Fig. 4. The cytoskeleton recruits the membranes to the fusome. (A-F") Comparison of Rtnl1-GFP as a specific marker for the fusomal membranes with cytoskeletal components of the fusome: z-stack (A) or single confocal section (B) comparison of Rtnl1 (green in A and B and as a single channel in A' and B') with the adducin-like protein Hts (purple in A and B and as a single channel in A" and B"). Note that Hts is concentrated on spectrosomes and early fusomes and then rapidly declines in intensity during region 2b, respectively, whereas Rtnl1 becomes increasingly stronger with progress of the forming cyst through the germarium. (C,D) Two fusomes in early and later region 2b, demonstrating the increase in membrane fusome over cytoskeletal fusome. Note that the membranes (marked by Rtnl1-GFP in green in C and D and as a single channel in C' and D') are found throughout and also surrounding the structure labeled with the cytoskeletal fusome marker Hts (purple in C and D and as a single channel in C" and D"). (E) -Spectrin (purple in E and as a single channel in E") appears similar to Hts in its decline in intensity over the germarium compared with Rtnl1-GFP (green in E and as a single channel in E"), whereas Shot, F, remains very strong all throughout the germarium (purple in F and as a single channel in F"). Bars, 10 µm (A,B,E,F), 5 µm (C,D).