Notch signaling regulates neuroepithelial stem cell maintenance and neuroblast formation in Drosophila optic lobe development

►The Notch pathway is active in the optic lobe neuroepithelium. ►Notch or Delta mutant brains developed no lamina and an undersized medulla due to early depletion of neuroepithelial stem cells in the optic lobe. ►Mosaic clone analyses indicate that the Delta/Notch/Su(H) pathway is required for both maintaining the neuroepithelial stem cells and inhibiting medulla neuroblast formation while E(spl)-C is only involved in the inhibition of medulla neuroblast formation. ►Notch pathway overactivation promotes neuroepithelial cell overexpansion. ►numb loss of function mimics Notch overactivation.