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Bao X, Zhang Z, Guo Y, Buser C, Kochounian H, Wu N, Li X, He S, Sun B, Ross-Cisneros FN, Sadun AA, Huang L, Zhao M, Fong HKW. Human RGR Gene and Associated Features of Age-Related Macular Degeneration in Models of Retina-Choriocapillaris Atrophy. THE AMERICAN JOURNAL OF PATHOLOGY 2021; 191:1454-1473. [PMID: 34022179 DOI: 10.1016/j.ajpath.2021.05.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/18/2020] [Revised: 04/16/2021] [Accepted: 05/05/2021] [Indexed: 01/28/2023]
Abstract
Age-related macular degeneration (AMD) is a progressive eye disease and the most common cause of blindness among the elderly. AMD is characterized by early atrophy of the choriocapillaris and retinal pigment epithelium (RPE). Although AMD is a multifactorial disease with many environmental and genetic risk factors, a hallmark of the disease is the origination of extracellular deposits, or drusen, between the RPE and Bruch membrane. Human retinal G-protein-coupled receptor (RGR) gene generates an exon-skipping splice variant of RGR-opsin (RGR-d; NP_001012740) that is a persistent component of small and large drusen. Herein, the findings show that abnormal RGR proteins, including RGR-d, are pathogenic in an animal retina with degeneration of the choriocapillaris, RPE, and photoreceptors. A frameshift truncating mutation resulted in severe retinal degeneration with a continuous band of basal deposits along the Bruch membrane. RGR-d produced less severe disease with choriocapillaris and RPE atrophy, including focal accumulation of abnormal RGR-d protein at the basal boundary of the RPE. Degeneration of the choriocapillaris was marked by a decrease in endothelial CD31 protein and choriocapillaris breakdown at the ultrastructural level. Fundus lesions with patchy depigmentation were characteristic of old RGR-d mice. RGR-d was mislocalized in cultured cells and caused a strong cell growth defect. These results uphold the notion of a potential hidden link between AMD and a high-frequency RGR allele.
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Affiliation(s)
- Xuan Bao
- Department of Ophthalmology, Beijing Key Laboratory for the Diagnosis and Treatment of Retinal and Choroid Diseases, Peking University People's Hospital, Beijing, China; Department of Ophthalmology, Keck School of Medicine of USC, Los Angeles, California
| | - Zhaoxia Zhang
- Department of Ophthalmology, Keck School of Medicine of USC, Los Angeles, California; Shanxi Eye Hospital, Taiyuan, China
| | - Yanjiang Guo
- Department of Ophthalmology, Beijing Key Laboratory for the Diagnosis and Treatment of Retinal and Choroid Diseases, Peking University People's Hospital, Beijing, China
| | | | | | - Nancy Wu
- Norris Cancer Center, Keck School of Medicine of University of Southern California, Los Angeles, California
| | - Xiaohua Li
- Henan Eye Institute, Henan Provincial People's Hospital, Henan, China
| | - Shikun He
- Department of Pathology, Keck School of Medicine of USC, Los Angeles, California
| | - Bin Sun
- Shanxi Eye Hospital, Taiyuan, China
| | | | - Alfredo A Sadun
- Doheny Eye Institute, Los Angeles, California; Department of Ophthalmology, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California
| | - Lvzhen Huang
- Department of Ophthalmology, Beijing Key Laboratory for the Diagnosis and Treatment of Retinal and Choroid Diseases, Peking University People's Hospital, Beijing, China
| | - Mingwei Zhao
- Department of Ophthalmology, Beijing Key Laboratory for the Diagnosis and Treatment of Retinal and Choroid Diseases, Peking University People's Hospital, Beijing, China.
| | - Henry K W Fong
- Department of Ophthalmology, Keck School of Medicine of USC, Los Angeles, California; University of Southern California Roski Eye Institute, Los Angeles, California; Department of Molecular Microbiology and Immunology, University of Southern California, Los Angeles, California.
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Arya M, Sabrosa AS, Duker JS, Waheed NK. Choriocapillaris changes in dry age-related macular degeneration and geographic atrophy: a review. EYE AND VISION 2018; 5:22. [PMID: 30238015 PMCID: PMC6138930 DOI: 10.1186/s40662-018-0118-x] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 08/29/2018] [Indexed: 01/16/2023]
Abstract
Age-related macular degeneration (AMD) is a leading cause of central vision loss worldwide. The progression of dry AMD from early to intermediate stages is primarily characterized by increasing drusen formation and adverse impact on outer retinal cells. Late stage AMD consists of either geographic atrophy (GA), the non-exudative (dry) AMD subtype, or choroidal neovascularization, the exudative (wet) AMD subtype. GA is characterized by outer retinal and choroidal atrophy, specifically the photoreceptor layer, RPE, and choriocapillaris. Much remains to be discovered regarding the pathogenesis of AMD progression and subsequent development of GA. As the functionality of all three layers is closely linked, the temporal sequence of events that end up in atrophy is important in the understanding of the pathogenic pathway of the disease. The advent of OCTA, and particularly of swept-source technology, has allowed for depth-resolved imaging of retinal vasculature and the choriocapillaris. With the use of OCTA, recent studies demonstrate that choriocapillaris flow alterations are closely associated with the development and progression of AMD. Such changes may even possibly offer predictive value in determining progression of GA. This article reviews studies demonstrating choriocapillaris changes in dry AMD and summarizes the existing literature on the potential role of the choriocapillaris as a key factor in the pathogenesis of AMD.
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Affiliation(s)
- Malvika Arya
- 1New England Eye Center, Tufts Medical Center, Boston, MA USA.,Institude of Ophthalmology, Rio de Janeiro, Brazil
| | - Almyr S Sabrosa
- 1New England Eye Center, Tufts Medical Center, Boston, MA USA.,Institude of Ophthalmology, Rio de Janeiro, Brazil
| | - Jay S Duker
- 1New England Eye Center, Tufts Medical Center, Boston, MA USA
| | - Nadia K Waheed
- 1New England Eye Center, Tufts Medical Center, Boston, MA USA
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Zhang Z, Fong HK. Coexpression of nonvisual opsin, retinal G protein-coupled receptor, and visual pigments in human and bovine cone photoreceptors. Mol Vis 2018; 24:434-442. [PMID: 30034210 PMCID: PMC6031102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 06/29/2018] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Retinal G protein-coupled receptor (RGR) mRNA is transcribed in the outer nuclear layer of human retinas; however, it is not known whether the RGR gene is expressed in the rod or cone photoreceptors. In this study, we investigate broader expression of the normal RGR isoform in photoreceptors of human and bovine retinas. METHODS We produced and validated a rabbit polyclonal antipeptide antibody (DE15) that is directed against a peptide sequence (SSLLRRWPHGSEGC) partly conserved in RGR across several species. Bovine and human retina sections were analyzed with immunohistochemical and double-label immunofluorescent staining. RESULTS The DE15 antibody bound specifically to overexpressed recombinant RGR, purified RGR from bovine RPE, and RGR in crude RPE membrane extracts without cross-reaction to other proteins. Immunostaining of diurnal bovine and human retinas with DE15 showed labeling of long-wavelength-sensitive and short-wavelength-sensitive cone photoreceptors and some retinal ganglion cells in both species. Strong labeling with DE15 was detected throughout the cone photoreceptor, including the outer segment, inner segment, cell body, axon, and cone pedicle, while rod outer segments were negative. Immunostaining for human exon-6-skipping RGR (RGR-d) was found primarily at the tips of the outer segment of the cones. CONCLUSIONS The results indicate that the cone photoreceptors in these mammals express a nonvisual opsin of the Go/RGR or tetraopsin group. RGR and the visual pigments are predominantly colocalized in the cone outer segment, which suggests functional interaction among these opsins. Human cone photoreceptors may also contain normal RGR and the aberrant RGR-d splice isoform.
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Affiliation(s)
- Zhaoxia Zhang
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA,USC Roski Eye Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA
| | - Henry K.W. Fong
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA,Department of Molecular Microbiology and Immunology, Keck School of Medicine of the University of Southern California, Los Angeles, CA,USC Roski Eye Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA
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Campos MM, Abu-Asab MS. Loss of endothelial planar cell polarity and cellular clearance mechanisms in age-related macular degeneration. Ultrastruct Pathol 2017; 41:312-319. [PMID: 28796562 DOI: 10.1080/01913123.2017.1348418] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Apoptosis, autophagosomes, and lysosomes are lacking in the retinal pigment epithelium (RPE) of age-related macular degeneration (AMD) eyes. Necrosis, not apoptosis, appeared to be the prominent type of cell death in RPE, which led to the accumulation of cell debris within and on both sides of Bruch's membrane. The endothelium of the choriocapillaris had an altered planar cell polarity which encompassed the disappearance of fenestrations, the thickening of cytoplasm, and anterior nuclear dislocation. There were no significant differences in RPE and choroidal aberrations between macular and temporal regions. Loss of endothelial polarity could be at the crux of AMD initiation and progression.
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Affiliation(s)
- Maria Mercedes Campos
- a Section of Histopathology , National Eye Institute, NIH , Bethesda , Maryland , USA
| | - Mones S Abu-Asab
- a Section of Histopathology , National Eye Institute, NIH , Bethesda , Maryland , USA
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Gelfand BD, Ambati J. A Revised Hemodynamic Theory of Age-Related Macular Degeneration. Trends Mol Med 2016; 22:656-670. [PMID: 27423265 DOI: 10.1016/j.molmed.2016.06.009] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2016] [Revised: 06/16/2016] [Accepted: 06/16/2016] [Indexed: 12/16/2022]
Abstract
Age-related macular degeneration (AMD) afflicts one out of every 40 individuals worldwide, causing irreversible central blindness in millions. The transformation of various tissue layers within the macula in the retina has led to competing conceptual models of the molecular pathways, cell types, and tissues responsible for the onset and progression of AMD. A model that has persisted for over 6 decades is the hemodynamic, or vascular theory of AMD progression, which states that vascular dysfunction of the choroid underlies AMD pathogenesis. Here, we re-evaluate this hypothesis in light of recent advances on molecular, anatomic, and hemodynamic changes underlying choroidal dysfunction in AMD. We propose an updated, detailed model of hemodynamic dysfunction as a mechanism of AMD development and progression.
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Affiliation(s)
- Bradley D Gelfand
- Department of Ophthalmology and Visual Sciences, University of Kentucky, Lexington, KY, USA; Department of Biomedical Engineering, University of Kentucky, Lexington, KY, USA; Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky, Lexington, KY, USA
| | - Jayakrishna Ambati
- Department of Ophthalmology and Visual Sciences, University of Kentucky, Lexington, KY, USA; Department of Physiology, University of Kentucky, Lexington, KY, USA.
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Kochounian H, Zhang Z, Spee C, Hinton DR, Fong HKW. Targeting of exon VI-skipping human RGR-opsin to the plasma membrane of pigment epithelium and co-localization with terminal complement complex C5b-9. Mol Vis 2016; 22:213-23. [PMID: 27011730 PMCID: PMC4783578] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Accepted: 03/01/2016] [Indexed: 10/26/2022] Open
Abstract
PURPOSE Rare mutations in the human RGR gene lead to autosomal recessive retinitis pigmentosa or dominantly inherited peripapillary choroidal atrophy. Here, we analyze a common exon-skipping isoform of the human retinal G protein-coupled receptor opsin (RGR-d) to determine differences in subcellular targeting between RGR-d and normal RGR and possible association with abnormal traits in the human eye. METHODS The terminal complement complex (C5b-9), vitronectin, CD46, syntaxin-4, and RGR-d were analyzed in human eye tissue from young and old donors or in cultured fetal RPE cells by means of immunofluorescent labeling and high-resolution confocal microscopy or immunohistochemical staining. RESULTS We observed that RGR-d is targeted to the basolateral plasma membrane of the RPE. RGR-d, but not normal RGR, is expressed in cultured human fetal RPE cells in which the protein also trafficks to the plasma membrane. In young donors, the amount of RGR-d protein in the basolateral plasma membrane was much higher than that in the RPE cells of older subjects. In older donor eyes, the level of immunoreactive RGR-d within RPE cells was often low or undetectable, and immunostaining of RGR-d was consistently strongest in extracellular deposits in Bruch's membrane. Double immunofluorescent labeling in the basal deposits revealed significant aggregate and small punctate co-localization of RGR-d with C5b-9 and vitronectin. CONCLUSIONS RGR-d may escape endoplasmic reticulum-associated degradation and in contrast to full-length RGR, traffick to the basolateral plasma membrane, particularly in younger subjects. RGR-d in the plasma membrane indicates that the protein is properly folded, as misfolded membrane proteins cannot otherwise sort to the plasma membrane. The close association of extracellular RGR-d with both vitronectin and C5b-9 suggests a potential role of RGR-d-containing deposits in complement activation.
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Affiliation(s)
| | - Zhaoxia Zhang
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA
- USC Eye Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA
| | - Christine Spee
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA
| | - David R. Hinton
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA
- Department of Pathology, Keck School of Medicine of the University of Southern California, Los Angeles, CA
- USC Eye Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA
| | - Henry K. W. Fong
- Department of Ophthalmology, Keck School of Medicine of the University of Southern California, Los Angeles, CA
- Department of Molecular Microbiology and Immunology, Keck School of Medicine of the University of Southern California, Los Angeles, CA
- USC Eye Institute, Keck School of Medicine of the University of Southern California, Los Angeles, CA
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Biesemeier A, Taubitz T, Julien S, Yoeruek E, Schraermeyer U. Choriocapillaris breakdown precedes retinal degeneration in age-related macular degeneration. Neurobiol Aging 2014; 35:2562-2573. [DOI: 10.1016/j.neurobiolaging.2014.05.003] [Citation(s) in RCA: 190] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2013] [Revised: 04/23/2014] [Accepted: 05/02/2014] [Indexed: 01/21/2023]
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Mullins RF, Johnson MN, Faidley EA, Skeie JM, Huang J. Choriocapillaris vascular dropout related to density of drusen in human eyes with early age-related macular degeneration. Invest Ophthalmol Vis Sci 2011; 52:1606-12. [PMID: 21398287 DOI: 10.1167/iovs.10-6476] [Citation(s) in RCA: 276] [Impact Index Per Article: 21.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Age-related macular degeneration (AMD) is a common, potentially blinding disease characterized by the presence of extracellular deposits beneath the retinal pigment epithelium (RPE). Choroidal vascular changes have also been noted in AMD. This study examined the relationship between the choroidal vasculature and extent of drusen and other sub-RPE deposits, the key pathologic landmarks of AMD. METHODS Sections of the maculas of 45 human eyes (21 early AMD and 24 age-matched control) were evaluated morphometrically. The cross-sectional area of sub-RPE deposits, vascular density, number of CD45+ leukocytes, and number of "ghost vessels" were determined in a masked fashion and evaluated by regression analysis. In addition, the extramacular vascular density either directly beneath drusen or adjacent to drusen was evaluated in a separate set of donor eyes. RESULTS The vascular density of the choriocapillaris showed a trend toward decreasing in association with AMD status. By linear regression analysis, vascular density was inversely associated with sub-RPE deposit density (r(2) = 0.22, P < 0.01). The number of ghost vessels was negatively correlated with vascular density (r(2) = 0.55, P < 0.001) and positively correlated with sub-RPE deposit density (r(2) = 0.57, P < 0.001). In morphologic studies of extramacular solitary drusen, vascular density beneath drusen was found to be 45% lower than adjacent to drusen (P < 0.01). CONCLUSIONS These findings support the concept that microvascular changes are related to the pathogenesis of AMD and suggest that vascular endothelial cell loss occurs in association with sub-RPE deposit formation. Whether microvascular events are a cause or consequence of drusen or other deposit formation remains to be determined.
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Affiliation(s)
- Robert F Mullins
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, Iowa City, Iowa, USA.
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Wang L, Clark ME, Crossman DK, Kojima K, Messinger JD, Mobley JA, Curcio CA. Abundant lipid and protein components of drusen. PLoS One 2010; 5:e10329. [PMID: 20428236 PMCID: PMC2859054 DOI: 10.1371/journal.pone.0010329] [Citation(s) in RCA: 252] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2010] [Accepted: 03/30/2010] [Indexed: 01/24/2023] Open
Abstract
Background Drusen are extracellular lesions characteristic of aging and age-related maculopathy, a major retinal disease of the elderly. We determined the relative proportions of lipids and proteins in drusen capped with retinal pigment epithelium (RPE) and in RPE isolated from non-macular regions of 36 human retinas with grossly normal maculas obtained <6 hr after death. Methodology/Principal Findings Druse pellets were examined by light and electron microscopy. Component proteins were extracted using novel methods for preserved tissues, separated, subjected to tryptic digestion and LC-MS(MS)2 analysis using an ion trap mass spectrometer, and identified with reference to databases. Lipid classes were separated using thin layer chromatography and quantified by densitometry. Major druse components were esterified cholesterol (EC), phosphatidylcholine (PC), and protein (37.5±13.7, 36.9±12.9, and 43.0±11.5 ng/druse, respectively). Lipid-containing particles (median diameter, 77 nm) occupied 37–44% of druse volume. Major proteins include vitronectin, complement component 9, apoE, and clusterin, previously seen in drusen, and ATP synthase subunit β, scavenger receptor B2, and retinol dehydrogenase 5, previously seen in RPE. Drusen and RPE had similar protein profiles, with higher intensities and greater variability in drusen. C8, part of the complement membrane attack complex, was localized in drusen by immunofluorescence. Conclusions/Significance At least 40% of druse content is comprised by lipids dominated by EC and PC, 2 components that are potentially accounted for by just one pathway, the secretion of lipoproteins by RPE. Manipulating genes encoding apolipoprotein pathways would be a fruitful approach to producing drusen with high EC content in laboratory animals. Therapies that directly mitigate drusen should prepare for the substantial volume of neutral lipids. The catalog of major druse proteins is nearing completion.
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Affiliation(s)
- Lan Wang
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Mark E. Clark
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - David K. Crossman
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Kyoko Kojima
- Department of Epidemiology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Jeffrey D. Messinger
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - James A. Mobley
- Department of Surgery, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
| | - Christine A. Curcio
- Department of Ophthalmology, University of Alabama at Birmingham, Birmingham, Alabama, United States of America
- * E-mail:
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