BEST1 expression in the retinal pigment epithelium is modulated by OTX family members

Hum Mol Genet. 2009 Jan 1;18(1):128-41. doi: 10.1093/hmg/ddn323. Epub 2008 Oct 10.


A number of genes preferentially expressed in the retinal pigment epithelium (RPE) are associated with retinal degenerative disease. One of these, BEST1, encodes bestrophin-1, a protein that when mutated causes Best macular dystrophy. As a model for RPE gene regulation, we have been studying the mechanisms that control BEST1 expression, and recently demonstrated that members of the MITF-TFE family modulate BEST1 transcription. The human BEST1 upstream region from -154 to +38 bp is sufficient to direct expression in the RPE, and positive-regulatory elements exist between -154 and -104 bp. Here, we show that the -154 to -104 bp region is necessary for RPE expression in transgenic mice and contains a predicted OTX-binding site (Site 1). Since another non-canonical OTX site (Site 2) is located nearby, we tested the function of these sites using BEST1 promoter/luciferase constructs by in vivo electroporation and found that mutation of both sites reduces promoter activity. Three OTX family proteins - OTX1, OTX2 and CRX - bound to both Sites 1 and 2 in vitro, and all of them increased BEST1 promoter activity. Surprisingly, we found that human and bovine RPE expressed not only OTX2 but also CRX, the CRX genomic region in bovine RPE was hypersensitive to DNase I, consistent with active transcription, and that both OTX2 and CRX bound to the BEST1 proximal promoter in vivo. These results demonstrate for the first time CRX expression in the RPE, and suggest that OTX2 and CRX may act as positive modulators of the BEST1 promoter in the RPE.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Bestrophins
  • Binding Sites
  • Cattle
  • Cell Line
  • Chloride Channels / genetics*
  • Chloride Channels / metabolism
  • Corneal Dystrophies, Hereditary / genetics
  • Corneal Dystrophies, Hereditary / metabolism
  • Eye Proteins / genetics*
  • Eye Proteins / metabolism
  • Gene Expression Regulation*
  • Genes, Reporter
  • Homeodomain Proteins / genetics
  • Homeodomain Proteins / metabolism*
  • Humans
  • Mice
  • Mice, Transgenic
  • Multigene Family
  • Otx Transcription Factors / genetics
  • Otx Transcription Factors / metabolism*
  • Promoter Regions, Genetic
  • Retinal Pigment Epithelium / metabolism*
  • Trans-Activators / genetics
  • Trans-Activators / metabolism*


  • BEST1 protein, human
  • Bestrophins
  • Chloride Channels
  • Eye Proteins
  • Homeodomain Proteins
  • OTX1 protein, human
  • OTX2 protein, human
  • Otx Transcription Factors
  • Trans-Activators
  • cone rod homeobox protein