In vivo function of the orphan nuclear receptor NR2E3 in establishing photoreceptor identity during mammalian retinal development

Neuroscience Graduate Program, Department of Ophthalmology and Visual Sciences, W.K. Kellogg Eye Center, University of Michigan, Ann Arbor 48105, USA.
Human Molecular Genetics (Impact Factor: 6.39). 10/2006; 15(17):2588-602. DOI: 10.1093/hmg/ddl185
Source: PubMed


Rod and cone photoreceptors in mammalian retina are generated from common pool(s) of neuroepithelial progenitors. NRL, CRX and NR2E3 are key transcriptional regulators that control photoreceptor differentiation. Mutations in NR2E3, a rod-specific orphan nuclear receptor, lead to loss of rods, increased density of S-cones and supernormal S-cone-mediated vision in humans. To better understand its in vivo function, NR2E3 was expressed ectopically in the Nrl-/- retina, where post-mitotic precursors fated to be rods develop into functional S-cones similar to the human NR2E3 disease. Expression of NR2E3 in the Nrl-/- retina completely suppressed cone differentiation and resulted in morphologically rod-like photoreceptors, which were however not functional. Gene profiling of FACS-purified photoreceptors confirmed the role of NR2E3 as a strong suppressor of cone genes but an activator of only a subset of rod genes (including rhodopsin) in vivo. Ectopic expression of NR2E3 in cone precursors and differentiating S-cones of wild-type retina also generated rod-like cells. The dual regulatory function of NR2E3 was not dependent upon the presence of NRL and/or CRX, but on the timing and level of its expression. Our studies reveal a critical role of NR2E3 in establishing functional specificity of NRL-expressing photoreceptor precursors during retinal neurogenesis.


Available from: Artur Cideciyan
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    • "The energy of the UV flashes was adjusted to evoke responses matched in waveform to those elicited by the green stimulus in WT mice. The stimuli were presented in a ganzfeld lined with aluminum foil [7], [11], [12]. "
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    ABSTRACT: Mutations in the CEP290 (cilia-centrosomal protein 290 kDa) gene in Leber congenital amaurosis (LCA) cause early onset visual loss but retained cone photoreceptors in the fovea, which is the potential therapeutic target. A cone-only mouse model carrying a Cep290 gene mutation, rd16;Nrl-/-, was engineered to mimic the human disease. In the current study, we determined the natural history of retinal structure and function in this murine model to permit design of pre-clinical proof-of-concept studies and allow progress to be made toward human therapy. Analyses of retinal structure and visual function in CEP290-LCA patients were also performed for comparison with the results in the model. Rd16;Nrl-/- mice were studied in the first 90 days of life with optical coherence tomography (OCT), electroretinography (ERG), retinal histopathology and immunocytochemistry. Structure and function data from a cohort of patients with CEP290-LCA (n = 15; ages 7-48) were compared with those of the model. CEP290-LCA patients retain a central island of photoreceptors with normal thickness at the fovea (despite severe visual loss); the extent of this island declined slowly with age. The rd16;Nrl-/- model also showed a relatively slow photoreceptor layer decline in thickness with ∼80% remaining at 3 months. The number of pseudorosettes also became reduced. By comparison to single mutant Nrl-/- mice, UV- and M-cone ERGs of rd16;Nrl-/- were at least 1 log unit reduced at 1 month of age and declined further over the 3 months of monitoring. Expression of GNAT2 and S-opsin also decreased with age. The natural history of early loss of photoreceptor function with retained cone cell nuclei is common to both CEP290-LCA patients and the rd16;Nrl-/- murine model. Pre-clinical proof-of-concept studies for uniocular therapies would seem most appropriate to begin with intervention at P35-40 and re-study after one month by assaying interocular difference in the UV-cone ERG.
    PLoS ONE 03/2014; 9(3):e92928. DOI:10.1371/journal.pone.0092928 · 3.23 Impact Factor
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    • "photoreceptors through the activation of an orphan nuclear receptor Nr2e3 ( Cheng et al . , 2006 ) . Deletion of Nrl resulted in the loss of rod photoreceptors and Nr2e3 expression in the mutant retinas ( Mears et al . , 2001 ) . Nr2e3 was shown to activate rod - specific genes , but works in con - cert with CrX , represses cone - specific genes ( Cheng et al . , 2006 ; Chen et al . , 2005 ; Peng et al . , 2005 ) . Hori - zontal cell specification is regulated by the core group of Foxn4 , Ptf1a and Prox1 . In the absence of any of these three genes , horizontal cell genesis is impaired ( Dyer et al . , 2003 ; Li et al . , 2004 ; Fujitani et al . , 2006 ) . Hes1 and Hes5 , which is a negative regulato"
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    ABSTRACT: The vertebrate retina is a well-characterized model for studying neurogenesis. Retinal neurons and glia are generated in a conserved order from a pool of mutlipotent progenitor cells. During retinal development, retinal stem/progenitor cells (RPC) change their competency over time under the influence of intrinsic (such as transcriptional factors) and extrinsic factors (such as growth factors). In this review, we summarize the roles of these factors, together with the understanding of the signaling pathways that regulate eye development. The information about the interactions between intrinsic and extrinsic factors for retinal cell fate specification is useful to regenerate specific retinal neurons from RPCs. Recent studies have identified RPCs in the retina, which may have important implications in health and disease. Despite the recent advances in stem cell biology, our understanding of many aspects of RPCs in the eye remains limited. PRCs are present in the developing eye of all vertebrates and remain active in lower vertebrates throughout life. In mammals, however, PRCs are quiescent and exhibit very little activity and thus have low capacity for retinal regeneration. A number of different cellular sources of RPCs have been identified in the vertebrate retina. These include PRCs at the retinal margin, pigmented cells in the ciliary body, iris, and retinal pigment epithelium, and Müller cells within the retina. Because PRCs can be isolated and expanded from immature and mature eyes, it is possible now to study these cells in culture and after transplantation in the degenerated retinal tissue. We also examine current knowledge of intrinsic RPCs, and human embryonic stems and induced pluripotent stem cells as potential sources for cell transplant therapy to regenerate the diseased retina. Anat Rec, 2013. © 2013 Wiley Periodicals, Inc.
    The Anatomical Record Advances in Integrative Anatomy and Evolutionary Biology 01/2014; 297(1). DOI:10.1002/ar.22800 · 1.54 Impact Factor
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    • "In concert with other transcription factors, NR2E3 has a dual role to consolidate the rod fate of rod precursor cells: NR2E3 is associated with the promoters of both cone-specific genes, including the cone opsin genes, to repress their transcription, and rod-specific genes, including rhodopsin, to activate their transcription. The default state of photoreceptor precursor differentiation appears to be formation of S-cone cells, which is inhibited in rod precursor cells by NR2E3 repressor function [8,9,10,11,12,15]. NR2E3 is not only expressed during photoreceptor cell differentiation, but rather is continuously expressed at high levels in mature retina [13,14], consistent with its proposed additional neuroprotective function. "
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    ABSTRACT: Photoreceptor-specific nuclear receptor (PNR, NR2E3) is a key transcriptional regulator of human photoreceptor differentiation and maintenance. Mutations in the NR2E3-encoding gene cause various retinal degenerations, including Enhanced S-cone syndrome, retinitis pigmentosa, and Goldman-Favre disease. Although physiological ligands have not been identified, it is believed that binding of small molecule agonists, receptor desumoylation, and receptor heterodimerization may switch NR2E3 from a transcriptional repressor to an activator. While these features make NR2E3 a potential therapeutic target for the treatment of retinal diseases, there has been a clear lack of structural information for the receptor. Here, we report the crystal structure of the apo NR2E3 ligand binding domain (LBD) at 2.8 Å resolution. Apo NR2E3 functions as transcriptional repressor in cells and the structure of its LBD is in a dimeric auto-repressed conformation. In this conformation, the putative ligand binding pocket is filled with bulky hydrophobic residues and the activation-function-2 (AF2) helix occupies the canonical cofactor binding site. Mutations designed to disrupt either the AF2/cofactor-binding site interface or the dimer interface compromised the transcriptional repressor activity of this receptor. Together, these results reveal several conserved structural features shared by related orphan nuclear receptors, suggest that most disease-causing mutations affect the receptor's structural integrity, and allowed us to model a putative active conformation that can accommodate small ligands in its pocket.
    PLoS ONE 09/2013; 8(9):e74359. DOI:10.1371/journal.pone.0074359 · 3.23 Impact Factor
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