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Annear MJ, Mowat FM, Occelli LM, Smith AJ, Curran PG, Bainbridge JW, Ali RR, Petersen-Jones SM. A Comprehensive Study of the Retinal Phenotype of Rpe65-Deficient Dogs. Cells 2021; 10:cells10010115. [PMID: 33435495 PMCID: PMC7827248 DOI: 10.3390/cells10010115] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2020] [Revised: 01/04/2021] [Accepted: 01/06/2021] [Indexed: 01/09/2023] Open
Abstract
The Rpe65-deficient dog has been important for development of translational therapies of Leber congenital amaurosis type 2 (LCA2). The purpose of this study was to provide a comprehensive report of the natural history of retinal changes in this dog model. Rpe65-deficient dogs from 2 months to 10 years of age were assessed by fundus imaging, electroretinography (ERG) and vision testing (VT). Changes in retinal layer thickness were assessed by optical coherence tomography and on plastic retinal sections. ERG showed marked loss of retinal sensitivity, with amplitudes declining with age. Retinal thinning initially developed in the area centralis, with a slower thinning of the outer retina in other areas starting with the inferior retina. VT showed that dogs of all ages performed well in bright light, while at lower light levels they were blind. Retinal pigment epithelial (RPE) inclusions developed and in younger dogs and increased in size with age. The loss of photoreceptors was mirrored by a decline in ERG amplitudes. The slow degeneration meant that sufficient photoreceptors, albeit very desensitized, remained to allow for residual bright light vision in older dogs. This study shows the natural history of the Rpe65-deficient dog model of LCA2.
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Affiliation(s)
- Matthew J Annear
- Department of Small Animal Clinical Sciences, Michigan State University, East Lansing, MI 48824, USA; (M.J.A.); (F.M.M.); (L.M.O.)
| | - Freya M Mowat
- Department of Small Animal Clinical Sciences, Michigan State University, East Lansing, MI 48824, USA; (M.J.A.); (F.M.M.); (L.M.O.)
| | - Laurence M Occelli
- Department of Small Animal Clinical Sciences, Michigan State University, East Lansing, MI 48824, USA; (M.J.A.); (F.M.M.); (L.M.O.)
| | - Alexander J Smith
- Department of Genetics, UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK; (A.J.S.); (J.W.B.); (R.R.A.)
| | - Paul G Curran
- Center for Statistical Consulting, Michigan State University, East Lansing, MI 48824, USA;
| | - James W Bainbridge
- Department of Genetics, UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK; (A.J.S.); (J.W.B.); (R.R.A.)
- NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, City Road, London EC1V 2PD, UK
| | - Robin R Ali
- Department of Genetics, UCL Institute of Ophthalmology, 11-43 Bath Street, London EC1V 9EL, UK; (A.J.S.); (J.W.B.); (R.R.A.)
- NIHR Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, City Road, London EC1V 2PD, UK
| | - Simon M Petersen-Jones
- Department of Small Animal Clinical Sciences, Michigan State University, East Lansing, MI 48824, USA; (M.J.A.); (F.M.M.); (L.M.O.)
- Correspondence:
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Ward R, Kaylor JJ, Cobice DF, Pepe DA, McGarrigle EM, Brockerhoff SE, Hurley JB, Travis GH, Kennedy BN. Non-photopic and photopic visual cycles differentially regulate immediate, early, and late phases of cone photoreceptor-mediated vision. J Biol Chem 2020; 295:6482-6497. [PMID: 32238432 DOI: 10.1074/jbc.ra119.011374] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 03/30/2020] [Indexed: 11/06/2022] Open
Abstract
Cone photoreceptors in the retina enable vision over a wide range of light intensities. However, the processes enabling cone vision in bright light (i.e. photopic vision) are not adequately understood. Chromophore regeneration of cone photopigments may require the retinal pigment epithelium (RPE) and/or retinal Müller glia. In the RPE, isomerization of all-trans-retinyl esters to 11-cis-retinol is mediated by the retinoid isomerohydrolase Rpe65. A putative alternative retinoid isomerase, dihydroceramide desaturase-1 (DES1), is expressed in RPE and Müller cells. The retinol-isomerase activities of Rpe65 and Des1 are inhibited by emixustat and fenretinide, respectively. Here, we tested the effects of these visual cycle inhibitors on immediate, early, and late phases of cone photopic vision. In zebrafish larvae raised under cyclic light conditions, fenretinide impaired late cone photopic vision, while the emixustat-treated zebrafish unexpectedly had normal vision. In contrast, emixustat-treated larvae raised under extensive dark-adaptation displayed significantly attenuated immediate photopic vision concomitant with significantly reduced 11-cis-retinaldehyde (11cRAL). Following 30 min of light, early photopic vision was recovered, despite 11cRAL levels remaining significantly reduced. Defects in immediate cone photopic vision were rescued in emixustat- or fenretinide-treated larvae following exogenous 9-cis-retinaldehyde supplementation. Genetic knockout of Des1 (degs1) or retinaldehyde-binding protein 1b (rlbp1b) did not eliminate photopic vision in zebrafish. Our findings define molecular and temporal requirements of the nonphotopic or photopic visual cycles for mediating vision in bright light.
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Affiliation(s)
- Rebecca Ward
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin D04 V1W8, Ireland
| | - Joanna J Kaylor
- Jules Stein Eye Institute, UCLA School of Medicine, Los Angeles, California 90095
| | - Diego F Cobice
- Mass Spectrometry Centre, School of Biomedical Sciences, Biomedical Sciences Research Institute, Ulster University, Coleraine BT52 1SA, Northern Ireland
| | - Dionissia A Pepe
- Centre for Synthesis and Chemical Biology, UCD School of Chemistry, University College Dublin, Dublin D04 V1W8, Ireland
| | - Eoghan M McGarrigle
- Centre for Synthesis and Chemical Biology, UCD School of Chemistry, University College Dublin, Dublin D04 V1W8, Ireland
| | - Susan E Brockerhoff
- Department of Biochemistry, University of Washington, Seattle, Washington 98109.,Department of Ophthalmology, University of Washington, Seattle, Washington 98109
| | - James B Hurley
- Department of Biochemistry, University of Washington, Seattle, Washington 98109.,Department of Ophthalmology, University of Washington, Seattle, Washington 98109
| | - Gabriel H Travis
- Jules Stein Eye Institute, UCLA School of Medicine, Los Angeles, California 90095.,Department of Biological Chemistry, UCLA School of Medicine, Los Angeles, California 90095
| | - Breandán N Kennedy
- UCD School of Biomolecular and Biomedical Science, UCD Conway Institute, University College Dublin, Dublin D04 V1W8, Ireland
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Thebeau C, Zhang S, Kolesnikov AV, Kefalov VJ, Semenkovich CF, Rajagopal R. Light deprivation reduces the severity of experimental diabetic retinopathy. Neurobiol Dis 2020; 137:104754. [PMID: 31978605 DOI: 10.1016/j.nbd.2020.104754] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Revised: 01/13/2020] [Accepted: 01/20/2020] [Indexed: 12/30/2022] Open
Abstract
Illumination of the retina is a major determinant of energy expenditure by its neurons. However, it remains unclear whether light exposure significantly contributes to the pathophysiology of common retinal disease. Driven by the premise that light exposure reduces the metabolic demand of the retina, recent clinical trials failed to demonstrate a benefit for constant illumination in the treatment of diabetic retinopathy. Here, we instead ask whether light deprivation or blockade of visual transduction could modulate the severity of this common cause of blindness. We randomized adult mice with two different models of diabetic retinopathy to 1-3 months of complete dark housing. Unexpectedly, we find that diabetic mice exposed to short or prolonged light deprivation have reduced diabetes-induced retinal pathology, using measures of visual function, compared to control animals in standard lighting conditions. To corroborate these results, we performed assays of retinal vascular health in diabetic Gnat1-/- and Rpe65-/- mice, which lack phototransduction. Both mutants displayed less diabetes-associated retinal vascular disease compared to respective wild-type controls. Collectively, these results suggest that light-induced visual transduction promotes the development of diabetic retinopathy and implicate photoreceptors as an early source of visual pathology in diabetes.
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Affiliation(s)
- Christina Thebeau
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Sheng Zhang
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Alexander V Kolesnikov
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Vladimir J Kefalov
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Clay F Semenkovich
- Division of Endocrinology, Metabolism, and Lipid Research, Washington University School of Medicine, Saint Louis, MO 63110, USA; Department of Cell Biology and Physiology, Washington University School of Medicine, Saint Louis, MO 63110, USA
| | - Rithwick Rajagopal
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, Saint Louis, MO 63110, USA.
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Li S, Samardzija M, Yang Z, Grimm C, Jin M. Pharmacological Amelioration of Cone Survival and Vision in a Mouse Model for Leber Congenital Amaurosis. J Neurosci 2016; 36:5808-19. [PMID: 27225770 DOI: 10.1523/JNEUROSCI.3857-15.2016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2015] [Accepted: 04/20/2016] [Indexed: 11/21/2022] Open
Abstract
UNLABELLED RPE65, an abundant membrane-associate protein in the retinal pigment epithelium (RPE), is a key retinoid isomerase of the visual cycle necessary for generating 11-cis-retinal that functions not only as a molecular switch for activating cone and rod visual pigments in response to light stimulation, but also as a chaperone for normal trafficking of cone opsins to the outer segments. Many mutations in RPE65 are associated with Leber congenital amaurosis (LCA). A R91W substitution, the most frequent LCA-associated mutation, results in a severe decrease in protein level and enzymatic activity of RPE65, causing cone opsin mislocalization and early cone degeneration in the mutation knock-in mouse model of LCA. Here we show that R91W RPE65 undergoes ubiquitination-dependent proteasomal degradation in the knock-in mouse RPE due to misfolding. The 26S proteasome non-ATPase regulatory subunit 13 mediated degradation specifically of misfolded R91W RPE65. The mutation disrupted membrane-association and colocalization of RPE65 with lecithin:retinol acyltransferase (LRAT) that provides the hydrophobic substrate for RPE65. Systemic administration of sodium 4-phenylbutyrate (PBA), a chemical chaperone, increased protein stability, enzymatic activity, membrane-association, and colocalization of R91W RPE65 with LRAT. This rescue effect increased synthesis of 11-cis-retinal and 9-cis-retinal, a functional iso-chromophore of the visual pigments, led to alleviation of S-opsin mislocalization and cone degeneration in the knock-in mice. Importantly, PBA-treatment also improved cone-mediated vision in the mutant mice. These results indicate that PBA, a U.S. Food and Drug Administration-approved safe oral medication, may provide a noninvasive therapeutic intervention that delays daylight vision loss in patients with RPE65 mutations. SIGNIFICANCE STATEMENT LCA is a severe early onset retinal dystrophy. Recent clinical trials of gene therapy have implicated the need of an alternative or combination therapy to improve cone survival and function in patients with LCA caused by RPE65 mutations. Using a mouse model carrying the most frequent LCA-associated mutation (R91W), we found that the mutant RPE65 underwent ubiquitination-dependent proteasomal degradation due to misfolding. Treatment of the mice with a chemical chaperone partially corrected stability, enzymatic activity, and subcellular localization of R91W RPE65, which was also accompanied by improvement of cone survival and vision. These findings identify an in vivo molecular pathogenic mechanism for R91W mutation and provide a feasible pharmacological approach that can delay vision loss in patients with RPE65 mutations.
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