Fig. 4. Prolonged Cut expression during mid-oogenesis caused defects in the mitotic cycle/endocycle switch. Cut misexpression and Cut-String double misexpression were achieved by the flip-out Gal4/UAS technique and are marked by co-expression of GFP (green in A-G). All the clones were also marked by Cut staining (not shown in the figure), except those in F. DAPI is shown in blue (A-C,G) and white (A'). (A,A') Continuous expression of Cut during mid-oogenesis caused the follicle cells to be more densely distributed and their nuclei to be slightly smaller than those of the wild type. (B,B') Cyclin A (shown in red in B and white in B') was found to be expressed in some of the follicle cells misexpressing Cut in a stage 9 egg chamber, whereas CycA was no longer present in wild-type cells. (C,C') ß-gal expression (red in C and white in C') from a fzr enhancer trap line fzr^G0326 was downregulated in follicle-cell clones with overexpression of Cut during mid-oogenesis. (D,D') ß-gal expression (red in D and white in D') from stg-lacZ showed no change in cut misexpressing clones during mid-oogenesis. (E,E') PH3 (red in D and white in D') staining was found occasionally during mid-oogenesis in follicle cells misexpressing both Cut and Stg. (F,F',F'') Follicle-cell clones overexpressing Cut in stage 10B egg chambers did not switch to the amplification stage. BrdU incorporation (red in F and white in F') and Orc2 staining (blue in F and white in F'') were not present in the clonal cells (outlined). (G,G') Overexpression of Cut in a stage 10B egg chamber affected the uniform Cyclin E expression pattern. No Cyclin E expression (red in G and white in G') was detected in the clone misexpressing Cut (outlined).