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Ng ESY, Hu J, Jiang Z, Radu RA. Impaired cathepsin D in retinal pigment epithelium cells mediates Stargardt disease pathogenesis. FASEB J 2024; 38:e23720. [PMID: 38837708 DOI: 10.1096/fj.202400210rr] [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: 01/26/2024] [Revised: 05/12/2024] [Accepted: 05/21/2024] [Indexed: 06/07/2024]
Abstract
Recessive Stargardt disease (STGD1) is an inherited juvenile maculopathy caused by mutations in the ABCA4 gene, for which there is no suitable treatment. Loss of functional ABCA4 in the retinal pigment epithelium (RPE) alone, without contribution from photoreceptor cells, was shown to induce STGD1 pathology. Here, we identified cathepsin D (CatD), the primary RPE lysosomal protease, as a key molecular player contributing to endo-lysosomal dysfunction in STGD1 using a newly developed "disease-in-a-dish" RPE model from confirmed STGD1 patients. Induced pluripotent stem cell (iPSC)-derived RPE originating from three STGD1 patients exhibited elevated lysosomal pH, as previously reported in Abca4-/- mice. CatD protein maturation and activity were impaired in RPE from STGD1 patients and Abca4-/- mice. Consequently, STGD1 RPE cells have reduced photoreceptor outer segment degradation and abnormal accumulation of α-synuclein, the natural substrate of CatD. Furthermore, dysfunctional ABCA4 in STGD1 RPE cells results in intracellular accumulation of autofluorescent material and phosphatidylethanolamine (PE). The altered distribution of PE associated with the internal membranes of STGD1 RPE cells presumably compromises LC3-associated phagocytosis, contributing to delayed endo-lysosomal degradation activity. Drug-mediated re-acidification of lysosomes in the RPE of STGD1 restores CatD functional activity and reduces the accumulation of immature CatD protein loads. This preclinical study validates the contribution of CatD deficiencies to STGD1 pathology and provides evidence for an efficacious therapeutic approach targeting RPE cells. Our findings support a cell-autonomous RPE-driven pathology, informing future research aimed at targeting RPE cells to treat ABCA4-mediated retinopathies.
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Affiliation(s)
- Eunice Sze Yin Ng
- UCLA Stein Eye Institute, University of California, Los Angeles, California, USA
- Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
- Molecular, Cellular, and Integrative Physiology Interdepartmental Program, University of California, Los Angeles, California, USA
| | - Jane Hu
- UCLA Stein Eye Institute, University of California, Los Angeles, California, USA
- Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Zhichun Jiang
- UCLA Stein Eye Institute, University of California, Los Angeles, California, USA
- Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
| | - Roxana A Radu
- UCLA Stein Eye Institute, University of California, Los Angeles, California, USA
- Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, California, USA
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2
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Whelan L, Dockery A, Stephenson KAJ, Zhu J, Kopčić E, Post IJM, Khan M, Corradi Z, Wynne N, O' Byrne JJ, Duignan E, Silvestri G, Roosing S, Cremers FPM, Keegan DJ, Kenna PF, Farrar GJ. Detailed analysis of an enriched deep intronic ABCA4 variant in Irish Stargardt disease patients. Sci Rep 2023; 13:9380. [PMID: 37296172 PMCID: PMC10256698 DOI: 10.1038/s41598-023-35889-9] [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: 05/17/2022] [Accepted: 05/25/2023] [Indexed: 06/12/2023] Open
Abstract
Over 15% of probands in a large cohort of more than 1500 inherited retinal degeneration patients present with a clinical diagnosis of Stargardt disease (STGD1), a recessive form of macular dystrophy caused by biallelic variants in the ABCA4 gene. Participants were clinically examined and underwent either target capture sequencing of the exons and some pathogenic intronic regions of ABCA4, sequencing of the entire ABCA4 gene or whole genome sequencing. ABCA4 c.4539 + 2028C > T, p.[= ,Arg1514Leufs*36] is a pathogenic deep intronic variant that results in a retina-specific 345-nucleotide pseudoexon inclusion. Through analysis of the Irish STGD1 cohort, 25 individuals across 18 pedigrees harbour ABCA4 c.4539 + 2028C > T and another pathogenic variant. This includes, to the best of our knowledge, the only two homozygous patients identified to date. This provides important evidence of variant pathogenicity for this deep intronic variant, highlighting the value of homozygotes for variant interpretation. 15 other heterozygous incidents of this variant in patients have been reported globally, indicating significant enrichment in the Irish population. We provide detailed genetic and clinical characterization of these patients, illustrating that ABCA4 c.4539 + 2028C > T is a variant of mild to intermediate severity. These results have important implications for unresolved STGD1 patients globally with approximately 10% of the population in some western countries claiming Irish heritage. This study exemplifies that detection and characterization of founder variants is a diagnostic imperative.
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Affiliation(s)
- Laura Whelan
- The School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland.
| | - Adrian Dockery
- The School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland
- Next Generation Sequencing Laboratory, Pathology Department, The Mater Misericordiae University Hospital, Dublin 7, Ireland
| | - Kirk A J Stephenson
- Department of Ophthalmology, Royal Victoria Eye and Ear Hospital, Dublin 2, Ireland
- Mater Clinical Ophthalmic Genetics Unit, The Mater Misericordiae University Hospital, Dublin 7, Ireland
| | - Julia Zhu
- Mater Clinical Ophthalmic Genetics Unit, The Mater Misericordiae University Hospital, Dublin 7, Ireland
| | - Ella Kopčić
- The School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland
| | - Iris J M Post
- The School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland
| | - Mubeen Khan
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
- Language and Genetics Department, Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands
- International Max Planck Research School for Language Sciences, Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands
| | - Zelia Corradi
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
- Academic Alliance Genetics, Radboud University Medical Center, Nijmegen, and Maastricht University Medical Center+, Maastricht, The Netherlands
| | - Niamh Wynne
- Department of Ophthalmology, Royal Victoria Eye and Ear Hospital, Dublin 2, Ireland
| | - James J O' Byrne
- Mater Clinical Ophthalmic Genetics Unit, The Mater Misericordiae University Hospital, Dublin 7, Ireland
- International Max Planck Research School for Language Sciences, Max Planck Institute for Psycholinguistics, Nijmegen, The Netherlands
- National Centre for Inherited Metabolic Disorders, The Mater Misericordiae University Hospital, Dublin 7, Ireland
- School of Medicine, Trinity College Dublin, Dublin 2, Ireland
| | - Emma Duignan
- Department of Ophthalmology, Royal Victoria Eye and Ear Hospital, Dublin 2, Ireland
| | - Giuliana Silvestri
- Centre for Experimental Medicine, Queen's University Belfast, Belfast, Northern Ireland, UK
- School of Medicine, University College Dublin, Dublin 4, Ireland
- Department of Ophthalmology, The Royal Victoria Hospital, Belfast, Northern Ireland, UK
| | - Susanne Roosing
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
- Academic Alliance Genetics, Radboud University Medical Center, Nijmegen, and Maastricht University Medical Center+, Maastricht, The Netherlands
| | - Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
- Academic Alliance Genetics, Radboud University Medical Center, Nijmegen, and Maastricht University Medical Center+, Maastricht, The Netherlands
| | - David J Keegan
- Mater Clinical Ophthalmic Genetics Unit, The Mater Misericordiae University Hospital, Dublin 7, Ireland
| | - Paul F Kenna
- The School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland
- Department of Ophthalmology, Royal Victoria Eye and Ear Hospital, Dublin 2, Ireland
| | - G Jane Farrar
- The School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland
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3
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Ng ESY, Kady N, Hu J, Dave A, Jiang Z, Pei J, Gorin MB, Matynia A, Radu RA. Membrane Attack Complex Mediates Retinal Pigment Epithelium Cell Death in Stargardt Macular Degeneration. Cells 2022; 11:3462. [PMID: 36359858 PMCID: PMC9655712 DOI: 10.3390/cells11213462] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2022] [Revised: 10/28/2022] [Accepted: 10/30/2022] [Indexed: 08/22/2023] Open
Abstract
Recessive Stargardt disease (STGD1) is an inherited retinopathy caused by mutations in the ABCA4 gene. The ABCA4 protein is a phospholipid-retinoid flippase in the outer segments of photoreceptors and the internal membranes of retinal pigment epithelial (RPE) cells. Here, we show that RPE cells derived via induced pluripotent stem-cell from a molecularly and clinically diagnosed STGD1 patient exhibited reduced ABCA4 protein and diminished activity compared to a normal subject. Consequently, STGD1 RPE cells accumulated intracellular autofluorescence-lipofuscin and displayed increased complement C3 activity. The level of C3 inversely correlated with the level of CD46, an early negative regulator of the complement cascade. Persistent complement dysregulation led to deposition of the membrane attack complex on the surface of RPE cells, decrease in transepithelial resistance, and subsequent cell death. These findings are strong evidence of complement-mediated RPE cell damage in STGD1, in the absence of photoreceptors, caused by reduced CD46 regulatory protein.
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Affiliation(s)
- Eunice Sze Yin Ng
- UCLA Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, CA 90095, USA
- Molecular Cellular and Integrative Physiology Interdepartmental Program, University of California, Los Angeles, CA 90095, USA
| | - Nermin Kady
- UCLA Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, CA 90095, USA
- Department of Internal Medicine, Division of Hematology and Oncology, University of Michigan, Ann Arbor, MI 48109, USA
- Clinical Pathology Department, Faculty of Medicine, Mansoura University, Mansoura 35516, Egypt
| | - Jane Hu
- UCLA Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, CA 90095, USA
| | - Arpita Dave
- UCLA Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, CA 90095, USA
| | - Zhichun Jiang
- UCLA Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, CA 90095, USA
| | - Jacqueline Pei
- UCLA Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, CA 90095, USA
| | - Michael B. Gorin
- UCLA Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, CA 90095, USA
| | - Anna Matynia
- UCLA Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, CA 90095, USA
| | - Roxana A. Radu
- UCLA Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, University of California at Los Angeles, CA 90095, USA
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Hall JC, Paull D, Pébay A, Lidgerwood GE. Human pluripotent stem cells for the modelling of retinal pigment epithelium homeostasis and disease: A review. Clin Exp Ophthalmol 2022; 50:667-677. [PMID: 35739648 PMCID: PMC9546239 DOI: 10.1111/ceo.14128] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2022] [Revised: 06/06/2022] [Accepted: 06/19/2022] [Indexed: 12/05/2022]
Abstract
Human pluripotent stem cells (hPSCs), which include induced pluripotent stem cells and embryonic stem cells, are powerful tools for studying human development, physiology and disease, including those affecting the retina. Cells from selected individuals, or specific genetic backgrounds, can be differentiated into distinct cell types allowing the modelling of diseases in a dish for therapeutic development. hPSC‐derived retinal cultures have already been used to successfully model retinal pigment epithelium (RPE) degeneration for various retinal diseases including monogenic conditions and complex disease such as age‐related macular degeneration. Here, we will review the current knowledge gained in understanding the molecular events involved in retinal disease using hPSC‐derived retinal models, in particular RPE models. We will provide examples of various conditions to illustrate the scope of applications associated with the use of hPSC‐derived RPE models.
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Affiliation(s)
- Jenna C Hall
- Department of Anatomy and Physiology The University of Melbourne Parkville Victoria Australia
| | - Daniel Paull
- The New York Stem Cell Foundation Research Institute New York New York USA
| | - Alice Pébay
- Department of Anatomy and Physiology The University of Melbourne Parkville Victoria Australia
- Department of Surgery, Royal Melbourne Hospital The University of Melbourne Parkville Victoria Australia
| | - Grace E. Lidgerwood
- Department of Anatomy and Physiology The University of Melbourne Parkville Victoria Australia
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