Up-regulation of Ttk69 is required for the proper E/A switch and cell differentiation. Images in A and E–G are collapsed images of the z stacks. ttk^1e11 mutant clones are marked by the absence of Ttk69 (A, E, and F; green) or GFP (D and G; green). (A and A′) Cut (A, red; A′, white) was not detected in ttk mutant clones (outlined) in a stage 10B egg chamber. (B and C) The expression pattern of Ttk69 in follicle cells. Ttk69 was steadily expressed at a low level in follicle cells before stage 10 (B) but significantly up-regulated at stage 10B (C). (D and D′) ttk mutant follicle cells (outlined) at stage 10B had oscillating genomic BrdU incorporation (D, red; D′, white). (E and E′) dE2F1 (E, red; E′, white) showed an oscillating expression pattern with an overall low level in ttk mutant clones (outlined) in a stage 10B egg chamber. The arrow points to a follicle cell with dE2F1 expression, and the arrowhead points to one without dE2F1 expression. (F and F′) Hnt (F, red; F′, white) was still detected in stage 10B ttk mutant clones. Outlining indicates the ttk mutant follicle cells. (G and G′) MPM2 staining (red) retained an oscillating pattern in ttk mutant clones in a stage 10B egg chamber. The arrow points to a cell with MPM2 signal, and the arrowhead points to a cell without MPM2 signal. Outlining indicates the ttk mutant follicle cells. Bars, 10 μm.