Abl promotes Notch internalization into the LE lumen to limit signaling. (A–E″) Single confocal sections of representative S2 cells showing Notch (anti-Notch indirect immunofluorescence, magenta) and Rab7-EYFP (green). “n” marks the cell nucleus. Transfections and treatments are shown: (A) Notch, (B) Notch + Abl dsRNA, (C) Notch + imatinib mesylate (Gleevec), (D) Notch + Abl, and (E) Notch + Abl^K417N (kinase dead). Scale bars = 5 µm. (F) Plot showing profiles of Notch levels across LE diameters in conditions in A–E, as depicted by the black arrowhead in cartoon schematic. A 0° cross-sectional line was used to measure Notch fluorescent intensity across LEs. Both Notch levels and LE diameters were normalized. Sample size (# of LEs evaluated): Notch (WT, N = 38), Notch + Abl dsRNA (N = 32), Notch + imatinib (N = 50), Notch + Abl (N = 27), and Notch + Abl^K417N (N = 52). (G) Relative Notch activity in manipulations shown in A–E. A t-student means comparison test was performed, and P values <0.05 (*), <0.01 (**), and <0.001(***) are indicated. (H and I) en > Abl and en > Abl^K417N adult wings, respectively. Orange arrowhead in H points to an ectopic vein at the PCV. Scale bars = 100 µm.