Sox2, Tlx, Gli3, and Her9 converge on Rx2 to define retinal stem cells in vivo

EMBO J. 2015 Jun 3;34(11):1572-88. doi: 10.15252/embj.201490706. Epub 2015 Apr 23.


Transcriptional networks defining stemness in adult neural stem cells (NSCs) are largely unknown. We used the proximal cis-regulatory element (pCRE) of the retina-specific homeobox gene 2 (rx2) to address such a network. Lineage analysis in the fish retina identified rx2 as marker for multipotent NSCs. rx2-positive cells located in the peripheral ciliary marginal zone behave as stem cells for the neuroretina, or the retinal pigmented epithelium. We identified upstream regulators of rx2 interrogating the rx2 pCRE in a trans-regulation screen and focused on four TFs (Sox2, Tlx, Gli3, and Her9) activating or repressing rx2 expression. We demonstrated direct interaction of the rx2 pCRE with the four factors in vitro and in vivo. By conditional mosaic gain- and loss-of-function analyses, we validated the activity of those factors on regulating rx2 transcription and consequently modulating neuroretinal and RPE stem cell features. This becomes obvious by the rx2-mutant phenotypes that together with the data presented above identify rx2 as a transcriptional hub balancing stemness of neuroretinal and RPE stem cells in the adult fish retina.

Keywords: de‐differentiation; gene regulation; neural stem cells; retinal stem cells; transcriptional network.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult Stem Cells / cytology
  • Adult Stem Cells / metabolism*
  • Animals
  • Fish Proteins / genetics
  • Fish Proteins / metabolism*
  • Gene Expression Regulation / physiology
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism*
  • Neural Stem Cells / cytology
  • Neural Stem Cells / metabolism*
  • Oryzias / genetics
  • Oryzias / metabolism*
  • Retina / cytology
  • Retina / metabolism*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*


  • Fish Proteins
  • Homeodomain Proteins
  • Transcription Factors