1
|
Getz TE, Chrenek MA, Papania JT, Shelton DA, Markand S, Iuvone PM, Kozmik Z, Boatright JH, Nickerson JM. Conditional Knockouts of Interphotoreceptor Retinoid Binding Protein Suggest Two Independent Mechanisms for Retinal Degeneration and Myopia. Invest Ophthalmol Vis Sci 2024; 65:32. [PMID: 38904640 PMCID: PMC11193143 DOI: 10.1167/iovs.65.6.32] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Accepted: 06/03/2024] [Indexed: 06/22/2024] Open
Abstract
Purpose Interphotoreceptor retinoid-binding protein's (IRBP) role in eye growth and its involvement in cell homeostasis remain poorly understood. One hypothesis proposes early conditional deletion of the IRBP gene could lead to a myopic response with retinal degeneration, whereas late conditional deletion (after eye size is determined) could cause retinal degeneration without myopia. Here, we sought to understand if prior myopia was required for subsequent retinal degeneration in the absence of IRBP. This study investigates if any cell type or developmental stage is more important in myopia or retinal degeneration. Methods IBRPfl/fl mice were bred with 5 Cre-driver lines: HRGP-Cre, Chx10-Cre, Rho-iCre75, HRGP-Cre Rho-iCre75, and Rx-Cre. Mice were analyzed for IRBP gene expression through digital droplet PCR (ddPCR). Young adult (P30) mice were tested for retinal degeneration and morphology using spectral-domain optical coherence tomography (SD-OCT) and hematoxylin and eosin (H&E) staining. Function was analyzed using electroretinograms (ERGs). Eye sizes and axial lengths were compared through external eye measurements and whole eye biometry. Results Across all outcome measures, when bred to IRBPfl/fl, HRGP-Cre and Chx10-Cre lines showed no differences from IRBPfl/fl alone. With the Rho-iCre75 line, small but significant reductions were seen in retinal thickness with SD-OCT imaging and postmortem H&E staining without increased axial length. Both the HRGP-Cre+Rho-iCre75 and the Rx-Cre lines showed significant decreases in retinal thickness and outer nuclear layer cell counts. Using external eye measurements and SD-OCT imaging, both lines showed an increase in eye size. Finally, function in both lines was roughly halved across scotopic, photopic, and flicker ERGs. Conclusions Our studies support hypotheses that for both eye size determination and retinal homeostasis, there are two critical timing windows when IRBP must be expressed in rods or cones to prevent myopia (P7-P12) and degeneration (P21 and later). The rod-specific IRBP knockout (Rho-iCre75) showed significant retinal functional losses without myopia, indicating that the two phenotypes are independent. IRBP is needed for early development of photoreceptors and eye size, whereas Rho-iCre75 IRBPfl/fl knockout results in retinal degeneration without myopia.
Collapse
Affiliation(s)
- Tatiana E. Getz
- Emory University, Department of Ophthalmology, Atlanta, Georgia, United States
| | - Micah A. Chrenek
- Emory University, Department of Ophthalmology, Atlanta, Georgia, United States
| | - Jack T. Papania
- Emory University, Department of Ophthalmology, Atlanta, Georgia, United States
| | - Debresha A. Shelton
- Emory University, Department of Ophthalmology, Atlanta, Georgia, United States
| | - Shanu Markand
- Kirksville College of Osteopathic Medicine, A.T. Still University, Kirksville, Missouri, United States
| | - P. Michael Iuvone
- Emory University, Department of Ophthalmology, Atlanta, Georgia, United States
| | - Zbynek Kozmik
- Institute of Molecular Genetics of the ASCR, Prague, Czech Republic
| | - Jeffrey H. Boatright
- Emory University, Department of Ophthalmology, Atlanta, Georgia, United States
- Atlanta Veterans Administration Center for Visual and Neurocognitive Rehabilitation, Decatur, Georgia, United States
| | - John M. Nickerson
- Emory University, Department of Ophthalmology, Atlanta, Georgia, United States
| |
Collapse
|
2
|
Castellini ME, Spagnolli G, Poggi L, Biasini E, Casarosa S, Messina A. Identification of the zebrafish homologues of IMPG2, a retinal proteoglycan. Cell Tissue Res 2023; 394:93-105. [PMID: 37470839 PMCID: PMC10558372 DOI: 10.1007/s00441-023-03808-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Accepted: 07/05/2023] [Indexed: 07/21/2023]
Abstract
Photoreceptor outer segments are surrounded by a carbohydrate-rich matrix, the interphotoreceptor matrix, necessary for physiological retinal function. Few roles for molecules characterizing the interphotoreceptor matrix have been clearly defined. Recent studies have found the presence of nonsense mutations in the interphotoreceptor matrix proteoglycan 2 (IMPG2) gene in patients affected by retinal dystrophies. IMPG2 encodes for a proteoglycan synthesized by photoreceptors and secreted in the interphotoreceptor matrix. Little is known about the structure and function of this protein, we thus decided to characterize zebrafish impg2. In zebrafish there are two Impg2 proteins, Impg2a and Impg2b. We generated a phylogenetic tree based on IMPG2 protein sequence similarity among vertebrates, showing a significant similarity between humans and teleosts. The human and zebrafish proteins share conserved domains, as also shown by homology models. Expression analyses of impg2a and impg2b show a continued expression in the photoreceptor layer starting from developmental stages and continuing through adulthood. Between 1 and 6 months post-fertilization, there is a significant shift of Impg2 expression toward the outer segment region, suggesting an increase in secretion. This raises intriguing hypotheses about its possible role(s) during retinal maturation, laying the groundwork for the generation of most needed models for the study of IMPG2-related inherited retinal dystrophies.
Collapse
Affiliation(s)
- M E Castellini
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Via Sommarive, 9, 38123, Povo, TN, Italy
| | - G Spagnolli
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Via Sommarive, 9, 38123, Povo, TN, Italy
- Sibylla Biotech S.R.L, Piazzetta Chiavica 2 - 37121, Verona, VR, Italy
| | - L Poggi
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Via Sommarive, 9, 38123, Povo, TN, Italy
- Centre for Medical Sciences (CISMed), University of Trento, Via S. Maria Maddalena, 1, 38122, Trento, TN, Italy
| | - E Biasini
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Via Sommarive, 9, 38123, Povo, TN, Italy
- Centre for Medical Sciences (CISMed), University of Trento, Via S. Maria Maddalena, 1, 38122, Trento, TN, Italy
| | - S Casarosa
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Via Sommarive, 9, 38123, Povo, TN, Italy.
- Centre for Medical Sciences (CISMed), University of Trento, Via S. Maria Maddalena, 1, 38122, Trento, TN, Italy.
| | - A Messina
- Department of Cellular, Computational and Integrative Biology (CIBIO), University of Trento, Via Sommarive, 9, 38123, Povo, TN, Italy
- Centre for Mind/Brain Sciences (CIMeC), University of Trento, Piazza Manifattura 1, 38068, Rovereto, TN, Italy
| |
Collapse
|
3
|
Zhang X, Sun Y, Meng L, Ye C, Han H, Zhang T, Feng Y, Li J, Duan L, Chen Y. Whole-exome sequencing analysis identifies novel variants associated with Kawasaki disease susceptibility. Pediatr Rheumatol Online J 2023; 21:78. [PMID: 37550746 PMCID: PMC10405421 DOI: 10.1186/s12969-023-00857-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 07/04/2023] [Indexed: 08/09/2023] Open
Abstract
BACKGROUND Kawasaki disease (KD) is an acute pediatric vasculitis affecting genetically susceptible infants and children. Although the pathogenesis of KD remains unclear, growing evidence links genetic susceptibility to the disease. METHODS To explore the genes associated with susceptibility in KD, we applied whole-exome sequencing to KD and control subjects from Yunnan province, China. We conducted association study analysis on the two groups. RESULTS In this study, we successfully identified 11 significant rare variants in two genes (MYH14 and RBP3) through the genotype/allele frequency analysis. A heterozygous variant (c.2650G > A, p.V884M) of the RBP3 gene was identified in 12 KD cases, while eight heterozygous variants (c.566G > A, p.R189H; c.1109 C > T, p.S370L; c.3917T > G, p.L1306R; c.4301G > A, p.R1434Q; c.5026 C > T, p.R1676W; c.5329 C > T, p.R1777C; c.5393 C > A, p.A1798D and c.5476 C > T, p.R1826C) of the MYH14 gene were identified in 8 KD cases respectively. CONCLUSION This study suggested that nine variants in MYH14 and RBP3 gene may be associated with KD susceptibility in the population from Yunnan province.
Collapse
Affiliation(s)
- Xing Zhang
- Department of Cardiology, Kunming Children's Hospital, Yunnan Province Clinical Research Center for Children's Health and Disease, Yunnan, China
| | - Ying Sun
- Department of Cardiology, Kunming Children's Hospital, Yunnan Province Clinical Research Center for Children's Health and Disease, Yunnan, China
| | - Lijuan Meng
- Department of Cardiology, Kunming Children's Hospital, Yunnan Province Clinical Research Center for Children's Health and Disease, Yunnan, China
| | - Caixia Ye
- Maternity and Child health care Hospital of Yunyang County, Chongqing, China
| | | | - Tiesong Zhang
- Department of Cardiology, Kunming Children's Hospital, Yunnan Province Clinical Research Center for Children's Health and Disease, Yunnan, China
| | - Yue Feng
- Kunming University of Science and Technology, Kunming, China
| | - Jianxiao Li
- Department of Cardiology, Kunming Children's Hospital, Yunnan Province Clinical Research Center for Children's Health and Disease, Yunnan, China
| | - Lifen Duan
- Department of Cardiology, Kunming Children's Hospital, Yunnan Province Clinical Research Center for Children's Health and Disease, Yunnan, China.
| | - Yanfei Chen
- Department of Cardiology, Kunming Children's Hospital, Yunnan Province Clinical Research Center for Children's Health and Disease, Yunnan, China.
| |
Collapse
|
4
|
DeRamus ML, Jasien JV, Eppstein JM, Koala P, Kraft TW. Retinal Responses to Visual Stimuli in Interphotoreceptor Retinoid Binding-Protein Knock-Out Mice. Int J Mol Sci 2023; 24:10655. [PMID: 37445836 PMCID: PMC10341985 DOI: 10.3390/ijms241310655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 06/07/2023] [Accepted: 06/20/2023] [Indexed: 07/15/2023] Open
Abstract
Interphotoreceptor retinoid-binding protein (IRBP) is an abundant glycoprotein in the subretinal space bound by the photoreceptor (PR) outer segments and the processes of the retinal pigmented epithelium (RPE). IRBP binds retinoids, including 11-cis-retinal and all-trans-retinol. In this study, visual function for demanding visual tasks was assessed in IRBP knock-out (KO) mice. Surprisingly, IRBP KO mice showed no differences in scotopic critical flicker frequency (CFF) compared to wildtype (WT). However, they did have lower photopic CFF than WT. IRBP KO mice had reduced scotopic and photopic acuity and contrast sensitivity compared to WT. IRBP KO mice had a significant reduction in outer nuclear layer (ONL) thickness, PR outer and inner segment, and full retinal thickness (FRT) compared to WT. There were fewer cones in IRBP KO mice. Overall, these results confirm substantial loss of rods and significant loss of cones within 30 days. Absence of IRBP resulted in cone circuit damage, reducing photopic flicker, contrast sensitivity, and spatial frequency sensitivity. The c-wave was reduced and accelerated in response to bright steps of light. This result also suggests altered retinal pigment epithelium activity. There appears to be a compensatory mechanism such as higher synaptic gain between PRs and bipolar cells since the loss of the b-wave did not linearly follow the loss of rods, or the a-wave. Scotopic CFF is normal despite thinning of ONL and reduced scotopic electroretinogram (ERG) in IRBP KO mice, suggesting either a redundancy or plasticity in circuits detecting (encoding) scotopic flicker at threshold even with substantial rod loss.
Collapse
Affiliation(s)
| | | | | | | | - Timothy W. Kraft
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL 35294, USA; (J.V.J.); (J.M.E.); (P.K.)
| |
Collapse
|
5
|
Towards a New Biomarker for Diabetic Retinopathy: Exploring RBP3 Structure and Retinoids Binding for Functional Imaging of Eyes In Vivo. Int J Mol Sci 2023; 24:ijms24054408. [PMID: 36901838 PMCID: PMC10002987 DOI: 10.3390/ijms24054408] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2022] [Revised: 02/10/2023] [Accepted: 02/21/2023] [Indexed: 02/25/2023] Open
Abstract
Diabetic retinopathy (DR) is a severe disease with a growing number of afflicted patients, which places a heavy burden on society, both socially and financially. While there are treatments available, they are not always effective and are usually administered when the disease is already at a developed stage with visible clinical manifestation. However, homeostasis at a molecular level is disrupted before visible signs of the disease are evident. Thus, there has been a constant search for effective biomarkers that could signal the onset of DR. There is evidence that early detection and prompt disease control are effective in preventing or slowing DR progression. Here, we review some of the molecular changes that occur before clinical manifestations are observable. As a possible new biomarker, we focus on retinol binding protein 3 (RBP3). We argue that it displays unique features that make it a very good biomarker for non-invasive, early-stage DR detection. Linking chemistry to biological function and focusing on new developments in eye imaging and two-photon technology, we describe a new potential diagnostic tool that would allow rapid and effective quantification of RBP3 in the retina. Moreover, this tool would also be useful in the future to monitor therapeutic effectiveness if levels of RBP3 are elevated by DR treatments.
Collapse
|
6
|
Mano F, Sugioka K, Kuniyoshi K, Kondo H, Kusaka S. Identification of Interphotoreceptor retinoid-binding protein in the Schisis cavity fluid of a patient with congenital X-linked Retinoschisis. BMC Ophthalmol 2022; 22:14. [PMID: 34991515 PMCID: PMC8740355 DOI: 10.1186/s12886-021-02234-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Accepted: 12/23/2021] [Indexed: 11/10/2022] Open
Abstract
Background This case report describes the surgical outcome in a patient with congenital X-linked retinoschisis (CXLRS) and the results of proteomic analysis of surgically extracted samples from both vitreous and intraschisis cavities by mass spectrometry. Case presentation A 3-month-old boy presented with extensive retinoschisis involving macula and retinal periphery in both eyes. Genetic analysis confirmed retinoschisin 1 mutation (c.554C > T), and an electroretinogram showed significant reduction of b-wave and decreased cone and rod responses, which led to a diagnosis of CXLRS. By performing pars plana vitrectomy, including inner wall retinectomy, clear visual axes with stable retinal conditions and functional vision in both eyes were obtained during the 4 years of follow-up. Proteomic analysis of surgically retrieved fluid from the intraschisis cavity revealed a higher expression of interphotoreceptor retinoid-binding protein (IRBP) than that from the vitreous humor. However, both samples showed equal levels of albumin, transferrin, and pigment epithelium-derived factor. Conclusions Cellular adhesive imperfection in CXLRS may cause IRBP diffusion from the interphotoreceptor matrix, resulting in the strong expression of IRBP in the intraschisis cavity. An impaired retinoid cycle caused by an absence of IRBP in the retina may potentially underlie the pathology of CXLRS. Supplementary Information The online version contains supplementary material available at 10.1186/s12886-021-02234-5.
Collapse
Affiliation(s)
- Fukutaro Mano
- Department of Ophthalmology, Kindai University Faculty of Medicine, Osakasayama, Japan
| | - Koji Sugioka
- Department of Ophthalmology, Kindai University Faculty of Medicine, Osakasayama, Japan. .,Department of Ophthalmology, Kindai University Nara Hospital, 1248-1 Otodacho, Ikoma City, Nara, 630-0293, Japan.
| | - Kazuki Kuniyoshi
- Department of Ophthalmology, Kindai University Faculty of Medicine, Osakasayama, Japan
| | - Hiroyuki Kondo
- Department of Ophthalmology, University of Occupational and Environmental Health, Kitakyushu, Japan
| | - Shunji Kusaka
- Department of Ophthalmology, Kindai University Faculty of Medicine, Osakasayama, Japan
| |
Collapse
|
7
|
Berkowitz BA, Qian H. OCT imaging of rod mitochondrial respiration in vivo. Exp Biol Med (Maywood) 2021; 246:2151-2158. [PMID: 34024141 DOI: 10.1177/15353702211013799] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
There remains a need for high spatial resolution imaging indices of mitochondrial respiration in the outer retina that probe normal physiology and measure pathogenic and reversible conditions underlying loss of vision. Mitochondria are involved in a critical, but somewhat underappreciated, support system that maintains the health of the outer retina involving stimulus-evoked changes in subretinal space hydration. The subretinal space hydration light-dark response is important because it controls the distribution of vision-critical interphotoreceptor matrix components, including anti-oxidants, pro-survival factors, ions, and metabolites. The underlying signaling pathway controlling subretinal space water management has been worked out over the past 30 years and involves cGMP/mitochondria respiration/pH/RPE water efflux. This signaling pathway has also been shown to be modified by disease-generating conditions, such as hypoxia or oxidative stress. Here, we review recent advances in MRI and commercially available OCT technologies that can measure stimulus-evoked changes in subretinal space water content based on changes in the external limiting membrane-retinal pigment epithelium region. Each step within the above signaling pathway can also be interrogated with FDA-approved pharmaceuticals. A highlight of these studies is the demonstration of first-in-kind in vivo imaging of mitochondria respiration of any cell in the body. Future examinations of subretinal space hydration are expected to be useful for diagnosing threats to sight in aging and disease, and improving the success rate when translating treatments from bench-to-bedside.
Collapse
Affiliation(s)
- Bruce A Berkowitz
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, MI 48201, USA
| | - Haohua Qian
- Visual Function Core, National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| |
Collapse
|
8
|
Chen J, Shao Y, Sasore T, Moiseyev G, Zhou K, Ma X, Du Y, Ma JX. Interphotoreceptor Retinol-Binding Protein Ameliorates Diabetes-Induced Retinal Dysfunction and Neurodegeneration Through Rhodopsin. Diabetes 2021; 70:788-799. [PMID: 33334874 PMCID: PMC7897347 DOI: 10.2337/db20-0609] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 12/10/2020] [Indexed: 12/12/2022]
Abstract
Patients with diabetes often experience visual defects before any retinal pathologies are detected. The molecular mechanism for the visual defects in early diabetes has not been elucidated. Our previous study reported that in early diabetic retinopathy (DR), rhodopsin levels were reduced due to impaired 11-cis-retinal regeneration. Interphotoreceptor retinol-binding protein (IRBP) is a visual cycle protein and important for 11-cis-retinal generation. IRBP levels are decreased in the vitreous and retina of DR patients and animal models. To determine the role of IRBP downregulation in the visual defects in early DR, we induced diabetes in transgenic mice overexpressing IRBP in the retina. IRBP overexpression prevented diabetes-induced decline of retinal function. Furthermore, IRBP overexpression also prevented decreases of rhodopsin levels and 11-cis-retinal generation in diabetic mice. Diabetic IRBP transgenic mice also showed ameliorated retinal oxidative stress, inflammation, apoptosis, and retinal degeneration compared with diabetic wild-type mice. These findings suggest that diabetes-induced IRBP downregulation impairs the regeneration of 11-cis-retinal and rhodopsin, leading to retinal dysfunction in early DR. Furthermore, increased 11-cis-retinal-free opsin constitutively activates the phototransduction pathway, leading to increased oxidative stress and retinal neurodegeneration. Therefore, restored IRBP expression in the diabetic retina may confer a protective effect against retinal degeneration in DR.
Collapse
Affiliation(s)
- Jianglei Chen
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Yan Shao
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
- Tianjin Medical University Eye Hospital, Eye Institute & School of Optometry and Ophthalmology, Tianjin, China
| | - Temmy Sasore
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Gennadiy Moiseyev
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Kelu Zhou
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Xiang Ma
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Yanhong Du
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| | - Jian-Xing Ma
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK
- Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK
| |
Collapse
|
9
|
Zeng S, Zhang T, Madigan MC, Fernando N, Aggio-Bruce R, Zhou F, Pierce M, Chen Y, Huang L, Natoli R, Gillies MC, Zhu L. Interphotoreceptor Retinoid-Binding Protein (IRBP) in Retinal Health and Disease. Front Cell Neurosci 2020; 14:577935. [PMID: 33328889 PMCID: PMC7710524 DOI: 10.3389/fncel.2020.577935] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Accepted: 10/21/2020] [Indexed: 02/05/2023] Open
Abstract
Interphotoreceptor retinoid-binding protein (IRBP), also known as retinol binding protein 3 (RBP3), is a lipophilic glycoprotein specifically secreted by photoreceptors. Enriched in the interphotoreceptor matrix (IPM) and recycled by the retinal pigment epithelium (RPE), IRBP is essential for the vision of all vertebrates as it facilitates the transfer of retinoids in the visual cycle. It also helps to transport lipids between the RPE and photoreceptors. The thiol-dependent antioxidant activity of IRBP maintains the delicate redox balance in the normal retina. Thus, its dysfunction is suspected to play a role in many retinal diseases. We have reviewed here the latest research on IRBP in both retinal health and disease, including the function and regulation of IRBP under retinal stress in both animal models and the human retina. We have also explored the therapeutic potential of targeting IRBP in retinal diseases. Although some technical barriers remain, it is possible that manipulating the expression of IRBP in the retina will rescue or prevent photoreceptor degeneration in many retinal diseases.
Collapse
Affiliation(s)
- Shaoxue Zeng
- Save Sight Institute, The University of Sydney, Sydney, NSW, Australia.,Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, China
| | - Ting Zhang
- Save Sight Institute, The University of Sydney, Sydney, NSW, Australia
| | - Michele C Madigan
- Save Sight Institute, The University of Sydney, Sydney, NSW, Australia.,School of Optometry and Vision Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Nilisha Fernando
- The John Curtin School of Medical Research, The Australian National University, Acton, ACT, Australia
| | - Riemke Aggio-Bruce
- The John Curtin School of Medical Research, The Australian National University, Acton, ACT, Australia.,The Australian National University Medical School, The Australian National University, Acton, ACT, Australia
| | - Fanfan Zhou
- Sydney Pharmacy School, The University of Sydney, Sydney, NSW, Australia
| | - Matthew Pierce
- Save Sight Institute, The University of Sydney, Sydney, NSW, Australia
| | - Yingying Chen
- Save Sight Institute, The University of Sydney, Sydney, NSW, Australia.,Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, China
| | - Lianlin Huang
- Save Sight Institute, The University of Sydney, Sydney, NSW, Australia.,School of Optometry and Vision Sciences, University of New South Wales, Sydney, NSW, Australia
| | - Riccardo Natoli
- The John Curtin School of Medical Research, The Australian National University, Acton, ACT, Australia.,The Australian National University Medical School, The Australian National University, Acton, ACT, Australia
| | - Mark C Gillies
- Save Sight Institute, The University of Sydney, Sydney, NSW, Australia
| | - Ling Zhu
- Save Sight Institute, The University of Sydney, Sydney, NSW, Australia
| |
Collapse
|
10
|
Abstract
Patients with diabetes continue to suffer from impaired visual performance before the appearance of overt damage to the retinal microvasculature and later sight-threatening complications. This diabetic retinopathy (DR) has long been thought to start with endothelial cell oxidative stress. Yet newer data surprisingly finds that the avascular outer retina is the primary site of oxidative stress before microvascular histopathology in experimental DR. Importantly, correcting this early oxidative stress is sufficient to restore vision and mitigate the histopathology in diabetic models. However, translating these promising results into the clinic has been stymied by an absence of methods that can measure and optimize anti-oxidant treatment efficacy in vivo. Here, we review imaging approaches that address this problem. In particular, diabetes-induced oxidative stress impairs dark-light regulation of subretinal space hydration, which regulates the distribution of interphotoreceptor binding protein (IRBP). IRBP is a vision-critical, anti-oxidant, lipid transporter, and pro-survival factor. We show how optical coherence tomography can measure subretinal space oxidative stress thus setting the stage for personalizing anti-oxidant treatment and prevention of impactful declines and loss of vision in patients with diabetes.
Collapse
|
11
|
Widjaja-Adhi MAK, Golczak M. The molecular aspects of absorption and metabolism of carotenoids and retinoids in vertebrates. Biochim Biophys Acta Mol Cell Biol Lipids 2019; 1865:158571. [PMID: 31770587 DOI: 10.1016/j.bbalip.2019.158571] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Revised: 11/04/2019] [Accepted: 11/07/2019] [Indexed: 02/08/2023]
Abstract
Vitamin A is an essential nutrient necessary for numerous basic physiological functions, including reproduction and development, immune cell differentiation and communication, as well as the perception of light. To evade the dire consequences of vitamin A deficiency, vertebrates have evolved specialized metabolic pathways that enable the absorption, transport, and storage of vitamin A acquired from dietary sources as preformed retinoids or provitamin A carotenoids. This evolutionary advantage requires a complex interplay between numerous specialized retinoid-transport proteins, receptors, and enzymes. Recent advances in molecular and structural biology resulted in a rapid expansion of our understanding of these processes at the molecular level. This progress opened new avenues for the therapeutic manipulation of retinoid homeostasis. In this review, we summarize current research related to the biochemistry of carotenoid and retinoid-processing proteins with special emphasis on the structural aspects of their physiological actions. This article is part of a Special Issue entitled Carotenoids recent advances in cell and molecular biology edited by Johannes von Lintig and Loredana Quadro.
Collapse
Affiliation(s)
- Made Airanthi K Widjaja-Adhi
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, United States of America
| | - Marcin Golczak
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, United States of America; Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH, United States of America.
| |
Collapse
|
12
|
Zhang T, Gillies M, Wang Y, Shen W, Bahrami B, Zeng S, Zhu M, Yao W, Zhou F, Murray M, Wang K, Zhu L. Simvastatin protects photoreceptors from oxidative stress induced by all-trans-retinal, through the up-regulation of interphotoreceptor retinoid binding protein. Br J Pharmacol 2019; 176:2063-2078. [PMID: 30825184 PMCID: PMC6534793 DOI: 10.1111/bph.14650] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 02/10/2019] [Accepted: 02/14/2019] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND AND PURPOSE Simvastatin is a 3-hydroxy-3-methylglutaryl CoA reductase inhibitor with multiple targets and effects. It protects neurons in the brain, but its protective effects on photoreceptors are unclear. In this study, we evaluated the neuroprotective effect of simvastatin on photoreceptors exposed to stress induced by all-trans-retinal (atRAL). EXPERIMENTAL APPROACH AlamarBlue and LDH assays were used to evaluate the viability and metabolic activity of Y79 cells (a retinoblastoma cell line) exposed to atRAL-induced stress with or without simvastatin pretreatment. Changes in cellular ROS were evaluated using flow cytometry and mitochondrial stress markers JC-1 and HSP60. Changes in levels of two photoreceptor-specific markers, cone-rod homeobox protein (CRX) and interphotoreceptor retinoid binding protein (IRBP), were evaluated with western blot. The results were validated in ex vivo human retinal explants and a mouse model of photoreceptor degeneration. KEY RESULTS Simvastatin improved mitochondrial function, alleviated oxidative stress and up-regulated the photoreceptor-specific markers IRBP and its upstream regulator CRX in Y79 cells and ex vivo human retinal explants under atRAL-induced stress. Simvastatin attenuated photoreceptor degeneration in association with up-regulation of IRBP and CRX expression after knockdown of IRBP in a murine model. CONCLUSION AND IMPLICATIONS Our findings suggest that simvastatin has a novel role in protecting photoreceptors from atRAL-induced stress. Simvastatin treatment resulted in up-regulation of IRBP and its upstream transcription factor CRX in Y79 cells, ex vivo human retinal explants, and murine retinas in vivo. Further studies of simvastatin to treat photoreceptor degeneration are warranted.
Collapse
Affiliation(s)
- Ting Zhang
- Save Sight InstituteThe University of SydneySydneyNew South WalesAustralia
| | - Mark Gillies
- Save Sight InstituteThe University of SydneySydneyNew South WalesAustralia
| | - Ying Wang
- Save Sight InstituteThe University of SydneySydneyNew South WalesAustralia
| | - Weiyong Shen
- Save Sight InstituteThe University of SydneySydneyNew South WalesAustralia
| | - Bobak Bahrami
- Save Sight InstituteThe University of SydneySydneyNew South WalesAustralia
| | - Shaoxue Zeng
- Save Sight InstituteThe University of SydneySydneyNew South WalesAustralia
- Department of Ophthalmology, West China HospitalSichuan UniversityChengduSichuanChina
| | - Meidong Zhu
- Save Sight InstituteThe University of SydneySydneyNew South WalesAustralia
- New South Wales Organ and Tissue Donation ServiceNew South Wales Tissue Bank, Sydney Eye HospitalSydneyNew South WalesAustralia
| | - Wenjuan Yao
- School of PharmacyThe University of SydneySydneyNew South WalesAustralia
- Department of PharmacologyNantong University Medical CollegeNantongJiangsuChina
| | - Fanfan Zhou
- School of PharmacyThe University of SydneySydneyNew South WalesAustralia
| | - Michael Murray
- Discipline of Pharmacology, Faculty of Medicine and HealthThe University of SydneySydneyNew South WalesAustralia
| | - Ke Wang
- Key Laboratory of Nuclear Medicine, Ministry of Health, Jiangsu Key Laboratory of Molecular Nuclear MedicineJiangsu Institute of Nuclear MedicineWuxiJiangsuChina
| | - Ling Zhu
- Save Sight InstituteThe University of SydneySydneyNew South WalesAustralia
| |
Collapse
|
13
|
Nawaz IM, Rezzola S, Cancarini A, Russo A, Costagliola C, Semeraro F, Presta M. Human vitreous in proliferative diabetic retinopathy: Characterization and translational implications. Prog Retin Eye Res 2019; 72:100756. [PMID: 30951889 DOI: 10.1016/j.preteyeres.2019.03.002] [Citation(s) in RCA: 79] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2018] [Revised: 03/26/2019] [Accepted: 03/28/2019] [Indexed: 02/07/2023]
Abstract
Diabetic retinopathy (DR) is one of the leading causes of visual impairment in the working-age population. DR is a progressive eye disease caused by long-term accumulation of hyperglycaemia-mediated pathological alterations in the retina of diabetic patients. DR begins with asymptomatic retinal abnormalities and may progress to advanced-stage proliferative diabetic retinopathy (PDR), characterized by neovascularization or preretinal/vitreous haemorrhages. The vitreous, a transparent gel that fills the posterior cavity of the eye, plays a vital role in maintaining ocular function. Structural and molecular alterations of the vitreous, observed during DR progression, are consequences of metabolic and functional modifications of the retinal tissue. Thus, vitreal alterations reflect the pathological events occurring at the vitreoretinal interface. These events are caused by hypoxic, oxidative, inflammatory, neurodegenerative, and leukostatic conditions that occur during diabetes. Conversely, PDR vitreous can exert pathological effects on the diabetic retina, resulting in activation of a vicious cycle that contributes to disease progression. In this review, we recapitulate the major pathological features of DR/PDR, and focus on the structural and molecular changes that characterize the vitreal structure and composition during DR and progression to PDR. In PDR, vitreous represents a reservoir of pathological signalling molecules. Therefore, in this review we discuss how studying the biological activity of the vitreous in different in vitro, ex vivo, and in vivo experimental models can provide insights into the pathogenesis of PDR. In addition, the vitreous from PDR patients can represent a novel tool to obtain preclinical experimental evidences for the development and characterization of new therapeutic drug candidates for PDR therapy.
Collapse
Affiliation(s)
- Imtiaz M Nawaz
- Department of Molecular and Translational Medicine, University of Brescia, Italy
| | - Sara Rezzola
- Department of Molecular and Translational Medicine, University of Brescia, Italy
| | - Anna Cancarini
- Department of Ophthalmology, University of Brescia, Italy
| | - Andrea Russo
- Department of Ophthalmology, University of Brescia, Italy
| | - Ciro Costagliola
- Department of Medicine and Health Sciences, University of Molise, Campobasso, Italy
| | | | - Marco Presta
- Department of Molecular and Translational Medicine, University of Brescia, Italy.
| |
Collapse
|
14
|
Sjöstedt E, Sivertsson Å, Hikmet Noraddin F, Katona B, Näsström Å, Vuu J, Kesti D, Oksvold P, Edqvist PH, Olsson I, Uhlén M, Lindskog C. Integration of Transcriptomics and Antibody-Based Proteomics for Exploration of Proteins Expressed in Specialized Tissues. J Proteome Res 2018; 17:4127-4137. [DOI: 10.1021/acs.jproteome.8b00406] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Affiliation(s)
- Evelina Sjöstedt
- Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH - Royal Institute of Technology, Stockholm SE 171 21, Sweden
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala SE 752 37, Sweden
| | - Åsa Sivertsson
- Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH - Royal Institute of Technology, Stockholm SE 171 21, Sweden
| | - Feria Hikmet Noraddin
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala SE 752 37, Sweden
| | - Borbala Katona
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala SE 752 37, Sweden
| | - Åsa Näsström
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala SE 752 37, Sweden
| | - Jimmy Vuu
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala SE 752 37, Sweden
| | - Dennis Kesti
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala SE 752 37, Sweden
| | - Per Oksvold
- Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH - Royal Institute of Technology, Stockholm SE 171 21, Sweden
| | - Per-Henrik Edqvist
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala SE 752 37, Sweden
| | - Ingmarie Olsson
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala SE 752 37, Sweden
| | - Mathias Uhlén
- Science for Life Laboratory, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH - Royal Institute of Technology, Stockholm SE 171 21, Sweden
| | - Cecilia Lindskog
- Rudbeck Laboratory, Department of Immunology, Genetics and Pathology, Science for Life Laboratory, Uppsala University, Uppsala SE 752 37, Sweden
| |
Collapse
|
15
|
Tsin A, Betts-Obregon B, Grigsby J. Visual cycle proteins: Structure, function, and roles in human retinal disease. J Biol Chem 2018; 293:13016-13021. [PMID: 30002120 DOI: 10.1074/jbc.aw118.003228] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Here, we seek to summarize the current understanding of the biochemical and molecular events mediated by visual cycle molecules in the eye. The structures and functions of selected visual cycle proteins and their roles in human retinal diseases are also highlighted. Genetic mutations and malfunctions of these proteins provide etiological evidence that many ocular diseases arise from anomalies of retinoid (vitamin A) metabolism and related visual processes. Genetic retinal disorders such as retinitis pigmentosa, Leber's congenital amaurosis, and Stargardt's disease are linked to structural changes in visual cycle proteins. Moreover, recent reports suggest that visual cycle proteins may also play a role in the development of diabetic retinopathy. Basic science has laid the groundwork for finding a cure for many of these blindness-causing afflictions, but much work remains. Some translational research projects have advanced to the clinical trial stage, while many others are still in progress, and more are at the ideas stage and remain yet to be tested. Some examples of these studies are discussed. Recent and future progress in our understanding of the visual cycle will inform intervention strategies to preserve human vision and prevent blindness.
Collapse
Affiliation(s)
- Andrew Tsin
- From the Department of Biomedical Sciences, University of Texas Rio Grande Valley School of Medicine, Edinburg, Texas 78541,
| | - Brandi Betts-Obregon
- From the Department of Biomedical Sciences, University of Texas Rio Grande Valley School of Medicine, Edinburg, Texas 78541
| | - Jeffery Grigsby
- Vision Health Specialties, Midland, Texas 79707.,the College of Optometry, University of Houston, Houston, Texas 77204, and.,the Department of Laboratory Science and Primary Care, School of Health Professions, Texas Tech University Health Science Center, Midland, Texas 79705
| |
Collapse
|
16
|
Malechka VV, Moiseyev G, Takahashi Y, Shin Y, Ma JX. Impaired Rhodopsin Generation in the Rat Model of Diabetic Retinopathy. THE AMERICAN JOURNAL OF PATHOLOGY 2017; 187:2222-2231. [PMID: 28734946 PMCID: PMC5809515 DOI: 10.1016/j.ajpath.2017.06.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/25/2017] [Revised: 06/14/2017] [Accepted: 06/19/2017] [Indexed: 12/11/2022]
Abstract
Diabetic retinopathy is a common complication of diabetes mellitus. Diabetic patients experience functional deficits in dark adaptation, contrast sensitivity, and color perception before microvascular pathologies become apparent. Herein, we evaluated early changes in neural retinal function and in retinoid metabolism in the eye in diabetes. Streptozotocin-induced diabetic rats showed decreased a- and b-wave amplitudes of scotopic and photopic electroretinography responses 4 months after diabetes induction compared to nondiabetic controls. Although Western blot analysis revealed no difference in opsin expression, rhodopsin content was decreased in diabetic retinas, as shown by a difference in absorbance. Consistently, levels of 11-cis-retinal, the chromophore for visual pigments, were significantly lower in diabetic retinas compared to those in controls, suggesting a retinoid deficiency. Among visual cycle proteins, interphotoreceptor retinoid-binding protein and stimulated by retinoic acid 6 protein showed significantly lower levels in diabetic rats than those in nondiabetic controls. Similarly, serum levels of retinol-binding protein 4 and retinoids were significantly lower in diabetic rats. Overall, these results suggest that retinoid metabolism in the eye is impaired in type 1 diabetes, which leads to deficient generation of visual pigments and neural retinal dysfunction in early diabetes.
Collapse
Affiliation(s)
- Volha V Malechka
- Department of Physiology, Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Gennadiy Moiseyev
- Department of Physiology, Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma.
| | - Yusuke Takahashi
- Department of Medicine, Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Younghwa Shin
- Department of Physiology, Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| | - Jian-Xing Ma
- Department of Physiology, Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma
| |
Collapse
|
17
|
Chen C, Adler L, Goletz P, Gonzalez-Fernandez F, Thompson DA, Koutalos Y. Interphotoreceptor retinoid-binding protein removes all- trans-retinol and retinal from rod outer segments, preventing lipofuscin precursor formation. J Biol Chem 2017; 292:19356-19365. [PMID: 28972139 DOI: 10.1074/jbc.m117.795187] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Revised: 09/22/2017] [Indexed: 11/06/2022] Open
Abstract
Interphotoreceptor retinoid-binding protein (IRBP) is a specialized lipophilic carrier that binds the all-trans and 11-cis isomers of retinal and retinol, and this facilitates their transport between photoreceptors and cells in the retina. One of these retinoids, all-trans-retinal, is released in the rod outer segment by photoactivated rhodopsin after light excitation. Following its release, all-trans-retinal is reduced by the retinol dehydrogenase RDH8 to all-trans-retinol in an NADPH-dependent reaction. However, all-trans-retinal can also react with outer segment components, sometimes forming lipofuscin precursors, which after conversion to lipofuscin accumulate in the lysosomes of the retinal pigment epithelium and display cytotoxic effects. Here, we have imaged the fluorescence of all-trans-retinol, all-trans-retinal, and lipofuscin precursors in real time in single isolated mouse rod photoreceptors. We found that IRBP removes all-trans-retinol from individual rod photoreceptors in a concentration-dependent manner. The rate constant for retinol removal increased linearly with IRBP concentration with a slope of 0.012 min-1 μm-1 IRBP also removed all-trans-retinal, but with much less efficacy, indicating that the reduction of retinal to retinol promotes faster clearance of the photoisomerized rhodopsin chromophore. The presence of physiological IRBP concentrations in the extracellular medium resulted in lower levels of all-trans-retinal and retinol in rod outer segments following light exposure. It also prevented light-induced lipofuscin precursor formation, but it did not remove precursors that were already present. These findings reveal an important and previously unappreciated role of IRBP in protecting the photoreceptor cells against the cytotoxic effects of accumulated all-trans-retinal.
Collapse
Affiliation(s)
- Chunhe Chen
- From the Departments of Ophthalmology and Neurosciences, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Leopold Adler
- From the Departments of Ophthalmology and Neurosciences, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Patrice Goletz
- From the Departments of Ophthalmology and Neurosciences, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Federico Gonzalez-Fernandez
- the Departments of Ophthalmology and Pathology, University of Mississippi and G. V. (Sonny) Montgomery Veterans Affairs Medical Centers, Jackson, Mississippi 39216, and
| | - Debra A Thompson
- the Departments of Ophthalmology and Visual Sciences, and Biological Chemistry, University of Michigan School of Medicine, Ann Arbor, Michigan 48105
| | - Yiannis Koutalos
- From the Departments of Ophthalmology and Neurosciences, Medical University of South Carolina, Charleston, South Carolina 29425,
| |
Collapse
|
18
|
Cheng F, He K, Chen ZZ, Zhang B, Wan T, Li JT, Zhang BW, Jiang XL. Phylogeny and systematic revision of the genus Typhlomys (Rodentia, Platacanthomyidae), with description of a new species. J Mammal 2017. [DOI: 10.1093/jmammal/gyx016] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Feng Cheng
- Institute of Health Sciences, Anhui University, Hefei, Anhui 230601, China (FC, BWZ)
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650204, China (FC, KH, ZZC, BZ, TW, XLJ)
| | - Kai He
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650204, China (FC, KH, ZZC, BZ, TW, XLJ)
- Smithsonian Institution, National Museum of Natural History, 1000 Constitution Avenue, NW, Washington, DC 20004, USA (KH)
- The Kyoto University Museum, Kyoto University, Kyoto 606-8501, Japan (KH)
| | - Zhong-Zheng Chen
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650204, China (FC, KH, ZZC, BZ, TW, XLJ)
- Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming 650204, China (ZZC, BZ)
| | - Bin Zhang
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650204, China (FC, KH, ZZC, BZ, TW, XLJ)
- Kunming College of Life Science, University of Chinese Academy of Sciences, Kunming 650204, China (ZZC, BZ)
| | - Tao Wan
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650204, China (FC, KH, ZZC, BZ, TW, XLJ)
| | - Jia-Tang Li
- Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu 610041, China (JTL)
| | - Bao-Wei Zhang
- School of Life Sciences, Anhui University, Hefei, Anhui 230601, China (BWZ)
| | - Xue-Long Jiang
- State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming 650204, China (FC, KH, ZZC, BZ, TW, XLJ)
| |
Collapse
|
19
|
Balaiya S, Zhou Z, Chalam KV. Characterization of Vitreous and Aqueous Proteome in Humans With Proliferative Diabetic Retinopathy and Its Clinical Correlation. PROTEOMICS INSIGHTS 2017; 8:1178641816686078. [PMID: 28469465 PMCID: PMC5398322 DOI: 10.1177/1178641816686078] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 11/06/2016] [Indexed: 12/28/2022]
Abstract
Aims: Proliferative diabetic retinopathy (PDR) is associated with microvascular complications that cause biochemical changes in the human retina and alter the proteome of vitreous humor and aqueous humor (AH). Methods: Human vitreous humor and AH of PDR subjects were collected. Subjects who had surgery for epiretinal membrane or macular hole served as controls. Protein profiles were obtained and analyzed after running the samples on a liquid chromatography-mass spectrometry/mass spectrometry. Results: In vitreous humor, 16 unique proteins were noted in PDR patients, but not in controls. Those were associated mainly with coagulation, complement, and kallikrein-kinin systems. Under coagulation, fibrinogen and prothrombin proteins were more evident and may emphasize the importance of angiogenesis in the development of PDR. Vitreous proteins showed replicative presence in AH too. As for AH samples, we detected 10 proteins found in PDR patients, which were related to transport, coagulation, and inflammatory responses. Conclusions: We found 57 proteins in human vitreous and 39 proteins in AH. Identification of these proteins that are involved in various pathways will be helpful to understand diabetic retinopathy pathogenesis and to develop proteome as a biomarker for PDR.
Collapse
Affiliation(s)
- Sankarathi Balaiya
- Department of Ophthalmology, College of Medicine, University of Florida, Jacksonville, FL, USA
| | - Zimei Zhou
- Department of Ophthalmology, College of Medicine, University of Florida, Jacksonville, FL, USA
| | - Kakarla V Chalam
- Department of Ophthalmology, College of Medicine, University of Florida, Jacksonville, FL, USA
| |
Collapse
|
20
|
Sun D, Sahu B, Gao S, Schur RM, Vaidya AM, Maeda A, Palczewski K, Lu ZR. Targeted Multifunctional Lipid ECO Plasmid DNA Nanoparticles as Efficient Non-viral Gene Therapy for Leber's Congenital Amaurosis. MOLECULAR THERAPY. NUCLEIC ACIDS 2017. [PMID: 28624218 PMCID: PMC5363681 DOI: 10.1016/j.omtn.2017.02.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Development of a gene delivery system with high efficiency and a good safety profile is essential for successful gene therapy. Here we developed a targeted non-viral delivery system using a multifunctional lipid ECO for treating Leber’s congenital amaurosis type 2 (LCA2) and tested this in a mouse model. ECO formed stable nanoparticles with plasmid DNA (pDNA) at a low amine to phosphate (N/P) ratio and mediated high gene transfection efficiency in ARPE-19 cells because of their intrinsic properties of pH-sensitive amphiphilic endosomal escape and reductive cytosolic release (PERC). All-trans-retinylamine, which binds to interphotoreceptor retinoid-binding protein (IRBP), was incorporated into the nanoparticles via a polyethylene glycol (PEG) spacer for targeted delivery of pDNA into the retinal pigmented epithelium. The targeted ECO/pDNA nanoparticles provided high GFP expression in the RPE of 1-month-old Rpe65−/− mice after subretinal injection. Such mice also exhibited a significant increase in electroretinographic activity, and this therapeutic effect continued for at least 120 days. A safety study in wild-type BALB/c mice indicated no irreversible retinal damage following subretinal injection of these targeted nanoparticles. All-trans-retinylamine-modified ECO/pDNA nanoparticles provide a promising non-viral platform for safe and effective treatment of RPE-specific monogenic eye diseases such as LCA2.
Collapse
Affiliation(s)
- Da Sun
- Case Center for Biomolecular Engineering and Department of Biomedical Engineering, School of Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Bhubanananda Sahu
- Department of Ophthalmology and Visual Sciences, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Songqi Gao
- Department of Pharmacology and Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44140, USA
| | - Rebecca M Schur
- Case Center for Biomolecular Engineering and Department of Biomedical Engineering, School of Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Amita M Vaidya
- Case Center for Biomolecular Engineering and Department of Biomedical Engineering, School of Engineering, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Akiko Maeda
- Department of Ophthalmology and Visual Sciences, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA
| | - Krzysztof Palczewski
- Department of Pharmacology and Cleveland Center for Membrane and Structural Biology, School of Medicine, Case Western Reserve University, Cleveland, OH 44140, USA
| | - Zheng-Rong Lu
- Case Center for Biomolecular Engineering and Department of Biomedical Engineering, School of Engineering, Case Western Reserve University, Cleveland, OH 44106, USA.
| |
Collapse
|
21
|
Identification of differentially expressed proteins in retinoblastoma tumors using mass spectrometry-based comparative proteomic approach. J Proteomics 2017; 159:77-91. [PMID: 28232133 DOI: 10.1016/j.jprot.2017.02.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Revised: 01/24/2017] [Accepted: 02/10/2017] [Indexed: 12/17/2022]
Abstract
In India, retinoblastoma is among the top five childhood cancers. Children mostly present with extraocular extension and high risk features that results in unsatisfactory treatment and low survival rate. In addition, lack of potential therapeutic and prognostic targets is another challenge in the management of retinoblastoma. We studied comparative proteome of retinoblastoma patients (HPV positive and negative (n=4 each) and controls (n=4), in order to identify potential retinoblastoma-specific protein targets. 2D-DIGE coupled MALDI-TOF/TOF mass spectrometry identified 39 unique proteins. Highly deregulated proteins were GFAP,RBP3,APOA1,CRYAA,CRABP1,SAG and TF. Gene ontology (Panther 7.0) revealed majority of proteins to be associated with metabolic processes (26%) and catalytic activity (38%). 8 proteins were significantly upregulated in HPV positive vis-a-vis HPV negative cases. Patient group exhibited 12 upregulated and 18 downregulated proteins compared to controls. Pathway and network analysis (IPA software) revealed CTNNB1 as most significantly regulated signalling pathway in HPV positive than HPV negative retinoblastoma. The trends in transcriptional change of 9 genes were consistent with those at proteomic level. The Western blot analysis confirmed the expression pattern of RBP3,GFAP and CRABP1. We suggest GFAP,RBP3,CRABP1,CRYAAA,APOA1 and SAG as prospective targets that could further be explored as potential candidates in therapy and may further assist in studying the disease mechanism. SIGNIFICANCE In this study we evaluated tumor tissue specimens from retinoblastoma patients and identified 39 differentially regulated proteins compared to healthy retina. From these, we propose RBP3, CRABP1, GFAP, CRYAA, APOA1 and SAG as promising proteomic signatures that could further be explored as efficient prognostic and therapeutic targets in retinoblastoma. The present study is not only a contribution to the ongoing endeavour for the discovery of proteomic signatures in retinoblastoma, but, may also act as a starting point for future studies aimed at uncovering novel targets for further therapeutic interventions and improving patient outcomes.
Collapse
|
22
|
Iwona BS. Growth Factors in the Pathogenesis of Retinal Neurodegeneration in Diabetes Mellitus. Curr Neuropharmacol 2017; 14:792-804. [PMID: 27528260 PMCID: PMC5333593 DOI: 10.2174/1570159x14666160813182009] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2015] [Revised: 11/12/2015] [Accepted: 01/06/2015] [Indexed: 12/13/2022] Open
Abstract
Neurodegeneration is an initial process in the development of diabetic retinopathy (DR). High quantities of glutamate, oxidative stress, induction of the renin-angiotensin system (RAS) and elevated levels of RAGE are crucial elements in the retinal neurodegeneration caused by diabetes mellitus. At least, there is emerging proof to indicate that the equilibrium between the neurotoxic and neuroprotective components will affect the state of the retinal neurons. Somatostatin (SST), pigment epithelium-derived factor (PEDF), and erythropoietin (Epo) are endogenous neuroprotective peptides that are decreased in the eye of diabetic persons and play an essential role in retinal homeostasis. On the other hand, insulin-like growth factor 1 (IGF-1), and vascular endothelial growth factor (VEGF) are pivotal proteins which participate in the development of new capillaries and finally cause damage to the retinal neurons. During recent years, our knowledge about the function of growth factors in the pathogenesis of retinal neurodegeneration has increased. However, intensive investigations are needed to clarify the basic processes that contribute to retinal neurodegeneration and its association with damage to the capillary blood vessels. The objective of this review article is to show new insights on the role of neurotransmitters and growth factors in the pathogenesis of diabetic retinopathy. The information contained in this manuscript may provide the basis for novel strategies based on the factors of neurodegeneration to diagnose, prevent and treat DR in its earliest phases.
Collapse
Affiliation(s)
- Ben-Skowronek Iwona
- Department Pediatric Endocrinology and Diabetology, Medical University of Lublin, ul. Prof. A. Gebali 6, 20-093 Lublin, Poland
| |
Collapse
|
23
|
Mutated olfactomedin 1 in the interphotoreceptor matrix of the mouse retina causes functional deficits and vulnerability to light damage. Histochem Cell Biol 2016; 147:453-469. [PMID: 27787612 DOI: 10.1007/s00418-016-1510-z] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/14/2016] [Indexed: 12/24/2022]
Abstract
Olfactomedin 1 (OLFM1) is a secreted glycoprotein and member of the olfactomedin protein family, which is preferentially expressed in various areas throughout the central nervous system. To learn about the functional properties of OLFM1 in the eye, we investigated its localization in the mouse and pig eye. In addition, we analyzed the ocular phenotype of Olfm1 mutant mice in which 52 amino acids were deleted in the central part (M2 region) of OLFM1. OLFM1 was detected in cornea, sclera, retina, and optic nerve of both wild-type and Olfm1 mutant littermates. By immunohistochemistry and double labeling with the lectin peanut agglutinin, OLFM1 was found in the interphotoreceptor matrix (IPM) of mouse and pig retina where it was directly localized to the inner segments of photoreceptors. Western blotting confirmed the presence of the OLFM1 isoforms pancortin 1 (BMY) and pancortin 2 (BMZ) in the IPM. The retinal phenotype of Olfm1 mutant mice did not obviously differ from that of wild-type littermates. In addition, outer nuclear layer (ONL) and total retinal thickness were not different, and the same was true for the area of the optic nerve in cross sections. Functional changes were observed though by electroretinography, which showed significantly lower a- and b-wave amplitudes in Olfm1 mutant mice when compared to age-matched wild-type mice. When light damage experiments were performed as an experimental paradigm of photoreceptor apoptosis, significantly more TUNEL-positive cells were observed in Olfm1 mutant mice 30 h after light exposure. One week after light exposure, the ONL was significantly thinner in Olfm1 mutant mice than in wild-type littermates indicating increased photoreceptor loss. No differences were observed when rhodopsin turnover or ERK1/2 signaling was investigated. We conclude that OLFM1 is a newly identified IPM molecule that serves an important role for photoreceptor homeostasis, which is significantly compromised in the eyes of Olfm1 mutant mice.
Collapse
|
24
|
Lee M, Li S, Sato K, Jin M. Interphotoreceptor Retinoid-Binding Protein Mitigates Cellular Oxidative Stress and Mitochondrial Dysfunction Induced by All-trans-Retinal. Invest Ophthalmol Vis Sci 2016; 57:1553-62. [PMID: 27046120 PMCID: PMC4824376 DOI: 10.1167/iovs.15-18551] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Purpose Point and null mutations in interphotoreceptor retinoid-binding protein (IRBP) cause retinal dystrophy in affected patients and IRBP-deficient mice with unknown mechanism. This study investigated whether IRBP protects cells from damages induced by all-trans-retinal (atRAL), which was increased in the Irbp−/− retina. Methods Wild-type and Irbp−/− mice retinal explants in buffer with or without purified IBRP were exposed to 800 lux light for different times and subjected to retinoid analysis by high-performance liquid chromatography. Purity of IRBP was determined by Coomassie Brilliant Blue staining and immunoblot analysis. Cellular damages induced by atRAL in the presence or absence of IRBP were evaluated in the mouse photoreceptor-derived 661W cells. Cell viability and death were measured by 3-(4,5-dimethyl-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and TUNEL assays. Expression and modification levels of retinal proteins were determined by immunoblot analysis. Intracellular reactive oxygen species (ROS) and nitric oxide (NO) were detected with fluorogenic dyes and confocal microscopy. Mitochondrial membrane potential was analyzed by using JC-1 fluorescent probe and a flow cytometer. Results Content of atRAL in Irbp−/− retinal explants exposed to light for 40 minutes was significantly higher than that in wild-type retinas under the same light conditions. All-trans-retinal caused increase in cell death, tumor necrosis factor activation, and Adam17 upregulation in 661W cells. NADPH oxidase-1 (NOX1) upregulation, ROS generation, NO-mediated protein S-nitrosylation, and mitochondrial dysfunction were also observed in 661W cells treated with atRAL. These cytotoxic effects were significantly attenuated in the presence of IRBP. Conclusions Interphotoreceptor retinoid-binding protein is required for preventing accumulation of retinal atRAL, which causes inflammation, oxidative stress, and mitochondrial dysfunction of the cells.
Collapse
|
25
|
Metabolic and redox signaling in the retina. Cell Mol Life Sci 2016; 74:3649-3665. [PMID: 27543457 PMCID: PMC5597695 DOI: 10.1007/s00018-016-2318-7] [Citation(s) in RCA: 73] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2016] [Revised: 07/21/2016] [Accepted: 07/22/2016] [Indexed: 01/04/2023]
Abstract
Visual perception by photoreceptors relies on the interaction of incident photons from light with a derivative of vitamin A that is covalently linked to an opsin molecule located in a special subcellular structure, the photoreceptor outer segment. The photochemical reaction produced by the photon is optimal when the opsin molecule, a seven-transmembrane protein, is embedded in a lipid bilayer of optimal fluidity. This is achieved in vertebrate photoreceptors by a high proportion of lipids made with polyunsaturated fatty acids, which have the detrimental property of being oxidized and damaged by light. Photoreceptors cannot divide, but regenerate their outer segments. This is an enormous energetic challenge that explains why photoreceptors metabolize glucose through aerobic glycolysis, as cancer cells do. Uptaken glucose produces metabolites to renew that outer segment as well as reducing power through the pentose phosphate pathway to protect photoreceptors against oxidative damage.
Collapse
|
26
|
Ghosh D, Haswell KM, Sprada M, Gonzalez-Fernandez F. Structure of zebrafish IRBP reveals fatty acid binding. Exp Eye Res 2015; 140:149-158. [PMID: 26344741 DOI: 10.1016/j.exer.2015.08.026] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2015] [Revised: 08/22/2015] [Accepted: 08/31/2015] [Indexed: 10/23/2022]
Abstract
Interphotoreceptor retinoid-binding protein (IRBP) has a remarkable role in targeting and protecting all-trans and 11-cis retinol, and 11-cis retinal during the rod and cone visual cycles. Little is known about how the correct retinoid is efficiently delivered and removed from the correct cell at the required time. It has been proposed that different fatty composition at that the outer-segments and retinal-pigmented epithelium have an important role is regulating the delivery and uptake of the visual cycle retinoids at the cell-interphotoreceptor-matrix interface. Although this suggests intriguing mechanisms for the role of local fatty acids in visual-cycle retinoid trafficking, nothing is known about the structural basis of IRBP-fatty acid interactions. Such regulation may be mediated through IRBP's unusual repeating homologous modules, each containing about 300 amino acids. We have been investigating structure-function relationships of Zebrafish IRBP (zIRBP), which has only two tandem modules (z1 and z2), as a model for the more complex four-module mammalian IRBP's. Here we report the first X-ray crystal structure of a teleost IRBP, and the only structure with a bound ligand. The X-ray structure of z1, determined at 1.90 Å resolution, reveals a two-domain organization of the module (domains A and B). A deep hydrophobic pocket with a single bound molecule of oleic acid was identified within the N-terminal domain A. In fluorescence titrations assays, oleic acid displaced all-trans retinol from zIRBP. Our study, which provides the first structure of an IRBP with bound ligand, supports a potential role for fatty acids in regulating retinoid binding.
Collapse
Affiliation(s)
- Debashis Ghosh
- Department of Pharmacology, State University of New York Upstate Medical University, Syracuse, NY, USA.
| | - Karen M Haswell
- Department of Pharmacology, State University of New York Upstate Medical University, Syracuse, NY, USA
| | - Molly Sprada
- SUNY Eye Institute, State University of New York, USA
| | - Federico Gonzalez-Fernandez
- Medical Research & Development Service, G.V. (Sonny) Veterans Affairs Medical Center, Jackson, MS, USA; Departments of Ophthalmology and Pathology, University of Mississippi Medical Center, Jackson, MS, USA; SUNY Eye Institute, State University of New York, USA.
| |
Collapse
|
27
|
Zhu L, Shen W, Lyons B, Wang Y, Zhou F, Gillies MC. Dysregulation of inter-photoreceptor retinoid-binding protein (IRBP) after induced Müller cell disruption. J Neurochem 2015; 133:909-18. [PMID: 25692504 DOI: 10.1111/jnc.13075] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Revised: 02/11/2015] [Accepted: 02/12/2015] [Indexed: 11/29/2022]
Abstract
Reduced expression of a ~150 kDa protein was unexpectedly observed while investigating Norrin protein in a transgenic murine model in which Müller cells can be selectively and inducibly disrupted. Isolation of this unknown protein via ion exchange and hydrophobic interaction chromatography followed by Tandem mass spectrometry identified it as Inter-photoreceptor retinoid-binding protein (IRBP). Significantly reduced IRBP mRNA expression was observed at the early and late stages after Müller cell disruption. IRBP protein expression was also consistently reduced to 5.7% of the control level as early as 1 week after Müller cell disruption. This down-regulation of IRBP was accompanied by focal hyperfluorescent dots and cytotoxic N-retinylidene-N-retinylethanolamine (A2E) accumulation. In vitro treatment of cone photoreceptor cell lines with conditioned medium collected from stressed Müller cells suggested that Müller cells regulated photoreceptors expression of IRBP via secreted factor(s). In vivo studies suggested that one of these secreted factors was tumour necrosis factor alpha (TNFα). These findings suggest that dysregulation of IRBP expression caused by Müller cell dysfunction may be an important early event in photoreceptor degeneration in some retinal diseases. This study reports down-regulation of inter-photoreceptor retinoid-binding protein (IRBP) in photoreceptors and retinoid cycle derangement after Müller cell disruption in a transgenic mouse model. The findings indicate that Müller cells communicate with photoreceptors in response to stress by secreting soluble protein factor(s). We propose that down-regulation of IRBP may represent an early and novel pathogenic mechanism in degenerative retinal diseases.
Collapse
Affiliation(s)
- Ling Zhu
- Save Sight Institute, the University of Sydney, Sydney, NSW, Australia
| | - Weiyong Shen
- Save Sight Institute, the University of Sydney, Sydney, NSW, Australia
| | - Brian Lyons
- Save Sight Institute, the University of Sydney, Sydney, NSW, Australia
| | - Ying Wang
- Save Sight Institute, the University of Sydney, Sydney, NSW, Australia
| | - Fanfan Zhou
- Faculty of Pharmacy, the University of Sydney, Sydney, NSW, Australia
| | - Mark C Gillies
- Save Sight Institute, the University of Sydney, Sydney, NSW, Australia
| |
Collapse
|
28
|
Gonzalez-Fernandez F, Betts-Obregon B, Yust B, Mimun J, Sung D, Sardar D, Tsin AT. Interphotoreceptor retinoid-binding protein protects retinoids from photodegradation. Photochem Photobiol 2015; 91:371-8. [PMID: 25565073 DOI: 10.1111/php.12416] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 12/16/2014] [Indexed: 12/20/2022]
Abstract
Retinol degrades rapidly in light into a variety of photoproducts. It is remarkable that visual cycle retinoids can evade photodegradation as they are exchanged between the photoreceptors, retinal pigment epithelium and Müller glia. Within the interphotoreceptor matrix, all-trans retinol, 11-cis retinol and retinal are bound by interphotoreceptor retinoid-binding protein (IRBP). Apart from its role in retinoid trafficking and targeting, could IRBP have a photoprotective function? HPLC was used to evaluate the ability of IRBP to protect all-trans and 11-cis retinols from photodegradation when exposed to incandescent light (0 to 8842 μW cm(-2)); time periods of 0-60 min, and bIRBP: retinol molar ratios of 1:1 to 1:5. bIRBP afforded a significant prevention of both all-trans and 11-cis retinol to rapid photodegradation. The effect was significant over the entire light intensity range tested, and extended to the bIRBP: retinol ratio 1:5. In view of the continual exposure of the retina to light, and the high oxidative stress in the outer retina, our results suggest IRBP may have an important protective role in the visual cycle by reducing photodegradation of all-trans and 11-cis retinols. This role of IRBP is particularly relevant in the high flux conditions of the cone visual cycle.
Collapse
Affiliation(s)
- Federico Gonzalez-Fernandez
- Medical Research Service, G.V. (Sonny) Montgomery Veterans Affairs Medical Center, Jackson, MS; Departments of Ophthalmology & Pathology, University of Mississippi School of Medicine, Jackson, MS; SUNY Eye Institute, State University of New York, Buffalo, NY
| | | | | | | | | | | | | |
Collapse
|
29
|
Betts-Obregon BS, Gonzalez-Fernandez F, Tsin AT. Interphotoreceptor retinoid-binding protein (IRBP) promotes retinol uptake and release by rat Müller cells (rMC-1) in vitro: implications for the cone visual cycle. Invest Ophthalmol Vis Sci 2014; 55:6265-71. [PMID: 25183762 DOI: 10.1167/iovs.14-14721] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Interphotoreceptor retinoid-binding protein's (IRBP) role in facilitating the exchange of retinoids between rod and cone photoreceptors, RPE, and Müller cells in the visual cycle remains a mystery. Interphotoreceptor retinoid-binding protein's ability to bind the pericellular matrix of the cone outer segment and Müller cell villi suggests a function in all-trans and 11-cis retinol targeted trafficking in the cone visual cycle. We hypothesize that IRBP facilitates delivery and uptake of all-trans retinol to and release of 11-cis retinol from rat Müller cells (rMC-1). METHODS Rat Müller cells were incubated with all-trans retinol and BSA or bovine IRBP (bIRBP). Retinoids in the cell homogenates and conditioned media were analyzed by high performance liquid chromatography (HPLC). RESULTS Cells incubated with 10 μM retinol and BSA had 2100 pmol of all-trans retinol per milligram homogenate protein compared with 3450 pmol when retinol was delivered by bIRBP; these cells also had 450 pmol all-trans retinyl ester per milligram when retinol was delivered by BSA compared with 270 pmol when retinol was delivered by bIRBP. Conditioned media from cells incubated with retinol delivered by BSA did not contain11-cis retinol. However, cells with retinol delivered by bIRBP released 130 pmol/mL of 11-cis retinol into the cell media. Incubation with 5.0 mM deferoxamine (an iron chelator) reduced IRBP-dependent 11-cis retinol retrieval by 60%. CONCLUSIONS Promoting Müller cell uptake of all-trans retinol and release of 11-cis retinol is a previously unrecognized function of IRBP that may be critical to cone function and integrity.
Collapse
Affiliation(s)
- Brandi S Betts-Obregon
- Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, United States
| | - Federico Gonzalez-Fernandez
- Medical Research Service, Veterans Affairs Medical Center, Buffalo, New York, New York, United States Departments of Ophthalmology (Ross Eye Institute) and Pathology & Anatomic Sciences; Graduate Program in Neurosciences, SUNY Eye Institute, State University of New York, Buffalo, New York, United States
| | - Andrew T Tsin
- Department of Biology, The University of Texas at San Antonio, San Antonio, Texas, United States
| |
Collapse
|
30
|
Chen P, Miyake M, Fan Q, Liao J, Yamashiro K, Ikram MK, Chew M, Vithana EN, Khor CC, Aung T, Tai ES, Wong TY, Teo YY, Yoshimura N, Saw SM, Cheng CY. CMPK1 and RBP3 are associated with corneal curvature in Asian populations. Hum Mol Genet 2014; 23:6129-36. [PMID: 24963161 DOI: 10.1093/hmg/ddu322] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Corneal curvature (CC) measures the steepness of the cornea and is an important parameter for clinically diseases such as astigmatism and myopia. Despite the high heritability of CC, only two associated genes have been discovered to date. We performed a three-stage genome-wide association study meta-analysis in 12 660 Asian individuals. Our Stage 1 was done in multiethnic cohorts comprising 7440 individuals, followed by a Stage 2 replication in 2473 Chinese and Stage 3 in 2747 Japanese. The SNP array genotype data were imputed up to the 1000 Genomes Project Phase 1 cosmopolitan panel. The SNP association with the radii of CC was investigated in the linear regression model with the adjustment of age, gender and principal components. In addition to the known genes, MTOR (also known as FRAP1) and PDGFRA, we discovered two novel genes associated with CC: CMPK1 (rs17103186, P = 3.3 × 10(-12)) and RBP3 (rs11204213 [Val884Met], P = 1.1 × 10(-13)). The missense RBP3 SNP, rs11204213, was also associated with axial length (AL) (P = 4.2 × 10(-6)) and had larger effects on both CC and AL compared with other SNPs. The index SNPs at the four indicated loci explained 1.9% of CC variance across the Stages 1 and 2 cohorts, while 33.8% of CC variance was explained by the genome-wide imputation data. We identified two novel genes influencing CC, which are related to either corneal shape or eye size. This study provides additional insights into genetic architecture of corneal shape.
Collapse
Affiliation(s)
- Peng Chen
- Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore 117597, Singapore
| | - Masahiro Miyake
- Department of Ophthalmology, Kyoto University Graduate School of Medicine, Kyoto 6068507, Japan
| | - Qiao Fan
- Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore 117597, Singapore
| | - Jiemin Liao
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore 168751, Singapore, Department of Ophthalmology, National University of Singapore and National University Health System, Singapore 119228, Singapore
| | - Kenji Yamashiro
- Department of Ophthalmology, Kyoto University Graduate School of Medicine, Kyoto 6068507, Japan
| | - Mohammad K Ikram
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore 168751, Singapore, Department of Ophthalmology, National University of Singapore and National University Health System, Singapore 119228, Singapore, Memory Aging & Cognition Centre, National University Health System, Singapore 117597, Singapore
| | - Merywn Chew
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore 168751, Singapore
| | - Eranga N Vithana
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore 168751, Singapore, Department of Ophthalmology, National University of Singapore and National University Health System, Singapore 119228, Singapore, Duke-NUS Graduate Medical School, Singapore 169857, Singapore
| | - Chiea-Chuen Khor
- Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore 117597, Singapore, Department of Ophthalmology, National University of Singapore and National University Health System, Singapore 119228, Singapore, Genome Institute of Singapore, Agency for Science, Technology and Research, Singapore 138672, Singapore, Department of Paediatrics
| | - Tin Aung
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore 168751, Singapore, Department of Ophthalmology, National University of Singapore and National University Health System, Singapore 119228, Singapore
| | - E-Shyong Tai
- Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore 117597, Singapore, Duke-NUS Graduate Medical School, Singapore 169857, Singapore, Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 119228, Singapore
| | - Tien-Yin Wong
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore 168751, Singapore, Department of Ophthalmology, National University of Singapore and National University Health System, Singapore 119228, Singapore, Duke-NUS Graduate Medical School, Singapore 169857, Singapore
| | - Yik-Ying Teo
- Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore 117597, Singapore, Genome Institute of Singapore, Agency for Science, Technology and Research, Singapore 138672, Singapore, NUS Graduate School for Integrative Science and Engineering, Life Sciences Institute, National University of Singapore, Singapore 117456, Singapore and Department of Statistics and Applied Probability, National University of Singapore, Singapore 117546, Singapore
| | - Nagahisa Yoshimura
- Department of Ophthalmology, Kyoto University Graduate School of Medicine, Kyoto 6068507, Japan
| | - Seang-Mei Saw
- Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore 117597, Singapore, Department of Ophthalmology, National University of Singapore and National University Health System, Singapore 119228, Singapore
| | - Ching-Yu Cheng
- Saw Swee Hock School of Public Health, National University of Singapore and National University Health System, Singapore 117597, Singapore, Singapore Eye Research Institute, Singapore National Eye Centre, Singapore 168751, Singapore, Department of Ophthalmology, National University of Singapore and National University Health System, Singapore 119228, Singapore, Duke-NUS Graduate Medical School, Singapore 169857, Singapore,
| |
Collapse
|
31
|
Thiol-dependent antioxidant activity of interphotoreceptor retinoid-binding protein. Exp Eye Res 2014; 120:167-74. [PMID: 24424263 DOI: 10.1016/j.exer.2014.01.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2013] [Revised: 12/27/2013] [Accepted: 01/03/2014] [Indexed: 12/22/2022]
Abstract
Interphotoreceptor retinoid-binding protein (IRBP), which is critical to photoreceptor survival and function, is comprised of homologous tandem modules each ∼300 amino acids, and contains 10 cysteines, possibly 8 as free thiols. Purification of IRBP has historically been difficult due to aggregation, denaturation and precipitation. Our observation that reducing agent 1,4-dithiothreitol dramatically prevents aggregation prompted investigation of possible functions for IRBP's free thiols. Bovine IRBP (bIRBP) was purified from retina saline washes by a combination of concanavalin A, ion exchange and size exclusion chromatography. Antioxidant activity of the purified protein was measured by its ability to inhibit oxidation of 2,2'-azinobis [3-ethylbenzothiazoline-6-sulfonate] by metmyoglobin. Homology modeling predicted the relationship of the retinoid binding sites to cysteine residues. As a free radical scavenger, bIRBP was more active than ovalbumin, thioredoxin, and vitamin E analog Trolox. Alkylation of free cysteines by N-ethylmaleimide inhibited bIRBP's antioxidant activity, but not its ability to bind all-trans retinol. Structural modeling predicted that Cys 1051 is at the mouth of the module 4 hydrophobic ligand-binding site. Its free radical scavenging activity points to a new function for IRBP in defining the redox environment in the subretinal space.
Collapse
|
32
|
Simó R, Hernández C. Neurodegeneration in the diabetic eye: new insights and therapeutic perspectives. Trends Endocrinol Metab 2014; 25:23-33. [PMID: 24183659 DOI: 10.1016/j.tem.2013.09.005] [Citation(s) in RCA: 323] [Impact Index Per Article: 32.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 09/02/2013] [Accepted: 09/27/2013] [Indexed: 11/29/2022]
Abstract
Diabetic retinopathy (DR), one of the leading causes of preventable blindness, has been considered a microcirculatory disease of the retina. However, there is emerging evidence to suggest that retinal neurodegeneration is an early event in the pathogenesis of DR, which participates in the development of microvascular abnormalities. Therefore, the study of the underlying mechanisms leading to neurodegeneration and the identification of the mediators in the crosstalk between neurodegeneration and microangiopathy will be essential for the development of new therapeutic strategies. In this review, an updated discussion of the mechanisms involved in neurodegeneration, as well as the link between neurodegeneration and microangiopathy, is presented. Finally, the therapeutic implications and new perspectives based on identifying those patients with retinal neurodegeneration are given.
Collapse
Affiliation(s)
- Rafael Simó
- CIBERDEM (CIBER de Diabetes y Enfermedades Metabólicas Asociadas) and Diabetes and Metabolism Research Unit, Vall Hebron Institut de Recerca (VHIR), Universitat Autónoma de Barcelona, 08035 Barcelona, Spain.
| | - Cristina Hernández
- CIBERDEM (CIBER de Diabetes y Enfermedades Metabólicas Asociadas) and Diabetes and Metabolism Research Unit, Vall Hebron Institut de Recerca (VHIR), Universitat Autónoma de Barcelona, 08035 Barcelona, Spain
| | | |
Collapse
|
33
|
Vachali PP, Besch BM, Gonzalez-Fernandez F, Bernstein PS. Carotenoids as possible interphotoreceptor retinoid-binding protein (IRBP) ligands: a surface plasmon resonance (SPR) based study. Arch Biochem Biophys 2013; 539:181-6. [PMID: 23876239 DOI: 10.1016/j.abb.2013.07.008] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Revised: 06/13/2013] [Accepted: 07/05/2013] [Indexed: 12/11/2022]
Abstract
Uptake, transport and stabilization of xanthophylls in the human retina are important components of a complex multistep process that culminates in a non-uniform distribution of these important nutrients in the retina. The process is far from understood; here, we consider the potential role of interphotoreceptor retinoid-binding protein (IRBP) in this process. IRBP is thought to facilitate the exchange of 11-cis-retinal, 11-cis-retinol and all-trans-retinol between the retinal pigment epithelium (RPE), photoreceptors and Müller cells in the visual cycle. Structural and biochemical studies suggest that IRBP has a variety of nonequivalent ligand binding sites that function in this process. IRBP is multifunctional, being able to bind a variety of physiologically significant molecules including fatty acids in the subretinal space. This wide range of binding activities is of particular interest because it is unknown whether the lutein and zeaxanthin found in the macula originate from the choroidal or retinal circulations. If from the choroidal circulation, then IRBP is a likely mediator for their transport across the interphotoreceptor matrix. In this report, we explore the binding interactions of retinoids, fatty acids, and carotenoids with IRBP using surface plasmon resonance (SPR)-based biosensors. IRBP showed similar affinity toward retinoids and carotenoids (1-2 μM), while fatty acids had approximately 10 times less affinity. These results suggest that further studies should be carried out to evaluate whether IRBP has a physiologically relevant role in binding lutein and zeaxanthin in the interphotoreceptor matrix.
Collapse
Affiliation(s)
- Preejith P Vachali
- Moran Eye Center, University of Utah School of Medicine, 65 Mario Capecchi Drive, Salt Lake City, UT 84132, United States
| | | | | | | |
Collapse
|
34
|
Shen B, Fang T, Dai M, Jones G, Zhang S. Independent losses of visual perception genes Gja10 and Rbp3 in echolocating bats (Order: Chiroptera). PLoS One 2013; 8:e68867. [PMID: 23874796 PMCID: PMC3715546 DOI: 10.1371/journal.pone.0068867] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Accepted: 06/04/2013] [Indexed: 11/19/2022] Open
Abstract
A trade-off between the sensory modalities of vision and hearing is likely to have occurred in echolocating bats as the sophisticated mechanism of laryngeal echolocation requires considerable neural processing and has reduced the reliance of echolocating bats on vision for perceiving the environment. If such a trade-off exists, it is reasonable to hypothesize that some genes involved in visual function may have undergone relaxed selection or even functional loss in echolocating bats. The Gap junction protein, alpha 10 (Gja10, encoded by Gja10 gene) is expressed abundantly in mammal retinal horizontal cells and plays an important role in horizontal cell coupling. The interphotoreceptor retinoid-binding protein (Irbp, encoded by the Rbp3 gene) is mainly expressed in interphotoreceptor matrix and is known to be critical for normal functioning of the visual cycle. We sequenced Gja10 and Rbp3 genes in a taxonomically wide range of bats with divergent auditory characteristics (35 and 18 species for Gja10 and Rbp3, respectively). Both genes have became pseudogenes in species from the families Hipposideridae and Rhinolophidae that emit constant frequency echolocation calls with Doppler shift compensation at high-duty-cycles (the most sophisticated form of biosonar known), and in some bat species that emit echolocation calls at low-duty-cycles. Our study thus provides further evidence for the hypothesis that a trade-off occurs at the genetic level between vision and echolocation in bats.
Collapse
Affiliation(s)
- Bin Shen
- Institute of Molecular Ecology and Evolution, Institutes for Advanced Interdisciplinary Research, East China Normal University, Shanghai, China
| | - Tao Fang
- Institute of Molecular Ecology and Evolution, Institutes for Advanced Interdisciplinary Research, East China Normal University, Shanghai, China
| | - Mengyao Dai
- Institute of Molecular Ecology and Evolution, Institutes for Advanced Interdisciplinary Research, East China Normal University, Shanghai, China
| | - Gareth Jones
- School of Biological Sciences, University of Bristol, Bristol, United Kingdom
| | - Shuyi Zhang
- Institute of Molecular Ecology and Evolution, Institutes for Advanced Interdisciplinary Research, East China Normal University, Shanghai, China
| |
Collapse
|
35
|
Vitamin A derivatives as treatment options for retinal degenerative diseases. Nutrients 2013; 5:2646-66. [PMID: 23857173 PMCID: PMC3738993 DOI: 10.3390/nu5072646] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2013] [Revised: 06/05/2013] [Accepted: 06/13/2013] [Indexed: 11/17/2022] Open
Abstract
The visual cycle is a sequential enzymatic reaction for vitamin A, all-trans-retinol, occurring in the outer layer of the human retina and is essential for the maintenance of vision. The central source of retinol is derived from dietary intake of both retinol and pro-vitamin A carotenoids. A series of enzymatic reactions, located in both the photoreceptor outer segment and the retinal pigment epithelium, transform retinol into the visual chromophore 11-cis-retinal, regenerating visual pigments. Retina specific proteins carry out the majority of the visual cycle, and any significant interruption in this sequence of reactions is capable of causing varying degrees of blindness. Among these important proteins are Lecithin:retinol acyltransferase (LRAT) and retinal pigment epithelium-specific 65-kDa protein (RPE65) known to be responsible for esterification of retinol to all-trans-retinyl esters and isomerization of these esters to 11-cis-retinal, respectively. Deleterious mutations in these genes are identified in human retinal diseases that cause blindness, such as Leber congenital amaurosis (LCA) and retinitis pigmentosa (RP). Herein, we discuss the pathology of 11-cis-retinal deficiency caused by these mutations in both animal disease models and human patients. We also review novel therapeutic strategies employing artificial visual chromophore 9-cis-retinoids which have been employed in clinical trials involving LCA patients.
Collapse
|
36
|
Li S, Yang Z, Hu J, Gordon WC, Bazan NG, Haas AL, Bok D, Jin M. Secretory defect and cytotoxicity: the potential disease mechanisms for the retinitis pigmentosa (RP)-associated interphotoreceptor retinoid-binding protein (IRBP). J Biol Chem 2013; 288:11395-406. [PMID: 23486466 PMCID: PMC3630842 DOI: 10.1074/jbc.m112.418251] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Interphotoreceptor retinoid-binding protein (IRBP) secreted by photoreceptors plays a pivotal role in photoreceptor survival and function. Recently, a D1080N mutation in IRBP was found in patients with retinitis pigmentosa, a frequent cause of retinal degeneration. The molecular and cellular bases for pathogenicity of the mutation are unknown. Here, we show that the mutation abolishes secretion of IRBP and results in formation of insoluble high molecular weight complexes via disulfide bonds. Co-expression of protein disulfide isomerase A2 that regulates disulfide bond formation or introduction of double Cys-to-Ala substitutions at positions 304 and 1175 in D1080N IRBP promoted secretion of the mutated IRBP. D1080N IRBP was not transported to the Golgi apparatus, but accumulated in the endoplasmic reticulum (ER), bound with the ER-resident chaperone proteins such as BiP, protein disulfide isomerase, and heat shock proteins. Splicing of X-box-binding protein-1 mRNA, expression of activating transcription factor 4 (ATF4), and cleavage of ATF6 were significantly increased in cells expressing D1080N IRBP. Moreover, D1080N IRBP induced up-regulation and nuclear translocation of the C/EBP homologous protein, a proapoptotic transcription factor associated with the unfolded protein response. These results indicate that loss of normal function (nonsecretion) and gain of cytotoxic function (ER stress) are involved in the disease mechanisms of D1080N IRBP. Chemical chaperones and low temperature, which help proper folding of many mutated proteins, significantly rescued secretion of D1080N IRBP, suggesting that misfolding is the molecular basis for pathogenicity of D1080N substitution and that chemical chaperones are therapeutic candidates for the mutation-caused blinding disease.
Collapse
Affiliation(s)
- Songhua Li
- Department of Ophthalmology, Louisiana State University Health Sciences Center, New Orleans, Louisiana 70112, USA
| | | | | | | | | | | | | | | |
Collapse
|
37
|
Tang PH, Kono M, Koutalos Y, Ablonczy Z, Crouch RK. New insights into retinoid metabolism and cycling within the retina. Prog Retin Eye Res 2012; 32:48-63. [PMID: 23063666 DOI: 10.1016/j.preteyeres.2012.09.002] [Citation(s) in RCA: 86] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2012] [Revised: 09/28/2012] [Accepted: 09/30/2012] [Indexed: 01/05/2023]
Abstract
The retinoid cycle is a series of biochemical reactions within the eye that is responsible for synthesizing the chromophore, 11-cis retinal, for visual function. The chromophore is bound to G-protein coupled receptors, opsins, within rod and cone photoreceptor cells forming the photosensitive visual pigments. Integral to the sustained function of photoreceptors is the continuous generation of chromophore by the retinoid cycle through two separate processes, one that supplies both rods and cones and another that exclusively supplies cones. Recent findings such as RPE65 localization within cones and the pattern of distribution of retinoid metabolites within mouse and human retinas have challenged previous proposed schemes. This review will focus on recent findings regarding the transport of retinoids, the mechanisms by which chromophore is supplied to both rods and cones, and the metabolism of retinoids within the posterior segment of the eye.
Collapse
Affiliation(s)
- Peter H Tang
- Department of Neurosciences, Medical University of South Carolina, Charleston, SC 29425, USA
| | | | | | | | | |
Collapse
|
38
|
Garlipp MA, Nowak KR, Gonzalez-Fernandez F. Cone outer segment extracellular matrix as binding domain for interphotoreceptor retinoid-binding protein. J Comp Neurol 2012; 520:756-69. [PMID: 21935947 DOI: 10.1002/cne.22773] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Cones are critically dependent on interphotoreceptor retinoid-binding protein (IRBP) for retinoid delivery in the visual cycle. Cone-dominant vertebrates offer an opportunity to uncover the molecular basis of IRBP's role in this process. Here, we explore the association of IRBP with the interphotoreceptor matrix (IPM) of cones vs. rods in cone dominant retinas from chicken (Gallus domesticus), turkey (Meleagris gallopavo), and pig (Sus scrofa). Retinas were detached and fixed directly or washed in saline prior to fixation. Disassociated photoreceptors with adherent matrix were also prepared. Under 2 mM CaCl(2) , insoluble matrix was delaminated from saline washed retinas. The distribution of IRBP, as well as glycans binding peanut agglutinin (cone matrix) and wheat germ agglutinin (rod/cone matrix), was defined by confocal microscopy. Retina flat mounts showed IRBP diffusely distributed in an interconnecting, lattice-like pattern throughout the entire matrix. Saline wash replaced this pattern with fluorescent annuli surrounding individual cone outer segments. In isolated cones and matrix sheets, IRBP colocalized with the peanut agglutinin binding matrix glycans. Our results reveal a wash-resistant association of IRBP with a matrix domain immediately surrounding cone outer segments. The cone matrix sheath may be responsible for IRBP-mediated cone targeting of 11-cis retinoids.
Collapse
Affiliation(s)
- Mary Alice Garlipp
- Graduate Program in Neuroscience, School of Medicine and Biomedical Sciences, State University of New York, Buffalo, New York 14209, USA
| | | | | |
Collapse
|
39
|
Albalat R. Evolution of the genetic machinery of the visual cycle: a novelty of the vertebrate eye? Mol Biol Evol 2011; 29:1461-9. [PMID: 22319134 DOI: 10.1093/molbev/msr313] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The discovery in invertebrates of ciliary photoreceptor cells and ciliary (c)-opsins established that at least two of the three elements that characterize the vertebrate photoreceptor system were already present before vertebrate evolution. However, the origin of the third element, a series of biochemical reactions known as the "retinoid cycle," remained uncertain. To understand the evolution of the retinoid cycle, I have searched for the genetic machinery of the cycle in invertebrate genomes, with special emphasis on the cephalochordate amphioxus. Amphioxus is closely related to vertebrates, has a fairly prototypical genome, and possesses ciliary photoreceptor cells and c-opsins. Phylogenetic and structural analyses of the amphioxus sequences related with the vertebrate machinery do not support a function of amphioxus proteins in chromophore regeneration but suggest that the genetic machinery of the retinoid cycle arose in vertebrates due to duplications of ancestral nonvisual genes. These results favor the hypothesis that the retinoid cycle machinery was a functional innovation of the primitive vertebrate eye.
Collapse
Affiliation(s)
- Ricard Albalat
- Departament de Genètica, Universitat de Barcelona, Barcelona, Spain.
| |
Collapse
|
40
|
Kefalov VJ. Rod and cone visual pigments and phototransduction through pharmacological, genetic, and physiological approaches. J Biol Chem 2011; 287:1635-41. [PMID: 22074928 DOI: 10.1074/jbc.r111.303008] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Activation of the visual pigment by light in rod and cone photoreceptors initiates our visual perception. As a result, the signaling properties of visual pigments, consisting of a protein, opsin, and a chromophore, 11-cis-retinal, play a key role in shaping the light responses of photoreceptors. The combination of pharmacological, physiological, and genetic tools has been a powerful approach advancing our understanding of the interactions between opsin and chromophore and how they affect the function of visual pigments. The signaling properties of the visual pigments modulate many aspects of the function of rods and cones, producing their unique physiological properties.
Collapse
Affiliation(s)
- Vladimir J Kefalov
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA.
| |
Collapse
|
41
|
The mammalian cone visual cycle promotes rapid M/L-cone pigment regeneration independently of the interphotoreceptor retinoid-binding protein. J Neurosci 2011; 31:7900-9. [PMID: 21613504 DOI: 10.1523/jneurosci.0438-11.2011] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Rapid regeneration of the visual pigment following its photoactivation is critical for the function of cone photoreceptors throughout the day. Though the reactions of the visual cycle in the retinal pigment epithelium (RPE) that recycle chromophore for rod pigment regeneration are well characterized, the corresponding mechanisms that enable rapid regeneration of cone pigment are poorly understood. A key remaining question is the relative contribution of the recently discovered cone-specific retina visual cycle and the classic RPE-dependent visual cycle to mammalian cone pigment regeneration. In addition, it is not clear what role, if any, the abundant interphotoreceptor retinoid-binding protein (IRBP) presumed to facilitate the traffic of chromophore, plays in accelerating mammalian cone pigment regeneration. To address these issues, we used transretinal recordings to evaluate M/L-cone pigment regeneration in isolated retinas and eyecups from control and IRBP-deficient mice. Remarkably, the mouse retina promoted M/L-cone dark adaptation eightfold faster than the RPE. However, complete cone recovery required both visual cycles. We conclude that the retina visual cycle is critical for the initial rapid regeneration of mouse M/L-cone pigment during dark adaptation, whereas the slower RPE visual cycle is required to complete the process. While the deletion of IRBP reduced the amplitude and slowed the kinetics of mouse M/L-cone photoresponses, cone adaptation in bright, steady light and the kinetics of cone dark adaptation were not affected in isolated retina or in intact eyecup. Thus, IRBP does not accelerate cone pigment regeneration and is not critical for the function of mouse M/L-cones in bright light.
Collapse
|
42
|
Wisard J, Faulkner A, Chrenek MA, Waxweiler T, Waxweiler W, Donmoyer C, Liou GI, Craft CM, Schmid GF, Boatright JH, Pardue MT, Nickerson JM. Exaggerated eye growth in IRBP-deficient mice in early development. Invest Ophthalmol Vis Sci 2011; 52:5804-11. [PMID: 21642628 DOI: 10.1167/iovs.10-7129] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Because interphotoreceptor retinoid-binding protein (IRBP) is expressed before being needed in its presumptive role in the visual cycle, we tested whether it controls eye growth during development. METHODS The eyes of congenic IRBP knockout (KO) and C57BL/6J wild-type (WT) mice ranging in age from postnatal day (P)2 to P440 were compared by histology, laser micrometry, cycloplegic photorefractions, and partial coherence interferometry. RESULTS The size and weight of IRBP KO mouse eyes were greater than those of the WT mouse, even before eye-opening. Excessive ocular enlargement started between P7 and P10, with KO retinal arc lengths becoming greater compared with WT from P10 through P30 (18%; P < 0.01). The outer nuclear layer (ONL) of KO retinas became 20% thinner between P12 to P25, and progressed to 38% thinner at P30. At P30, there were 30% fewer cones per vertical section in KO than in WT retinas. Bromodeoxyuridine (BrdU) labeling indicated the same number of retinal cells were born in KO and WT mice. A spike in apoptosis was observed in KO outer nuclear layer at P25. These changes in size were accompanied by a large decrease in hyperopic refractive error, which reached -4.56 ± 0.70 diopters (D) versus +9.98 ± 0.993 D (mean ± SD) in WT, by postnatal day 60 (P60). CONCLUSIONS; In addition to its role in the visual cycle, IRBP is needed for normal eye development. How IRBP mediates ocular development is unknown.
Collapse
Affiliation(s)
- Jeffrey Wisard
- Department of Ophthalmology, Emory University, Atlanta, Georgia 30322, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
43
|
Interphotoreceptor retinoid-binding protein as the physiologically relevant carrier of 11-cis-retinol in the cone visual cycle. J Neurosci 2011; 31:4714-9. [PMID: 21430170 DOI: 10.1523/jneurosci.3722-10.2011] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cones function in constant light and are responsible for mediating daytime human vision. Like rods, cones use the photosensitive molecule 11-cis-retinal to detect light, and in constant illumination, a continuous supply of 11-cis-retinal is needed. A retina visual cycle is thought to provide a privileged supply of 11-cis-retinal to cones by using 11-cis-retinol generated in Müller cells. In the cycle, 11-cis-retinol is transported from Müller cells to cone inner segments, where it is oxidized to 11-cis-retinal. This oxidation step is only performed in cones, thus rendering the cycle cone-specific. Interphotoreceptor retinoid-binding protein (IRBP) is a retinoid-binding protein in the subretinal space that binds 11-cis-retinol endogenously. Cones in Irbp(-/-) mice are retinoid-deficient under photopic conditions, and it is possible that 11-cis-retinol supplies are disrupted in the absence of IRBP. We tested the hypothesis that IRBP facilitates the delivery of 11-cis-retinol to cones by preserving the isomeric state of 11-cis-retinol in light. With electrophysiology, we show that the cone-like photoreceptors of Nrl(-/-) mice use the cone visual cycle similarly to wild-type cones. Then, using oxidation assays in isolated Nrl(-/-)Rpe65(-/-) retinas, we show that IRBP delivers 11-cis-retinol for oxidation in cones and improves the efficiency of the oxidation reaction. Finally, we show that IRBP protects the isomeric state of 11-cis-retinol in the presence of light. Together, these findings suggest that IRBP plays an important role in the delivery of 11-cis-retinol to cones and can facilitate cone function in the presence of light.
Collapse
|
44
|
The retinal pigment epithelium: something more than a constituent of the blood-retinal barrier--implications for the pathogenesis of diabetic retinopathy. J Biomed Biotechnol 2010; 2010:190724. [PMID: 20182540 PMCID: PMC2825554 DOI: 10.1155/2010/190724] [Citation(s) in RCA: 293] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2009] [Revised: 09/28/2009] [Accepted: 11/16/2009] [Indexed: 12/27/2022] Open
Abstract
The retinal pigment epithelium (RPE) is an specialized epithelium lying in the interface between the neural retina and the choriocapillaris where it forms the outer blood-retinal barrier (BRB). The main functions of the RPE are the following: (1) transport of nutrients, ions, and water, (2) absorption of light and protection against photooxidation, (3) reisomerization of all-trans-retinal into 11-cis-retinal, which is crucial for the visual cycle, (4) phagocytosis of shed photoreceptor membranes, and (5) secretion of essential factors for the structural integrity of the retina. An overview of these functions will be given. Most of the research on the physiopathology of diabetic retinopathy has been focused on the impairment of the neuroretina and the breakdown of the inner BRB. By contrast, the effects of diabetes on the RPE and in particular on its secretory activity have received less attention. In this regard, new therapeutic strategies addressed to modulating RPE impairment are warranted.
Collapse
|
45
|
Abstract
The morphology and molecular mechanisms of animal photoreceptor cells and eyes reveal a complex pattern of duplications and co-option of genetic modules, leading to a number of different light-sensitive systems that share many components, in which clear-cut homologies are rare. On the basis of molecular and morphological findings, I discuss the functional requirements for vision and how these have constrained the evolution of eyes. The fact that natural selection on eyes acts through the consequences of visually guided behaviour leads to a concept of task-punctuated evolution, where sensory systems evolve by a sequential acquisition of sensory tasks. I identify four key innovations that, one after the other, paved the way for the evolution of efficient eyes. These innovations are (i) efficient photopigments, (ii) directionality through screening pigment, (iii) photoreceptor membrane folding, and (iv) focusing optics. A corresponding evolutionary sequence is suggested, starting at non-directional monitoring of ambient luminance and leading to comparisons of luminances within a scene, first by a scanning mode and later by parallel spatial channels in imaging eyes.
Collapse
Affiliation(s)
- Dan-Eric Nilsson
- Department of Cell and Organism Biology, Lund University, 22362 Lund, Sweden.
| |
Collapse
|
46
|
Garcia-Ramírez M, Hernández C, Villarroel M, Canals F, Alonso MA, Fortuny R, Masmiquel L, Navarro A, García-Arumí J, Simó R. Interphotoreceptor retinoid-binding protein (IRBP) is downregulated at early stages of diabetic retinopathy. Diabetologia 2009; 52:2633-41. [PMID: 19823802 DOI: 10.1007/s00125-009-1548-8] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Accepted: 09/02/2009] [Indexed: 11/24/2022]
Abstract
AIMS/HYPOTHESIS Interphotoreceptor retinoid-binding protein (IRBP) plays a major role in the visual cycle and is essential to the maintenance of photoreceptors. The aim of this study was to determine whether a decrease in IRBP production exists in the early stages of diabetic retinopathy. METHODS Vitreous samples from diabetic patients with proliferative and non-proliferative diabetic retinopathy (PDR, NPDR), and from non-diabetic patients with macular hole (control group) were selected for IRBP quantitative assessment by proteomic analysis (fluorescence-based difference gel electrophoresis) and western blot. Human post mortem eyes (n = 16) from diabetic donors without clinically detectable retinopathy and from non-diabetic donors (n = 16) were used to determine IRBP (also known as RBP3) mRNA levels (RT-PCR) and protein content (western blot and confocal microscopy). Retinal neurodegeneration was assessed by measuring glial fibrillar acidic protein (GFAP) and the apoptotic rate. Y79 human retinoblastoma cells were used to test the effects of glucose, TNF-alpha and IL-1beta on IRBP expression and IRBP levels. RESULTS Intravitreous IRBP concentration was significantly lower in PDR < NPDR < control in proteomic and western blot analysis. IRBP mRNA levels and IRBP protein content were significantly lower in the retinas from diabetic donors than in those from non-diabetic donors. Increased GFAP and a higher degree of apoptosis were observed in diabetic retinas compared with non-diabetic retinas. A dose-dependent downregulation of IRBP mRNA expression and IRBP content was detected with glucose, TNF-alpha and IL-1beta in cultures of Y79 human retinoblastoma cells. CONCLUSIONS/INTERPRETATION Underproduction of IRBP is an early event in the human diabetic retina and is associated with retinal neurodegeneration. The mechanisms leading to this deficit deserve further investigation.
Collapse
Affiliation(s)
- M Garcia-Ramírez
- CIBER for Diabetes and Associated Metabolic Diseases (CIBERDEM), Diabetes and Metabolism Research Unit, Institut de Recerca Hospital Universitari Vall d'Hebron, Universitat Autònoma de Barcelona Pg. Vall d'Hebron 119-129, 08035, Barcelona, Spain
| | | | | | | | | | | | | | | | | | | |
Collapse
|
47
|
Gonzalez-Fernandez F, Bevilacqua T, Lee KI, Chandrashekar R, Hsu L, Garlipp MA, Griswold JB, Crouch RK, Ghosh D. Retinol-binding site in interphotoreceptor retinoid-binding protein (IRBP): a novel hydrophobic cavity. Invest Ophthalmol Vis Sci 2009; 50:5577-86. [PMID: 19608538 DOI: 10.1167/iovs.08-1857] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Interphotoreceptor retinoid-binding protein (IRBP) appears to target and protect retinoids during the visual cycle. X-ray crystallographic studies had noted a betabetaalpha-spiral fold shared with crotonases and C-terminal protein transferases. The shallow cleft formed by the fold was assumed to represent the retinol-binding site. However, a second hydrophobic site consisting of a highly restricted cavity was more recently appreciated during in silico ligand-docking studies. In this study, the ligand-binding environment within the second module of Xenopus IRBP (X2IRBP) is defined. METHODS Pristine recombinant polypeptide corresponding to X2IRBP was expressed in a soluble form and purified to homogeneity without its fusion tag. Phenylalanine was substituted for tryptophan at each of the putative retinol-binding domains (W450F, hydrophobic cavity; W587F, shallow cleft). Binding of 11-cis and all-trans retinol were observed in titrations monitoring retinol fluorescence enhancement, quenching of tryptophan fluorescence, and energy transfer. The effect of oleic acid on retinol binding was also examined. RESULTS A ligand-binding stoichiometry of approximately 1:1 was observed for 11-cis and all-trans with K(d) in the tens of nanomolar range. The substitution mutants showed little effect on retinol binding in titrations after fluorescence enhancement. However, the W450F and not the W587F mutant showed a markedly reduced capacity for fluorescence quenching for both 11-cis and all-trans retinol. Oleic acid inhibited the binding of 11-cis and all-trans retinol in an apparent noncompetitive manner. CONCLUSIONS The binding site for 11-cis and all-trans retinol is a novel hydrophobic cavity that is highly restrictive and probably distinct from the long chain fatty acid-binding site.
Collapse
|
48
|
Park TK, Wu Z, Kjellstrom S, Zeng Y, Bush RA, Sieving PA, Colosi P. Intravitreal delivery of AAV8 retinoschisin results in cell type-specific gene expression and retinal rescue in the Rs1-KO mouse. Gene Ther 2009; 16:916-26. [PMID: 19458650 DOI: 10.1038/gt.2009.61] [Citation(s) in RCA: 115] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
X-linked juvenile retinoschisis (XLRS) is a neurodevelopmental abnormality caused by retinoschisin gene mutations. XLRS is characterized by splitting through the retinal layers and impaired synaptic transmission of visual signals resulting in impaired acuity and a propensity to retinal detachment. Several groups have treated murine retinoschisis models successfully using adeno-associated virus (AAV) vectors. Owing to the fragile nature of XLRS retina, translating this therapy to the clinic may require an alternative to invasive subretinal vector administration. Here we show that all layers of the retinoschisin knockout (Rs1-KO) mouse retina can be transduced efficiently with AAV vectors administered by simple vitreous injection. Retinoschisin expression was restricted to the neuroretina using a new vector that uses a 3.5-kb human retinoschisin promoter and an AAV type 8 capsid. Intravitreal administration to Rs1-KO mice resulted in robust retinoschisin expression with a retinal distribution similar to that observed in wild-type retina, including the expression by the photoreceptors lying deep in the retina. No off-target expression was observed. Rs1-KO mice treated with this vector showed a decrease in the schisis cavities and had improved retinal signaling evaluated by recording the electroretinogram 11-15 weeks after the application.
Collapse
Affiliation(s)
- T K Park
- Section for Translational Research in Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD, USA
| | | | | | | | | | | | | |
Collapse
|
49
|
den Hollander AI, McGee TL, Ziviello C, Banfi S, Dryja TP, Gonzalez-Fernandez F, Ghosh D, Berson EL. A homozygous missense mutation in the IRBP gene (RBP3) associated with autosomal recessive retinitis pigmentosa. Invest Ophthalmol Vis Sci 2008; 50:1864-72. [PMID: 19074801 DOI: 10.1167/iovs.08-2497] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Interphotoreceptor retinoid-binding protein (IRBP) has been considered essential for normal rod and cone function, as it mediates the transport of retinoids between the photoreceptors and the retinal pigment epithelium. This study was performed to determine whether mutations in the IRBP gene (RBP3) are associated with photoreceptor degeneration. METHODS A consanguineous family was ascertained in which four children had autosomal recessive retinitis pigmentosa (RP). Homozygosity mapping performed with SNP microarrays revealed only one homozygous region shared by all four affected siblings. Sequencing of RBP3, contained in this region, was performed in this family and others with recessive RP. Screening was also performed on patients with various other forms of retinal degeneration or malfunction. RESULTS Sequence analysis of RBP3 revealed a homozygous missense mutation (p.Asp1080Asn) in the four affected siblings. The mutation affects a residue that is completely conserved in all four homologous modules of the IRBP protein of vertebrate species and in C-terminal-processing proteases, photosynthesis enzymes found in bacteria, algae, and plants. Based on the previously reported crystal structure of Xenopus IRBP, the authors predict that the Asp1080-mediated conserved salt bridge that appears to participate in scaffolding of the retinol-binding domain is abolished by the mutation. No RBP3 mutations were detected in 395 unrelated patients with recessive or isolate RP or in 680 patients with other forms of hereditary retinal degeneration. CONCLUSIONS Mutations in RBP3 are an infrequent cause of autosomal recessive RP. The mutation Asp1080Asn may alter the conformation of the IRBP protein by disrupting a conserved salt bridge.
Collapse
Affiliation(s)
- Anneke I den Hollander
- Berman-Gund Laboratory for the Study of Retinal Degenerations, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Massachusetts 02114, USA
| | | | | | | | | | | | | | | |
Collapse
|
50
|
Chan A, Lakshminrusimha S, Heffner R, Gonzalez-Fernandez F. Histogenesis of retinal dysplasia in trisomy 13. Diagn Pathol 2007; 2:48. [PMID: 18088410 PMCID: PMC2244598 DOI: 10.1186/1746-1596-2-48] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2007] [Accepted: 12/18/2007] [Indexed: 11/21/2022] Open
Abstract
Background Although often associated with holoprosencephaly, little detail of the histopathology of cyclopia is available. Here, we describe the ocular findings in a case of trisomy 13 to better understand the histogenesis of the rosettes, or tubules, characteristic of the retinal dysplasia associated with this condition. Methods A full pediatric autopsy was performed of a near term infant who died shortly after birth from multiple congenital anomalies including fused facial-midline structures. A detailed histopathological study of the ocular structures was performed. The expression of interphotoreceptor retinoid-binding protein (IRBP), cellular retinal-binding protein (CRALBP), rod opsin, and Sonic Hedgehog (Shh) were studied by immunohistochemistry. Results Holoprosencephaly, and a spectrum of anatomical findings characteristic of Patau's syndrome, were found. Cytogenetic studies demonstrated trisomy 13 [47, XY, +13]. The eyes were fused but contained two developed separate lenses. In contrast, the cornea, and angle structures were hypoplastic, and the anterior chamber had failed to form. The retina showed areas of normally laminated neural retina, whereas in other areas it was replaced by numerous neuronal rosettes. Histological and immunohistochemical studies revealed that the rosettes were composed of differentiated retinal neurons and Müller cell glia. In normally laminated retina, Shh expression was restricted to retinal-ganglion cells, and to a population of neurons in the inner zone of the outer nuclear layer. In contrast, Shh could not be detected in the dysplastic rosettes. Conclusion The histopathology of cyclopia appears to be more complex than what may have been previously appreciated. In fact, the terms "cyclopia" and "synophthalmia" are misnomers as the underlying mechanism is a failure of the eyes to form separately during development. The rosettes found in the dysplastic retina are fundamentally different than those of retinoblastoma, being composed of a variety of differentiated cell types. The dysplastic rosettes are essentially laminated retina failing to establish a polarized orientation, resulting in the formation of tubules. Finally, our findings suggest that defective ganglion cell Shh expression may contribute to the ocular pathology of cyclopia.
Collapse
Affiliation(s)
- Ada Chan
- Department of Pathology, State University of New York, Buffalo, New York, USA.
| | | | | | | |
Collapse
|