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Fig. 8. Epidermal cell cycle progression in CycA^- CycE^- and CycA^- dap^- double mutants. (A-J) Embryos at the stage of mitosis 15 were immunolabeled either with anti-Cyclin B3 (A,B; CycB3), or with anti-tubulin (C-F; Tub) and a DNA stain (G-J; DNA). Comparison of the anti-CycB3 signals in CycE^AR95; CycA^C8LR1 double mutants (B; CycE^-; CycA^-) and sibling control embryos (A; +) reveals a premature Cyclin B3 disappearance in the double mutants. The strong anti-CycB3 signals remaining in the head region and along the ventral midline (arrowheads) of double mutants are from cells programmed to progress through mitosis 14 late. They are still in G2 before mitosis 14 at the stage shown and they therefore also still have residual maternal Cyclin A in the double mutants. Mitotic figures (white arrows) reflecting progression through mitosis 15 are observed in sibling control (C,G; +) and CycA^C8LR1 (D,H; CycA^-) and CycE^AR95 (E,I; CycE^-) single mutant embryos, but not in CycE^AR95; CycA^C8LR1 double mutant embryos (F,J; CycA^- CycE^-). (K-N) Embryos were pulse labeled with BrdU. After the stage of mitosis 16, epidermal cells in dap⁴ single (M; dap^-) and dap⁴; CycA^C8LR1 double (N; CycA^- dap^-) mutants enter S phase, but not in sibling control (K; +) and CycA^C8LR1 single mutants (L; CycA^-). Remarkably, epidermal cells in dap⁴; CycA^C8LR1 double mutants enter S phase even though they have not progressed through mitosis 16. The failure of mitosis 16 is also evident from a comparison of the nuclear density in the epidermis (insets in M,N).

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