FIGURE 1:

The actin bundle defects during late-stage follicle development are similar in fascin and pxt mutants. (A–F) Maximum projections of three confocal slices of S10B (A–C) and S12 (D–F) follicles taken at 20× magnification. (A′–F′) Maximum projections of four or five confocal slices of posterior nurse cells of the follicles in A–F acquired at 40× magnification. (G–I) Maximum projections of six or seven confocal slices of S14 follicles acquired by tiling at 20× magnification. (A–I) Merged images: F-actin (phalloidin), white; DNA (DAPI), cyan. (A′–F′) F-actin (phalloidin), white. (A–A′, D–D′, G) Wild-type (yw). (B–B′, E–E′, H) pxt^f. (C–C′, F–F′, I) fascin^sn2/fascin^sn36a. Wild-type S10B follicles possess a robust network of parallel actin filament bundles extending from the nurse cell membranes toward the nuclei in all of the nurse cells (A, A′). At the completion of nurse cell dumping (S12), the nurse cells have completely transferred their cytoplasmic contents to the elongating oocyte and the bundles have condensed (D, D′). pxt-mutant S10B follicles exhibit a spectrum of actin-remodeling defects, ranging from reduced bundle formation to a complete loss of bundles (B, B′). Similarly, fascin transheterozygotes show a substantial reduction in elongated bundles at S10B (C, C′). As a result, the nurse cells in both mutants fail to complete dumping at S12 (E–E′ pxt; F-F' fascin, earlier-stage follicle outlined by dotted yellow line). Unlike in wild-type S14 follicles (G), this results in a short-egg phenotype and the persistence of nurse cells at S14 in both pxt and fascin mutants (H–I, dorsal appendages outlined by dotted red line). Scale bars, 50 μm.