EcR activity is required for the proper E/A switch and cell differentiation. Images in C, E, and F are collapsed images of the z stacks. Follicle cells with DN EcR-A misexpression were marked by EcR-A staining (C, E, and F; green) or Ttk69 down-regulation (D, green). (A and B) The pattern of EcR activity illustrated by the EcR-LBD-Gal4, UAS-nlacZ system. EcR activity, marked by the LacZ (LZ) expression, was not observed in follicle cells before stage 10 (A), but it was strongly detected in follicle cells at stage 10B and later (B). (C and C′) Ttk69 (C, red; C′, white) was down-regulated in follicle cells with DN EcR-A (outlined) at a stage 10B egg chamber. (D and D′) Oscillating genomic BrdU incorporation (D, red; D′, white) was observed in DN EcR-A–misexpressing follicle cells (outlined) in a stage 10B egg chamber. (E and E′) Hnt (E, red; E′, white) was still detected in follicle cells with DN EcR-A (outlined) at stage 10B. (F and F′) Cut (F, red; F′, white) was not detected in follicle cells with DN EcR-A (outlined) in a stage 10B egg chamber. Bars, 10 μm.