2f2-null mutant cells expressing CycE and Stg at 40–44 h APF (E and F). However, similar levels of ectopic mitoses are evident in some control wings (G; mitotic index up to 0.3%) and eyes (H; up to 1.0%) expressing CycE and Stg (40–44 h APF shown). Bars: (A and C–H) 50 µm; (B) 20 µm.