Fig. 5. E2f2 restricts follicle cell DNA replication to gene amplification foci. (A) A wild-type stage 10B egg chambers stained with DAPI. (A') Schematic of a wild-type stage 10B egg chamber. At this stage, the columnar follicle cells that execute chorion gene amplification and that will eventually secrete the eggshell surround the developing oocyte in a single epithelial layer. Dissected ovaries were pulse labeled with BrdU for 1 hour and then immediately fixed. Incorporated BrdU was detected by indirect immunofluorescence. (B-F) Stage 10B egg chambers; (B'-F') stage 13 egg chambers. The left image in each panel is a surface view of the follicle cell epithelium located over the oocyte. The right image in each panel is a high magnification view of a single follicle cell nucleus. (B) yw⁶⁷ wild type. Distinct foci of BrdU incorporation corresponding with sites of gene amplification are observed in wild type. (C) Df(2L)E2f2³²⁹/Df(2L)E2f2³²⁹; P[E2f2^–; Mpp6⁺]/+. BrdU incorporation is detected throughout E2f2 null mutant follicle cells. (D) Df(2L)E2f2³²⁹/Df(2L)DS8, P[E2f2^1-188; Mpp6⁺]. This phenotype is similar to null at stage 13, but slightly weaker at stage 10B. (E) Df(2L)E2f2³²⁹/Df(2L)E2f2³²⁹; P[E2f2⁺; Mpp6⁺]/+. A wild type E2f2 transgene rescues the null mutant phenotype. (F) E2F2^16402a/Df(2L)DS8, P[E2f2^1-188; Mpp6⁺]. In this hypomorphic situation, different classes of replication patterns are apparent (best seen in F'): replication throughout the entire nucleus (large arrow), normal gene amplification foci (large arrowhead), absent replication (small arrowhead), and both amplification foci and genomic replication (small arrow).

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