Fig. 5. Spermatogenesis defects in yuri^F64. (A-A'') The actin sleeves in yuri^F64 testes are within the cyst cells that encase the spermatid bundles. Phalloidin staining (red) coincides with GFP fluorescence (green) in a cyst cell expressing a GFP `exon trap' construct (cyst-GFP line G0147). (B) Longer actin sleeves are seen at the base of control testes in coiling sperm bundles. (C) Late-stage sperm nuclei in controls are straight and tightly bundled (arrow). (D) Nuclei in yuri^F64 sperm are frequently bent or helically coiled (arrows) and never condense to tight bundles. (E) Nascent actin cones are visible on the tips of mature nuclei in controls (arrow). (F) Very little F-actin accumulates on yuri^F64 mutant nuclei (arrow). (G) Small, individual actin cones are sometimes scattered along yuri^F64 mutant cysts. Scale bars: 10 µm in A-A'',C,D, 100 µm in B,E,F, 50 µm in G.