Figure 5.

Subcellular localization of Numb-β-gal fusion proteins expressed in transgenic Drosophila embryos. Mating of flies carrying the transgenes UAS-numb-01-lacZ (A), UAS-numb-02-lacZ (B), UAS-numb-03-lacZ (C), or UAS-numb-04-lacZ (D) with flies carrying the sca-GAL4 transgene (25) generated embryos carrying both transgenes that were identified by their β-gal expression. Optical cross sections of 4–6 hr old embryos stained with anti-β-gal (green) and propidium-iodide (DNA, red) are shown. Each panel shows a mitotic neuroblast (Left, arrowhead marks the basal cell cortex) and a neuroblast/GMC pair just after cell division (Right, arrow marks the GMC). (A) Numb-01-β-gal is cytoplasmic and does not preferentially segregate into the GMC. (B and C) Numb-02-β-gal (B) and Numb-03-β-gal (C) are localized to the cell membrane but do not localize asymmetrically during mitosis and consequently segregate into both daughter cells. (D) Numb-04-β-gal first localizes to the cell membrane in interphase cells (not shown), then forms a basal cortical crescent during mitosis (arrowhead) and preferentially segregates into the GMC after cell division (arrow).