Temporal Patterning of Neural Progenitors in Drosophila

Abstract

Drosophila has recently become a powerful model system to understand the mechanisms of temporal patterning of neural progenitors called neuroblasts (NBs). Two different temporal sequences of transcription factors (TFs) have been found to be sequentially expressed in NBs of two different systems: the Hunchback, Krüppel, Pdm1/Pdm2, Castor, and Grainyhead sequence in the Drosophila ventral nerve cord; and the Homothorax, Klumpfuss, Eyeless, Sloppy-paired, Dichaete, and Tailless sequence that patterns medulla NBs. In addition, the intermediate neural progenitors of type II NB lineages are patterned by a different sequence: Dichaete, Grainyhead, and Eyeless. These three examples suggest that temporal patterning of neural precursors by sequences of TFs is a common theme to generate neural diversity. Cross-regulations, including negative feedback regulation and positive feedforward regulation among the temporal factors, can facilitate the progression of the sequence. However, there are many remaining questions to understand the mechanism of temporal transitions. The temporal sequence progression is intimately linked to the progressive restriction of NB competence, and eventually determines the end of neurogenesis. Temporal identity has to be integrated with spatial identity information, as well as with the Notch-dependent binary fate choices, in order to generate specific neuron fates.

Glial cells in neuronal development: recent advances and insights from Drosophila melanogaster

“…Drosophila neural stem cells, also termed neuroblasts (NBs), are plastic with an undifferentaited nature and serve as an excellent model to study stem-cell biology [21][22][23] .…”

“…These NBs, patterned by the distinct temporal and spatial expression of transcription factors, orchestrate the order and diversity of neural progeny in both the larval and adult CNS [22,23,28] .…”

“…These NBs generate most of the larval CNS neurons and enter a quiescence period for ~24 h at the end of embryogenesis [24][25][26][27] . How produce greater numbers of neurons than type I NBs [28][29][30] .These NBs, patterned by the distinct temporal and spatial expression of transcription factors, orchestrate the order and diversity of neural progeny in both the larval and adult CNS [22,23,28] .Glia participate in distinctive ways throughout this developmental process [31][32][33][34][35][36][37] . A fat body-glia-NB signaling relay has been demonstrated to regulate NB reactivation after quiescence [38, 39] .…”

GRHL2 coordinates regeneration of a polarized mucociliary epithelium from basal stem cells

“…Processes regulated by these factors include apical-basal polarity, intercellular adhesion, barrier function, and motility, as well as lineage choice and differentiation of progenitor populations (Wilanowski et al, 2002;Paré et al, 2012;Senga et al, 2012;Gao et al, 2013;Li et al, 2013). Epithelial tissues in which vertebrate grainyhead-like genes are known to be important include skin, developing neural tube, placental trophoblast, hepatic biliary cells, inner ear, and embryonic kidney (nephric duct; Ting et al, 2005;Chalmers et al, 2006;Werth et al, 2010; Pseudostratified airway epithelium of the lung is composed of polarized ciliated and secretory cells maintained by basal stem/progenitor cells.…”

Genetic Mechanisms Regulating the Spatiotemporal Modulation of Proliferation Rate and Mode in Neural Progenitors and Daughter Cells during Embryonic CNS Development

“…It also, in most cases, represses the factor next to the one it has activated. This transition is also observed in vitro for isolated, cultured NBs [125,126]. There are subtemporal factors which delineate a competence window into smaller windows.…”