Downregulation of Notch mediates the seamless transition of individual Drosophila neuroepithelial progenitors into optic medullar neuroblasts during prolonged G1

►Neuroepithelial cells are converted into neuroblasts. ►The conversion occurs during a prolonged G1. ►The conversion includes an epithelial-to-nonepithelial change. ►Notch signaling is activated temporally. ►Notch signaling coordinates the conversion.