Mislocalization of late endosomes and subcellular tube guidance. (A and B) Terminal cells expressing CD4::mIFP under btl-gal4 (A’–B’) together with GrabFP-BInt (A–A’’) and endogenously labeled Rab7::YFP (B–B’’); see also Video 2. (C) Diagram of the GrabFP-BInt nanobody in vesicles and associating with Rab7::YFP around the vesicle. (C’) Venn diagram of vesicles containing CD4::mIFP, GrabFP-BInt, or Rab7::YFP. n = 395 vesicles, from six different cells homozygous for Rab7::YFP and collected across seven time points each. ND, not detected. (D–G) Cells expressing GrabFP-BInt and CD4::mIFP (D’–G’) under btl-gal4 in a Rab7::YFP homozygous (D’’–F’’) and heterozygous background (G’’). The outline of the cells was traced using the CD4::mIFP signal and is shown as a red dashed line. Black arrowheads point to vesicles containing CD4::mIFP, GrabFP-BInt, and Rab7::YFP, and white arrowheads point to vesicles that do not contain Rab7::YFP. Asterisks mark the tips of the subcellular tubes in D’, E’, and G’. (H) Proportion of cells with the indicated genotypes. Number of cells analyzed: control, n = 28; heterozygous YRab7 background, n = 26; homozygous YRab7 background, n = 59. Significance was assayed with χ2 tests; ****, P < 0.0001. Ventral is down.
