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Rutan Woods CT, Makia MS, Lewis TR, Crane R, Zeibak S, Yu P, Kakakhel M, Castillo CM, Arshavsky VY, Naash MI, Al-Ubaidi MR. Downregulation of rhodopsin is an effective therapeutic strategy in ameliorating peripherin-2-associated inherited retinal disorders. Nat Commun 2024; 15:4756. [PMID: 38834544 PMCID: PMC11150396 DOI: 10.1038/s41467-024-48846-5] [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: 08/22/2023] [Accepted: 05/15/2024] [Indexed: 06/06/2024] Open
Abstract
Given the absence of approved treatments for pathogenic variants in Peripherin-2 (PRPH2), it is imperative to identify a universally effective therapeutic target for PRPH2 pathogenic variants. To test the hypothesis that formation of the elongated discs in presence of PRPH2 pathogenic variants is due to the presence of the full complement of rhodopsin in absence of the required amounts of functional PRPH2. Here we demonstrate the therapeutic potential of reducing rhodopsin levels in ameliorating disease phenotype in knockin models for p.Lys154del (c.458-460del) and p.Tyr141Cys (c.422 A > G) in PRPH2. Reducing rhodopsin levels improves physiological function, mitigates the severity of disc abnormalities, and decreases retinal gliosis. Additionally, intravitreal injections of a rhodopsin-specific antisense oligonucleotide successfully enhance the physiological function of photoreceptors and improves the ultrastructure of discs in mutant mice. Presented findings shows that reducing rhodopsin levels is an effective therapeutic strategy for the treatment of inherited retinal degeneration associated with PRPH2 pathogenic variants.
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Affiliation(s)
| | - Mustafa S Makia
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA
| | - Tylor R Lewis
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Ryan Crane
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA
| | - Stephanie Zeibak
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA
| | - Paul Yu
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA
| | - Mashal Kakakhel
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA
| | - Carson M Castillo
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, 27710, USA
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA.
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, TX, 77204, USA.
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2
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Brotherton C, Megaw R. Molecular Mechanisms Governing Sight Loss in Inherited Cone Disorders. Genes (Basel) 2024; 15:727. [PMID: 38927662 PMCID: PMC11202562 DOI: 10.3390/genes15060727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2024] [Revised: 05/28/2024] [Accepted: 05/29/2024] [Indexed: 06/28/2024] Open
Abstract
Inherited cone disorders (ICDs) are a heterogeneous sub-group of inherited retinal disorders (IRDs), the leading cause of sight loss in children and working-age adults. ICDs result from the dysfunction of the cone photoreceptors in the macula and manifest as the loss of colour vision and reduced visual acuity. Currently, 37 genes are associated with varying forms of ICD; however, almost half of all patients receive no molecular diagnosis. This review will discuss the known ICD genes, their molecular function, and the diseases they cause, with a focus on the most common forms of ICDs, including achromatopsia, progressive cone dystrophies (CODs), and cone-rod dystrophies (CORDs). It will discuss the gene-specific therapies that have emerged in recent years in order to treat patients with some of the more common ICDs.
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Affiliation(s)
- Chloe Brotherton
- MRC Human Genetics Unit, Institute of Genetics and Cancer, University of Edinburgh, Crewe Road, Edinburgh EH4 2XU1, UK;
| | - Roly Megaw
- Princess Alexandra Eye Pavilion, NHS Lothian, Chalmers St., Edinburgh EH3 9HA, UK
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3
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Ikelle L, Makia M, Lewis T, Crane R, Kakakhel M, Conley SM, Birtley JR, Arshavsky VY, Al-Ubaidi MR, Naash MI. Comparative study of PRPH2 D2 loop mutants reveals divergent disease mechanism in rods and cones. Cell Mol Life Sci 2023; 80:214. [PMID: 37466729 PMCID: PMC10356684 DOI: 10.1007/s00018-023-04851-3] [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: 01/25/2023] [Revised: 05/10/2023] [Accepted: 06/28/2023] [Indexed: 07/20/2023]
Abstract
Mutations in the photoreceptor-specific tetraspanin gene peripherin-2 (PRPH2) lead to widely varying forms of retinal degeneration ranging from retinitis pigmentosa to macular dystrophy. Both inter- and intra-familial phenotypic heterogeneity has led to much interest in uncovering the complex pathogenic mechanisms of PRPH2-associated disease. Majority of disease-causing mutations in PRPH2 reside in the second intradiscal loop, wherein seven cysteines control protein folding and oligomerization. Here, we utilize knockin models to evaluate the role of three D2 loop cysteine mutants (Y141C, C213Y and C150S), alone or in combination. We elucidated how these mutations affect PRPH2 properties, including oligomerization and subcellular localization, and contribute to disease processes. Results from our structural, functional and molecular studies revealed that, in contrast to our understanding from prior investigations, rods are highly affected by PRPH2 mutations interfering with oligomerization and not merely by the haploinsufficiency associated with these mutations. On the other hand, cones are less affected by the toxicity of the mutant protein and significantly reduced protein levels, suggesting that knockdown therapeutic strategies may sustain cone functionality for a longer period. This observation provides useful data to guide and simplify the current development of effective therapeutic approaches for PRPH2-associated diseases that combine knockdown with high levels of gene supplementation needed to generate prolonged rod improvement.
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Affiliation(s)
- Larissa Ikelle
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA
| | - Mustafa Makia
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA
| | - Tylor Lewis
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA
| | - Ryan Crane
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA
| | - Mashal Kakakhel
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, 73104, USA
| | | | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, NC, USA
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA.
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, 3517 Cullen Blvd. Room 2027, Houston, TX, 77204-5060, USA.
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4
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Bianco L, Arrigo A, Antropoli A, Saladino A, Spiga I, Patricelli MG, Bandello F, Carrera P, Battaglia Parodi M. PRPH2-Associated Retinopathy: Novel Variants and Genotype-Phenotype Correlations. Ophthalmol Retina 2022; 7:450-461. [PMID: 36563963 DOI: 10.1016/j.oret.2022.12.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 12/01/2022] [Accepted: 12/13/2022] [Indexed: 12/25/2022]
Abstract
PURPOSE A broad spectrum of autosomal-dominant inherited retinal diseases (IRDs), ranging from mild macular pattern dystrophy to severe cone-rod degeneration, is associated with PRPH2 variants (peripherinopathies). We present detailed clinical and molecular characterization of patients affected by peripherinopathies, aiming to expand the mutational spectrum, and propose novel genotype-phenotype correlations. DESIGN Observational, retrospective case series. PARTICIPANTS Patients with an IRD related to a molecularly proven PRPH2 variant. METHODS Data from ophthalmic examinations and retinal imaging were collected for each follow-up visit. The standard imaging protocol included OCT, blue-light autofluorescence, near-infrared autofluorescence, and ultra-widefield fundus imaging. Genetic analysis was performed with a genomic approach by next-generation sequencing. MAIN OUTCOME MEASURES Results of ophthalmic examination, retinal imaging, and molecular genetic analysis. RESULTS Overall, a total of 19 patients with an IRD and a (likely) pathogenic PRPH2 variant were identified. Their age at presentation had a median of 48 years, whereas the symptomatic disease onset was in their 30s or 40s in 74% of cases. The median follow-up time was 4 years. Clinically, 6 patients were diagnosed with cone-rod dystrophy and 13 with pattern dystrophy. Among the 13 PRPH2 pathogenic variants identified in our cohort, 7 were missense, 3 nonsense, 2 frame shifting, and 1 splice site. Missense variants in the D2 loop were associated with cone-rod dystrophies and poor visual prognosis, whereas predicted loss-of-function alleles with pattern dystrophies and retention of a good visual function into adulthood. Overall, the following 7 variants were novel and never associated to a clinical phenotype: c.68delT, c.290G>A, c.413T>G, c.642C>G, c.702_706dupCAGTT, c.771_772delinsGA, and c.850C>G. CONCLUSIONS Here, we report the findings of a retrospective case series that provided a detailed clinical and molecular characterization of 19 patients harboring 13 different PRPH2 pathogenic variants, 7 of which were previously unreported, expanding the mutational spectrum of the PRPH2 gene. Loss-of-function variants might be preferentially associated with mild-pattern dystrophies, whereas missense dominant-negative variants might be preferentially associated with severely blinding cone-rod degenerations. Further studies are needed to better define the pathogenetic mechanisms and the functional effects of most variants to allow the development of successful gene therapy. FINANCIAL DISCLOSURE(S) Proprietary or commercial disclosure may be found after the references.
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Affiliation(s)
- Lorenzo Bianco
- Department of Ophthalmology, Vita-Salute San Raffaele University, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Alessandro Arrigo
- Department of Ophthalmology, Vita-Salute San Raffaele University, IRCCS San Raffaele Scientific Institute, Milan, Italy.
| | - Alessio Antropoli
- Department of Ophthalmology, Vita-Salute San Raffaele University, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Andrea Saladino
- Department of Ophthalmology, Vita-Salute San Raffaele University, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Ivana Spiga
- Laboratory of Clinical Genomics, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | | | - Francesco Bandello
- Department of Ophthalmology, Vita-Salute San Raffaele University, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Paola Carrera
- Laboratory of Clinical Genomics, IRCCS San Raffaele Scientific Institute, Milan, Italy; Unit of Genomics for Human Disease Diagnosis, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Maurizio Battaglia Parodi
- Department of Ophthalmology, Vita-Salute San Raffaele University, IRCCS San Raffaele Scientific Institute, Milan, Italy
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5
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Conley SM, McClard CK, Mwoyosvi ML, Alkadhem N, Radojevic B, Klein M, Birch D, Ellis A, Icks SW, Guddanti T, Bennett LD. Delineating the Clinical Phenotype of Patients With the c.629C>G, p.Pro210Arg Mutation in Peripherin-2. Invest Ophthalmol Vis Sci 2022; 63:19. [PMID: 35861669 PMCID: PMC9315069 DOI: 10.1167/iovs.63.8.19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose More than 200 different mutations in peripherin-2 (PRPH2) are associated with multiple subtypes of inherited retinal diseases (IRDs), including retinitis pigmentosa and cone or macular diseases. Our goal was to understand how the poorly characterized PRPH2 mutation p.Pro210Arg (P210R) affects visual function and retinal structure as well as gain insight into the mechanism driving the clinical pathology. Methods Eleven patients had clinical assessments including best-corrected visual acuity (BCVA), full field and multifocal electroretinography (ERG), static (spot size V) and kinetic perimetry (Octopus 900), and dark-adapted chromatic (DAC; Medmont; spot size V) perimetry. Images were acquired with the Optos ultra-wide field camera and spectral-domain optical coherence tomography (SD-OCT). Molecular characteristics of the P210R mutant protein were evaluated in vitro. Results Patients with the P210R mutation had BCVA (Snellen) ranging from 20/15 to 20/80. Perimetry showed a reduction in sensitivity, while ERG findings suggested that cone function was more impaired than rod function. Scotomas were identified corresponding to atrophic retinal lesions. Imaging revealed heterogeneous outer retinal changes such as hyperfluorescent flecks, hypo-autofluorescence (AF) regions of atrophy, and thinning of the photoreceptor layer on SD-OCT. In vitro findings suggested that P210R-Prph2 retains the ability to interact with binding partner Rom1 but abnormally accumulates in the endoplasmic reticulum (ER), suggesting the protein does not fold properly. Conclusions Rod and cone sensitivities were decreased in subjects with the P210R mutation in PRPH2. There was scotomatous vision loss that occurred within the macula, likely due to atrophy that occurs after drusen have formed and have begun to resolve. This suggests that although rod and cone photoreceptors are dependent on PRPH2, preventing blindness in this specific subgroup of patients could involve therapeutics that impede the formation or lifecycle of drusen.
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Affiliation(s)
- Shannon M Conley
- University of Oklahoma Health Sciences Center, Department of Cell Biology, Oklahoma City, Oklahoma, United States
| | - Cynthia K McClard
- University of Oklahoma Health Sciences Center, Department of Ophthalmology, Oklahoma City, Oklahoma, United States.,Dean McGee Eye Institute, Oklahoma City, Oklahoma City, Oklahoma, United States
| | - Maggie L Mwoyosvi
- University of Oklahoma Health Sciences Center, Department of Cell Biology, Oklahoma City, Oklahoma, United States
| | - Niyaf Alkadhem
- University of Oklahoma Health Sciences Center, Department of Ophthalmology, Oklahoma City, Oklahoma, United States
| | - Bojana Radojevic
- University of Oklahoma Health Sciences Center, Department of Ophthalmology, Oklahoma City, Oklahoma, United States
| | - Martin Klein
- Retina Foundation of the Southwest, Dallas, Texas, United States
| | - David Birch
- Retina Foundation of the Southwest, Dallas, Texas, United States
| | - Ashley Ellis
- Dean McGee Eye Institute, Oklahoma City, Oklahoma City, Oklahoma, United States
| | - Sonny W Icks
- Dean McGee Eye Institute, Oklahoma City, Oklahoma City, Oklahoma, United States
| | - Tejesh Guddanti
- University of Oklahoma Health Sciences Center, College of Medicine, Oklahoma City, Oklahoma, United States
| | - Lea D Bennett
- University of Oklahoma Health Sciences Center, Department of Ophthalmology, Oklahoma City, Oklahoma, United States.,Dean McGee Eye Institute, Oklahoma City, Oklahoma City, Oklahoma, United States
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6
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Tebbe L, Sakthivel H, Makia MS, Kakakhel M, Conley SM, Al-Ubaidi MR, Naash MI. Prph2 disease mutations lead to structural and functional defects in the RPE. FASEB J 2022; 36:e22284. [PMID: 35344225 PMCID: PMC10599796 DOI: 10.1096/fj.202101562rr] [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: 10/04/2021] [Revised: 02/28/2022] [Accepted: 03/17/2022] [Indexed: 11/11/2022]
Abstract
Prph2 is a photoreceptor-specific tetraspanin with an essential role in the structure and function of photoreceptor outer segments. PRPH2 mutations cause a multitude of retinal diseases characterized by the degeneration of photoreceptors as well as defects in neighboring tissues such as the RPE. While extensive research has analyzed photoreceptors, less attention has been paid to these secondary defects. Here, we use different Prph2 disease models to evaluate the damage of the RPE arising from photoreceptor defects. In Prph2 disease models, the RPE exhibits structural abnormalities and cell loss. Furthermore, RPE functional defects are observed, including impaired clearance of phagocytosed outer segment material and increased microglia activation. The severity of RPE damage is different between models, suggesting that the different abnormal outer segment structures caused by Prph2 disease mutations lead to varying degrees of RPE stress and thus influence the clinical phenotype observed in patients.
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Affiliation(s)
- Lars Tebbe
- Department of Biomedical Engineering, University of Houston, Houston, Texas, USA
| | - Haarthi Sakthivel
- Department of Biomedical Engineering, University of Houston, Houston, Texas, USA
| | - Mustafa S. Makia
- Department of Biomedical Engineering, University of Houston, Houston, Texas, USA
| | - Mashal Kakakhel
- Department of Biomedical Engineering, University of Houston, Houston, Texas, USA
| | - Shannon M. Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
| | - Muayyad R. Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, Texas, USA
| | - Muna I. Naash
- Department of Biomedical Engineering, University of Houston, Houston, Texas, USA
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7
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Gil CH, Chakraborty D, Vieira CP, Prasain N, Calzi SL, Fortmann SD, Hu P, Banno K, Jamal M, Huang C, Sielski MS, Lin Y, Huang X, Dupont MD, Floyd JL, Prasad R, Longhini ALF, McGill TJ, Chung HM, Murphy MP, Kotton DN, Boulton ME, Yoder MC, Grant MB. Specific mesoderm subset derived from human pluripotent stem cells ameliorates microvascular pathology in type 2 diabetic mice. SCIENCE ADVANCES 2022; 8:eabm5559. [PMID: 35245116 PMCID: PMC8896785 DOI: 10.1126/sciadv.abm5559] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Accepted: 01/11/2022] [Indexed: 06/14/2023]
Abstract
Human induced pluripotent stem cells (hiPSCs) were differentiated into a specific mesoderm subset characterized by KDR+CD56+APLNR+ (KNA+) expression. KNA+ cells had high clonal proliferative potential and specification into endothelial colony-forming cell (ECFCs) phenotype. KNA+ cells differentiated into perfused blood vessels when implanted subcutaneously into the flank of nonobese diabetic/severe combined immunodeficient mice and when injected into the vitreous of type 2 diabetic mice (db/db mice). Transcriptomic analysis showed that differentiation of hiPSCs derived from diabetics into KNA+ cells was sufficient to change baseline differences in gene expression caused by the diabetic status and reprogram diabetic cells to a pattern similar to KNA+ cells derived from nondiabetic hiPSCs. Proteomic array studies performed on retinas of db/db mice injected with either control or diabetic donor-derived KNA+ cells showed correction of aberrant signaling in db/db retinas toward normal healthy retina. These data provide "proof of principle" that KNA+ cells restore perfusion and correct vascular dysfunction in db/db mice.
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Affiliation(s)
- Chang-Hyun Gil
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Department of Surgery, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Dibyendu Chakraborty
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
| | - Cristiano P. Vieira
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
| | - Nutan Prasain
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Astellas Institute for Regenerative Medicine (AIRM), Westborough, MA 01581, USA
| | - Sergio Li Calzi
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
| | - Seth D. Fortmann
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
- Medical Scientist Training Program (MSTP), School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Ping Hu
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
| | - Kimihiko Banno
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Department of Physiology II, Nara Medical University, Kashihara, Nara 634-8521, Japan
| | - Mohamed Jamal
- Center for Regenerative Medicine, Pulmonary Center, and Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA
- Department of Endodontics, Hamdan Bin Mohammed College of Dental Medicine, Mohammed Bin Rashid University of Medicine and Health Sciences, Dubai 00000, UAE
| | - Chao Huang
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
| | - Micheli S. Sielski
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
| | - Yang Lin
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Department of Medicine, Ansary Stem Cell Institute, Weill Cornell Medicine, New York, NY 10021, USA
| | - Xinxin Huang
- Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Zhongshan-Xuhui Hospital and Shanghai Key Laboratory of Medical Epigenetics, Institutes of Biomedical Sciences, Fudan University, Shanghai 310104, China
| | - Mariana D. Dupont
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
| | - Jason L. Floyd
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
| | - Ram Prasad
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
| | - Ana Leda F. Longhini
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
- Flow Cytometry Core Facility, Memorial Sloan Kettering Cancer Center (MSKCC), New York, NY 10065, USA
| | - Trevor J. McGill
- Department of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, OR 97239, USA
| | - Hyung-Min Chung
- Department of Stem Cell Biology, School of Medicine, Konkuk University, Seoul 05029, Republic of Korea
| | - Michael P. Murphy
- Department of Surgery, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Darrell N. Kotton
- Center for Regenerative Medicine, Pulmonary Center, and Department of Medicine, Boston University School of Medicine, Boston, MA 02118, USA
| | - Michael E. Boulton
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
| | - Mervin C. Yoder
- Department of Pediatrics, Indiana University School of Medicine, Indianapolis, IN 46202, USA
- Indiana Center for Regenerative Medicine and Engineering, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Maria B. Grant
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham (UAB), Birmingham, AL 35294, USA
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Choi H, Cloutier A, Lally D. PRPH2-Associated Macular Dystrophy in 4 Family Members with a Novel Mutation. Ophthalmic Genet 2021; 43:235-239. [PMID: 34906036 DOI: 10.1080/13816810.2021.2015790] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Peripherin-2 (PRPH2) gene variants are a well-established cause of multiple inherited maculopathies including central areolar choroidal dystrophy (CACD) and pattern dystrophy. In this familial case study, we present a 63-year-old proband who presented with visual acuity of 20/63 right eye and 20/100 left eye with a complaint of lowered visual acuity in the left eye for unknown duration. Fundus examination presented with unifocal atrophic lesions bilaterally. Multi-modal imaging was obtained and genetic testing (My Retina Tracker; Blueprint Genetics) was performed. The proband was monoallelic for a novel missense mutation within the PRPH2 gene (Arg203Pro) not previously found in the literature or large databases (gnomAD, ClinVar, and HGMD). Subsequent examination of the proband's mother, older sister (65 years old), younger sister (53), and daughter (35) found the novel mutation to segregate with maculopathy ranging from speckled fundus autofluorescence with EZ disruption and RPE attenuation on spectral domain optical coherence tomography to large unifocal atrophic lesions throughout the macula bilaterally. The purpose of this case report is to add to the literature of PRPH2-associated disease by providing a comprehensive fundus examination of a family with autosomal dominant PRPH2-associated maculopathy diagnosed as central areolar choroidal dystrophy and pattern dystrophy.
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Affiliation(s)
- Hanna Choi
- Department of Biology, University of Massachusetts, Amherst, Massachusetts, USA.,New England Retina Consultants, Springfield, Massachusetts, USA
| | - Alan Cloutier
- New England Retina Consultants, Springfield, Massachusetts, USA
| | - David Lally
- New England Retina Consultants, Springfield, Massachusetts, USA.,Department of Surgery, University of Massachusetts Medical School-Baystate, Springfield, Massachusetts, USA
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9
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Ulańczyk Z, Grabowicz A, Mozolewska‐Piotrowska K, Safranow K, Kawa MP, Pałucha A, Krawczyk M, Sikora P, Matczyńska E, Machaliński B, Machalińska A. Genetic factors associated with age-related macular degeneration: identification of a novel PRPH2 single nucleotide polymorphism associated with increased risk of the disease. Acta Ophthalmol 2021; 99:739-749. [PMID: 33354892 DOI: 10.1111/aos.14721] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Accepted: 11/20/2020] [Indexed: 12/17/2022]
Abstract
PURPOSE Age-related macular degeneration (AMD) is associated with multiple environmental and genetic risk factors. Two main risk factors for AMD are variants in the CFH and ARMS2/HTRA1 genes. We investigated over 2000 variants in AMD patients and controls using high-throughput sequencing methods to search for variants associated with AMD. METHODS A total of 296 AMD patients and 100 controls were enrolled in this study. Genetic analysis was performed with the Illumina NextSeq 500 system. RESULTS Multivariate analysis of patients and controls, adjusted for age, sex and smoking status (pack-years), revealed that three SNPs were strong risk factors independently associated with AMD: CFH Y402H, ARMS A69S and PRPH2 c.582-67T>A (rs3818086). The TC genotype in CFH Y402H was associated with 1.90-fold higher odds, and the CC genotype was associated with 5.66-fold higher odds of AMD compared with the TT genotype. The GT genotype in ARMS A69S was associated with 2.40-fold higher odds, and the TT genotype was associated with 6.75-fold higher odds of disease compared with the GG genotype. In the case of rs3818086, the A allele could be considered a 'risk' allele, since AA + TA genotypes were associated with 2.33-fold higher odds of AMD compared with the TT genotype. CONCLUSIONS Although PRPH2 mutations have been previously implicated in various forms of retinal degeneration, to the best of our knowledge, this study is the first to show that the rs3818086 variant increases the risk for AMD more than two times. Further studies on larger cohorts are required to elucidate how this variant affects protein structure.
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Affiliation(s)
- Zofia Ulańczyk
- Department of General Pathology Pomeranian Medical University Szczecin Poland
| | | | | | - Krzysztof Safranow
- Department of Biochemistry and Medical Chemistry Pomeranian Medical University Szczecin Poland
| | - Miłosz Piotr Kawa
- Department of General Pathology Pomeranian Medical University Szczecin Poland
| | | | | | | | | | | | - Anna Machalińska
- First Department of Ophthalmology Pomeranian Medical University Szczecin Poland
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10
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Modulation of SOD3 Levels Is Detrimental to Retinal Homeostasis. Antioxidants (Basel) 2021; 10:antiox10101595. [PMID: 34679728 PMCID: PMC8533566 DOI: 10.3390/antiox10101595] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Revised: 10/05/2021] [Accepted: 10/07/2021] [Indexed: 01/08/2023] Open
Abstract
Retinal oxidative stress is a common secondary feature of many retinal diseases. Though it may not be the initial insult, it is a major contributor to the pathogenesis of highly prevalent retinal dystrophic diseases like macular degeneration, diabetic retinopathy, and retinitis pigmentosa. We explored the role of superoxide dismutase 3 (SOD3) in retinal homeostasis since SOD3 protects the extracellular matrix (ECM) from oxidative injury. We show that SOD3 is mainly extracellularly localized and is upregulated as a result of environmental and pathogenic stress. Ablation of SOD3 resulted in reduced functional electroretinographic responses and number of photoreceptors, which is exacerbated with age. By contrast, overexpression showed increased electroretinographic responses and increased number of photoreceptors at young ages, but appears deleterious as the animal ages, as determined from the associated functional decline. Our exploration shows that SOD3 is vital to retinal homeostasis but its levels are tightly regulated. This suggests that SOD3 augmentation to combat oxidative stress during retinal degenerative changes may only be effective in the short-term.
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11
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Adherent but Not Suspension-Cultured Embryoid Bodies Develop into Laminated Retinal Organoids. J Dev Biol 2021; 9:jdb9030038. [PMID: 34564087 PMCID: PMC8482155 DOI: 10.3390/jdb9030038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2021] [Revised: 08/31/2021] [Accepted: 09/08/2021] [Indexed: 11/23/2022] Open
Abstract
Human induced pluripotent stem cells (iPSCs) are differentiated into three-dimensional (3D) retinal organoids to study retinogenesis and diseases that would otherwise be impossible. The complexity and low yield in current protocols remain a technical challenge, particularly for inexperienced personnel. Differentiation protocols require labor-intensive and time-consuming dissection of optic vesicles (OVs). Here we compare this method with a suspension method of developing retinal organoids. iPSCs were differentiated with standard protocols but the suspension-grown method omitted the re-plating of embryoid bodies and dissection of OVs. All other media and treatments were identical between developmental methods. Developmental maturation was evaluated with RT-qPCR and immunocytochemistry. Dissection- and suspension-derived retinal organoids displayed temporal biogenesis of retinal cell types. Differences in retinal organoids generated by the two methods of differentiation included temporal developmental and the organization of neural retina layers. Retinal organoids grown in suspension showed delayed development and disorganized retinal layers compared to the dissected retinal organoids. We found that omitting the re-plating of EBs to form OVs resulted in numerous OVs that were easy to identify and matured along a retinal lineage. While more efficient, the suspension method led to retinal organoids with disorganized retinal layers compared to those obtained using conventional dissection protocols.
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12
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Peeters MHCA, Khan M, Rooijakkers AAMB, Mulders T, Haer-Wigman L, Boon CJF, Klaver CCW, van den Born LI, Hoyng CB, Cremers FPM, den Hollander AI, Dhaenens CM, Collin RWJ. PRPH2 mutation update: In silico assessment of 245 reported and 7 novel variants in patients with retinal disease. Hum Mutat 2021; 42:1521-1547. [PMID: 34411390 PMCID: PMC9290825 DOI: 10.1002/humu.24275] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Revised: 07/22/2021] [Accepted: 08/16/2021] [Indexed: 01/31/2023]
Abstract
Mutations in PRPH2, encoding peripherin-2, are associated with the development of a wide variety of inherited retinal diseases (IRDs). To determine the causality of the many PRPH2 variants that have been discovered over the last decades, we surveyed all published PRPH2 variants up to July 2020, describing 720 index patients that in total carried 245 unique variants. In addition, we identified seven novel PRPH2 variants in eight additional index patients. The pathogenicity of all variants was determined using the ACMG guidelines. With this, 107 variants were classified as pathogenic, 92 as likely pathogenic, one as benign, and two as likely benign. The remaining 50 variants were classified as variants of uncertain significance. Interestingly, of the total 252 PRPH2 variants, more than half (n = 137) were missense variants. All variants were uploaded into the Leiden Open source Variation and ClinVar databases. Our study underscores the need for experimental assays for variants of unknown significance to improve pathogenicity classification, which would allow us to better understand genotype-phenotype correlations, and in the long-term, hopefully also support the development of therapeutic strategies for patients with PRPH2-associated IRD.
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Affiliation(s)
- Manon H C A Peeters
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Human Genetics and Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | - Mubeen Khan
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Human Genetics and Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | | | - Timo Mulders
- Department of Human Genetics and Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.,Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Lonneke Haer-Wigman
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Camiel J F Boon
- Department of Ophthalmology, Leiden University Medical Center, Leiden, The Netherlands.,Department of Ophthalmology, Amsterdam UMC, Academic Medical Center, Amsterdam, The Netherlands
| | - Caroline C W Klaver
- Department of Human Genetics and Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.,Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Ophthalmology, Erasmus University Medical Centre, Rotterdam, The Netherlands.,Institute of Molecular and Clinical Ophthalmology, Basel, Switzerland
| | - L Ingeborgh van den Born
- The Rotterdam Eye Hospital, Rotterdam, The Netherlands.,Rotterdam Ophthalmic Institute, Rotterdam, The Netherlands
| | - Carel B Hoyng
- Department of Human Genetics and Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.,Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Human Genetics and Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
| | - Anneke I den Hollander
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Human Genetics and Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands.,Department of Ophthalmology, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Claire-Marie Dhaenens
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Biochemistry and Molecular Biology, Univ. Lille, Inserm, CHU Lille, U1172-LilNCog-Lille Neuroscience & Cognition, Lille, France
| | - Rob W J Collin
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands.,Department of Human Genetics and Ophthalmology, Donders Institute for Brain, Cognition and Behaviour, Nijmegen, The Netherlands
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13
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Lewis TR, Makia MS, Castillo CM, Al-Ubaidi MR, Naash MI, Arshavsky VY. Photoreceptor Disc Enclosure Is Tightly Controlled by Peripherin-2 Oligomerization. J Neurosci 2021; 41:3588-3596. [PMID: 33707293 PMCID: PMC8055076 DOI: 10.1523/jneurosci.0041-21.2021] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2021] [Revised: 02/15/2021] [Accepted: 03/05/2021] [Indexed: 11/21/2022] Open
Abstract
Mutations in the PRPH2 gene encoding the photoreceptor-specific protein PRPH2 (also known as peripherin-2 or rds) cause a broad range of autosomal dominant retinal diseases. Most of these mutations affect the structure of the light-sensitive photoreceptor outer segment, which is composed of a stack of flattened "disc" membranes surrounded by the plasma membrane. The outer segment is renewed on a daily basis in a process whereby new discs are added at the outer segment base and old discs are shed at the outer segment tip. New discs are formed as serial membrane evaginations, which eventually enclose through a complex process of membrane remodeling (completely in rods and partially in cones). As disc enclosure proceeds, PRPH2 localizes to the rims of enclosed discs where it forms oligomers which fortify the highly curved membrane structure of these rims. In this study, we analyzed the outer segment phenotypes of mice of both sexes bearing a single copy of either the C150S or the Y141C PRPH2 mutation known to prevent or increase the degree of PRPH2 oligomerization, respectively. Strikingly, both mutations increased the number of newly forming, not-yet-enclosed discs, indicating that the precision of disc enclosure is regulated by PRPH2 oligomerization. Without tightly controlled enclosure, discs occasionally over-elongate and form large membranous "whorls" instead of disc stacks. These data show that the defects in outer segment structure arising from abnormal PRPH2 oligomerization are manifested at the stage of disc enclosure.SIGNIFICANCE STATEMENT The light-sensitive photoreceptor outer segment contains a stack of flattened "disc" membranes that are surrounded, or "enclosed," by the outer segment membrane. Disc enclosure is an adaptation increasing photoreceptor light sensitivity by facilitating the diffusion of the second messenger along the outer segment axes. However, the molecular mechanisms by which photoreceptor discs enclose within the outer segment membrane remain poorly understood. We now demonstrate that oligomers of the photoreceptor-specific protein peripherin-2, or PRPH2, play an active role in this process. We further propose that defects in disc enclosure because of abnormal PRPH2 oligomerization result in major structural abnormalities of the outer segment, ultimately leading to loss of visual function and cell degeneration in PRPH2 mutant models and human patients.
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Affiliation(s)
- Tylor R Lewis
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina 27710
| | - Mustafa S Makia
- Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
| | - Carson M Castillo
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina 27710
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
- College of Optometry, University of Houston, Houston, Texas 77204
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
- College of Optometry, University of Houston, Houston, Texas 77204
| | - Vadim Y Arshavsky
- Department of Ophthalmology, Duke University Medical Center, Durham, North Carolina 27710
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina 27710
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14
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Strayve D, Makia MS, Kakakhel M, Sakthivel H, Conley SM, Al-Ubaidi MR, Naash MI. ROM1 contributes to phenotypic heterogeneity in PRPH2-associated retinal disease. Hum Mol Genet 2020; 29:2708-2722. [PMID: 32716032 DOI: 10.1093/hmg/ddaa160] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 07/03/2020] [Accepted: 07/16/2020] [Indexed: 11/14/2022] Open
Abstract
Peripherin 2 (PRPH2) is a retina-specific tetraspanin protein essential for the formation of rod and cone photoreceptor outer segments (OS). Patients with mutations in PRPH2 exhibit severe retinal degeneration characterized by vast inter- and intra-familial phenotypic heterogeneity. To help understand contributors to this within-mutation disease variability, we asked whether the PRPH2 binding partner rod OS membrane protein 1 (ROM1) could serve as a phenotypic modifier. We utilized knockin and transgenic mouse models to evaluate the structural, functional and biochemical effects of eliminating one allele of Rom1 (Rom1+/-) in three different Prph2 models which mimic human disease: C213Y Prph2 (Prph2C/+), K153Del Prph2 (Prph2K/+) and R172W (Prph2R172W). Reducing Rom1 in the absence of Prph2 mutations (Rom1+/-) had no effect on retinal structure or function. However, the effects of reducing Rom1 in the presence of Prph2 mutations were highly variable. Prph2K/+/Rom1+/- mice had improved rod and cone function compared with Prph2K/+ as well as amelioration of K153Del-associated defects in PRPH2/ROM1 oligomerization. In contrast, Prph2R172W/Rom1+/- animals had worsened rod and cone function and exacerbated retinal degeneration compared with Prph2R172W animals. Removing one allele of Rom1 had no effect in Prph2C/+. Combined, our findings support a role for non-pathogenic ROM1 null variants in contributing to phenotypic variability in mutant PRPH2-associated retinal degeneration. Since the effects of Rom1 reduction are variable, our data suggest that this contribution is specific to the type of Prph2 mutation.
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Affiliation(s)
- Daniel Strayve
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
| | - Mustafa S Makia
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
| | - Mashal Kakakhel
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
| | - Haarthi Sakthivel
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.,Oklahoma Center for Neurosciences, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA.,College of Optometry, University of Houston, Houston, TX 77004, USA.,Depatment of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX 77204, USA.,College of Optometry, University of Houston, Houston, TX 77004, USA.,Depatment of Biology and Biochemistry, University of Houston, Houston, TX 77204-5001, USA
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15
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Narasimhan I, Murali A, Subramanian K, Ramalingam S, Parameswaran S. Autosomal dominant retinitis pigmentosa with toxic gain of function: Mechanisms and therapeutics. Eur J Ophthalmol 2020; 31:304-320. [PMID: 32962414 DOI: 10.1177/1120672120957605] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Autosomal dominant retinitis pigmentosa is a form of retinitis pigmentosa, an inherited retinal degenerative disorder characterized by progressive loss of photoreceptors eventually leading to irreversible loss of vision. Mutations in genes involved in the basic functions of the visual system give rise to this condition. These mutations can either lead to loss of function or toxic gain of function phenotypes. While autosomal dominant retinitis pigmentosa caused by loss of function can be ideally treated by gene supplementation with a single vector to address a different spectrum of mutations in a gene, the same strategy cannot be applied to toxic gain of function phenotypes. In toxic gain of function phenotypes, the mutation in the gene results in the acquisition of a new function that can interrupt the functioning of the wildtype protein by various mechanisms leading to cell toxicity, thus making a single approach impractical. This review focuses on the genes and mechanisms that cause toxic gain of function phenotypes associated with autosomal dominant retinitis pigmentosa and provide a bird's eye view on current therapeutic strategies and ongoing clinical trials.
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Affiliation(s)
- Ishwarya Narasimhan
- Radheshyam Kanoi Stem Cell Laboratory, Kamalnayan Bajaj Institute for Research in Vision and Ophthalmology, Vision Research Foundation, Chennai, Tamil Nadu, India
| | - Aishwarya Murali
- Radheshyam Kanoi Stem Cell Laboratory, Kamalnayan Bajaj Institute for Research in Vision and Ophthalmology, Vision Research Foundation, Chennai, Tamil Nadu, India
| | - Krishnakumar Subramanian
- Radheshyam Kanoi Stem Cell Laboratory, Kamalnayan Bajaj Institute for Research in Vision and Ophthalmology, Vision Research Foundation, Chennai, Tamil Nadu, India
| | - Sivaprakash Ramalingam
- Genomics and Molecular Medicine Unit, Council of Scientific and Industrial Research - Institute of Genomics and Integrative Biology, New Delhi, India
| | - Sowmya Parameswaran
- Radheshyam Kanoi Stem Cell Laboratory, Kamalnayan Bajaj Institute for Research in Vision and Ophthalmology, Vision Research Foundation, Chennai, Tamil Nadu, India
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16
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Coco-Martin RM, Sanchez-Tocino HT, Desco C, Usategui-Martín R, Tellería JJ. PRPH2-Related Retinal Diseases: Broadening the Clinical Spectrum and Describing a New Mutation. Genes (Basel) 2020; 11:genes11070773. [PMID: 32660024 PMCID: PMC7397286 DOI: 10.3390/genes11070773] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2020] [Revised: 06/30/2020] [Accepted: 07/07/2020] [Indexed: 12/12/2022] Open
Abstract
Over 175 pathogenic mutations in the Peripherin-2 (PRPH2) gene are linked to various retinal diseases. We report the phenotype and genotype of eight families (24 patients) with retinal diseases associated with seven distinct PRPH2 gene mutations. We identified a new mutation, c.824_828+3delinsCATTTGGGCTCCTCATTTGG, in a patient with adult-onset vitelliform macular dystrophy (AVMD). One family with the p.Arg46Ter mutation presented with the already described AVMD phenotype, but another family presented with the same mutation and two heterozygous pathogenic mutations (p.Leu2027Phe and p.Gly1977Ser) in the ATP Binding Cassette Subfamily A Member 4 (ABCA4) gene that cause extensive chorioretinal atrophy (ECA), which could be a blended phenotype. The p.Lys154del PRPH2 gene mutation associated with the p.Arg2030Glu mutation in the ABCA4 gene was found in a patient with multifocal pattern dystrophy simulating fundus flavimaculatus (PDsFF), for whom we considered ABCA4 as a possible modifying gene. The mutation p.Gly167Ser was already known to cause pattern dystrophy, but we also found ECA, PDsFF, and autosomal-dominant retinitis pigmentosa (ADRP) as possible phenotypes. Finally, we identified the mutation p.Arg195Leu in a large family with common ancestry, which previously was described to cause central areolar choroidal dystrophy (CACD), but we also found ADRP and observed that it caused ECA more frequently than CACD in this family.
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Affiliation(s)
- Rosa M. Coco-Martin
- Instituto Universitario de Oftalmobiologia Aplicada, Universidad de Valladolid, 47011 Valladolid, Spain; (R.U.-M.); (J.J.T.)
- Red Temática de Investigación Cooperativa en Salud de Oftalmologia (Oftared), Instituto de Salud Carlos III, 28029 Madrid, Spain
- Correspondence: ; Tel.: +34-983-423-559 (ext. 4738)
| | | | - Carmen Desco
- Fisabio Oftalmologia Medica, 46035 Valencia, Spain;
| | - Ricardo Usategui-Martín
- Instituto Universitario de Oftalmobiologia Aplicada, Universidad de Valladolid, 47011 Valladolid, Spain; (R.U.-M.); (J.J.T.)
| | - Juan J. Tellería
- Instituto Universitario de Oftalmobiologia Aplicada, Universidad de Valladolid, 47011 Valladolid, Spain; (R.U.-M.); (J.J.T.)
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17
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Collin GB, Gogna N, Chang B, Damkham N, Pinkney J, Hyde LF, Stone L, Naggert JK, Nishina PM, Krebs MP. Mouse Models of Inherited Retinal Degeneration with Photoreceptor Cell Loss. Cells 2020; 9:cells9040931. [PMID: 32290105 PMCID: PMC7227028 DOI: 10.3390/cells9040931] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2020] [Revised: 04/05/2020] [Accepted: 04/07/2020] [Indexed: 12/12/2022] Open
Abstract
Inherited retinal degeneration (RD) leads to the impairment or loss of vision in millions of individuals worldwide, most frequently due to the loss of photoreceptor (PR) cells. Animal models, particularly the laboratory mouse, have been used to understand the pathogenic mechanisms that underlie PR cell loss and to explore therapies that may prevent, delay, or reverse RD. Here, we reviewed entries in the Mouse Genome Informatics and PubMed databases to compile a comprehensive list of monogenic mouse models in which PR cell loss is demonstrated. The progression of PR cell loss with postnatal age was documented in mutant alleles of genes grouped by biological function. As anticipated, a wide range in the onset and rate of cell loss was observed among the reported models. The analysis underscored relationships between RD genes and ciliary function, transcription-coupled DNA damage repair, and cellular chloride homeostasis. Comparing the mouse gene list to human RD genes identified in the RetNet database revealed that mouse models are available for 40% of the known human diseases, suggesting opportunities for future research. This work may provide insight into the molecular players and pathways through which PR degenerative disease occurs and may be useful for planning translational studies.
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Affiliation(s)
- Gayle B. Collin
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Navdeep Gogna
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Bo Chang
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Nattaya Damkham
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
- Department of Immunology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
- Siriraj Center of Excellence for Stem Cell Research, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok 10700, Thailand
| | - Jai Pinkney
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Lillian F. Hyde
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Lisa Stone
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Jürgen K. Naggert
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
| | - Patsy M. Nishina
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
- Correspondence: (P.M.N.); (M.P.K.); Tel.: +1-207-2886-383 (P.M.N.); +1-207-2886-000 (M.P.K.)
| | - Mark P. Krebs
- The Jackson Laboratory, Bar Harbor, Maine, ME 04609, USA; (G.B.C.); (N.G.); (B.C.); (N.D.); (J.P.); (L.F.H.); (L.S.); (J.K.N.)
- Correspondence: (P.M.N.); (M.P.K.); Tel.: +1-207-2886-383 (P.M.N.); +1-207-2886-000 (M.P.K.)
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18
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The Interplay between Peripherin 2 Complex Formation and Degenerative Retinal Diseases. Cells 2020; 9:cells9030784. [PMID: 32213850 PMCID: PMC7140794 DOI: 10.3390/cells9030784] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2020] [Revised: 03/11/2020] [Accepted: 03/20/2020] [Indexed: 12/17/2022] Open
Abstract
Peripherin 2 (Prph2) is a photoreceptor-specific tetraspanin protein present in the outer segment (OS) rims of rod and cone photoreceptors. It shares many common features with other tetraspanins, including a large intradiscal loop which contains several cysteines. This loop enables Prph2 to associate with itself to form homo-oligomers or with its homologue, rod outer segment membrane protein 1 (Rom1) to form hetero-tetramers and hetero-octamers. Mutations in PRPH2 cause a multitude of retinal diseases including autosomal dominant retinitis pigmentosa (RP) or cone dominant macular dystrophies. The importance of Prph2 for photoreceptor development, maintenance and function is underscored by the fact that its absence results in a failure to initialize OS formation in rods and formation of severely disorganized OS membranous structures in cones. Although the exact role of Rom1 has not been well studied, it has been concluded that it is not necessary for disc morphogenesis but is required for fine tuning OS disc size and structure. Pathogenic mutations in PRPH2 often result in complex and multifactorial phenotypes, involving not just photoreceptors, as has historically been reasoned, but also secondary effects on the retinal pigment epithelium (RPE) and retinal/choroidal vasculature. The ability of Prph2 to form complexes was identified as a key requirement for the development and maintenance of OS structure and function. Studies using mouse models of pathogenic Prph2 mutations established a connection between changes in complex formation and disease phenotypes. Although progress has been made in the development of therapeutic approaches for retinal diseases in general, the highly complex interplay of functions mediated by Prph2 and the precise regulation of these complexes made it difficult, thus far, to develop a suitable Prph2-specific therapy. Here we describe the latest results obtained in Prph2-associated research and how mouse models provided new insights into the pathogenesis of its related diseases. Furthermore, we give an overview on the current status of the development of therapeutic solutions.
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19
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Chakraborty D, Strayve DG, Makia MS, Conley SM, Kakahel M, Al-Ubaidi MR, Naash MI. Novel molecular mechanisms for Prph2-associated pattern dystrophy. FASEB J 2019; 34:1211-1230. [PMID: 31914632 DOI: 10.1096/fj.201901888r] [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: 08/01/2019] [Revised: 10/10/2019] [Accepted: 11/14/2019] [Indexed: 01/16/2023]
Abstract
Mutations in peripherin 2 (PRPH2) have been associated with retinitis pigmentosa (RP) and macular/pattern dystrophies, but the origin of this phenotypic variability is unclear. The majority of Prph2 mutations are located in the large intradiscal loop (D2), a region that contains seven cysteines involved in intra- and intermolecular disulfide bonding and protein folding. A mutation at cysteine 213, which is engaged in an intramolecular disulfide bond, leads to butterfly-shaped pattern dystrophy in humans, in sharp contrast to mutations in the adjacent cysteine at position 214 which result in RP. To help understand this unexpected phenotypic variability, we generated a knockin mouse line carrying the C213Y disease mutation. The mutant Prph2 protein lost the ability to oligomerize with rod outer segment membrane protein 1 (Rom1), but retained the ability to form homotetramers. C213Y heterozygotes had significantly decreased overall Prph2 levels as well as decreased rod and cone function. Critically, supplementation with extra wild-type Prph2 protein elicited improvements in Prph2 protein levels and rod outer segment structure, but not functional rescue in rods or cones. These findings suggest that not all interruptions of D2 loop intramolecular disulfide bonding lead to haploinsufficiency-related RP, but rather that more subtle changes can lead to mutant proteins stable enough to exert gain-of-function defects in rods and cones. This outcome highlights the difficulty in targeting Prph2-associated gain-of-function disease and suggests that elimination of the mutant protein will be a pre-requisite for any curative therapeutic strategy.
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Affiliation(s)
- Dibyendu Chakraborty
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA.,Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Daniel G Strayve
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
| | - Mustafa S Makia
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Mashal Kakahel
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
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20
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Zulliger R, Conley SM, Mwoyosvi ML, Al-Ubaidi MR, Naash MI. Oligomerization of Prph2 and Rom1 is essential for photoreceptor outer segment formation. Hum Mol Genet 2019; 27:3507-3518. [PMID: 29961824 DOI: 10.1093/hmg/ddy240] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2018] [Accepted: 06/04/2018] [Indexed: 12/20/2022] Open
Abstract
Mutations in peripherin 2 (PRPH2, also known as Rds), a tetraspanin protein found in photoreceptor outer segments (OSs), cause retinal degeneration ranging from rod-dominant retinitis pigmentosa (RP) to cone-dominant macular dystrophy (MD). Understanding why some Prph2 mutants affect rods while others affect cones remains a critical unanswered question. Prph2 is essential for OS structure and function and exhibits a very specific pattern of oligomerization with its homolog Rom1. Non-covalent Prph2/Rom1 homo- and hetero-tetramers assemble into higher-order covalently linked complexes held together by an intermolecular disulfide bond at Prph2-C150/Rom1-C153. Here we disrupt this crucial bond using a C150S-Prph2 knockin mouse line to study the role of Prph2 higher-order complex formation. We find that C150S-Prph2 traffics to the OS, interacts with Rom1 and forms non-covalent tetramers, but alone cannot support normal OS structure and function. However, C150S-Prph2 supports the initiation or elaboration of OS disc structures, and improves rod OS ultrastructure in the presence of wild-type (WT) Prph2 (i.e. Prph2C150S/+ versus Prph2+/-). Prph2C150S/+ animals exhibit haploinsufficiency in rods, but a dominant-negative phenotype in cones, suggesting cones have a different requirement for large Prph2 complexes than rods. Importantly, cone but not rod function can be improved by the addition of one Prph2Y141C allele, a mutation responsible for pattern dystrophy owing to the extra cysteine. Combined these findings show that covalently linked Prph2 complexes are essential for OS formation, but not for Prph2 targeting to the OS, and that cones are especially sensitive to having a broad distribution of Prph2 complex types (i.e. tetramers and large complexes).
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Affiliation(s)
- Rahel Zulliger
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
| | - Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Maggie L Mwoyosvi
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
| | - Muayyad R Al-Ubaidi
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
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21
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Conley SM, Stuck MW, Watson JN, Zulliger R, Burnett JL, Naash MI. Prph2 initiates outer segment morphogenesis but maturation requires Prph2/Rom1 oligomerization. Hum Mol Genet 2019; 28:459-475. [PMID: 30307502 PMCID: PMC6337695 DOI: 10.1093/hmg/ddy359] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2018] [Accepted: 10/05/2018] [Indexed: 12/15/2022] Open
Abstract
The retinal disease gene peripherin 2 (PRPH2) is essential for the formation of photoreceptor outer segments (OSs), where it functions in oligomers with and without its homologue ROM1. However, the precise role of these proteins in OS morphogenesis is not understood. By utilizing a knock-in mouse expressing a chimeric protein comprised of the body of Rom1 and the C-terminus of Prph2 (termed RRCT), we find that the Prph2 C-terminus is necessary and sufficient for the initiation of OSs, while OS maturation requires the body of Prph2 and associated large oligomers. Importantly, dominant-negative physiological and biochemical defects in RRCT heterozygous rods are rescued by removing Rom1, suggesting Rom1 is a regulator for OS formation. Our experiments evaluating Prph2 trafficking show that Rom1 is a key determinant of whether Prph2 complexes utilize conventional versus unconventional (Golgi bypass) secretory pathways to reach the OS. These findings significantly advance our understanding of the molecular underpinnings of OS morphogenesis and particularly the role of Rom1.
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Affiliation(s)
- Shannon M Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Michael W Stuck
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Jamie N Watson
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Rahel Zulliger
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
| | - Justin L Burnett
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Muna I Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA,To whom correspondence should be addressed at: Department of Biomedical Engineering University of Houston, 3517 Cullen Blvd., Room 2011, Houston, TX 77204-5060, USA. Tel: +713 7431651; E-mail:
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22
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Cehofski LJ, Kruse A, Kirkeby S, Alsing AN, Ellegaard Nielsen J, Kojima K, Honoré B, Vorum H. IL-18 and S100A12 Are Upregulated in Experimental Central Retinal Vein Occlusion. Int J Mol Sci 2018; 19:ijms19113328. [PMID: 30366444 PMCID: PMC6274751 DOI: 10.3390/ijms19113328] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2018] [Revised: 10/08/2018] [Accepted: 10/10/2018] [Indexed: 12/22/2022] Open
Abstract
Retinal vein occlusion (RVO) is a common retinal vascular disease. RVO may be complicated by pronounced ischemia that often leads to severe loss of visual function. The present work aimed at studying the retinal proteome of RVO complicated by ischemia. In six Danish Landrace pigs RVO was induced with argon laser in the right eye of each animal. As four retinal veins were occluded, the RVO best corresponded to a central retinal vein occlusion (CRVO). Left control eyes received a similar laser treatment without inducing occlusion. RVO and retinal ischemia were verified by angiography. The retinas were collected 15 days after RVO for proteomic analysis. RVO resulted in a downregulation of proteins involved in visual perception, including rhodopsin, transducin alpha chain, and peripherin-2. RVO also caused a downregulation of proteins involved in neurotransmitter transport, including glutamate decarboxylase 1 (GAD1), glutamate decarboxylase 2 (GAD2), and complexins 2⁻4. RVO lead to increased contents of proteins involved in inflammation, including interleukin-18 (IL-18), S100A12, and annexin A1 (ANXA1). Immunohistochemistry revealed a general retinal upregulation of IL-18 and ANXA1 while S100A12 was highly abundant in retinal ganglion cells in RVO. IL-18 and S100A12 are likely to be driving forces in the inflammatory response of RVO complicated by ischemia. Our findings also suggest that RVO results in compromised neurotransmission and a downregulation of proteins involved in visual perception.
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Affiliation(s)
- Lasse Jørgensen Cehofski
- Department of Ophthalmology, Aalborg University Hospital, Hobrovej 18-22, 9000 Aalborg, Denmark.
- Biomedical Research Laboratory, Aalborg University Hospital, 9000 Aalborg, Denmark.
- Department of Clinical Medicine, Aalborg University, 9000 Aalborg, Denmark.
| | - Anders Kruse
- Department of Ophthalmology, Aalborg University Hospital, Hobrovej 18-22, 9000 Aalborg, Denmark.
| | - Svend Kirkeby
- Department of Odontology, School of Dentistry, University of Copenhagen, 1017 Copenhagen, Denmark.
| | - Alexander Nørgård Alsing
- Department of Ophthalmology, Aalborg University Hospital, Hobrovej 18-22, 9000 Aalborg, Denmark.
| | | | - Kentaro Kojima
- Department of Ophthalmology, Kyoto Prefectural University of Medicine, 6028566 Kyoto, Japan.
| | - Bent Honoré
- Department of Clinical Medicine, Aalborg University, 9000 Aalborg, Denmark.
- Department of Biomedicine, Aarhus University, 8000 Aarhus, Denmark.
| | - Henrik Vorum
- Department of Ophthalmology, Aalborg University Hospital, Hobrovej 18-22, 9000 Aalborg, Denmark.
- Department of Clinical Medicine, Aalborg University, 9000 Aalborg, Denmark.
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23
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Kelley RA, Al-Ubaidi MR, Sinha T, Genc AM, Makia MS, Ikelle L, Naash MI. Ablation of the riboflavin-binding protein retbindin reduces flavin levels and leads to progressive and dose-dependent degeneration of rods and cones. J Biol Chem 2017; 292:21023-21034. [PMID: 29079576 DOI: 10.1074/jbc.m117.785105] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 10/26/2017] [Indexed: 11/06/2022] Open
Abstract
The interface between the neural retina and the retinal pigment epithelium (RPE) is critical for several processes, including visual pigment regeneration and retinal attachment to the RPE. One of its most important functions is the exchange of metabolites between the photoreceptors and RPE because photoreceptor cells have very high energy demands, largely satisfied by oxidative metabolism. The riboflavin (RF) cofactors, flavin adenine dinucleotide (FAD) and flavin mononucleotide (FMN), are two key cofactors involved in oxidative metabolism. We have previously shown that retbindin is a photoreceptor-specific RF-binding protein exclusively expressed in the rods and present in the interphotoreceptor matrix at the interface between the RPE and photoreceptor outer segments. Here, we show that retbindin ablation in mice causes a retinal phenotype characterized by time- and dose-dependent declines in rod and cone photoreceptor functions as early as 120 days of age. Whereas minor retinal ultrastructural defects were observed at all ages examined, a significant decline occurred in photoreceptor nuclei at 240 days of age (∼36.8% rods and ∼19.9% cones). Interestingly, significant reductions in FAD and FMN levels were observed before the onset of degeneration (∼46.1% FAD and ∼45% FMN). These findings suggest that the reduced levels of these flavins result in the disruption of intracellular mechanisms, leading to photoreceptor cell death. Altogether, our results suggest that retbindin is a key player in the acquisition and retention of flavins in the neural retina, warranting future investigation into retbindin's role in photoreceptor cell death in models of retinal degenerative disorders.
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Affiliation(s)
- Ryan A Kelley
- From the Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
| | - Muayyad R Al-Ubaidi
- From the Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
| | - Tirthankar Sinha
- From the Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
| | - Ayse M Genc
- From the Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
| | - Mustafa S Makia
- From the Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
| | - Larissa Ikelle
- From the Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
| | - Muna I Naash
- From the Department of Biomedical Engineering, University of Houston, Houston, Texas 77204
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24
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Conley SM, Stuck MW, Watson JN, Naash MI. Rom1 converts Y141C-Prph2-associated pattern dystrophy to retinitis pigmentosa. Hum Mol Genet 2017; 26:509-518. [PMID: 28053051 PMCID: PMC6075606 DOI: 10.1093/hmg/ddw408] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2016] [Revised: 11/02/2016] [Accepted: 11/21/2016] [Indexed: 12/15/2022] Open
Abstract
Mutations in peripherin 2 (PRPH2), also known as retinal degeneration slow/RDS, lead to various retinal degenerations including retinitis pigmentosa (RP) and macular/pattern dystrophy (MD/PD). PRPH2-associated disease is often characterized by a phenotypic variability even within families carrying the same mutation, raising interest in potential modifiers. PRPH2 oligomerizes with its homologue rod outer segment (OS) membrane protein 1 (ROM1), and non-pathogenic PRPH2/ROM1 mutations, when present together, lead to digenic RP. We asked whether ROM1 could modify the phenotype of a PRPH2 mutation associated with a high degree of intrafamilial phenotypic heterogeneity: Y141C. In vitro, Y141C-Prph2 showed signs of retention in the endoplasmic reticulum (ER), however co-expression with Rom1 rescued this phenotype. In the heterozygous Y141C knockin mouse model (Prph2Y/+), Y141C-Prph2 and Rom1 formed abnormal complexes but were present at normal levels. Abnormal complexes were eliminated in the absence of Rom1 (Prph2Y/+/Rom1-/-) and total Prph2 levels were reduced to those found in the haploinsufficient Prph2+/- RP model. The biochemical changes had functional and structural consequences; while Prph2Y/+ animals exhibited a cone-rod electroretinogram defect, Prph2Y/+/Rom1-/- animals displayed a rod-dominant phenotype and OSs similar to those seen in the Prph2+/-. These data show that ablation of Rom1 results in the conversion of an MD/PD phenotype characterized by cone functional defects and the formation of abnormal Prph2/Rom1 complexes to an RP phenotype characterized by rod-dominant functional defects and reductions in total Prph2 protein. Thus one method by which ROM1 may act as a disease modifier is by contributing to the large variability in PRPH2-associated disease phenotypes.
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Affiliation(s)
- Shannon M. Conley
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Michael W. Stuck
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Jamie N. Watson
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Muna I. Naash
- Department of Biomedical Engineering, University of Houston, Houston, TX, USA
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