Fig. 3. Loss of MASK increases programmed cell death and reduces proliferation. (A-C) mask clones in third instar larval eye imaginal discs. Non-clonal cells are marked with GFP (green) and apoptotic nuclei are marked with TUNEL-TMR (red). (D,E) Third instar eye imaginal discs are stained with antibodies against Elav, which is expressed in photoreceptor nuclei (red), and TUNEL-fluorescein, which marks the nuclei of apoptotic cells (green). White arrows mark the morphogenetic furrow. (D) Wild type (w); (E) w; mask^6.3/mask^7.29. (F,G) Alimentary canal tissue from third instar larvae stained for apoptotic nuclei with TUNEL-fluorescein (green). (F) Wild type (w); (G) w; mask^6.3/mask^7.29. (H-J) Third instar eye imaginal discs. As above, -Elav marks photoreceptor nuclei (red) and TUNEL-fluorescein marks apoptotic nuclei (green). White arrows mark the morphogenetic furrow. H) w, csw¹¹⁴ In these mutants, the morphogenetic furrow does not progress farther than is shown. (I) w; sev-csw^CS/+; (J) w; sev-csw^CS/mask^10.22. (K,L) Mutant clones (marked as cells not expressing GFP; green) in eye imaginal discs were stained with -phosphohistone H3 (red) to visualize nuclei in M phase. (K) Clones generated using hs-flp were small and rarely contained any mitotic cells. (L) Clones generated using ey-flp were larger and contained more cells undergoing mitosis. White arrowheads mark zones of mitosis before and after the morphogenetic furrow.