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Ashok S, Ramachandra Rao S. Updates on protein-prenylation and associated inherited retinopathies. FRONTIERS IN OPHTHALMOLOGY 2024; 4:1410874. [PMID: 39026984 PMCID: PMC11254824 DOI: 10.3389/fopht.2024.1410874] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/01/2024] [Accepted: 06/13/2024] [Indexed: 07/20/2024]
Abstract
Membrane-anchored proteins play critical roles in cell signaling, cellular architecture, and membrane biology. Hydrophilic proteins are post-translationally modified by a diverse range of lipid molecules such as phospholipids, glycosylphosphatidylinositol, and isoprenes, which allows their partition and anchorage to the cell membrane. In this review article, we discuss the biochemical basis of isoprenoid synthesis, the mechanisms of isoprene conjugation to proteins, and the functions of prenylated proteins in the neural retina. Recent discovery of novel prenyltransferases, prenylated protein chaperones, non-canonical prenylation-target motifs, and reversible prenylation is expected to increase the number of inherited systemic and blinding diseases with aberrant protein prenylation. Recent important investigations have also demonstrated the role of several unexpected regulators (such as protein charge, sequence/protein-chaperone interaction, light exposure history) in the photoreceptor trafficking of prenylated proteins. Technical advances in the investigation of the prenylated proteome and its application in vision research are discussed. Clinical updates and technical insights into known and putative prenylation-associated retinopathies are provided herein. Characterization of non-canonical prenylation mechanisms in the retina and retina-specific prenylated proteome is fundamental to the understanding of the pathogenesis of protein prenylation-associated inherited blinding disorders.
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Affiliation(s)
- Sudhat Ashok
- Department of Ophthalmology, Jacobs School of Medicine and Biomedical Sciences, State University of New York, University at Buffalo, Buffalo, NY, United States
| | - Sriganesh Ramachandra Rao
- Department of Ophthalmology, Jacobs School of Medicine and Biomedical Sciences, State University of New York, University at Buffalo, Buffalo, NY, United States
- Neuroscience Program, Jacobs School of Medicine and Biomedical Sciences, State University of New York, University at Buffalo, Buffalo, NY, United States
- Research Service, VA Western New York Healthcare System, Buffalo, NY, United States
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2
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Kolkova Z, Durdik P, Holubekova V, Durdikova A, Jesenak M, Banovcin P. Identification of a novel RPGR mutation associated with retinitis pigmentosa and primary ciliary dyskinesia in a Slovak family: a case report. Front Pediatr 2024; 12:1339664. [PMID: 38333087 PMCID: PMC10850321 DOI: 10.3389/fped.2024.1339664] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2023] [Accepted: 01/10/2024] [Indexed: 02/10/2024] Open
Abstract
Background The mutations in the RPGR (retinitis pigmentosa GTPase regulator) gene are the most common cause of X-linked retinitis pigmentosa (XLRP), a rare genetic disorder affecting the photoreceptor cells in the retina. Several reported cases identified this gene as a genetic link between retinitis pigmentosa (RP) and primary ciliary dyskinesia (PCD), characterised by impaired ciliary function predominantly in the respiratory tract. Since different mutations in the same gene can result in various clinical manifestations, it is important to describe a correlation between the gene variant and the observed phenotype. Methods Two young brothers from a non-consanguineous Slovak family with diagnosed retinal dystrophy and recurrent respiratory infections were examined. Suspected PCD was diagnosed based on a PICADAR questionnaire, nasal nitric oxide analysis, transmission electron microscopy, high-speed video microscopy analysis, and genetic testing. Results We identified a novel frameshift RPGR mutation NM_001034853: c.309_310insA, p.Glu104Argfs*12, resulting in a complex X-linked phenotype combining PCD and RP. In our patients, this mutation was associated with normal ultrastructure of respiratory cilia, reduced ciliary epithelium, more aciliary respiratory epithelium, shorter cilia, and uncoordinated beating with a frequency at a lower limit of normal beating, explaining the clinical manifestation of PCD in our patients. Conclusion The identified novel pathogenic mutation in the RPGR gene expands the spectrum of genetic variants associated with the X-linked PCD phenotype overlapping with RP, highlighting the diversity of mutations contributing to the disorder. The described genotype-phenotype correlation can be useful in clinical practice to recognise a broader spectrum of PCD phenotypes as well as for future research focused on the genetic basis of PCD, gene interactions, the pathways implicated in PCD pathogenesis, and the role of RPGR protein for the proper functioning of cilia in various tissues throughout the body.
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Affiliation(s)
- Zuzana Kolkova
- Biomedical Center Martin, Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, Martin, Slovakia
| | - Peter Durdik
- Department of Pediatrics, Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, Martin, Slovakia
- Department of Pediatrics, University Hospital Martin, Martin, Slovakia
| | - Veronika Holubekova
- Biomedical Center Martin, Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, Martin, Slovakia
| | - Anna Durdikova
- Department of Pediatrics, Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, Martin, Slovakia
- Department of Pediatrics, University Hospital Martin, Martin, Slovakia
| | - Milos Jesenak
- Department of Pediatrics, Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, Martin, Slovakia
- Department of Pediatrics, University Hospital Martin, Martin, Slovakia
- Department of Pulmonology and Phthisiology, Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, University Hospital in Martin, Martin, Slovakia
- Department of Clinical Immunology and Allergology, University Hospital in Martin, Martin, Slovakia
| | - Peter Banovcin
- Department of Pediatrics, Jessenius Faculty of Medicine in Martin, Comenius University in Bratislava, Martin, Slovakia
- Department of Pediatrics, University Hospital Martin, Martin, Slovakia
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3
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Awadh Hashem S, Georgiou M, Ali RR, Michaelides M. RPGR-Related Retinopathy: Clinical Features, Molecular Genetics, and Gene Replacement Therapy. Cold Spring Harb Perspect Med 2023; 13:a041280. [PMID: 37188525 PMCID: PMC10626266 DOI: 10.1101/cshperspect.a041280] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Retinitis pigmentosa GTPase regulator (RPGR) gene variants are the predominant cause of X-linked retinitis pigmentosa (XLRP) and a common cause of cone-rod dystrophy (CORD). XLRP presents as early as the first decade of life, with impaired night vision and constriction of peripheral visual field and rapid progression, eventually leading to blindness. In this review, we present RPGR gene structure and function, molecular genetics, animal models, RPGR-associated phenotypes and highlight emerging potential treatments such as gene-replacement therapy.
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Affiliation(s)
- Shaima Awadh Hashem
- UCL Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, United Kingdom
| | - Michalis Georgiou
- UCL Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, United Kingdom
- Jones Eye Institute, University of Arkansas for Medical Sciences, Little Rock, Arkansas 72205, USA
| | - Robin R Ali
- UCL Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, United Kingdom
- Centre for Cell and Gene Therapy, King's College London, London WC2R 2LS, United Kingdom
| | - Michel Michaelides
- UCL Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom
- Moorfields Eye Hospital NHS Foundation Trust, London EC1V 2PD, United Kingdom
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4
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Wongchaisuwat N, Amato A, Lamborn AE, Yang P, Everett L, Pennesi ME. Retinitis pigmentosa GTPase regulator-related retinopathy and gene therapy. Saudi J Ophthalmol 2023; 37:276-286. [PMID: 38155670 PMCID: PMC10752277 DOI: 10.4103/sjopt.sjopt_168_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/14/2023] [Accepted: 08/16/2023] [Indexed: 12/30/2023] Open
Abstract
Retinitis pigmentosa GTPase regulator (RPGR)-related retinopathy is a retinal dystrophy inherited in a X-linked recessive manner that typically causes progressive visual loss starting in childhood with severe visual impairment by the fourth decade of life. It manifests as an early onset and severe form of retinitis pigmentosa. There are currently no effective treatments for RPGR-related retinopathy; however, there are multiple clinical trials in progress exploring gene augmentation therapy aimed at slowing down or halting the progression of disease and possibly restoring visual function. This review focuses on the molecular biology, clinical manifestations, and the recent progress of gene therapy clinical trials.
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Affiliation(s)
- Nida Wongchaisuwat
- Department of Ophthalmology, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand
- Department of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, USA
| | - Alessia Amato
- Department of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, USA
| | - Andrew E. Lamborn
- Department of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, USA
| | - Paul Yang
- Department of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, USA
| | - Lesley Everett
- Department of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, USA
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, Oregon, USA
| | - Mark E. Pennesi
- Department of Ophthalmology, Casey Eye Institute, Oregon Health and Science University, Portland, Oregon, USA
- Department of Molecular and Medical Genetics, Oregon Health and Science University, Portland, Oregon, USA
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Becherucci V, Bacci GM, Marziali E, Sodi A, Bambi F, Caputo R. The New Era of Therapeutic Strategies for the Treatment of Retinitis Pigmentosa: A Narrative Review of Pathomolecular Mechanisms for the Development of Cell-Based Therapies. Biomedicines 2023; 11:2656. [PMID: 37893030 PMCID: PMC10604477 DOI: 10.3390/biomedicines11102656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Revised: 09/20/2023] [Accepted: 09/25/2023] [Indexed: 10/29/2023] Open
Abstract
Retinitis pigmentosa, defined more properly as cone-rod dystrophy, is a paradigm of inherited diffuse retinal dystrophies, one of the rare diseases with the highest prevalence in the worldwide population and one of the main causes of low vision in the pediatric and elderly age groups. Advancements in and the understanding of molecular biology and gene-editing technologies have raised interest in laying the foundation for new therapeutic strategies for rare diseases. As a consequence, new possibilities for clinicians and patients are arising due to the feasibility of treating such a devastating disorder, reducing its complications. The scope of this review focuses on the pathomolecular mechanisms underlying RP better to understand the prospects of its treatment using innovative approaches.
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Affiliation(s)
- Valentina Becherucci
- Cell Factory Meyer, Children’s Hospital A. Meyer Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS), University of Florence, 50139 Florence, Italy; (V.B.); (F.B.)
| | - Giacomo Maria Bacci
- Pediatric Ophthalmology Unit, Children’s Hospital A. Meyer Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS), University of Florence, 50139 Florence, Italy; (E.M.); (R.C.)
| | - Elisa Marziali
- Pediatric Ophthalmology Unit, Children’s Hospital A. Meyer Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS), University of Florence, 50139 Florence, Italy; (E.M.); (R.C.)
| | - Andrea Sodi
- Department of Neuroscience, Psychology, Drug Research and Child Health, University of Florence, 50139 Florence, Italy;
| | - Franco Bambi
- Cell Factory Meyer, Children’s Hospital A. Meyer Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS), University of Florence, 50139 Florence, Italy; (V.B.); (F.B.)
| | - Roberto Caputo
- Pediatric Ophthalmology Unit, Children’s Hospital A. Meyer Istituti di Ricovero e Cura a Carattere Scientifico (IRCCS), University of Florence, 50139 Florence, Italy; (E.M.); (R.C.)
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6
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Hadalin V, Buscarino M, Sajovic J, Meglič A, Jarc-Vidmar M, Hawlina M, Volk M, Fakin A. Genetic Characteristics and Long-Term Follow-Up of Slovenian Patients with RPGR Retinal Dystrophy. Int J Mol Sci 2023; 24:ijms24043840. [PMID: 36835250 PMCID: PMC9958649 DOI: 10.3390/ijms24043840] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Revised: 02/01/2023] [Accepted: 02/06/2023] [Indexed: 02/17/2023] Open
Abstract
Genetic characteristics and a long-term clinical follow-up of 18 Slovenian retinitis pigmentosa GTPase regulator (RPGR) patients from 10 families with retinitis pigmentosa (RP) or cone/cone-rod dystrophy (COD/CORD) are reported. RP (eight families) was associated with two already known (p.(Ser407Ilefs*46) and p.(Glu746Argfs*23)) and five novel variants (c.1245+704_1415-2286del, p.(Glu660*), p.(Ala153Thr), c.1506+1G>T, and p.(Arg780Serfs*54)). COD (two families) was associated with p.(Ter1153Lysext*38). The median age of onset in males with RP (N = 9) was 6 years. At the first examination (median age of 32 years), the median best corrected visual acuity (BCVA) was 0.30 logMAR, and all patients had a hyperautofluorescent ring on fundus autofluorescence (FAF) encircling preserved photoreceptors. At the last follow-up (median age of 39 years), the median BCVA was 0.48 logMAR, and FAF showed ring constriction transitioning to patch in 2/9. Among females (N = 6; median age of 40 years), two had normal/near-normal FAF, one had unilateral RP (male pattern), and three had a radial and/or focal pattern of retinal degeneration. After a median of 4 years (4-21) of follow-up, 2/6 exhibited disease progression. The median age of onset in males with COD was 25 years. At first examination (median age of 35 years), the median BCVA was 1.00 logMAR, and all patients had a hyperautofluorescent FAF ring encircling foveal photoreceptor loss. At the last follow-up (median age of 42 years), the median BCVA was 1.30 logMAR, and FAF showed ring enlargement. The majority of the identified variants (75%; 6/8) had not been previously reported in other RPGR cohorts, which suggested the presence of distinct RPGR alleles in the Slovenian population.
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Affiliation(s)
- Vlasta Hadalin
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Maša Buscarino
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Jana Sajovic
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Andrej Meglič
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Martina Jarc-Vidmar
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Marko Hawlina
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Marija Volk
- Clinical Institute of Genomic Medicine, University Medical Centre Ljubljana, Šlajmerjeva 4, 1000 Ljubljana, Slovenia
| | - Ana Fakin
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
- Correspondence:
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7
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Roshandel D, Lamey TM, Charng J, Heath Jeffery RC, McLaren TL, Thompson JA, De Roach JN, McLenachan S, Mackey DA, Chen FK. Microperimetry and Adaptive Optics Imaging Reveal Localized Functional and Structural Changes in Asymptomatic RPGR Mutation Carriers. Invest Ophthalmol Vis Sci 2023; 64:3. [PMID: 36607619 PMCID: PMC9836009 DOI: 10.1167/iovs.64.1.3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Purpose Female carriers of RPGR mutations demonstrate no significant retinal dysfunction or structural change despite a characteristic tapetal-like reflex. In this study, we examined localized changes of pointwise sensitivity (PWS) and cone density (CD) using microperimetry (MP) and adaptive optics (AO) imaging in female carriers of RPGR mutations. Methods In this cross-sectional case-control study, MP (MAIA, 10-2 test grid) and AO imaging (rtx1) were performed in female carriers of RPGR mutations and unrelated age-matched healthy controls. PWS at 68 loci located 1 degree to 9 degrees away from the preferred retinal locus and CD at 12 loci located 1 degree to 3 degrees away from the foveal center were measured. Severity of defect was defined by standard deviation (SD) from age-matched healthy control means: normal (<1 SD from normal average), moderate defect (1-2 SD from normal average), and severe defect (>2 SD from normal average). Results Twelve patients from seven unrelated families were enrolled. Seven patients were asymptomatic, 5 of whom had visual acuity 20/20 or better in both eyes. PWS and CD were available in 12 and 8 patients, respectively. Severe PWS and CD defect in at least 1 test location was observed in 10 of 12 patients and 7 of 8 patients, respectively. Among the five asymptomatic patients who had normal visual acuity, severe PWS and CD defects were observed in three of five and four of five patients, respectively. Conclusions MP and AO imaging revealed early functional and structural changes in asymptomatic RPGR mutation carriers and should be considered in clinical assessment of these patients.
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Affiliation(s)
- Danial Roshandel
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Western Australia, Australia,Ocular Tissue Engineering Laboratory, Lions Eye Institute, Nedlands, Western Australia, Australia
| | - Tina M. Lamey
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Western Australia, Australia,Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia
| | - Jason Charng
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Western Australia, Australia,Department of Optometry, School of Allied Health, University of Western Australia, Western Australia, Australia
| | - Rachael C. Heath Jeffery
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Western Australia, Australia,Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia
| | - Terri L. McLaren
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Western Australia, Australia,Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia
| | - Jennifer A. Thompson
- Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia
| | - John N. De Roach
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Western Australia, Australia,Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia
| | - Samuel McLenachan
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Western Australia, Australia,Ocular Tissue Engineering Laboratory, Lions Eye Institute, Nedlands, Western Australia, Australia
| | - David A. Mackey
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Western Australia, Australia,Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia
| | - Fred K. Chen
- Centre for Ophthalmology and Visual Science, The University of Western Australia, Nedlands, Western Australia, Australia,Ocular Tissue Engineering Laboratory, Lions Eye Institute, Nedlands, Western Australia, Australia,Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and Physics, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia,Department of Optometry, School of Allied Health, University of Western Australia, Western Australia, Australia,Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, Melbourne, Victoria, Australia,Ophthalmology, Department of Surgery, University of Melbourne, Melbourne, Victoria, Australia
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8
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Chahine Karam F, Loi TH, Ma A, Nash BM, Grigg JR, Parekh D, Riley LG, Farnsworth E, Bennetts B, Gonzalez-Cordero A, Jamieson RV. Human iPSC-Derived Retinal Organoids and Retinal Pigment Epithelium for Novel Intronic RPGR Variant Assessment for Therapy Suitability. J Pers Med 2022; 12:jpm12030502. [PMID: 35330501 PMCID: PMC8951517 DOI: 10.3390/jpm12030502] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Revised: 03/16/2022] [Accepted: 03/17/2022] [Indexed: 02/04/2023] Open
Abstract
The RPGR gene encodes Retinitis Pigmentosa GTPase Regulator, a known interactor with ciliary proteins, which is involved in maintaining healthy photoreceptor cells. Variants in RPGR are the main contributor to X-linked rod-cone dystrophy (RCD), and RPGR gene therapy approaches are in clinical trials. Hence, elucidation of the pathogenicity of novel RPGR variants is important for a patient therapy opportunity. Here, we describe a novel intronic RPGR variant, c.1415 − 9A>G, in a patient with RCD, which was classified as a variant of uncertain significance according to current clinical diagnostic criteria. The variant lay several base pairs intronic to the canonical splice acceptor site, raising suspicion of an RPGR RNA splicing abnormality and consequent protein dysfunction. To investigate disease causation in an appropriate disease model, induced pluripotent stem cells were generated from patient fibroblasts and differentiated to retinal pigment epithelium (iPSC-RPE) and retinal organoids (iPSC-RO). Abnormal RNA splicing of RPGR was demonstrated in patient fibroblasts, iPSC-RPE and iPSC-ROs, leading to a predicted frameshift and premature stop codon. Decreased RPGR expression was demonstrated in these cell types, with a striking loss of RPGR localization at the ciliary transitional zone, critically in the photoreceptor cilium of the patient iPSC-ROs. Mislocalisation of rhodopsin staining was present in the patient’s iPSC-RO rod photoreceptor cells, along with an abnormality of L/M opsin staining affecting cone photoreceptor cells and increased photoreceptor apoptosis. Additionally, patient iPSC-ROs displayed an increase in F-actin expression that was consistent with an abnormal actin regulation phenotype. Collectively, these studies indicate that the splicing abnormality caused by the c.1415 − 9A>G variant has an impact on RPGR function. This work has enabled the reclassification of this variant to pathogenic, allowing the consideration of patients with this variant having access to gene therapy clinical trials. In addition, we have identified biomarkers of disease suitable for the interrogation of other RPGR variants of uncertain significance.
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Affiliation(s)
- Fidelle Chahine Karam
- Eye Genetics Research Unit, Children’s Medical Research Institute, Sydney Children’s Hospitals Network, Save Sight Institute, University of Sydney, Westmead, Sydney 2145, Australia; (F.C.K.); (T.H.L.); (A.M.); (B.M.N.); (J.R.G.)
| | - To Ha Loi
- Eye Genetics Research Unit, Children’s Medical Research Institute, Sydney Children’s Hospitals Network, Save Sight Institute, University of Sydney, Westmead, Sydney 2145, Australia; (F.C.K.); (T.H.L.); (A.M.); (B.M.N.); (J.R.G.)
| | - Alan Ma
- Eye Genetics Research Unit, Children’s Medical Research Institute, Sydney Children’s Hospitals Network, Save Sight Institute, University of Sydney, Westmead, Sydney 2145, Australia; (F.C.K.); (T.H.L.); (A.M.); (B.M.N.); (J.R.G.)
- Department of Clinical Genetics, Western Sydney Genetics Program, Sydney Children’s Hospitals Network, Westmead, Sydney 2145, Australia
- Specialty of Genomic Medicine, Faculty of Medicine and Health, University of Sydney, Westmead, Sydney 2145, Australia; (E.F.); (B.B.)
| | - Benjamin M. Nash
- Eye Genetics Research Unit, Children’s Medical Research Institute, Sydney Children’s Hospitals Network, Save Sight Institute, University of Sydney, Westmead, Sydney 2145, Australia; (F.C.K.); (T.H.L.); (A.M.); (B.M.N.); (J.R.G.)
- Specialty of Genomic Medicine, Faculty of Medicine and Health, University of Sydney, Westmead, Sydney 2145, Australia; (E.F.); (B.B.)
- Sydney Genome Diagnostics, Western Sydney Genetics Program, Sydney Children’s Hospitals Network, Westmead, Sydney 2145, Australia
| | - John R. Grigg
- Eye Genetics Research Unit, Children’s Medical Research Institute, Sydney Children’s Hospitals Network, Save Sight Institute, University of Sydney, Westmead, Sydney 2145, Australia; (F.C.K.); (T.H.L.); (A.M.); (B.M.N.); (J.R.G.)
- Specialty of Ophthalmology, Faculty of Medicine and Health, University of Sydney, Sydney 2006, Australia
| | - Darshan Parekh
- Rare Diseases Functional Genomics Laboratory, Sydney Children’s Hospitals Network and Children’s Medical Research Institute, Westmead, Sydney 2145, Australia; (D.P.); (L.G.R.)
| | - Lisa G. Riley
- Rare Diseases Functional Genomics Laboratory, Sydney Children’s Hospitals Network and Children’s Medical Research Institute, Westmead, Sydney 2145, Australia; (D.P.); (L.G.R.)
- Specialty of Child and Adolescent Health, University of Sydney, Westmead, Sydney 2145, Australia
| | - Elizabeth Farnsworth
- Specialty of Genomic Medicine, Faculty of Medicine and Health, University of Sydney, Westmead, Sydney 2145, Australia; (E.F.); (B.B.)
- Sydney Genome Diagnostics, Western Sydney Genetics Program, Sydney Children’s Hospitals Network, Westmead, Sydney 2145, Australia
| | - Bruce Bennetts
- Specialty of Genomic Medicine, Faculty of Medicine and Health, University of Sydney, Westmead, Sydney 2145, Australia; (E.F.); (B.B.)
- Sydney Genome Diagnostics, Western Sydney Genetics Program, Sydney Children’s Hospitals Network, Westmead, Sydney 2145, Australia
| | - Anai Gonzalez-Cordero
- Stem Cell Medicine Group, Children’s Medical Research Institute, University of Sydney, Westmead, Sydney 2145, Australia;
- School of Medical Sciences, Faculty of Medicine and Health, University of Sydney, Sydney 2006, Australia
| | - Robyn V. Jamieson
- Eye Genetics Research Unit, Children’s Medical Research Institute, Sydney Children’s Hospitals Network, Save Sight Institute, University of Sydney, Westmead, Sydney 2145, Australia; (F.C.K.); (T.H.L.); (A.M.); (B.M.N.); (J.R.G.)
- Department of Clinical Genetics, Western Sydney Genetics Program, Sydney Children’s Hospitals Network, Westmead, Sydney 2145, Australia
- Specialty of Genomic Medicine, Faculty of Medicine and Health, University of Sydney, Westmead, Sydney 2145, Australia; (E.F.); (B.B.)
- Correspondence: ; Tel.: +61-2-9687-2800; Fax: +61-2-9687-2120
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9
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Covello G, Ibrahim GH, Bacchi N, Casarosa S, Denti MA. Exon Skipping Through Chimeric Antisense U1 snRNAs to Correct Retinitis Pigmentosa GTPase-Regulator ( RPGR) Splice Defect. Nucleic Acid Ther 2022; 32:333-349. [PMID: 35166581 PMCID: PMC9416563 DOI: 10.1089/nat.2021.0053] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Inherited retinal dystrophies are caused by mutations in more than 250 genes, each of them carrying several types of mutations that can lead to different clinical phenotypes. Mutations in Retinitis Pigmentosa GTPase-Regulator (RPGR) cause X-linked Retinitis pigmentosa (RP). A nucleotide substitution in intron 9 of RPGR causes the increase of an alternatively spliced isoform of the mature mRNA, bearing exon 9a (E9a). This introduces a stop codon, leading to truncation of the protein. Aiming at restoring impaired gene expression, we developed an antisense RNA-based therapeutic approach for the skipping of RPGR E9a. We designed a set of specific U1 antisense snRNAs (U1_asRNAs) and tested their efficacy in vitro, upon transient cotransfection with RPGR minigene reporter systems in HEK-293T, 661W, and PC-12 cell lines.
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Affiliation(s)
- Giuseppina Covello
- RNA Biology and Biotechnology Laboratory, Department of Cellular, Computational and Integrative Biology - CIBIO, University of Trento, Trento, Italy
| | - Gehan H Ibrahim
- Department of Medical Biochemistry, Faculty of Medicine, Suez Canal University, Ismailia, Egypt
| | - Niccolò Bacchi
- RNA Biology and Biotechnology Laboratory, Department of Cellular, Computational and Integrative Biology - CIBIO, University of Trento, Trento, Italy
| | - Simona Casarosa
- Neural Development and Regeneration Laboratory, Department of Cellular, Computational and Integrative Biology - CIBIO, University of Trento, Trento, Italy.,Centre for Medical Science - CIS Med, University of Trento, Trento, Italy.,CNR Neuroscience Institute, Pisa, Italy
| | - Michela Alessandra Denti
- RNA Biology and Biotechnology Laboratory, Department of Cellular, Computational and Integrative Biology - CIBIO, University of Trento, Trento, Italy.,CNR Neuroscience Institute, Pisa, Italy
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10
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Georgiou M, Awadh Hashem S, Daich Varela M, Michaelides M. Gene Therapy in X-linked Retinitis Pigmentosa Due to Defects in RPGR. Int Ophthalmol Clin 2021; 61:97-108. [PMID: 34584047 DOI: 10.1097/iio.0000000000000384] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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11
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Yang C, Georgiou M, Atkinson R, Collin J, Al-Aama J, Nagaraja-Grellscheid S, Johnson C, Ali R, Armstrong L, Mozaffari-Jovin S, Lako M. Pre-mRNA Processing Factors and Retinitis Pigmentosa: RNA Splicing and Beyond. Front Cell Dev Biol 2021; 9:700276. [PMID: 34395430 PMCID: PMC8355544 DOI: 10.3389/fcell.2021.700276] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Accepted: 07/09/2021] [Indexed: 12/20/2022] Open
Abstract
Retinitis pigmentosa (RP) is the most common inherited retinal disease characterized by progressive degeneration of photoreceptors and/or retinal pigment epithelium that eventually results in blindness. Mutations in pre-mRNA processing factors (PRPF3, 4, 6, 8, 31, SNRNP200, and RP9) have been linked to 15–20% of autosomal dominant RP (adRP) cases. Current evidence indicates that PRPF mutations cause retinal specific global spliceosome dysregulation, leading to mis-splicing of numerous genes that are involved in a variety of retina-specific functions and/or general biological processes, including phototransduction, retinol metabolism, photoreceptor disk morphogenesis, retinal cell polarity, ciliogenesis, cytoskeleton and tight junction organization, waste disposal, inflammation, and apoptosis. Importantly, additional PRPF functions beyond RNA splicing have been documented recently, suggesting a more complex mechanism underlying PRPF-RPs driven disease pathogenesis. The current review focuses on the key RP-PRPF genes, depicting the current understanding of their roles in RNA splicing, impact of their mutations on retinal cell’s transcriptome and phenome, discussed in the context of model species including yeast, zebrafish, and mice. Importantly, information on PRPF functions beyond RNA splicing are discussed, aiming at a holistic investigation of PRPF-RP pathogenesis. Finally, work performed in human patient-specific lab models and developing gene and cell-based replacement therapies for the treatment of PRPF-RPs are thoroughly discussed to allow the reader to get a deeper understanding of the disease mechanisms, which we believe will facilitate the establishment of novel and better therapeutic strategies for PRPF-RP patients.
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Affiliation(s)
- Chunbo Yang
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Maria Georgiou
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Robert Atkinson
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Joseph Collin
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Jumana Al-Aama
- Faculty of Medicine, King Abdulaziz University, Jeddah, Saudi Arabia
| | | | - Colin Johnson
- Leeds Institute of Molecular Medicine, University of Leeds, Leeds, United Kingdom
| | - Robin Ali
- King's College London, London, United Kingdom
| | - Lyle Armstrong
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Sina Mozaffari-Jovin
- Medical Genetics Research Center, Mashhad University of Medical Sciences, Mashhad, Iran.,Department of Medical Genetics, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran.,Department of Cellular Biochemistry, Max Planck Institute for Biophysical Chemistry, Göttingen, Germany
| | - Majlinda Lako
- Biosciences Institute, Newcastle University, Newcastle upon Tyne, United Kingdom
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12
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Hadalin V, Šuštar M, Volk M, Maver A, Sajovic J, Jarc-Vidmar M, Peterlin B, Hawlina M, Fakin A. Cone Dystrophy Associated with a Novel Variant in the Terminal Codon of the RPGR- ORF15. Genes (Basel) 2021; 12:genes12040499. [PMID: 33805381 PMCID: PMC8066792 DOI: 10.3390/genes12040499] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2021] [Revised: 03/23/2021] [Accepted: 03/24/2021] [Indexed: 12/30/2022] Open
Abstract
Mutations in RPGRORF15 are associated with rod-cone or cone/cone-rod dystrophy, the latter associated with mutations at the distal end. We describe the phenotype associated with a novel variant in the terminal codon of the RPGRORF15 c.3457T>A (Ter1153Lysext*38), which results in a C-terminal extension. Three male patients from two families were recruited, aged 31, 35, and 38 years. Genetic testing was performed by whole exome sequencing. Filtered variants were analysed according to the population frequency, ClinVar database, the variant’s putative impact, and predicted pathogenicity; and were classified according to the ACMG guidelines. Examination included visual acuity (Snellen), colour vision (Ishihara), visual field, fundus autofluorescence (FAF), optical coherence tomography (OCT), and electrophysiology. All patients were myopic, and had central scotoma and reduced colour vision. Visual acuities on better eyes were counting fingers, 0.3 and 0.05. Electrophysiology showed severely reduced cone-specific responses and macular dysfunction, while the rod-specific response was normal. FAF showed hyperautofluorescent ring centred at the fovea encompassing an area of photoreceptor loss approximately two optic discs in diameter (3462–6342 μm). Follow up after 2–11 years showed enlargement of the diameter (avg. 100 μm/year). The novel c.3457T>A (Ter1153Lysext*38) mutation in the terminal RPGRORF15 codon is associated with cone dystrophy, which corresponds to the previously described phenotypes associated with mutations in the distal end of the RPGRORF15. Minimal progression during follow-up years suggests a relatively stable disease after the initial loss of the central cones.
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Affiliation(s)
- Vlasta Hadalin
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia; (V.H.); (M.Š.); (J.S.); (M.J.-V.); (M.H.)
| | - Maja Šuštar
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia; (V.H.); (M.Š.); (J.S.); (M.J.-V.); (M.H.)
| | - Marija Volk
- Clinical Institute of Medical Genetics, University Medical Centre Ljubljana, Šlajmerjeva ulica 4, 1000 Ljubljana, Slovenia; (M.V.); (A.M.); (B.P.)
| | - Aleš Maver
- Clinical Institute of Medical Genetics, University Medical Centre Ljubljana, Šlajmerjeva ulica 4, 1000 Ljubljana, Slovenia; (M.V.); (A.M.); (B.P.)
| | - Jana Sajovic
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia; (V.H.); (M.Š.); (J.S.); (M.J.-V.); (M.H.)
| | - Martina Jarc-Vidmar
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia; (V.H.); (M.Š.); (J.S.); (M.J.-V.); (M.H.)
| | - Borut Peterlin
- Clinical Institute of Medical Genetics, University Medical Centre Ljubljana, Šlajmerjeva ulica 4, 1000 Ljubljana, Slovenia; (M.V.); (A.M.); (B.P.)
| | - Marko Hawlina
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia; (V.H.); (M.Š.); (J.S.); (M.J.-V.); (M.H.)
| | - Ana Fakin
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia; (V.H.); (M.Š.); (J.S.); (M.J.-V.); (M.H.)
- Correspondence:
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13
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Moreno-Leon L, West EL, O’Hara-Wright M, Li L, Nair R, He J, Anand M, Sahu B, Chavali VRM, Smith AJ, Ali RR, Jacobson SG, Cideciyan AV, Khanna H. RPGR isoform imbalance causes ciliary defects due to exon ORF15 mutations in X-linked retinitis pigmentosa (XLRP). Hum Mol Genet 2021; 29:3706-3716. [PMID: 33355362 PMCID: PMC7823108 DOI: 10.1093/hmg/ddaa269] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 12/03/2020] [Accepted: 12/09/2020] [Indexed: 12/28/2022] Open
Abstract
Mutations in retinitis pigmentosa GTPase regulator (RPGR) cause severe retinal ciliopathy, X-linked retinitis pigmentosa. Although two major alternatively spliced isoforms, RPGRex1-19 and RPGRORF15, are expressed, the relative importance of these isoforms in disease pathogenesis is unclear. Here, we analyzed fibroblast samples from eight patients and found that all of them form longer cilia than normal controls, albeit to different degrees. Although all mutant RPGRORF15 messenger RNAs (mRNAs) are unstable, their steady-state levels were similar or higher than those in the control cells, suggesting there may be increased transcription. Three of the fibroblasts that had higher levels of mutant RPGRORF15 mRNA also exhibited significantly higher levels of RPGRex1-19 mRNA. Four samples with unaltered RPGRex1-19 levels carried mutations in RPGRORF15 that resulted in this isoform being relatively less stable. Thus, in all cases, the RPGRex1-19/RPGRORF15 isoform ratio was increased, and this was highly correlative to the cilia extension defect. Moreover, overexpression of RPGRex1-19 (mimicking the increase in RPGRex1-19 to RPGRORF15 isoform ratio) or RPGRORF15 (mimicking reduction of the ratio) resulted in significantly longer or shorter cilia, respectively. Notably, the cilia length defect appears to be attributable to both the loss of the wild-type RPGRORF15 protein and to the higher levels of the RPGRex1-19 isoform, indicating that the observed defect is due to the altered isoform ratios. These results suggest that maintaining the optimal RPGRex1-9 to RPGRORF15 ratio is critical for cilia growth and that designing strategies that focus on the best ways to restore the RPGRex1-19/RPGRORF15 ratio may lead to better therapeutic outcomes.
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Affiliation(s)
- Laura Moreno-Leon
- Department of Ophthalmology & Visual Sciences, UMass Medical School, Worcester, MA 01655, USA
| | - Emma L West
- Division of Molecular Therapy, UCL Institute of Ophthalmology, London EC1V 9El, UK
| | | | - Linjing Li
- Department of Ophthalmology & Visual Sciences, UMass Medical School, Worcester, MA 01655, USA
| | - Rohini Nair
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Jie He
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Manisha Anand
- Department of Ophthalmology & Visual Sciences, UMass Medical School, Worcester, MA 01655, USA
| | - Bhubanananda Sahu
- Department of Ophthalmology & Visual Sciences, UMass Medical School, Worcester, MA 01655, USA
| | | | - Alexander J Smith
- Division of Molecular Therapy, UCL Institute of Ophthalmology, London EC1V 9El, UK
| | - Robin R Ali
- Division of Molecular Therapy, UCL Institute of Ophthalmology, London EC1V 9El, UK
| | - Samuel G Jacobson
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Artur V Cideciyan
- Department of Ophthalmology, Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Hemant Khanna
- Department of Ophthalmology & Visual Sciences, UMass Medical School, Worcester, MA 01655, USA
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14
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Aluru N, Karchner SI. PCB126 Exposure Revealed Alterations in m6A RNA Modifications in Transcripts Associated With AHR Activation. Toxicol Sci 2021; 179:84-94. [PMID: 33064826 PMCID: PMC8453794 DOI: 10.1093/toxsci/kfaa158] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Chemical modifications of proteins, DNA, and RNA moieties play critical roles in regulating gene expression. Emerging evidence suggests the RNA modifications (epitranscriptomics) have substantive roles in basic biological processes. One of the most common modifications in mRNA and noncoding RNAs is N6-methyladenosine (m6A). In a subset of mRNAs, m6A sites are preferentially enriched near stop codons, in 3' UTRs, and within exons, suggesting an important role in the regulation of mRNA processing and function including alternative splicing and gene expression. Very little is known about the effect of environmental chemical exposure on m6A modifications. As many of the commonly occurring environmental contaminants alter gene expression profiles and have detrimental effects on physiological processes, it is important to understand the effects of exposure on this important layer of gene regulation. Hence, the objective of this study was to characterize the acute effects of developmental exposure to PCB126, an environmentally relevant dioxin-like PCB, on m6A methylation patterns. We exposed zebrafish embryos to PCB126 for 6 h starting from 72 h post fertilization and profiled m6A RNA using methylated RNA immunoprecipitation followed by sequencing (MeRIP-seq). Our analysis revealed 117 and 217 m6A peaks in the DMSO and PCB126 samples (false discovery rate 5%), respectively. The majority of the peaks were preferentially located around the 3' UTR and stop codons. Statistical analysis revealed 15 m6A marked transcripts to be differentially methylated by PCB126 exposure. These include transcripts that are known to be activated by AHR agonists (eg, ahrra, tiparp, nfe2l2b) as well as others that are important for normal development (vgf, cebpd, sned1). These results suggest that environmental chemicals such as dioxin-like PCBs could affect developmental gene expression patterns by altering m6A levels. Further studies are necessary to understand the functional consequences of exposure-associated alterations in m6A levels.
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Affiliation(s)
- Neelakanteswar Aluru
- Biology Department and Woods Hole Center for Oceans and Human Health, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
| | - Sibel I Karchner
- Biology Department and Woods Hole Center for Oceans and Human Health, Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543
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15
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Translational Read-Through Therapy of RPGR Nonsense Mutations. Int J Mol Sci 2020; 21:ijms21228418. [PMID: 33182541 PMCID: PMC7697989 DOI: 10.3390/ijms21228418] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 10/28/2020] [Accepted: 11/05/2020] [Indexed: 12/14/2022] Open
Abstract
X-chromosomal retinitis pigmentosa (RP) frequently is caused by mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene. We evaluated the potential of PTC124 (Ataluren, TranslamaTM) treatment to promote ribosomal read-through of premature termination codons (PTC) in RPGR. Expression constructs in HEK293T cells showed that the efficacy of read-through reagents is higher for UGA than UAA PTCs. We identified the novel hemizygous nonsense mutation c.1154T > A, p.Leu385* (NM_000328.3) causing a UAA PTC in RPGR and generated patient-derived fibroblasts. Immunocytochemistry of serum-starved control fibroblasts showed the RPGR protein in a dot-like expression pattern along the primary cilium. In contrast, RPGR was no longer detectable at the primary cilium in patient-derived cells. Applying PTC124 restored RPGR at the cilium in approximately 8% of patient-derived cells. RT-PCR and Western blot assays verified the pathogenic mechanisms underlying the nonsense variant. Immunofluorescence stainings confirmed the successful PTC124 treatment. Our results showed for the first time that PTC124 induces read-through of PTCs in RPGR and restores the localization of the RPGR protein at the primary cilium in patient-derived cells. These results may provide a promising new treatment option for patients suffering from nonsense mutations in RPGR or other genetic diseases.
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16
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De Silva SR, Arno G, Robson AG, Fakin A, Pontikos N, Mohamed MD, Bird AC, Moore AT, Michaelides M, Webster AR, Mahroo OA. The X-linked retinopathies: Physiological insights, pathogenic mechanisms, phenotypic features and novel therapies. Prog Retin Eye Res 2020; 82:100898. [PMID: 32860923 DOI: 10.1016/j.preteyeres.2020.100898] [Citation(s) in RCA: 65] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 08/07/2020] [Accepted: 08/21/2020] [Indexed: 02/08/2023]
Abstract
X-linked retinopathies represent a significant proportion of monogenic retinal disease. They include progressive and stationary conditions, with and without syndromic features. Many are X-linked recessive, but several exhibit a phenotype in female carriers, which can help establish diagnosis and yield insights into disease mechanisms. The presence of affected carriers can misleadingly suggest autosomal dominant inheritance. Some disorders (such as RPGR-associated retinopathy) show diverse phenotypes from variants in the same gene and also highlight limitations of current genetic sequencing methods. X-linked disease frequently arises from loss of function, implying potential for benefit from gene replacement strategies. We review X-inactivation and X-linked inheritance, and explore burden of disease attributable to X-linked genes in our clinically and genetically characterised retinal disease cohort, finding correlation between gene transcript length and numbers of families. We list relevant genes and discuss key clinical features, disease mechanisms, carrier phenotypes and novel experimental therapies. We consider in detail the following: RPGR (associated with retinitis pigmentosa, cone and cone-rod dystrophy), RP2 (retinitis pigmentosa), CHM (choroideremia), RS1 (X-linked retinoschisis), NYX (complete congenital stationary night blindness (CSNB)), CACNA1F (incomplete CSNB), OPN1LW/OPN1MW (blue cone monochromacy, Bornholm eye disease, cone dystrophy), GPR143 (ocular albinism), COL4A5 (Alport syndrome), and NDP (Norrie disease and X-linked familial exudative vitreoretinopathy (FEVR)). We use a recently published transcriptome analysis to explore expression by cell-type and discuss insights from electrophysiology. In the final section, we present an algorithm for genes to consider in diagnosing males with non-syndromic X-linked retinopathy, summarise current experimental therapeutic approaches, and consider questions for future research.
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Affiliation(s)
- Samantha R De Silva
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Gavin Arno
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Anthony G Robson
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Ana Fakin
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK; Ljubljana University Medical Centre, Ljubljana, Slovenia
| | - Nikolas Pontikos
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Moin D Mohamed
- Department of Ophthalmology, Guy's & St Thomas' NHS Foundation Trust, London, UK
| | - Alan C Bird
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Anthony T Moore
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK; Department of Ophthalmology, UCSF School of Medicine, San Francisco, CA, USA
| | - Michel Michaelides
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Andrew R Webster
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Omar A Mahroo
- UCL Institute of Ophthalmology, University College London, UK; Moorfields Eye Hospital NHS Foundation Trust, London, UK; Department of Ophthalmology, Guy's & St Thomas' NHS Foundation Trust, London, UK; Section of Ophthalmology, King's College London, UK; Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK.
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17
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Abstract
PURPOSE To examine the features of the tapetal-like reflex (TLR) in female carriers of RPGR-associated retinopathy by means of adaptive optics scanning light ophthalmoscopy (AOSLO) and spectral domain optical coherence tomography. METHODS Nine molecularly confirmed RPGR carriers and three healthy controls underwent ocular examination and the following retinal imaging modalities: color photography, near-infrared reflectance, fundus autofluorescence, spectral domain optical coherence tomography, and AOSLO. After identifying TLR areas across all imaging modalities, normalized local contrast of outer retinal bands on spectral domain optical coherence tomography was calculated and AOSLO-acquired photoreceptor mosaic analysis was performed. RESULTS Seven carriers had TLR areas, which colocalized with increased rod photoreceptor reflectivity on confocal AOSLO and reduced cone photoreceptor densities. Parafoveal TLR areas also exhibited reduced local contrast (i.e., increased reflectivity) of the outer retinal bands on spectral domain optical coherence tomography (inner segment ellipsoid zone and outer segment interdigitation zone). Healthy controls did not show TLR. CONCLUSION The cellular resolution provided by AOSLO affords the characterization of the photoreceptor mosaic in RPGR carriers with a TLR. Features revealed include reduced cone density, increased cone inner segment diameter, and increased rod outer segment reflectivity.
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18
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Menghini M, Jolly JK, Nanda A, Wood L, Cehajic-Kapetanovic J, MacLaren RE. Early Cone Photoreceptor Outer Segment Length Shortening in RPGR X-Linked Retinitis Pigmentosa. Ophthalmologica 2020; 244:281-290. [PMID: 32209785 DOI: 10.1159/000507484] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 03/24/2020] [Indexed: 11/19/2022]
Abstract
INTRODUCTION Introduction of retinal gene therapy requires established outcome measures along with thorough understanding of the pathophysiology. Evidence of early, thinned outer segments in RPGR X-linked retinitis pigmentosa could help understand how the level of cone photoreceptor involvement translates to visual potential. OBJECTIVE Analysis of foveal photoreceptor outer segment length in a young cohort of RPGR patients to help clarify the reason for absent maximal visual acuity seen. METHODS Case-control study of RPGR patients. Quantitative measurement of photoreceptor outer segment by OCT. RESULTS Eighteen male RPGR patients and 30 normal subjects were included. Outer segment thickness differed significantly between the RPGR and normal eyes (p < 0.0005). Mean outer segment values were 35.6 ± 2.3 µm and 35.4 ± 2.6 µm for RPGR right and left eyes, respectively. In normal eyes, the mean outer segment thickness was 61.4 ± 0.7 µm for right eyes and 62.4 ± 0.7 µm for left eyes. CONCLUSIONS Patients with RPGR X-linked retinitis pigmentosa show thinning of the foveal photoreceptor outer segment thickness early in the disease course, which could be an explanation for the lower maximum visual acuity seen. These findings must be taken into consideration when assessing efficacy outcome measures in retinal gene therapy trials.
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Affiliation(s)
- Moreno Menghini
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, Oxford University, Oxford, UK,
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK,
| | - Jasleen K Jolly
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, Oxford University, Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Anika Nanda
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, Oxford University, Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Laura Wood
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, Oxford University, Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Jasmina Cehajic-Kapetanovic
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, Oxford University, Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
| | - Robert E MacLaren
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neurosciences, Oxford University, Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK
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19
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Barabino A, Flamier A, Hanna R, Héon E, Freedman BS, Bernier G. Deregulation of Neuro-Developmental Genes and Primary Cilium Cytoskeleton Anomalies in iPSC Retinal Sheets from Human Syndromic Ciliopathies. Stem Cell Reports 2020; 14:357-373. [PMID: 32160518 PMCID: PMC7066374 DOI: 10.1016/j.stemcr.2020.02.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2019] [Revised: 02/10/2020] [Accepted: 02/11/2020] [Indexed: 01/22/2023] Open
Abstract
Ciliopathies are heterogeneous genetic diseases affecting primary cilium structure and function. Meckel-Gruber (MKS) and Bardet-Biedl (BBS) syndromes are severe ciliopathies characterized by skeletal and neurodevelopment anomalies, including polydactyly, cognitive impairment, and retinal degeneration. We describe the generation and molecular characterization of human induced pluripotent stem cell (iPSC)-derived retinal sheets (RSs) from controls, and MKS (TMEM67) and BBS (BBS10) cases. MKS and BBS RSs displayed significant common alterations in the expression of hundreds of developmental genes and members of the WNT and BMP pathways. Induction of crystallin molecular chaperones was prominent in MKS and BBS RSs suggesting a stress response to misfolded proteins. Unique to MKS photoreceptors was the presence of supernumerary centrioles and cilia, and aggregation of ciliary proteins. Unique to BBS photoreceptors was the accumulation of DNA damage and activation of the mitotic spindle checkpoint. This study reveals how combining cell reprogramming, organogenesis, and next-generation sequencing enables the elucidation of mechanisms involved in human ciliopathies.
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Affiliation(s)
- Andrea Barabino
- Stem Cell and Developmental Biology Laboratory, Hôpital Maisonneuve-Rosemont, 5415 Boul. Assomption, Montreal, QC H1T 2M4, Canada
| | - Anthony Flamier
- Stem Cell and Developmental Biology Laboratory, Hôpital Maisonneuve-Rosemont, 5415 Boul. Assomption, Montreal, QC H1T 2M4, Canada
| | - Roy Hanna
- Stem Cell and Developmental Biology Laboratory, Hôpital Maisonneuve-Rosemont, 5415 Boul. Assomption, Montreal, QC H1T 2M4, Canada
| | - Elise Héon
- Hospital for Sick Children, Department of Ophthalmology and Vision Sciences, Program of Genetics and Genome Biology, 555 University av., Toronto, ON M5G 1X8, Canada
| | - Benjamin S Freedman
- Department of Medicine, Division of Nephrology, Kidney Research Institute, and Institute of Stem Cell and Regenerative Medicine, and Department of Pathology, University of Washington School of Medicine, Seattle, WA 98109, USA.
| | - Gilbert Bernier
- Stem Cell and Developmental Biology Laboratory, Hôpital Maisonneuve-Rosemont, 5415 Boul. Assomption, Montreal, QC H1T 2M4, Canada; Department of Neurosciences, University of Montreal, Montreal, QC H3C 3J7, Canada; Department of Ophthalmology, University of Montreal, Montreal, QC H3C 3J7, Canada.
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20
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Cehajic Kapetanovic J, McClements ME, Martinez-Fernandez de la Camara C, MacLaren RE. Molecular Strategies for RPGR Gene Therapy. Genes (Basel) 2019; 10:genes10090674. [PMID: 31487940 PMCID: PMC6770968 DOI: 10.3390/genes10090674] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 08/27/2019] [Accepted: 09/01/2019] [Indexed: 11/16/2022] Open
Abstract
Mutations affecting the Retinitis Pigmentosa GTPase Regulator (RPGR) gene are the commonest cause of X-linked and recessive retinitis pigmentosa (RP), accounting for 10%-20% of all cases of RP. The phenotype is one of the most severe amongst all causes of RP, characteristic for its early onset and rapid progression to blindness in young people. At present there is no cure for RPGR-related retinal disease. Recently, however, there have been important advances in RPGR research from bench to bedside that increased our understanding of RPGR function and led to the development of potential therapies, including the progress of adeno-associated viral (AAV)-mediated gene replacement therapy into clinical trials. This manuscript discusses the advances in molecular research, which have connected the RPGR protein with an important post-translational modification, known as glutamylation, that is essential for its optimal function as a key regulator of photoreceptor ciliary transport. In addition, we review key pre-clinical research that addressed challenges encountered during development of therapeutic vectors caused by high infidelity of the RPGR genomic sequence. Finally, we discuss the structure of three current phase I/II clinical trials based on three AAV vectors and RPGR sequences and link the rationale behind the use of the different vectors back to the bench research that led to their development.
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Affiliation(s)
- Jasmina Cehajic Kapetanovic
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford OX3 9DU, UK. '
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, UK. '
| | | | - Cristina Martinez-Fernandez de la Camara
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford OX3 9DU, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, UK
| | - Robert E MacLaren
- Nuffield Laboratory of Ophthalmology, University of Oxford, Oxford OX3 9DU, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, UK
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Khanna H. More Than Meets the Eye: Current Understanding of RPGR Function. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1074:521-538. [PMID: 29721984 DOI: 10.1007/978-3-319-75402-4_64] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/15/2023]
Abstract
This article summarizes the recent advances in our understanding of a major retinal disease gene RPGR (retinitis pigmentosa GTPase regulator), mutations in which are associated with majority of X-linked forms of retinal degenerations. A great deal of work has been done to uncover the ciliary localization of RPGR and its interacting proteins in the retina. However, the molecular mechanisms of action of RPGR in the photoreceptors are still unclear. Recent studies have begun to shed light on the intracellular pathways in which RPGR is likely involved. The deregulation of such pathways may underlie the pathogenesis of severe retinal degeneration associated with RPGR. With the recent advances in the gene augmentation therapy for RPGR-associated disease, there is a lot of excitement in the field. Patients with RPGR mutations, however, present with clinically heterogeneous manifestations. It is therefore imperative to examine the function of RPGR in detail, so that we can design patient-oriented therapeutic strategies for this disease.
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Affiliation(s)
- Hemant Khanna
- Department of Ophthalmology and Neurobiology, UMASS Medical School, Worcester, MA, USA.
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22
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Song C, Conlon TJ, Deng WT, Coleman KE, Zhu P, Plummer C, Mandapati S, Van Hoosear M, Green KB, Sonnentag P, Sharma AK, Timmers A, Robinson PM, Knop DR, Hauswirth WW, Chulay JD, Shearman MS, Ye GJ. Toxicology and Pharmacology of an AAV Vector Expressing Codon-Optimized RPGR in RPGR-Deficient Rd9 Mice. HUM GENE THER CL DEV 2019; 29:188-197. [PMID: 30280954 DOI: 10.1089/humc.2018.168] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Applied Genetic Technologies Corporation (AGTC) is developing a recombinant adeno-associated virus (rAAV) vector AGTC-501, also designated AAV2tYF-GRK1-RPGRco, to treat retinitis pigmentosa (RP) in patients with mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene. The vector contains a codon-optimized human RPGR cDNA (RPGRco) driven by a photoreceptor-specific promoter (G protein-coupled receptor kinase 1, GRK1) and is packaged in an AAV2 capsid with three surface tyrosine residues changed to phenylalanine (AAV2tYF). We conducted a safety and potency study of this vector administered by subretinal a injection in the naturally occurring RPGR-deficient Rd9 mouse model. Sixty Rd9 mice (20 per group) received a subretinal injection in the right eye of vehicle (control) or AAV2tYF-GRK1-RPGRco at one of two dose levels (4 × 108 or 4 × 109 vg/eye) and were followed for 12 weeks after injection. Vector injections were well tolerated, with no systemic toxicity. There was a trend towards reduced electroretinography b-wave amplitudes in the high vector dose group that was not statistically significant. There were no clinically important changes in hematology or clinical chemistry parameters and no vector-related ocular changes in life or by histological examination. Dose-dependent RPGR protein expression, mainly in the inner segment of photoreceptors and the adjacent connecting cilium region, was observed in all vector-treated eyes examined. Sequence integrity of the codon-optimized RPGR was confirmed by sequencing of PCR-amplified DNA, or cDNA reverse transcribed from total RNA extracted from vector-treated retinal tissues, and by sequencing of RPGR protein obtained from transfected HEK 293 cells. These results support the use of rAAV2tYF-GRK1-RPGRco in clinical studies in patients with XLRP caused by RPGR mutations.
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Affiliation(s)
- Chunjuan Song
- 1 Applied Genetic Technologies Corporation (AGTC), Alachua, FL
| | - Thomas J Conlon
- 2 CR Scientific and Compliance Consulting LLC, Gainesville, FL
| | - Wen-Tao Deng
- 3 Department of Ophthalmology, University of Florida, Gainesville, FL
| | - Kirsten E Coleman
- 3 Department of Ophthalmology, University of Florida, Gainesville, FL
| | - Ping Zhu
- 3 Department of Ophthalmology, University of Florida, Gainesville, FL
| | - Cayrn Plummer
- 3 Department of Ophthalmology, University of Florida, Gainesville, FL
| | | | | | - Kari B Green
- 4 Department of Chemistry, University of Florida, Gainesville, FL
| | | | | | - Adrian Timmers
- 1 Applied Genetic Technologies Corporation (AGTC), Alachua, FL
| | | | - David R Knop
- 1 Applied Genetic Technologies Corporation (AGTC), Alachua, FL
| | | | | | - Mark S Shearman
- 1 Applied Genetic Technologies Corporation (AGTC), Alachua, FL
| | - Guo-Jie Ye
- 1 Applied Genetic Technologies Corporation (AGTC), Alachua, FL
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Disruption of RPGR protein interaction network is the common feature of RPGR missense variations that cause XLRP. Proc Natl Acad Sci U S A 2019; 116:1353-1360. [PMID: 30622176 DOI: 10.1073/pnas.1817639116] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Retinitis pigmentosa (RP) is an inherited retinal degenerative disease with severe vision impairment leading to blindness. About 10-15% of RP cases are caused by mutations in the RPGR gene, with RPGR mutations accounting for 70% of X-linked RP cases. The mechanism by which RPGR mutations cause photoreceptor cell dysfunction is not well understood. In this study, we show that the two isoforms of RPGR (RPGR1-19 and RPGRORF15) interact with endogenous PDE6D, INPP5E, and RPGRIP1L. The RPGR1-19 isoform contains two PDE6D binding sites with the C-terminal prenylation site being the predominant PDE6D binding site. The C terminus of RPGR1-19 that contains the prenylation site regulates its interaction with PDE6D, INPP5E, and RPGRIP1L. Only the RPGR1-19 isoform localizes to cilia in cultured RPE1 cells. Missense variations found in RPGR patients disrupt the interaction between RPGR isoforms and their endogenous interactors INPP5E, PDE6D, and RPGRIP1L. We evaluated a RPGR missense variation (M58K) found in a family with X-linked retinitis pigmentosa (XLRP) and show that this missense variation disrupts the interaction of RPGR isoforms with their endogenous interactors. The M58K variation also disrupts the ciliary localization of the RPGR1-19 isoform. Using this assay, we also show that some of the RPGR missense variants reported in the literature might not actually be disease causing. Our data establishes an in vitro assay that can be used to validate the potential pathogenicity of RPGR missense variants.
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Golden JR, Erickson-Davis C, Cottaris NP, Parthasarathy N, Rieke F, Brainard DH, Wandell BA, Chichilnisky EJ. Simulation of visual perception and learning with a retinal prosthesis. J Neural Eng 2018; 16:025003. [PMID: 30523985 DOI: 10.1088/1741-2552/aaf270] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
OBJECTIVE The nature of artificial vision with a retinal prosthesis, and the degree to which the brain can adapt to the unnatural input from such a device, are poorly understood. Therefore, the development of current and future devices may be aided by theory and simulations that help to infer and understand what prosthesis patients see. APPROACH A biologically-informed, extensible computational framework is presented here to predict visual perception and the potential effect of learning with a subretinal prosthesis. The framework relies on optimal linear reconstruction of the stimulus from retinal responses to infer the visual information available to the patient. A simulation of the physiological optics of the eye and light responses of the major retinal neurons was used to calculate the optimal linear transformation for reconstructing natural images from retinal activity. The result was then used to reconstruct the visual stimulus during the artificial activation expected from a subretinal prosthesis in a degenerated retina, as a proxy for inferred visual perception. MAIN RESULTS Several simple observations reveal the potential utility of such a simulation framework. The inferred perception obtained with prosthesis activation was substantially degraded compared to the inferred perception obtained with normal retinal responses, as expected given the limited resolution and lack of cell type specificity of the prosthesis. Consistent with clinical findings and the importance of cell type specificity, reconstruction using only ON cells, and not OFF cells, was substantially more accurate. Finally, when reconstruction was re-optimized for prosthesis stimulation, simulating the greatest potential for learning by the patient, the accuracy of inferred perception was much closer to that of healthy vision. SIGNIFICANCE The reconstruction approach thus provides a more complete method for exploring the potential for treating blindness with retinal prostheses than has been available previously. It may also be useful for interpreting patient data in clinical trials, and for improving prosthesis design.
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Sengillo JD, Fridman G, Cho GY, Buchovecky C, Tsang SH. Novel Mutation in Retinitis Pigmentosa GTPase Regulator Gene Causes Primary Ciliary Dyskinesia and Retinitis Pigmentosa. Ophthalmic Surg Lasers Imaging Retina 2018; 49:548-552. [DOI: 10.3928/23258160-20180628-14] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 04/25/2018] [Indexed: 11/20/2022]
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Martinez-Fernandez De La Camara C, Nanda A, Salvetti AP, Fischer MD, MacLaren RE. Gene therapy for the treatment of X-linked retinitis pigmentosa. Expert Opin Orphan Drugs 2018; 6:167-177. [PMID: 30057863 PMCID: PMC6059358 DOI: 10.1080/21678707.2018.1444476] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
INTRODUCTION X-linked retinitis pigmentosa caused by mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene is the most common form of recessive RP. The phenotype is characterised by its severity and rapid disease progression. Gene therapy using adeno-associated viral vectors is currently the most promising therapeutic approach. However, the construction of a stable vector encoding the full-length RPGR transcript has previously proven to be a limiting step towards gene therapy clinical trials. Recently however, a codon optimised version of RPGR has been shown to increase the stability and fidelity of the sequence, conferring a therapeutic effect in murine and canine animal models. AREAS COVERED This manuscript reviews the natural history of X-linked retinitis pigmentosa and the research performed from the discovery of the causative gene, RPGR, to the preclinical testing of potential therapies that have led to the initiation of three clinical trials. EXPERT OPINION X-linked retinitis pigmentosa is an amenable disease to be treated by gene therapy. Codon optimisation has overcome the challenge of designing an RPGR vector without mutations, and with a therapeutic effect in different animal models. With the RPGR gene therapy clinical trials still in the early stages, the confirmation of the safety, tolerability and potency of the therapy is still ongoing.
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Affiliation(s)
| | - Anika Nanda
- Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Trust, John Radcliffe Hospital, Oxford, UK
| | - Anna Paola Salvetti
- Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford, UK
- Department of Biomedical and Clinical Sciences “Luigi Sacco”, Sacco Hospital, University of Milan, Milano, Italy
| | - M. Dominik Fischer
- Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford, UK
- Centre for Ophthalmology Tübingen, University Eye Hospital, Tübingen, Germany
| | - Robert E. MacLaren
- Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, John Radcliffe Hospital, Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Trust, John Radcliffe Hospital, Oxford, UK
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27
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Rao KN, Zhang W, Li L, Anand M, Khanna H. Prenylated retinal ciliopathy protein RPGR interacts with PDE6δ and regulates ciliary localization of Joubert syndrome-associated protein INPP5E. Hum Mol Genet 2018; 25:4533-4545. [PMID: 28172980 DOI: 10.1093/hmg/ddw281] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 07/24/2016] [Accepted: 08/19/2016] [Indexed: 12/11/2022] Open
Abstract
Ciliary trafficking defects underlie the pathogenesis of severe human ciliopathies, including Joubert Syndrome (JBTS), Bardet-Biedl Syndrome, and some forms of retinitis pigmentosa (RP). Mutations in the ciliary protein RPGR (retinitis pigmentosa GTPase regulator) are common causes of RP-associated photoreceptor degeneration worldwide. While previous work has suggested that the localization of RPGR to cilia is critical to its functions, the mechanism by which RPGR and its associated cargo are trafficked to the cilia is unclear. Using proteomic and biochemical approaches, we show that RPGR interacts with two JBTS-associated ciliary proteins: PDE6δ (delta subunit of phosphodiesterase; a prenyl-binding protein) and INPP5E (inositol polyphosphate-5-phosphatase 5E). We find that PDE6δ binds selectively to the C-terminus of RPGR and that this interaction is critical for RPGR’s localization to cilia. Furthermore, we show that INPP5E associates with the N-terminus of RPGR and trafficking of INPP5E to cilia is dependent upon the ciliary localization of RPGR. These results implicate prenylation of RPGR as a critical modification for its localization to cilia and, in turn suggest that trafficking of INPP5E to cilia depends upon the interaction of RPGR with PDE6δ. Finally, our results implicate INPP5E, a novel RPGR-interacting protein, in the pathogenesis of RPGR-associated ciliopathies.
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Affiliation(s)
- Kollu N Rao
- Department of Ophthalmology, Horae Gene Therapy Center, UMASS Medical School, Worcester, MA, USA
| | - Wei Zhang
- Department of Ophthalmology, Horae Gene Therapy Center, UMASS Medical School, Worcester, MA, USA
| | - Linjing Li
- Department of Ophthalmology, Horae Gene Therapy Center, UMASS Medical School, Worcester, MA, USA
| | - Manisha Anand
- Department of Ophthalmology, Horae Gene Therapy Center, UMASS Medical School, Worcester, MA, USA
| | - Hemant Khanna
- Department of Ophthalmology, Horae Gene Therapy Center, UMASS Medical School, Worcester, MA, USA
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Tee JJL, Smith AJ, Hardcastle AJ, Michaelides M. RPGR-associated retinopathy: clinical features, molecular genetics, animal models and therapeutic options. Br J Ophthalmol 2016; 100:1022-7. [PMID: 26843488 DOI: 10.1136/bjophthalmol-2015-307698] [Citation(s) in RCA: 62] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2015] [Accepted: 01/02/2016] [Indexed: 11/04/2022]
Abstract
Retinitis pigmentosa GTPase regulator (RPGR) gene sequence variants account for the vast majority of X linked retinitis pigmentosa (RP), which is one of the most severe forms of RP. Symptoms of nyctalopia typically begin in childhood, with increasing loss of peripheral visual field during teenage years, and progressive central visual loss during the second to fourth decade of life. There is however marked intrafamilial and interfamilial phenotypic heterogeneity in affected males and carrier females. There is now a far greater understanding of the range of phenotypes associated with variants in this gene; including rod-cone dystrophy, cone-rod dystrophy, cone dystrophy, macular dystrophy and non-ocular phenotypes. There are also increasingly established genotype-phenotype associations and structure-function correlations. RPGR is involved in ciliary function, with ciliary dysfunction now recognised as the mechanism underlying a large proportion of inherited retinal disease. There has been significant progress in identifying naturally occurring animal models and developing novel models to define the underlying disease mechanisms and to test gene replacement therapy, in addition to advances in human retinal imaging, culminating in completed and planned clinical trials. These significant developments will be discussed.
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Affiliation(s)
- James J L Tee
- UCL Institute of Ophthalmology, University College London, London, UK Moorfields Eye Hospital, London, UK
| | - Alexander J Smith
- UCL Institute of Ophthalmology, University College London, London, UK Moorfields Eye Hospital, London, UK
| | - Alison J Hardcastle
- UCL Institute of Ophthalmology, University College London, London, UK Moorfields Eye Hospital, London, UK
| | - Michel Michaelides
- UCL Institute of Ophthalmology, University College London, London, UK Moorfields Eye Hospital, London, UK
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Rao KN, Li L, Zhang W, Brush RS, Rajala RVS, Khanna H. Loss of human disease protein retinitis pigmentosa GTPase regulator (RPGR) differentially affects rod or cone-enriched retina. Hum Mol Genet 2016; 25:1345-56. [PMID: 26908598 DOI: 10.1093/hmg/ddw017] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Accepted: 01/18/2016] [Indexed: 01/13/2023] Open
Abstract
It is unclear how genes, such as RPGR (retinitis pigmentosa guanine triphosphatase regulator) that are expressed in both rods and cones, cause variable disease pathogenesis. Using transcriptomic analysis, we show that loss of RPGR in a rod-dominant mouse retina (Rpgr(ko)) results in predominant alterations in genes involved in actin cytoskeletal dynamics, prior to onset of degeneration. We validated these findings and found an increase in activated RhoA-GTP levels and polymerized F-actin in the Rpgr(ko) mouse retina. To assess the effect of the loss of RPGR in the all-cone region of the human retina, we used Nrl(-/-) (neural retina leucine zipper) mice, to generate Rpgr(ko)::Nrl(-/-) double-knock-out (Rpgr-DKO) mice. These mice exhibited supranormal cone response to light and substantially retained retinal architecture. Transcriptomic analysis revealed predominant up-regulation of retinal pigmented epithelium (RPE)-specific genes associated with visual cycle, whereas fatty acid analysis showed mild decrease in docosahexaenoic acid in the retina of the Rpgr-DKO mice when compared with the Nrl(-/-) mice. Our data reveal new insights into distinct intracellular pathways that are involved in RPGR-associated rod and cone dysfunction and provide a platform to design new treatment modalities.
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Affiliation(s)
- Kollu N Rao
- Department of Ophthalmology, University of Massachusetts Medical School, 368 Plantation St, Albert Sherman Center AS6-2043, Worcester, MA 01605, USA and
| | - Linjing Li
- Department of Ophthalmology, University of Massachusetts Medical School, 368 Plantation St, Albert Sherman Center AS6-2043, Worcester, MA 01605, USA and
| | - Wei Zhang
- Department of Ophthalmology, University of Massachusetts Medical School, 368 Plantation St, Albert Sherman Center AS6-2043, Worcester, MA 01605, USA and
| | - Richard S Brush
- University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Raju V S Rajala
- University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Hemant Khanna
- Department of Ophthalmology, University of Massachusetts Medical School, 368 Plantation St, Albert Sherman Center AS6-2043, Worcester, MA 01605, USA and
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Deng WT, Dyka FM, Dinculescu A, Li J, Zhu P, Chiodo VA, Boye SL, Conlon TJ, Erger K, Cossette T, Hauswirth WW. Stability and Safety of an AAV Vector for Treating RPGR-ORF15 X-Linked Retinitis Pigmentosa. Hum Gene Ther 2015; 26:593-602. [PMID: 26076799 DOI: 10.1089/hum.2015.035] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Our collaborative successful gene replacement therapy using AAV vectors expressing a variant of human RPGR-ORF15 in two canine models provided therapeutic proof of concept for translation into human treatment. The ORF15 sequence contained within this AAV vector, however, has ORF15 DNA sequence variations compared to the published sequence that are likely due to its unusual composition of repetitive purine nucleotides. This mutability is a concern for AAV vector production and safety when contemplating a human trial. In this study, we establish the safety profile of AAV-hIRBP-hRPGR and AAV-hGRK1-hRPGR vectors used in the initial canine proof-of-principle experiments by demonstrating hRPGR-ORF15 sequence stability during all phases of manipulation, from plasmid propagation to vector production to its stability in vivo after subretinal administration to animals. We also evaluate potential toxicity in vivo by investigating protein expression, retinal structure and function, and vector biodistribution. Expression of hRPGR is detected in the inner segments and synaptic terminals of photoreceptors and is restricted to the connecting cilium when the vector is further diluted. Treated eyes exhibit no toxicity as assessed by retinal histopathology, immunocytochemistry, optical coherence tomography, fundoscopy, electroretinogram, and vector biodistribution. Therefore, the hRPGR-ORF15 variant in our AAV vectors appears to be a more stable form than the endogenous hRPGR cDNA when propagated in vitro. Its safety profile presented here in combination with its proven efficacy supports future gene therapy clinical trials.
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Affiliation(s)
- Wen-Tao Deng
- 1 Department of Ophthalmology, College of Medicine, University of Florida , Gainesville, Florida
| | - Frank M Dyka
- 1 Department of Ophthalmology, College of Medicine, University of Florida , Gainesville, Florida
| | - Astra Dinculescu
- 1 Department of Ophthalmology, College of Medicine, University of Florida , Gainesville, Florida
| | - Jie Li
- 1 Department of Ophthalmology, College of Medicine, University of Florida , Gainesville, Florida
| | - Ping Zhu
- 1 Department of Ophthalmology, College of Medicine, University of Florida , Gainesville, Florida
| | - Vince A Chiodo
- 1 Department of Ophthalmology, College of Medicine, University of Florida , Gainesville, Florida
| | - Sanford L Boye
- 1 Department of Ophthalmology, College of Medicine, University of Florida , Gainesville, Florida
| | - Thomas J Conlon
- 2 Powell Gene Therapy Center, Department of Pediatrics, University of Florida , Gainesville, Florida
| | - Kirsten Erger
- 2 Powell Gene Therapy Center, Department of Pediatrics, University of Florida , Gainesville, Florida
| | - Travis Cossette
- 2 Powell Gene Therapy Center, Department of Pediatrics, University of Florida , Gainesville, Florida
| | - William W Hauswirth
- 1 Department of Ophthalmology, College of Medicine, University of Florida , Gainesville, Florida
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Abstract
Retina is a neurosensory tissue lining the back of the eye and is responsible for light detection and relaying the signal to the visual cortex in the brain. Mammalian retina consists of six major types of neurons (including photoreceptors; rods and cones) and one type of glial cells arranged in distinct layers. Photoreceptors are the most abundant cell types accounting for approximately 60% of all cells in the retina. Owing to their unique structure and function as ciliated neurons and their vast majority, dysfunction and degeneration of photoreceptors is associated with several inherited blindness disorders, such as retinitis pigmentosa, cone-rod degeneration, and age-related macular degeneration. Therefore, it is imperative to examine the structure and function of photoreceptors so that better understanding of the pathogenesis of associated diseases can be obtained for designing therapeutic modalities. In this chapter, we will provide detailed methods for analyzing photoreceptor function (electroretinography), structure, and biochemical analysis of sensory cilia of photoreceptors using mammalian retina as model system. These methods are widely used to assess photoreceptor development and degeneration during disease.
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Affiliation(s)
- Linjing Li
- Department of Ophthalmology, UMASS Medical School, Worcester, MA, USA
| | - Manisha Anand
- Department of Ophthalmology, UMASS Medical School, Worcester, MA, USA
| | | | - Hemant Khanna
- Department of Ophthalmology, UMASS Medical School, Worcester, MA, USA
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32
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Zahid S, Khan N, Branham K, Othman M, Karoukis AJ, Sharma N, Moncrief A, Mahmood MN, Sieving PA, Swaroop A, Heckenlively JR, Jayasundera T. Phenotypic conservation in patients with X-linked retinitis pigmentosa caused by RPGR mutations. JAMA Ophthalmol 2013; 131:1016-25. [PMID: 23681342 DOI: 10.1001/jamaophthalmol.2013.120] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
IMPORTANCE For patients with X-linked retinitis pigmentosa and clinicians alike, phenotypic variability can be challenging because it complicates counseling regarding patients' likely visual prognosis. OBJECTIVE To evaluate the clinical findings from patients with X-linked retinitis pigmentosa with 13 distinct RPGR mutations and assess for phenotypic concordance or variability. DESIGN Retrospective medical record review of data collected from 1985 to 2011. SETTING Kellogg Eye Center, University of Michigan. PATIENTS A total of 42 patients with X-linked retinitis pigmentosa with mutations in RPGR. Age at first visit ranged from 4 to 53 years, with follow-up ranging from 1 to 11 visits (median follow-up time, 5.5 years; range, 1.4-32.7 years, for 23 patients with >1 visit). MAIN OUTCOMES AND MEASURES Clinical data assessed for concordance included visual acuity (VA), Goldmann visual fields (GVFs), and full-field electroretinography (ERG). Electroretinography phenotype (cone-rod vs rod-cone dysfunction) was defined by the extent of photopic vs scotopic abnormality. Qualitative GVF phenotype was determined by the GVF pattern, where central or peripheral loss suggested cone or rod dysfunction, respectively. Goldmann visual fields were also quantified and compared among patients. RESULTS Each mutation was detected in 2 or more related or unrelated patients. Five mutations in 11 patients displayed strong concordance of VA, while 4 mutations in 16 patients revealed moderate concordance of VA. A definitive cone-rod or rod-cone ERG pattern consistent among patients was found in 6 of 13 mutations (46.2%); the remaining mutations were characterized by patients demonstrating both phenotypes or who had limited data or nonrecordable ERG values. Concordant GVF phenotypes (7 rod-cone pattern vs 4 cone-rod pattern) were seen in 11 of 13 mutations (84.6%). All 6 mutations displaying a constant ERG pattern within the mutation group revealed a GVF phenotype consistent with the ERG findings. CONCLUSIONS AND RELEVANCE While VA and ERG phenotypes are concordant in only some patients carrying identical mutations, assessment of GVF phenotypes revealed stronger phenotypic conservation. Phenotypic concordance is important for establishing proper counseling of patients diagnosed as having X-linked retinitis pigmentosa, as well as for establishing accurate patient selection and efficacy monitoring in therapeutic trials.
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Affiliation(s)
- Sarwar Zahid
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor, MI 48105, USA
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Photoreceptor sensory cilia and ciliopathies: focus on CEP290, RPGR and their interacting proteins. Cilia 2012; 1:22. [PMID: 23351659 PMCID: PMC3563624 DOI: 10.1186/2046-2530-1-22] [Citation(s) in RCA: 110] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2012] [Accepted: 09/19/2012] [Indexed: 02/08/2023] Open
Abstract
Ciliopathies encompass a broad array of clinical findings associated with genetic defects in biogenesis and/or function of the primary cilium, a ubiquitous organelle involved in the transduction of diverse biological signals. Degeneration or dysfunction of retinal photoreceptors is frequently observed in diverse ciliopathies. The sensory cilium in a photoreceptor elaborates into unique outer segment discs that provide extensive surface area for maximal photon capture and efficient visual transduction. The daily renewal of approximately 10% of outer segments requires a precise control of ciliary transport. Here, we review the ciliopathies with associated retinal degeneration, describe the distinctive structure of the photoreceptor cilium, and discuss mouse models that allow investigations into molecular mechanisms of cilia biogenesis and defects. We have specifically focused on two ciliary proteins - CEP290 and RPGR - that underlie photoreceptor degeneration and syndromic ciliopathies. Mouse models of CEP290 and RPGR disease, and of their multiple interacting partners, have helped unravel new functional insights into cell type-specific phenotypic defects in distinct ciliary proteins. Elucidation of multifaceted ciliary functions and associated protein complexes will require concerted efforts to assimilate diverse datasets from in vivo and in vitro studies. We therefore discuss a possible framework for investigating genetic networks associated with photoreceptor cilia biogenesis and pathology.
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Anand M, Khanna H. Ciliary transition zone (TZ) proteins RPGR and CEP290: role in photoreceptor cilia and degenerative diseases. Expert Opin Ther Targets 2012; 16:541-51. [PMID: 22563985 DOI: 10.1517/14728222.2012.680956] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
INTRODUCTION Primary cilia are microtubule-based extensions of the plasma membrane in nearly all cell types. In vertebrate photoreceptors, the sensory cilium develops as outer segment (OS) that contains the photopigment rhodopsin and other proteins necessary for phototransduction. The distinct composition of proteins and lipids in the OS membrane is maintained by the selective barrier located at the border between the basal body and the ciliary compartment, called the transition zone (TZ). AREAS COVERED In this review, we will discuss the identification and function of two ciliary TZ proteins, RPGR (retinitis pigmentosa GTPase regulator) and CEP290. Mutations in these proteins account for a majority of retinopathies due to ciliary dysfunction. We will also discuss the potential of such information in designing therapeutic approaches to treat cilia-dependent photoreceptor degenerative diseases. EXPERT OPINION RPGR and CEP290 perform overlapping yet distinct functions in regulating trafficking of cargo via the TZ of photoreceptors. While RPGR modulates the trafficking by acting as a GEF for the small GTPase RAB8A, CEP290 may be involved in maintaining the polarized distribution of proteins in the OS by modulating intracellular levels of selected proteins involved in inhibiting OS formation.
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Affiliation(s)
- Manisha Anand
- University of Massachusetts Medical School, Department of Ophthalmology, 381 Plantation Street, Biotech 5, Suite 250, Worcester, MA 01605, USA
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Thompson DA, Khan NW, Othman MI, Chang B, Jia L, Grahek G, Wu Z, Hiriyanna S, Nellissery J, Li T, Khanna H, Colosi P, Swaroop A, Heckenlively JR. Rd9 is a naturally occurring mouse model of a common form of retinitis pigmentosa caused by mutations in RPGR-ORF15. PLoS One 2012; 7:e35865. [PMID: 22563472 PMCID: PMC3341386 DOI: 10.1371/journal.pone.0035865] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2012] [Accepted: 03/27/2012] [Indexed: 11/18/2022] Open
Abstract
Animal models of human disease are an invaluable component of studies aimed at understanding disease pathogenesis and therapeutic possibilities. Mutations in the gene encoding retinitis pigmentosa GTPase regulator (RPGR) are the most common cause of X-linked retinitis pigmentosa (XLRP) and are estimated to cause 20% of all retinal dystrophy cases. A majority of RPGR mutations are present in ORF15, the purine-rich terminal exon of the predominant splice-variant expressed in retina. Here we describe the genetic and phenotypic characterization of the retinal degeneration 9 (Rd9) strain of mice, a naturally occurring animal model of XLRP. Rd9 mice were found to carry a 32-base-pair duplication within ORF15 that causes a shift in the reading frame that introduces a premature-stop codon. Rpgr ORF15 transcripts, but not protein, were detected in retinas from Rd9/Y male mice that exhibited retinal pathology, including pigment loss and slowly progressing decrease in outer nuclear layer thickness. The levels of rhodopsin and transducin in rod outer segments were also decreased, and M-cone opsin appeared mislocalized within cone photoreceptors. In addition, electroretinogram (ERG) a- and b-wave amplitudes of both Rd9/Y male and Rd9/Rd9 female mice showed moderate gradual reduction that continued to 24 months of age. The presence of multiple retinal features that correlate with findings in individuals with XLRP identifies Rd9 as a valuable model for use in gaining insight into ORF15-associated disease progression and pathogenesis, as well as accelerating the development and testing of therapeutic strategies for this common form of retinal dystrophy.
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Affiliation(s)
- Debra A. Thompson
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- Department of Biological Chemistry, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Naheed W. Khan
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Mohammad I. Othman
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Bo Chang
- Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Lin Jia
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Garrett Grahek
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
| | - Zhijian Wu
- Neurobiology-Neurodegeneration & Repair laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Suja Hiriyanna
- Neurobiology-Neurodegeneration & Repair laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Jacob Nellissery
- Neurobiology-Neurodegeneration & Repair laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Tiansen Li
- Neurobiology-Neurodegeneration & Repair laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Hemant Khanna
- Department of Ophthalmology, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Peter Colosi
- Neurobiology-Neurodegeneration & Repair laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Anand Swaroop
- Neurobiology-Neurodegeneration & Repair laboratory, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States of America
- * E-mail: (AS); (JRH)
| | - John R. Heckenlively
- Department of Ophthalmology and Visual Sciences, University of Michigan Medical School, Ann Arbor, Michigan, United States of America
- * E-mail: (AS); (JRH)
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Gene therapy rescues photoreceptor blindness in dogs and paves the way for treating human X-linked retinitis pigmentosa. Proc Natl Acad Sci U S A 2012; 109:2132-7. [PMID: 22308428 DOI: 10.1073/pnas.1118847109] [Citation(s) in RCA: 204] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Hereditary retinal blindness is caused by mutations in genes expressed in photoreceptors or retinal pigment epithelium. Gene therapy in mouse and dog models of a primary retinal pigment epithelium disease has already been translated to human clinical trials with encouraging results. Treatment for common primary photoreceptor blindness, however, has not yet moved from proof of concept to the clinic. We evaluated gene augmentation therapy in two blinding canine photoreceptor diseases that model the common X-linked form of retinitis pigmentosa caused by mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene, which encodes a photoreceptor ciliary protein, and provide evidence that the therapy is effective. After subretinal injections of adeno-associated virus-2/5-vectored human RPGR with human IRBP or GRK1 promoters, in vivo imaging showed preserved photoreceptor nuclei and inner/outer segments that were limited to treated areas. Both rod and cone photoreceptor function were greater in treated (three of four) than in control eyes. Histopathology indicated normal photoreceptor structure and reversal of opsin mislocalization in treated areas expressing human RPGR protein in rods and cones. Postreceptoral remodeling was also corrected: there was reversal of bipolar cell dendrite retraction evident with bipolar cell markers and preservation of outer plexiform layer thickness. Efficacy of gene therapy in these large animal models of X-linked retinitis pigmentosa provides a path for translation to human treatment.
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Thiadens AAHJ, Soerjoesing GG, Florijn RJ, Tjiam AG, den Hollander AI, van den Born LI, Riemslag FC, Bergen AAB, Klaver CCW. Clinical course of cone dystrophy caused by mutations in the RPGR gene. Graefes Arch Clin Exp Ophthalmol 2011; 249:1527-35. [PMID: 21866333 PMCID: PMC3178018 DOI: 10.1007/s00417-011-1789-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2011] [Revised: 07/19/2011] [Accepted: 07/28/2011] [Indexed: 11/12/2022] Open
Abstract
Background Mutations in the RPGR gene predominantly cause rod photoreceptor disorders with a large variability in clinical course. In this report, we describe two families with mutations in this gene and cone involvement. Methods We investigated an X-linked cone dystrophy family (1) with 25 affected males, 25 female carriers, and 21 non-carriers, as well as a small family (2) with one affected and one unaffected male. The RPGR gene was analyzed by direct sequencing. All medical records were evaluated, and all available data on visual acuity, color vision testing, ophthalmoscopy, fundus photography, fundus autofluorescence, Goldmann perimetry, SD-OCT, dark adaptation, and full-field electroretinography (ERG) were registered. Cumulative risks of visual loss were studied with Kaplan–Meier product-limit survival analysis. Results Both families had a frameshift mutation in ORF15 of the RPGR gene; family 1 had p.Ser1107ValfsX4, and family 2 had p.His1100GlnfsX10. Mean follow up was 13 years (SD 10). Virtually all affected males showed reduced photopic and normal scotopic responses on ERG. Fifty percent of the patients had a visual acuity of <0.5 at age 35 years (SE 2.2), and 75% of the patients was legally blind at age 60 years (SE 2.3). Female carriers showed no signs of ocular involvement. Conclusions This report describes the clinical course and visual prognosis in two families with cone dystrophy due to RPGR mutations in the 3’ terminal region of ORF15. Remarkable features were the consistent, late-onset phenotype, the severe visual outcome, and the non-expression in female carriers. Expression of RPGR mutations in this particular region appears to be relatively homogeneous and predisposed to cones.
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Affiliation(s)
- Alberta A H J Thiadens
- Department of Ophthalmology, Erasmus Medical Center, PO Box 2040, 3000, CA, Rotterdam, The Netherlands
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Allelic heterogeneity and genetic modifier loci contribute to clinical variation in males with X-linked retinitis pigmentosa due to RPGR mutations. PLoS One 2011; 6:e23021. [PMID: 21857984 PMCID: PMC3155520 DOI: 10.1371/journal.pone.0023021] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Accepted: 07/07/2011] [Indexed: 11/23/2022] Open
Abstract
Mutations in RPGR account for over 70% of X-linked retinitis pigmentosa (XlRP), characterized by retinal degeneration and eventual blindness. The clinical consequences of RPGR mutations are highly varied, even among individuals with the same mutation: males demonstrate a wide range of clinical severity, and female carriers may or may not be affected. This study describes the phenotypic diversity in a cohort of 98 affected males from 56 families with RPGR mutations, and demonstrates the contribution of genetic factors (i.e., allelic heterogeneity and genetic modifiers) to this diversity. Patients were categorized as grade 1 (mild), 2 (moderate) or 3 (severe) according to specific clinical criteria. Patient DNAs were genotyped for coding SNPs in 4 candidate modifier genes with products known to interact with RPGR protein: RPGRIP1, RPGRIP1L, CEP290, and IQCB1. Family-based association testing was performed using PLINK. A wide range of clinical severity was observed both between and within families. Patients with mutations in exons 1–14 were more severely affected than those with ORF15 mutations, and patients with predicted null alleles were more severely affected than those predicted to make RPGR protein. Two SNPs showed association with severe disease: the minor allele (N) of I393N in IQCB1 (p = 0.044) and the common allele (R) of R744Q in RPGRIP1L (p = 0.049). These data demonstrate that allelic heterogeneity contributes to phenotypic diversity in XlRP and suggest that this may depend on the presence or absence of RPGR protein. In addition, common variants in 2 proteins known to interact with RPGR are associated with severe disease in this cohort.
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Gan DK, He CL, Shu HR, Hoffman MR, Jin ZB. Novel RPGR-ORF15 mutations in X-linked retinitis pigmentosa patients. Neurosci Lett 2011; 500:16-9. [PMID: 21683121 DOI: 10.1016/j.neulet.2011.05.234] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2011] [Revised: 05/30/2011] [Accepted: 05/30/2011] [Indexed: 01/13/2023]
Abstract
X-linked retinitis pigmentosa (XLRP) is the most severe type of retinitis pigmentosa (RP), with patients consistently showing early onset and rapid deterioration. Obtaining a genetic diagnosis for a family with XLRP is important for counseling purposes. In this study, we aimed to identify disease-causing mutations in two unrelated XLRP families. Genetic analysis was performed on two unrelated XLRP families. Genomic DNA was extracted from peripheral blood or amniotic fluid samples. The coding regions and intron/exon boundaries of the Retinitis Pigmentosa GTPase Regulator (RPGR) and RP2 genes were amplified by PCR and then sequenced directly. A clinically unaffected pregnant female and the four month old fetus were found to have a hemizygous 2 base pair deletion (g.ORF15+484_485delAA) in the exon ORF15 of RPGR gene. In another XLRP family, a nonsense mutation (g.ORF15+810G>T) was identified. Neither mutation has been reported previously. Both are predicted to cause premature termination of the protein. In conclusion, we identified a micro-deletion through prenatal genetic diagnosis and another novel nonsense mutation in RPGR-ORF15. Identifying a disease-causing mutation facilitated early diagnosis and genetic counseling for the patients. Discovery of novel mutations also broadens knowledge of XLRP and the spectrum of its pathogenic genotypes.
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Affiliation(s)
- De-Kang Gan
- Department of Ophthalmology, The Eye & ENT Hospital of Fudan University, Shanghai 200031, China
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Hu Q, Nelson WJ. Ciliary diffusion barrier: the gatekeeper for the primary cilium compartment. Cytoskeleton (Hoboken) 2011; 68:313-24. [PMID: 21634025 DOI: 10.1002/cm.20514] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2011] [Accepted: 05/04/2011] [Indexed: 11/08/2022]
Abstract
The primary cilium is a cellular antenna that detects and transmits chemical and mechanical cues in the environment through receptors and downstream signal proteins enriched along the ciliary membrane. While it is known that ciliary membrane proteins enter the cilium by way of vesicular and intraflagellar transport, less is known about how ciliary membrane proteins are retained in, and how apical membrane proteins are excluded from the cilium. Here, we review evidence for a membrane diffusion barrier at the base of the primary cilium, and highlight the recent finding of a septin cytoskeleton diffusion barrier. We also discuss candidate ciliopathy genes that may be involved in formation of the barrier, and the role of a diffusion barrier as a common mechanism for compartmentalizing membranes and lipid domains.
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Affiliation(s)
- Qicong Hu
- Department of Biology, Stanford University, Stanford, California 94305., USA
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Murga-Zamalloa CA, Desai NJ, Hildebrandt F, Khanna H. Interaction of ciliary disease protein retinitis pigmentosa GTPase regulator with nephronophthisis-associated proteins in mammalian retinas. Mol Vis 2010; 16:1373-81. [PMID: 20664800 PMCID: PMC2905641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2010] [Accepted: 07/13/2010] [Indexed: 11/04/2022] Open
Abstract
PURPOSE Retinitis pigmentosa GTPase regulator (RPGR) is a cilia-centrosomal protein that frequently mutates in X-linked retinal degeneration and associated disorders. RPGR interacts with multiple ciliary proteins in the retina. Perturbations in the assembly of RPGR complexes are associated with retinal degeneration. This study was undertaken to delineate the composition and dissection of RPGR complexes in mammalian retinas. METHODS Immunoprecipitation of RPGR from ciliary fraction of bovine retina was performed, followed by mass spectrometry analysis. The glutathione S-transferase pull-down assay was performed to validate the interaction. Immunodepletion experiments were performed to dissect the partitioning of RPGR in different protein complexes in mammalian retinas. RESULTS We found that RPGR associates with a ciliary protein nephrocystin-4 (nephroretinin; NPHP4) that is mutated in nephronophthisis (NPH) and RP (Senior-Løken syndrome). This association is abolished in the Rpgr-knockout mouse retina. The RCC1-like domain of RPGR interacts with the N-terminal 316 amino acids of NPHP4. In the retina, RPGR also associates with NPHP1, an NPHP4-interacting protein; RPGR interacts directly with amino acids 243-586 of NPHP1. We further show that, in the retina, RPGR associates with and is partitioned in at least two different complexes with NPHP-associated proteins, (i) NPHP1, NPHP2, and NPHP5, and (ii) NPHP4, NPHP6, and NPHP8. CONCLUSIONS RPGR may regulate some complexes with NPHP proteins in the mammalian retina. The disruption of these complexes may contribute to the pathogenesis of retinal degeneration in X-linked RP and associated ciliary diseases.
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Affiliation(s)
- Carlos A. Murga-Zamalloa
- Department of Ophthalmology and Visual Sciences and Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI
| | - Nimit J. Desai
- Department of Ophthalmology and Visual Sciences and Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI
| | | | - Hemant Khanna
- Department of Ophthalmology and Visual Sciences and Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI
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Murga-Zamalloa CA, Atkins SJ, Peranen J, Swaroop A, Khanna H. Interaction of retinitis pigmentosa GTPase regulator (RPGR) with RAB8A GTPase: implications for cilia dysfunction and photoreceptor degeneration. Hum Mol Genet 2010; 19:3591-8. [PMID: 20631154 PMCID: PMC2928130 DOI: 10.1093/hmg/ddq275] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Defects in biogenesis or function(s) of primary cilia are associated with numerous inherited disorders (called ciliopathies) that may include retinal degeneration phenotype. The cilia-expressed gene RPGR (retinitis pigmentosa GTPase regulator) is mutated in patients with X-linked retinitis pigmentosa (XLRP) and encodes multiple protein isoforms with a common N-terminal domain homologous to regulator of chromosome condensation 1 (RCC1), a guanine nucleotide exchange factor (GEF) for Ran GTPase. RPGR interacts with several ciliopathy proteins, such as RPGRIP1L and CEP290; however, its physiological role in cilia-associated functions has not been delineated. Here, we report that RPGR interacts with the small GTPase RAB8A, which participates in cilia biogenesis and maintenance. We show that RPGR primarily associates with the GDP-bound form of RAB8A and stimulates GDP/GTP nucleotide exchange. Disease-causing mutations in RPGR diminish its interaction with RAB8A and reduce the GEF activity. Depletion of RPGR in hTERT-RPE1 cells interferes with ciliary localization of RAB8A and results in shorter primary cilia. Our data suggest that RPGR modulates intracellular localization and function of RAB8A. We propose that perturbation of RPGR–RAB8A interaction, at least in part, underlies the pathogenesis of photoreceptor degeneration in XLRP caused by RPGR mutations.
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Affiliation(s)
- Carlos A Murga-Zamalloa
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
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Murga-Zamalloa CA, Swaroop A, Khanna H. RPGR-containing protein complexes in syndromic and non-syndromic retinal degeneration due to ciliary dysfunction. J Genet 2010; 88:399-407. [PMID: 20090203 DOI: 10.1007/s12041-009-0061-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Dysfunction of primary cilia due to mutations in cilia-centrosomal proteins is associated with pleiotropic disorders. The primary (or sensory) cilium of photoreceptors mediates polarized trafficking of proteins for efficient phototransduction. Retinitis pigmentosa GTPase regulator (RPGR) is a cilia-centrosomal protein mutated in >70% of X-linked RP cases and 10%-20% of simplex RP males. Accumulating evidence indicates that RPGR may facilitate the orchestration of multiple ciliary protein complexes. Disruption of these complexes due to mutations in component proteins is an underlying cause of associated photoreceptor degeneration. Here, we highlight the recent developments in understanding the mechanism of cilia-dependent photoreceptor degeneration due to mutations in RPGR and PGR-interacting proteins in severe genetic diseases, including retinitis pigmentosa, Leber congenital amaurosis (LCA), Joubert syndrome, and Senior-Loken syndrome, and explore the physiological relevance of photoreceptor ciliary protein complexes.
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Affiliation(s)
- Carlos A Murga-Zamalloa
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
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Ghosh AK, Murga-Zamalloa CA, Chan L, Hitchcock PF, Swaroop A, Khanna H. Human retinopathy-associated ciliary protein retinitis pigmentosa GTPase regulator mediates cilia-dependent vertebrate development. Hum Mol Genet 2010; 19:90-8. [PMID: 19815619 DOI: 10.1093/hmg/ddp469] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Dysfunction of primary cilia is associated with tissue-specific or syndromic disorders. RPGR is a ciliary protein, mutations in which can lead to retinitis pigmentosa (RP), cone-rod degeneration, respiratory infections and hearing disorders. Though RPGR is implicated in ciliary transport, the pathogenicity of RPGR mutations and the mechanism of underlying phenotypic heterogeneity are still unclear. Here we have utilized genetic rescue studies in zebrafish to elucidate the effect of human disease-associated mutations on its function. We show that rpgr is expressed predominantly in the retina, brain and gut of zebrafish. In the retina, RPGR primarily localizes to the sensory cilium of photoreceptors. Antisense morpholino (MO)-mediated knockdown of rpgr function in zebrafish results in reduced length of Kupffer's vesicle (KV) cilia and is associated with ciliary anomalies including shortened body-axis, kinked tail, hydrocephaly and edema but does not affect retinal development. These phenotypes can be rescued by wild-type (WT) human RPGR. Several of the RPGR mutants can also reverse the MO-induced phenotype, suggesting their potential hypomorphic function. Notably, selected RPGR mutations observed in XLRP (T99N, E589X) or syndromic RP (T124fs, K190fs and L280fs) do not completely rescue the rpgr-MO phenotype, indicating a more deleterious effect of the mutation on the function of RPGR. We propose that RPGR is involved in cilia-dependent cascades during development in zebrafish. Our studies provide evidence for a heterogenic effect of the disease-causing mutations on the function of RPGR.
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Affiliation(s)
- Amiya K Ghosh
- Department of Ophthalmology and Visual Sciences, University of Michigan, Ann Arbor, MI 48105, USA
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Murga-Zamalloa C, Swaroop A, Khanna H. Multiprotein complexes of Retinitis Pigmentosa GTPase regulator (RPGR), a ciliary protein mutated in X-linked Retinitis Pigmentosa (XLRP). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 664:105-14. [PMID: 20238008 DOI: 10.1007/978-1-4419-1399-9_13] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Mutations in Retinitis Pigmentosa GTPase Regulator (RPGR) are a frequent cause of X-linked Retinitis Pigmentosa (XLRP). The RPGR gene undergoes extensive alternative splicing and encodes for distinct protein isoforms in the retina. Extensive studies using isoform-specific antibodies and mouse mutants have revealed that RPGR predominantly localizes to the transition zone to primary cilia and associates with selected ciliary and microtubule-associated assemblies in photoreceptors. In this chapter, we have summarized recent advances on understanding the role of RPGR in photoreceptor protein trafficking. We also provide new evidence that suggests the existence of discrete RPGR multiprotein complexes in photoreceptors. Piecing together the RPGR-interactome in different subcellular compartments should provide critical insights into the role of alternative RPGR isoforms in associated orphan and syndromic retinal degenerative diseases.
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Affiliation(s)
- Carlos Murga-Zamalloa
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Ann Arbor, MI 48105, USA
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Veltel S, Wittinghofer A. RPGR and RP2: targets for the treatment of X-linked retinitis pigmentosa? Expert Opin Ther Targets 2009; 13:1239-51. [PMID: 19702441 DOI: 10.1517/14728220903225016] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Retinitis pigmentosa is the most important hereditary eye disease and there is currently no cure available. Although mutations were found in more than 40 genes in patients with retinitis pigmentosa, only two genes have thus far been found to be responsible for one of the most severe forms of the disease, X-linked retinitis pigmentosa. In this review, we highlight the current knowledge about the two gene products RPGR and RP2 and try to link genetic data from patients with functional data on the corresponding proteins. Based on the fact that recent gene therapeutic approaches for eye diseases are at a very promising stage, we discuss the potential of RPGR and RP2 as drug targets to treat retinitis pigmentosa.
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Affiliation(s)
- Stefan Veltel
- Max-Planck-Institut für molekulare Physiologie, Abteilung Strukturelle Biologie, Otto Hahn-Street 11, 44227 Dortmund, Germany
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A common allele in RPGRIP1L is a modifier of retinal degeneration in ciliopathies. Nat Genet 2009; 41:739-45. [PMID: 19430481 PMCID: PMC2783476 DOI: 10.1038/ng.366] [Citation(s) in RCA: 230] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Accepted: 02/26/2009] [Indexed: 11/08/2022]
Abstract
Despite rapid advances in the identification of genes involved in disease, the predictive power of the genotype remains limited, in part owing to poorly understood effects of second-site modifiers. Here we demonstrate that a polymorphic coding variant of RPGRIP1L (retinitis pigmentosa GTPase regulator-interacting protein-1 like), a ciliary gene mutated in Meckel-Gruber (MKS) and Joubert (JBTS) syndromes, is associated with the development of retinal degeneration in individuals with ciliopathies caused by mutations in other genes. As part of our resequencing efforts of the ciliary proteome, we identified several putative loss-of-function RPGRIP1L mutations, including one common variant, A229T. Multiple genetic lines of evidence showed this allele to be associated with photoreceptor loss in ciliopathies. Moreover, we show that RPGRIP1L interacts biochemically with RPGR, loss of which causes retinal degeneration, and that the Thr229-encoded protein significantly compromises this interaction. Our data represent an example of modification of a discrete phenotype of syndromic disease and highlight the importance of a multifaceted approach for the discovery of modifier alleles of intermediate frequency and effect.
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Brunner S, Colman D, Travis AJ, Luhmann UF, Shi W, Feil S, Imsand C, Nelson J, Grimm C, Rülicke T, Fundele R, Neidhardt J, Berger W. Overexpression of RPGR Leads to Male Infertility in Mice Due to Defects in Flagellar Assembly1. Biol Reprod 2008; 79:608-17. [DOI: 10.1095/biolreprod.107.067454] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
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Garbarini N, Delpire E. The RCC1 domain of protein associated with Myc (PAM) interacts with and regulates KCC2. Cell Physiol Biochem 2008; 22:31-44. [PMID: 18769030 PMCID: PMC2535904 DOI: 10.1159/000149781] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/17/2008] [Indexed: 12/16/2022] Open
Abstract
GABAergic and glycinergic function is dependent on neuronal intracellular chloride. The neuron-specific electroneutral potassium (K(+)) and chloride (Cl(-)) cotransporter (KCC2), is a key regulator of neuronal Cl(-), yet little is known about KCC2 regulation. Using yeast two-hybrid, we identified Protein Associated with Myc (PAM) as a binding partner of KCC2. The RCC1 (Regulator of Chromatin Condensation) domain of PAM binds to the carboxyl terminus of KCC2, as demonstrated through yeast two-hybrid and GST-pull-down assays. RCC1/PAM and full-length KCC2 coimmunoprecipitate following heterologous co-expression in HEK293 cells. Additionally, (86)Rb/K(+) uptake assays in this model system show that RCC1/PAM causes increased KCC2-mediated flux. After narrowing down RCC1/PAM binding to a 20 amino acid region on the KCC2 carboxyl terminus, we created a point mutant in this region to eliminate interaction between the KCC2 carboxyl terminus and RCC1/PAM. This same mutation abolishes N-ethylmaleimide activation of KCC2, suggesting that PAM plays a role in modulating KCC2 function.
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Affiliation(s)
- Nicole Garbarini
- Neuroscience Graduate Program and Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, TN, USA
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Spatuzza C, Schiavone M, Di Salle E, Janda E, Sardiello M, Fiume G, Fierro O, Simonetta M, Argiriou N, Faraonio R, Capparelli R, Quinto I, Scala G. Physical and functional characterization of the genetic locus of IBtk, an inhibitor of Bruton's tyrosine kinase: evidence for three protein isoforms of IBtk. Nucleic Acids Res 2008; 36:4402-16. [PMID: 18596081 PMCID: PMC2490745 DOI: 10.1093/nar/gkn413] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Bruton's tyrosine kinase (Btk) is required for B-cell development. Btk deficiency causes X-linked agammaglobulinemia (XLA) in humans and X-linked immunodeficiency (Xid) in mice. Btk lacks a negative regulatory domain and may rely on cytoplasmic proteins to regulate its activity. Consistently, we identified an inhibitor of Btk, IBtk, which binds to the PH domain of Btk and down-regulates the Btk kinase activity. IBtk is an evolutionary conserved protein encoded by a single genomic sequence at 6q14.1 cytogenetic location, a region of recurrent chromosomal aberrations in lymphoproliferative disorders; however, the physical and functional organization of IBTK is unknown. Here, we report that the human IBTK locus includes three distinct mRNAs arising from complete intron splicing, an additional polyadenylation signal and a second transcription start site that utilizes a specific ATG for protein translation. By northern blot, 5′RACE and 3′RACE we identified three IBTKα, IBTKβ and IBTKγ mRNAs, whose transcription is driven by two distinct promoter regions; the corresponding IBtk proteins were detected in human cells and mouse tissues by specific antibodies. These results provide the first characterization of the human IBTK locus and may assist in understanding the in vivo function of IBtk.
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Affiliation(s)
- Carmen Spatuzza
- Department of Experimental and Clinical Medicine, University of Catanzaro Magna Graecia, 88100 Catanzaro, Italy
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