title: The photoreceptor-specific nuclear receptor Nr2e3 interacts with Crx and exerts opposing effects on the transcription of rod versus cone genes.
abstract: Nr2e3 is an orphan nuclear receptor expressed specifically by retinal photoreceptor cells. Mutations in Nr2e3 result in syndromes characterized by excess blue cones and loss of rods: enhanced S-cone syndrome (ESCS) in humans and rd7 in mice. Using yeast two-hybrid screens with Nr2e3 as bait, the cone-rod homeobox protein Crx was identified as an interacting partner of Nr2e3. Immunoprecipitation assays confirmed this Nr2e3-Crx interaction and identified the DNA-binding domain of each protein as the interaction motif. Immunohistochemistry demonstrated that Crx and Nr2e3 are co-expressed by rod photoreceptors and their precursors. Chromatin immunoprecipitation assays on mouse retina demonstrated that Nr2e3 and Crx co-occupy the promoter/enhancer region of several rod and cone genes in the rod photoreceptor cells. The promoter/enhancer occupancy of Nr2e3 is Crx-dependent, suggesting that Nr2e3 is associated with photoreceptor gene targets by interacting with Crx. Transient transfection assays in HEK293 cells demonstrated that Nr2e3 enhances rhodopsin, but represses S- or M-cone opsin transcription when interacting with Crx. Quantitative real-time RT-PCR analysis on postnatal day 28 (P28) retina of the rd7 mouse, which lacks Nr2e3 protein, revealed an up-regulation of cone genes, but down-regulation of rod genes. Several mutant forms of human Nr2e3 identified from ESCS patients showed defects in interacting with Crx and/or in transcriptional regulatory function. Altogether, our findings suggest that Nr2e3 is a dual-function transcriptional regulator that acts in concert with Crx to promote and maintain the function of rod photoreceptors.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St Louis, MO 63110, USA.
authors.forename: Guang-Hua
authors.initials: GH
authors.lastname: Peng
authors.forename: Omar
authors.initials: O
authors.lastname: Ahmad
authors.forename: Faisel
authors.initials: F
authors.lastname: Ahmad
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Liu
authors.forename: Shiming
authors.initials: S
authors.lastname: Chen
mesh_terms: D020816:Amino Acid Motifs / Q000235:genetics / Q000502:physiology; D000818:Animals; D002460:Cell Line; D005786:Gene Expression Regulation / Q000235:genetics / Q000502:physiology*; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051379:Mice; D057093:Orphan Nuclear Receptors; D011485:Protein Binding / Q000235:genetics / Q000502:physiology; D018160:Receptors, Cytoplasmic and Nuclear / Q000235:genetics / Q000378:metabolism*; D017949:Retinal Cone Photoreceptor Cells / Q000502:physiology*; D017948:Retinal Rod Photoreceptor Cells / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D018398:Homeodomain Proteins; C403073:NR2E3 protein, human; C485736:Nr2e3 protein, mouse; D057093:Orphan Nuclear Receptors; D018160:Receptors, Cytoplasmic and Nuclear; D015534:Trans-Activators; D014157:Transcription Factors; C109288:cone rod homeobox protein