Fig. S1. Cell death in third-instar GCNs upon knockdown of Sns or Kirre. GCNs from third-instar larvae that were genetically sns-GCN-nGFP, sns-GCN-Gal4/+ (A,D), sns-GCN-nGFP, sns-GCN-Gal4/+; UAS-sns-IR(1)/+ (B,E) or sns-GCN-nGFP, sns-GCN-Gal4/kirre-IR(1) (C,F). Cells were analyzed by TUNEL and immunostained for Sns (A-C) or Kirre (D-F). Approximately half of the cells were TUNEL positive in B,C,E,F, but no TUNEL-positive GCNs were apparent in the controls A,D. Neither Kirre nor Sns persists in these defective cells. Scale bar: 10 m.

Movie 1. Real-time imaging of fusion in wild-type embryo, stage 14. The fluorescence of nGFP and gapGFP is shown in green. Red dots denote that two single-nucleate cells fuse into one binucleate cell. The 3D movie was generated by IMARIS ×64 6.1.5 (Bitplane).

Movie 2. 3D animation of uptake of molecules by endocytosis. GCNs from second-instar larvae of wild-type control were incubated with Cascade Blue dextran-10 kD (green) and Alexa Fluor 555 BSA (red) for 30 seconds. The yellow spots show the colocalization of the two molecules. The 3D movie was generated by IMARIS ×64 6.1.5 (Bitplane).