Sox2 controls neural stem cell self-renewal through a Fos-centered gene regulatory network

Stem Cells. 2021 Aug;39(8):1107-1119. doi: 10.1002/stem.3373. Epub 2021 Mar 29.

Abstract

The Sox2 transcription factor is necessary for the long-term self-renewal of neural stem cells (NSCs). Its mechanism of action is still poorly defined. To identify molecules regulated by Sox2, and acting in mouse NSC maintenance, we transduced, into Sox2-deleted NSC, genes whose expression is strongly downregulated following Sox2 loss (Fos, Jun, Egr2), individually or in combination. Fos alone rescued long-term proliferation, as shown by in vitro cell growth and clonal analysis. Furthermore, pharmacological inhibition by T-5224 of FOS/JUN AP1 complex binding to its targets decreased cell proliferation and expression of the putative target Suppressor of cytokine signaling 3 (Socs3). Additionally, Fos requirement for efficient long-term proliferation was demonstrated by the reduction of NSC clones capable of long-term expansion following CRISPR/Cas9-mediated Fos inactivation. Previous work showed that the Socs3 gene is strongly downregulated following Sox2 deletion, and its re-expression by lentiviral transduction rescues long-term NSC proliferation. Fos appears to be an upstream regulator of Socs3, possibly together with Jun and Egr2; indeed, Sox2 re-expression in Sox2-deleted NSC progressively activates both Fos and Socs3 expression; in turn, Fos transduction activates Socs3 expression. Based on available SOX2 ChIPseq and ChIA-PET data, we propose a model whereby Sox2 is a direct activator of both Socs3 and Fos, as well as possibly Jun and Egr2; furthermore, we provide direct evidence for FOS and JUN binding on Socs3 promoter, suggesting direct transcriptional regulation. These results provide the basis for developing a model of a network of interactions, regulating critical effectors of NSC proliferation and long-term maintenance.

Keywords: AP1 inhibitor T-5224; CRISPR; CUT&RUN; Fos; Socs3; Sox2; lentiviral vector; neural stem cells (NSCs); self-renewal; transcription factors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Proliferation / genetics
  • Cell Self Renewal / genetics
  • Gene Expression Regulation
  • Gene Regulatory Networks
  • Mice
  • Neural Stem Cells* / metabolism
  • Proto-Oncogene Proteins c-fos* / genetics
  • Proto-Oncogene Proteins c-fos* / metabolism
  • SOXB1 Transcription Factors* / genetics
  • SOXB1 Transcription Factors* / metabolism
  • Suppressor of Cytokine Signaling 3 Protein / genetics
  • Suppressor of Cytokine Signaling 3 Protein / metabolism

Substances

  • Fos protein, mouse
  • Proto-Oncogene Proteins c-fos
  • SOXB1 Transcription Factors
  • Suppressor of Cytokine Signaling 3 Protein