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Fig. 5. Polar cells are sufficient to specify border cells. Follicles with flip-out
clones (marked with GFP, green) expressing constitutively activated Notch
(ActN) and stained with Hoechst (DNA, white) and antibodies recognizing FasIII
(polar cells, red). The arrows indicate the position of border cell groups.
(A) Stage 9 follicle with an anterior group containing one polar cell and two
outer border cells, and a posterior group containing two polar cells and six
outer border cells. All cells express ActN. (B) Stage 10A follicle with an
anterior group containing the only ActN cell, which behaves as a polar cell
and migrates with three outer border cells. The posterior group includes the
wild-type polar cells and five outer border cells. (C) Stage 9 follicle in
which all cells express ActN and one group of border cells forms from four
polar cells and 11 outer border cells.