Figure 2. L1 neurons express Delta and activate Notch signaling in adjacent L4 neurons.

(A, A’) Svp+Zfh1+L1 neurons are adjacent to both newborn L3 and L4 neurons. Newborn L3 neurons (Erm+) are localized strictly above (distal to) L1 neurons (Svp+Zfh1+), and L1 neurons are localized strictly above (distal to) L4 neurons. Here and below, scale bar: 10 µm, n≥5 brains. The dashed line delineates the boundary between L1 (Svp+Zfh1+) and L4 (Bsh+) cell bodies. (B, B’) Delta is expressed in Zfh1+ L1 neurons which are adjacent to Bsh+ L4 neurons. The dashed line delineates the boundary between L1 (Zfh1+) and L4 (Bsh+) cell bodies. (C-C”) Delta is also expressed in a subset of LPCs (Tll+). The dashed line highlights Delta+ cell bodies. (D) Summary of A-C data; triangles represent Delta expression. (E-F”) Delta-KD (27G05-Gal4, tubP-GAL80[ts], UAS-Delta-RNAi) results in loss of Delta and Hey expression in lamina. HRP labels the axons of the photoreceptors, which represent the lamina column. A solid white line outlines the lamina and a dashed line delineates the boundary between Delta+ cells and Hey+ cells. (G) Summary.

Figure 2—figure supplement 1. Svp is not required to initiate or maintain Delta expression in L1 neurons.

(A–D) In Svp-KD (27G05-Gal4>UAS-Svp-RNAi), there is a loss of Svp while Hey expression remains unaffected at 19 hr APF. (C–D) Quantification (single optical section). Here and below, scale bar, 10 µm, n≥5 brains. (E–G) In Svp-KD (27G05-Gal4>UAS-Svp-RNAi), Delta expression remains unaffected at 19 hr APF. (G) Quantification (single optical section). Data are presented as mean ± SEM. Each dot represents each brain. n=5 brains in (C) and (D). n=6 brains for control and n=5 brains for Svp-KD in (G). ***p<0.001, ns = not significant, unpaired t-test.