1
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Pan Y, Iwata T. Exploring the Genetic Landscape of Childhood Glaucoma. CHILDREN (BASEL, SWITZERLAND) 2024; 11:454. [PMID: 38671671 PMCID: PMC11048810 DOI: 10.3390/children11040454] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Revised: 04/03/2024] [Accepted: 04/08/2024] [Indexed: 04/28/2024]
Abstract
Childhood glaucoma, a significant cause of global blindness, represents a heterogeneous group of disorders categorized into primary or secondary forms. Primary childhood glaucoma stands as the most prevalent subtype, comprising primary congenital glaucoma (PCG) and juvenile open-angle glaucoma (JOAG). Presently, multiple genes are implicated in inherited forms of primary childhood glaucoma. This comprehensive review delves into genetic investigations into primary childhood glaucoma, with a focus on identifying causative genes, understanding their inheritance patterns, exploring essential biological pathways in disease pathogenesis, and utilizing animal models to study these mechanisms. Specifically, attention is directed towards genes such as CYP1B1 (cytochrome P450 family 1 subfamily B member 1), LTBP2 (latent transforming growth factor beta binding protein 2), TEK (TEK receptor tyrosine kinase), ANGPT1 (angiopoietin 1), and FOXC1 (forkhead box C1), all associated with PCG; and MYOC (myocilin), associated with JOAG. Through exploring these genetic factors, this review aims to deepen our understanding of the intricate pathogenesis of primary childhood glaucoma, thereby facilitating the development of enhanced diagnostic and therapeutic strategies.
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Affiliation(s)
| | - Takeshi Iwata
- National Institute of Sensory Organs, NHO Tokyo Medical Center, Tokyo 152-8902, Japan;
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2
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Patil SV, Kaipa BR, Ranshing S, Sundaresan Y, Millar JC, Nagarajan B, Kiehlbauch C, Zhang Q, Jain A, Searby CC, Scheetz TE, Clark AF, Sheffield VC, Zode GS. Lentiviral mediated delivery of CRISPR/Cas9 reduces intraocular pressure in a mouse model of myocilin glaucoma. Sci Rep 2024; 14:6958. [PMID: 38521856 PMCID: PMC10960846 DOI: 10.1038/s41598-024-57286-6] [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: 12/11/2023] [Accepted: 03/16/2024] [Indexed: 03/25/2024] Open
Abstract
Mutations in myocilin (MYOC) are the leading known genetic cause of primary open-angle glaucoma, responsible for about 4% of all cases. Mutations in MYOC cause a gain-of-function phenotype in which mutant myocilin accumulates in the endoplasmic reticulum (ER) leading to ER stress and trabecular meshwork (TM) cell death. Therefore, knocking out myocilin at the genome level is an ideal strategy to permanently cure the disease. We have previously utilized CRISPR/Cas9 genome editing successfully to target MYOC using adenovirus 5 (Ad5). However, Ad5 is not a suitable vector for clinical use. Here, we sought to determine the efficacy of adeno-associated viruses (AAVs) and lentiviruses (LVs) to target the TM. First, we examined the TM tropism of single-stranded (ss) and self-complimentary (sc) AAV serotypes as well as LV expressing GFP via intravitreal (IVT) and intracameral (IC) injections. We observed that LV_GFP expression was more specific to the TM injected via the IVT route. IC injections of Trp-mutant scAAV2 showed a prominent expression of GFP in the TM. However, robust GFP expression was also observed in the ciliary body and retina. We next constructed lentiviral particles expressing Cas9 and guide RNA (gRNA) targeting MYOC (crMYOC) and transduction of TM cells stably expressing mutant myocilin with LV_crMYOC significantly reduced myocilin accumulation and its associated chronic ER stress. A single IVT injection of LV_crMYOC in Tg-MYOCY437H mice decreased myocilin accumulation in TM and reduced elevated IOP significantly. Together, our data indicates, LV_crMYOC targets MYOC gene editing in TM and rescues a mouse model of myocilin-associated glaucoma.
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Affiliation(s)
- Shruti V Patil
- Department of Pharmacology and Neuroscience, North Texas Eye Research Institute, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, 76107, USA
| | - Balasankara Reddy Kaipa
- Department of Ophthalmology and Center for Translational Vision Research, University of California, 829 Health Sciences Rd, Irvine, CA, 92617, USA
| | - Sujata Ranshing
- Department of Pharmacology and Neuroscience, North Texas Eye Research Institute, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, 76107, USA
| | - Yogapriya Sundaresan
- Department of Ophthalmology and Center for Translational Vision Research, University of California, 829 Health Sciences Rd, Irvine, CA, 92617, USA
| | - J Cameron Millar
- Department of Pharmacology and Neuroscience, North Texas Eye Research Institute, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, 76107, USA
| | - Bhavani Nagarajan
- Department of Pharmacology and Neuroscience, North Texas Eye Research Institute, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, 76107, USA
| | - Charles Kiehlbauch
- Department of Pharmacology and Neuroscience, North Texas Eye Research Institute, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, 76107, USA
| | - Qihong Zhang
- Department of Pediatrics, University of Iowa, Iowa City, IA, 52242, USA
| | - Ankur Jain
- Department of Pediatrics, University of Iowa, Iowa City, IA, 52242, USA
| | - Charles C Searby
- Department of Pediatrics, University of Iowa, Iowa City, IA, 52242, USA
| | - Todd E Scheetz
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, IA, 52242, USA
| | - Abbot F Clark
- Department of Pharmacology and Neuroscience, North Texas Eye Research Institute, University of North Texas Health Science Center at Fort Worth, Fort Worth, TX, 76107, USA
| | - Val C Sheffield
- Department of Pediatrics, University of Iowa, Iowa City, IA, 52242, USA
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, IA, 52242, USA
| | - Gulab S Zode
- Department of Ophthalmology and Center for Translational Vision Research, University of California, 829 Health Sciences Rd, Irvine, CA, 92617, USA.
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3
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Saccuzzo EG, Mebrat MD, Scelsi HF, Kim M, Ma MT, Su X, Hill SE, Rheaume E, Li R, Torres MP, Gumbart JC, Van Horn WD, Lieberman RL. Competition between inside-out unfolding and pathogenic aggregation in an amyloid-forming β-propeller. Nat Commun 2024; 15:155. [PMID: 38168102 PMCID: PMC10762032 DOI: 10.1038/s41467-023-44479-2] [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: 02/14/2023] [Accepted: 12/14/2023] [Indexed: 01/05/2024] Open
Abstract
Studies of folded-to-misfolded transitions using model protein systems reveal a range of unfolding needed for exposure of amyloid-prone regions for subsequent fibrillization. Here, we probe the relationship between unfolding and aggregation for glaucoma-associated myocilin. Mutations within the olfactomedin domain of myocilin (OLF) cause a gain-of-function, namely cytotoxic intracellular aggregation, which hastens disease progression. Aggregation by wild-type OLF (OLFWT) competes with its chemical unfolding, but only below the threshold where OLF loses tertiary structure. Representative moderate (OLFD380A) and severe (OLFI499F) disease variants aggregate differently, with rates comparable to OLFWT in initial stages of unfolding, and variants adopt distinct partially folded structures seen along the OLFWT urea-unfolding pathway. Whether initiated with mutation or chemical perturbation, unfolding propagates outward to the propeller surface. In sum, for this large protein prone to amyloid formation, the requirement for a conformational change to promote amyloid fibrillization leads to direct competition between unfolding and aggregation.
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Affiliation(s)
- Emily G Saccuzzo
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, USA
| | - Mubark D Mebrat
- Biodesign Center for Personalized Diagnostics, Arizona State University, Tempe, USA
- School of Molecular Sciences, Arizona State University, Tempe, USA
| | - Hailee F Scelsi
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, USA
| | - Minjoo Kim
- Biodesign Center for Personalized Diagnostics, Arizona State University, Tempe, USA
- School of Molecular Sciences, Arizona State University, Tempe, USA
| | - Minh Thu Ma
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, USA
| | - Xinya Su
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, USA
| | - Shannon E Hill
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, USA
| | - Elisa Rheaume
- Interdisciplinary Graduate Program in Quantitative Biosciences, Georgia Institute of Technology, Atlanta, USA
| | - Renhao Li
- Aflac Cancer and Blood Disorders Center, Children's Healthcare of Atlanta and Department of Pediatrics, Emory University School of Medicine, Atlanta, USA
| | - Matthew P Torres
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, USA
| | - James C Gumbart
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, USA
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, USA
- School of Physics, Georgia Institute of Technology, Atlanta, USA
| | - Wade D Van Horn
- Biodesign Center for Personalized Diagnostics, Arizona State University, Tempe, USA.
- School of Molecular Sciences, Arizona State University, Tempe, USA.
| | - Raquel L Lieberman
- School of Chemistry & Biochemistry, Georgia Institute of Technology, Atlanta, USA.
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4
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Patil SV, Kaipa BR, Ranshing S, Sundaresan Y, Millar JC, Nagarajan B, Kiehlbauch C, Zhang Q, Jain A, Searby CC, Scheetz TE, Clark AF, Sheffield VC, Zode GS. Lentiviral mediated delivery of CRISPR/Cas9 reduces intraocular pressure in a mouse model of myocilin glaucoma. RESEARCH SQUARE 2023:rs.3.rs-3740880. [PMID: 38196579 PMCID: PMC10775399 DOI: 10.21203/rs.3.rs-3740880/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
Mutations in myocilin (MYOC) are the leading known genetic cause of primary open-angle glaucoma, responsible for about 4% of all cases. Mutations in MYOC cause a gain-of-function phenotype in which mutant myocilin accumulates in the endoplasmic reticulum (ER) leading to ER stress and trabecular meshwork (TM) cell death. Therefore, knocking out myocilin at the genome level is an ideal strategy to permanently cure the disease. We have previously utilized CRISPR/Cas9 genome editing successfully to target MYOC using adenovirus 5 (Ad5). However, Ad5 is not a suitable vector for clinical use. Here, we sought to determine the efficacy of adeno-associated viruses (AAVs) and lentiviruses (LVs) to target the TM. First, we examined the TM tropism of single-stranded (ss) and self-complimentary (sc) AAV serotypes as well as LV expressing GFP via intravitreal (IVT) and intracameral (IC) injections. We observed that LV_GFP expression was more specific to the TM injected via the IVT route. IC injections of Trp-mutant scAAV2 showed a prominent expression of GFP in the TM. However, robust GFP expression was also observed in the ciliary body and retina. We next constructed lentiviral particles expressing Cas9 and guide RNA (gRNA) targeting MYOC (crMYOC) and transduction of TM cells stably expressing mutant myocilin with LV_crMYOC significantly reduced myocilin accumulation and its associated chronic ER stress. A single IVT injection of LV_crMYOC in Tg-MYOCY437H mice decreased myocilin accumulation in TM and reduced elevated IOP significantly. Together, our data indicates, LV_crMYOC targets MYOC gene editing in TM and rescues a mouse model of myocilin-associated glaucoma.
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Affiliation(s)
- Shruti V Patil
- University of North Texas Health Science Center at Fort Worth
| | | | - Sujata Ranshing
- University of North Texas Health Science Center at Fort Worth
| | | | | | | | | | | | | | | | | | - Abbot F Clark
- University of North Texas Health Science Center at Fort Worth
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5
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Saccuzzo EG, Youngblood HA, Lieberman RL. Myocilin misfolding and glaucoma: A 20-year update. Prog Retin Eye Res 2023:101188. [PMID: 37217093 DOI: 10.1016/j.preteyeres.2023.101188] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2023] [Revised: 05/18/2023] [Accepted: 05/19/2023] [Indexed: 05/24/2023]
Abstract
Mutations in the gene MYOC account for approximately 5% of cases of primary open angle glaucoma (POAG). MYOC encodes for the protein myocilin, a multimeric secreted glycoprotein composed of N-terminal coil-coil (CC) and leucine zipper (LZ) domains that are connected via a disordered linker to a 30 kDa olfactomedin (OLF) domain. More than 90% of glaucoma-causing mutations are localized to the OLF domain. While myocilin is expressed in numerous tissues, mutant myocilin is only associated with disease in the anterior segment of the eye, in the trabecular meshwork. The prevailing pathogenic mechanism involves a gain of toxic function whereby mutant myocilin aggregates intracellularly instead of being secreted, which causes cell stress and an early timeline for TM cell death, elevated intraocular pressure, and subsequent glaucomatous neurodegeneration. In this review, we focus on the work our lab has conducted over the past ∼15 years to enhance our molecular understanding of myocilin-associated glaucoma, which includes details of the molecular structure and the nature of the aggregates formed by mutant myocilin. We conclude by discussing open questions, such as predicting phenotype from genotype alone, the elusive native function of myocilin, and translational directions enabled by our work.
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Affiliation(s)
- Emily G Saccuzzo
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA, 30332-0400, USA
| | - Hannah A Youngblood
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA, 30332-0400, USA
| | - Raquel L Lieberman
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA, 30332-0400, USA.
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6
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Scelsi HF, Hill KR, Barlow BM, Martin MD, Lieberman RL. Quantitative differentiation of benign and misfolded glaucoma-causing myocilin variants on the basis of protein thermal stability. Dis Model Mech 2023; 16:286212. [PMID: 36579626 PMCID: PMC9844228 DOI: 10.1242/dmm.049816] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 11/28/2022] [Indexed: 12/30/2022] Open
Abstract
Accurate predictions of the pathogenicity of mutations associated with genetic diseases are key to the success of precision medicine. Inherited missense mutations in the myocilin (MYOC) gene, within its olfactomedin (OLF) domain, constitute the strongest genetic link to primary open-angle glaucoma via a toxic gain of function, and thus MYOC is an attractive precision-medicine target. However, not all mutations in MYOC cause glaucoma, and common variants are expected to be neutral polymorphisms. The Genome Aggregation Database (gnomAD) lists ∼100 missense variants documented within OLF, all of which are relatively rare (allele frequency <0.001%) and nearly all are of unknown pathogenicity. To distinguish disease-causing OLF variants from benign OLF variants, we first characterized the most prevalent population-based variants using a suite of cellular and biophysical assays, and identified two variants with features of aggregation-prone familial disease variants. Next, we considered all available biochemical and clinical data to demonstrate that pathogenic and benign variants can be differentiated statistically based on a single metric: the thermal stability of OLF. Our results motivate genotyping MYOC in patients for clinical monitoring of this widespread, painless and irreversible ocular disease.
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Affiliation(s)
- Hailee F. Scelsi
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA 30332-0400, USA
| | - Kamisha R. Hill
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA 30332-0400, USA
| | - Brett M. Barlow
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA 30332-0400, USA
| | - Mackenzie D. Martin
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA 30332-0400, USA
| | - Raquel L. Lieberman
- School of Chemistry & Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA 30332-0400, USA,Author for correspondence ()
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7
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Burdon KP, Graham P, Hadler J, Hulleman JD, Pasutto F, Boese EA, Craig JE, Fingert JH, Hewitt AW, Siggs OM, Whisenhunt K, Young TL, Mackey DA, Dubowsky A, Souzeau E. Specifications of the ACMG/AMP variant curation guidelines for myocilin: Recommendations from the clingen glaucoma expert panel. Hum Mutat 2022; 43:2170-2186. [PMID: 36217948 PMCID: PMC9771967 DOI: 10.1002/humu.24482] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 09/02/2022] [Accepted: 10/06/2022] [Indexed: 01/25/2023]
Abstract
The standardization of variant curation criteria is essential for accurate interpretation of genetic results and clinical care of patients. The variant curation guidelines developed by the American College of Medical Genetics and Genomics (ACMG) and the Association for Molecular Pathology (AMP) in 2015 are widely used but are not gene specific. To address this issue, the Clinical Genome Resource (ClinGen) Variant Curation Expert Panels (VCEP) have been tasked with developing gene-specific variant curation guidelines. The Glaucoma VCEP was created to develop rule specifications for genes associated with primary glaucoma, including myocilin (MYOC), the most common cause of Mendelian glaucoma. Of the 28 ACMG/AMP criteria, the Glaucoma VCEP adapted 15 rules to MYOC and determined 13 rules not applicable. Key specifications included determining minor allele frequency thresholds, developing an approach to counting probands and segregations, and reviewing functional assays. The rules were piloted on 81 variants and led to a change in classification in 40% of those that were classified in ClinVar, with functional evidence influencing the classification of 18 variants. The standardized variant curation guidelines for MYOC provide a framework for the consistent application of the rules between laboratories, to improve MYOC genetic testing in the management of glaucoma.
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Affiliation(s)
- Kathryn P. Burdon
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
| | - Patricia Graham
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
- Centre for Ophthalmology and Vision Sciences, Lions Eye Institute, University of Western Australia, Perth, WA, Australia
| | - Johanna Hadler
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, SA, Australia
- SA Pathology, Adelaide, SA, Australia
| | - John D. Hulleman
- Department of Ophthalmology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Francesca Pasutto
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Erin A. Boese
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa, USA
| | - Jamie E. Craig
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, SA, Australia
| | - John H. Fingert
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, Iowa, USA
| | - Alex W. Hewitt
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
| | - Owen M. Siggs
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, SA, Australia
- Garvan Institute of Medical Research, Darlinghurst, NSW, Australia
| | - Kristina Whisenhunt
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA
| | - Terri L. Young
- Department of Ophthalmology and Visual Sciences, University of Wisconsin-Madison, Madison, WI, USA
| | - David A. Mackey
- Menzies Institute for Medical Research, University of Tasmania, Hobart, TAS, Australia
- Centre for Ophthalmology and Vision Sciences, Lions Eye Institute, University of Western Australia, Perth, WA, Australia
| | | | - Emmanuelle Souzeau
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, SA, Australia
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8
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Saccuzzo EG, Martin MD, Hill KR, Ma MT, Ku Y, Lieberman RL. Calcium dysregulation potentiates wild-type myocilin misfolding: implications for glaucoma pathogenesis. J Biol Inorg Chem 2022; 27:553-564. [PMID: 35831671 PMCID: PMC10085244 DOI: 10.1007/s00775-022-01946-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Accepted: 06/02/2022] [Indexed: 10/17/2022]
Abstract
Myocilin is secreted from trabecular meshwork cells to an eponymous extracellular matrix that is critical for maintaining intraocular pressure. Missense mutations found in the myocilin olfactomedin domain (OLF) lead to intracellular myocilin misfolding and are causative for the heritable form of early-onset glaucoma. The OLF domain contains a unique internal, hetero-dinuclear calcium site. Here, we tested the hypothesis that calcium dysregulation causes wild-type (WT) myocilin misfolding reminiscent of that observed for disease variants. Using two cellular models expressing WT myocilin, we show that the Ca2+ ATPase channel blocker thapsigargin inhibits WT myocilin secretion. Intracellular WT myocilin is at least partly insoluble and aggregated in the endoplasmic reticulum (ER), and stains positively with an amyloid dye. By comparing the effect of thapsigargin on WT myocilin to that on a de novo secretion-competent Ca2+-free variant D478S, we discern that non-secretion of WT myocilin is due initially to calcium dysregulation, and is potentiated further by resultant ER stress. In E. coli, depletion of calcium leads to recombinant expression of misfolded isolated WT OLF but the D478S variant is still produced as a folded monomer. Treatment of cells expressing a double mutant composed of D478S and either disease variants P370L or Y437H with thapsigargin promotes its misfolding and aggregation, demonstrating the limits of D478S to correct secretion defects. Taken together, the heterodinuclear calcium site is a liability for proper folding of myocilin. Our study suggests a molecular mechanism by which WT myocilin misfolding may contribute broadly to glaucoma-associated ER stress. This study explores the effect of calcium depletion on myocilin olfactomedin domain folding.
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Affiliation(s)
- Emily G Saccuzzo
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA, 30332-0400, USA
| | - Mackenzie D Martin
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA, 30332-0400, USA
| | - Kamisha R Hill
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA, 30332-0400, USA
| | - Minh Thu Ma
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA, 30332-0400, USA
| | - Yemo Ku
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA, 30332-0400, USA
| | - Raquel L Lieberman
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, GA, 30332-0400, USA.
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9
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Yan X, Wu S, Liu Q, Cheng Y, Zhang J, Wang N. Myocilin Gene Mutation Induced Autophagy Activation Causes Dysfunction of Trabecular Meshwork Cells. Front Cell Dev Biol 2022; 10:900777. [PMID: 35615698 PMCID: PMC9124892 DOI: 10.3389/fcell.2022.900777] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 04/08/2022] [Indexed: 12/12/2022] Open
Abstract
Trabecular meshwork dysfunction is the main cause of primary open angle glaucoma (POAG) associated with elevated intraocular pressure (IOP). Mutant myocilin causes glaucoma mainly via elevating IOP. Previously we have found that accumulated Asn 450 Tyr (N450Y) mutant myocilin impairs human trabecular meshwork (TM) cells by inducing chronic endoplasmic reticulum (ER) stress response in vitro. However, it is unclear how ER stress leads to TM damage and whether N450Y myocilin mutation is associated with POAG in vivo. Here we found that N450Y mutant myocilin induces autophagy, which worsens cell viability, whereas inhibition of autophagy increases viability and decreases cell death in human TM cells. Furthermore, we construct a transgenic mouse model of N450Y myocilin mutation (Tg-MYOCN450Y) and Tg-MYOCN450Y mice exhibiting glaucoma phenotypes: IOP elevation, retinal ganglion cell loss and visual impairment. Consistent with our published in vitro studies, mutant myocilin fails to secrete into aqueous humor, causes ER stress and actives autophagy in Tg-MYOCN450Y mice, and aqueous humor dynamics are altered in Tg-MYOCN450Y mice. In summary, our studies demonstrate that activation of autophagy is correlated with pathogenesis of POAG.
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Affiliation(s)
- Xuejing Yan
- Beijing Tongren Eye Center, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing Tongren Hospital, Beijing Institute of Ophthalmology, Capital Medical University, Beijing, China
- Collaborative Innovation Center for Brain Disorders, Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
| | - Shen Wu
- Beijing Tongren Eye Center, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing Tongren Hospital, Beijing Institute of Ophthalmology, Capital Medical University, Beijing, China
- Collaborative Innovation Center for Brain Disorders, Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
| | - Qian Liu
- Beijing Tongren Eye Center, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing Tongren Hospital, Beijing Institute of Ophthalmology, Capital Medical University, Beijing, China
- Collaborative Innovation Center for Brain Disorders, Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
| | - Ying Cheng
- Beijing Tongren Eye Center, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing Tongren Hospital, Beijing Institute of Ophthalmology, Capital Medical University, Beijing, China
| | - Jingxue Zhang
- Beijing Tongren Eye Center, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing Tongren Hospital, Beijing Institute of Ophthalmology, Capital Medical University, Beijing, China
- Collaborative Innovation Center for Brain Disorders, Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
- *Correspondence: Ningli Wang, ; Jingxue Zhang,
| | - Ningli Wang
- Beijing Tongren Eye Center, Beijing Ophthalmology and Visual Sciences Key Laboratory, Beijing Tongren Hospital, Beijing Institute of Ophthalmology, Capital Medical University, Beijing, China
- Collaborative Innovation Center for Brain Disorders, Beijing Institute of Brain Disorders, Capital Medical University, Beijing, China
- *Correspondence: Ningli Wang, ; Jingxue Zhang,
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10
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Collantes ERA, Delfin MS, Fan B, Torregosa JMR, Siguan-Bell C, de Guzman Florcruz NV, Martinez JMD, Masna-Hidalgo BJ, Guzman VPT, Anotado-Flores JF, Levina FD, Hernandez SRC, Collantes AA, Sibulo MC, Rong S, Wiggs JL. EFEMP1 rare variants cause familial juvenile-onset open-angle glaucoma. Hum Mutat 2022; 43:240-252. [PMID: 34923728 PMCID: PMC8972201 DOI: 10.1002/humu.24320] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 12/02/2021] [Accepted: 12/15/2021] [Indexed: 02/03/2023]
Abstract
Juvenile open-angle glaucoma (JOAG) is a severe type of glaucoma with onset before age 40 and dominant inheritance. Using exome sequencing we identified 3 independent families from the Philippines with novel EFEMP1 variants (c.238A>T, p.Asn80Tyr; c.1480T>C, p.Ter494Glnext*29; and c.1429C>T, p.Arg477Cys) co-segregating with disease. Affected variant carriers (N = 34) exhibited severe disease with average age of onset of 16 years and with 76% developing blindness. To investigate functional effects, we transfected COS7 cells with vectors expressing the three novel EFEMP1 variants and showed that all three variants found in JOAG patients caused significant intracellular protein aggregation and retention compared to wild type and also compared to EFEMP1 variants associated with other ocular phenotypes including an early-onset form of macular degeneration, Malattia Leventinese/Doyne's Honeycomb retinal dystrophy. These results suggest that rare EFEMP1 coding variants can cause JOAG through a mechanism involving protein aggregation and retention, and that the extent of intracellular retention correlates with disease phenotype. This is the first report of EFEMP1 variants causing JOAG, expanding the EFEMP1 disease spectrum. Our results suggest that EFEMP1 mutations appear to be a relatively common cause of JOAG in Filipino families, an ethnically diverse population.
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Affiliation(s)
- Edward Ryan A. Collantes
- Harvard Medical School Department of Ophthalmology, Massachusetts Eye and Ear, Boston, USA
- Department of Ophthalmology, Manila Doctors Hospital, Manila, Philippines
| | - Manuel S. Delfin
- Department of Ophthalmology, Manila Doctors Hospital, Manila, Philippines
| | - Baojian Fan
- Harvard Medical School Department of Ophthalmology, Massachusetts Eye and Ear, Boston, USA
| | - Justine May R. Torregosa
- Department of Ophthalmology, Cebu Institute of Medicine, Cebu Velez General Hospital, Cebu City, Philippines
| | - Christine Siguan-Bell
- Department of Ophthalmology, Cebu Institute of Medicine, Cebu Velez General Hospital, Cebu City, Philippines
| | - Nilo Vincent de Guzman Florcruz
- Department of Ophthalmology and Visual Sciences, University of the Philippines-Philippine General Hospital, Manila, Philippines
- Glaucoma Service, Department of Ophthalmology, East Avenue Medical Center, Quezon City, Philippines
| | - Jose Maria D. Martinez
- Glaucoma Service, Department of Ophthalmology, East Avenue Medical Center, Quezon City, Philippines
| | | | | | | | - Faye D. Levina
- Department of Ophthalmology, Jose R. Reyes Memorial Medical Center, Manila, Philippines
| | | | | | | | - Shisong Rong
- Harvard Medical School Department of Ophthalmology, Massachusetts Eye and Ear, Boston, USA
| | - Janey L. Wiggs
- Harvard Medical School Department of Ophthalmology, Massachusetts Eye and Ear, Boston, USA
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11
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Wilson MR, Satapathy S, Jeong S, Fini ME. Clusterin, other extracellular chaperones, and eye disease. Prog Retin Eye Res 2021; 89:101032. [PMID: 34896599 DOI: 10.1016/j.preteyeres.2021.101032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2021] [Revised: 11/30/2021] [Accepted: 11/30/2021] [Indexed: 12/15/2022]
Abstract
Proteostasis refers to all the processes that maintain the correct expression level, location, folding and turnover of proteins, essential to organismal survival. Both inside cells and in body fluids, molecular chaperones play key roles in maintaining proteostasis. In this article, we focus on clusterin, the first-recognized extracellular mammalian chaperone, and its role in diseases of the eye. Clusterin binds to and inhibits the aggregation of proteins that are misfolded due to mutations or stresses, clears these aggregating proteins from extracellular spaces, and facilitates their degradation. Clusterin exhibits three main homeostatic activities: proteostasis, cytoprotection, and anti-inflammation. The so-called "protein misfolding diseases" are caused by aggregation of misfolded proteins that accumulate pathologically as deposits in tissues; we discuss several such diseases that occur in the eye. Clusterin is typically found in these deposits, which is interpreted to mean that its capacity as a molecular chaperone to maintain proteostasis is overwhelmed in the disease state. Nevertheless, the role of clusterin in diseases involving such deposits needs to be better defined before therapeutic approaches can be entertained. A more straightforward case can be made for therapeutic use of clusterin based on its proteostatic role as a proteinase inhibitor, as well as its cytoprotective and anti-inflammatory properties. It is likely that clusterin works together in this way with other extracellular chaperones to protect the eye from disease, and we discuss several examples. We end this article by predicting future steps that may lead to development of clusterin as a biological drug.
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Affiliation(s)
- Mark R Wilson
- Molecular Horizons and the School of Chemistry and Molecular Bioscience, University of Wollongong; Illawarra Health and Medical Research Institute, Northfields Avenue, Wollongong, New South Wales, 2522, Australia.
| | - Sandeep Satapathy
- Molecular Horizons and the School of Chemistry and Molecular Bioscience, University of Wollongong; Illawarra Health and Medical Research Institute, Northfields Avenue, Wollongong, New South Wales, 2522, Australia.
| | - Shinwu Jeong
- USC Roski Eye Institute and Department of Ophthalmology, Keck School of Medicine of USC, University of Southern California, 1333 San Pablo Street., Los Angeles, CA, 90033, USA.
| | - M Elizabeth Fini
- New England Eye Center, Tufts Medical Center and Department of Ophthalmology, Tufts University School of Medicine; Program in Pharmacology & Drug Development, Graduate School of Biomedical Sciences, Tufts University, 800 Washington St, Boston, MA, 02111, USA.
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12
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Scelsi HF, Barlow BM, Saccuzzo EG, Lieberman RL. Common and rare myocilin variants: Predicting glaucoma pathogenicity based on genetics, clinical, and laboratory misfolding data. Hum Mutat 2021; 42:903-946. [PMID: 34082484 DOI: 10.1002/humu.24238] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 05/07/2021] [Accepted: 05/31/2021] [Indexed: 12/12/2022]
Abstract
Rare variants of the olfactomedin domain of myocilin are considered causative for inherited, early-onset open-angle glaucoma, with a misfolding toxic gain-of-function pathogenic mechanism detailed by 20 years of laboratory research. Myocilin variants are documented in the scientific literature and identified through large-scale genetic sequencing projects such as those curated in the Genome Aggregation Database (gnomAD). In the absence of key clinical and laboratory information, however, the pathogenicity of any given variant is not clear, because glaucoma is a heterogeneous and prevalent age-onset disease, and common variants are likely benign. In this review, we reevaluate the likelihood of pathogenicity for the ~100 nonsynonymous missense, insertion-deletion, and premature termination of myocilin olfactomedin variants documented in the literature. We integrate available clinical, laboratory cellular, biochemical and biophysical data, the olfactomedin domain structure, and population genetics data from gnomAD. Of the variants inspected, ~50% can be binned based on a preponderance of data, leaving many of uncertain pathogenicity that motivate additional studies. Ultimately, the approach of combining metrics from different disciplines will likely resolve outstanding complexities regarding the role of this misfolding-prone protein within the context of a multifactorial and prevalent ocular disease, and pave the way for new precision medicine therapeutics.
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Affiliation(s)
- Hailee F Scelsi
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Brett M Barlow
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Emily G Saccuzzo
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
| | - Raquel L Lieberman
- School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, Georgia, USA
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13
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Lieberman RL, Ma MT. Molecular Insights into Myocilin and Its Glaucoma-Causing Misfolded Olfactomedin Domain Variants. Acc Chem Res 2021; 54:2205-2215. [PMID: 33847483 DOI: 10.1021/acs.accounts.1c00060] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Numerous human disorders arise due to the inability of a particular protein to adopt its correct three-dimensional structure in the context of the cell, leading to aggregation. A new addition to the list of such protein conformational disorders is the inherited subtype of glaucoma. Different and rare coding mutations in myocilin, found in families throughout the world, are causal for early onset ocular hypertension, a key glaucoma risk factor. Myocilin is expressed at high levels in the trabecular meshwork (TM) extracellular matrix. The TM is the anatomical region of the eye that regulates intraocular pressure, and its dysfunction is associated with most forms of glaucoma. Disease variants, distributed across the 30 kDa olfactomedin domain (mOLF), cause myocilin to be sequestered intracellularly instead of being secreted to the TM extracellular matrix. The working hypothesis is that the intracellular aggregates cause a toxic gain of function: TM cell death is thought to lead to TM matrix dysfunction, hastening elevated intraocular pressure and subsequent vision loss.Our lab has provided molecular underpinnings for myocilin structure and misfolding, placing myocilin-associated glaucoma within the context of amyloid diseases like Alzheimer and diabetes. We have dissected complexities of the modular wild-type (WT) myocilin structure and associated misfolded states. Our data support the model that full-length WT myocilin adopts a Y-shaped dimer-of-dimers conferred by two different coiled-coil regions, generating new hypotheses regarding its mysterious function. The mOLF β-propellers are paired at each tip of the Y. Disease-associated variants aggregate because mOLFs are less stable, leading to facile aggregation under physiological conditions (37 °C, pH 7.2). Mutant myocilin aggregates exhibit numerous characteristics of amyloid in vitro and in cells, and aggregation proceeds from a partially folded state accessed preferentially by disease variants at physiological conditions. Interestingly, destabilization is not a universal consequence of mutation. We identified counterintuitive, stabilizing point variants that adopt a non-native structure and do not aggregate; however, these variants have not been identified in glaucoma patients. An ongoing effort is predicting the consequence of any given mutation. This effort is relevant to interpreting data from large-scale sequencing projects where clinical and family history data are not available. Finally, our work suggests avenues to develop disease-modifying precision medicines for myocilin-associated glaucoma.
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Affiliation(s)
- Raquel L. Lieberman
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, Georgia 30332-0400, United States
| | - Minh Thu Ma
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 901 Atlantic Dr. NW, Atlanta, Georgia 30332-0400, United States
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14
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Li X, Xiao X, Li S, Sun W, Wang P, Zhang Q. Systemic Genotype-Phenotype Analysis of MYOC Variants Based on Exome Sequencing and Literature Review. Asia Pac J Ophthalmol (Phila) 2021; 10:173-182. [PMID: 33793440 DOI: 10.1097/apo.0000000000000382] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
PURPOSE This study aims to characterize disease-causing variants in the myocilin gene (MYOC), which is associated with autosomal dominant primary open-angle glaucoma (adPOAG). DESIGN Case-control study. METHODS MYOC variants were collected from in-house exome sequencing data of 7092 individuals. Genotype-phenotype analysis and bioinformatics evaluation were used to distinguish potential pathogenic variants for POAG from others. MYOC mutations in published works of literature were also systemically analyzed. RESULTS In total, 53 variants in MYOC were detected in the 7092 subjects, including 45 rare variants (MAF < 0.01) and 8 polymorphisms (MAF ≥ 0.01), or 48 missense variants and 5 truncation variants. There was no difference in the frequency of the 8 polymorphisms between subjects with and without POAG (P > 0.05). The total number of rare MYOC variants was significantly higher in POAG than that in in-house controls (P = 3.31E-14). The pathogenic/likely pathogenic variants (p.P254T, p.S341P, p.G367R, p.P370L, p.D378G, p.C433Y, and p.L486F) were exclusively present in 8 POAG but absent in in-house controls (P = 2.79E-10). Rare truncation MYOC variants were not enriched in POAG as compared with those in in-house controls (P = 0.28). Further analysis of previously reported MYOC variants suggested that pathogenic/likely pathogenic variants were enriched in the conserved olfactomedin domain. Truncation MYOC variants were scattered in the coding region, where only p.Q368∗ had relatively strong evidence to be causative for adPOAG, whereas most others are questionable. CONCLUSIONS Most MYOC variants contributing to adPOAG could be characterized as rare missense variants located in OLF-domain and predicted to be damaging through multiple tools. The effect of other variants, especially for truncation variants (except for p.Q368∗) need further clarification.
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Affiliation(s)
- Xueqing Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, 54 Xianlie Road, Guangzhou, China
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15
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Childhood glaucoma genes and phenotypes: Focus on FOXC1 mutations causing anterior segment dysgenesis and hearing loss. Exp Eye Res 2019; 190:107893. [PMID: 31836490 DOI: 10.1016/j.exer.2019.107893] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 10/16/2019] [Accepted: 12/04/2019] [Indexed: 12/27/2022]
Abstract
Childhood glaucoma is an important cause of blindness world-wide. Eleven genes are currently known to cause inherited forms of glaucoma with onset before age 20. While all the early-onset glaucoma genes cause severe disease, considerable phenotypic variability is observed among mutations carriers. In particular, FOXC1 genetic variants are associated with a broad range of phenotypes including multiple forms of glaucoma and also systemic abnormalities, especially hearing loss. FOXC1 is a member of the forkhead family of transcription factors and is involved in neural crest development necessary for formation of anterior eye structures and also pharyngeal arches that form the middle ear bones. In this study we review the clinical phenotypes reported for known FOXC1 mutations and show that mutations in patients with reported ocular anterior segment abnormalities and hearing loss primarily disrupt the critically important forkhead domain. These results suggest that optimal care for patients affected with anterior segment dysgenesis should include screening for FOXC1 mutations and also testing for hearing loss.
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16
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Sears NC, Boese EA, Miller MA, Fingert JH. Mendelian genes in primary open angle glaucoma. Exp Eye Res 2019; 186:107702. [PMID: 31238079 DOI: 10.1016/j.exer.2019.107702] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 06/11/2019] [Accepted: 06/14/2019] [Indexed: 01/09/2023]
Abstract
Mutations in each of three genes, myocilin (MYOC), optineurin (OPTN), and TANK binding kinase 1 (TBK1), may cause primary open-angle glaucoma (POAG) that is inherited as a Mendelian trait. MYOC mutations cause 3-4% of POAG cases with IOP >21 mmHg, while mutations in OPTN, TBK1, and MYOC each cause ∼1% of POAG with IOP ≤21 mmHg, i.e. normal tension glaucoma. Identification of these disease-causing genes has provided insights into glaucoma pathogenesis. Mutations in MYOC cause a cascade of abnormalities in the trabecular meshwork including intracellular retention of MYOC protein, decreased aqueous outflow, higher intraocular pressure, and glaucoma. Investigation of MYOC mutations demonstrated that abnormal retention of intracellular MYOC and stimulation of endoplasmic reticular (ER) stress may be important steps in the development of MYOC-associated glaucoma. Mutations in OPTN and TBK1 cause a dysregulation of autophagy which may directly cause retinal ganglion cell damage and normal tension glaucoma. Discovery of these Mendelian causes of glaucoma has also provided a new set of potential therapeutic targets that may ultimately lead to novel, gene-directed glaucoma treatments.
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Affiliation(s)
- Nathan C Sears
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Erin A Boese
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - Mathew A Miller
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, USA
| | - John H Fingert
- Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, IA, USA.
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17
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Wang H, Li M, Zhang Z, Xue H, Chen X, Ji Y. Physiological function of myocilin and its role in the pathogenesis of glaucoma in the trabecular meshwork (Review). Int J Mol Med 2018; 43:671-681. [PMID: 30483726 PMCID: PMC6317685 DOI: 10.3892/ijmm.2018.3992] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2018] [Accepted: 11/16/2018] [Indexed: 12/26/2022] Open
Abstract
Myocilin is highly expressed in the trabecular meshwork (TM), which plays an important role in the regulation of intraocular pressure (IOP). Myocilin abnormalities may cause dysfunction of the TM, potentially leading to increased IOP. High IOP is a well‑known primary risk factor for glaucoma. Myocilin mutations are common among glaucoma patients, and they are implicated in juvenile‑onset open‑angle glaucoma (JOAG) and adult‑onset primary open‑angle glaucoma (POAG). Aggregation of aberrant mutant myocilins is closely associated with glaucoma pathogenesis. The aim of the present review was to discuss the recent findings regarding the major physiological functions of myocilin, such as intra‑ and extracellular proteolytic processes. We also aimed to discuss the risk factors associated with myocilin and the development of glaucoma, such as misfolded/mutant myocilin, imbalance of myocilin and extracellular proteins, and instability of mutant myocilin associated with temperature. Finally, we further outlined certain issues that are yet to be resolved, which may represent the basis for future studies on the role of myocilin in glaucoma.
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Affiliation(s)
- Hongwei Wang
- Department of Ophthalmology, Jingjiang People's Hospital, Jingjiang, Jiangsu 214500, P.R. China
| | - Mingzhe Li
- Department of Ophthalmology, Shanghai Pudong Hospital, Fudan University Pudong Medical Center, Shanghai 201399, P.R. China
| | - Zhenzhen Zhang
- Department of Ophthalmology, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200011, P.R. China
| | - Haifeng Xue
- Public Health School, Qiqihar Medical University, Qiqihar, Heilongjiang 161006, P.R. China
| | - Xing Chen
- Department of Science and Education, Jingjiang People's Hospital, Jingjiang, Jiangsu 214500, P.R. China
| | - Yong Ji
- Department of General Surgery, Jingjiang People's Hospital, Jingjiang, Jiangsu 214500, P.R. China
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18
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Wiggs JL, Pasquale LR. Genetics of glaucoma. Hum Mol Genet 2017; 26:R21-R27. [PMID: 28505344 DOI: 10.1093/hmg/ddx184] [Citation(s) in RCA: 217] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 05/08/2017] [Indexed: 12/15/2022] Open
Abstract
Genetic and genomic studies, including genome-wide association studies (GWAS) have accelerated the discovery of genes contributing to glaucoma, the leading cause of irreversible blindness world-wide. Glaucoma can occur at all ages, with Mendelian inheritance typical for the rare early onset disease (before age 40) and complex inheritance evident in common adult-onset forms of disease. Recent studies have suggested possible therapeutic targets for some patients with early-onset glaucoma based on the molecular and cellular events caused by MYOC, OPTN and TBK1 mutations. Diagnostic genetic tests using early-onset glaucoma genes are also proving useful for pre-symptomatic disease detection and genetic counseling. Recent GWAS completed for three types of common adult-onset glaucoma have identified novel loci for POAG (primary-open-angle glaucoma) (ABCA1, AFAP1, GMDS, PMM2, TGFBR3, FNDC3B, ARHGEF12, GAS7, FOXC1, ATXN2, TXNRD2); PACG (primary angle-closure glaucoma (EPDR1, CHAT, GLIS3, FERMT2, DPM2-FAM102); and exfoliation syndrome (XFS) glaucoma (CACNA1A). In total sixteen genomic regions have been associated with POAG (including the normal tension glaucoma (NTG) subgroup), 8 with PACG and 2 with XFS. These studies are defining important biological pathways and processes that contribute to disease pathogenesis.
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Affiliation(s)
- Janey L Wiggs
- Department of Ophthalmology, Harvard Medical School, Massachusetts Eye and Ear, Boston, MA 02114, USA
| | - Louis R Pasquale
- Department of Ophthalmology, Harvard Medical School, Massachusetts Eye and Ear, Boston, MA 02114, USA.,Channing Division of Network Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02114, USA
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19
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Jain A, Zode G, Kasetti RB, Ran FA, Yan W, Sharma TP, Bugge K, Searby CC, Fingert JH, Zhang F, Clark AF, Sheffield VC. CRISPR-Cas9-based treatment of myocilin-associated glaucoma. Proc Natl Acad Sci U S A 2017; 114:11199-11204. [PMID: 28973933 PMCID: PMC5651749 DOI: 10.1073/pnas.1706193114] [Citation(s) in RCA: 108] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Primary open-angle glaucoma (POAG) is a leading cause of irreversible vision loss worldwide, with elevated intraocular pressure (IOP) a major risk factor. Myocilin (MYOC) dominant gain-of-function mutations have been reported in ∼4% of POAG cases. MYOC mutations result in protein misfolding, leading to endoplasmic reticulum (ER) stress in the trabecular meshwork (TM), the tissue that regulates IOP. We use CRISPR-Cas9-mediated genome editing in cultured human TM cells and in a MYOC mouse model of POAG to knock down expression of mutant MYOC, resulting in relief of ER stress. In vivo genome editing results in lower IOP and prevents further glaucomatous damage. Importantly, using an ex vivo human organ culture system, we demonstrate the feasibility of human genome editing in the eye for this important disease.
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Affiliation(s)
- Ankur Jain
- Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
| | - Gulab Zode
- North Texas Eye Research Institute, University of North Texas Health Science Center, Fort Worth, TX 76107;
| | - Ramesh B Kasetti
- North Texas Eye Research Institute, University of North Texas Health Science Center, Fort Worth, TX 76107
| | - Fei A Ran
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA 02142
| | - Winston Yan
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA 02142
| | - Tasneem P Sharma
- Stephen A. Wynn Institute for Vision Research, Department of Ophthalmology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
| | - Kevin Bugge
- Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
| | - Charles C Searby
- Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
| | - John H Fingert
- Stephen A. Wynn Institute for Vision Research, Department of Ophthalmology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
| | - Feng Zhang
- McGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA 02142
| | - Abbot F Clark
- North Texas Eye Research Institute, University of North Texas Health Science Center, Fort Worth, TX 76107
| | - Val C Sheffield
- Department of Pediatrics, Carver College of Medicine, University of Iowa, Iowa City, IA 52242;
- Stephen A. Wynn Institute for Vision Research, Department of Ophthalmology, Carver College of Medicine, University of Iowa, Iowa City, IA 52242
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20
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Fini ME, Schwartz SG, Gao X, Jeong S, Patel N, Itakura T, Price MO, Price FW, Varma R, Stamer WD. Steroid-induced ocular hypertension/glaucoma: Focus on pharmacogenomics and implications for precision medicine. Prog Retin Eye Res 2017; 56:58-83. [PMID: 27666015 PMCID: PMC5237612 DOI: 10.1016/j.preteyeres.2016.09.003] [Citation(s) in RCA: 84] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2016] [Revised: 09/17/2016] [Accepted: 09/19/2016] [Indexed: 02/06/2023]
Abstract
Elevation of intraocular pressure (IOP) due to therapeutic use of glucocorticoids is called steroid-induced ocular hypertension (SIOH); this can lead to steroid-induced glaucoma (SIG). Glucocorticoids initiate signaling cascades ultimately affecting expression of hundreds of genes; this provides the potential for a highly personalized pharmacological response. Studies attempting to define genetic risk factors were undertaken early in the history of glucocorticoid use, however scientific tools available at that time were limited and progress stalled. In contrast, significant advances were made over the ensuing years in defining disease pathophysiology. As the genomics age emerged, it appeared the time was right to renew investigation into genetics. Pharmacogenomics is an unbiased discovery approach, not requiring an underlying hypothesis, and provides a way to pinpoint clinically significant genes and pathways that could not have been discovered any other way. Results of the first genome-wide association study to identify polymorphisms associated with SIOH, and follow-up on two novel genes linked to the disorder, GPR158 and HCG22, is discussed in the second half of the article. However, knowledge of genetic variants determining response to steroids in the eye also has value in its own right as a predictive and diagnostic tool. This article concludes with a discussion of how the Precision Medicine Initiative®, announced by U.S. President Obama in his 2015 State of the Union address, is beginning to touch the practice of ophthalmology. It is argued that SIOH/SIG may provide one of the next opportunities for effective application of precision medicine.
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Affiliation(s)
- M Elizabeth Fini
- USC Institute for Genetic Medicine and Department of Cell & Neurobiology, Keck School of Medicine of USC, University of Southern California, 2250 Alcatraz St., Suite 240, Los Angeles, CA, 90089, USA.
| | - Stephen G Schwartz
- Department of Ophthalmology, Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, 3880 Tamiami Trail North, Naples, FL, 34103, USA.
| | - Xiaoyi Gao
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, 1905 W Taylor St., Suite 235, Chicago, IL, 60612, USA.
| | - Shinwu Jeong
- USC Institute for Genetic Medicine, USC Roski Eye Institute and Department of Ophthalmology, Keck School of Medicine of USC, University of Southern California, 2250 Alcatraz St., Suite 240, Los Angeles, CA, 90089, USA.
| | - Nitin Patel
- USC Institute for Genetic Medicine, Keck School of Medicine of USC, University of Southern California, 2250 Alcatraz St., Suite 240, Los Angeles, CA, 90089, USA.
| | - Tatsuo Itakura
- USC Institute for Genetic Medicine, Keck School of Medicine of USC, University of Southern California, 2250 Alcatraz St., Suite 240, Los Angeles, CA, 90089, USA.
| | - Marianne O Price
- Cornea Research Foundation of America, 9002 North Meridian Street, Indianapolis, IN, 46260, USA.
| | - Francis W Price
- Price Vision Group, 9002 North Meridian Street, Indianapolis, IN, 46260, USA.
| | - Rohit Varma
- Office of the Dean, USC Roski Eye Institute and Department of Ophthalmology, Keck School of Medicine of USC, University of Southern California, 1975 Zonal Ave., KAM 500, Los Angeles, CA, 90089, USA.
| | - W Daniel Stamer
- Department of Ophthalmology and Department of Biomedical Engineering, Duke University, AERI Room 4008, 2351 Erwin Rd, Durham, NC, 27705, USA.
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21
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Kumar S, Malik MA, Goswami S, Sihota R, Kaur J. Candidate genes involved in the susceptibility of primary open angle glaucoma. Gene 2016; 577:119-31. [PMID: 26621382 DOI: 10.1016/j.gene.2015.11.032] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2015] [Revised: 11/05/2015] [Accepted: 11/23/2015] [Indexed: 12/30/2022]
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22
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Wiggs JL. Glaucoma Genes and Mechanisms. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 134:315-42. [PMID: 26310163 DOI: 10.1016/bs.pmbts.2015.04.008] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Genetic studies have yielded important genes contributing to both early-onset and adult-onset forms of glaucoma. The proteins encoded by the current collection of glaucoma genes participate in a broad range of cellular processes and biological systems. Approximately half the glaucoma-related genes function in the extracellular matrix, however proteins involved in cytokine signaling, lipid metabolism, membrane biology, regulation of cell division, autophagy, and ocular development also contribute to the disease pathogenesis. While the function of these proteins in health and disease are not completely understood, recent studies are providing insight into underlying disease mechanisms, a critical step toward the development of gene-based therapies. In this review, genes known to cause early-onset glaucoma or contribute to adult-onset glaucoma are organized according to the cell processes or biological systems that are impacted by the function of the disease-related protein product.
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Affiliation(s)
- Janey L Wiggs
- Harvard Medical School, and Massachusetts Eye and Ear Infirmary, Boston, Massachusetts, USA.
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23
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Abstract
The characterization of genes responsible for glaucoma is the critical first step toward the development of gene-based diagnostic and screening tests, which could identify individuals at risk for disease before irreversible optic nerve damage occurs. Early-onset forms of glaucoma affecting children and young adults are typically inherited as Mendelian autosomal dominant or recessive traits whereas glaucoma affecting older adults has complex inheritance. In this report, we present a comprehensive overview of the genes and genomic regions contributing to inherited glaucoma.
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Affiliation(s)
- Ryan Wang
- Department of Ophthalmology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114
| | - Janey L Wiggs
- Department of Ophthalmology, Harvard Medical School, Massachusetts Eye and Ear Infirmary, Boston, Massachusetts 02114
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24
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Takamoto M, Araie M. Genetics of primary open angle glaucoma. Jpn J Ophthalmol 2013; 58:1-15. [DOI: 10.1007/s10384-013-0286-0] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2013] [Accepted: 09/17/2013] [Indexed: 04/21/2023]
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25
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Kwon HS, Johnson TV, Joe MK, Abu-Asab M, Zhang J, Chan CC, Tomarev SI. Myocilin mediates myelination in the peripheral nervous system through ErbB2/3 signaling. J Biol Chem 2013; 288:26357-71. [PMID: 23897819 DOI: 10.1074/jbc.m112.446138] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The glaucoma-associated gene, myocilin, is expressed in ocular and non-ocular tissues including the peripheral nervous system, but its functions in these tissues remain poorly understood. We demonstrate that in sciatic nerve, myocilin is expressed in Schwann cells with high concentrations at the nodes of Ranvier. There, myocilin interacts with gliomedin, neurofascin, and NrCAM, which are essential for node formation and function. Treatment of isolated dorsal root ganglion cultures with myocilin stimulates clustering of the nodal proteins neurofascin and sodium channel Nav1.2. Sciatic nerves of myocilin null mice express reduced levels of several myelin-associated and basal membrane proteins compared with those of wild-type littermates. They also demonstrate reduced myelin sheath thickness and partial disorganization of the nodes. Myocilin signaling through ErbB2/3 receptors may contribute to these observed effects. Myocilin binds to ErbB2/ErbB3, activates these receptors, and affects the downstream PI3K-AKT signaling pathway. These data implicate a role for myocilin in the development and/or maintenance of myelination and nodes of Ranvier in sciatic nerve.
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Affiliation(s)
- Heung Sun Kwon
- From the Section of Retinal Ganglion Cell Biology, Laboratory of Retinal Cell and Molecular Biology, and
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Souzeau E, Burdon KP, Dubowsky A, Grist S, Usher B, Fitzgerald JT, Crawford A, Hewitt AW, Goldberg I, Mills RA, Ruddle JB, Landers J, Mackey DA, Craig JE. Higher prevalence of myocilin mutations in advanced glaucoma in comparison with less advanced disease in an Australasian disease registry. Ophthalmology 2013; 120:1135-43. [PMID: 23453510 DOI: 10.1016/j.ophtha.2012.11.029] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Revised: 11/14/2012] [Accepted: 11/14/2012] [Indexed: 10/27/2022] Open
Abstract
OBJECTIVES To determine the proportion of all Myocilin coding mutations responsible for advanced primary open-angle glaucoma (POAG) in early-age-at-onset individuals and to investigate the prevalence of exon 3 Myocilin mutations in advanced POAG at any age at onset in a large Australasian cohort. DESIGN Cross-sectional study using a national disease registry. PARTICIPANTS One thousand sixty individuals with advanced POAG (103 with age at onset of 40 years or younger) and 320 with nonadvanced POAG all recruited by the Australian and New Zealand Registry of Advanced Glaucoma. METHODS Participants were examined and referred by their eye practitioner, and Myocilin genetic testing was performed by direct sequencing. Cascade genetic testing was made available for relatives of participants found to carry a Myocilin mutation. MAIN OUTCOME MEASURES Advanced glaucoma diagnosis based on strict visual field entry criteria. Prevalence and spectrum of Myocilin mutations in individuals with advanced and nonadvanced POAG. RESULTS This is the first study to report Myocilin mutations in an advanced POAG cohort. No pathogenic Myocilin mutations were identified in exons 1 and 2 in early-age-at-onset advanced POAG cases. Exon 3 Myocilin mutations were identified in 45 advanced POAG patients (4.2%), which is significantly higher (P = 0.02) compared with nonadvanced POAG patients (1.6%). A novel mutation (Trp373X) and a new variant of uncertain pathogenicity (Ala447Thr) also were reported. The prevalence of Myocilin mutations rose from 16% to 40% in selected advanced POAG subgroups based on different thresholds of maximum recorded intraocular pressure, age at diagnosis, and the presence and strength of positive family history. Twenty-six individuals with Myocilin mutations were identified through cascade genetic testing of first-degree relatives of affected mutation carriers. CONCLUSIONS The prevalence of Myocilin mutations in glaucoma cases with severe visual field loss is significantly greater than in nonadvanced glaucoma patients. Myocilin screening in phenotypically selected cases can have a much higher yield than in previous unselected series. Identifying individuals who have Myocilin mutations provides an opportunity to screen at-risk clinically unaffected relatives and to reduce glaucoma blindness through early management and intervention. FINANCIAL DISCLOSURE(S) The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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Affiliation(s)
- Emmanuelle Souzeau
- Department of Ophthalmology, Flinders University, Flinders Medical Centre, Adelaide, Australia
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Abstract
PURPOSE OF REVIEW To provide an overview of the genetics of the primary open-angle glaucomas with particular attention to congenital, infantile, and juvenile forms. RECENT FINDINGS Mutations in CYP1B1, in addition to being the most common identifiable cause of autosomal recessive primary congenital/infantile glaucoma, can infrequently underlie juvenile and even primary adult-onset open-angle glaucoma, particularly in certain consanguineous populations. In 2009, patients diagnosed with congenital/infantile glaucoma were found to have recessive mutations in a second gene, LTBP2, with a phenotypic spectrum that includes primary megalocornea, spherophakia with ectopia lentis, and lens-related glaucoma. The most common identifiable cause of primary juvenile open-angle glaucoma across most populations remains heterozygous (autosomal dominant) MYOC mutation, underlying up to one-third of cases and possibly sometimes involved in earlier and later onset glaucomas Although primary adult-onset open-angle glaucoma usually does not follow simple Mendelian genetics and is etiologically complex, genome-wide association studies are uncovering genetic susceptibility factors. In some cases, primary adult-onset open-angle glaucoma can be caused by heterozygous mutation in MYOC, OPTN, or WDR36. In addition, in 2009, heterozygous NTF4 mutation was associated with the phenotype in a small percentage of patients from a German cohort. SUMMARY Seemingly unaffected siblings of children with CYP1B1-related primary congenital/infantile glaucoma should undergo genetic testing because of variable expressivity for the phenotype; such testing should also be considered for other asymptomatic relatives, especially in consanguineous families. In western populations, dominant MYOC mutation remains a common cause of primary open-angle juvenile glaucoma and infrequently can be implicated in congenital/infantile or adult-onset forms; identified families should undergo genetic counseling. Primary adult-onset open-angle glaucoma rarely follows simple Mendelian genetics, but genomic studies in different populations are revealing potential genetic risk factors for the phenotype.
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Kwon HS, Tomarev SI. Myocilin, a glaucoma-associated protein, promotes cell migration through activation of integrin-focal adhesion kinase-serine/threonine kinase signaling pathway. J Cell Physiol 2011; 226:3392-402. [PMID: 21656515 DOI: 10.1002/jcp.22701] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The MYOCILIN gene encodes a secreted glycoprotein which is highly expressed in eye drainage structures. Mutations in this gene may lead to juvenile open-angle glaucoma and adult onset primary open-angle glaucoma, one of the leading causes of irreversible blindness in the world. Functions of wild-type myocilin are still unclear. We have recently demonstrated that myocilin is a modulator of Wnt signaling and may affect actin cytoskeleton organization. Here we report that myocilin and its naturally occurring proteolytic fragments, similar to Wnt3a, are able to stimulate trabecular meshwork, NIH3T3, and FHL124 cell migration with the N-terminal proteolytic fragment of myocilin lacking the olfactomedin domain producing the highest stimulatory effect. Stimulation of cell migration occurs through activation of the integrin-focal adhesion kinase (FAK)-serine/threonine kinase (AKT) signaling pathway. Inhibition of FAK by siRNA reduced the stimulatory action of myocilin by threefold. Activation of several components of this signaling pathway was also demonstrated in the eyes of transgenic mice expressing elevated levels of myocilin in the eye drainage structures. These data extend the similarities between actions of myocilin and Wnt proteins acting through a β-catenin-independent mechanism. The modification of the migratory ability of cells by myocilin may play a role in normal functioning of the eye anterior segment and its pathology including glaucoma.
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Affiliation(s)
- Heung Sun Kwon
- Molecular Mechanisms of Glaucoma Section, Laboratory of Molecular and Developmental Biology, National Eye Institute, NIH, Bethesda, Maryland 20892-9303, USA
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Zode GS, Kuehn MH, Nishimura DY, Searby CC, Mohan K, Grozdanic SD, Bugge K, Anderson MG, Clark AF, Stone EM, Sheffield VC. Reduction of ER stress via a chemical chaperone prevents disease phenotypes in a mouse model of primary open angle glaucoma. J Clin Invest 2011; 121:3542-53. [PMID: 21821918 DOI: 10.1172/jci58183] [Citation(s) in RCA: 219] [Impact Index Per Article: 16.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2011] [Accepted: 06/01/2011] [Indexed: 12/11/2022] Open
Abstract
Mutations in myocilin (MYOC) are the most common genetic cause of primary open angle glaucoma (POAG), but the mechanisms underlying MYOC-associated glaucoma are not fully understood. Here, we report the development of a transgenic mouse model of POAG caused by the Y437H MYOC mutation; the mice are referred to herein as Tg-MYOC(Y437H) mice. Analysis of adult Tg-MYOC(Y437H) mice, which we showed express human MYOC containing the Y437H mutation within relevant eye tissues, revealed that they display glaucoma phenotypes (i.e., elevated intraocular pressure [IOP], retinal ganglion cell death, and axonal degeneration) closely resembling those seen in patients with POAG caused by the Y437H MYOC mutation. Mutant myocilin was not secreted into the aqueous humor but accumulated in the ER of the trabecular meshwork (TM), thereby inducing ER stress in the TM of Tg-MYOC(Y437H) mice. Furthermore, chronic and persistent ER stress was found to be associated with TM cell death and elevation of IOP in Tg-MYOC(Y437H) mice. Reduction of ER stress with a chemical chaperone, phenylbutyric acid (PBA), prevented glaucoma phenotypes in Tg-MYOC(Y437H) mice by promoting the secretion of mutant myocilin in the aqueous humor and by decreasing intracellular accumulation of myocilin in the ER, thus preventing TM cell death. These results demonstrate that ER stress is linked to the pathogenesis of POAG and may be a target for treatment in human patients.
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Affiliation(s)
- Gulab S Zode
- Howard Hughes Medical Institute, Department of Pediatrics, College of Medicine, University of Iowa, Iowa City, Iowa 52242, USA
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Menaa F, Braghini CA, Vasconcellos JPCD, Menaa B, Costa VP, Figueiredo ESD, Melo MBD. Keeping an eye on myocilin: a complex molecule associated with primary open-angle glaucoma susceptibility. Molecules 2011; 16:5402-21. [PMID: 21709622 PMCID: PMC6264709 DOI: 10.3390/molecules16075402] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 06/21/2011] [Indexed: 02/04/2023] Open
Abstract
MYOC encodes a secretary glycoprotein of 504 amino acids named myocilin. MYOC is the first gene to be linked to juvenile open-angle glaucoma (JOAG) and some forms of adult-onset primary open-angle glaucoma (POAG). The gene was identified as an up-regulated molecule in cultured trabecular meshwork (TM) cells after treatment with dexamethasone and was originally referred to as trabecular meshwork-inducible glucocorticoid response (TIGR). Elevated intraocular pressure (IOP), due to decreased aqueous outflow, is the strongest known risk factor for POAG. Increasing evidence showed that the modulation of the wild-type (wt) myocilin protein expression is not causative of glaucoma while some misfolded and self-assembly aggregates of mutated myocilin may be associated with POAG in related or unrelated populations. The etiology of the disease remains unclear. Consequently, a better understanding of the molecular mechanisms underlyingPOAG is required to obtain early diagnosis, avoid potential disease progression, and develop new therapeutic strategies. In the present study, we review and discuss the most relevant studies regarding structural characterizations, expressions, molecular interactions, putative functions of MYOC gene and/or its corresponding protein in POAG etiology.
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Affiliation(s)
- Farid Menaa
- Laboratory of Human Genetics, Center for Molecular Biology and Genetic Engineering (CBMEG), University of Campinas (UNICAMP), Campinas-SP 13083-875, Brazil; (C.A.B.); (M.B.D.M.)
- Author to whom correspondence should be addressed; ; or ; Tel.: +55-19-3521-1138; Fax: +55-19-3521-1089
| | - Carolina Ayumi Braghini
- Laboratory of Human Genetics, Center for Molecular Biology and Genetic Engineering (CBMEG), University of Campinas (UNICAMP), Campinas-SP 13083-875, Brazil; (C.A.B.); (M.B.D.M.)
| | - Jose Paulo Cabral De Vasconcellos
- Department of Ophthalmology, Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas-SP 13083-888, Brazil; (J.P.C.D.V.); (V.P.C.); (E.S.D.F.)
| | - Bouzid Menaa
- Department of Chemistry and Nanobiotechnology, Fluorotronics, Inc., San Diego, CA 92081, USA; (B.M.)
| | - Vital Paulino Costa
- Department of Ophthalmology, Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas-SP 13083-888, Brazil; (J.P.C.D.V.); (V.P.C.); (E.S.D.F.)
| | - Eugênio Santana De Figueiredo
- Department of Ophthalmology, Faculty of Medical Sciences, University of Campinas (UNICAMP), Campinas-SP 13083-888, Brazil; (J.P.C.D.V.); (V.P.C.); (E.S.D.F.)
| | - Monica Barbosa De Melo
- Laboratory of Human Genetics, Center for Molecular Biology and Genetic Engineering (CBMEG), University of Campinas (UNICAMP), Campinas-SP 13083-875, Brazil; (C.A.B.); (M.B.D.M.)
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Lim DH, Sohn S, Kim TE, Kee C. Mechanisms Underlying Trabecular Meshwork Cell Death Caused by Mutant Myocilin Expression. JOURNAL OF THE KOREAN OPHTHALMOLOGICAL SOCIETY 2011. [DOI: 10.3341/jkos.2011.52.12.1507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Dong Hui Lim
- Department of Ophthalmology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Seongsoo Sohn
- Department of Ophthalmology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
| | - Tae Eun Kim
- Center for Clinical Research, Samsung Biomedical Research Institute, Seoul, Korea
| | - Changwon Kee
- Department of Ophthalmology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
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Abstract
Glaucoma, a leading cause of blindness worldwide, is characterized by progressive optic nerve damage, usually associated with intraocular pressure. Although the clinical progression of the disease is well defined, the molecular events responsible for glaucoma are currently poorly understood and current therapeutic strategies are not curative. This review summarizes the human genetics and genomic approaches that have shed light on the complex inheritance of glaucoma genes and the potential for gene-based and cellular therapies that this research makes possible.
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Affiliation(s)
- Bao Jian Fan
- Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
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Sohn S, Hur W, Choi YR, Chung YS, Ki CS, Kee C. Little evidence for association of the glaucoma gene MYOC with open-angle glaucoma. Br J Ophthalmol 2010; 94:639-42. [PMID: 20447966 PMCID: PMC2976471 DOI: 10.1136/bjo.2009.158261] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Background/aim To determine if overexpression of the glaucoma gene MYOC is involved in the development of open-angle glaucoma (OAG) and if its promoter variants are associated with glaucoma in the Korean population. Methods Human trabecular meshwork cells were cultured in the presence of ophthalmic steroids such as fluorometholone, fluorometholone acetate, dexamethasone, prednisolone acetate and rimexolone. The cells were cultured at a hydrostatic pressure of 32 mm Hg above atmospheric pressure and induction of MYOC was evaluated by northern blot analysis. Genomic DNA was extracted from blood samples obtained from 74 normal controls and 168 unrelated Korean patients with OAG, including primary OAG, normal tension glaucoma and steroid-induced glaucoma. A 461 base pair (bp) DNA fragment of the MYOC promoter region was amplified using PCR and its genotype was analysed by directly sequencing the product. Results The potencies of steroid eye drops in MYOC induction in vitro was the same regardless of their potential for elevating intraocular pressure in vivo. Hydrostatic pressure had no effect on MYOC induction. A dinucleotide repeat polymorphism and three single nucleotide polymorphisms were identified, but no obvious differences in the genotype distribution and allele frequency of the variants between the control group and any type of OAG were observed. Conclusion Our data suggest that MYOC overexpression is not a cause or an effect of intraocular pressure elevation and that MYOC itself is not associated with OAG.
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Affiliation(s)
- Seongsoo Sohn
- Department of Ophthalmology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul 135-710, South Korea
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Joe MK, Tomarev SI. Expression of myocilin mutants sensitizes cells to oxidative stress-induced apoptosis: implication for glaucoma pathogenesis. THE AMERICAN JOURNAL OF PATHOLOGY 2010; 176:2880-90. [PMID: 20382707 DOI: 10.2353/ajpath.2010.090853] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Mutations in the myocilin gene are associated with juvenile and adult-onset primary open-angle glaucoma. However, the pathogenic mechanisms of myocilin-induced glaucoma are still largely unknown. To investigate these mechanisms, we developed stably transfected HEK293 cell lines expressing wild-type or mutant (Y437H and I477N) myocilins under an inducible promoter. Expression of two mutant myocilins led to different levels of endoplasmic reticulum stress and increased apoptosis after treatment of cells with hydrogen peroxide. The Y437H mutant myocilin cell line showed the highest sensitivity to the oxidant treatment. Several antioxidant genes were down-regulated in the Y437H mutant myocilin cell line, but not in other cell lines. The Y437H mutant myocilin cell line also produced more reactive oxygen species than other cell lines examined. Consistent with the data obtained in cultured cells, the endoplasmic reticulum stress marker, 78 kDa glucose-regulated protein, was up-regulated, whereas antioxidant proteins, paraoxonase 2 and glutathione peroxidase 3, were down-regulated in the eye angle tissue of 18-month-old transgenic mice expressing Y437H myocilin mutant. In addition, a pro-apoptotic factor, CCAAT/enhancer-binding protein-homologous protein, was up-regulated in the aged transgenic mouse angle tissue. Our results suggest that expression of mutated myocilins may have a sensitization effect, which can lead to a severe phenotype in combination with oxidative stress. Mutant myocilins may confer different sensitivity to oxidative stress depending on the mutation.
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Affiliation(s)
- Myung Kuk Joe
- Molecular Mechanisms of Glaucoma Section, Laboratory of Molecular and Developmental Biology, National Eye Institute, National Institutes of Health, 5635 Fishers Lane, Room 1124, Bethesda, MD 20892, USA
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Rautenstrauss B, Mardin C. Targeting glaucoma beyond intraocular pressure. EXPERT REVIEW OF OPHTHALMOLOGY 2010. [DOI: 10.1586/eop.10.21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Li M, Xu J, Chen X, Sun X. RNA interference as a gene silencing therapy for mutant MYOC protein in primary open angle glaucoma. Diagn Pathol 2009; 4:46. [PMID: 20015381 PMCID: PMC2801471 DOI: 10.1186/1746-1596-4-46] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Accepted: 12/16/2009] [Indexed: 11/16/2022] Open
Abstract
Background Primary open-angle glaucoma (POAG) is the most common form of glaucoma which is an irreversible blind leading disease and lacks effective remedies. In recent years, POAG has been linked to the gene MYOC encoding myocilin that has been identified to harbor causal mutations. A variety of studies show that the mutant myocilin acts by gain of function. The mutant MYOC protein induces endoplasmic reticulum (ER) stress and the resultant unfolded protein response (UPR) induces apoptosis in the trabecular meshwork cells, which then leads to an increase in resistance to aqueous humor outflow, elevated intraocular pressure (IOP), and, ultimately, glaucoma. Culturing human trabecular meshwork (HTM) cells at a condition facilitating protein folding promotes secretion of mutant myocilin, normalizes cell morphology and reverses cell lethality. Presentation of the Hypothesis We speculate that a complete elimination of mutant myocilin expression in trabecular meshwork cells is safe and that gives the possibility of avoiding the POAG phenotype. Testing the Hypothesis We propose RNA interference (RNAi) as a gene silencing therapy to eliminate the mutant myocilin proteins in the trabecular meshwork cells, either in a mutation-dependent or mutation-independent way due to the different engineering of the small interfering (si) RNA. Implications of the Hypothesis The RNAi strategy can reverse the pathological process of trabecular meshwork cells and thus treat the POAG caused by myocilin gene mutation. This strategy can also be applicable to many protein-misfolding diseases caused by gain-of-function mutant proteins.
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Affiliation(s)
- Mao Li
- Department of Ophthalmology and Vision Science, Eye and Ear Nose Throat Hospital, Shanghai Medical School, Fudan University, No. 83 Fenyang Road, Shanghai, PR China.
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Puska P, Lemmelä S, Kristo P, Sankila EM, Järvelä I. Penetrance and Phenotype of the Thr377MetMyocilinMutation in a Large Finnish Family with Juvenile- and Adult-Onset Primary Open-Angle Glaucoma. Ophthalmic Genet 2009; 26:17-23. [PMID: 15823921 DOI: 10.1080/13816810590918208] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PURPOSE To study the role of myocilin (MYOC) as a susceptibility gene for juvenile- and adult-onset open-angle glaucoma (JOAG and POAG, respectively). METHODS In a six-generation Finnish family with JOAG and POAG, we performed thorough ophthalmologic characterization (including assessment of the visual fields by Octopus perimetry, nerve-fiber layer thickness by photography, and disc size by Heidelberg tomography) of 51 individuals. The coding region of MYOC was screened for mutations by PCR amplification and direct sequencing. RESULTS We detected a C > T transition at codon 377 resulting in a substitution of a threonine residue for methionine (Thr377Met) in the olfactomedin-like domain of myocilin, segregating in the family. Of the 20 individuals heterozygous for the mutation, nine (45%) were glaucomatous and two (10%) had ocular hypertension (OHT). The mean age at diagnosis of glaucoma in these individuals was 34.3 years (range: 14-66 years). Moreover, three of these individuals suffered retinal vein occlusion (RVO) in one eye, while one individual without the mutation had RVO. CONCLUSION Our results further support the evidence that the Thr377Met mutation in MYOC may represent a susceptibility allele for glaucoma. These findings may facilitate genetic counseling, and early diagnosis and treatment of glaucoma. The possible interaction of factors contributing to RVO in conjunction with the Thr377Met mutation warrants further investigation.
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Affiliation(s)
- Päivi Puska
- Department of Ophthalmology, University of Helsinki, Haarmaninkatu 4C, 00290 Helsinki, Finland.
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Affiliation(s)
- Young H Kwon
- Department of Ophthalmology and Visual Sciences, University of Iowa, Iowa City, USA
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Howell GR, Libby RT, John SWM. Mouse genetic models: an ideal system for understanding glaucomatous neurodegeneration and neuroprotection. PROGRESS IN BRAIN RESEARCH 2009; 173:303-21. [PMID: 18929118 DOI: 10.1016/s0079-6123(08)01122-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/22/2023]
Abstract
Here we review how mouse studies are contributing to understanding glaucoma. We include discussion of aqueous humor drainage and intraocular pressure elevation, because new treatments to avoid exposure to high pressure will indirectly protect neurons from glaucoma, and complement direct neuroprotective strategies. We describe how mouse models are adding to both the understanding of glaucomatous neurodegeneration and the development of neuroprotective strategies.
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Affiliation(s)
- Gareth R Howell
- The Jackson Laboratory, 600 Main Street, Bar Harbor, ME 04609, USA
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Abstract
It is well documented that mutations in the MYOCILIN gene may lead to juvenile- and adult-onset primary open-angle glaucoma. However, the functions of wild-type myocilin are still not well understood. To study the functions of human myocilin and its two proteolytic fragments, these proteins were expressed in HEK293 cells. Conditioned medium from myocilin-expressing cells, as well as purified myocilin, induced the formation of stress fibers in primary cultures of human trabecular meshwork or NIH 3T3 cells. Stress fiber-inducing activity of myocilin was blocked by antibodies against myocilin, as well as secreted inhibitors of Wnt signaling, secreted Frizzled-related protein 1 (sFRP1) or sFRP3, and beta-catenin small interfering RNA. Interaction of myocilin with sFRP1, sFRP3, and several Frizzled receptors was confirmed by immunoprecipitation experiments and by binding of myocilin to the surface of cells expressing cysteine-rich domains of different Frizzled and sFRPs. Treatment of NIH 3T3 cells with myocilin and its fragments induced intracellular redistribution of beta-catenin and its accumulation on the cellular membrane but did not induce nuclear accumulation of beta-catenin. Overexpression of myocilin in the eye angle tissues of transgenic mice stimulated accumulation of beta-catenin in these tissues. Myocilin and Wnt proteins may perform redundant functions in the mammalian eye, since myocilin modulates Wnt signaling by interacting with components of this signaling pathway.
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Wiggs JL. Genes Associated with Human Glaucoma. Ophthalmology 2009. [DOI: 10.1016/b978-0-323-04332-8.00214-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
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Wiggs JL. Molecular Genetics of Selected Ocular Disorders. Ophthalmology 2009. [DOI: 10.1016/b978-0-323-04332-8.00002-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022] Open
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Allingham RR, Liu Y, Rhee DJ. The genetics of primary open-angle glaucoma: a review. Exp Eye Res 2008; 88:837-44. [PMID: 19061886 DOI: 10.1016/j.exer.2008.11.003] [Citation(s) in RCA: 128] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2008] [Revised: 09/26/2008] [Accepted: 11/04/2008] [Indexed: 12/24/2022]
Abstract
Glaucoma is the major cause of irreversible blindness worldwide. Primary open-angle glaucoma (POAG), as the most prevalent form of glaucoma, is a complex inherited disorder and affects more than 2 million individuals in the United States. It has become increasingly clear that a host of genetic as well as environmental factors are likely to contribute to the phenotype. A number of chromosomal and genetic associations have been reported for POAG. This review examines what is currently known about the underlying genetic structure, what remains to be learned, and how this may affect our medical management of this major blinding disease.
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Affiliation(s)
- R Rand Allingham
- Duke University Eye Center, Duke University, Durham, NC 27710, USA.
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Sidjanin DJ, McCarty CA, Patchett R, Smith E, Wilke RA. Pharmacogenetics of ophthalmic topical beta-blockers. Per Med 2008; 5:377-385. [PMID: 19266054 DOI: 10.2217/17410541.5.4.377] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Glaucoma is the second leading cause of blindness worldwide. The primary glaucoma risk factor is elevated intraocular pressure. Topical beta-blockers are affordable and widely used to lower intraocular pressure. Genetic variability has been postulated to contribute to interpersonal differences in efficacy and safety of topical beta-blockers. This review summarizes clinically significant polymorphisms that have been identified in the beta-adrenergic receptors (ADRB1, ADRB2 and ADRB3). The implications of polymorphisms in CYP2D6 are also discussed. Although the candidate-gene approach has facilitated significant progress in our understanding of the genetic basis of glaucoma treatment response, most drug responses involve a large number of genes, each containing multiple polymorphisms. Genome-wide association studies may yield a more comprehensive set of polymorphisms associated with glaucoma outcomes. An understanding of the genetic mechanisms associated with variability in individual responses to topical beta-blockers may advance individualized treatment at a lower cost.
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Affiliation(s)
- Duska J Sidjanin
- Medical College of Wisconsin, Department of Cell Biology, Neurobiology and Anatomy, Milwaukee, WI, USA, Tel.: +1 414 456 7810; ; E-mail:
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Over expression and purification of recombinant human myocilin. World J Microbiol Biotechnol 2008. [DOI: 10.1007/s11274-007-9549-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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Turalba AV, Chen TC. Clinical and genetic characteristics of primary juvenile-onset open-angle glaucoma (JOAG). Semin Ophthalmol 2008; 23:19-25. [PMID: 18214788 DOI: 10.1080/08820530701745199] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
Juvenile-onset open-angle glaucoma (JOAG) is an autosomal dominant disease characterized by an early age of onset and severely elevated intraocular pressures. Large JOAG pedigrees have been pivotal in genetic linkage analyses that have helped establish the association between JOAG and the myocilin gene (MYOC). Numerous disease-causing MYOC mutations have now been identified, and additional loci on other chromosomes have been linked to JOAG. Ongoing molecular genetic studies on myocilin and the search for new gene defects associated with JOAG may offer new directions in our scientific understanding and clinical management of open-angle glaucoma.
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Affiliation(s)
- Angela V Turalba
- Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, MA 02114, USA.
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Shepard AR, Jacobson N, Millar JC, Pang IH, Steely HT, Searby CC, Sheffield VC, Stone EM, Clark AF. Glaucoma-causing myocilin mutants require the Peroxisomal targeting signal-1 receptor (PTS1R) to elevate intraocular pressure. Hum Mol Genet 2007; 16:609-17. [PMID: 17317787 DOI: 10.1093/hmg/ddm001] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Glaucoma is a leading cause of worldwide irreversible visual impairment and blindness and is a clinically and genetically heterogenous group of optic neuropathies. Specific mutations in the myocilin (MYOC) gene cause primary open angle glaucoma (POAG) with varying age-of-onset and degree of severity. We show a mutation-dependent, gain-of-function association between human myocilin and the peroxisomal targeting signal type 1 receptor (PTS1R). There was correlation between the glaucoma phenotype and the specific MYOC mutations, with the more severe early-onset POAG mutations having a higher degree of association with PTS1R. Expression of human myocilin glaucomatous mutations in mouse eyes causes elevated intraocular pressure, which is a major phenotype of MYOC glaucoma. This is the first demonstration of a disease resulting from mutation-induced exposure of a cryptic signaling site that causes mislocalization of mutant protein to peroxisomes and the first disease-gene-based animal model of human POAG.
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Affiliation(s)
- Allan R Shepard
- Glaucoma Research, Alcon Research, Ltd, Fort Worth, TX 76134, USA.
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Hewitt AW, Craig JE, Mackey DA. Complex genetics of complex traits: the case of primary open-angle glaucoma. Clin Exp Ophthalmol 2006; 34:472-84. [PMID: 16872346 DOI: 10.1111/j.1442-9071.2006.01268.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Glaucoma, which is a complex heterogeneous disease, presents an ideal case for genetic investigation. Primary open-angle glaucoma (POAG) is the commonest subtype and will be the focus of this review. When detected early, POAG is amenable to therapeutic intervention. Unfortunately, current population-based clinical screening lacks efficacy. If individuals with a genetic predisposition for developing POAG can be identified, then efficient and cost-effective population-based screening programs could be designed. Although considerable inroads have been made in understanding the natural history of POAG caused by mutations in the myocilin and optineurin genes, other POAG genes accounting for most cases remain to be identified. This review explores the genetic mechanisms that have been unequivocally linked to the glaucomatous process and then discusses potential avenues for future breakthroughs.
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Affiliation(s)
- Alex W Hewitt
- Department of Ophthalmology, Flinders University, Adelaide, South Australia, Australia
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Gobeil S, Letartre L, Raymond V. Functional analysis of the glaucoma-causing TIGR/myocilin protein: Integrity of amino-terminal coiled-coil regions and olfactomedin homology domain is essential for extracellular adhesion and secretion. Exp Eye Res 2006; 82:1017-29. [PMID: 16466712 DOI: 10.1016/j.exer.2005.11.002] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2005] [Revised: 11/11/2005] [Accepted: 11/16/2005] [Indexed: 11/29/2022]
Abstract
TIGR/MYOC mutations account for 2-4% of the primary open-angle glaucoma (POAG) patients. More than 90% of the known mutations are located within its carboxy-terminus olfactomedin-homology (Olf) domain (amino acids (aa) 245-504). In vitro and in vivo studies showed that several Olf domain mutations prevented myocilin secretion. To investigate if intracellular sequestration was a characteristic feature shared by a majority of the mutations, we analyzed the secretion status of 36 myocilin variants. These encompassed 26 glaucoma-causing mutations and 10 non-disease associated or undefined polymorphisms. As several variants were found to be secreted, we tested for their adhesion to the extracellular matrix (ECM) and/or cell surface. Myocilin variants were generated by site-directed mutagenesis of a vector encoding the human MYOC cDNA. COS-7 or immortalized human trabecular meshwork cells were transfected with wild-type or mutated MYOC constructs. Myocilin levels were estimated by immunoprecipitation and/or immunoblotting. All variants showed identical behaviors in both cell lines; the truncated R46X polypeptide being the only variant which could not be detected in our assays. Of the 35 variants monitored, 20 remained sequestered intracellularly. All of them encoded disease-causing polypeptides carrying Olf domain mutations. Of the 15 variants secreted into the culture medium, six (6) were POAG mutants (of which three (3) located within the Olf domain) while the remaining nine (9) were non-disease causing or undefined polymorphisms. Three (3) of the six (6) secreted mutations caused familial POAG; these were the R126W, T377M and A427T mutants. Both, the T377M and A427T mutants located within the Olf domain. When cells were cultured at 30 degrees C, a process known to facilitate protein folding, 11 of the 20 sequestered mutants were released in the extracellular medium. Out of the 15 secreted variants tested for their adhesion to the ECM and/or cell surface, only the R82C and L95P polypeptides displayed loss of their adhesive properties. Deletion experiments revealed that the coiled-coil (aa 78-105) and leucine zipper (aa 114-183) motifs were essential for adhesion. These experiments demonstrate that intracellular sequestration might be the primary mechanism contributing to myocilin-related POAG as it was associated with more than 80% of the disease-causing mutants tested in our study. A second mechanism may involve abnormal interaction(s) between myocilin and ECM and/or cell surface proteins. Our data further revealed the importance of the olfactomedin-homology domain for myocilin secretion and the significant role of the N-terminal region for its extracellular interactions.
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Affiliation(s)
- Stéphane Gobeil
- Laboratory of Ocular Genetics and Genomics, Molecular Endocrinology and Oncology Research Center, Laval University Hospital (CHUL) Research Center, 2705 Laurier Boulevard, Room T3-67, Quebec City, Prov. of Québec, Canada G1V 4G2
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