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Liu X, Han S, Liu F, Yu S, Qin Y, Li J, Jia D, Gao P, Chen X, Tang Z, Liu M, Huang Y. Retinal degeneration in rpgra mutant zebrafish. Front Cell Dev Biol 2023; 11:1169941. [PMID: 37351277 PMCID: PMC10282147 DOI: 10.3389/fcell.2023.1169941] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 05/24/2023] [Indexed: 06/24/2023] Open
Abstract
Introduction: Pathogenic mutations in RPGR ORF15, one of two major human RPGR isoforms, were responsible for most X-linked retinitis pigmentosa cases. Previous studies have shown that RPGR plays a critical role in ciliary protein transport. However, the precise mechanisms of disease triggered by RPGR ORF15 mutations have yet to be clearly defined. There are two homologous genes in zebrafish, rpgra and rpgrb. Zebrafish rpgra has a single transcript homologous to human RPGR ORF15; rpgrb has two major transcripts: rpgrb ex1-17 and rpgrb ORF15, similar to human RPGR ex1-19 and RPGR ORF15, respectively. rpgrb knockdown in zebrafish resulted in both abnormal development and increased cell death in the dysplastic retina. However, the impact of knocking down rpgra in zebrafish remains undetermined. Here, we constructed a rpgra mutant zebrafish model to investigate the retina defect and related molecular mechanism. Methods: we utilized transcription activator-like effector nuclease (TALEN) to generate a rpgra mutant zebrafish. Western blot was used to determine protein expression. RT-PCR was used to quantify gene transcription levels. The visual function of embryonic zebrafish was detected by electroretinography. Immunohistochemistry was used to observe the pathological changes in the retina of mutant zebrafish and transmission electron microscope was employed to view subcellular structure of photoreceptor cells. Results: A homozygous rpgra mutant zebrafish with c.1675_1678delins21 mutation was successfully constructed. Despite the normal morphological development of the retina at 5 days post-fertilization, visual dysfunction was observed in the mutant zebrafish. Further histological and immunofluorescence assays indicated that rpgra mutant zebrafish retina photoreceptors progressively began to degenerate at 3-6 months. Additionally, the mislocalization of cone outer segment proteins (Opn1lw and Gnb3) and the accumulation of vacuole-like structures around the connecting cilium below the OSs were observed in mutant zebrafish. Furthermore, Rab8a, a key regulator of opsin-carrier vesicle trafficking, exhibited decreased expression and evident mislocalization in mutant zebrafish. Discussion: This study generated a novel rpgra mutant zebrafish model, which showed retinal degeneration. our data suggested Rpgra is necessary for the ciliary transport of cone-associated proteins, and further investigation is required to determine its function in rods. The rpgra mutant zebrafish constructed in this study may help us gain a better understanding of the molecular mechanism of retinal degeneration caused by RPGR ORF15 mutation and find some useful treatment in the future.
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Affiliation(s)
- Xiliang Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
- Sansure Biotech Inc., Changsha, Hunan, China
| | - Shanshan Han
- Medical College, China Three Gorges University, Yichang, China
- The Institute of Infection and Inflammation, China Three Gorges University, Yichang, Hubei, China
| | - Fei Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Innovation Academy for Seed Design, Chinese Academy of Science, Wuhan, Hubei, China
| | - Shanshan Yu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
- Institute of Visual Neuroscience and Stem Cell Engineering, College of Life Sciences and Health, Wuhan University of Science and Technology, Wuhan, Hubei, China
| | - Yayun Qin
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
- Maternal and Child Health Hospital of Hubei Province, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Jingzhen Li
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Danna Jia
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Pan Gao
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Xiang Chen
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Zhaohui Tang
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Mugen Liu
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
| | - Yuwen Huang
- Key Laboratory of Molecular Biophysics of Ministry of Education, Department of Genetics and Developmental Biology, College of Life Science and Technology, Huazhong University of Science and Technology, Wuhan, Hubei, China
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Martinez-Fernandez de la Camara C, Cehajic-Kapetanovic J, MacLaren RE. Emerging gene therapy products for RPGR-associated X-linked retinitis pigmentosa. Expert Opin Emerg Drugs 2022; 27:431-443. [PMID: 36562395 DOI: 10.1080/14728214.2022.2152003] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2021] [Accepted: 11/22/2022] [Indexed: 12/24/2022]
Abstract
INTRODUCTION Mutations in the RPGR gene are responsible for one of the most prevalent and severe types of retinitis pigmentosa. Gene therapy has shown great promise to treat inherited retinal diseases, and currently, four RPGR gene therapy vectors are being evaluated in clinical trials. AREAS COVERED This manuscript reviews the gene therapy products that are in development for X-linked retinitis pigmentosa caused by mutations in RPGR, and the challenges that scientists and clinicians have faced. EXPERT OPINION The development of a gene therapy product for RPGR-associated retinal degeneration has been a great challenge due to the incomplete understanding of the underlying genetics and mechanism of action of RPGR, and on the other hand, due to the instability of the RPGR gene. Three of the four gene therapy vectors currently in clinical trials include a codon-optimized version of the human RPGR sequence, and the other vector contains a shortened version of the human RPGR. To date, the only Phase I/II results published in a peer-reviewed journal demonstrate a good safety profile and an improvement in the visual field using a codon optimized version of RPGRORF15.
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Affiliation(s)
- Cristina Martinez-Fernandez de la Camara
- Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, John Radcliffe Hospital, Level 5 & 6, West Wing, Headley Way, OX3 9DU, Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Trust, John Radcliffe Hospital, West Wing, Headley Way, OX3 9DU, Oxford, UK
| | - Jasmina Cehajic-Kapetanovic
- Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, John Radcliffe Hospital, Level 5 & 6, West Wing, Headley Way, OX3 9DU, Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Trust, John Radcliffe Hospital, West Wing, Headley Way, OX3 9DU, Oxford, UK
| | - Robert E MacLaren
- Nuffield Laboratory of Ophthalmology, Department of Clinical Neurosciences, John Radcliffe Hospital, Level 5 & 6, West Wing, Headley Way, OX3 9DU, Oxford, UK
- Oxford Eye Hospital, Oxford University Hospitals NHS Trust, John Radcliffe Hospital, West Wing, Headley Way, OX3 9DU, Oxford, UK
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Yang J, Zhou L, Ouyang J, Xiao X, Sun W, Li S, Zhang Q. Genotype-Phenotype Analysis of RPGR Variations: Reporting of 62 Chinese Families and a Literature Review. Front Genet 2021; 12:600210. [PMID: 34745198 PMCID: PMC8565807 DOI: 10.3389/fgene.2021.600210] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2020] [Accepted: 04/27/2021] [Indexed: 02/05/2023] Open
Abstract
Purpose RPGR is the most common cause of X-linked retinitis pigmentosa (RP), of which female carriers are also frequently affected. The aim of the current study was to explore the RPGR variation spectrum and associated phenotype based on the data from our lab and previous studies. Methods Variants in RPGR were selected from exome sequencing data of 7,092 probands with different eye conditions. The probands and their available family members underwent comprehensive ocular examinations. Similar data were collected from previous reports through searches in PubMed, Web of Science, and Google Scholar. Systematic analyses of genotypes, phenotypes and their correlations were performed. Results A total of 46 likely pathogenic variants, including nine missense and one in-frame variants in RCC1-like domain and 36 truncation variants, in RPGR were detected in 62 unrelated families in our in-house cohort. In addition, a total of 585 variants, including 491 (83.9%) truncation variants, were identified from the literature. Systematic analysis of variants from our in-house dataset, literature, and gnomAD suggested that most of the pathogenic variants of RPGR were truncation variants while pathogenic missense and in-frame variants were enriched in the RCC1-like domain. Phenotypic variations were present between males and female carriers, including more severe refractive error but better best corrected visual acuity (BCVA) in female carriers than those in males. The male patients showed a significant reduction of BCVA with increase of age and males with exon1-14 variants presented a better BCVA than those with ORF15 variants. For female carriers, the BCVA also showed significant reduction with increase of age, but BCVA in females with exon1-14 variants was not significant difference compared with those with ORF15 variants. Conclusion Most pathogenic variants of RPGR are truncations. Missense and in-frame variants located outside of the RCC1-like domain might be benign and the pathogenicity criteria for these variants should be considered with greater caution. The BCVA and refractive error are different between males and female carriers. Increase of age and location of variants in ORF15 contribute to the reduction of BCVA in males. These results are valuable for understanding genotypes and phenotypes of RPGR.
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Affiliation(s)
- Junxing Yang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Lin Zhou
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China.,Department of Ophthalmology, West China Hospital, Sichuan University, Chengdu, China
| | - Jiamin Ouyang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Xueshan Xiao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Wenmin Sun
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Shiqiang Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
| | - Qingjiong Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
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Cogné B, Latypova X, Senaratne LDS, Martin L, Koboldt DC, Kellaris G, Fievet L, Le Meur G, Caldari D, Debray D, Nizon M, Frengen E, Bowne SJ, Cadena EL, Daiger SP, Bujakowska KM, Pierce EA, Gorin M, Katsanis N, Bézieau S, Petersen-Jones SM, Occelli LM, Lyons LA, Legeai-Mallet L, Sullivan LS, Davis EE, Isidor B, Buckley RM, Aberdein D, Alves PC, Barsh GS, Bellone RR, Bergström TF, Boyko AR, Brockman JA, Casal ML, Castelhano MG, Distl O, Dodman NH, Ellinwood NM, Fogle JE, Forman OP, Garrick DJ, Ginns EI, Häggström J, Harvey RJ, Hasegawa D, Haase B, Helps CR, Hernandez I, Hytönen MK, Kaukonen M, Kaelin CB, Kosho T, Leclerc E, Lear TL, Leeb T, Li RH, Lohi H, Longeri M, Magnuson MA, Malik R, Mane SP, Munday JS, Murphy WJ, Pedersen NC, Rothschild MF, Rusbridge C, Shapiro B, Stern JA, Swanson WF, Terio KA, Todhunter RJ, Warren WC, Wilcox EA, Wildschutte JH, Yu Y. Mutations in the Kinesin-2 Motor KIF3B Cause an Autosomal-Dominant Ciliopathy. Am J Hum Genet 2020; 106:893-904. [PMID: 32386558 DOI: 10.1016/j.ajhg.2020.04.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 04/02/2020] [Indexed: 11/26/2022] Open
Abstract
Kinesin-2 enables ciliary assembly and maintenance as an anterograde intraflagellar transport (IFT) motor. Molecular motor activity is driven by a heterotrimeric complex comprised of KIF3A and KIF3B or KIF3C plus one non-motor subunit, KIFAP3. Using exome sequencing, we identified heterozygous KIF3B variants in two unrelated families with hallmark ciliopathy phenotypes. In the first family, the proband presents with hepatic fibrosis, retinitis pigmentosa, and postaxial polydactyly; he harbors a de novo c.748G>C (p.Glu250Gln) variant affecting the kinesin motor domain encoded by KIF3B. The second family is a six-generation pedigree affected predominantly by retinitis pigmentosa. Affected individuals carry a heterozygous c.1568T>C (p.Leu523Pro) KIF3B variant segregating in an autosomal-dominant pattern. We observed a significant increase in primary cilia length in vitro in the context of either of the two mutations while variant KIF3B proteins retained stability indistinguishable from wild type. Furthermore, we tested the effects of KIF3B mutant mRNA expression in the developing zebrafish retina. In the presence of either missense variant, rhodopsin was sequestered to the photoreceptor rod inner segment layer with a concomitant increase in photoreceptor cilia length. Notably, impaired rhodopsin trafficking is also characteristic of recessive KIF3B models as exemplified by an early-onset, autosomal-recessive, progressive retinal degeneration in Bengal cats; we identified a c.1000G>A (p.Ala334Thr) KIF3B variant by genome-wide association study and whole-genome sequencing. Together, our genetic, cell-based, and in vivo modeling data delineate an autosomal-dominant syndromic retinal ciliopathy in humans and suggest that multiple KIF3B pathomechanisms can impair kinesin-driven ciliary transport in the photoreceptor.
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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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Ropelewski P, Imanishi Y. Disrupted Plasma Membrane Protein Homeostasis in a Xenopus Laevis Model of Retinitis Pigmentosa. J Neurosci 2019; 39:5581-5593. [PMID: 31061086 PMCID: PMC6616295 DOI: 10.1523/jneurosci.3025-18.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 03/23/2019] [Accepted: 04/26/2019] [Indexed: 12/17/2022] Open
Abstract
Rhodopsin mislocalization is frequently observed in retinitis pigmentosa (RP) patients. For example, class I mutant rhodopsin is deficient in the VxPx trafficking signal, mislocalizes to the plasma membrane (PM) of rod photoreceptor inner segments (ISs), and causes autosomal dominant RP. Mislocalized rhodopsin causes photoreceptor degeneration in a manner independent of light-activation. In this manuscript, we took advantage of Xenopus laevis models of both sexes expressing wild-type human rhodopsin or its class I Q344ter mutant fused to Dendra2 fluorescent protein to characterize a novel light-independent mechanism of photoreceptor degeneration caused by mislocalized rhodopsin. We found that rhodopsin mislocalized to the PM is actively internalized and transported to lysosomes where it is degraded. This degradation process results in the downregulation of a crucial component of the photoreceptor IS PM: the sodium-potassium ATPase α-subunit (NKAα). The downregulation of NKAα is not because of decreased NKAα mRNA, but due to cotransport of mislocalized rhodopsin and NKAα to lysosomes or autophagolysosomes. In a separate set of experiments, we found that class I mutant rhodopsin, which causes NKAα downregulation, also causes shortening and loss of rod outer segments (OSs); the symptoms frequently observed in the early stages of human RP. Likewise, pharmacological inhibition of NKAα led to shortening and loss of rod OSs. These combined studies suggest that mislocalized rhodopsin leads to photoreceptor dysfunction through disruption of the PM protein homeostasis and compromised NKAα function. This study unveiled a novel role of lysosome-mediated degradation in causing inherited disorders manifested by mislocalization of ciliary receptors.SIGNIFICANCE STATEMENT Retinal ciliopathy is the most common form of inherited blinding disorder frequently manifesting rhodopsin mislocalization. Our understanding of the relationships between rhodopsin mislocalization and photoreceptor dysfunction/degeneration has been far from complete. This study uncovers a hitherto uncharacterized consequence of rhodopsin mislocalization: the activation of the lysosomal pathway, which negatively regulates the amount of the sodium-potassium ATPase (NKAα) on the inner segment plasma membrane. On the plasma membrane, mislocalized rhodopsin extracts NKAα and sends it to lysosomes where they are co-degraded. Compromised NKAα function leads to shortening and loss of the photoreceptor outer segments as observed for various inherited blinding disorders. In summary, this study revealed a novel pathogenic mechanism applicable to various forms of blinding disorders caused by rhodopsin mislocalization.
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Affiliation(s)
- Philip Ropelewski
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965
| | - Yoshikazu Imanishi
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-4965
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Wu AL, Wang JP, Tseng YJ, Liu L, Kang YC, Chen KJ, Chao AN, Yeh LK, Chen TL, Hwang YS, Wu WC, Lai CC, Wang NK. MULTIMODAL IMAGING OF MOSAIC RETINOPATHY IN CARRIERS OF HEREDITARY X-LINKED RECESSIVE DISEASES. Retina 2018; 38:1047-1057. [PMID: 28376043 DOI: 10.1097/iae.0000000000001629] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To investigate the clinical features in carriers of X-linked retinitis pigmentosa, X-linked ocular albinism, and choroideremia (CHM) using multimodal imaging and to assess their diagnostic value in these three mosaic retinopathies. METHODS We prospectively examined 14 carriers of 3 X-linked recessive disorders (X-linked retinitis pigmentosa, X-linked ocular albinism, and CHM). Details of abnormalities of retinal morphology were evaluated using fundus photography, fundus autofluorescence (FAF) imaging, and spectral domain optical coherence tomography. RESULTS In six X-linked retinitis pigmentosa carriers, fundus appearance varied from unremarkable to the presence of tapetal-like reflex and pigmentary changes. On FAF imaging, all carriers exhibited a bright radial reflex against a dark background. By spectral domain optical coherence tomography, loss of the ellipsoid zone in the macula was observed in 3 carriers (50%). Regarding the retinal laminar architecture, 4 carriers (66.7%) showed thinning of the outer nuclear layer and a dentate appearance of the outer plexiform layer. All five X-linked ocular albinism carriers showed a characteristic mud-splatter patterned fundus, dark radial streaks against a bright background on FAF imaging, and a normal-appearing retinal structure by spectral domain optical coherence tomography imaging. Two of the 3 CHM carriers (66.7%) showed a diffuse moth-eaten appearance of the fundus, and all 3 showed irregular hyper-FAF and hypo-FAF spots throughout the affected area. In the CHM carriers, the structural changes observed by spectral domain optical coherence tomography imaging were variable. CONCLUSION Our findings in an Asian cohort suggest that FAF imaging is a practical diagnostic test for differentiating X-linked retinitis pigmentosa, X-linked ocular albinism, and CHM carriers. Wide-field FAF is an easy and helpful adjunct to testing for the correct diagnosis and identification of lyonization in carriers of these three mosaic retinopathies.
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Affiliation(s)
- An-Lun Wu
- Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan
| | - Jung-Pan Wang
- Department of Orthopaedics and Traumatology, Taipei Veterans General Hospital, Taipei, Taiwan.,School of Medicine, National Yang-Ming University, Taipei, Taiwan
| | - Yun-Ju Tseng
- Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York
| | - Laura Liu
- Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Yu-Chuan Kang
- Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan
| | - Kuan-Jen Chen
- Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - An-Ning Chao
- Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Lung-Kun Yeh
- Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Tun-Lu Chen
- Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Yih-Shiou Hwang
- Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Wei-Chi Wu
- Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Chi-Chun Lai
- Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
| | - Nan-Kai Wang
- Department of Ophthalmology, Chang Gung Memorial Hospital, Taoyuan, Taiwan.,College of Medicine, Chang Gung University, Taoyuan, Taiwan
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Disease mechanisms of X-linked retinitis pigmentosa due to RP2 and RPGR mutations. Biochem Soc Trans 2017; 44:1235-1244. [PMID: 27911705 DOI: 10.1042/bst20160148] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 08/16/2016] [Accepted: 08/18/2016] [Indexed: 01/24/2023]
Abstract
Photoreceptor degeneration is the prominent characteristic of retinitis pigmentosa (RP), a heterogeneous group of inherited retinal dystrophies resulting in blindness. Although abnormalities in many pathways can cause photoreceptor degeneration, one of the most important causes is defective protein transport through the connecting cilium, the structure that connects the biosynthetic inner segment with the photosensitive outer segment of the photoreceptors. The majority of patients with X-linked RP have mutations in the retinitis pigmentosa GTPase regulator (RPGR) or RP2 genes, the protein products of which are both components of the connecting cilium and associated with distinct mechanisms of protein delivery to the outer segment. RP2 and RPGR proteins are associated with severe diseases ranging from classic RP to atypical forms. In this short review, we will summarise current knowledge generated by experimental studies and knockout animal models, compare and discuss the prominent hypotheses about the two proteins' functions in retinal cell biology.
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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: 64] [Impact Index Per Article: 8.0] [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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Megaw RD, Soares DC, Wright AF. RPGR: Its role in photoreceptor physiology, human disease, and future therapies. Exp Eye Res 2015; 138:32-41. [PMID: 26093275 PMCID: PMC4553903 DOI: 10.1016/j.exer.2015.06.007] [Citation(s) in RCA: 88] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Revised: 06/03/2015] [Accepted: 06/04/2015] [Indexed: 12/21/2022]
Abstract
Mammalian photoreceptors contain specialised connecting cilia that connect the inner (IS) to the outer segments (OS). Dysfunction of the connecting cilia due to mutations in ciliary proteins are a common cause of the inherited retinal dystrophy retinitis pigmentosa (RP). Mutations affecting the Retinitis Pigmentosa GTPase Regulator (RPGR) protein is one such cause, affecting 10-20% of all people with RP and the majority of those with X-linked RP. RPGR is located in photoreceptor connecting cilia. It interacts with a wide variety of ciliary proteins, but its exact function is unknown. Recently, there have been important advances both in our understanding of RPGR function and towards the development of a therapy. This review summarises the existing literature on human RPGR function and dysfunction, and suggests that RPGR plays a role in the function of the ciliary gate, which controls access of both membrane and soluble proteins to the photoreceptor outer segment. We discuss key models used to investigate and treat RPGR disease and suggest that gene augmentation therapy offers a realistic therapeutic approach, although important questions still remain to be answered, while cell replacement therapy based on retinal progenitor cells represents a more distant prospect.
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Affiliation(s)
- Roly D Megaw
- Scottish Centre for Regenerative Medicine, University of Edinburgh, 5 Little France Drive, Edinburgh EH16 4UU, United Kingdom.
| | - Dinesh C Soares
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom.
| | - Alan F Wright
- Medical Research Council Human Genetics Unit, Institute of Genetics and Molecular Medicine, University of Edinburgh, Edinburgh EH4 2XU, United Kingdom.
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The Role of RPGR and Its Interacting Proteins in Ciliopathies. J Ophthalmol 2015; 2015:414781. [PMID: 26124960 PMCID: PMC4466403 DOI: 10.1155/2015/414781] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2014] [Revised: 04/13/2015] [Accepted: 04/19/2015] [Indexed: 11/28/2022] Open
Abstract
Ciliopathies encompass a group of genetic disorders characterized by defects in the formation, maintenance, or function of cilia. Retinitis pigmentosa (RP) is frequently one of the clinical features presented in diverse ciliopathies. RP is a heterogeneous group of inherited retinal disorders, characterized by the death of photoreceptors and affecting more than one million individuals worldwide. The retinitis pigmentosa GTPase regulator (RPGR) gene is mutated in up to 20% of all RP patients. RPGR protein has different interacting partners to function in ciliary protein trafficking. In this review, we specifically focus on RPGR and its two interacting proteins: RPGRIP1 and RPGRIP1L. We summarize the function of the three proteins and highlight recent studies that provide insight into the cellular function of those proteins.
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12
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Wu Z, Hiriyanna S, Qian H, Mookherjee S, Campos MM, Gao C, Fariss R, Sieving PA, Li T, Colosi P, Swaroop A. A long-term efficacy study of gene replacement therapy for RPGR-associated retinal degeneration. Hum Mol Genet 2015; 24:3956-70. [PMID: 25877300 DOI: 10.1093/hmg/ddv134] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 04/13/2015] [Indexed: 11/14/2022] Open
Abstract
Mutations in the retinitis pigmentosa GTPase regulator (RPGR) gene account for >70% of X-linked retinitis pigmentosa (XLRP) and 15-20% of all inherited retinal degeneration. Gene replacement therapy for RPGR-XLRP was hampered by the relatively slow disease progression in mouse models and by difficulties in cloning the full-length RPGR-ORF15 cDNA that includes a purine-rich 3'-coding region; however, its effectiveness has recently been demonstrated in four dogs with RPGR mutations. To advance the therapy to clinical stage, we generated new stable vectors in AAV8 or AAV9 carrying mouse and human full-length RPGR-ORF15-coding sequence and conducted a comprehensive long-term dose-efficacy study in Rpgr-knockout mice. After validating their ability to produce full-length proteins that localize to photoreceptor connecting cilia, we evaluated various vector doses in mice during a 2-year study. We demonstrate that eyes treated with a single injection of mouse or human RPGR-ORF15 vector at an optimal dose maintained the expression of RPGR-ORF15 throughout the study duration and exhibited higher electroretinogram amplitude, thicker photoreceptor layer and better targeting of opsins to outer segments compared with sham-treated eyes. Furthermore, mice that received treatment at an advanced age also showed remarkable preservation of retinal structure and function. Retinal toxicity was observed at high vector doses, highlighting the importance of careful dose optimization in future clinical experiments. Our long-term dose-efficacy study should facilitate the design of human trials with human RPGR-ORF15 vector as a clinical candidate.
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Affiliation(s)
- Zhijian Wu
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Suja Hiriyanna
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Haohua Qian
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | | | - Maria M Campos
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Chun Gao
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Robert Fariss
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Paul A Sieving
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Tiansen Li
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Peter Colosi
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Anand Swaroop
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
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13
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Localizing the RPGR protein along the cilium: a new method to determine efficacies to treat RPGR mutations. Gene Ther 2015; 22:413-20. [PMID: 25630948 DOI: 10.1038/gt.2014.128] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2014] [Revised: 12/16/2014] [Accepted: 12/19/2014] [Indexed: 01/18/2023]
Abstract
Retinal dystrophies constitute a group of clinically and genetically heterogeneous diseases that cause visual impairment. As treatments are not readily available, readout assays performed in patient-derived cells can aid in the development and comparative analysis of therapeutic approaches. We describe a new method with which the localization of the retinitis pigmentosa GTPase regulator (RPGR) protein along the cilium can be used as a measure for treatment efficacy. In a patient-derived fibroblast cell line, we found that the RPGR protein is mislocalized along the ciliary axoneme. The patient carried a point mutation that leads to skipping of RPGR exon 10. We confirmed that this skipping is causative for the impaired localization of RPGR using a U7 small nuclear RNA (U7snRNA)-based antisense approach in control cells. Treatment of the patient-derived fibroblasts with therapeutic U1snRNA significantly corrected the proteins' mislocalization. In this proof of principle study, we show that detecting the RPGR protein along the cilium provides a reliable and quantifiable readout assay to evaluate the efficacy of therapies intended to correct or silence RPGR gene mutations. This method opens the possibility to compare different therapeutic agents, and thus facilitate the identification of treatment options for the clinically and molecularly complex RPGR-associated diseases.
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14
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Eblimit A, Nguyen TMT, Chen Y, Esteve-Rudd J, Zhong H, Letteboer S, Van Reeuwijk J, Simons DL, Ding Q, Wu KM, Li Y, Van Beersum S, Moayedi Y, Xu H, Pickard P, Wang K, Gan L, Wu SM, Williams DS, Mardon G, Roepman R, Chen R. Spata7 is a retinal ciliopathy gene critical for correct RPGRIP1 localization and protein trafficking in the retina. Hum Mol Genet 2014; 24:1584-601. [PMID: 25398945 DOI: 10.1093/hmg/ddu573] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Leber congenital amaurosis (LCA) and juvenile retinitis pigmentosa (RP) are severe hereditary diseases that causes visual impairment in infants and children. SPATA7 has recently been identified as the LCA3 and juvenile RP gene in humans, whose function in the retina remains elusive. Here, we show that SPATA7 localizes at the primary cilium of cells and at the connecting cilium (CC) of photoreceptor cells, indicating that SPATA7 is a ciliary protein. In addition, SPATA7 directly interacts with the retinitis pigmentosa GTPase regulator interacting protein 1 (RPGRIP1), a key connecting cilium protein that has also been linked to LCA. In the retina of Spata7 null mutant mice, a substantial reduction of RPGRIP1 levels at the CC of photoreceptor cells is observed, suggesting that SPATA7 is required for the stable assembly and localization of the ciliary RPGRIP1 protein complex. Furthermore, our results pinpoint a role of this complex in protein trafficking across the CC to the outer segments, as we identified that rhodopsin accumulates in the inner segments and around the nucleus of photoreceptors. This accumulation then likely triggers the apoptosis of rod photoreceptors that was observed. Loss of Spata7 function in mice indeed results in a juvenile RP-like phenotype, characterized by progressive degeneration of photoreceptor cells and a strongly decreased light response. Together, these results indicate that SPATA7 functions as a key member of a retinal ciliopathy-associated protein complex, and that apoptosis of rod photoreceptor cells triggered by protein mislocalization is likely the mechanism of disease progression in LCA3/ juvenile RP patients.
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Affiliation(s)
| | - Thanh-Minh T Nguyen
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen 6525, The Netherlands
| | - Yiyun Chen
- HGSC, Department of Molecular and Human Genetics
| | - Julian Esteve-Rudd
- Jules Stein Eye Institute, UCLA David Geffen School of Medicine, Los Angeles, CA 90095, USA
| | - Hua Zhong
- Department of Pathology and Immunology
| | - Stef Letteboer
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen 6525, The Netherlands
| | - Jeroen Van Reeuwijk
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen 6525, The Netherlands
| | - David L Simons
- Department of Neuroscience and Department of Ophthalmology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Qian Ding
- Department of Ophthalmology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
| | - Ka Man Wu
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen 6525, The Netherlands
| | - Yumei Li
- HGSC, Department of Molecular and Human Genetics
| | - Sylvia Van Beersum
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen 6525, The Netherlands
| | | | - Huidan Xu
- HGSC, Department of Molecular and Human Genetics
| | | | - Keqing Wang
- HGSC, Department of Molecular and Human Genetics
| | - Lin Gan
- Department of Ophthalmology, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642, USA
| | - Samuel M Wu
- Department of Neuroscience and Department of Ophthalmology, Baylor College of Medicine, Houston, TX 77030, USA
| | - David S Williams
- Jules Stein Eye Institute, UCLA David Geffen School of Medicine, Los Angeles, CA 90095, USA
| | - Graeme Mardon
- Department of Molecular and Human Genetics, Department of Pathology and Immunology, Department of Neuroscience and Department of Ophthalmology, Baylor College of Medicine, Houston, TX 77030, USA,
| | - Ronald Roepman
- Department of Human Genetics and Radboud Institute for Molecular Life Sciences, Radboud University Medical Center, Nijmegen 6525, The Netherlands,
| | - Rui Chen
- HGSC, Department of Molecular and Human Genetics,
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15
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Beltran WA, Cideciyan AV, Lewin AS, Hauswirth WW, Jacobson SG, Aguirre GD. Gene augmentation for X-linked retinitis pigmentosa caused by mutations in RPGR. Cold Spring Harb Perspect Med 2014; 5:a017392. [PMID: 25301933 DOI: 10.1101/cshperspect.a017392] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
X-linked retinitis pigmentosa (XLRP) caused by mutations in the RPGR gene is a severe and early onset form of retinal degeneration, and no treatment is currently available. Recent evidence in two clinically relevant canine models shows that adeno-associated viral (AAV)-mediated RPGR gene transfer to rods and cones can prevent disease onset and rescue photoreceptors at early- and mid-stages of degeneration. There is thus a strong incentive for conducting long-term, preclinical efficacy and safety studies, while concomitantly pursuing the detailed phenotypic characterization of XLRP disease in patients that may benefit from such corrective therapy.
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Affiliation(s)
- William A Beltran
- Section of Ophthalmology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Artur V Cideciyan
- Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104
| | - Alfred S Lewin
- Department of Molecular Genetics & Microbiology, University of Florida, Gainesville, Florida 32610
| | - William W Hauswirth
- Department of Ophthalmology, University of Florida, Gainesville, Florida 32610
| | - Samuel G Jacobson
- Scheie Eye Institute, Department of Ophthalmology, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104
| | - Gustavo D Aguirre
- Section of Ophthalmology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104
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16
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Pyo Park S, Hwan Hong I, Tsang SH, Chang S. Cellular imaging demonstrates genetic mosaicism in heterozygous carriers of an X-linked ciliopathy gene. Eur J Hum Genet 2013; 21:1240-8. [PMID: 23443027 PMCID: PMC3798832 DOI: 10.1038/ejhg.2013.21] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2012] [Revised: 11/02/2012] [Accepted: 01/24/2013] [Indexed: 11/09/2022] Open
Abstract
X-linked retinitis pigmentosa (XLRP) is the least common genetic type of retinitis pigmentosa; however, it has extremely devastating consequences to patients' activities of daily living. RPGR and RP2 genes expressed in the photoreceptor sensory cilia are predominantly implicated in XLRP; however, the interpretation of genetic mutations and their correlation with clinical phenotypes remain unknown, and the role of these genes in photoreceptor cilia function is not completely elucidated. Therefore, we evaluated structural characteristics in five female obligate carriers of XLRP by using state-of-the-art non-invasive imaging methods, including adaptive optics (AO) scanning laser ophthalmoscopy (SLO). In all five carriers examined, qualitative and quantitative analyses by AO SLO imaging revealed a mosaic pattern of cone disruption, even in the absence of visual symptoms, normal visual acuity and normal macular thickness, on optical coherence tomography and mildly subnormal full-field cone electroretinographic findings. As the technique is sensitive to the level of a single cone, the ability to visualize the cone cells in vivo should be especially useful in other retinal diseases. In addition, further investigation of XLRP carriers may yield insight into how cone structures change over time and ultimately enable understanding of the role of RPGR and RP2 in cone cell survival.
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Affiliation(s)
- Sung Pyo Park
- Department of Ophthalmology, Columbia University, New York, NY, USA
- Department of Ophthalmology, Kangdong Sacred Heart Hospital, Hallym University Medical Center, Seoul, South Korea
| | - In Hwan Hong
- Department of Ophthalmology, Kangdong Sacred Heart Hospital, Hallym University Medical Center, Seoul, South Korea
| | - Stephen H Tsang
- Department of Ophthalmology, Columbia University, New York, NY, USA
- Department of Pathology and Cell Biology, Columbia University, New York, NY, USA
| | - Stanley Chang
- Department of Ophthalmology, Columbia University, New York, NY, USA
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17
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Abstract
PURPOSE OF REVIEW To describe the entity of Lyonization in ocular eye diseases, along with its clinical and counseling implications. RECENT FINDINGS Several X-linked ocular diseases such as choroideremia, X-linked retinitis pigmentosa, and X-linked ocular albinism may have signs of Lyonization on ocular examination and diagnostic testing. These findings may aid in the proper diagnosis of ocular disease in both female carriers and their affected male relatives. SUMMARY Manifestations of Lyonization in the eye may help in the diagnosis of X-linked ocular diseases which may lead to accurate diagnosis, appropriate molecular genetic testing and genetic counseling.
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18
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Raghupathy RK, McCulloch DL, Akhtar S, Al-mubrad TM, Shu X. Zebrafish model for the genetic basis of X-linked retinitis pigmentosa. Zebrafish 2013; 10:62-9. [PMID: 23536988 DOI: 10.1089/zeb.2012.0761] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Retinitis pigmentosa (RP) affects 1/4000 individuals in most populations, and X-linked RP (XLRP) is one of the most severe forms of human retinal degeneration. Mutations in both the retinitis pigmentosa GTPase regulator (RPGR) gene and retinitis pigmentosa 2 (RP2) gene account for almost all cases of XLRP. The functional roles of both RPGR and RP2 in the pathogenesis of XLRP are unclear. Due to the surprisingly high degree of functional conservation between human genes and their zebrafish orthologues, the zebrafish has become an important model for human retinal disorders. In this brief review, we summarize the functional characterization of XLRP-causing genes, RPGR and RP2, in zebrafish, and highlight recent studies that provide insight into the cellular functions of both genes. This will not only shed light on disease mechanisms in XLRP but will also provide a solid platform to test RP-causing mutants before proposing XLRP gene therapy trials.
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Sustained protection against photoreceptor degeneration in tubby mice by intravitreal injection of nanoceria. Biomaterials 2012; 33:8771-81. [PMID: 22959465 DOI: 10.1016/j.biomaterials.2012.08.030] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2012] [Accepted: 08/13/2012] [Indexed: 02/05/2023]
Abstract
We previously reported that nanoceria can slow retinal degeneration in the tubby mouse for two weeks by multiple systemic injections. However, the long-term protection of retinal structure and function by directly deliver of nanoceria to the eye had not been explored. In this study, 172 ng of nanoceria in 1 μl saline (1 mm) were intravitreally injected into tubby P7 pups and assays were performed at P28, P49, P80 and P120. The expression of antioxidant associated genes and photoreceptor-specific genes was significantly up regulated, the mislocalization of rod and cone opsins was decreased, and retinal structure and function were protected. These findings demonstrate that nanoceria can function as catalytic antioxidants in vivo and may be broad spectrum therapeutic agents for multiple types of ocular diseases.
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20
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Cai X, Sezate SA, Seal S, McGinnis JF. WITHDRAWN: Sustained protection against photoreceptor degeneration in tubby mice by intravitreal injection of nanoceria. Biomaterials 2012:S0142-9612(12)00767-3. [PMID: 22871422 DOI: 10.1016/j.biomaterials.2012.06.102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2012] [Accepted: 06/30/2012] [Indexed: 11/21/2022]
Abstract
This article has been withdrawn at the request of the author(s) and/or editor. The Publisher apologizes for any inconvenience this may cause. The full Elsevier Policy on Article Withdrawal can be found at http://www.elsevier.com/locate/withdrawalpolicy.
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Affiliation(s)
- Xue Cai
- Department of Ophthalmology, Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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21
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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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23
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Hollingsworth TJ, Gross AK. Defective trafficking of rhodopsin and its role in retinal degenerations. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 293:1-44. [PMID: 22251557 DOI: 10.1016/b978-0-12-394304-0.00006-3] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Retinitis pigmentosa is a retinal degeneration transmitted by varied modes of inheritance and affects approximately 1 in 4000 individuals. The photoreceptors of the outer retina, as well as the retinal pigmented epithelium which supports the outer retina metabolically and structurally, are the retinal regions most affected by the disorder. In several forms of retinitis pigmentosa, the mislocalization of the rod photoreceptor protein rhodopsin is thought to be a contributing factor underlying the pathophysiology seen in patients. The mutations causing this mislocalization often occur in genes coding proteins involved in ciliary formation, vesicular transport, rod outer segment disc formation, and stability, as well as the rhodopsin protein itself. Often, these mutations result in the most early-onset cases of both recessive and dominant retinitis pigmentosa, and the following presents a discussion of the proteins, their degenerative phenotypes, and possible treatments of the disease.
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Affiliation(s)
- T J Hollingsworth
- Department of Vision Sciences, University of Alabama, Birmingham, Alabama, USA
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24
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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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25
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Hosch J, Lorenz B, Stieger K. RPGR: role in the photoreceptor cilium, human retinal disease, and gene therapy. Ophthalmic Genet 2010; 32:1-11. [PMID: 21174525 DOI: 10.3109/13816810.2010.535889] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cilia are specialized dynamic organelles extending from the surface of almost all mammalian cells. Since proteins and protein precursors are transported across the ciliary compartments via intraflagellar transport (IFT), mutations in genes encoding proteins that participate in IFT can cause a spectrum of different ciliopathies. Photoreceptors of the mammalian retina contain ciliary structures that connect the inner (IS) with the outer segments (OS). This structure, the connecting cilium (CC), serves as the only junction between OS and IS, the correct passage of proteins through the CC is crucial for the functioning and maintenance of the cells. Therefore, any impairment of the IFT leads to severe malfunction of photoreceptors, and may induce apoptosis ultimately leading to the degeneration of the retina. The Retinitis Pigmentosa GTPase Regulator (RPGR), which is located in the CC, participates in the IFT and interacts with a variety of proteins, including RPGRIP-1, CEP290, NPM, SMC1 and 3 and IFT88. However, the function of RPGR through its interaction with these proteins is not yet entirely understood. Mutations in the RPGR gene lead to X-linked Retinitis pigmentosa (XLRP), one of the most severe and early onset forms of RP. Gene therapy is considered a potential therapeutic option and is currently under investigation in several animal models of XLRP. However, some of the currently available mouse models are only partially suitable for the development of therapeutic strategies and the quest for more appropriate small animal models is still an issue.
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Affiliation(s)
- Jutta Hosch
- Department of Ophthalmology, Justus-Liebig-University Giessen, Giessen, Germany
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Shu X, Zeng Z, Gautier P, Lennon A, Gakovic M, Patton EE, Wright AF. Zebrafish Rpgr is required for normal retinal development and plays a role in dynein-based retrograde transport processes. Hum Mol Genet 2009; 19:657-70. [DOI: 10.1093/hmg/ddp533] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
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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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Loss of the cholesterol-binding protein prominin-1/CD133 causes disk dysmorphogenesis and photoreceptor degeneration. J Neurosci 2009; 29:2297-308. [PMID: 19228982 DOI: 10.1523/jneurosci.2034-08.2009] [Citation(s) in RCA: 137] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Prominin-1/CD133 (Prom-1) is a commonly used marker of neuronal, vascular, hematopoietic and other stem cells, yet little is known about its biological role and importance in vivo. Here, we show that loss of Prom-1 results in progressive degeneration of mature photoreceptors with complete loss of vision. Despite the expression of Prom-1 on endothelial progenitors, photoreceptor degeneration was not attributable to retinal vessel defects, but caused by intrinsic photoreceptor defects in disk formation, outer segment morphogenesis, and associated with visual pigment sorting and phototransduction abnormalities. These findings shed novel insight on how Prom-1 regulates neural retinal development and phototransduction in vertebrates.
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Beltran WA, Acland GM, Aguirre GD. Age-dependent disease expression determines remodeling of the retinal mosaic in carriers of RPGR exon ORF15 mutations. Invest Ophthalmol Vis Sci 2009; 50:3985-95. [PMID: 19255154 DOI: 10.1167/iovs.08-3364] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To characterize the retinal histopathology in carriers of X-linked progressive retinal atrophy (XLPRA1 and XLPRA2), two canine models of X-linked retinitis pigmentosa caused, respectively, by a stop and a frameshift mutation in RPGRORF15. METHODS Retinas of XLPRA2 and XLPRA1 carriers of different ages were processed for morphologic evaluation, TUNEL assay, and immunohistochemistry. Cell-specific markers were used to examine retinal remodeling events. RESULTS A mosaic pattern composed of patches of diseased and normal retina was first detected in XLPRA2 carriers at 4.9 weeks of age. A peak of photoreceptor cell death led to focal rod loss; however, in these patches an increased density of cones was found to persist over time. Patches of disease gradually disappeared so that by 39 weeks of age the overall retinal morphology, albeit thinner, had improved lamination. In older XLPRA2 carriers (>or=8.8 years), extended regions of severe degeneration occurred in the peripheral/mid-peripheral retina. In XLPRA1 carriers, opsin mislocalization and rare events of rod death were detected by TUNEL assay at 20 weeks of age; however, only patchy degeneration was seen by 1.4 years and was still apparent at 7.8 years. CONCLUSIONS The time of onset and the progression of the disease differed between the two models. In the early-onset form (XLPRA2) the morphologic appearance of the retinal mosaic changed as a function of age, suggesting that structural plasticity persists in the early postnatal canine retina as mutant photoreceptors die. In the late-onset form (XLPRA1), patches of disease persisted until later ages.
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Affiliation(s)
- William A Beltran
- School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104,
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Abstract
While the functions of many of the proteins located in or associated with the photoreceptor cilia are poorly understood, disruption of the function of these proteins may result in a wide variety of phenotypes ranging from isolated retinal degeneration to more pleiotropic phenotypes. Systemic findings include neurosensory hearing loss, developmental delay, situs-inversus, infertility, disorders of limb and digit development, obesity, kidney disease, liver disease, and respiratory disease. The concept of "retinal ciliopathies" brings to attention the importance of further molecular analysis of this organelle as well as provides a potential common target for therapies for these disorders. The retinal ciliopathies include retinitis pigmentosa, macular degeneration, cone-dystrophy, cone-rod dystrophy, Leber congenital amaurosis, as well as retinal degenerations associated with Usher syndrome, primary ciliary dyskinesia, Senior-Loken syndrome, Joubert syndrome, Bardet-Biedl syndrome, Laurence-Moon syndrome, McKusick-Kaufman syndrome, and Biemond syndrome. Mutations for these disorders have been found in retinitis pigmentosa-1 (RP1), retinitis pigmentosa GTPase regulator (RPGR), retinitis pigmentosa GTPase regulator interacting protein (RPGR-IP), as well as the Usher, Bardet-Biedl, and nephronophthisis genes. Other systemic disorders associated with retinal degenerations that may also involve ciliary abnormalities include: Alstrom, Edwards-Sethi, Ellis-van Creveld, Jeune, Meckel-Gruber, Orofaciodigital Type 9, and Gurrieri syndromes. Understanding these conditions as ciliopathies may help the ophthalmologist to recognize associations between seemingly unrelated diseases and have a high degree of suspicion that a systemic finding may be present.
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Affiliation(s)
- N A Adams
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland 21287, USA.
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