title: E-proteins orchestrate the progression of neural stem cell differentiation in the postnatal forebrain.
abstract: BACKGROUND
  Neural stem cell (NSC) differentiation is a complex multistep process that persists in specific regions of the postnatal forebrain and requires tight regulation throughout life. The transcriptional control of NSC proliferation and specification involves Class II (proneural) and Class V (Id1-4) basic helix-loop-helix (bHLH) proteins. In this study, we analyzed the pattern of expression of their dimerization partners, Class I bHLH proteins (E-proteins), and explored their putative role in orchestrating postnatal subventricular zone (SVZ) neurogenesis.
  
  
  RESULTS
  Overexpression of a dominant-negative form of the E-protein E47 (dnE47) confirmed a crucial role for bHLH transcriptional networks in postnatal neurogenesis by dramatically blocking SVZ NSC differentiation. In situ hybridization was used in combination with RT-qPCR to measure and compare the level of expression of E-protein transcripts (E2-2, E2A, and HEB) in the neonatal and adult SVZ as well as in magnetic affinity cell sorted progenitor cells and neuroblasts. Our results evidence that E-protein transcripts, in particular E2-2 and E2A, are enriched in the postnatal SVZ with expression levels increasing as cells engage towards neuronal differentiation. To investigate the role of E-proteins in orchestrating lineage progression, both in vitro and in vivo gain-of-function and loss-of-function experiments were performed for individual E-proteins. Overexpression of E2-2 and E2A promoted SVZ neurogenesis by enhancing not only radial glial cell differentiation but also cell cycle exit of their progeny. Conversely, knock-down by shRNA electroporation resulted in opposite effects. Manipulation of E-proteins and/or Ascl1 in SVZ NSC cultures indicated that those effects were Ascl1 dependent, although they could not solely be attributed to an Ascl1-induced switch from promoting cell proliferation to triggering cell cycle arrest and differentiation.
  
  
  CONCLUSIONS
  In contrast to former concepts, suggesting ubiquitous expression and subsidiary function for E-proteins to foster postnatal neurogenesis, this work unveils E-proteins as being active players in the orchestration of postnatal SVZ neurogenesis.
authors.forename: Bruno
authors.initials: B
authors.lastname: Fischer
authors.forename: Kasum
authors.initials: K
authors.lastname: Azim
authors.forename: Anahí
authors.initials: A
authors.lastname: Hurtado-Chong
authors.forename: Sandra
authors.initials: S
authors.lastname: Ramelli
authors.forename: María
authors.initials: M
authors.lastname: Fernández
authors.affiliation: Brain Research Institute, ETH Zurich/University of Zurich, 8057 Zurich, Switzerland. raineteau@hifo.uzh.ch.
authors.forename: Olivier
authors.initials: O
authors.lastname: Raineteau
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D002453:Cell Cycle / Q000235:genetics; D002454:Cell Differentiation / Q000502:physiology; D002465:Cell Movement; D003857:Deoxyuridine / Q000031:analogs & derivatives / Q000378:metabolism; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D019394:Ki-67 Antigen / Q000378:metabolism; D051379:Mice; D009419:Nerve Tissue Proteins; D058953:Neural Stem Cells / Q000145:classification* / Q000502:physiology*; D055495:Neurogenesis; D016548:Prosencephalon / Q000166:cytology* / Q000254:growth & development*; D014162:Transfection
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D003857:Deoxyuridine; D049452:Green Fluorescent Proteins; D019394:Ki-67 Antigen; D009419:Nerve Tissue Proteins; C499317:Ascl1 protein, mouse; C031086:5-ethynyl-2'-deoxyuridine