Fig. 7: The second Notch peak regulates the temporal patterning of neurogenesis.

a Klu expression (magenta) coincides with the second peak of N activity (mγGFP, green) as indicated by arrows behind the wavefront (Lsc, blue). b Klu expression (magenta) is eliminated in Dl mutant clones visualized by the absence of GFP (green), except for cells at the clone boundary (arrows). Lsc visualizes the accelerated wavefront inside the Dl mutant clones (blue). c, d Fusion of the twin peaks of N activity (mγGFP, green) and precocious Klu expression (magenta) indicated by arrows upon partial knockdown of Dl (c) and vps2 (d). Asterisks indicate the optix-Gal4-positive areas outlined by white lines. Yellow lines outline Klu-expressing NBs. The wavefronts are not accelerated (Lsc, blue). e optix-Gal4 is expressed in the dorsal (top) and ventral (bottom) subdomains of the optic lobe (GFP, green). GFP signals are stronger in the dorsal subdomain. Run (magenta). f Cells expressing Bsh-GFP (green) and Run (magenta) form the concentric zones that are complementary with each other. g, h Ectopic Run-positive cells (magenta) are found within the concentric zone expressing Bsh-GFP (green) upon partial knockdown of Dl and vps2 as indicated by arrows. Positions of Run and Bsh-positive cells are plotted in magenta and green within the defective areas and in black and gray in the other areas, respectively, in the right panels. i Overlaps between Run- and Bsh-positive areas are quantified in Dl and vps RNAi backgrounds (p = 0.034, 0.009 (*p < 0.05, **p < 0.01), two-sided t test, n = 4, number of brain samples). Cross, mean; center line, median; box limits, upper and lower quartiles; whiskers, 1.5× interquartile range. j, k Morphologies of Run-positive medulla neurons, Mi4 (j) and TmY16 (k) visualized by run-Gal4 UAS-CD8GFP MARCM clones (white). Run (red) and Ncad (blue). Layers in the medulla (M), lobula (Lo), and lobula plate (Lop). l Schematics of the temporal patterning of neurogenesis through N activity and Klu expression. Hth- and Klu-positive NBs produce Bsh- and Run-positive neurons, respectively. Fusion of the twin peaks of Notch activity leads to precocious Klu expression, which precociously produces Run-positive neurons. Scale bars, 20 μm.