Quiescent Oct4 + Neural Stem Cells (NSCs) Repopulate Ablated Glial Fibrillary Acidic Protein + NSCs in the Adult Mouse Brain

Stem Cells. 2017 Sep;35(9):2071-2082. doi: 10.1002/stem.2662. Epub 2017 Jul 21.

Abstract

Adult primitive neural stem cells (pNSCs) are a rare population of glial fibrillary acidic protein (GFAP)- Oct4+ cells in the mouse forebrain subependymal zone bordering the lateral ventricles that give rise to clonal neurospheres in leukemia inhibitory factor in vitro. pNSC neurospheres can be passaged to self-renew or give rise to GFAP+ NSCs that form neurospheres in epidermal growth factor and fibroblast growth factor 2, which we collectively refer to as definitive NSCs (dNSCs). Label retention experiments using doxycycline-inducible histone-2B (H2B)-green fluorescent protein (GFP) mice and several chase periods of up to 1 year quantified the adult pNSC cell cycle time as 3-5 months. We hypothesized that while pNSCs are not very proliferative at baseline, they may exist as a reserve pool of NSCs in case of injury. To test this function of pNSCs, we obtained conditional Oct4 knockout mice, Oct4fl/fl ;Sox1Cre (Oct4CKO ), which do not yield adult pNSC-derived neurospheres. When we ablated the progeny of pNSCs, namely all GFAP+ dNSCs, in these Oct4CKO mice, we found that dNSCs did not recover as they do in wild-type mice, suggesting that pNSCs are necessary for dNSC repopulation. Returning to the H2B-GFP mice, we observed that the cytosine β-d-arabinofuranoside ablation of proliferating cells including dNSCs-induced quiescent pNSCs to proliferate and significantly dilute their H2B-GFP label. In conclusion, we demonstrate that pNSCs are the most quiescent stem cells in the adult brain reported to date and that their lineage position upstream of GFAP+ dNSCs allows them to repopulate a depleted neural lineage. Stem Cells 2017;35:2071-2082.

Keywords: Adult stem cells; Neural stem cells (NSCs); Stem cell cycle; Tissue regeneration.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aging / metabolism*
  • Animals
  • Brain / metabolism*
  • Cell Cycle*
  • Cell Proliferation
  • Glial Fibrillary Acidic Protein / metabolism*
  • Mice, Knockout
  • Mitosis
  • Models, Biological
  • Neural Stem Cells / cytology*
  • Neural Stem Cells / metabolism*
  • Octamer Transcription Factor-3 / metabolism*
  • SOXB1 Transcription Factors / metabolism
  • Spheroids, Cellular / cytology

Substances

  • Glial Fibrillary Acidic Protein
  • Octamer Transcription Factor-3
  • SOXB1 Transcription Factors

Grant support