Transcription factor SOX9 plays a key role in the regulation of visual cycle gene expression in the retinal pigment epithelium

J Biol Chem. 2014 May 2;289(18):12908-21. doi: 10.1074/jbc.M114.556738. Epub 2014 Mar 14.


The retinal pigment epithelium (RPE) performs specialized functions to support retinal photoreceptors, including regeneration of the visual chromophore. Enzymes and carrier proteins in the visual cycle function sequentially to regenerate and continuously supply 11-cis-retinal to retinal photoreceptor cells. However, it is unknown how the expression of the visual cycle genes is coordinated at the transcriptional level. Here, we show that the proximal upstream regions of six visual cycle genes contain chromatin-accessible sex-determining region Y box (SOX) binding sites, that SOX9 and LIM homeobox 2 (LHX2) are coexpressed in the nuclei of mature RPE cells, and that SOX9 acts synergistically with orthodenticle homeobox 2 (OTX2) to activate the RPE65 and retinaldehyde binding protein 1 (RLBP1) promoters and acts synergistically with LHX2 to activate the retinal G protein-coupled receptor (RGR) promoter. ChIP reveals that SOX9 and OTX2 bind to the promoter regions of RPE65, RLBP1, and RGR and that LHX2 binds to those of RPE65 and RGR in bovine RPE. ChIP with human fetal RPE cells shows that SOX9 and OTX2 also bind to the human RPE65, RLBP1, and RGR promoters. Conditional inactivation of Sox9 in mouse RPE results in reduced expression of several visual cycle genes, most dramatically Rpe65 and Rgr. Furthermore, bioinformatic analysis predicts that multiple common microRNAs (miRNAs) regulate visual cycle genes, and cotransfection of miRNA mimics with luciferase reporter constructs validated some of the predicted miRNAs. These results implicate SOX9 as a key regulator of visual cycle genes, reveal for the first time the functional role of LHX2 in the RPE, and suggest the possible regulation of visual cycle genes by common miRNAs.

Keywords: Eye; Gene Expression; Gene Regulation; MicroRNA; Retinal Pigment Epithelium; SOX9; Transcription; Visual Cycle.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Binding Sites / genetics
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cell Line
  • Cells, Cultured
  • Chromatin / genetics
  • Chromatin / metabolism
  • Eye Proteins / genetics*
  • Eye Proteins / metabolism
  • Gene Expression Regulation*
  • Gene Regulatory Networks
  • HEK293 Cells
  • Humans
  • Immunohistochemistry
  • LIM-Homeodomain Proteins / genetics
  • LIM-Homeodomain Proteins / metabolism
  • Mice
  • Mice, Knockout
  • MicroRNAs / genetics
  • Models, Genetic
  • Otx Transcription Factors / genetics
  • Otx Transcription Factors / metabolism
  • Retinal Pigment Epithelium / cytology
  • Retinal Pigment Epithelium / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • SOX9 Transcription Factor / genetics
  • SOX9 Transcription Factor / metabolism
  • SOX9 Transcription Factor / physiology*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • cis-trans-Isomerases / genetics
  • cis-trans-Isomerases / metabolism


  • 11-cis-retinal-binding protein
  • Carrier Proteins
  • Chromatin
  • Eye Proteins
  • LHX2 protein, human
  • LIM-Homeodomain Proteins
  • MicroRNAs
  • OTX2 protein, human
  • Otx Transcription Factors
  • SOX9 Transcription Factor
  • Transcription Factors
  • retinoid isomerohydrolase
  • cis-trans-Isomerases