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van der Veen I, Heredero Berzal A, Koster C, ten Asbroek ALMA, Bergen AA, Boon CJF. The Road towards Gene Therapy for X-Linked Juvenile Retinoschisis: A Systematic Review of Preclinical Gene Therapy in Cell-Based and Rodent Models of XLRS. Int J Mol Sci 2024; 25:1267. [PMID: 38279267 PMCID: PMC10816913 DOI: 10.3390/ijms25021267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2023] [Revised: 01/12/2024] [Accepted: 01/17/2024] [Indexed: 01/28/2024] Open
Abstract
X-linked juvenile retinoschisis (XLRS) is an early-onset progressive inherited retinopathy affecting males. It is characterized by abnormalities in the macula, with formation of cystoid retinal cavities, frequently accompanied by splitting of the retinal layers, impaired synaptic transmission of visual signals, and associated loss of visual acuity. XLRS is caused by loss-of-function mutations in the retinoschisin gene located on the X chromosome (RS1, MIM 30083). While proof-of-concept studies for gene augmentation therapy have been promising in in vitro and rodent models, clinical trials in XLRS patients have not been successful thus far. We performed a systematic literature investigation using search strings related to XLRS and gene therapy in in vivo and in vitro models. Three rounds of screening (title/abstract, full text and qualitative) were performed by two independent reviewers until consensus was reached. Characteristics related to study design and intervention were extracted from all studies. Results were divided into studies using (1) viral and (2) non-viral therapies. All in vivo rodent studies that used viral vectors were assessed for quality and risk of bias using the SYRCLE's risk-of-bias tool. Studies using alternative and non-viral delivery techniques, either in vivo or in vitro, were extracted and reviewed qualitatively, given the diverse and dispersed nature of the information. For in-depth analysis of in vivo studies using viral vectors, outcome data for optical coherence tomography (OCT), immunohistopathology and electroretinography (ERG) were extracted. Meta-analyses were performed on the effect of recombinant adeno-associated viral vector (AAV)-mediated gene augmentation therapies on a- and b-wave amplitude as well as the ratio between b- and a-wave amplitudes (b/a-ratio) extracted from ERG data. Subgroup analyses and meta-regression were performed for model, dose, age at injection, follow-up time point and delivery method. Between-study heterogeneity was assessed with a Chi-square test of homogeneity (I2). We identified 25 studies that target RS1 and met our search string. A total of 19 of these studies reported rodent viral methods in vivo. Six of the 25 studies used non-viral or alternative delivery methods, either in vitro or in vivo. Of these, five studies described non-viral methods and one study described an alternative delivery method. The 19 aforementioned in vivo studies were assessed for risk of bias and quality assessments and showed inconsistency in reporting. This resulted in an unclear risk of bias in most included studies. All 19 studies used AAVs to deliver intact human or murine RS1 in rodent models for XLRS. Meta-analyses of a-wave amplitude, b-wave amplitude, and b/a-ratio showed that, overall, AAV-mediated gene augmentation therapy significantly ameliorated the disease phenotype on these parameters. Subgroup analyses and meta-regression showed significant correlations between b-wave amplitude effect size and dose, although between-study heterogeneity was high. This systematic review reiterates the high potential for gene therapy in XLRS, while highlighting the importance of careful preclinical study design and reporting. The establishment of a systematic approach in these studies is essential to effectively translate this knowledge into novel and improved treatment alternatives.
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Affiliation(s)
- Isa van der Veen
- Department of Ophthalmology, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (I.v.d.V.); (A.H.B.); (C.K.); (A.A.B.)
- Department of Human Genetics, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands;
| | - Andrea Heredero Berzal
- Department of Ophthalmology, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (I.v.d.V.); (A.H.B.); (C.K.); (A.A.B.)
- Department of Human Genetics, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands;
| | - Céline Koster
- Department of Ophthalmology, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (I.v.d.V.); (A.H.B.); (C.K.); (A.A.B.)
- Department of Human Genetics, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands;
| | - Anneloor L. M. A. ten Asbroek
- Department of Human Genetics, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands;
| | - Arthur A. Bergen
- Department of Ophthalmology, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (I.v.d.V.); (A.H.B.); (C.K.); (A.A.B.)
- Department of Human Genetics, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands;
| | - Camiel J. F. Boon
- Department of Ophthalmology, Amsterdam UMC, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands; (I.v.d.V.); (A.H.B.); (C.K.); (A.A.B.)
- Department of Ophthalmology, Leiden University Medical Center, Leiden University, Albinusdreef 2, 2333 ZA Leiden, The Netherlands
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Sengillo JD, Al-Khersan H, Rohowetz L, Shoji MK, Robles-Holmes H, Cruz NFSD, Negron CI, Yannuzzi NA, Patel NA, Berrocal AM. Retinal Detachments in Pediatric Patients With X-Linked Retinoschisis: Characteristics and Surgical Outcomes. Ophthalmic Surg Lasers Imaging Retina 2023; 54:574-579. [PMID: 37847161 DOI: 10.3928/23258160-20230920-01] [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: 10/18/2023]
Abstract
BACKGROUND AND OBJECTIVE Retinal detachments (RDs) are a complication of X-linked retinoschisis (XLRS) with a poor prognosis. This study aims to report outcomes of XLRS-RD repair in pediatric patients. MATERIALS AND METHODS The study is a retrospective analysis of pediatric patients undergoing vitreoretinal surgery for XLRS-RDs from 2000 to 2022. RESULTS Nine patients (11 eyes) met inclusion criteria. All patients were boys, with a mean age of 8 years. Most RDs arose inferiorly (64%). Seven (64%) detachments were macula-involving. Seven (64%) detachments were repaired with combined scleral buckling and vitrectomy, two (18%) detachments were repaired with vitrectomy alone, one (9%) detachment underwent a primary scleral buckling procedure, and one (9%) asymptomatic detachment with a pigment demarcation line was observed. Silicone oil was used in eight of nine (89%) eyes undergoing vitrectomy. Final visual acuity was 20/200 or better in eight (73%) eyes. One eye that underwent surgical intervention remained unattached at follow-up. CONCLUSION Surgical repair in patients with XLRSRDs was associated with successful reattachment, although visual prognosis varied. [Ophthalmic Surg Lasers Imaging Retina 2023;54:574-579.].
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Ambrosio L, Hansen RM, Kimia R, Fulton AB. Retinal Function in X-Linked Juvenile Retinoschisis. Invest Ophthalmol Vis Sci 2020; 60:4872-4881. [PMID: 31747688 DOI: 10.1167/iovs.19-27897] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To assess retinal function in young patients with X-linked juvenile retinoschisis (XLRS), a disorder that is known to alter ERG postreceptor retinal components and also possibly photoreceptor components. Methods ERG responses to full-field stimuli were recorded under scotopic and photopic conditions in 12 XLRS patients aged 1 to 15 (median 8) years. A- and b-wave amplitudes and implicit times were examined over a range of stimulus intensities. Rod and cone photoreceptor (SROD, RROD, SCONE, RCONE) and rod-driven postreceptor (log σ, VMAX) response parameters were calculated from the a- and b-waves. Data from XLRS patients were evaluated for significant change with age. Results A- and b-wave amplitudes were smaller in XLRS patients compared with controls under both scotopic and photopic conditions. Saturated photoresponse amplitude (RROD), postreceptor b-wave (log σ), and saturated b-wave amplitude (VMAX) were significantly lower in XLRS patients than in controls; SROD did not differ between the two groups. SCONE and RCONE values were normal. In XLRS patients, neither a- and b-wave amplitudes nor calculated parameters (SROD, RROD, log σ, VMAX,SCONE, and RCONE) changed with age. Conclusions In these young XLRS patients, RROD and a-wave amplitudes were significantly smaller than in controls. Thus, in addition to XLRS causing postreceptor dysfunction, an effect of XLRS on rod photoreceptors cannot be ignored.
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Affiliation(s)
- Lucia Ambrosio
- Department of Ophthalmology, Boston Children's Hospital & Harvard Medical School, Boston, Massachusetts, United States
| | - Ronald M Hansen
- Department of Ophthalmology, Boston Children's Hospital & Harvard Medical School, Boston, Massachusetts, United States
| | - Rotem Kimia
- Department of Ophthalmology, Boston Children's Hospital & Harvard Medical School, Boston, Massachusetts, United States
| | - Anne B Fulton
- Department of Ophthalmology, Boston Children's Hospital & Harvard Medical School, Boston, Massachusetts, United States
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Wide-Field Swept-Source OCT and Angiography in X-Linked Retinoschisis. ACTA ACUST UNITED AC 2019; 3:178-185. [DOI: 10.1016/j.oret.2018.09.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2018] [Revised: 08/28/2018] [Accepted: 09/10/2018] [Indexed: 11/17/2022]
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Shi L, Chang JYA, Yu F, Ko ML, Ko GYP. The Contribution of L-Type Ca v1.3 Channels to Retinal Light Responses. Front Mol Neurosci 2017; 10:394. [PMID: 29259539 PMCID: PMC5723326 DOI: 10.3389/fnmol.2017.00394] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Accepted: 11/10/2017] [Indexed: 01/28/2023] Open
Abstract
L-type voltage-gated calcium channels (LTCCs) regulate tonic neurotransmitter release from sensory neurons including retinal photoreceptors. There are three types of LTCCs (Cav1.2, Cav1.3, and Cav1.4) expressed in the retina. While Cav1.2 is expressed in all retinal cells including the Müller glia and neurons, Cav1.3 and Cav1.4 are expressed in the retinal neurons with Cav1.4 exclusively expressed in the photoreceptor synaptic terminals. Mutations in the gene encoding Cav1.4 cause incomplete X-linked congenital stationary night blindness in humans. Even though Cav1.3 is present in the photoreceptor inner segments and the synaptic terminals in various vertebrate species, its role in vision is unclear, since genetic alterations in Cav1.3 are not associated with severe vision impairment in humans or in Cav1.3-null (Cav1.3-/-) mice. However, a failure to regulate Cav1.3 was found in a mouse model of Usher syndrome, the most common cause of combined deafness and blindness in humans, indicating that Cav1.3 may contribute to retinal function. In this report, we combined physiological and morphological data to demonstrate the role of Cav1.3 in retinal physiology and function that has been undervalued thus far. Through ex vivo and in vivo electroretinogram (ERG) recordings and immunohistochemical staining, we found that Cav1.3 plays a role in retinal light responses and synaptic plasticity. Pharmacological inhibition of Cav1.3 decreased ex vivo ERG a- and b-wave amplitudes. In Cav1.3-/- mice, their dark-adapted ERG a-, b-wave, and oscillatory potential amplitudes were significantly dampened, and implicit times were delayed compared to the wild type (WT). Furthermore, the density of ribbon synapses was reduced in the outer plexiform layer of Cav1.3-/- mice retinas. Hence, Cav1.3 plays a more prominent role in retinal physiology and function than previously reported.
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Affiliation(s)
- Liheng Shi
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, United States
| | - Janet Ya-An Chang
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, United States
| | - Fei Yu
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, United States
| | - Michael L Ko
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, United States
| | - Gladys Y-P Ko
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX, United States.,Texas A&M Institute of Neuroscience, Texas A&M University, College Station, TX, United States
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Shi L, Ko ML, Ko GYP. Retinoschisin Facilitates the Function of L-Type Voltage-Gated Calcium Channels. Front Cell Neurosci 2017; 11:232. [PMID: 28848397 PMCID: PMC5550728 DOI: 10.3389/fncel.2017.00232] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2017] [Accepted: 07/25/2017] [Indexed: 11/18/2022] Open
Abstract
Modulation of ion channels by extracellular proteins plays critical roles in shaping synaptic plasticity. Retinoschisin (RS1) is an extracellular adhesive protein secreted from photoreceptors and bipolar cells, and it plays an important role during retinal development, as well as in maintaining the stability of retinal layers. RS1 is known to form homologous octamers and interact with molecules on the plasma membrane including phosphatidylserine, sodium-potassium exchanger complex, and L-type voltage-gated calcium channels (LTCCs). However, how this physical interaction between RS1 and ion channels might affect the channel gating properties is unclear. In retinal photoreceptors, two major LTCCs are Cav1.3 (α1D) and Cav1.4 (α1F) with distinct biophysical properties, functions and distributions. Cav1.3 is distributed from the inner segment (IS) to the synaptic terminal and is responsible for calcium influx to the photoreceptors and overall calcium homeostasis. Cav1.4 is only expressed at the synaptic terminal and is responsible for neurotransmitter release. Mutations of the gene encoding Cav1.4 cause X-linked incomplete congenital stationary night blindness type 2 (CSNB2), while null mutations of Cav1.3 cause a mild decrease of retinal light responses in mice. Even though RS1 is known to maintain retinal architecture, in this study, we present that RS1 interacts with both Cav1.3 and Cav1.4 and regulates their activations. RS1 was able to co-immunoprecipitate with Cav1.3 and Cav1.4 from porcine retinas, and it increased the LTCC currents and facilitated voltage-dependent activation in HEK cells co-transfected with RS1 and Cav1.3 or Cav1.4, thus providing evidence of a functional interaction between RS1 and LTCCs. The interaction between RS1 and Cav1.3 did not change the calcium-dependent inactivation of Cav1.3. In mice lacking RS1, the expression of Cav1.3 and Cav1.4 in the retina decreased, while in mice with Cav1.4 deletion, the retinal level of RS1 decreased. These results provide important evidence that RS1 is not only an adhesive protein promoting cell-cell adhesion, it is essential for anchoring other membrane proteins including ion channels and enhancing their function in the retina.
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Affiliation(s)
- Liheng Shi
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M UniversityCollege Station, TX, United States
| | - Michael L Ko
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M UniversityCollege Station, TX, United States
| | - Gladys Y-P Ko
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M UniversityCollege Station, TX, United States.,Texas A&M Institute for Neuroscience, Texas A&M UniversityCollege Station, TX, United States
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Ramsay EP, Collins RF, Owens TW, Siebert CA, Jones RPO, Wang T, Roseman AM, Baldock C. Structural analysis of X-linked retinoschisis mutations reveals distinct classes which differentially effect retinoschisin function. Hum Mol Genet 2017; 25:5311-5320. [PMID: 27798099 PMCID: PMC5418834 DOI: 10.1093/hmg/ddw345] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Accepted: 09/30/2016] [Indexed: 01/09/2023] Open
Abstract
Retinoschisin, an octameric retinal-specific protein, is essential for retinal architecture with mutations causing X-linked retinoschisis (XLRS), a monogenic form of macular degeneration. Most XLRS-associated mutations cause intracellular retention, however a subset are secreted as octamers and the cause of their pathology is ill-defined. Therefore, here we investigated the solution structure of the retinoschisin monomer and the impact of two XLRS-causing mutants using a combinatorial approach of biophysics and cryo-EM. The retinoschisin monomer has an elongated structure which persists in the octameric assembly. Retinoschisin forms a dimer of octamers with each octameric ring adopting a planar propeller structure. Comparison of the octamer with the hexadecamer structure indicated little conformational change in the retinoschisin octamer upon dimerization, suggesting that the octamer provides a stable interface for the construction of the hexadecamer. The H207Q XLRS-associated mutation was found in the interface between octamers and destabilized both monomeric and octameric retinoschisin. Octamer dimerization is consistent with the adhesive function of retinoschisin supporting interactions between retinal cell layers, so disassembly would prevent structural coupling between opposing membranes. In contrast, cryo-EM structural analysis of the R141H mutation at ∼4.2Å resolution was found to only cause a subtle conformational change in the propeller tips, potentially perturbing an interaction site. Together, these findings support distinct mechanisms of pathology for two classes of XLRS-associated mutations in the retinoschisin assembly.
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Affiliation(s)
- Ewan P Ramsay
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK.,School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Richard F Collins
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Thomas W Owens
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK.,School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - C Alistair Siebert
- Electron Bio-Imaging Centre, Diamond Light Source, Harwell Science and Innovation Research Campus, UK
| | - Richard P O Jones
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Tao Wang
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Alan M Roseman
- School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
| | - Clair Baldock
- Wellcome Trust Centre for Cell-Matrix Research, School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK.,School of Biological Sciences, Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK
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Bush RA, Zeng Y, Colosi P, Kjellstrom S, Hiriyanna S, Vijayasarathy C, Santos M, Li J, Wu Z, Sieving PA. Preclinical Dose-Escalation Study of Intravitreal AAV-RS1 Gene Therapy in a Mouse Model of X-linked Retinoschisis: Dose-Dependent Expression and Improved Retinal Structure and Function. Hum Gene Ther 2016; 27:376-89. [PMID: 27036983 DOI: 10.1089/hum.2015.142] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Gene therapy for inherited retinal diseases has been shown to ameliorate functional and structural defects in both animal models and in human clinical trials. X-linked retinoschisis (XLRS) is an early-age onset macular dystrophy resulting from loss of an extracellular matrix protein (RS1). In preparation for a human clinical gene therapy trial, we conducted a dose-range efficacy study of the clinical vector, a self-complementary AAV delivering a human retinoschisin (RS1) gene under control of the RS1 promoter and an interphotoreceptor binding protein enhancer (AAV8-scRS/IRBPhRS), in the retinoschisin knockout (Rs1-KO) mouse. The therapeutic vector at 1 × 10(6) to 2.5 × 10(9) (1E6-2.5E9) vector genomes (vg)/eye or vehicle was administered to one eye of 229 male Rs1-KO mice by intravitreal injection at 22 ± 3 days postnatal age (PN). Analysis of retinal function (dark-adapted electroretinogram, ERG), structure (cavities and outer nuclear layer thickness) by in vivo retinal imaging using optical coherence tomography, and retinal immunohistochemistry (IHC) for RS1 was done 3-4 months and/or 6-9 months postinjection (PI). RS1 IHC staining was dose dependent across doses ≥1E7 vg/eye, and the threshold for significant improvement in all measures of retinal structure and function was 1E8 vg/eye. Higher doses, however, did not produce additional improvement. At all doses showing efficacy, RS1 staining in Rs1-KO mouse was less than that in wild-type mice. Improvement in the ERG and RS1 staining was unchanged or greater at 6-9 months than at 3-4 months PI. This study demonstrates that vitreal administration of AAV8 scRS/IRBPhRS produces significant improvement in retinal structure and function in the mouse model of XLRS over a vector dose range that can be extended to a human trial. It indicates that a fully normal level of RS1 expression is not necessary for a therapeutic effect.
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Affiliation(s)
- Ronald A Bush
- 1 National Institute on Deafness and Other Communication Disorders, National Institutes of Health , Bethesda, Maryland
| | - Yong Zeng
- 1 National Institute on Deafness and Other Communication Disorders, National Institutes of Health , Bethesda, Maryland
| | - Peter Colosi
- 2 National Eye Institute, National Institutes of Health , Bethesda, Maryland
| | - Sten Kjellstrom
- 1 National Institute on Deafness and Other Communication Disorders, National Institutes of Health , Bethesda, Maryland.,3 Department of Ophthalmology, Lund University , Lund, Sweden
| | - Suja Hiriyanna
- 2 National Eye Institute, National Institutes of Health , Bethesda, Maryland
| | - Camasamudram Vijayasarathy
- 1 National Institute on Deafness and Other Communication Disorders, National Institutes of Health , Bethesda, Maryland
| | - Maria Santos
- 2 National Eye Institute, National Institutes of Health , Bethesda, Maryland
| | - Jinbo Li
- 1 National Institute on Deafness and Other Communication Disorders, National Institutes of Health , Bethesda, Maryland
| | - Zhijian Wu
- 2 National Eye Institute, National Institutes of Health , Bethesda, Maryland
| | - Paul A Sieving
- 1 National Institute on Deafness and Other Communication Disorders, National Institutes of Health , Bethesda, Maryland.,2 National Eye Institute, National Institutes of Health , Bethesda, Maryland
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Bush RA, Wei LL, Sieving PA. Convergence of Human Genetics and Animal Studies: Gene Therapy for X-Linked Retinoschisis. Cold Spring Harb Perspect Med 2015; 5:a017368. [PMID: 26101206 DOI: 10.1101/cshperspect.a017368] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Retinoschisis is an X-linked recessive genetic disease that leads to vision loss in males. X-linked retinoschisis (XLRS) typically affects young males; however, progressive vision loss continues throughout life. Although discovered in 1898 by Haas in two brothers, the underlying biology leading to blindness has become apparent only in the last 15 years with the advancement of human genetic analyses, generation of XLRS animal models, and the development of ocular monitoring methods such as the electroretinogram and optical coherence tomography. It is now recognized that retinoschisis results from cyst formations within the retinal layers that interrupt normal visual neurosignaling and compromise structural integrity. Mutations in the human retinoschisin gene have been correlated with disease severity of the human XLRS phenotype. Introduction of a normal human retinoschisin cDNA into retinoschisin knockout mice restores retinal structure and improves neural function, providing proof-of-concept that gene replacement therapy is a plausible treatment for XLRS.
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Affiliation(s)
- Ronald A Bush
- National Institute on Deafness and Other Communication Disorders, Bethesda, Maryland 20892
| | - Lisa L Wei
- National Eye Institute, Bethesda, Maryland 20892
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Huang Y, Mei L, Gui B, Su W, Liang D, Wu L, Pan Q. A novel deletion mutation in RS1 gene caused X-linked juvenile retinoschisis in a Chinese family. Eye (Lond) 2014; 28:1364-9. [PMID: 25168411 DOI: 10.1038/eye.2014.196] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2014] [Accepted: 06/26/2014] [Indexed: 11/09/2022] Open
Abstract
PURPOSE X-linked juvenile retinoschisis (XLRS), a leading cause of juvenile macular degeneration, is characterized by a spoke-wheel pattern in the macular region of the retina and splitting of the neurosensory retina. This study aimed to identify the underlying genetic defect in a Chinese family with XLRS. METHODS The proband underwent complete ophthalmic examinations, including fundus examination, fundus autofluorescence, and optical coherence tomography. DNA extracted from proband and his younger brother was screened for mutations in RS1 gene. The detected RS1 mutation was tested in all available family members and 200 healthy controls. RESULTS Reduced visual acuity, spoke-wheel pattern at the fovea, and split retina were observed in the proband. A novel frameshift mutation c.206-207delTG in the RS1 gene, leading to a truncated protein (p.L69fs16X), was identified in the proband and his younger brother. This mutation was not found in any unaffected member or in the healthy controls. The mother of the proband was hemizygous for this mutant allele. CONCLUSIONS We identified a novel causative mutation of RS1 in a Chinese family with XLRS. This finding expands the mutation spectrum of RS1 and provides evidence for a phenotype-genotype study in XLRS.
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Affiliation(s)
- Y Huang
- State Key Laboratory of Medical Genetics, Xiangya Hospital, Central South University, Changsha, China
| | - L Mei
- State Key Laboratory of Medical Genetics, Xiangya Hospital, Central South University, Changsha, China
| | - B Gui
- State Key Laboratory of Medical Genetics, Xiangya Hospital, Central South University, Changsha, China
| | - W Su
- State Key Laboratory of Medical Genetics, Xiangya Hospital, Central South University, Changsha, China
| | - D Liang
- State Key Laboratory of Medical Genetics, Xiangya Hospital, Central South University, Changsha, China
| | - L Wu
- State Key Laboratory of Medical Genetics, Xiangya Hospital, Central South University, Changsha, China
| | - Q Pan
- State Key Laboratory of Medical Genetics, Xiangya Hospital, Central South University, Changsha, China
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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: 219] [Impact Index Per Article: 18.3] [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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Duncan JL, Ratnam K, Birch DG, Sundquist SM, Lucero AS, Zhang Y, Meltzer M, Smaoui N, Roorda A. Abnormal cone structure in foveal schisis cavities in X-linked retinoschisis from mutations in exon 6 of the RS1 gene. Invest Ophthalmol Vis Sci 2011; 52:9614-23. [PMID: 22110067 DOI: 10.1167/iovs.11-8600] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To evaluate macular cone structure in patients with X-linked retinoschisis (XLRS) caused by mutations in exon 6 of the RS1 gene. METHODS High-resolution macular images were obtained with adaptive optics scanning laser ophthalmoscopy (AOSLO) and spectral domain optical coherence tomography (SD-OCT) in two patients with XLRS and 27 age-similar healthy subjects. Retinal structure was correlated with best-corrected visual acuity, kinetic and static perimetry, fundus-guided microperimetry, full-field electroretinography (ERG), and multifocal ERG. The six coding exons and the flanking intronic regions of the RS1 gene were sequenced in each patient. RESULTS Two unrelated males, ages 14 and 29, with visual acuity ranging from 20/32 to 20/63, had macular schisis with small relative central scotomas in each eye. The mixed scotopic ERG b-wave was reduced more than the a-wave. SD-OCT showed schisis cavities in the outer and inner nuclear and plexiform layers. Cone spacing was increased within the largest foveal schisis cavities but was normal elsewhere. In each patient, a mutation in exon 6 of the RS1 gene was identified and was predicted to change the amino acid sequence in the discoidin domain of the retinoschisin protein. CONCLUSIONS AOSLO images of two patients with molecularly characterized XLRS revealed increased cone spacing and abnormal packing in the macula of each patient, but cone coverage and function were near normal outside the central foveal schisis cavities. Although cone density is reduced, the preservation of wave-guiding cones at the fovea and eccentric macular regions has prognostic and therapeutic implications for XLRS patients with foveal schisis. (Clinical Trials.gov number, NCT00254605.).
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Affiliation(s)
- Jacque L Duncan
- Department of Ophthalmology, University of California at San Francisco, San Francisco, California 94143, USA.
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14
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Bowles K, Cukras C, Turriff A, Sergeev Y, Vitale S, Bush RA, Sieving PA. X-linked retinoschisis: RS1 mutation severity and age affect the ERG phenotype in a cohort of 68 affected male subjects. Invest Ophthalmol Vis Sci 2011; 52:9250-6. [PMID: 22039241 DOI: 10.1167/iovs.11-8115] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE To assess the effect of age and RS1 mutation on the phenotype of X-linked retinoschisis (XLRS) subjects using the clinical electroretinogram (ERG) in a cross-sectional analysis. METHODS Sixty-eight XLRS males 4.5 to 55 years of age underwent genotyping, and the retinoschisis (RS1) mutations were classified as less severe (27 subjects) or more severe (41 subjects) based on the putative impact on the protein. ERG parameters of retinal function were analyzed by putative mutation severity with age as a continuous variable. RESULTS The a-wave amplitude remained greater than the lower limit of normal (mean, -2 SD) for 72% of XLRS males and correlated with neither age nor mutation class. However, b-wave and b/a-ratio amplitudes were significantly lower in the more severe than in the less severe mutation groups and in older than in younger subjects. Subjects up to 10 years of age with more severe RS1 mutations had significantly greater b-wave amplitudes and faster a-wave trough implicit times than older subjects in this group. CONCLUSIONS RS1 mutation putative severity and age both had significant effects on retinal function in XLRS only in the severe mutation group, as judged by ERG analysis of the b-wave amplitude and the b/a-ratio, whereas the a-wave amplitude remained normal in most. A new observation was that increasing age (limited to those aged 55 and younger) caused a significant delay in XLRS b-wave onset (i.e., a-wave implicit time), even for those who retained considerable b-wave amplitudes. The delayed b-wave onset suggested that dysfunction of the photoreceptor synapse or of bipolar cells increases with age of XLRS subjects.
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Affiliation(s)
- Kristen Bowles
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, Bethesda, Maryland 20892, USA
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Farber DB, Theendakara VP, Akhmedov NB, Saghizadeh M. ZBED4, a novel retinal protein expressed in cones and Müller cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 664:79-87. [PMID: 20238005 DOI: 10.1007/978-1-4419-1399-9_10] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
To identify genes expressed in cone photoreceptors, we previously carried out subtractive hybridization and microarrays of retinal mRNAs from normal and cd (cone degeneration) dogs. One of the isolated genes encoded ZBED4, a novel protein that in human retina is localized to cone photoreceptors and glial Müller cells. ZBED4 is distributed between nuclear and cytoplasmic fractions of the retina and it readily forms homodimers, probably as a consequence of its hATC dimerization domain. In addition, the ZBED4 sequence has several domains that suggest it may function as part of a co-activator complex facilitating the activation of nuclear receptors and other factors (BED finger domains) or as a co-activator/co-repressor of nuclear hormone receptors (LXXLL motifs). We have identified several putative ZBED4-interacting proteins and one of them is precisely a co-repressor of the estrogen receptor alpha.
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Affiliation(s)
- Debora B Farber
- Jules Stein Eye Institute, UCLA School of Medicine, Los Angeles, CA 90095-7000, USA.
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16
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Kitamura E, Gribanova YE, Farber DB. Regulation of retinoschisin secretion in Weri-Rb1 cells by the F-actin and microtubule cytoskeleton. PLoS One 2011; 6:e20707. [PMID: 21738583 PMCID: PMC3124475 DOI: 10.1371/journal.pone.0020707] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2010] [Accepted: 05/10/2011] [Indexed: 11/19/2022] Open
Abstract
Retinoschisin is encoded by the gene responsible for X-linked retinoschisis (XLRS), an early onset macular degeneration that results in a splitting of the inner layers of the retina and severe loss in vision. Retinoschisin is predominantly expressed and secreted from photoreceptor cells as a homo-oligomer protein; it then associates with the surface of retinal cells and maintains the retina cellular architecture. Many missense mutations in the XLRS1 gene are known to cause intracellular retention of retinoschisin, indicating that the secretion process of the protein is a critical step for its normal function in the retina. However, the molecular mechanisms underlying retinoschisin's secretion remain to be fully elucidated. In this study, we investigated the role of the F-actin cytoskeleton in the secretion of retinoschisin by treating Weri-Rb1 cells, which are known to secrete retinoschisin, with cytochalasin D, jasplakinolide, Y-27632, and dibutyryl cGMP. Our results show that cytochalasin D and jasplakinolide inhibit retinoschisin secretion, whereas Y-27632 and dibutyryl cGMP enhance secretion causing F-actin alterations. We also demonstrate that high concentrations of taxol, which hyperpolymerizes microtubules, inhibit retinoschisin secretion. Our data suggest that retinoschisin secretion is regulated by the F-actin cytoskeleton, that cGMP or inhibition of ROCK alters F-actin structure enhancing the secretion, and that the microtubule cytoskeleton is also involved in this process.
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Affiliation(s)
- Eiko Kitamura
- Jules Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Yekaterina E. Gribanova
- Jules Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
| | - Debora B. Farber
- Jules Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, United States of America
- Molecular Biology Institute, University of California Los Angeles, Los Angeles, California, United States of America
- Brain Research Institute, University of California Los Angeles, Los Angeles, California, United States of America
- * E-mail:
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Fletcher EL, Jobling AI, Vessey KA, Luu C, Guymer RH, Baird PN. Animal models of retinal disease. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2011; 100:211-86. [PMID: 21377628 DOI: 10.1016/b978-0-12-384878-9.00006-6] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/02/2022]
Abstract
Diseases of the retina are the leading causes of blindness in the industrialized world. The recognition that animals develop retinal diseases with similar traits to humans has led to not only a dramatic improvement in our understanding of the pathogenesis of retinal disease but also provided a means for testing possible treatment regimes and successful gene therapy trials. With the advent of genetic and molecular biological tools, the association between specific gene mutations and retinal signs has been made. Animals carrying natural mutations usually in one gene now provide well-established models for a host of inherited retinal diseases, including retinitis pigmentosa, Leber congenital amaurosis, inherited macular degeneration, and optic nerve diseases. In addition, the development of transgenic technologies has provided a means by which to study the effects of these and novel induced mutations on retinal structure and function. Despite these advances, there is a paucity of suitable animal models for complex diseases, including age-related macular degeneration (AMD) and diabetic retinopathy, largely because these diseases are not caused by single gene defects, but involve complex genetics and/or exacerbation through environmental factors, epigenetic, or other modes of genetic influence. In this review, we outline in detail the available animal models for inherited retinal diseases and how this information has furthered our understanding of retinal diseases. We also examine how transgenic technologies have helped to develop our understanding of the role of isolated genes or pathways in complex diseases like AMD, diabetes, and glaucoma.
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Affiliation(s)
- Erica L Fletcher
- Department of Anatomy and Cell Biology, The University of Melbourne, Parkville, Victoria, Australia
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18
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Abstract
X-linked retinoschisis (XLRS) is a form of macular degeneration with a juvenile onset. This disease is caused by mutations in the retinoschisin (RS1) gene. The major clinical pathologies of this disease include splitting of the retina (schisis) and a loss in synaptic transmission. Human XLRS patients display a broad range in phenotypic severity, even among family members with the same mutation. This variation suggests the existence of genetic modifiers that may contribute to disease severity. Previously, we reported the identification of a modifier locus, named Mor1, which affects severity of schisis in a mouse model of XLRS (the Rs1tmgc1 mouse). Homozygosity for the protective AKR allele of Mor1 restores cell adhesion in Rs1tmgc1 mice. Here, we report our study to identify the Mor1 gene. Through collecting recombinant mice followed by progeny testing, we have localized Mor1 to a 4.4-Mb region on chromosome 7. In this genetic region, the AKR strain is known to carry a mutation in the tyrosinase (Tyr) gene. We observed that the schisis phenotype caused by the Rs1 mutation is rescued by a Tyr mutation in the C57BL/6J genetic background, strongly suggesting that Tyr is the Mor1 gene.
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19
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Abstract
Ion channels are the gatekeepers to neuronal excitability. Retinal neurons of vertebrates and invertebrates, neurons of the suprachiasmatic nucleus (SCN) of vertebrates, and pinealocytes of non-mammalian vertebrates display daily rhythms in their activities. The interlocking transcription-translation feedback loops with specific post-translational modulations within individual cells form the molecular clock, the basic mechanism that maintains the autonomic approximately 24-h rhythm. The molecular clock regulates downstream output signaling pathways that further modulate activities of various ion channels. Ultimately, it is the circadian regulation of ion channel properties that govern excitability and behavior output of these neurons. In this review, we focus on the recent development of research in circadian neurobiology mainly from 1980 forward. We will emphasize the circadian regulation of various ion channels, including cGMP-gated cation channels, various voltage-gated calcium and potassium channels, Na(+)/K(+)-ATPase, and a long-opening cation channel. The cellular mechanisms underlying the circadian regulation of these ion channels and their functions in various tissues and organisms will also be discussed. Despite the magnitude of chronobiological studies in recent years, the circadian regulation of ion channels still remains largely unexplored. Through more investigation and understanding of the circadian regulation of ion channels, the future development of therapeutic strategies for the treatment of sleep disorders, cardiovascular diseases, and other illnesses linked to circadian misalignment will benefit.
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Affiliation(s)
- Gladys Y-P Ko
- Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, Texas 77843-4458, USA.
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20
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Genead MA, Pasadhika S, Fishman GA. Retinal nerve fibre layer thickness analysis in X-linked retinoschisis using Fourier-domain OCT. Eye (Lond) 2009; 23:1019-27. [PMID: 19373267 PMCID: PMC2865150 DOI: 10.1038/eye.2009.53] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Purpose 19 To evaluate the presence of retinal nerve fiber layer (RNFL) defects in patients with XLRS using high speed, high resolution, Fourier domain OCT (FD-OCT). Methods Twenty four patients with XLRS seen by the authors were enrolled in the study. All patients underwent a complete eye examination. FD-OCT was performed using Optovue technology. A quadrant of the RNFL was considered to be thinned if at least 2 of the 4 segments in the quadrant were reduced in thickness. Results The average age of the 24 patients in the study was 28.8 years ± 14.7 years. Thinning of the RNFL in 1 quadrant was seen in 10 patients (41.7%), and thinning in 2 or more quadrants was seen in 8 patients (33.3%). Thinning in the inferior quadrant was most commonly seen and was observed in 12 patients (50%), followed by the temporal quadrant in 8 patients (33.3%), nasal quadrant in 4 patients (16.7%), and the superior quadrant in 4 patients (16.7%). Conclusions Among our 24 patients with XLRS, 15 patients (62.5%) showed a thinning of the RNFL in one or more quadrants in at least one eye and 9 patients (37.5%) in both eyes. The use of high speed, high resolution FD-OCT may be useful to determine the presence of possible changes in RNFL thickness in patients with XLRS. Reductions in RNFL thickness in such patients could be relevant in their selection for future therapeutic trials.
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Affiliation(s)
- M A Genead
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, USA
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21
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Shi L, Jian K, Ko ML, Trump D, Ko GYP. Retinoschisin, a new binding partner for L-type voltage-gated calcium channels in the retina. J Biol Chem 2008; 284:3966-75. [PMID: 19074145 DOI: 10.1074/jbc.m806333200] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The L-type voltage-gated calcium channels (L-VGCCs) are activated under high depolarization voltages. They are vital for diverse biological events, including cell excitability, differentiation, and synaptic transmission. In retinal photoreceptors, L-VGCCs are responsible for neurotransmitter release and are under circadian influences. However, the mechanism of L-VGCC regulation in photoreceptors is not fully understood. Here, we show that retinoschisin, a highly conserved extracellular protein, interacts with the L-VGCCalpha1D subunit and regulates its activities in a circadian manner. Mutations in the gene encoding retinoschisin (RS1) cause retinal disorganization that leads to early onset of macular degeneration. Since ion channel activities can be modulated through interactions with extracellular proteins, disruption of these interactions can alter physiology and be the root cause of disease states. Co-immunoprecipitation and mammalian two-hybrid assays showed that retinoschisin and the N-terminal fragment of the L-VGCCalpha1 subunit physically interacted with one another. The expression and secretion of retinoschisin are under circadian regulation with a peak at night and nadir during the day. Inhibition of L-type VGCCs decreased membrane-bound retinoschisin at night. Overexpression of a missense RS1 mutant gene, R141G, into chicken cone photoreceptors caused a decrease of L-type VGCC currents at night. Our findings demonstrate a novel bidirectional relationship between an ion channel and an extracellular protein; L-type VGCCs regulate the circadian rhythm of retinoschisin secretion, whereas secreted retinoschisin feeds back to regulate L-type VGCCs. Therefore, physical interactions between L-VGCCalpha1 subunits and retinoschisin play an important role in the membrane retention of L-VGCCalpha1 subunits and photoreceptor-bipolar synaptic transmission.
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Affiliation(s)
- Liheng Shi
- Department of Veterinary Integrative Biosciences, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, College Station, Texas 77843-4458, USA
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22
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Langmann T, Lai CCL, Weigelt K, Tam BM, Warneke-Wittstock R, Moritz OL, Weber BHF. CRX controls retinal expression of the X-linked juvenile retinoschisis (RS1) gene. Nucleic Acids Res 2008; 36:6523-34. [PMID: 18927113 PMCID: PMC2582616 DOI: 10.1093/nar/gkn737] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
X-linked juvenile retinoschisis is a heritable condition of the retina in males caused by mutations in the RS1 gene. Still, the cellular function and retina-specific expression of RS1 are poorly understood. To address the latter issue, we characterized the minimal promoter driving expression of RS1 in the retina. Binding site prediction, site-directed mutagenesis, and reporter assays suggest an essential role of two nearby cone-rod homeobox (CRX)-responsive elements (CRE) in the proximal −177/+32 RS1 promoter. Chromatin immunoprecipitation associates the RS1 promoter in vivo with CRX, the coactivators CBP, P300, GCN5 and acetylated histone H3. Transgenic Xenopus laevis expressing a green fluorescent protein (GFP) reporter under the control of RS1 promoter sequences show that the −177/+32 fragment drives GFP expression in photoreceptors and bipolar cells. Mutating either of the two conserved CRX binding sites results in strongly decreased RS1 expression. Despite the presence of sequence motifs in the promoter, NRL and NR2E3 appear not to be essential for RS1 expression. Together, our in vitro and in vivo results indicate that two CRE sites in the minimal RS1 promoter region control retinal RS1 expression and establish CRX as a key factor driving this expression.
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Affiliation(s)
- Thomas Langmann
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
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23
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Saleheen D, Ali A, Khanum S, Ozair MZ, Zaidi M, Sethi MJ, Khan N, Frossard P. Molecular analysis of the XLRS1 gene in 4 females affected with X-linked juvenile retinoschisis. Can J Ophthalmol 2008; 43:596-9. [DOI: 10.3129/i08-143] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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24
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Wong A, Merritt S, Butt AN, Williams A, Swaminathan R. Effect of Hypoxia on Circulating Levels of Retina-Specific Messenger RNA in Type 2 Diabetes Mellitus. Ann N Y Acad Sci 2008; 1137:243-52. [DOI: 10.1196/annals.1448.001] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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25
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Gerth C, Zawadzki RJ, Werner JS, Héon E. Retinal morphological changes of patients with X-linked retinoschisis evaluated by Fourier-domain optical coherence tomography. ACTA ACUST UNITED AC 2008; 126:807-11. [PMID: 18541843 DOI: 10.1001/archopht.126.6.807] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
Abstract
OBJECTIVE To investigate the retinal microstructure and lamination of patients affected with X-linked retinoschisis (XLRS) using high-resolution imaging modalities. METHODS Patients diagnosed as having XLRS underwent assessment. Visual function testing included visual acuity, color vision, and full-field electroretinography. We used a high-resolution Fourier-domain optical coherence tomography (FD-OCT) system (4.5-mum axial resolution; 9 frames/s; 1000 A-scans per frame) combined with a handheld scanner. Macular image evaluation included schisis localization and retinal layer integrity. RESULTS Six patients with XLRS and identified mutations in the XLRS1 gene underwent testing. Visual acuity ranged from 0.2 to 1.6 logMAR (logarithm of the minimum angle of resolution). Results of FD-OCT revealed foveal schisis extending from the outer to the inner plexiform layer in 4 of 6 patients. Bullous foveal schisis was associated with younger age. All patients showed extrafoveal schisis within the outer and inner nuclear and ganglion cell layer, alone or in combination. Photoreceptor outer and inner segment layers were disrupted and irregular in all patients. CONCLUSIONS Retinal dystrophy in XLRS is reflected by morphological changes within the inner and outer retinal layers. Disturbed foveal photoreceptor integrity was identified in all patients. Retinal layer abnormalities correlated with age but did not appear to correlate with visual acuity or genotypic variation.
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Affiliation(s)
- Christina Gerth
- Department of Ophthalmology and Vision Sciences, The Hospital for Sick Children, University of Toronto, Toronto, Ontario, Canada
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26
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Audo I, Robson AG, Holder GE, Moore AT. The negative ERG: clinical phenotypes and disease mechanisms of inner retinal dysfunction. Surv Ophthalmol 2008; 53:16-40. [PMID: 18191655 DOI: 10.1016/j.survophthal.2007.10.010] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Inner retinal dysfunction is encountered in a number of retinal disorders, either inherited or acquired, as a primary or predominant defect. Fundus examination is rarely diagnostic in these disorders, although some show characteristic features, and careful electrophysiological assessment of retinal function is needed for accurate diagnosis. The ERG in inner retinal dysfunction typically shows a negative waveform with a preserved a-wave and a selectively reduced b-wave. Advances in retinal physiology and molecular genetics have led to a greater understanding of the pathogenesis of these disorders. This review summarizes current knowledge on normal retinal physiology, the investigative techniques used and the range of clinical disorders in which there is predominantly inner retinal dysfunction.
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Vijayasarathy C, Takada Y, Zeng Y, Bush RA, Sieving PA. Organization and molecular interactions of retinoschisin in photoreceptors. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2008; 613:291-7. [PMID: 18188957 DOI: 10.1007/978-0-387-74904-4_34] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
Affiliation(s)
- Camasamudram Vijayasarathy
- Section for Translational Research in Retinal and Macular Degeneration, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA.
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Genetic modification of the schisis phenotype in a mouse model of X-linked retinoschisis. Genetics 2008; 178:1785-94. [PMID: 18245825 DOI: 10.1534/genetics.107.084905] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
X-linked retinoschisis (XLRS) is an inherited form of macular degeneration that is caused by mutations in the retinoschisin (RS1) gene. In addition to macular degeneration, other major characteristics of XLRS include splitting of the retina (schisis) and impaired synaptic transmission as indicated by a reduction in the electroretinogram b-wave. It has been known that patients carrying RS1 mutations show a broad range of phenotypic variability. Interestingly, phenotypic variation is observed even among family members with the same RS1 mutation, suggesting the existence of genetic or environmental factors that contribute to the severity of XLRS. However, in the human population, the cause of phenotypic variability and the contribution of genetic modifiers for this relatively rare disease are difficult to study and poorly understood. In this study, using a mouse model for XLRS, we show that genetic factors can contribute to the severity of the retinoschisis phenotype. We report evidence of a major genetic modifier of Rs1, which affects the disease severity in these animals. A quantitative trait locus (QTL), named modifier of Rs1 1 (Mor1), is mapped on chromosome (Chr) 7. When homozygous, the Mor1 allele from the inbred mouse strain AKR/J diminishes the severity of the schisis phenotype in Rs1(tmgc1)/Y male and Rs1(tmgc1)/Rs1(tmgc1) female mice. We also show that the penetrance of the disease phenotype is affected by additional genetic factor(s). Our study suggests that multiple genetic modifiers could potentially be responsible for the phenotypic variation in human XLRS.
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Molday LL, Wu WWH, Molday RS. Retinoschisin (RS1), the Protein Encoded by the X-linked Retinoschisis Gene, Is Anchored to the Surface of Retinal Photoreceptor and Bipolar Cells through Its Interactions with a Na/K ATPase-SARM1 Complex. J Biol Chem 2007; 282:32792-801. [PMID: 17804407 DOI: 10.1074/jbc.m706321200] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Retinoschisin or RS1 is a discoidin domain-containing protein encoded by the gene responsible for X-linked retinoschisis (XLRS), an early onset macular degeneration characterized by a splitting of the retina. Retinoschisin, expressed and secreted from photoreceptors and bipolar cells as a homo-octameric complex, associates with the surface of these cells where it serves to maintain the cellular organization of the retina and the photoreceptor-bipolar synaptic structure. To gain insight into the role of retinoschisin in retinal cell adhesion and the pathogenesis of XLRS, we have investigated membrane components in retinal extracts that interact with retinoschisin. Unlike the discoidin domain-containing blood coagulation proteins Factor V and Factor VIII, retinoschisin did not bind to phospholipids or retinal lipids reconstituted into unilamellar vesicles or immobilized on microtiter plates. Instead, co-immunoprecipitation studies together with mass spectrometric-based proteomics and Western blotting showed that retinoschisin is associated with a complex consisting of Na/K ATPase (alpha3, beta2 isoforms) and the sterile alpha and TIR motif-containing protein SARM1. Double labeling studies for immunofluorescence microscopy confirmed the co-localization of retinoschisin with Na/K ATPase and SARM1 in photoreceptors and bipolar cells of retina tissue. We conclude that retinoschisin binds to Na/K ATPase on photoreceptor and bipolar cells. This interaction may be part of a novel SARM1-mediated cell signaling pathway required for the maintenance of retinal cell organization and photoreceptor-bipolar synaptic structure.
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Affiliation(s)
- Laurie L Molday
- Department of Biochemistry & Molecular Biology, Centre for Macular Research, University of British Columbia, Vancouver, British Columbia, Canada.
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Kiedzierska A, Smietana K, Czepczynska H, Otlewski J. Structural similarities and functional diversity of eukaryotic discoidin-like domains. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2007; 1774:1069-78. [PMID: 17702679 DOI: 10.1016/j.bbapap.2007.07.007] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2007] [Revised: 07/02/2007] [Accepted: 07/17/2007] [Indexed: 12/15/2022]
Abstract
The discoidin domain is a approximately 150 amino acid motif common in both eukaryotic and prokaryotic proteins. It is found in a variety of extracellular, intracellular and transmembrane multidomain proteins characterized by a considerable functional diversity, mostly involved in developmental processes. The biological role of the domain depends on its interactions with different molecules, including growth factors, phospholipids and lipids, galactose or its derivatives, and collagen. The conservation of the motif, as well as the serious physiological consequences of discoidin domain disorders underscore the importance of the fold, while the ability to accommodate such an extraordinarily broad range of ligand molecules makes it a fascinating research target. In present review we characterize the distinctive features of discoidin domains and briefly outline the biological role of this module in various eukaryotic proteins.
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Affiliation(s)
- A Kiedzierska
- Faculty of Biotechnology, University of Wroclaw, Str. Tamka2, 50-137 Wroclaw, Poland
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31
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Johnson BA, Ikeda S, Pinto LH, Ikeda A. Reduced synaptic vesicle density and aberrant synaptic localization
caused by a splice site mutation in the Rs1h gene. Vis Neurosci 2007; 23:887-98. [PMID: 17266781 DOI: 10.1017/s0952523806230244] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2006] [Accepted: 09/04/2006] [Indexed: 01/30/2023]
Abstract
X-linked retinoschisis (XLRS) is a common form of inherited macular
degeneration caused by mutations in the RS1 gene. Whereas the
role of RS1 has been implicated in the synaptic structure as well
as layer organization in the retina, the pathological effect of a
defective RS1 gene on the synaptic interaction between
photoreceptor cells and second-order neurons has not been thoroughly
investigated. In this study, we perform a detailed characterization of the
retinal synaptic phenotypes caused by a splice site mutation in the murine
RS1 homolog (Rs1htmgc1). Electron
microscopic analysis showed that presynaptic terminals of photoreceptor
cells contain a lower areal density of synaptic vesicles in the
Rs1htmgc1 retina. Examination of the synaptic
interactions in the outer plexiform layer also revealed ectopic
localization of photoreceptor cell presynaptic markers and elongation of
neurites from postsynaptic neurons (bipolar and horizontal cells), which
are observed in other mouse models with defective photoreceptor cell
molecules. Consistent with these synaptic abnormalities, ERG analysis of
young Rs1htmgc1 mice revealed attenuation of
the b-wave with preservation of the a-wave. These results demonstrate that
RS1H has functional significance in the morphology and function of the
synapse between photoreceptors and second-order neurons. A developmental
study from postnatal day (P) 15 through P19 showed that synaptic
interactions form normally, and structural abnormalities occur after
completion of synaptic formation suggesting that RS1H is important for the
maintenance of this synaptic interaction. Thus,
Rs1htmgc1 mice may serve as a new genetic
model for human XLRS and other synaptic disorders.
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Affiliation(s)
- Britt A Johnson
- Department of Medical Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Iannaccone A, Mura M, Dyka FM, Ciccarelli ML, Yashar BM, Ayyagari R, Jablonski MM, Molday RS. An unusual X-linked retinoschisis phenotype and biochemical characterization of the W112C RS1 mutation. Vision Res 2006; 46:3845-52. [PMID: 16884758 DOI: 10.1016/j.visres.2006.06.011] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2006] [Revised: 06/02/2006] [Accepted: 06/09/2006] [Indexed: 10/24/2022]
Abstract
A 52-year-old subject harboring an RS1 gene W112C mutation presented with a prominent and asymmetric tapetal-like retinal sheen. Transient ERG responses were smaller and slower in the eye with the more extensive sheen, an association that, to our knowledge, had not been previously reported. An ON-pathway dysfunction explained the abnormalities of the transient but not those of the flicker ERGs. Although in vitro studies showed that the W112C mutant retinoschisin is present only in the cellular fraction and is not secreted, disease expression was remarkably mild, consistent with the notion of the existence of genetic and/or epigenetic disease modifiers.
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Affiliation(s)
- Alessandro Iannaccone
- Hamilton Eye Institute, Department of Ophthalmology, University of Tennessee Health Science Center, 930 Madison Avenue, Suite 731, Memphis, TN 38163, USA.
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Abstract
PURPOSE To determine the value of a topical carbonic anhydrase inhibitor for the treatment of foveal lesions in patients with X-linked retinoschisis (XLRS). METHODS Eight patients with XLRS and foveal cystic-appearing spaces by fundus examination and by optical coherence tomography (OCT) were treated with a topical form of carbonic anhydrase inhibitor. Changes in "foveal thickness" and "foveal zone thickness" were measured by OCT, and changes of best-corrected visual acuity were measured by Early Treatment Diabetic Retinopathy Study (ETDRS) charts. RESULTS Seven of eight patients treated with 2% dorzolamide had a noticeable reduction in foveal thickness as well as cystic-appearing spaces by OCT. This reduction was found in both eyes in four of these patients and in one eye in one patient after 1 month of treatment. After an additional 1 month to 2 months of the same treatment regimen, two additional patients also had a noticeable reduction in foveal thickness as well as cystic-appearing spaces. Of these seven patients who had an improvement shown by OCT with treatment, five also had improvement of their visual acuity by >or=7 letters in at least one eye on ETDRS charts. CONCLUSION The present study shows the efficacy of topical dorzolamide for treating foveal cystic-appearing lesions in patients with XLRS.
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Affiliation(s)
- Marsha A Apushkin
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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Molday LL, Min SH, Seeliger MW, Wu WWH, Dinculescu A, Timmers AM, Janssen A, Tonagel F, Hudl K, Weber BHF, Hauswirth WW, Molday RS. Disease mechanisms and gene therapy in a mouse model for X-linked retinoschisis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2006; 572:283-9. [PMID: 17249585 DOI: 10.1007/0-387-32442-9_39] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/13/2023]
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Apushkin MA, Fishman GA, Janowicz MJ. Correlation of optical coherence tomography findings with visual acuity and macular lesions in patients with X-linked retinoschisis. Ophthalmology 2005; 112:495-501. [PMID: 15745780 DOI: 10.1016/j.ophtha.2004.08.027] [Citation(s) in RCA: 60] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2004] [Accepted: 08/06/2004] [Indexed: 11/19/2022] Open
Abstract
PURPOSE To evaluate and correlate findings obtained by optical coherence tomography (OCT) imaging with visual acuity (VA) and macular lesions in patients with X-linked retinoschisis (XLRS). DESIGN Prospective comparative case series. PARTICIPANTS Thirty-one patients with confirmed XLRS. METHODS Best-corrected VA was determined using Early Treatment Diabetic Retinopathy Study charts, and a dilated funduscopic examination was performed on all patients. For all patients, the macula in each eye was OCT imaged. A correlation between VA, macular presentation, and OCT images was determined. MAIN OUTCOME MEASURES Analysis of findings on OCT images, including foveal thickness and the area of macular cystic-appearing lesions, and their correlation with VA. RESULTS Twenty-five patients with funduscopically evident cystic-appearing macular lesions demonstrated cysticlike spaces on OCT images. No statistically significant correlation was observed between the macular area of the cysticlike spaces, foveal thickness, and VA. Three patients with no funduscopic or OCT evidence of foveal cysts demonstrated thinning of the fovea on OCT images and more extensive reduction of their VA. Retinal papillomacular bundle nerve fiber layer thickness on OCT images showed no significant difference between control and patient groups. CONCLUSIONS In XLRS patients with cystic-appearing macular lesions, there was a lack of correlation between VA, foveal thickness, and cystic area. The anatomical appearance of smaller perifoveal cysts on OCT imaging was most consistent with their location being primarily within the inner nuclear layer of the retina. In older patients, macular cysts were no longer apparent clinically or by OCT imaging, and foveal thickness was reduced. The findings on OCT images are consistent with the hypothesis of a primary Muller cell defect in patients with XLRS.
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Affiliation(s)
- Marsha A Apushkin
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612, USA
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Reid SNM, Farber DB. Glial transcytosis of a photoreceptor-secreted signaling protein, retinoschisin. Glia 2005; 49:397-406. [PMID: 15538749 DOI: 10.1002/glia.20131] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
In vitro studies have clearly shown that signaling/guidance proteins can diffuse to their targets. However, it is unclear whether they can travel by diffusion in vivo, or if they are distributed in the tissue by an active mechanism. Retinoschisin, a signaling molecule related to neuropilins, is synthesized and secreted by photoreceptor cells in the outer retina; then it interacts with inner retinal cells contributing to synaptic organization and optic nerve fiber integrity. We developed an assay to examine how retinoschisin, which is secreted a distance away, reaches its inner retinal targets. We found that retinoschisin is preferentially taken up and carried into the inner retina from the retinal outer border (the photoreceptor side) by Müller cells (the main glial cells of the vertebrate retina). This transcytosis is disrupted by DL-alpha-aminoadipic acid, a Müller cell/glia-specific toxin. Our results suggest that glial uptake/transcytosis can provide an effective and precise alternative for distributing signaling molecules in the nervous system.
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Affiliation(s)
- Silvia N M Reid
- Jules Stein Eye Institute, UCLA School of Medicine Center for the Health Sciences, 100 Stein Plaza, Los Angeles, CA 90095-7008, USA.
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Wu WWH, Wong JP, Kast J, Molday RS. RS1, a discoidin domain-containing retinal cell adhesion protein associated with X-linked retinoschisis, exists as a novel disulfide-linked octamer. J Biol Chem 2005; 280:10721-30. [PMID: 15644328 DOI: 10.1074/jbc.m413117200] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
RS1, also known as retinoschisin, is an extracellular protein that plays a crucial role in the cellular organization of the retina. Mutations in RS1 are responsible for X-linked retinoschisis, a common, early-onset macular degeneration in males that results in a splitting of the inner layers of the retina and severe loss in vision. RS1 is assembled and secreted from photoreceptors and bipolar cells as a homo-oligomeric protein complex. Each subunit consists of a 157-amino acid discoidin domain flanked by two small segments of 39 and 5 amino acids. To begin to understand how the structure of RS1 relates to its role in retinal cell adhesion and X-linked retinoschisis, we have determined the subunit organization and disulfide bonding pattern of RS1 by SDS gel electrophoresis, velocity sedimentation, and mass spectrometry. Our results indicate that RS1 exists as a novel octamer in which the eight subunits are joined together by Cys(59)-Cys(223) intermolecular disulfide bonds. Subunits within the octamer are further organized into dimers mediated by Cys(40)-Cys(40) bonds. These cysteines lie just outside the discoidin domain indicating that these flanking segments primarily function in the octamerization of RS1. Within the discoidin domain, two cysteine pairs (Cys(63)-Cys(219) and Cys(110)-Cys(142)) form intramolecular disulfide bonds that are important in protein folding, and one cysteine (Cys(83)) exists in its reduced state. Because mutations that disrupt subunit assembly cause X-linked retinoschisis, the assembly of RS1 into a disulfide-linked homo-octamer appears to be critical for its function as a retinal cell adhesion protein.
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Affiliation(s)
- Winco W H Wu
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, V6T 1Z3, Canada
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Tantri A, Vrabec TR, Cu-Unjieng A, Frost A, Annesley WH, Donoso LA. X-linked retinoschisis: A clinical and molecular genetic review. Surv Ophthalmol 2004; 49:214-30. [PMID: 14998693 DOI: 10.1016/j.survophthal.2003.12.007] [Citation(s) in RCA: 144] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
X-linked retinoschisis is a leading cause of macular degeneration in male children. It is characterized by a high degree of clinical variability. Clinical features include a stellate foveal retinoschisis, with or without peripheral retinoschisis. The schisis occurs within the inner retina, primarily at the level of the nerve fiber layer. The disease-causing gene, X-linked retinoschisis 1, has recently been identified, and is expressed in photoreceptor and bipolar cells. This gene codes for retinoschisin, a secreted protein containing a discoidin domain which may be involved in cellular adhesion or cell-cell interactions. The identification of this gene allows for improved diagnosis and contributes to the understanding of this condition. Visual prognosis is variable, as X-linked retinoschisis exhibits a high degree of phenotypic variability. Although there is no treatment to halt the progressive maculopathy, clinical management is directed toward treatment of amblyopia and surgical correction of certain complications. X-linked retinoschisis is an important condition to study, both to improve the clinical management of this disorder, and to better understand retinal function and development. Herein, we review the clinical, histopathologic, and molecular genetic and treatment options of X-linked retinoschisis.
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Affiliation(s)
- Avinash Tantri
- The Henry and Corinne Bower Laboratory, Wills Eye Hospital, and the Eye Research Institute, Philadelphia, Pennsylvania, USA
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39
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Abstract
Usually, photoreceptors interact with other retinal cells through the neurotransmitter glutamate. Here we describe a nonsynaptic interaction via a secreted protein, retinoschisin. Using in situ hybridization, we found that from early postnatal life retinoschisin mRNA is present only in the outer retina of the mouse, and with single-cell RT-PCR we demonstrated its localization in rod and cone photoreceptor cells but not in Müller cells. Western blot analyses of proteins from cultured ocular tissues and microdissected outer and inner retinas, as well as from the culture media of these samples, showed that retinoschisin is secreted from the photoreceptor cells. Immunostaining of permeabilized and nonpermeabilized dissociated retinal cells revealed that retinoschisin is mainly inside and outside the photoreceptors, outside bipolar cells, and associated with plasma membranes of Müller cells and inside their distal processes. Because we showed previously that retinoschisin is distributed all over the retina, our current data suggest that after synthesis and secretion by the photoreceptors, retinoschisin reaches the surface of retinal cells and mediates interactions/adhesion between photoreceptor, bipolar, and Müller cells, contributing to the maintenance of the cytoarchitectural integrity of the retina. These interactions may not occur when the gene encoding retinoschisin is mutated, as it occurs in X-linked juvenile retinoschisis, a disease that results in morphological and electrophysiological defects of the retina.
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40
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Wu WWH, Molday RS. Defective discoidin domain structure, subunit assembly, and endoplasmic reticulum processing of retinoschisin are primary mechanisms responsible for X-linked retinoschisis. J Biol Chem 2003; 278:28139-46. [PMID: 12746437 DOI: 10.1074/jbc.m302464200] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Retinoschisin is a 24-kDa discoidin domain-containing protein that is secreted from photoreceptor and bipolar cells as a large disulfide-linked multisubunit complex. It functions as a cell adhesion protein to maintain the cellular organization and synaptic structure of the retina. Over 125 different mutations in the RS1 gene are associated with X-linked juvenile retinoschisis, the most common form of early onset macular degeneration in males. To identify molecular determinants important for retinoschisin structure and function and elucidate molecular and cellular mechanisms responsible for X-linked juvenile retinoschisis, we have analyzed the expression, protein folding, disulfide-linked subunit assembly, intracellular localization, and secretion of wild-type retinoschisin, 15 Cys-to-Ser variants and 12 disease-linked mutants. Our studies, together with molecular modeling of the discoidin domain, identify Cys residues involved in intramolecular and intermolecular disulfide bonds essential for protein folding and subunit assembly. We show that misfolding of the discoidin domain, defective disulfide-linked subunit assembly, and inability of retinoschisin to insert into the endoplasmic reticulum membrane as part of the protein secretion process are three primary mechanisms responsible for the loss in the function of retinoschisin as a cell adhesion protein and the pathogenesis of X-linked juvenile retinoschisis.
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Affiliation(s)
- Winco W H Wu
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
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Burris C, Klug K, Ngo IT, Sterling P, Schein S. How Müller glial cells in macaque fovea coat and isolate the synaptic terminals of cone photoreceptors. J Comp Neurol 2002; 453:100-11. [PMID: 12357435 DOI: 10.1002/cne.10397] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A cone synaptic terminal in macaque fovea releases quanta of glutamate from approximately 20 active zones at a high rate in the dark. The transmitter reaches approximately 500 receptor clusters on bipolar and horizontal cell processes by diffusion laterally along the terminal's 50 microm(2) secretory face and approximately 2 microm inward. To understand what shapes transmitter flow, we investigated from electron photomicrographs of serial sections the relationship between Müller glial processes and cone terminals. We find that each Müller cell has one substantial trunk that ascends in the outer plexiform layer below the space between the "footprints" of the terminals. We find exactly equal numbers of Müller cell trunks and foveal cone terminals, which may make the fovea particularly vulnerable to Müller cell dysfunction. The processes that emerge from the single trunk do not ensheathe a single terminal. Instead, each Müller cell partially coats two to three terminals; in turn, each terminal is completely coated by two to three Müller cells. Therefore, the Müller cells that coat one terminal also partially coat the surrounding ( approximately six) terminals, creating a common environment for the cones supplying the center/surround receptive field of foveal midget bipolar and ganglion cells. Upon reaching the terminals, the trunk divides into processes that coat the terminals' sides but not their secretory faces. This glial framework minimizes glutamate transporter (EAAT1) beneath a terminal's secretory face but maximizes EAAT1 between adjacent terminals, thus permitting glutamate to diffuse locally along the secretory face and inward toward inner receptor clusters but reducing its effective spillover to neighboring terminals.
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Affiliation(s)
- Christine Burris
- Department of Psychology, Franz Hall, University of California, Los Angeles, Los Angeles, California, 90095-1563, USA
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Weber BHF, Schrewe H, Molday LL, Gehrig A, White KL, Seeliger MW, Jaissle GB, Friedburg C, Tamm E, Molday RS. Inactivation of the murine X-linked juvenile retinoschisis gene, Rs1h, suggests a role of retinoschisin in retinal cell layer organization and synaptic structure. Proc Natl Acad Sci U S A 2002; 99:6222-7. [PMID: 11983912 PMCID: PMC122930 DOI: 10.1073/pnas.092528599] [Citation(s) in RCA: 163] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Deleterious mutations in RS1 encoding retinoschisin are associated with X-linked juvenile retinoschisis (RS), a common form of macular degeneration in males. The disorder is characterized by a negative electroretinogram pattern and by a splitting of the inner retina. To gain further insight into the function of the retinoschisin protein and its role in the cellular pathology of RS, we have generated knockout mice deficient in Rs1h, the murine ortholog of the human RS1 gene. We show that pathologic changes in hemizygous Rs1h(-/Y) male mice are evenly distributed across the retina, apparently contrasting with the macula-dominated features in human. Similar functional anomalies in human and Rs1h(-/Y) mice, however, suggest that both conditions are a disease of the entire retina affecting the organization of the retinal cell layers as well as structural properties of the retinal synapse.
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Affiliation(s)
- Bernhard H F Weber
- Institute of Human Genetics, Biocenter, University of Würzburg, D-97074 Würzburg, Germany.
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Curat CA, Eck M, Dervillez X, Vogel WF. Mapping of epitopes in discoidin domain receptor 1 critical for collagen binding. J Biol Chem 2001; 276:45952-8. [PMID: 11598108 DOI: 10.1074/jbc.m104360200] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The binding and activation of the discoidin domain receptor 1 by collagen has led to the conclusion that proteins from the extracellular matrix can directly induce receptor tyrosine kinase-mediated signaling cascades. A region in the extracellular domain of DDR1 homologous to the Dictyostelium discoideum protein discoidin-I is also present in the secreted human protein RS1. Mutations in RS1 cause retinoschisis, a genetic disorder characterized by ablation of the retina. By introducing point mutations into the discoidin domain of DDR1 at positions homologous to the retinoschisis mutations, ligand binding epitopes in the discoidin domain of DDR1 were mapped. Surprisingly, some residues only affected receptor phosphorylation, whereas others influenced both collagen-binding and receptor activation. Furthermore, two truncated DDR1 variants, lacking either the discoidin domain or the stalk region between the discoidin and transmembrane domain, were generated. We showed that (i) the discoidin domain was necessary and sufficient for collagen binding, (ii) only the region between discoidin and transmembrane domain was glycosylated, and (iii) the entire extracellular domain was essential for transmembrane signaling. Using these results, we were able to predict key sites in the collagen-binding epitope of DDR1 and to suggest a potential mechanism of signaling.
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Affiliation(s)
- C A Curat
- Laboratory of Extracellular Matrix Signaling and Tumor Invasion, Georg-Speyer-Haus-Institute for Biomedical Research, Johann Wolfgang von Goethe University Frankfurt, Paul-Ehrlich-Strasse 42-44, 60596 Frankfurt, Germany
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Khan NW, Jamison JA, Kemp JA, Sieving PA. Analysis of photoreceptor function and inner retinal activity in juvenile X-linked retinoschisis. Vision Res 2001; 41:3931-42. [PMID: 11738458 DOI: 10.1016/s0042-6989(01)00188-2] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Thirteen retinoschisis males with genotyped XLRS1 gene mutations were examined by electroretinogram (ERG) techniques to determine photoreceptor involvement and ON-pathway and OFF-pathway sites of dysfunction. Parameters R(max) and logS determined by fitting the mathematical model of the activation phase of phototransduction to the scotopic and photopic a-wave responses, were not significantly different from normal. However, the XLRS photopic a-wave amplitudes were significantly lower than normal across all intensities, consistent with defective signaling in the OFF pathway. Long flash (150 ms) ON-OFF photopic responses showed reduced b-wave amplitude but normal d-wave amplitude, giving a reduced b/d ratio of <1.32 Hz photopic flicker ERG fundamental frequency responses showed reduced amplitude and delayed phase, consistent with abnormal signaling by both the ON- and OFF-pathway components. These results indicate that the XLRS1 protein appears not to affect photoreceptor function directly for most XLRS males, and that ERG signaling abnormalities occur in both the ON- and OFF-pathway components that originate in the proximal retina.
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Affiliation(s)
- N W Khan
- Department of Ophthalmology and Visual Sciences, W. K. Kellogg Eye Center, University of Michigan, 1000 Wall Street, Ann Arbor, MI 48105, USA
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45
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Blackshaw S, Fraioli RE, Furukawa T, Cepko CL. Comprehensive analysis of photoreceptor gene expression and the identification of candidate retinal disease genes. Cell 2001; 107:579-89. [PMID: 11733058 DOI: 10.1016/s0092-8674(01)00574-8] [Citation(s) in RCA: 220] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
To identify the full set of genes expressed by mammalian rods, we conducted serial analysis of gene expression (SAGE) by using libraries generated from mature and developing mouse retina. We identified 264 uncharacterized genes that were specific to or highly enriched in rods. Nearly half of all cloned human retinal disease genes are selectively expressed in rod photoreceptors. In silico mapping of the human orthologs of genes identified in our screen revealed that 86 map within intervals containing uncloned retinal disease genes, representing 37 different loci. We expect these data will allow identification of many disease genes, and that this approach may be useful for cloning genes involved in classes of disease where cell type-specific expression of disease genes is observed.
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Affiliation(s)
- S Blackshaw
- Department of Genetics, Howard Hughes Medical Institute, Harvard Medical School, 200 Longwood Avenue, Boston, MA 02115, USA
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46
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Shinoda K, Ohde H, Mashima Y, Inoue R, Ishida S, Inoue M, Kawashima S, Oguchi Y. On- and off-responses of the photopic electroretinograms in X-linked juvenile retinoschisis. Am J Ophthalmol 2001; 131:489-94. [PMID: 11292413 DOI: 10.1016/s0002-9394(00)00858-8] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
PURPOSE To examine the physiologic condition of the middle retinal layer of patients with X-linked juvenile retinoschisis (xlRS) by studying the on- and off-responses of the photopic electroretinograms (ERGs). METHODS Eleven unrelated Japanese men (mean age; 24.9 +/- 7.6 years) who were clinically diagnosed with xlRS and molecularly confirmed as having XLRS1 mutations were investigated. For the photopic ERGs, the a-, b- and d-wave amplitudes elicited by long duration stimuli were recorded, and the responses from the xlRS patients were compared to those recorded from normal subjects (n = 14, mean age, 27.5 +/- 4.5 years). We also examined the relationship between the photopic ERG responses and the genotype. RESULTS No significant difference was found between the a- and d-wave amplitudes in the xlRS patients (34.2 +/- 8.7 microV, 52.5 +/- 10.4 microV, respectively), and those in normal subjects (40.4 +/- 10.3 microV, 44.7 +/- 6.3 microV, respectively). The mean b-wave amplitude in the xlRS patients was significantly smaller (10.5 +/- 7.7 microV) than the mean of normal subjects (46.4 +/- 10.2 microV) (P < 0.0001). No significant correlation was found between the ERG responses and the locus of the mutation. CONCLUSION The photopic ERG demonstrated considerable impairment of the on-pathway arising from an abnormality of the on-bipolar cells or possibly secondary to Müller cell abnormality in xlRS.
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Affiliation(s)
- K Shinoda
- Department of Ophthalmology, Keio University School of Medicine, Shinjuku-ku, Tokyo, Japan.
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Huopaniemi L, Tyynismaa H, Rantala A, Rosenberg T, Alitalo T. Characterization of two unusual RS1 gene deletions segregating in Danish retinoschisis families. Hum Mutat 2000; 16:307-14. [PMID: 11013441 DOI: 10.1002/1098-1004(200010)16:4<307::aid-humu3>3.0.co;2-l] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Over 100 distinct retinoschisis gene (RS1) mutations, of which approximately 10% are single exon deletions, have been described to date. In this paper we have characterized in detail two dissimilar RS1 gene deletions which are accountable for RS in one-third of Danish patients. First, a 136 kb deletion, spanning from the 5' region of the RS1 gene to intron 3, was identified. Unexpectedly this large deletion abolishes exons of three adjacent genes: serine-threonine phosphatase gene (PPEF-1)/serine-threonine protein phosphatase gene (PP7), retinoschisis gene (RS1), and serine-threonine kinase gene (STK9). We demonstrate that the RS1 and STK9 genes are partly overlapping and the sequences of the PP7 and PPEF-1 genes are identical. This is the first study which reports of retinoschisis patients who also suffer from deletions in genes adjacent to RS1. The 136 kb deletion is also the first gross deletion of the retinoschisis gene deleting three exons. It results from a recombination between two repetitive sequences of the Alu family, one in 5' region of the RS1 gene and the other in RS1 intron 3. The second alteration, the actual Danish RS founder mutation, is a 4.4 kb noncontiguous two-part deletion composed of two deleted 1.5 and 2.9 kb segments, separated by an intact 1.2 kb segment. It extends from the 5' flanking region of the retinoschisis gene to RS intron 1. RS1 gene deletions of this type have not been identified previously. Despite these two unique deletions, which either lead to severely defective transcription or total absence of the retinoschisin and PPEF-1 protein, all the patients have a typical retinoschisis phenotype.
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Affiliation(s)
- L Huopaniemi
- Department of Medical Genetics, University of Helsinki, Helsinki, Finland
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Abstract
The past decade has witnessed extraordinary progress in retinal disease gene identification, the analysis of animal and tissue culture models of disease processes, and the integration of this information with clinical observations and with retinal biochemistry and physiology. During this period over twenty retinal disease genes were identified and for many of these genes there are now significant insights into their role in disease. This review presents an overview of the basic and clinical biology of the retina, summarizes recent progress in understanding the molecular mechanisms of inherited retinal diseases, and offers an assessment of the role that genetics will play in the next phase of research in this area.
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Affiliation(s)
- A Rattner
- Department of Molecular Biology and Genetics, Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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49
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Hiriyanna KT, Bingham EL, Yashar BM, Ayyagari R, Fishman G, Small KW, Weinberg DV, Weleber RG, Lewis RA, Andreasson S, Richards JE, Sieving PA. Novel mutations in XLRS1 causing retinoschisis, including first evidence of putative leader sequence change. Hum Mutat 1999; 14:423-7. [PMID: 10533068 DOI: 10.1002/(sici)1098-1004(199911)14:5<423::aid-humu8>3.0.co;2-d] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Juvenile retinoschisis is an X-linked recessive disease caused by mutations in the XLRS1 gene. We screened 31 new unrelated patients and families for XLRS1 mutations in addition to previously reported mutations for 60 of our families (Retinoschisis Consortium, Hum Mol Genet 1998;7:1185-1192). Twenty-three different mutations including 12 novel ones were identified in 28 patients. Mutations identified in this study include 19 missense mutations, two nonsense mutations, one intragenic deletion, four microdeletions, one insertion, and one intronic sequence substitution that is likely to result in a splice site defect. Two novel mutations, c.38T-->C (L13P) and c.667T-->C (C223R), respectively, present the first genetic evidence for the functional significance of the putative leader peptide sequence and for the functional significance at the carboxyl terminal of the XLRS1 protein beyond the discoidin domain. Mutations in 25 of the families were localized to exons 4-6, emphasizing the critical functional significance of the discoidin domain of the XLRS1 protein.
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Affiliation(s)
- K T Hiriyanna
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, University of Michigan, Ann Arbor 48105, USA.
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