Fig. 5: Late endosomes are responsible for Notch inactivation at the wavefront.

a–l RNAi knockdown of rab7 (a), vps2 (d), vps22 (g), and vps25 (j) under the control of optix-Gal4 induces ectopic puncta of N (magenta or white, arrows) and fusion of the twin activation peaks of N (mγGFP in a, g, j and NRE-dVenus in d, green) at the wavefront (Lsc, blue). The magenta dotted boxes are magnified in the right panels showing the ectopic puncta of N. Asterisks indicate the optix-Gal4 positive areas outlined by white lines. The signal intensities of N activity (green), N expression (gray), and Lsc (blue) within the white and yellow dotted boxes in (a, d, g, j) are plotted in (b, e, h, k; controls) and (c, f, i, l; RNAi), respectively. Green arrows indicate the N activity peaks. m vps2 RNAi with a strong phenotype induces ectopic N puncta (magenta and white) and uniform N activity (NRE-dVenus, green) in a wide area (asterisk). Lsc (blue). n Quantification of N intensity (p = 0.020, 0.047, 0.017, 0.038 (*p < 0.05), two-sided t test). Numbers of quantified areas are indicated. Cross, mean; center line, median; box limits, upper and lower quartiles; whiskers, 1.5× interquartile range. o, p Fusion of the twin peaks of N activity (NRE-dVenus, green) in vps2 and vps22 mutant clones, respectively, visualized by the absence of RFP (magenta). Arrows indicate the upregulation of N activity between the twin peaks. Arrowheads indicate the absence of N activation in cells adjacent to the wavefront (Lsc, blue). Scale bars indicate 20 μm.