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Ku CA, Wei LW, Sieving PA. X-Linked Retinoschisis. Cold Spring Harb Perspect Med 2023; 13:a041288. [PMID: 36690462 PMCID: PMC10513161 DOI: 10.1101/cshperspect.a041288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
X-linked retinoschisis (XLRS) is an inherited vitreoretinal dystrophy causing visual impairment in males starting at a young age with an estimated prevalence of 1:5000 to 1:25,000. The condition was first observed in two affected brothers by Josef Haas in 1898 and is clinically diagnosed by characteristic intraretinal cysts arranged in a petaloid "spoke-wheel" pattern centered in the macula. When clinical electroretinogram (ERG) testing began in the 1960s, XLRS was noted to have a characteristic reduction of the dark-adapted b-wave amplitude despite normal or usually nearly normal a-wave amplitudes, which became known as the "electronegative ERG response" of XLRS disease. The causative gene, RS1, was identified on the X-chromosome in 1997 and led to understanding the molecular and cellular basis of the condition, discerning the structure and function of the retinoschisin protein, and generating XLRS murine models. Along with parallel development of gene delivery vectors suitable for targeting retinal diseases, successful gene augmentation therapy was demonstrated by rescuing the XLRS phenotype in mouse. Two human phase I/II therapeutic XLRS gene augmentation studies were initiated; and although these did not yield definitive improvement in visual function, they gave significant new knowledge and experience, which positions the field for further near-term clinical testing with enhanced, next-generation gene therapy for XLRS patients.
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Affiliation(s)
- Cristy A Ku
- Department of Ophthalmology & Vision Science, University of California Davis, Sacramento, California 95817, USA
| | - Lisa W Wei
- National Institutes of Health, National Institute of Allergy and Infectious Diseases, NIH Office of Biodefense, Research Resources and Translational Research/Vaccine Section, Bethesda, Maryland 20892, USA
| | - Paul A Sieving
- Department of Ophthalmology & Vision Science, University of California Davis, Sacramento, California 95817, USA
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Fenner BJ, Russell JF, Drack AV, Dumitrescu AV, Sohn EH, Russell SR, Boldt HC, Affatigato LM, Hoffmann JM, Andorf JL, Stone EM, Han IC. Long-term functional and structural outcomes in X-linked retinoschisis: implications for clinical trials. Front Med (Lausanne) 2023; 10:1204095. [PMID: 37396901 PMCID: PMC10310546 DOI: 10.3389/fmed.2023.1204095] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2023] [Accepted: 05/26/2023] [Indexed: 07/04/2023] Open
Abstract
Introduction X-linked retinoschisis (XLRS) is an inherited retinal disease (IRD) caused by pathogenic mutations in the retinoschisin gene, RS1. Affected individuals develop retinal layer separation, leading to loss of visual acuity (VA). Several XLRS gene therapy trials have been attempted but none have met their primary endpoints. An improved understanding of XLRS natural history and clinical outcomes may better inform future trials. Here, we report the long-term functional and structural outcomes of XLRS and the relevance of RS1 genotypes to the visual prognosis of affected individuals. Methods A retrospective chart review of patients with molecularly confirmed X-linked retinoschisis was performed. Functional and structural outcomes, and RS1 genotype data, were included for analysis. Results Fifty-two patients with XLRS from 33 families were included in the study. Median age at symptom onset was 5 years (range 0-49) and median follow-up was 5.7 years (range 0.1-56.8). Macular retinoschisis occurred in 103 of 104 eyes (99.0%), while peripheral retinoschisis occurred in 48 of 104 eyes (46.2%), most often in the inferotemporal quadrant (40.4%). Initial and final VA were similar (logMAR 0.498 vs. 0.521; p = 0.203). Fifty of 54 eyes (92.6%) developed detectable outer retinal loss by age 20, and 29 of 66 eyes (43.9%) had focal or diffuse outer retinal atrophy (ORA) by age 40. ORA but not central subfield thickness (CST) was associated with reduced VA. Inter-eye correlation was modest for VA (r-squared = 0.03; p = 0.08) and CST (r-squared = 0.15; p = 0.001). Carbonic anhydrase inhibitors (CAIs) improved CST (p = 0.026), but not VA (p = 0.380). Eight of 104 eyes (7.7%) had XLRS-related retinal detachment (RD), which was associated with poorer outcomes compared to eyes without RD (median final VA 0.875 vs. 0.487; p <0.0001). RS1 null genotypes had greater odds of at least moderate visual impairment at final follow-up (OR 7.81; 95% CI 2.17, 28.10; p = 0.002) which was independent of age at onset, initial CST, initial ORA, or previous RD. Discussion Overall, long-term follow-up of XLRS patients demonstrated relatively stable VA, with presenting CST, development of ORA, and null RS1 mutations associated with poorer long-term visual outcomes, indicating a clinically relevant genotype-phenotype correlation in XLRS.
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Affiliation(s)
- Beau J. Fenner
- Institute for Vision Research, University of Iowa, Iowa City, IA, United States
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
- Department of Medical Retina, Singapore National Eye Centre, Singapore, Singapore
- Singapore Eye Research Institute, Singapore, Singapore
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-NUS Graduate Medical School, Singapore, Singapore
| | - Jonathan F. Russell
- Institute for Vision Research, University of Iowa, Iowa City, IA, United States
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - Arlene V. Drack
- Institute for Vision Research, University of Iowa, Iowa City, IA, United States
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - Alina V. Dumitrescu
- Institute for Vision Research, University of Iowa, Iowa City, IA, United States
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - Elliott H. Sohn
- Institute for Vision Research, University of Iowa, Iowa City, IA, United States
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - Stephen R. Russell
- Institute for Vision Research, University of Iowa, Iowa City, IA, United States
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - H. Culver Boldt
- Institute for Vision Research, University of Iowa, Iowa City, IA, United States
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | | | - Jeremy M. Hoffmann
- Institute for Vision Research, University of Iowa, Iowa City, IA, United States
| | - Jeaneen L. Andorf
- Institute for Vision Research, University of Iowa, Iowa City, IA, United States
| | - Edwin M. Stone
- Institute for Vision Research, University of Iowa, Iowa City, IA, United States
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
| | - Ian C. Han
- Institute for Vision Research, University of Iowa, Iowa City, IA, United States
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, United States
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Vijayasarathy C, Zeng Y, Marangoni D, Dong L, Pan ZH, Simpson EM, Fariss RN, Sieving PA. Targeted Expression of Retinoschisin by Retinal Bipolar Cells in XLRS Promotes Resolution of Retinoschisis Cysts Sans RS1 From Photoreceptors. Invest Ophthalmol Vis Sci 2022; 63:8. [PMID: 36227606 PMCID: PMC9583743 DOI: 10.1167/iovs.63.11.8] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2022] [Accepted: 09/18/2022] [Indexed: 01/14/2023] Open
Abstract
Purpose Loss of retinoschisin (RS1) function underlies X-linked retinoschisis (XLRS) pathology. In the retina, both photoreceptor inner segments and bipolar cells express RS1. However, the loss of RS1 function causes schisis primarily in the inner retina. To understand these cell type-specific phenotypes, we decoupled RS1 effects in bipolar cells from that in photoreceptors. Methods Bipolar cell transgene RS1 expression was achieved using two inner retina-specific promoters: (1) a minimal promoter engineered from glutamate receptor, metabotropic glutamate receptor 6 gene (mini-mGluR6/ Grm6) and (2) MiniPromoter (Ple155). Adeno-associated virus vectors encoding RS1 gene under either the mini-mGluR6 or Ple-155 promoter were delivered to the XLRS mouse retina through intravitreal or subretinal injection on postnatal day 14. Retinal structure and function were assessed 5 weeks later: immunohistochemistry for morphological characterization, optical coherence tomography and electroretinography (ERG) for structural and functional evaluation. Results Immunohistochemical analysis of RS1expression showed that expression with the MiniPromoter (Ple155) was heavily enriched in bipolar cells. Despite variations in vector penetrance and gene transfer efficiency across the injected retinas, those retinal areas with robust bipolar cell RS1 expression showed tightly packed bipolar cells with fewer cavities and marked improvement in inner retinal structure and synaptic function as judged by optical coherence tomography and electroretinography, respectively. Conclusions These results demonstrate that RS1 gene expression primarily in bipolar cells of the XLRS mouse retina, independent of photoreceptor expression, can ameliorate retinoschisis structural pathology and provide further evidence of RS1 role in cell adhesion.
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Affiliation(s)
- Camasamudram Vijayasarathy
- Section for Translational Research in Retinal and Macular Degeneration, National Institutes of Health, Bethesda, Maryland, United States
| | - Yong Zeng
- Section for Translational Research in Retinal and Macular Degeneration, National Institutes of Health, Bethesda, Maryland, United States
| | - Dario Marangoni
- Section for Translational Research in Retinal and Macular Degeneration, National Institutes of Health, Bethesda, Maryland, United States
| | - Lijin Dong
- Genetic Engineering Facility, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Zhuo-Hua Pan
- Department of Ophthalmology, Visual and Anatomical Sciences, Wayne State University School of Medicine, Detroit, Michigan, United States
| | - Elizabeth M. Simpson
- Centre for Molecular Medicine and Therapeutics at BC Children's Hospital, University of British Columbia, Vancouver, British Columbia, Canada
| | - Robert N. Fariss
- Biological Imaging Core, National Eye Institute, National Institutes of Health, Bethesda, Maryland, United States
| | - Paul A. Sieving
- Section for Translational Research in Retinal and Macular Degeneration, National Institutes of Health, Bethesda, Maryland, United States
- Center for Ocular Regenerative Therapy, Department of Ophthalmology, University of California Davis, United States
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Schmid V, Wurzel A, Wetzel CH, Plössl K, Bruckmann A, Luckner P, Weber BHF, Friedrich U. Retinoschisin and novel Na/K-ATPase interaction partners Kv2.1 and Kv8.2 define a growing protein complex at the inner segments of mammalian photoreceptors. Cell Mol Life Sci 2022; 79:448. [PMID: 35876901 PMCID: PMC9314279 DOI: 10.1007/s00018-022-04409-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2022] [Revised: 05/05/2022] [Accepted: 05/30/2022] [Indexed: 11/28/2022]
Abstract
The RS1 gene on Xp 22.13 encodes retinoschisin which is known to directly interact with the retinal Na/K-ATPase at the photoreceptor inner segments. Pathologic mutations in RS1 cause X-linked juvenile retinoschisis (XLRS), a hereditary retinal dystrophy in young males. To further delineate the retinoschisin-Na/K-ATPase complex, co-immunoprecipitation was performed with porcine and murine retinal lysates targeting the ATP1A3 subunit. This identified the voltage-gated potassium (Kv) channel subunits Kv2.1 and Kv8.2 as direct interaction partners of the retinal Na/K-ATPase. Colocalization of the individual components of the complex was demonstrated at the membrane of photoreceptor inner segments. We further show that retinoschisin-deficiency, a frequent consequence of molecular pathology in XLRS, causes mislocalization of the macromolecular complex during postnatal retinal development with a simultaneous reduction of Kv2.1 and Kv8.2 protein expression, while the level of retinal Na/K-ATPase expression remains unaffected. Patch-clamp analysis revealed no effect of retinoschisin-deficiency on Kv channel mediated potassium ion currents in vitro. Together, our data suggest that Kv2.1 and Kv8.2 together with retinoschisin and the retinal Na/K-ATPase are integral parts of a macromolecular complex at the photoreceptor inner segments. Defective compartmentalization of this complex due to retinoschisin-deficiency may be a crucial step in initial XLRS pathogenesis.
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Affiliation(s)
- Verena Schmid
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany
| | - Alexander Wurzel
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany
| | - Christian H Wetzel
- Department of Psychiatry and Psychotherapy, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany
| | - Karolina Plössl
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany
| | - Astrid Bruckmann
- Institute of Biochemistry, Genetics and Microbiology, Protein Mass Spectrometry Group, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Patricia Luckner
- Institute of Biochemistry, Genetics and Microbiology, Protein Mass Spectrometry Group, University of Regensburg, Universitätsstraße 31, 93053, Regensburg, Germany
| | - Bernhard H F Weber
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany.
- Institute of Clinical Human Genetics, University Hospital Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany.
| | - Ulrike Friedrich
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany.
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Gorenberg EL, Massaro Tieze S, Yücel B, Zhao HR, Chou V, Wirak GS, Tomita S, Lam TT, Chandra SS. Identification of substrates of palmitoyl protein thioesterase 1 highlights roles of depalmitoylation in disulfide bond formation and synaptic function. PLoS Biol 2022; 20:e3001590. [PMID: 35358180 PMCID: PMC9004782 DOI: 10.1371/journal.pbio.3001590] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 04/12/2022] [Accepted: 03/02/2022] [Indexed: 12/30/2022] Open
Abstract
Loss-of-function mutations in the depalmitoylating enzyme palmitoyl protein thioesterase 1 (PPT1) cause neuronal ceroid lipofuscinosis (NCL), a devastating neurodegenerative disease. The substrates of PPT1 are largely undescribed, posing a limitation on molecular dissection of disease mechanisms and therapeutic development. Here, we provide a resource identifying >100 novel PPT1 substrates. We utilized Acyl Resin-Assisted Capture (Acyl RAC) and mass spectrometry to identify proteins with increased in vivo palmitoylation in PPT1 knockout (KO) mouse brains. We then validated putative substrates through direct depalmitoylation with recombinant PPT1. This stringent screen elucidated diverse PPT1 substrates at the synapse, including channels and transporters, G-protein–associated molecules, endo/exocytic components, synaptic adhesion molecules, and mitochondrial proteins. Cysteine depalmitoylation sites in transmembrane PPT1 substrates frequently participate in disulfide bonds in the mature protein. We confirmed that depalmitoylation plays a role in disulfide bond formation in a tertiary screen analyzing posttranslational modifications (PTMs). Collectively, these data highlight the role of PPT1 in mediating synapse functions, implicate molecular pathways in the etiology of NCL and other neurodegenerative diseases, and advance our basic understanding of the purpose of depalmitoylation.
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Affiliation(s)
- Erica L. Gorenberg
- Departments of Neurology and Neuroscience, Yale University, New Haven, Connecticut, United States of America
- Interdepartmental Neuroscience Program, Yale University, New Haven, Connecticut, United States of America
| | - Sofia Massaro Tieze
- Departments of Neurology and Neuroscience, Yale University, New Haven, Connecticut, United States of America
- Interdepartmental Neuroscience Program, Yale University, New Haven, Connecticut, United States of America
| | - Betül Yücel
- Departments of Neurology and Neuroscience, Yale University, New Haven, Connecticut, United States of America
| | - Helen R. Zhao
- Departments of Neurology and Neuroscience, Yale University, New Haven, Connecticut, United States of America
| | - Vicky Chou
- Departments of Neurology and Neuroscience, Yale University, New Haven, Connecticut, United States of America
| | - Gregory S. Wirak
- Departments of Neurology and Neuroscience, Yale University, New Haven, Connecticut, United States of America
| | - Susumu Tomita
- Departments of Neuroscience and of Cellular and Molecular Physiology, Yale University, New Haven, Connecticut, United States of America
| | - TuKiet T. Lam
- Departments of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, United States of America
- Keck MS & Proteomics Resource, WM Keck Biotechnology Resource Laboratory, New Haven, Connecticut, United States of America
| | - Sreeganga S. Chandra
- Departments of Neurology and Neuroscience, Yale University, New Haven, Connecticut, United States of America
- * E-mail:
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Vijaysarathy C, Babu Sardar Pasha SP, Sieving PA. Of men and mice: Human X-linked retinoschisis and fidelity in mouse modeling. Prog Retin Eye Res 2021; 87:100999. [PMID: 34390869 DOI: 10.1016/j.preteyeres.2021.100999] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 08/02/2021] [Accepted: 08/06/2021] [Indexed: 02/07/2023]
Abstract
X-linked Retinoschisis (XLRS) is an early-onset transretinal dystrophy, often with a prominent macular component, that affects males and generally spares heterozygous females because of X-linked recessive inheritance. It results from loss-of-function RS1 gene mutations on the X-chromosome. XLRS causes bilateral reduced acuities from young age, and on clinical exam and by ocular coherence tomography (OCT) the neurosensory retina shows foveo-macular cystic schisis cavities in the outer plexiform (OPL) and inner nuclear layers (INL). XLRS manifests between infancy and school-age with variable phenotypic presentation and without reliable genotype-phenotype correlations. INL disorganization disrupts synaptic signal transmission from photoreceptors to ON-bipolar cells, and this reduces the electroretinogram (ERG) bipolar b-wave disproportionately to photoreceptor a-wave changes. RS1 gene expression is localized mainly to photoreceptors and INL bipolar neurons, and RS1 protein is thought to play a critical cell adhesion role during normal retinal development and later for maintenance of retinal structure. Several independent XLRS mouse models with mutant RS1 were created that recapitulate features of human XLRS disease, with OPL-INL schisis cavities, early onset and variable phenotype across mutant models, and reduced ERG b-wave to a-wave amplitude ratio. The faithful phenotype of the XLRS mouse has assisted in delineating the disease pathophysiology. Delivery to XLRS mouse retina of an AAV8-RS1 construct under control of the RS1 promoter restores the retinal structure and synaptic function (with increase of b-wave amplitude). It also ameliorates the schisis-induced inflammatory microglia phenotype toward a state of immune quiescence. The results imply that XLRS gene therapy could yield therapeutic benefit to preserve morphological and functional retina particularly when intervention is conducted at earlier ages before retinal degeneration becomes irreversible. A phase I/IIa single-center, open-label, three-dose-escalation clinical trial reported a suitable safety and tolerability profile of intravitreally administered AAV8-RS1 gene replacement therapy for XLRS participants. Dose-related ocular inflammation occurred after dosing, but this resolved with topical and oral corticosteroids. Systemic antibodies against AAV8 increased in dose-dependent fashion, but no antibodies were observed against the RS1 protein. Retinal cavities closed transiently in one participant. Technological innovations in methods of gene delivery and strategies to further reduce immune responses are expected to enhance the therapeutic efficacy of the vector and ultimate success of a gene therapy approach.
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Affiliation(s)
| | | | - Paul A Sieving
- National Eye Institute, National Institutes of Health, Bethesda, Maryland, 20892, USA; Department of Ophthalmology, University of California Davis, 95817, USA.
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Biasella F, Plössl K, Karl C, Weber BHF, Friedrich U. Altered Protein Function Caused by AMD-associated Variant rs704 Links Vitronectin to Disease Pathology. Invest Ophthalmol Vis Sci 2020; 61:2. [PMID: 33259607 PMCID: PMC7718807 DOI: 10.1167/iovs.61.14.2] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2020] [Accepted: 11/07/2020] [Indexed: 12/13/2022] Open
Abstract
Purpose Vitronectin, a cell adhesion and spreading factor, is suspected to play a role in the pathogenesis of age-related macular degeneration (AMD), as it is a major component of AMD-specific extracellular deposits (e.g., soft drusen, subretinal drusenoid deposits). The present study addressed the impact of AMD-associated non-synonymous variant rs704 in the vitronectin-encoding gene VTN on vitronectin functionality. Methods Effects of rs704 on vitronectin expression and processing were analyzed by semi-quantitative sequencing of VTN transcripts from retinal pigment epithelium (RPE) cells generated from human induced pluripotent stem cells (hiPSCs) and from human neural retina, as well as by western blot analyses on heterologously expressed vitronectin isoforms. Binding of vitronectin isoforms to retinal and endothelial cells was analyzed by western blot. Immunofluorescence staining followed extracellular matrix (ECM) deposition in cultured RPE cells heterologously expressing the vitronectin isoforms. Adhesion of fluorescently labeled RPE or endothelial cells in dependence of recombinant vitronectin or vitronectin-containing ECM was investigated fluorometrically or microscopically. Tube formation and migration assays addressed effects of vitronectin on angiogenesis-related processes. Results Variant rs704 affected expression, secretion, and processing but not oligomerization of vitronectin. Cell binding and influence on RPE-mediated ECM deposition differed between AMD-risk-associated and non-AMD-risk-associated protein isoforms. Finally, vitronectin affected adhesion and endothelial tube formation. Conclusions The AMD-risk-associated vitronectin isoform exhibits increased expression and altered functionality in cellular processes related to the sub-RPE aspects of AMD pathology. Although further research is required to address the subretinal disease aspects, this initial study supports an involvement of vitronectin in AMD pathogenesis.
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Affiliation(s)
- Fabiola Biasella
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Karolina Plössl
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Claudia Karl
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Bernhard H. F. Weber
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
- Institute of Clinical Human Genetics, University Hospital Regensburg, Regensburg, Germany
| | - Ulrike Friedrich
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
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Schmid V, Plössl K, Schmid C, Bernklau S, Weber BHF, Friedrich U. Retinoschisin and Cardiac Glycoside Crosstalk at the Retinal Na/K-ATPase. Invest Ophthalmol Vis Sci 2020; 61:1. [PMID: 32392309 PMCID: PMC7405613 DOI: 10.1167/iovs.61.5.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Purpose Mutations in the RS1 gene, which encodes retinoschisin, cause X-linked juvenile retinoschisis, a retinal dystrophy in males. Retinoschisin specifically interacts with the retinal sodium–potassium adenosine triphosphatase (Na/K-ATPase), a transmembrane ion pump. Na/K-ATPases also bind cardiac glycosides, which control the activity of the pump and have been linked to disturbances in retinal homeostasis. In this study, we investigated the crosstalk between retinoschisin and cardiac glycosides at the retinal Na/K-ATPase and the consequences of this interplay on retinal integrity. Methods The effect of cardiac glycosides (ouabain and digoxin) on the binding of retinoschisin to the retinal Na/K-ATPase was investigated via western blot and immunocytochemistry. Also, the influence of retinoschisin on the binding of cardiac glycosides was analyzed via enzymatic assays, which quantified cardiac glycoside-sensitive Na/K-ATPase pump activity. Moreover, retinoschisin-dependent binding of tritium-labeled ouabain to the Na/K-ATPase was determined. Finally, a reciprocal effect of retinoschisin and cardiac glycosides on Na/K-ATPase localization and photoreceptor degeneration was addressed using immunohistochemistry in retinoschisin-deficient murine retinal explants. Results Cardiac glycosides displaced retinoschisin from the retinal Na/K-ATPase; however, retinoschisin did not affect cardiac glycoside binding. Notably, cardiac glycosides reduced the capacity of retinoschisin to regulate Na/K-ATPase localization and to protect against photoreceptor degeneration. Conclusions Our findings reveal opposing effects of retinoschisin and cardiac glycosides on retinal Na/K-ATPase binding and on retinal integrity, suggesting that a fine-tuned interplay between both components is required to maintain retinal homeostasis. This observation provides new insight into the mechanisms underlying the pathological effects of cardiac glycoside treatment on retinal integrity.
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Ropelewski P, Imanishi Y. RPE Cells Engulf Microvesicles Secreted by Degenerating Rod Photoreceptors. eNeuro 2020; 7:ENEURO.0507-19.2020. [PMID: 32376599 PMCID: PMC7242815 DOI: 10.1523/eneuro.0507-19.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2019] [Revised: 04/10/2020] [Accepted: 04/24/2020] [Indexed: 01/11/2023] Open
Abstract
Rhodopsin is mislocalized to the inner segment plasma membrane (IS PM) in various blinding disorders including autosomal-dominant retinitis pigmentosa caused by class I rhodopsin mutations. In these disorders, rhodopsin-laden microvesicles are secreted into the extracellular milieu by afflicted photoreceptor cells. Using a Xenopus laevis model expressing class I mutant rhodopsin or Na+/K+-ATPase (NKA) fused to Dendra2, we fluorescently labeled the microvesicles and found retinal pigment epithelial (RPE) cells are capable of engulfing microvesicles containing rhodopsin. A unique sorting mechanism allows class I mutant rhodopsin, but not NKA, to be packaged into the microvesicles. Under normal physiological conditions, NKA is not shed as microvesicles to the extracellular space, but is degraded intracellularly. Those studies provide novel insights into protein homeostasis in the photoreceptor IS PM.
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Affiliation(s)
- Philip Ropelewski
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
| | - Yoshikazu Imanishi
- Department of Pharmacology, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106
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10
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ASCOT identifies key regulators of neuronal subtype-specific splicing. Nat Commun 2020; 11:137. [PMID: 31919425 PMCID: PMC6952364 DOI: 10.1038/s41467-019-14020-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2019] [Accepted: 12/12/2019] [Indexed: 12/22/2022] Open
Abstract
Public archives of next-generation sequencing data are growing exponentially, but the difficulty of marshaling this data has led to its underutilization by scientists. Here, we present ASCOT, a resource that uses annotation-free methods to rapidly analyze and visualize splice variants across tens of thousands of bulk and single-cell data sets in the public archive. To demonstrate the utility of ASCOT, we identify novel cell type-specific alternative exons across the nervous system and leverage ENCODE and GTEx data sets to study the unique splicing of photoreceptors. We find that PTBP1 knockdown and MSI1 and PCBP2 overexpression are sufficient to activate many photoreceptor-specific exons in HepG2 liver cancer cells. This work demonstrates how large-scale analysis of public RNA-Seq data sets can yield key insights into cell type-specific control of RNA splicing and underscores the importance of considering both annotated and unannotated splicing events.
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Disrupted Plasma Membrane Protein Homeostasis in a Xenopus Laevis Model of Retinitis Pigmentosa. J Neurosci 2019; 39:5581-5593. [PMID: 31061086 DOI: 10.1523/jneurosci.3025-18.2019] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [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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Abstract
Rods and cones are retinal photoreceptor neurons required for our visual sensation. Because of their highly polarized structures and well-characterized processes of G protein-coupled receptor-mediated phototransduction signaling, these photoreceptors have been excellent models for studying the compartmentalization and sorting of proteins. Rods and cones have a modified ciliary compartment called the outer segment (OS) as well as non-OS compartments. The distinct membrane protein compositions between OS and non-OS compartments suggest that the OS is separated from the rest of the cellular compartments by multiple barriers or gates that are selectively permissive to specific cargoes. This review discusses the mechanisms of protein sorting and compartmentalization in photoreceptor neurons. Proper sorting and compartmentalization of membrane proteins are required for signal transduction and transmission. This review also discusses the roles of compartmentalized signaling, which is compromised in various retinal ciliopathies.
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Affiliation(s)
- Yoshikazu Imanishi
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106, USA;
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13
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Identification of the retinoschisin-binding site on the retinal Na/K-ATPase. PLoS One 2019; 14:e0216320. [PMID: 31048931 PMCID: PMC6497308 DOI: 10.1371/journal.pone.0216320] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2018] [Accepted: 04/19/2019] [Indexed: 01/11/2023] Open
Abstract
X-linked juvenile retinoschisis (XLRS) is a hereditary retinal dystrophy, caused by mutations in the RS1 gene which encodes the secreted protein retinoschisin. In recent years, several molecules have been proposed to interact with retinoschisin, including the retinal Na/K-ATPase, L-voltage gated Ca2+ channels, and specific sugars. We recently showed that the retinal Na/K-ATPase consisting of subunits ATP1A3 and ATP1B2 is essential for anchoring retinoschisin to plasma membranes and identified the glycosylated ATP1B2 subunit as the direct interaction partner for retinoschisin. We now aimed to precisely map the retinoschisin binding domain(s) in ATP1B2. In general, retinoschisin binding was not affected after selective elimination of individual glycosylation sites via site-directed mutagenesis as well as after full enzymatic deglycosylation of ATP1B2. Applying the interface prediction tool PresCont, two putative protein-protein interaction patches (“patch I” and “patch II”) consisting each of four hydrophobic amino acid stretches on the ATP1B2 surface were identified. These were consecutively altered by site-directed mutagenesis. Functional assays with the ATP1B2 patch mutants identified patch II and, specifically, the associated amino acid at position 240 (harboring a threonine in ATP1B2) as crucial for retinoschisin binding to ATP1B2. These and previous results led us to suggest an induced-fit binding mechanism for the interaction between retinoschisin and the Na/K-ATPase, which is dependent on threonine 240 in ATP1B2 allowing the accommodation of hyperflexible retinoschisin spikes by the associated protein-protein interaction patch on ATP1B2.
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Heymann JB, Vijayasarathy C, Huang RK, Dearborn AD, Sieving PA, Steven AC. Cryo-EM of retinoschisin branched networks suggests an intercellular adhesive scaffold in the retina. J Cell Biol 2019; 218:1027-1038. [PMID: 30630865 PMCID: PMC6400569 DOI: 10.1083/jcb.201806148] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Revised: 11/06/2018] [Accepted: 12/07/2018] [Indexed: 12/26/2022] Open
Abstract
Mutations in the essential retinal protein retinoschisin (RS1) cause a form of macular degeneration. Heymann et al. use cryo-EM to show that RS1 assembles into branched networks that may play a stabilizing role in maintaining the integrity of the retina. Mutations in the retinal protein retinoschisin (RS1) cause progressive loss of vision in young males, a form of macular degeneration called X-linked retinoschisis (XLRS). We previously solved the structure of RS1, a 16-mer composed of paired back-to-back octameric rings. Here, we show by cryo–electron microscopy that RS1 16-mers can assemble into extensive branched networks. We classified the different configurations, finding four types of interaction between the RS1 molecules. The predominant configuration is a linear strand with a wavy appearance. Three less frequent types constitute the branch points of the network. In all cases, the “spikes” around the periphery of the double rings are involved in these interactions. In the linear strand, a loop (usually referred to as spike 1) occurs on both sides of the interface between neighboring molecules. Mutations in this loop suppress secretion, indicating the possibility of intracellular higher-order assembly. These observations suggest that branched networks of RS1 may play a stabilizing role in maintaining the integrity of the retina.
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Affiliation(s)
- J Bernard Heymann
- Laboratory for Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD
| | - Camasamudram Vijayasarathy
- Section on Translational Research for Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD
| | - Rick K Huang
- Cryo-Electron Microscopy Facility, Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA
| | - Altaira D Dearborn
- Laboratory for Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD
| | - Paul A Sieving
- Section on Translational Research for Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD.,National Eye Institute, National Institutes of Health, Bethesda, MD
| | - Alasdair C Steven
- Laboratory for Structural Biology Research, National Institute of Arthritis and Musculoskeletal and Skin Diseases, National Institutes of Health, Bethesda, MD
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The Natural History of Congenital X-Linked Retinoschisis and Conversion between Phenotypes over Time. ACTA ACUST UNITED AC 2019; 3:77-82. [DOI: 10.1016/j.oret.2018.08.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Revised: 08/15/2018] [Accepted: 08/16/2018] [Indexed: 11/19/2022]
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16
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Plössl K, Schmid V, Straub K, Schmid C, Ammon M, Merkl R, Weber BHF, Friedrich U. Pathomechanism of mutated and secreted retinoschisin in X-linked juvenile retinoschisis. Exp Eye Res 2018; 177:23-34. [PMID: 30040949 DOI: 10.1016/j.exer.2018.07.021] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Revised: 07/20/2018] [Accepted: 07/20/2018] [Indexed: 01/08/2023]
Abstract
Mutations in the RS1 gene encoding retinoschisin cause X-linked juvenile retinoschisis (XLRS), a hereditary retinal dystrophy in males. While most of the XLRS associated mutations strongly interfere with cellular secretion, this is not true for mutants RS1-F108C, -R141G, -R141H, -R182C, -H207Q and -R209H. Native retinoschisin builds double-octamers and binds to retinal membranes, interacting with the retinal Na/K-ATPase. Functionally, it regulates MAP kinase signaling and Na/K-ATPase localization, and hampers photoreceptor degeneration. In this study, we investigated the capacity of the retinoschisin mutants still secreted extracellularly to fulfil these tasks. We addressed secretion and oligomerization of the heterologously expressed mutants as well as their binding to recombinant retinal Na/K-ATPases and murine retinoschisin-deficient (Rs1h-/Y) retinal and non-retinal explants. This has refined the categorization of secreted retinoschisin mutants: (i) no octamerization, unspecific membrane binding (RS1-F108C and -R182C), (ii) double-octamerization but no membrane binding (RS1-R141H), and (iii) double-octamerization and unspecific membrane binding (RS1-R141G, -H207Q, and -R209H). Notably, selected mutants of all categories (RS1-F108C, -R141H, and -R209H) failed to regulate retinal MAP kinase signaling and Na/K-ATPase localization in Rs1h-/Y retinal explants, and could not attenuate photoreceptor degeneration. Bioinformatic modeling of the secreted mutants depicted prominent alterations in the spatial and temporal conformation of a substructure called "spike 3" and its vicinity, implying a crucial role of this substructure for binding capacity and specificity. Taken together, our data point to a pathomechanism for secreted retinoschisin mutants, specifically to disturbances of the retinoschisin interface accompanied by unphysiological membrane interactions and impaired regulatory functions.
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Affiliation(s)
- Karolina Plössl
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
| | - Verena Schmid
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
| | - Kristina Straub
- Institute of Biophysics and Physical Biochemistry, University of Regensburg, Universitätsstraße 31, 93040 Regensburg, Germany
| | - Carina Schmid
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
| | - Mirjam Ammon
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
| | - Rainer Merkl
- Institute of Biophysics and Physical Biochemistry, University of Regensburg, Universitätsstraße 31, 93040 Regensburg, Germany
| | - Bernhard H F Weber
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany
| | - Ulrike Friedrich
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauss-Allee 11, 93053 Regensburg, Germany.
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Abalem MF, Musch DC, Birch DG, Pennesi ME, Heckenlively JR, Jayasundera T. Diurnal variations of foveoschisis by optical coherence tomography in patients with RS1 X-linked juvenile retinoschisis. Ophthalmic Genet 2018; 39:437-442. [PMID: 29902095 DOI: 10.1080/13816810.2018.1466340] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
BACKGROUND To evaluate diurnal variations in macular schisis cavities in patients with X-linked juvenile retinoschisis (XLRS) with pathogenic variants in the RS1 gene using spectral-domain optical coherence tomography (SD-OCT). METHODS Three consecutive patients with a clinical diagnosis of XLRS and pathogenic variants in the RS1, treated with carbonic anhydrase inhibitors (CAIs). Observational procedures: SD-OCT scans of the macula were acquired at 9 a.m., 1 p.m., and 4 p.m. within 24 h. RESULTS All patients demonstrated increased measures of central foveal thickness in the morning with gradual decrease through the day (9-43%). Major changes were observed between 9 a.m. and 1 p.m. in the central foveal thickness. CONCLUSION The central foveal thickness varies during daytime hours in patients with XLRS. This finding may explain the inconsistent and heterogeneous responses to treatment with CAIs and necessitate standardization of measurement times in treatment trials for XLRS as well as in the routine ophthalmic evaluation of these patients.
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Affiliation(s)
- Maria Fernanda Abalem
- a Department of Ophthalmology and Visual Sciences, Kellogg Eye Center , University of Michigan Medical School , Ann Arbor , MI , USA.,b Department of Ophthalmology and Otolaryngology , University of Sao Paulo Medical School , Sao Paulo , Brazil
| | - David C Musch
- a Department of Ophthalmology and Visual Sciences, Kellogg Eye Center , University of Michigan Medical School , Ann Arbor , MI , USA.,c Department of Epidemiology , University of Michigan School of Public Health , Ann Arbor , MI , USA
| | - David G Birch
- d Retina Foundation of the Southwest , Dallas , TX , USA
| | - Mark E Pennesi
- e Casey Eye Institute , Oregon Health & Science University , Portland , OR , USA
| | - John R Heckenlively
- a Department of Ophthalmology and Visual Sciences, Kellogg Eye Center , University of Michigan Medical School , Ann Arbor , MI , USA
| | - Thiran Jayasundera
- a Department of Ophthalmology and Visual Sciences, Kellogg Eye Center , University of Michigan Medical School , Ann Arbor , MI , USA
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A SINE Insertion in ATP1B2 in Belgian Shepherd Dogs Affected by Spongy Degeneration with Cerebellar Ataxia (SDCA2). G3-GENES GENOMES GENETICS 2017; 7:2729-2737. [PMID: 28620085 PMCID: PMC5555477 DOI: 10.1534/g3.117.043018] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Spongy degeneration with cerebellar ataxia (SDCA) is a genetically heterogeneous neurodegenerative disorder with autosomal recessive inheritance in Malinois dogs, one of the four varieties of the Belgian Shepherd breed. Using a combined linkage and homozygosity mapping approach we identified an ∼10.6 Mb critical interval on chromosome 5 in a Malinois family with four puppies affected by cerebellar dysfunction. Visual inspection of the 10.6 Mb interval in whole-genome sequencing data from one affected puppy revealed a 227 bp SINE insertion into the ATP1B2 gene encoding the β2 subunit of the Na+/K+-ATPase holoenzyme (ATP1B2:c.130_131insLT796559.1:g.50_276). The SINE insertion caused aberrant RNA splicing. Immunohistochemistry suggested a reduction of ATP1B2 protein expression in the central nervous system of affected puppies. Atp1b2 knockout mice had previously been reported to show clinical and neurohistopathological findings similar to the affected Malinois puppies. Therefore, we consider ATP1B2:c.130_131ins227 the most likely candidate causative variant for a second subtype of SDCA in Malinois dogs, which we propose to term spongy degeneration with cerebellar ataxia subtype 2 (SDCA2). Our study further elucidates the genetic and phenotypic complexity underlying cerebellar dysfunction in Malinois dogs and provides the basis for a genetic test to eradicate one specific neurodegenerative disease from the breeding population in Malinois and the other varieties of the Belgian Shepherd breed. ATP1B2 thus represents another candidate gene for human inherited cerebellar ataxias, and SDCA2-affected Malinois puppies may serve as a naturally occurring animal model for this disorder.
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Plössl K, Royer M, Bernklau S, Tavraz NN, Friedrich T, Wild J, Weber BHF, Friedrich U. Retinoschisin is linked to retinal Na/K-ATPase signaling and localization. Mol Biol Cell 2017; 28:2178-2189. [PMID: 28615319 PMCID: PMC5531734 DOI: 10.1091/mbc.e17-01-0064] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2017] [Revised: 06/02/2017] [Accepted: 06/06/2017] [Indexed: 01/30/2023] Open
Abstract
Retinoschisin binds to the extracellular domain of Na/K-ATPase subunit β2. Retinoschisin inhibits Na/K-ATPase–associated signaling cascades and affects Na/K-ATPase localization. The retinoschisin-Na/K-ATPase complex overlaps with signaling mediators. Defective Na/K-ATPase signaling by retinoschisin deficiency may promote retinal dystrophy. Mutations in the RS1 gene cause X-linked juvenile retinoschisis (XLRS), a hereditary retinal dystrophy. We recently showed that retinoschisin, the protein encoded by RS1, regulates ERK signaling and apoptosis in retinal cells. In this study, we explored an influence of retinoschisin on the functionality of the Na/K-ATPase, its interaction partner at retinal plasma membranes. We show that retinoschisin binding requires the β2-subunit of the Na/K-ATPase, whereas the α-subunit is exchangeable. Our investigations revealed no effect of retinoschisin on Na/K-ATPase–mediated ATP hydrolysis and ion transport. However, we identified an influence of retinoschisin on Na/K-ATPase–regulated signaling cascades and Na/K-ATPase localization. In addition to the known ERK deactivation, retinoschisin treatment of retinoschisin-deficient (Rs1h-/Y) murine retinal explants decreased activation of Src, an initial transmitter in Na/K-ATPase signal transduction, and of Ca2+ signaling marker Camk2. Immunohistochemistry on murine retinae revealed an overlap of the retinoschisin–Na/K-ATPase complex with proteins involved in Na/K-ATPase signaling, such as caveolin, phospholipase C, Src, and the IP3 receptor. Finally, retinoschisin treatment altered Na/K-ATPase localization in photoreceptors of Rs1h-/Y retinae. Taken together, our results suggest a regulatory effect of retinoschisin on Na/K-ATPase signaling and localization, whereas Na/K-ATPase-dysregulation caused by retinoschisin deficiency could represent an initial step in XLRS pathogenesis.
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Affiliation(s)
- Karolina Plössl
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
| | - Melanie Royer
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
| | - Sarah Bernklau
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
| | - Neslihan N Tavraz
- Institute of Chemistry, Technical University of Berlin, 10623 Berlin, Germany
| | - Thomas Friedrich
- Institute of Chemistry, Technical University of Berlin, 10623 Berlin, Germany
| | - Jens Wild
- Institute of Clinical Microbiology and Hygiene, University Hospital of Regensburg, University of Regensburg, 93053 Regensburg, Germany
| | - Bernhard H F Weber
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
| | - Ulrike Friedrich
- Institute of Human Genetics, University of Regensburg, 93053 Regensburg, Germany
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Plössl K, Weber BHF, Friedrich U. The X-linked juvenile retinoschisis protein retinoschisin is a novel regulator of mitogen-activated protein kinase signalling and apoptosis in the retina. J Cell Mol Med 2016; 21:768-780. [PMID: 27995734 PMCID: PMC5345684 DOI: 10.1111/jcmm.13019] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 09/26/2016] [Indexed: 02/01/2023] Open
Abstract
X-linked juvenile retinoschisis (XLRS) is a hereditary retinal dystrophy in young males, caused by mutations in the RS1 gene. The function of the encoded protein, termed retinoschisin, and the molecular mechanisms underlying XLRS pathogenesis are still unresolved, although a direct interaction partner of the secreted retinoschisin, the retinal Na/K-ATPase, was recently identified. Earlier gene expression studies in retinoschisin-deficient (Rs1h-/Y ) mice provided a first indication of pathological up-regulation of mitogen-activated protein (MAP) kinase signalling in disease pathogenesis. To further investigate the role for retinoschisin in MAP kinase regulation, we exposed Y-79 cells and murine Rs1h-/Y retinae to recombinant retinoschisin and the XLRS-associated mutant RS1-C59S. Although normal retinoschisin stably bound to retinal cells, RS1-C59S exhibited a strongly reduced binding affinity. Simultaneously, exposure to normal retinoschisin significantly reduced phosphorylation of C-RAF and MAP kinases ERK1/2 in Y-79 cells and murine Rs1h-/Y retinae. Expression of MAP kinase target genes C-FOS and EGR1 was also down-regulated in both model systems. Finally, retinoschisin treatment decreased pro-apoptotic BAX-2 transcript levels in Y-79 cells and Rs1h-/Y retinae. Upon retinoschisin treatment, these cells showed increased resistance against apoptosis, reflected by decreased caspase-3 activity (in Y-79 cells) and increased photoreceptor survival (in Rs1h-/Y retinal explants). RS1-C59S did not influence C-RAF or ERK1/2 activation, C-FOS or EGR1 expression, or apoptosis. Our data imply that retinoschisin is a novel regulator of MAP kinase signalling and exerts an anti-apoptotic effect on retinal cells. We therefore discuss that disturbances of MAP kinase signalling by retinoschisin deficiency could be an initial step in XLRS pathogenesis.
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Affiliation(s)
- Karolina Plössl
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Bernhard H F Weber
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Ulrike Friedrich
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
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Paired octamer rings of retinoschisin suggest a junctional model for cell-cell adhesion in the retina. Proc Natl Acad Sci U S A 2016; 113:5287-92. [PMID: 27114531 DOI: 10.1073/pnas.1519048113] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Retinoschisin (RS1) is involved in cell-cell junctions in the retina, but is unique among known cell-adhesion proteins in that it is a soluble secreted protein. Loss-of-function mutations in RS1 lead to early vision impairment in young males, called X-linked retinoschisis. The disease is characterized by separation of inner retinal layers and disruption of synaptic signaling. Using cryo-electron microscopy, we report the structure at 4.1 Å, revealing double octamer rings not observed before. Each subunit is composed of a discoidin domain and a small N-terminal (RS1) domain. The RS1 domains occupy the centers of the rings, but are not required for ring formation and are less clearly defined, suggesting mobility. We determined the structure of the discoidin rings, consistent with known intramolecular and intermolecular disulfides. The interfaces internal to and between rings feature residues implicated in X-linked retinoschisis, indicating the importance of correct assembly. Based on this structure, we propose that RS1 couples neighboring membranes together through octamer-octamer contacts, perhaps modulated by interactions with other membrane components.
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Glycoprotein nonmetastatic melanoma protein B extracellular fragment shows neuroprotective effects and activates the PI3K/Akt and MEK/ERK pathways via the Na+/K+-ATPase. Sci Rep 2016; 6:23241. [PMID: 26988030 PMCID: PMC4796790 DOI: 10.1038/srep23241] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 03/02/2016] [Indexed: 12/23/2022] Open
Abstract
Glycoprotein nonmetastatic melanoma protein B (GPNMB) plays important roles in various types of cancer and amyotrophic lateral sclerosis (ALS). The details of GPNMB function and its interacting protein have not been clarified. Therefore, to identify GPNMB binding partners on the cell membrane, we used membrane protein library/BLOTCHIP-MS technology, which enables us to analyze all cell membrane proteins as binding partners of the GPNMB extracellular fragment. As a result of a comprehensive search, we identified the alpha subunits of Na(+)/K(+)-ATPase (NKA) as a possible binding partner. We confirmed the interaction between the GPNMB extracellular fragment and NKA by immunoprecipitation and immunostaining in NSC-34 cells. Indeed, endogenous GPNMB extracellular fragment bound to and colocalized with NKA alpha subunits. Furthermore, exogenous GPNMB extracellular fragment, i.e., human recombinant GPNMB, also bound to and colocalized with NKA alpha subunits. Additionally, we found that the GPNMB extracellular fragment had neuroprotective effects and activated the phosphoinositide 3-kinase (PI3K)/Akt and mitogen-activated protein kinase (MAPK)-extracellular signal-regulated kinase (ERK) kinase (MEK)/ERK pathways via NKA. These findings indicated that NKA may act as a novel "receptor" for the GPNMB extracellular fragment, offering additional molecular targets for the treatment of GPNMB-related diseases, including various types of cancer and ALS.
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Apaolaza PS, Del Pozo-Rodríguez A, Solinís MA, Rodríguez JM, Friedrich U, Torrecilla J, Weber BHF, Rodríguez-Gascón A. Structural recovery of the retina in a retinoschisin-deficient mouse after gene replacement therapy by solid lipid nanoparticles. Biomaterials 2016; 90:40-9. [PMID: 26986855 DOI: 10.1016/j.biomaterials.2016.03.004] [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: 12/22/2015] [Revised: 02/29/2016] [Accepted: 03/02/2016] [Indexed: 11/26/2022]
Abstract
X-linked juvenile retinoschisis (XLRS) is a retinal degenerative disorder caused by mutations in the RS1 gene encoding a protein termed retinoschisin. The disease is an excellent candidate for gene replacement therapy as the majority of mutations have been shown to lead to a complete deficiency of the secreted protein in the retinal structures. In this work, we have studied the ability of non-viral vectors based on solid lipid nanoparticles (SLN) to induce the expression of retinoschisin in photoreceptors (PR) after intravitreal administration to Rs1h-deficient mice. We designed two vectors prepared with SLN, protamine, and dextran (DX) or hyaluronic acid (HA), bearing a plasmid containing the human RS1 gene under the control of the murin opsin promoter (mOPS). In vitro, the nanocarriers were able to induce the expression of retinoschisin in a PR cell line. After injection into the murine vitreous, the formulation prepared with HA induced a higher transfection level in PR than the formulation prepared with DX. Moreover, the level of retinoschisin in the inner nuclear layer (INL), where bipolar cells are located, was also higher. Two weeks after vitreal administration into Rs1h-deficient mice, both formulations showed significant improvement of the retinal structure by inducing a decrease of cavities and PR loss, and an increase of retinal and outer nuclear layer (ONL) thickness. HA-SLN resulted in a significant higher increase in the thickness of both retina and ONL, which can be explained by the higher transfection level of PR. In conclusion, we have shown the structural improvement of the retina of Rs1h-deficient mice with PR specific expression of the RS1 gene driven by the specific promoter mOPS, after successful delivery via SLN-based non-viral vectors.
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Affiliation(s)
- P S Apaolaza
- Pharmacokinetic, Nanotechnology and Gene Therapy Group (PharmaNanoGene), Faculty of Pharmacy, Centro de investigación Lascaray ikergunea, University of the Basque Country UPV/EHU, Paseo de la Universidad, 7, 01006 Vitoria-Gasteiz, Spain
| | - A Del Pozo-Rodríguez
- Pharmacokinetic, Nanotechnology and Gene Therapy Group (PharmaNanoGene), Faculty of Pharmacy, Centro de investigación Lascaray ikergunea, University of the Basque Country UPV/EHU, Paseo de la Universidad, 7, 01006 Vitoria-Gasteiz, Spain
| | - M A Solinís
- Pharmacokinetic, Nanotechnology and Gene Therapy Group (PharmaNanoGene), Faculty of Pharmacy, Centro de investigación Lascaray ikergunea, University of the Basque Country UPV/EHU, Paseo de la Universidad, 7, 01006 Vitoria-Gasteiz, Spain
| | - J M Rodríguez
- Physiology Laboratory, Faculty of Pharmacy, University of the Basque Country UPV/EHU, Paseo de la Universidad, 7, 01006 Vitoria-Gasteiz, Spain
| | - U Friedrich
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauß-Allee 11, D-93053 Regensburg, Germany
| | - J Torrecilla
- Pharmacokinetic, Nanotechnology and Gene Therapy Group (PharmaNanoGene), Faculty of Pharmacy, Centro de investigación Lascaray ikergunea, University of the Basque Country UPV/EHU, Paseo de la Universidad, 7, 01006 Vitoria-Gasteiz, Spain
| | - B H F Weber
- Institute of Human Genetics, University of Regensburg, Franz-Josef-Strauß-Allee 11, D-93053 Regensburg, Germany
| | - A Rodríguez-Gascón
- Pharmacokinetic, Nanotechnology and Gene Therapy Group (PharmaNanoGene), Faculty of Pharmacy, Centro de investigación Lascaray ikergunea, University of the Basque Country UPV/EHU, Paseo de la Universidad, 7, 01006 Vitoria-Gasteiz, Spain.
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Zhao L, Chen Y, Bajaj AO, Eblimit A, Xu M, Soens ZT, Wang F, Ge Z, Jung SY, He F, Li Y, Wensel TG, Qin J, Chen R. Integrative subcellular proteomic analysis allows accurate prediction of human disease-causing genes. Genome Res 2016; 26:660-9. [PMID: 26912414 PMCID: PMC4864458 DOI: 10.1101/gr.198911.115] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Accepted: 02/19/2016] [Indexed: 12/04/2022]
Abstract
Proteomic profiling on subcellular fractions provides invaluable information regarding both protein abundance and subcellular localization. When integrated with other data sets, it can greatly enhance our ability to predict gene function genome-wide. In this study, we performed a comprehensive proteomic analysis on the light-sensing compartment of photoreceptors called the outer segment (OS). By comparing with the protein profile obtained from the retina tissue depleted of OS, an enrichment score for each protein is calculated to quantify protein subcellular localization, and 84% accuracy is achieved compared with experimental data. By integrating the protein OS enrichment score, the protein abundance, and the retina transcriptome, the probability of a gene playing an essential function in photoreceptor cells is derived with high specificity and sensitivity. As a result, a list of genes that will likely result in human retinal disease when mutated was identified and validated by previous literature and/or animal model studies. Therefore, this new methodology demonstrates the synergy of combining subcellular fractionation proteomics with other omics data sets and is generally applicable to other tissues and diseases.
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Affiliation(s)
- Li Zhao
- Structural and Computational Biology and Molecular Biophysics Graduate Program, Baylor College of Medicine, Houston, Texas 77030, USA; Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Yiyun Chen
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Amol Onkar Bajaj
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Aiden Eblimit
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Mingchu Xu
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Zachry T Soens
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Feng Wang
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Zhongqi Ge
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Sung Yun Jung
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Feng He
- Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Yumei Li
- Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Theodore G Wensel
- Structural and Computational Biology and Molecular Biophysics Graduate Program, Baylor College of Medicine, Houston, Texas 77030, USA; Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Jun Qin
- Structural and Computational Biology and Molecular Biophysics Graduate Program, Baylor College of Medicine, Houston, Texas 77030, USA; Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA
| | - Rui Chen
- Structural and Computational Biology and Molecular Biophysics Graduate Program, Baylor College of Medicine, Houston, Texas 77030, USA; Human Genome Sequencing Center, Baylor College of Medicine, Houston, Texas 77030, USA; Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, Texas 77030, USA
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25
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Bush M, Setiaputra D, Yip CK, Molday RS. Cog-Wheel Octameric Structure of RS1, the Discoidin Domain Containing Retinal Protein Associated with X-Linked Retinoschisis. PLoS One 2016; 11:e0147653. [PMID: 26812435 PMCID: PMC4728063 DOI: 10.1371/journal.pone.0147653] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2015] [Accepted: 01/06/2016] [Indexed: 11/19/2022] Open
Abstract
RS1, also known as retinoschisin, is a disulphide-linked, discoidin domain containing homo-oligomeric protein that plays a crucial role in maintaining the cellular and synaptic organization of the retina. This is highlighted by the finding that over 130 mutations in RS1 cause X-linked retinoschisis, a retinal degenerative disease characterized by the splitting of the retinal cell layers, disruption of the photoreceptor-bipolar synapses, degeneration of photoreceptors, and severe loss in central vision. In this study, we investigated the arrangement of the RS1 subunits within the oligomer complex using single particle electron microscopy. RS1 was seen as two stacked rings with each ring displaying a symmetrical cog wheel-like structure with eight teeth or projections corresponding to the RS1 subunits. Three dimensional reconstruction and molecular modelling indicated that the discoidin domain, the principal functional unit of RS1, projects outward, and the Rs1 domain and C-terminal segment containing intermolecular disulphide bonds are present in the inner ring to form the core octameric structure. These studies provide a basis for further understanding the role of the novel core RS1 octameric complex in retinal cell biology and X-linked retinoschisis.
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Affiliation(s)
- Martin Bush
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Dheva Setiaputra
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Calvin K. Yip
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Robert S. Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
- * E-mail:
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26
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Apaolaza P, del Pozo-Rodríguez A, Torrecilla J, Rodríguez-Gascón A, Rodríguez J, Friedrich U, Weber B, Solinís M. Solid lipid nanoparticle-based vectors intended for the treatment of X-linked juvenile retinoschisis by gene therapy: In vivo approaches in Rs1h-deficient mouse model. J Control Release 2015; 217:273-83. [DOI: 10.1016/j.jconrel.2015.09.033] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Revised: 09/16/2015] [Accepted: 09/18/2015] [Indexed: 11/25/2022]
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27
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Laird JG, Pan Y, Modestou M, Yamaguchi DM, Song H, Sokolov M, Baker SA. Identification of a VxP Targeting Signal in the Flagellar Na+ /K+ -ATPase. Traffic 2015; 16:1239-53. [PMID: 26373354 DOI: 10.1111/tra.12332] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Revised: 09/11/2015] [Accepted: 09/11/2015] [Indexed: 12/15/2022]
Abstract
Na(+) /K(+) -ATPase (NKA) participates in setting electrochemical gradients, cardiotonic steroid signaling and cellular adhesion. Distinct isoforms of NKA are found in different tissues and subcellular localization patterns. For example, NKA α1 is widely expressed, NKA α3 is enriched in neurons and NKA α4 is a testes-specific isoform found in sperm flagella. In some tissues, ankyrin, a key component of the membrane cytoskeleton, can regulate the trafficking of NKA. In the retina, NKA and ankyrin-B are expressed in multiple cell types and immunostaining for each is striking in the synaptic layers. Labeling for NKA is also prominent along the inner segment plasma membrane (ISPM) of photoreceptors. NKA co-immunoprecipitates with ankyrin-B, but on a subcellular level colocalization of these two proteins varies dependent on the cell type. We used transgenic Xenopus laevis tadpoles to evaluate the subcellular trafficking of NKA in photoreceptors. GFP-NKA α3 and α1 are localized to the ISPM, but α4 is localized to outer segments (OSs). We identified a VxP motif responsible for the OS targeting by using a series of chimeric and mutant NKA constructs. This motif is similar to previously identified ciliary targeting motifs. Given the structural similarities between OSs and flagella, our findings shed light on the subcellular targeting of this testes-specific NKA isoform.
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Affiliation(s)
- Joseph G Laird
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Yuan Pan
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA.,Current address: Department of Neurology, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Modestos Modestou
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - David M Yamaguchi
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
| | - Hongman Song
- Department of Ophthalmology, West Virginia University School of Medicine and West Virginia University Eye Institute, Morgantown, WV, 26506, USA.,Current address: Section for Translational Research in Retina & Macular Degeneration, National Institute on Deafness and Other Communication Disorders, NIH, Bethesda, MD, 20892, USA
| | - Maxim Sokolov
- Department of Ophthalmology, West Virginia University School of Medicine and West Virginia University Eye Institute, Morgantown, WV, 26506, USA
| | - Sheila A Baker
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, IA, 52242, USA
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28
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Manousaki T, Tsakogiannis A, Lagnel J, Sarropoulou E, Xiang JZ, Papandroulakis N, Mylonas CC, Tsigenopoulos CS. The sex-specific transcriptome of the hermaphrodite sparid sharpsnout seabream (Diplodus puntazzo). BMC Genomics 2014; 15:655. [PMID: 25099474 PMCID: PMC4133083 DOI: 10.1186/1471-2164-15-655] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Accepted: 07/30/2014] [Indexed: 12/13/2022] Open
Abstract
Background Teleosts are characterized by a remarkable breadth of sexual mechanisms including various forms of hermaphroditism. Sparidae is a fish family exhibiting gonochorism or hermaphroditism even in closely related species. The sparid Diplodus puntazzo (sharpsnout seabream), exhibits rudimentary hermaphroditism characterized by intersexual immature gonads but single-sex mature ones. Apart from the intriguing reproductive biology, it is economically important with a continuously growing aquaculture in the Mediterranean Sea, but limited available genetic resources. Our aim was to characterize the expressed transcriptome of gonads and brains through RNA-Sequencing and explore the properties of genes that exhibit sex-biased expression profiles. Results Through RNA-Sequencing we obtained an assembled transcriptome of 82,331 loci. The expression analysis uncovered remarkable differences between male and female gonads, while male and female brains were almost identical. Focused search for known targets of sex determination and differentiation in vertebrates built the sex-specific expression profile of sharpsnout seabream. Finally, a thorough genetic marker discovery pipeline led to the retrieval of 85,189 SNPs and 29,076 microsatellites enriching the available genetic markers for this species. Conclusions We obtained a nearly complete source of transcriptomic sequence as well as marker information for sharpsnout seabream, laying the ground for understanding the complex process of sex differentiation of this economically valuable species. The genes involved include known candidates from other vertebrate species, suggesting a conservation of the toolkit between gonochorists and hermaphrodites. Electronic supplementary material The online version of this article (doi:10.1186/1471-2164-15-655) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | | | | | - Costas S Tsigenopoulos
- Institute of Marine Biology, Biotechnology and Aquaculture (I,M,B,B,C,), Hellenic Centre for Marine Research (H,C,M,R,), Heraklion, Greece.
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29
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Byrne LC, Oztürk BE, Lee T, Fortuny C, Visel M, Dalkara D, Schaffer DV, Flannery JG. Retinoschisin gene therapy in photoreceptors, Müller glia or all retinal cells in the Rs1h-/- mouse. Gene Ther 2014; 21:585-92. [PMID: 24694538 PMCID: PMC4047144 DOI: 10.1038/gt.2014.31] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Revised: 01/28/2014] [Accepted: 02/25/2014] [Indexed: 01/21/2023]
Abstract
X-linked retinoschisis, a disease characterized by splitting of the retina, is caused by mutations in the retinoschisin gene, which encodes a secreted cell adhesion protein. Currently, there is no effective treatment for retinoschisis, though viral vector-mediated gene replacement therapies offer promise. We used intravitreal delivery of three different AAV vectors to target delivery of the RS1 gene to Müller glia, photoreceptors, or multiple cell types throughout the retina. Müller glia radially span the entire retina, are accessible from the vitreous, and remain intact throughout progression of the disease. However, photoreceptors, not glia, normally secrete retinoschisin. We compared the efficacy of rescue mediated by retinoschisin secretion from these specific subtypes of retinal cells in the Rs1h−/− mouse model of retinoschisis. Our results indicate that all three vectors deliver the RS1 gene, and that several cell types can secrete retinoschisin, leading to transport of the protein across the retina. The greatest long-term rescue was observed when photoreceptors produce retinoschisin. Similar rescue was observed with photoreceptor-specific or generalized expression, though photoreceptor secretion may contribute to rescue in the latter case. These results collectively point to the importance of cell targeting and appropriate vector choice in the success of retinal gene therapies.
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Affiliation(s)
- L C Byrne
- 1] Department of Molecular and Cellular Biology, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA [2] Department of Chemical and Biomolecular Engineering, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA [3] Department of Bioengineering, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA
| | - B E Oztürk
- Department of Molecular and Cellular Biology, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA
| | - T Lee
- Department of Molecular and Cellular Biology, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA
| | - C Fortuny
- 1] Department of Molecular and Cellular Biology, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA [2] Department of Vision Science, The University of California, Berkeley, CA, USA
| | - M Visel
- Department of Molecular and Cellular Biology, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA
| | - D Dalkara
- 1] Department of Molecular and Cellular Biology, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA [2] Department of Chemical and Biomolecular Engineering, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA [3] Department of Bioengineering, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA
| | - D V Schaffer
- 1] Department of Chemical and Biomolecular Engineering, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA [2] Department of Bioengineering, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA
| | - J G Flannery
- 1] Department of Molecular and Cellular Biology, The Helen Wills Neuroscience Institute, The University of California, Berkeley, CA, USA [2] Department of Vision Science, The University of California, Berkeley, CA, USA
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30
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Demos MK, van Karnebeek CD, Ross CJ, Adam S, Shen Y, Zhan SH, Shyr C, Horvath G, Suri M, Fryer A, Jones SJ, Friedman JM. A novel recurrent mutation in ATP1A3 causes CAPOS syndrome. Orphanet J Rare Dis 2014; 9:15. [PMID: 24468074 PMCID: PMC3937150 DOI: 10.1186/1750-1172-9-15] [Citation(s) in RCA: 139] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2013] [Accepted: 01/16/2014] [Indexed: 11/10/2022] Open
Abstract
Background We undertook genetic analysis of three affected families to identify the cause of dominantly-inherited CAPOS (cerebellar ataxia, areflexia, pes cavus, optic atrophy and sensorineural hearing loss) syndrome. Methods We used whole-exome sequencing to analyze two families affected with CAPOS syndrome, including the original family reported in 1996, and Sanger sequencing to assess familial segregation of rare variants identified in the probands and in a third, apparently unrelated family with CAPOS syndrome. Results We found an identical heterozygous missense mutation, c.2452G > A (p.(Glu818Lys)), in the Na+/K+ ATPase α3(ATP1A3) gene in the proband and his affected sister and mother, but not in either unaffected maternal grandparent, in the first family. The same mutation was also identified in the proband and three other affected members of the second family and in all three affected members of the third family. This mutation was not found in more than 3600 chromosomes from unaffected individuals. Conclusion Other mutations in ATP1A3 have previously been demonstrated to cause rapid-onset dystonia-parkinsonism (also called dystonia-12) or alternating hemiplegia of childhood. This study shows that an allelic mutation in ATP1A3 produces CAPOS syndrome.
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Affiliation(s)
- Michelle K Demos
- Division of Neurology, Department of Pediatrics, University of British Columbia and BC Children's Hospital, Vancouver, BC V6H 3N1, Canada.
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Abstract
Photoreceptors are exquisitely adapted to transform light stimuli into electrical signals that modulate neurotransmitter release. These cells are organized into several compartments including the unique outer segment (OS). Its whole function is to absorb light and transduce this signal into a change of membrane potential. Another compartment is the inner segment where much of metabolism and regulation of membrane potential takes place and that connects the OS and synapse. The synapse is the compartment where changes in membrane potentials are relayed to other neurons in the retina via release of neurotransmitter. The composition of the plasma membrane surrounding these compartments varies to accommodate their specific functions. In this chapter, we discuss the organization of the plasma membrane emphasizing the protein composition of each region as it relates to visual signaling. We also point out examples where mutations in these proteins cause visual impairment.
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Affiliation(s)
- Sheila A Baker
- Department of Biochemistry, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA.
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32
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Wu JW, Liu HL. In silico investigation of the disease-associated retinoschisin C110Y and C219G mutants. J Biomol Struct Dyn 2012; 29:937-59. [PMID: 22292953 DOI: 10.1080/07391102.2012.10507420] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The juvenile X-linked retinoschisis (XLRS) is a retinal disease caused by mutations in the secretory protein, retinoschisin (RS1). Majority of the disease is resulted from single point mutations on the RS1 discoidin domain with cysteine mutations being related to some of the more severe cases of XLRS. Previous studies have indicated that two mutations (C110Y and C219G), which involve cysteines that form intramolecular disulfide bonds in the native discoidin domain, resulted in different oligomerization states of the proteins and did not correlate with the degree of protein stability as calculated by the change in folding free energy. Through homology modeling, bioinformatics predictions, molecular dynamics (MD) and docking simulations, we attempt to investigate the effects of these two mutations on the structure of the RS1 discoidin domain in relevance to the discrepancy found between structural stability and aggregation propensity. Based on our findings, this discrepancy can be explained by the ability of C110Y mutant to establish suitable modules for initiating amorphous aggregation and to expand the aggregating mass through predominantly hydrophobic interactions. The low capability of C219G mutant to oligomerize, on the other hand, may be due to its greater structural instability and lesser hydrophobic tendency, two properties that may be unsupportive of aggregation. The results, altogether, indicate that aggregation propensity in the RS1 C110Y mutant is dependent upon the formation of suitable aggregating substrates for propagation of aggregation and not directly related to or determined by overall structural instability. As for the wildtype protein, the binding specificity of the spikes for biological function and the formation of octameric structure are contributed by important loop interactions, as well as evolved structural and sequence-based properties that prevent aggregation.
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Affiliation(s)
- Josephine W Wu
- Institute of Biotechnology, National Taipei University of Technology, Taipei 10608, Taiwan
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Molday RS, Kellner U, Weber BHF. X-linked juvenile retinoschisis: clinical diagnosis, genetic analysis, and molecular mechanisms. Prog Retin Eye Res 2012; 31:195-212. [PMID: 22245536 PMCID: PMC3334421 DOI: 10.1016/j.preteyeres.2011.12.002] [Citation(s) in RCA: 208] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2011] [Revised: 12/16/2011] [Accepted: 12/19/2011] [Indexed: 01/07/2023]
Abstract
X-linked juvenile retinoschisis (XLRS, MIM 312700) is a common early onset macular degeneration in males characterized by mild to severe loss in visual acuity, splitting of retinal layers, and a reduction in the b-wave of the electroretinogram (ERG). The RS1 gene (MIM 300839) associated with the disease encodes retinoschisin, a 224 amino acid protein containing a discoidin domain as the major structural unit, an N-terminal cleavable signal sequence, and regions responsible for subunit oligomerization. Retinoschisin is secreted from retinal cells as a disulphide-linked homo-octameric complex which binds to the surface of photoreceptors and bipolar cells to help maintain the integrity of the retina. Over 190 disease-causing mutations in the RS1 gene are known with most mutations occurring as non-synonymous changes in the discoidin domain. Cell expression studies have shown that disease-associated missense mutations in the discoidin domain cause severe protein misfolding and retention in the endoplasmic reticulum, mutations in the signal sequence result in aberrant protein synthesis, and mutations in regions flanking the discoidin domain cause defective disulphide-linked subunit assembly, all of which produce a non-functional protein. Knockout mice deficient in retinoschisin have been generated and shown to display most of the characteristic features found in XLRS patients. Recombinant adeno-associated virus (rAAV) mediated delivery of the normal RS1 gene to the retina of young knockout mice result in long-term retinoschisin expression and rescue of retinal structure and function providing a 'proof of concept' that gene therapy may be an effective treatment for XLRS.
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Affiliation(s)
- Robert S Molday
- Department of Biochemistry and Molecular Biology, Centre of Macular Research, University of British Columbia, 2350 Health Sciences Mall, Vancouver, B.C. V6T 1Z3, Canada.
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The dynamic architecture of photoreceptor ribbon synapses: cytoskeletal, extracellular matrix, and intramembrane proteins. Vis Neurosci 2012; 28:453-71. [PMID: 22192503 DOI: 10.1017/s0952523811000356] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Rod and cone photoreceptors possess ribbon synapses that assist in the transmission of graded light responses to second-order bipolar and horizontal cells of the vertebrate retina. Proper functioning of the synapse requires the juxtaposition of presynaptic release sites immediately adjacent to postsynaptic receptors. In this review, we focus on the synaptic, cytoskeletal, and extracellular matrix proteins that help to organize photoreceptor ribbon synapses in the outer plexiform layer. We examine the proteins that foster the clustering of release proteins, calcium channels, and synaptic vesicles in the presynaptic terminals of photoreceptors adjacent to their postsynaptic contacts. Although many proteins interact with one another in the presynaptic terminal and synaptic cleft, these protein-protein interactions do not create a static and immutable structure. Instead, photoreceptor ribbon synapses are remarkably dynamic, exhibiting structural changes on both rapid and slow time scales.
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