Neural Stem Cells in Drosophila: Molecular Genetic Mechanisms Underlying Normal Neural Proliferation and Abnormal Brain Tumor Formation

Figure 3

Schematic representation of neurogenesis in optic lobe development. During larval development transition from neuroepithelial (NE, orange) to neuroblast (NB, blue) takes place. NE cells undergo symmetric proliferation with a horizontal spindle orientation to expand the pool of precursor cells and give rise to asymmetrically dividing NB (green). This is in response to the proneural wave of lethal of scute. The median NB divides asymmetrically with a vertical spindle orientation, owing to the clear subcellular localization of the apical (polarity proteins, red boundary) and basal (cell-fate determinants and their adaptor proteins, purple boundary) complex, to give rise to the Ganglion mother cells (GMCs) and further, post mitotic neuronal daughter cells. Most central brain neuroblasts during embryonic and postembryonic stages undergo asymmetric cell divisions [21, 27, 28].