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Zaydon YA, Tsang SH. The ABCs of Stargardt disease: the latest advances in precision medicine. Cell Biosci 2024; 14:98. [PMID: 39060921 PMCID: PMC11282698 DOI: 10.1186/s13578-024-01272-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2023] [Accepted: 07/01/2024] [Indexed: 07/28/2024] Open
Abstract
Stargardt disease (STGD) is the most common form of inherited juvenile macular dystrophy and is caused by sequence variants in the ABCA4 gene. Due to its genetic complexity and phenotypic variability, STGD poses significant therapeutic challenges. In the past decade, a lot of progress has been made regarding our understanding of the molecular and clinical aspects of STGD, along with its mechanisms. This has led to the development of new therapies, and there are human clinical trials currently ongoing. This paper evaluates the emergence of pharmacological approaches targeting the visual cycle to mitigate retinal damage, the role of gene therapy in correcting specific genetic defects, and the use of stem cell therapies aimed at retinal regeneration by showcasing the latest clinical trials and precision medicine approaches.
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Affiliation(s)
- Yasmine A Zaydon
- Departments of Ophthalmology, Pathology and Cell Biology, Jonas Children's Vision Care, and Bernard and Shirlee Brown Glaucoma Laboratory, Columbia Stem Cell Initiative, Institute of Human Nutrition, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA.
| | - Stephen H Tsang
- Departments of Ophthalmology, Pathology and Cell Biology, Jonas Children's Vision Care, and Bernard and Shirlee Brown Glaucoma Laboratory, Columbia Stem Cell Initiative, Institute of Human Nutrition, Vagelos College of Physicians and Surgeons, Columbia University, New York, NY, USA
- Edward S. Harkness Eye Institute, New York-Presbyterian Hospital, New York, NY, USA
- Department of Pathology and Cell Biology, The Herbert Irving Comprehensive Cancer Center, Institute of Human Nutrition, Columbia University, New York, NY, USA
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2
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Corradi Z, Dhaenens CM, Grunewald O, Kocabaş IS, Meunier I, Banfi S, Karali M, Cremers FPM, Hitti-Malin RJ. Novel and Recurrent Copy Number Variants in ABCA4-Associated Retinopathy. Int J Mol Sci 2024; 25:5940. [PMID: 38892127 PMCID: PMC11173210 DOI: 10.3390/ijms25115940] [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: 04/22/2024] [Revised: 05/22/2024] [Accepted: 05/24/2024] [Indexed: 06/21/2024] Open
Abstract
ABCA4 is the most frequently mutated gene leading to inherited retinal disease (IRD) with over 2200 pathogenic variants reported to date. Of these, ~1% are copy number variants (CNVs) involving the deletion or duplication of genomic regions, typically >50 nucleotides in length. An in-depth assessment of the current literature based on the public database LOVD, regarding the presence of known CNVs and structural variants in ABCA4, and additional sequencing analysis of ABCA4 using single-molecule Molecular Inversion Probes (smMIPs) for 148 probands highlighted recurrent and novel CNVs associated with ABCA4-associated retinopathies. An analysis of the coverage depth in the sequencing data led to the identification of eleven deletions (six novel and five recurrent), three duplications (one novel and two recurrent) and one complex CNV. Of particular interest was the identification of a complex defect, i.e., a 15.3 kb duplicated segment encompassing exon 31 through intron 41 that was inserted at the junction of a downstream 2.7 kb deletion encompassing intron 44 through intron 47. In addition, we identified a 7.0 kb tandem duplication of intron 1 in three cases. The identification of CNVs in ABCA4 can provide patients and their families with a genetic diagnosis whilst expanding our understanding of the complexity of diseases caused by ABCA4 variants.
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Affiliation(s)
- Zelia Corradi
- Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Claire-Marie Dhaenens
- Université de Lille, Inserm, CHU Lille, U1172-LilNCog-Lille Neuroscience & Cognition, F-59000 Lille, France
| | - Olivier Grunewald
- Université de Lille, Inserm, CHU Lille, U1172-LilNCog-Lille Neuroscience & Cognition, F-59000 Lille, France
| | - Ipek Selen Kocabaş
- Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Isabelle Meunier
- Institute des Neurosciences de Montpellier, INSERM, Université de Montpellier, F-34295 Montpellier, France
| | - Sandro Banfi
- Department of Precision Medicine, University of Campania “Luigi Vanvitelli”, 81031 Naples, Italy
- Telethon Institute of Genetics and Medicine (TIGEM), 80078 Pozzuoli, Italy
| | - Marianthi Karali
- Department of Precision Medicine, University of Campania “Luigi Vanvitelli”, 81031 Naples, Italy
- Eye Clinic, Multidisciplinary Department of Medical, Surgical and Dental Sciences, University of Campania “Luigi Vanvitelli”, 81031 Naples, Italy
| | - Frans P. M. Cremers
- Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
| | - Rebekkah J. Hitti-Malin
- Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, The Netherlands
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3
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Corradi Z, Hitti-Malin RJ, de Rooij LA, Garanto A, Collin RWJ, Cremers FPM. Antisense Oligonucleotide-Based Rescue of Complex Intronic Splicing Defects in ABCA4. Nucleic Acid Ther 2024; 34:125-133. [PMID: 38800942 DOI: 10.1089/nat.2024.0008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/29/2024] Open
Abstract
The ABCA4 gene, involved in Stargardt disease, has a high percentage of splice-altering pathogenic variants, some of which cause complex RNA defects. Although antisense oligonucleotides (AONs) have shown promising results in splicing modulation, they have not yet been used to target complex splicing defects. Here, we performed AON-based rescue studies on ABCA4 complex splicing defects. Intron 13 variants c.1938-724A>G, c.1938-621G>A, c.1938-619A>G, and c.1938-514A>G all lead to the inclusion of different pseudo-exons (PEs) with and without an upstream PE (PE1). Intron 44 variant c.6148-84A>T results in multiple PE inclusions and/or exon skipping events. Five novel AONs were designed to target these defects. AON efficacy was assessed by in vitro splice assays using midigenes containing the variants of interest. All screened complex splicing defects were effectively rescued by the AONs. Although varying levels of efficacy were observed between AONs targeting the same PEs, for all variants at least one AON restored splicing to levels comparable or better than wildtype. In conclusion, AONs are a promising approach to target complex splicing defects in ABCA4.
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Affiliation(s)
- Zelia Corradi
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Rebekkah J Hitti-Malin
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Laura A de Rooij
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Alejandro Garanto
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Pediatrics, Amalia Children's Hospital, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Rob W J Collin
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, The Netherlands
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Engfer ZJ, Lewandowski D, Dong Z, Palczewska G, Zhang J, Kordecka K, Płaczkiewicz J, Panas D, Foik AT, Tabaka M, Palczewski K. Distinct mouse models of Stargardt disease display differences in pharmacological targeting of ceramides and inflammatory responses. Proc Natl Acad Sci U S A 2023; 120:e2314698120. [PMID: 38064509 PMCID: PMC10723050 DOI: 10.1073/pnas.2314698120] [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: 08/24/2023] [Accepted: 10/25/2023] [Indexed: 12/17/2023] Open
Abstract
Mutations in many visual cycle enzymes in photoreceptors and retinal pigment epithelium (RPE) cells can lead to the chronic accumulation of toxic retinoid byproducts, which poison photoreceptors and the underlying RPE if left unchecked. Without a functional ATP-binding cassette, sub-family A, member 4 (ABCA4), there is an elevation of all-trans-retinal and prolonged buildup of all-trans-retinal adducts, resulting in a retinal degenerative disease known as Stargardt-1 disease. Even in this monogenic disorder, there is significant heterogeneity in the time to onset of symptoms among patients. Using a combination of molecular techniques, we studied Abca4 knockout (simulating human noncoding disease variants) and Abca4 knock-in mice (simulating human misfolded, catalytically inactive protein variants), which serve as models for Stargardt-1 disease. We compared the two strains to ascertain whether they exhibit differential responses to agents that affect cytokine signaling and/or ceramide metabolism, as alterations in either of these pathways can exacerbate retinal degenerative phenotypes. We found different degrees of responsiveness to maraviroc, a known immunomodulatory CCR5 antagonist, and to the ceramide-lowering agent AdipoRon, an agonist of the ADIPOR1 and ADIPOR2 receptors. The two strains also display different degrees of transcriptional deviation from matched WT controls. Our phenotypic comparison of the two distinct Abca4 mutant-mouse models sheds light on potential therapeutic avenues previously unexplored in the treatment of Stargardt disease and provides a surrogate assay for assessing the effectiveness for genome editing.
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Affiliation(s)
- Zachary J. Engfer
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, CA92697
- Department of Physiology and Biophysics, University of California, Irvine, CA92697
| | - Dominik Lewandowski
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, CA92697
| | - Zhiqian Dong
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, CA92697
| | - Grazyna Palczewska
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, CA92697
| | - Jianye Zhang
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, CA92697
| | - Katarzyna Kordecka
- Ophthalmic Biology Group, International Centre for Translational Eye Research, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw01-224, Poland
| | - Jagoda Płaczkiewicz
- Ophthalmic Biology Group, International Centre for Translational Eye Research, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw01-224, Poland
| | - Damian Panas
- International Centre for Translational Eye Research, Warsaw01-224, Poland
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw01-224, Poland
| | - Andrzej T. Foik
- Ophthalmic Biology Group, International Centre for Translational Eye Research, Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw01-224, Poland
| | - Marcin Tabaka
- International Centre for Translational Eye Research, Warsaw01-224, Poland
- Institute of Physical Chemistry, Polish Academy of Sciences, Warsaw01-224, Poland
| | - Krzysztof Palczewski
- Gavin Herbert Eye Institute, Department of Ophthalmology, University of California, Irvine, CA92697
- Department of Physiology and Biophysics, University of California, Irvine, CA92697
- Department of Chemistry, University of California, Irvine, CA92697
- Department of Molecular Biology and Biochemistry, University of California, Irvine, CA92697
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Castiglione GM, Chiu YLI, Gutierrez EDA, Van Nynatten A, Hauser FE, Preston M, Bhattacharyya N, Schott RK, Chang BSW. Convergent evolution of dim light vision in owls and deep-diving whales. Curr Biol 2023; 33:4733-4740.e4. [PMID: 37776863 DOI: 10.1016/j.cub.2023.09.015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2023] [Revised: 08/21/2023] [Accepted: 09/05/2023] [Indexed: 10/02/2023]
Abstract
Animals with enhanced dim-light sensitivity are at higher risk of light-induced retinal degeneration when exposed to bright light conditions.1,2,3,4 This trade-off is mediated by the rod photoreceptor sensory protein, rhodopsin (RHO), and its toxic vitamin A chromophore by-product, all-trans retinal.5,6,7,8 Rod arrestin (Arr-1) binds to RHO and promotes sequestration of excess all-trans retinal,9,10 which has recently been suggested as a protective mechanism against photoreceptor cell death.2,11 We investigated Arr-1 evolution in animals at high risk of retinal damage due to periodic bright-light exposure of rod-dominated retinas. Here, we find the convergent evolution of enhanced Arr-1/RHO all-trans-retinal sequestration in owls and deep-diving whales. Statistical analyses reveal a parallel acceleration of Arr-1 evolutionary rates in these lineages, which is associated with the introduction of a rare Arr-1 mutation (Q69R) into the RHO-Arr-1 binding interface. Using in vitro assays, we find that this single mutation significantly enhances RHO-all-trans-retinal sequestration by ∼30%. This functional convergence across 300 million years of evolutionary divergence suggests that Arr-1 and RHO may play an underappreciated role in the photoprotection of the eye, with potentially vast clinical significance.
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Affiliation(s)
- Gianni M Castiglione
- Department of Biological Sciences, Vanderbilt University, Nashville, TN 37232, USA; Department of Ophthalmology & Visual Sciences, Vanderbilt University, Nashville, TN 37232, USA; Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada; Evolutionary Studies, Vanderbilt University, Nashville, TN 37235, USA.
| | - Yan L I Chiu
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Eduardo de A Gutierrez
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada
| | - Alexander Van Nynatten
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada
| | - Frances E Hauser
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada; Department of Biological Sciences, University of Toronto Scarborough, Toronto, ON M1C 1A4, Canada
| | - Matthew Preston
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada
| | - Nihar Bhattacharyya
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Institute of Ophthalmology, University College London, London EC1V 2PD, UK
| | - Ryan K Schott
- Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada; Department of Biology and Centre for Vision Research, York University, Toronto, ON M3J 1P3, Canada; Department of Vertebrate Zoology, National Museum of Natural History, Smithsonian Institution, Washington, DC 20560, USA
| | - Belinda S W Chang
- Department of Cell & Systems Biology, University of Toronto, Toronto, ON M5S 3G5, Canada; Department of Ecology & Evolutionary Biology, University of Toronto, Toronto, ON M5S 3B2, Canada.
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Corradi Z, Khan M, Hitti-Malin R, Mishra K, Whelan L, Cornelis SS, Hoyng CB, Kämpjärvi K, Klaver CCW, Liskova P, Stöhr H, Weber BHF, Banfi S, Farrar GJ, Sharon D, Zernant J, Allikmets R, Dhaenens CM, Cremers FPM. Targeted sequencing and in vitro splice assays shed light on ABCA4-associated retinopathies missing heritability. HGG ADVANCES 2023; 4:100237. [PMID: 37705246 PMCID: PMC10534262 DOI: 10.1016/j.xhgg.2023.100237] [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: 06/05/2023] [Revised: 09/07/2023] [Accepted: 09/08/2023] [Indexed: 09/15/2023] Open
Abstract
The ABCA4 gene is the most frequently mutated Mendelian retinopathy-associated gene. Biallelic variants lead to a variety of phenotypes, however, for thousands of cases the underlying variants remain unknown. Here, we aim to shed further light on the missing heritability of ABCA4-associated retinopathy by analyzing a large cohort of macular dystrophy probands. A total of 858 probands were collected from 26 centers, of whom 722 carried no or one pathogenic ABCA4 variant, while 136 cases carried two ABCA4 alleles, one of which was a frequent mild variant, suggesting that deep-intronic variants (DIVs) or other cis-modifiers might have been missed. After single molecule molecular inversion probes (smMIPs)-based sequencing of the complete 128-kb ABCA4 locus, the effect of putative splice variants was assessed in vitro by midigene splice assays in HEK293T cells. The breakpoints of copy number variants (CNVs) were determined by junction PCR and Sanger sequencing. ABCA4 sequence analysis solved 207 of 520 (39.8%) naive or unsolved cases and 70 of 202 (34.7%) monoallelic cases, while additional causal variants were identified in 54 of 136 (39.7%) probands carrying two variants. Seven novel DIVs and six novel non-canonical splice site variants were detected in a total of 35 alleles and characterized, including the c.6283-321C>G variant leading to a complex splicing defect. Additionally, four novel CNVs were identified and characterized in five alleles. These results confirm that smMIPs-based sequencing of the complete ABCA4 gene provides a cost-effective method to genetically solve retinopathy cases and that several rare structural and splice altering defects remain undiscovered in Stargardt disease cases.
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Affiliation(s)
- Zelia Corradi
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands.
| | - Mubeen Khan
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands; Max Planck Institute for Psycholinguistics, Nijmegen, the Netherlands
| | - Rebekkah Hitti-Malin
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Ketan Mishra
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Laura Whelan
- The School of Genetics & Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Stéphanie S Cornelis
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Carel B Hoyng
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, the Netherlands
| | | | - Caroline C W Klaver
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, the Netherlands; Department of Epidemiology, Erasmus Medical Center, Rotterdam, the Netherlands; Department of Ophthalmology, Erasmus Medical Center, Rotterdam, the Netherlands; Institute of Molecular & Clinical Ophthalmology, Basel, Switzerland
| | - Petra Liskova
- Research Unit for Rare Diseases, Department of Paediatrics and Adolescent Medicine, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic; Department of Ophthalmology, First Faculty of Medicine, Charles University and General University Hospital in Prague, Prague, Czech Republic
| | - Heidi Stöhr
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Bernhard H F Weber
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany; Institute of Clinical Human Genetics, University Hospital Regensburg, Regensburg, Germany
| | - Sandro Banfi
- Department of Precision Medicine, University of Campania "Luigi Vanvitelli," Naples and Telethon Institute of Genetics and Medicine (TIGEM), Pozzuoli, Italy
| | - G Jane Farrar
- The School of Genetics & Microbiology, Trinity College Dublin, Dublin, Ireland
| | - Dror Sharon
- Department of Ophthalmology, Hadassah Medical Center, Faculty of Medicine, The Hebrew University of Jerusalem, Jerusalem, Israel
| | - Jana Zernant
- Department of Ophthalmology, Columbia University, New York, NY, USA
| | - Rando Allikmets
- Department of Ophthalmology, Columbia University, New York, NY, USA; Department of Pathology & Cell Biology, Columbia University, New York, NY, USA
| | - Claire-Marie Dhaenens
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands; University Lille, Inserm, CHU Lille, U1172 - LilNCog - Lille Neuroscience & Cognition, 59000 Lille, France
| | - Frans P M Cremers
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
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Sajovic J, Meglič A, Corradi Z, Khan M, Maver A, Vidmar MJ, Hawlina M, Cremers FPM, Fakin A. ABCA4 Variant c.5714+5G>A in Trans With Null Alleles Results in Primary RPE Damage. Invest Ophthalmol Vis Sci 2023; 64:33. [PMID: 37728905 PMCID: PMC10516765 DOI: 10.1167/iovs.64.12.33] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Accepted: 08/30/2023] [Indexed: 09/22/2023] Open
Abstract
Purpose To determine the disease pathogenesis associated with the frequent ABCA4 variant c.5714+5G>A (p.[=,Glu1863Leufs*33]). Methods Patient-derived photoreceptor precursor cells were generated to analyze the effect of c.5714+5G>A on splicing and perform a quantitative analysis of c.5714+5G>A products. Patients with c.5714+5G>A in trans with a null allele (i.e., c.5714+5G>A patients; n = 7) were compared with patients with two null alleles (i.e., double null patients; n = 11); with a special attention to the degree of RPE atrophy (area of definitely decreased autofluorescence and the degree of photoreceptor impairment (outer nuclear layer thickness and pattern electroretinography amplitude). Results RT-PCR of mRNA from patient-derived photoreceptor precursor cells showed exon 40 and exon 39/40 deletion products, as well as the normal transcript. Quantification of products showed 52.4% normal and 47.6% mutant ABCA4 mRNA. Clinically, c.5714+5G>A patients displayed significantly better structural and functional preservation of photoreceptors (thicker outer nuclear layer, presence of tubulations, higher pattern electroretinography amplitude) than double null patients with similar degrees of RPE loss, whereas double null patients exhibited signs of extensive photoreceptor ,damage even in the areas with preserved RPE. Conclusions The prototypical STGD1 sequence of events of primary RPE and secondary photoreceptor damage is congruous with c.5714+5G>A, but not the double null genotype, which implies different and genotype-dependent disease mechanisms. We hypothesize that the relative photoreceptor sparing in c.5714+5G>A patients results from the remaining function of the ABCA4 transporter originating from the normally spliced product, possibly by decreasing the direct bisretinoid toxicity on photoreceptor membranes.
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Affiliation(s)
- Jana Sajovic
- Eye Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Andrej Meglič
- Eye Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia
| | - Zelia Corradi
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, the Netherlands
| | - Mubeen Khan
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, the Netherlands
- Max Planck Institute for Psycholinguistics, Nijmegen, the Netherlands
| | - Aleš Maver
- Clinical Institute of Genomic Medicine, University Medical Centre Ljubljana, Ljubljana, Slovenia
| | - Martina Jarc Vidmar
- Eye Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Marko Hawlina
- Eye Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Frans P. M. Cremers
- Department of Human Genetics, Radboud University Medical Center, Nijmegen, the Netherlands
- Donders Institute for Brain, Cognition and Behaviour, Radboud University, Nijmegen, the Netherlands
| | - Ana Fakin
- Eye Hospital, University Medical Centre Ljubljana, Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
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Watson A, Lako M. Retinal organoids provide unique insights into molecular signatures of inherited retinal disease throughout retinogenesis. J Anat 2023; 243:186-203. [PMID: 36177499 PMCID: PMC10335378 DOI: 10.1111/joa.13768] [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: 06/17/2022] [Revised: 09/06/2022] [Accepted: 09/06/2022] [Indexed: 10/14/2022] Open
Abstract
The demand for induced pluripotent stem cells (iPSC)-derived retinal organoid and retinal pigment epithelium (RPE) models for the modelling of inherited retinopathies has increased significantly in the last decade. These models are comparable with foetal retinas up until the later stages of retinogenesis, expressing all of the key neuronal markers necessary for retinal function. These models have proven to be invaluable in the understanding of retinogenesis, particular in the context of patient-specific diseases. Inherited retinopathies are infamously described as clinically and phenotypically heterogeneous, such that developing gene/mutation-specific animal models in each instance of retinal disease is not financially or ethically feasible. Further to this, many animal models are insufficient in the study of disease pathogenesis due to anatomical differences and failure to recapitulate human disease phenotypes. In contrast, iPSC-derived retinal models provide a high throughput platform which is physiologically relevant for studying human health and disease. They also serve as a platform for drug screening, gene therapy approaches and in vitro toxicology of novel therapeutics in pre-clinical studies. One unique characteristic of stem cell-derived retinal models is the ability to mimic in vivo retinogenesis, providing unparalleled insights into the effects of pathogenic mutations in cells of the developing retina, in a highly accessible way. This review aims to give the reader an overview of iPSC-derived retinal organoids and/or RPE in the context of disease modelling of several inherited retinopathies including Retinitis Pigmentosa, Stargardt disease and Retinoblastoma. We describe the ability of each model to recapitulate in vivo disease phenotypes, validate previous findings from animal models and identify novel pathomechanisms that underpin individual IRDs.
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Affiliation(s)
- Avril Watson
- Biosciences InstituteNewcastle UniversityNewcastle upon TyneUK
| | - Majlinda Lako
- Biosciences InstituteNewcastle UniversityNewcastle upon TyneUK
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9
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Sajovic J, Meglič A, Volk M, Maver A, Jarc-Vidmar M, Hawlina M, Fakin A. Stargardt-like Clinical Characteristics and Disease Course Associated with Variants in the WDR19 Gene. Genes (Basel) 2023; 14:genes14020291. [PMID: 36833218 PMCID: PMC9957452 DOI: 10.3390/genes14020291] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2022] [Revised: 01/11/2023] [Accepted: 01/19/2023] [Indexed: 01/26/2023] Open
Abstract
Variants in WDR19 (IFT144) have been implicated as another possible cause of Stargardt disease. The purpose of this study was to compare longitudinal multimodal imaging of a WDR19-Stargardt patient, harboring p.(Ser485Ile) and a novel c.(3183+1_3184-1)_(3261+1_3262-1)del variant, with 43 ABCA4-Stargardt patients. Age at onset, visual acuity, Ishihara color vision, color fundus, fundus autofluorescence (FAF), spectral-domain optical coherence tomography (OCT) images, microperimetry and electroretinography (ERG) were evaluated. First symptom of WDR19 patient was nyctalopia at the age of 5 years. After the age of 18 years, OCT showed hyper-reflectivity at the level of the external limiting membrane/outer nuclear layer. There was abnormal cone and rod photoreceptor function on ERG. Widespread fundus flecks appeared, followed by perifoveal photoreceptor atrophy. Fovea and peripapillary retina remained preserved until the latest exam at 25 years of age. ABCA4 patients had median age of onset at 16 (range 5-60) years and mostly displayed typical Stargardt triad. A total of 19% had foveal sparing. In comparison to ABCA4 patients, the WDR19 patient had a relatively large foveal preservation and severe rod photoreceptor impairment; however, it was still within the ABCA4 disease spectrum. Addition of WDR19 in the group of genes producing phenocopies of Stargardt disease underlines the importance of genetic testing and may help to understand its pathogenesis.
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Affiliation(s)
- Jana Sajovic
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Andrej Meglič
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Marija Volk
- Clinical Institute of Genomic Medicine, University Medical Centre Ljubljana, Šlajmerjeva 4, 1000 Ljubljana, Slovenia
| | - Aleš Maver
- Clinical Institute of Genomic Medicine, University Medical Centre Ljubljana, Šlajmerjeva 4, 1000 Ljubljana, Slovenia
| | - Martina Jarc-Vidmar
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Vrazov trg 2, 1000 Ljubljana, Slovenia
| | - Marko Hawlina
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Vrazov trg 2, 1000 Ljubljana, Slovenia
| | - Ana Fakin
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
- Faculty of Medicine, University of Ljubljana, Vrazov trg 2, 1000 Ljubljana, Slovenia
- Correspondence:
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10
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Electroretinography as a Biomarker to Monitor the Progression of Stargardt Disease. Int J Mol Sci 2022; 23:ijms232416161. [PMID: 36555803 PMCID: PMC9783580 DOI: 10.3390/ijms232416161] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Revised: 12/12/2022] [Accepted: 12/16/2022] [Indexed: 12/23/2022] Open
Abstract
The aim of the present study is to determine how electroretinographic (ERG) responses reflect age-related disease progression in the Stargardt disease (STGD1). The prospective comparative cohort study included 8 patients harboring two null ABCA4 variants (Group 1) and 34 patients with other ABCA4 genotypes (Group 2). Age at exam, age at onset, visual acuity (VA) and ERG responses were evaluated. The correlation between ERG responses and age in each patient group was determined using linear regression. A Mann-Whitney U Test was used to compare the median values between the groups. Age of onset was significantly earlier in Group 1 than in Group 2 (8 vs. 18), while disease duration was similar (13 vs. 12 years, i.e., advanced stage). Group 1 had significantly worse VA and lower ERG responses. ERG responses that significantly correlated with age in Group 1 were DA 0.01 and 3.0 ERG, which represented a retinal rod system response. The only ERG response that significantly correlated with age in Group 2 was the S-cone ERG. The observed difference was likely due to early cone loss occurring in double-null patients and slower photoreceptor loss in patients with other genotypes. The results suggest that specific ERG responses may be used to detect double-null patients at an early stage and monitor STGD1 disease progression in patients with specific genotypes.
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11
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Hou W, Xu D, Wang L, Chen Y, Chen Z, Zhou C, Chen Y. Plastic structures for diverse substrates: A revisit of human
ABC
transporters. Proteins 2022; 90:1749-1765. [DOI: 10.1002/prot.26406] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 07/31/2022] [Accepted: 08/01/2022] [Indexed: 12/18/2022]
Affiliation(s)
- Wen‐Tao Hou
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Da Xu
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Liang Wang
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Yu Chen
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Zhi‐Peng Chen
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Cong‐Zhao Zhou
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
| | - Yuxing Chen
- School of Life Sciences University of Science and Technology of China Hefei People's Republic of China
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12
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Farnoodian M, Bose D, Khristov V, Susaimanickam PJ, Maddileti S, Mariappan I, Abu-Asab M, Campos M, Villasmil R, Wan Q, Maminishkis A, McGaughey D, Barone F, Gundry RL, Riordon DR, Boheler KR, Sharma R, Bharti K. Cell-autonomous lipid-handling defects in Stargardt iPSC-derived retinal pigment epithelium cells. Stem Cell Reports 2022; 17:2438-2450. [DOI: 10.1016/j.stemcr.2022.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2022] [Revised: 09/30/2022] [Accepted: 10/03/2022] [Indexed: 11/06/2022] Open
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Abstract
In 2001, the first large animal was successfully treated with a gene therapy that restored its vision. Lancelot, the Briard dog that was treated, suffered from a human childhood blindness called Leber's congenital amaurosis type 2. Sixteen years later, the gene therapy was approved by the U.S. Food and Drug Administration. The success of this gene therapy in dogs led to a fast expansion of the ocular gene therapy field. By now every class of inherited retinal dystrophy has been treated in at least one animal model and many clinical trials have been initiated in humans. In this study, we review the status of viral gene therapies for the retina, with a focus on ongoing human clinical trials. It is likely that in the next decade we will see several new viral gene therapies approved.
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Affiliation(s)
- Shun-Yun Cheng
- University of Massachusetts Medical School, Ophthalmology, Worcester, Massachusetts, United States;
| | - Claudio Punzo
- University of Massachusetts Medical School, Ophthalmology, 368 Plantation Street, Albert Sherman Center, AS6-2041, Worcester, Massachusetts, United States, 01605;
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14
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Dean M, Moitra K, Allikmets R. The human ATP-binding cassette (ABC) transporter superfamily. Hum Mutat 2022; 43:1162-1182. [PMID: 35642569 PMCID: PMC9357071 DOI: 10.1002/humu.24418] [Citation(s) in RCA: 39] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Revised: 05/26/2022] [Accepted: 05/27/2022] [Indexed: 11/12/2022]
Abstract
The ATP-binding cassette (ABC) transporter superfamily comprises membrane proteins that efflux various substrates across extra- and intracellular membranes. Mutations in ABC genes cause 21 human disorders or phenotypes with Mendelian inheritance, including cystic fibrosis, adrenoleukodystrophy, retinal degeneration, cholesterol, and bile transport defects. To provide tools to study the function of human ABC transporters we compiled data from multiple genomics databases. We analyzed ABC gene conservation within human populations and across vertebrates and surveyed phenotypes of ABC gene mutations in mice. Most mouse ABC gene disruption mutations have a phenotype that mimics human disease, indicating they are applicable models. Interestingly, several ABCA family genes, whose human function is unknown, have cholesterol level phenotypes in the mouse. Genome-wide association studies confirm and extend ABC traits and suggest several new functions to investigate. Whole-exome sequencing of tumors from diverse cancer types demonstrates that mutations in ABC genes are not common in cancer, but specific genes are overexpressed in select tumor types. Finally, an analysis of the frequency of loss-of-function mutations demonstrates that many human ABC genes are essential with a low level of variants, while others have a higher level of genetic diversity.
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Affiliation(s)
- Michael Dean
- Laboratory of Translational Genomics, National Cancer Institute, Gaithersburg, Maryland 21702
| | | | - Rando Allikmets
- Department of Ophthalmology, Columbia University, New York, New York, 10032
- Department of Pathology & Cell Biology, Columbia University, New York, New York, 10032
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15
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Gullapalli VK, Zarbin MA. New Prospects for Retinal Pigment Epithelium Transplantation. Asia Pac J Ophthalmol (Phila) 2022; 11:302-313. [PMID: 36041145 DOI: 10.1097/apo.0000000000000521] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Accepted: 02/28/2022] [Indexed: 11/26/2022] Open
Abstract
ABSTRACT Retinal pigment epithelium (RPE) transplants rescue photoreceptors in selected animal models of retinal degenerative disease. Early clinical studies of RPE transplants as treatment for age-related macular degeneration (AMD) included autologous and allogeneic transplants of RPE suspensions and RPE sheets for atrophic and neovascular complications of AMD. Subsequent studies explored autologous RPE-Bruch membrane-choroid transplants in patients with neovascular AMD with occasional marked visual benefit, which establishes a rationale for RPE transplants in late-stage AMD. More recent work has involved transplantation of autologous and allogeneic stem cell-derived RPE for patients with AMD and those with Stargardt disease. These early-stage clinical trials have employed RPE suspensions and RPE monolayers on biocompatible scaffolds. Safety has been well documented, but evidence of efficacy is variable. Current research involves development of better scaffolds, improved modulation of immune surveillance, and modification of the extracellular milieu to improve RPE survival and integration with host retina.
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Affiliation(s)
| | - Marco A Zarbin
- Iinstitute of Ophthalmology and visual Science, Rutgers-New Jersey Medical School, Rutgers University, Newark, NJ, US
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16
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Wang Y, Sun W, Zhou J, Li X, Jiang Y, Li S, Jia X, Xiao X, Ouyang J, Wang Y, Zhou L, Long Y, Liu M, Li Y, Yi Z, Wang P, Zhang Q. Different Phenotypes Represent Advancing Stages of ABCA4-Associated Retinopathy: A Longitudinal Study of 212 Chinese Families From a Tertiary Center. Invest Ophthalmol Vis Sci 2022; 63:28. [PMID: 35608843 PMCID: PMC9150840 DOI: 10.1167/iovs.63.5.28] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To evaluate the nature and association of different phenotypes associated with ABCA4 mutations in Chinese. Methods All patients were recruited from our pediatric and genetic eye clinic. Detailed ocular phenotypes were characterized. The disease course was evaluated by long-term follow-up observation, with a focus on fundus changes. Cox regression was used to identify the factors associated with disease progression. Results A systematic review of genetic and clinical data for 228 patients and follow-up data for 42 patients indicated specific features in patients with two ABCA4 variants. Of 185 patients with available fundus images, 107 (57.8%) showed focal lesions restricted to the central macula without flecks. Among these 107 patients, 30 patients (28.0%) initially presented with relatively preserved visual acuity and inconspicuous performance on routine fundus screening. A pigmentary change in the posterior pole was observed in 22 of 185 patients (11.9%), and this change mimicked retinitis pigmentosa in 10 cases (45.5%). Follow-up visits and sibling comparisons demonstrated disease progression from cone-rod dystrophy, Stargardt disease, to retinitis pigmentosa. An earlier age of onset was associated with a more rapid decrease in visual acuity (P = 0.03). Patients with two truncation variants had an earlier age of onset. Conclusion Phenotypic variation in ABCA4-associated retinopathy may represent sequential changes in a single disease: early-stage Stargardt disease may resemble cone-rod dystrophy, whereas the presence of diffuse pigmentation in the late stage may mimic retinitis pigmentosa. Recognizing the natural progression of fundus changes, especially those visualized by wide-field fundus autofluorescence, is valuable for diagnostics and therapeutic decision-making.
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Affiliation(s)
- Yingwei Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Wenmin Sun
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Jing Zhou
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Xueqing Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Yi Jiang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Shiqiang Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Xiaoyun Jia
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Xueshan Xiao
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Jiamin Ouyang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Yueye Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Lin Zhou
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Yuxi Long
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Mengchu Liu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Yongyu Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Zhen Yi
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Panfeng Wang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Qingjiong Zhang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
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Sajovic J, Meglič A, Glavač D, Markelj Š, Hawlina M, Fakin A. The Role of Vitamin A in Retinal Diseases. Int J Mol Sci 2022; 23:1014. [PMID: 35162940 PMCID: PMC8835581 DOI: 10.3390/ijms23031014] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 01/12/2022] [Accepted: 01/13/2022] [Indexed: 12/24/2022] Open
Abstract
Vitamin A is an essential fat-soluble vitamin that occurs in various chemical forms. It is essential for several physiological processes. Either hyper- or hypovitaminosis can be harmful. One of the most important vitamin A functions is its involvement in visual phototransduction, where it serves as the crucial part of photopigment, the first molecule in the process of transforming photons of light into electrical signals. In this process, large quantities of vitamin A in the form of 11-cis-retinal are being isomerized to all-trans-retinal and then quickly recycled back to 11-cis-retinal. Complex machinery of transporters and enzymes is involved in this process (i.e., the visual cycle). Any fault in the machinery may not only reduce the efficiency of visual detection but also cause the accumulation of toxic chemicals in the retina. This review provides a comprehensive overview of diseases that are directly or indirectly connected with vitamin A pathways in the retina. It includes the pathophysiological background and clinical presentation of each disease and summarizes the already existing therapeutic and prospective interventions.
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Affiliation(s)
- Jana Sajovic
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Andrej Meglič
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Damjan Glavač
- Department of Molecular Genetics, Institute of Pathology, Faculty of Medicine, University of Ljubljana, Vrazov trg 2, 1000 Ljubljana, Slovenia
| | - Špela Markelj
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Marko Hawlina
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
| | - Ana Fakin
- Eye Hospital, University Medical Centre Ljubljana, Grablovičeva 46, 1000 Ljubljana, Slovenia
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18
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Golczak M, Moise AR, von Lintig J. Expression and biochemical analyses of proteins involved in the transport of carotenoids and retinoids. Methods Enzymol 2022; 674:447-480. [DOI: 10.1016/bs.mie.2022.05.004] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Association of ABCA4 Gene Polymorphisms with Cleft Lip with or without Cleft Palate in the Polish Population. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2021; 18:ijerph182111483. [PMID: 34769998 PMCID: PMC8583664 DOI: 10.3390/ijerph182111483] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 09/17/2021] [Revised: 10/24/2021] [Accepted: 10/28/2021] [Indexed: 12/01/2022]
Abstract
Background: Non-syndromic cleft lip with/without cleft palate (NSCL/P) is a common congenital condition with a complex aetiology reflecting multiple genetic and environmental factors. Single nucleotide polymorphisms (SNPs) in ABCA4 have been associated with NSCL/P in several studies, although there are some inconsistent results. This study aimed to evaluate whether two SNPs in ABCA4, namely rs4147811 and rs560426, are associated with NSCL/P occurrence in the Polish population. Methods: The study included 627 participants: 209 paediatric patients with NSCL/P and 418 healthy newborn controls. DNA was isolated from the saliva of NSCL/P patients and from umbilical cord blood in the controls. Genotyping of rs4147811 and rs560426 was performed using quantitative PCR. Results: The rs4147811 (AG genotype) SNP in ABCA4 was associated with a decreased risk of NSCL/P (odds ratio (OR) 0.57; 95% confidence interval (CI) 0.39–0.84; p = 0.004), whereas the rs560426 (GG genotype) SNP was associated with an increased risk of NSCL/P (OR 2.13; 95% CI 1.31–3.48; p = 0.002). Limitations: This study—based on the correlation between single genetic variants and the occurrence of different phenotypes—might have limited power in detecting relevant, complex inheritance patterns. ORs are often low to moderate when investigating the association of single genes with the risk of a complex trait. Another limitation was the small number of available NSCL/P samples. Conclusions: The results suggest that genetic variations in ABCA4 are important risk markers of NSCL/P in the Polish population. Further investigation in a larger study group is warranted.
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Al-Khuzaei S, Broadgate S, Foster CR, Shah M, Yu J, Downes SM, Halford S. An Overview of the Genetics of ABCA4 Retinopathies, an Evolving Story. Genes (Basel) 2021; 12:1241. [PMID: 34440414 PMCID: PMC8392661 DOI: 10.3390/genes12081241] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 08/09/2021] [Accepted: 08/10/2021] [Indexed: 11/16/2022] Open
Abstract
Stargardt disease (STGD1) and ABCA4 retinopathies (ABCA4R) are caused by pathogenic variants in the ABCA4 gene inherited in an autosomal recessive manner. The gene encodes an importer flippase protein that prevents the build-up of vitamin A derivatives that are toxic to the RPE. Diagnosing ABCA4R is complex due to its phenotypic variability and the presence of other inherited retinal dystrophy phenocopies. ABCA4 is a large gene, comprising 50 exons; to date > 2000 variants have been described. These include missense, nonsense, splicing, structural, and deep intronic variants. Missense variants account for the majority of variants in ABCA4. However, in a significant proportion of patients with an ABCA4R phenotype, a second variant in ABCA4 is not identified. This could be due to the presence of yet unknown variants, or hypomorphic alleles being incorrectly classified as benign, or the possibility that the disease is caused by a variant in another gene. This underlines the importance of accurate genetic testing. The pathogenicity of novel variants can be predicted using in silico programs, but these rely on databases that are not ethnically diverse, thus highlighting the need for studies in differing populations. Functional studies in vitro are useful towards assessing protein function but do not directly measure the flippase activity. Obtaining an accurate molecular diagnosis is becoming increasingly more important as targeted therapeutic options become available; these include pharmacological, gene-based, and cell replacement-based therapies. The aim of this review is to provide an update on the current status of genotyping in ABCA4 and the status of the therapeutic approaches being investigated.
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Affiliation(s)
- Saoud Al-Khuzaei
- Oxford Eye Hospital, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, UK; (S.A.-K.); (M.S.)
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; (S.B.); (J.Y.)
| | - Suzanne Broadgate
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; (S.B.); (J.Y.)
| | | | - Mital Shah
- Oxford Eye Hospital, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, UK; (S.A.-K.); (M.S.)
| | - Jing Yu
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; (S.B.); (J.Y.)
| | - Susan M. Downes
- Oxford Eye Hospital, John Radcliffe Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford OX3 9DU, UK; (S.A.-K.); (M.S.)
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; (S.B.); (J.Y.)
| | - Stephanie Halford
- Nuffield Laboratory of Ophthalmology, Nuffield Department of Clinical Neuroscience, University of Oxford, Level 6 John Radcliffe Hospital, Headley Way, Oxford OX3 9DU, UK; (S.B.); (J.Y.)
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Structural basis of substrate recognition and translocation by human ABCA4. Nat Commun 2021; 12:3853. [PMID: 34158497 PMCID: PMC8219669 DOI: 10.1038/s41467-021-24194-6] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 06/04/2021] [Indexed: 12/29/2022] Open
Abstract
Human ATP-binding cassette (ABC) subfamily A (ABCA) transporters mediate the transport of various lipid compounds across the membrane. Mutations in human ABCA transporters have been described to cause severe hereditary disorders associated with impaired lipid transport. However, little is known about the mechanistic details of substrate recognition and translocation by ABCA transporters. Here, we present three cryo-EM structures of human ABCA4, a retina-specific ABCA transporter, in distinct functional states at resolutions of 3.3–3.4 Å. In the nucleotide-free state, the two transmembrane domains (TMDs) exhibit a lateral-opening conformation, allowing the lateral entry of substrate from the lipid bilayer. The N-retinylidene-phosphatidylethanolamine (NRPE), the physiological lipid substrate of ABCA4, is sandwiched between the two TMDs in the luminal leaflet and is further stabilized by an extended loop from extracellular domain 1. In the ATP-bound state, the two TMDs display a closed conformation, which precludes the substrate binding. Our study provides a molecular basis to understand the mechanism of ABCA4-mediated NRPE recognition and translocation, and suggests a common ‘lateral access and extrusion’ mechanism for ABCA-mediated lipid transport. Here, cryo-EM structures of human retinal ABCA4 transporter, either in apo state, in complex with ATP or with the physiological lipid substrate N-retinylidene-phosphatidylethanolamine (NRPE), reveal lateral opening, substrate recognition and suggest ‘lateral access and extrusion’ mechanism for ABCA-mediated lipid transport.
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ADIPOR1 deficiency-induced suppression of retinal ELOVL2 and docosahexaenoic acid levels during photoreceptor degeneration and visual loss. Cell Death Dis 2021; 12:458. [PMID: 33963174 PMCID: PMC8105316 DOI: 10.1038/s41419-021-03741-5] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Revised: 03/23/2021] [Accepted: 03/25/2021] [Indexed: 02/03/2023]
Abstract
Lipid metabolism-related gene mutations can cause retinitis pigmentosa, a currently untreatable blinding disease resulting from progressive neurodegeneration of the retina. Here, we demonstrated the influence of adiponectin receptor 1 (ADIPOR1) deficiency in retinal neurodegeneration using Adipor1 knockout (KO) mice. Adipor1 mRNA was observed to be expressed in photoreceptors, predominately within the photoreceptor inner segment (PIS), and increased after birth during the development of the photoreceptor outer segments (POSs) where photons are received by the visual pigment, rhodopsin. At 3 weeks of age, visual function impairment, specifically photoreceptor dysfunction, as recorded by electroretinography (ERG), was evident in homozygous, but not heterozygous, Adipor1 KO mice. However, although photoreceptor loss was evident at 3 weeks of age and progressed until 10 weeks, the level of visual dysfunction was already substantial by 3 weeks, after which it was retained until 10 weeks of age. The rhodopsin mRNA levels had already decreased at 3 weeks, suggesting that reduced rhodopsin may have contributed to early visual loss. Moreover, inflammation and oxidative stress were induced in homozygous KO retinas. Prior to observation of photoreceptor loss via optical microscopy, electron microscopy revealed that POSs were present; however, they were misaligned and their lipid composition, including docosahexaenoic acid (DHA), which is critical in forming POSs, was impaired in the retina. Importantly, the expression of Elovl2, an elongase of very long chain fatty acids expressed in the PIS, was significantly reduced, and lipogenic genes, which are induced under conditions of reduced endogenous DHA synthesis, were increased in homozygous KO mice. The causal relationship between ADIPOR1 deficiency and Elovl2 repression, together with upregulation of lipogenic genes, was confirmed in vitro. Therefore, ADIPOR1 in the retina appears to be indispensable for ELOVL2 induction, which is likely required to supply sufficient DHA for appropriate photoreceptor function and survival.
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Dewell TE, Gjoni K, Liu AZ, Libby ARG, Moore AT, So PL, Conklin BR. Transcription factor overexpression drives reliable differentiation of retinal pigment epithelium from human induced pluripotent stem cells. Stem Cell Res 2021; 53:102368. [PMID: 34087997 DOI: 10.1016/j.scr.2021.102368] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 02/10/2021] [Accepted: 04/21/2021] [Indexed: 12/13/2022] Open
Abstract
Age-related macular degeneration and genetic forms of blindness such as Best Disease and Retinitis Pigmentosa can be caused by degeneration of the Retinal Pigment Epithelium (RPE). RPE generated from patient-derived induced pluripotent stem cells (iPSCs) is valuable for both the study of disease mechanisms and development of therapeutic strategies. However, protocols to produce iPSC-derived RPE in vitro are often inefficient, labor-intensive, low-throughput, and highly variable between cell lines and within batches. Here, we report a robust, scalable method to generate iPSC-RPE using doxycycline-inducible expression of eye field transcription factors OTX2, PAX6 and MITF paired with RPE-permissive culture media. Doxycycline addition induces exogenous expression of these transcription factors in Best Disease patient- and wildtype iPSCs to efficiently produce monolayers of RPE with characteristic morphology and gene expression. Further, these RPE monolayers display functionality features including light absorption via pigmentation, polarity-driven fluid transport, and phagocytosis. With this method, we achieve a highly efficient and easily scalable differentiation without the need for mechanical isolation or enrichment methods, generating RPE cultures applicable for in vitro studies.
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Affiliation(s)
- Tessa E Dewell
- Gladstone Institutes, 1650 Owens Street, San Francisco, CA 94158, USA
| | - Ketrin Gjoni
- Gladstone Institutes, 1650 Owens Street, San Francisco, CA 94158, USA
| | - Angela Z Liu
- Gladstone Institutes, 1650 Owens Street, San Francisco, CA 94158, USA
| | - Ashley R G Libby
- Gladstone Institutes, 1650 Owens Street, San Francisco, CA 94158, USA; Developmental and Stem Cell Biology Program, University of California, 1675 Owens St, San Francisco, CA 94158, USA
| | - Anthony T Moore
- UCSF Department of Ophthalmology, 10 Koret Way, San Francisco, CA 94143-0730, USA
| | - Po-Lin So
- Gladstone Institutes, 1650 Owens Street, San Francisco, CA 94158, USA; Innovative Genomics Institute, 2151 Berkeley Way, Berkeley, CA 94720, USA; Gladstone Institutes Stem Cell Core, 1650 Owens Street, San Francisco, CA 94158, USA
| | - Bruce R Conklin
- Gladstone Institutes, 1650 Owens Street, San Francisco, CA 94158, USA; UCSF Department of Ophthalmology, 10 Koret Way, San Francisco, CA 94143-0730, USA; Innovative Genomics Institute, 2151 Berkeley Way, Berkeley, CA 94720, USA; UCSF Department of Medicine, 535 Mission Bay Blvd South, San Francisco, CA 94158, USA.
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Yeboah GK, Lobanova ES, Brush RS, Agbaga MP. Very long chain fatty acid-containing lipids: a decade of novel insights from the study of ELOVL4. J Lipid Res 2021; 62:100030. [PMID: 33556440 PMCID: PMC8042400 DOI: 10.1016/j.jlr.2021.100030] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 01/12/2021] [Accepted: 01/27/2021] [Indexed: 11/18/2022] Open
Abstract
Lipids play essential roles in maintaining cell structure and function by modulating membrane fluidity and cell signaling. The fatty acid elongase-4 (ELOVL4) protein, expressed in retina, brain, Meibomian glands, skin, testes and sperm, is an essential enzyme that mediates tissue-specific biosynthesis of both VLC-PUFA and VLC-saturated fatty acids (VLC-SFA). These fatty acids play critical roles in maintaining retina and brain function, neuroprotection, skin permeability barrier maintenance, and sperm function, among other important cellular processes. Mutations in ELOVL4 that affect biosynthesis of these fatty acids cause several distinct tissue-specific human disorders that include blindness, age-related cerebellar atrophy and ataxia, skin disorders, early-childhood seizures, mental retardation, and mortality, which underscores the essential roles of ELOVL4 products for life. However, the mechanisms by which one tissue makes VLC-PUFA and another makes VLC-SFA, and how these fatty acids exert their important functional roles in each tissue, remain unknown. This review summarizes research over that last decade that has contributed to our current understanding of the role of ELOVL4 and its products in cellular function. In the retina, VLC-PUFA and their bioactive "Elovanoids" are essential for retinal function. In the brain, VLC-SFA are enriched in synaptic vesicles and mediate neuronal signaling by determining the rate of neurotransmitter release essential for normal neuronal function. These findings point to ELOVL4 and its products as being essential for life. Therefore, mutations and/or age-related epigenetic modifications of fatty acid biosynthetic gene activity that affect VLC-SFA and VLC-PUFA biosynthesis contribute to age-related dysfunction of ELOVL4-expressing tissues.
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Affiliation(s)
- Gyening Kofi Yeboah
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Ekaterina S Lobanova
- Department of Ophthalmology Research, University of Florida, Gainesville, FL, USA
| | - Richard S Brush
- Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Dean A. McGee Eye Institute, Oklahoma City, OK, USA
| | - Martin-Paul Agbaga
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Dean A. McGee Eye Institute, Oklahoma City, OK, USA.
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Stem Cell Ophthalmology Treatment Study (SCOTS): Bone Marrow-Derived Stem Cells in the Treatment of Stargardt Disease. MEDICINES 2021; 8:medicines8020010. [PMID: 33546345 PMCID: PMC7913552 DOI: 10.3390/medicines8020010] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/23/2021] [Accepted: 01/25/2021] [Indexed: 12/15/2022]
Abstract
Background: Stargardt Disease is the most common inherited macular degeneration, typically resulting in progressive central vision loss and legal blindness at an early age. We report regarding 34 eyes with Stargardt Disease treated in the Stem Cell Ophthalmology Treatment Study (SCOTS and SCOTS2). Methods: Autologous bone marrow was processed, separating the stem cell fraction which was provided Arms using retrobulbar, subtenons, intravitreal or subretinal and intravenous. The follow-up period was one year. Results: Of the 34 treated eyes, 21 (61.8%) improved, 8 (23.5%) remained stable, and 5 (14.7%) showed continued progression of their disease. Results were statistically significant with p = 0.0004. The average central vision improvement following treatment was 17.96% (95%CI, 16.39–19.53%) and ranged up to 80.5%. Of 17 patients treated, 13 (76.5%) showed visual acuity improvement in one or both eyes, 3 patients (17.6%) showed no net loss, and 1 worsened as a consequence of disease progression; 94.1% of patients had improved vision or remained stable. There were no adverse events. Conclusions: Patients with Stargardt Disease may potentially benefit from autologous bone marrow-derived stem cells (BMSC) as provided in SCOTS. Improvement or stabilization of vision was found to occur for the vast majority of reported patients and findings were highly statistically significant.
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Hamano F, Kuribayashi H, Iwagawa T, Tsuhako A, Nagata K, Sagara H, Shimizu T, Shindou H, Watanabe S. Mapping membrane lipids in the developing and adult mouse retina under physiological and pathological conditions using mass spectrometry. J Biol Chem 2021; 296:100303. [PMID: 33465374 PMCID: PMC7949107 DOI: 10.1016/j.jbc.2021.100303] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 01/05/2021] [Accepted: 01/14/2021] [Indexed: 12/31/2022] Open
Abstract
Membrane phospholipids play pivotal roles in various cellular processes, and their levels are tightly regulated. In the retina, phospholipids had been scrutinized because of their distinct composition and requirement in visual transduction. However, how lipid composition changes during retinal development remains unclear. Here, we used liquid chromatography–mass spectrometry (LC-MS) to assess the dynamic changes in the levels of two main glycerophospholipids, phosphatidylcholine (PC) and phosphatidylethanolamine (PE), in the developing mouse retina under physiological and pathological conditions. The total levels of PC and PE increased during retinal development, and individual lipid species exhibited distinct level changes. The amount of very-long-chain PC and PE increased dramatically in the late stages of retinal development. The mRNA levels of Elovl2 and Elovl4, genes encoding enzymes essential for the synthesis of very-long-chain polyunsaturated fatty acids, increased in developing photoreceptors. Cell sorting based on CD73 expression followed by LC-MS revealed distinct changes in PC and PE levels in CD73-positive rod photoreceptors and CD73-negative retinal cells. Finally, using the NaIO3-induced photoreceptor degeneration model, we identified photoreceptor-specific changes in PC and PE levels from 1 day after NaIO3 administration, before the outer segment of photoreceptors displayed morphological impairment. In conclusion, our findings provide insight into the dynamic changes in PC and PE levels in the developing and adult mouse retina under physiological and pathological conditions. Furthermore, we provide evidence that cell sorting followed by LC-MS is a promising approach for investigating the relevance of lipid homeostasis in the function of different retinal cell types.
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Affiliation(s)
- Fumie Hamano
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, Japan; Life Sciences Core Facility, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Hiroshi Kuribayashi
- Division of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Toshiro Iwagawa
- Division of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Asano Tsuhako
- Division of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Katsuyuki Nagata
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, Japan
| | - Hiroshi Sagara
- Medical Proteomics Laboratory, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan
| | - Takao Shimizu
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, Japan
| | - Hideo Shindou
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, Japan; Department of Lipid Science, Graduate School of Medicine, University of Tokyo, Bunkyo-ku, Tokyo, Japan
| | - Sumiko Watanabe
- Division of Molecular and Developmental Biology, Institute of Medical Science, University of Tokyo, Minato-ku, Tokyo, Japan.
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Polymorphisms of ATP-Binding Cassette, Sub-Family A, Member 4 (rs560426 and rs481931) and Non-Syndromic Cleft Lip/Palate: A Meta-Analysis. Life (Basel) 2021; 11:life11010058. [PMID: 33467554 PMCID: PMC7830788 DOI: 10.3390/life11010058] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2020] [Revised: 12/19/2020] [Accepted: 01/07/2021] [Indexed: 12/29/2022] Open
Abstract
Background: A number of genes are associated with the incidence of non-syndromic cleft lip/palate (NSCL/P). Studies have shown a significant association between polymorphisms of ATP-binding cassette, sub-family A, member 4 (ABCA4) with the risk of NSCL/P. The present meta-analysis assessed the association between ABCA4 polymorphisms (rs560426 and rs481931) and the NSCL/P risk by reviewing case-control studies. Methods: Four databases (Scopus; Cochrane Library; Web of Science; and PubMed) were searched for articles published up to June 2020. The Review Manager 5.3 software was used to calculate the crude odds ratio (OR) and 95% confidence interval (CI). Both subgroup analyses for ethnicity and source of controls and a meta-regression related to publication year were conducted. Results: Of 94 retrieved studies, 12 were analyzed in this meta-analysis (2859 NSCL/P patients and 3792 controls for ABCA4 rs560426 polymorphism and 1333 NSCL/P patients and 1884 controls for ABCA4 rs481931 polymorphism). Overall, there was no significant association between both polymorphisms and the risk of NSCL/P. However, subgroup analysis demonstrated that there was a higher risk of NSCL/P for specific models: the allelic model (OR = 1.13; p = 0.03), the homozygote model (OR = 1.53; p = 0.04), and the recessive model (OR = 1.30; p = 0.03) in the Asian ethnicity for the rs560426 polymorphism. Conclusion: The findings confirmed that the NSCL/P risk was significantly associated with the G allele and GG genotype of rs560426 polymorphism but not for rs481931 polymorphism. There were no associations between both polymorphisms (rs560426 and rs481931) and the NSCL/P risk in those of European descent and the mixed ethnicities.
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Sung YC, Yang CH, Yang CM, Lin CW, Huang DS, Huang YS, Hu FR, Chen PL, Chen TC. Genotypes Predispose Phenotypes-Clinical Features and Genetic Spectrum of ABCA4-Associated Retinal Dystrophies. Genes (Basel) 2020; 11:genes11121421. [PMID: 33261146 PMCID: PMC7759801 DOI: 10.3390/genes11121421] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2020] [Revised: 11/12/2020] [Accepted: 11/25/2020] [Indexed: 12/31/2022] Open
Abstract
The ABCA4 gene is one of the most common disease-causing genes of inherited retinal degeneration. In this study, we report different phenotypes of ABCA4-associated retinal dystrophies in the Taiwanese population, its clinical progression, and its relationship with genetic characteristics. Thirty-seven subjects were recruited and all patients underwent serial ophthalmic examinations at a single medical center. Fundus autofluorescence (FAF) images were quantified for clinical evaluation, and panel-based next-generation sequencing testing was performed for genetic diagnosis. Visual preservation, disease progression, and genotype–phenotype correlation were analyzed. In this cohort, ABCA4-associated retinal degeneration presented as Stargardt disease 1 (STGD1, 62.16%), retinitis pigmentosa (32.43%), and cone-rod dystrophy (5.41%). STGD1 could be further divided into central and dispersed types. In each phenotype, the lesion areas quantified by FAF increased with age (p < 0.01) and correlated with poorer visual acuity. However, three patients had the foveal sparing phenotype and had relatively preserved visual acuity. Forty-two ABCA4 variants were identified as disease-causing, with c.1804C>T (p.Arg602Trp) the most frequent (37.84%). Patients with a combination of severe/null variants could have more extensive phenotypes, such as arRP and dispersed STGD1. This is the first cohort study of ABCA4-associated retinal degeneration in Taiwan with wide spectrums of both genotypic and phenotypic characteristics. An extremely high prevalence of c.1804C>T, which has not been reported in East Asia before, was noted. The extensiveness of retinal involvement might be regarded as a spectrum of ABCA4-associated retinal dystrophies. Different types of genetic variations could lead to distinctive phenotypes, according to the coding impact of variants.
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Affiliation(s)
- Yu-Chi Sung
- Department of Medical Education, National Taiwan University Hospital, Taipei 100, Taiwan;
| | - Chang-Hao Yang
- Department of Ophthalmology, National Taiwan University Hospital, Taipei 100, Taiwan; (C.-H.Y.); (C.-M.Y.); (C.-W.L.); (D.-S.H.); (Y.-S.H.); (F.-R.H.)
- Department of Ophthalmology, College of Medicine, National Taiwan University, Taipei 100, Taiwan
| | - Chung-May Yang
- Department of Ophthalmology, National Taiwan University Hospital, Taipei 100, Taiwan; (C.-H.Y.); (C.-M.Y.); (C.-W.L.); (D.-S.H.); (Y.-S.H.); (F.-R.H.)
- Department of Ophthalmology, College of Medicine, National Taiwan University, Taipei 100, Taiwan
| | - Chao-Wen Lin
- Department of Ophthalmology, National Taiwan University Hospital, Taipei 100, Taiwan; (C.-H.Y.); (C.-M.Y.); (C.-W.L.); (D.-S.H.); (Y.-S.H.); (F.-R.H.)
| | - Ding-Siang Huang
- Department of Ophthalmology, National Taiwan University Hospital, Taipei 100, Taiwan; (C.-H.Y.); (C.-M.Y.); (C.-W.L.); (D.-S.H.); (Y.-S.H.); (F.-R.H.)
| | - Yu-Shu Huang
- Department of Ophthalmology, National Taiwan University Hospital, Taipei 100, Taiwan; (C.-H.Y.); (C.-M.Y.); (C.-W.L.); (D.-S.H.); (Y.-S.H.); (F.-R.H.)
| | - Fung-Rong Hu
- Department of Ophthalmology, National Taiwan University Hospital, Taipei 100, Taiwan; (C.-H.Y.); (C.-M.Y.); (C.-W.L.); (D.-S.H.); (Y.-S.H.); (F.-R.H.)
- Department of Ophthalmology, College of Medicine, National Taiwan University, Taipei 100, Taiwan
| | - Pei-Lung Chen
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei 100, Taiwan
- Graduate Institute of Medical Genomics and Proteomics, College of Medicine, National Taiwan University, Taipei 100, Taiwan
- Department of Medical Genetics, National Taiwan University Hospital, Taipei 100, Taiwan
- Correspondence: (P.-L.C.); (T.-C.C.); Tel.: +886-2-23123456 (ext. 71942) (P.-L.C.); +886-2-23123456 (ext. 63783) (T.-C.C.); Fax: +886-2-23934420 (T.-C.C.)
| | - Ta-Ching Chen
- Department of Ophthalmology, National Taiwan University Hospital, Taipei 100, Taiwan; (C.-H.Y.); (C.-M.Y.); (C.-W.L.); (D.-S.H.); (Y.-S.H.); (F.-R.H.)
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei 100, Taiwan
- Correspondence: (P.-L.C.); (T.-C.C.); Tel.: +886-2-23123456 (ext. 71942) (P.-L.C.); +886-2-23123456 (ext. 63783) (T.-C.C.); Fax: +886-2-23934420 (T.-C.C.)
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Kubota R, Birch DG, Gregory JK, Koester JM. Randomised study evaluating the pharmacodynamics of emixustat hydrochloride in subjects with macular atrophy secondary to Stargardt disease. Br J Ophthalmol 2020; 106:403-408. [PMID: 33214244 PMCID: PMC8867285 DOI: 10.1136/bjophthalmol-2020-317712] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 09/26/2020] [Accepted: 10/30/2020] [Indexed: 12/12/2022]
Abstract
Background/Aims Stargardt disease is a rare, inherited, degenerative disease of the retina that is the most common type of hereditary macular dystrophy. Currently, no approved treatments for the disease exist. The purpose of this study was to characterise the pharmacodynamics of emixustat, an orally available small molecule that targets the retinal pigment epithelium–specific 65 kDa protein (RPE65), in subjects with macular atrophy secondary to Stargardt disease. Methods In this multicentre study conducted at six study sites in the USA, 23 subjects with macular atrophy secondary to Stargardt disease were randomised to one of three doses of daily emixustat (2.5 mg, 5 mg or 10 mg) and treated for 1 month. The primary outcome was the suppression of the rod b-wave recovery rate on electroretinography after photobleaching, which is an indirect measure of RPE65 inhibition. Results Subjects who received 10 mg emixustat showed near-complete suppression of the rod b-wave amplitude recovery rate postphotobleaching (mean=91.86%, median=96.69%), whereas those who received 5 mg showed moderate suppression (mean=52.2%, median=68.0%). No effect was observed for subjects who received 2.5 mg emixustat (mean=−3.31%, median=−12.23%). The adverse event profile was consistent with prior studies in other patient populations and consisted primarily of ocular adverse events likely related to RPE65 inhibition. Conclusion This study demonstrated dose-dependent suppression of rod b-wave amplitude recovery postphotobleaching, confirming emixustat’s biological activity in patients with Stargardt disease. These findings informed dose selection for a 24-month phase 3 trial (SeaSTAR Study) that is now comparing emixustat to placebo in the treatment of Stargardt disease-associated macular atrophy.
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Affiliation(s)
- Ryo Kubota
- President, Kubota Vision Inc, Seattle, Washington, USA
| | - David G Birch
- Scientific Director, Retina Foundation of the Southwest, Dallas, Texas, USA
| | - Jeff K Gregory
- Clinical Development, Kubota Vision Inc, Seattle, Washington, USA
| | - John M Koester
- Clinical Development, Kubota Vision Inc, Seattle, Washington, USA
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Abstract
Taurine is a sulfur-containing amino acid that is not incorporated into protein but is abundant in retina. Schiff base adducts that form nonenzymatically and reversibly from reactions between taurine and vitamin A aldehyde (A1T) are increased under conditions in which the visual chromophore 11-cis-retinal is more abundant. These settings include black versus albino mice, dark-adapted versus light-adapted mice, and mice expressing the Rpe65-Leu450 versus Rpe65-Met450 variant. Conversely, A1T is less abundant in mouse models deficient in 11-cis-retinal. As an amphiphile, protonated A1T may serve to facilitate retinoid trafficking and could constitute a small-molecule reserve of mobilizable 11-cis-retinal in photoreceptor cells. Visual pigment consists of opsin covalently linked to the vitamin A-derived chromophore, 11-cis-retinaldehyde. Photon absorption causes the chromophore to isomerize from the 11-cis- to all-trans-retinal configuration. Continued light sensitivity necessitates the regeneration of 11-cis-retinal via a series of enzyme-catalyzed steps within the visual cycle. During this process, vitamin A aldehyde is shepherded within photoreceptors and retinal pigment epithelial cells to facilitate retinoid trafficking, to prevent nonspecific reactivity, and to conserve the 11-cis configuration. Here we show that redundancy in this system is provided by a protonated Schiff base adduct of retinaldehyde and taurine (A1-taurine, A1T) that forms reversibly by nonenzymatic reaction. A1T was present as 9-cis, 11-cis, 13-cis, and all-trans isomers, and the total levels were higher in neural retina than in retinal pigment epithelium (RPE). A1T was also more abundant under conditions in which 11-cis-retinaldehyde was higher; this included black versus albino mice, dark-adapted versus light-adapted mice, and mice carrying the Rpe65-Leu450 versus Rpe65-450Met variant. Taurine levels paralleled these differences in A1T. Moreover, A1T was substantially reduced in mice deficient in the Rpe65 isomerase and in mice deficient in cellular retinaldehyde-binding protein; in these models the production of 11-cis-retinal is compromised. A1T is an amphiphilic small molecule that may represent a mechanism for escorting retinaldehyde. The transient Schiff base conjugate that the primary amine of taurine forms with retinaldehyde would readily hydrolyze to release the retinoid and thus may embody a pool of 11-cis-retinal that can be marshalled in photoreceptor cells.
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Liu X, Meng X, Yang L, Long Y, Fujinami-Yokokawa Y, Ren J, Kurihara T, Tsubota K, Tsunoda K, Fujinami K, Li S. Clinical and genetic characteristics of Stargardt disease in a large Western China cohort: Report 1. AMERICAN JOURNAL OF MEDICAL GENETICS PART C-SEMINARS IN MEDICAL GENETICS 2020; 184:694-707. [PMID: 32845068 DOI: 10.1002/ajmg.c.31838] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2020] [Revised: 07/31/2020] [Accepted: 08/05/2020] [Indexed: 01/03/2023]
Abstract
Stargardt disease 1 (STGD1) is the most prevalent retinal dystrophy caused by pathogenic biallelic ABCA4 variants. Forty-two unrelated patients mostly originating from Western China were recruited. Comprehensive ophthalmological examinations, including visual acuity measurements (subjective function), fundus autofluorescence (retinal imaging), and full-field electroretinography (objective function), were performed. Next-generation sequencing (target/whole exome) and direct sequencing were conducted. Genotype grouping was performed based on the presence of deleterious variants. The median age of onset/age was 10.0 (5-52)/29.5 (12-72) years, and the median visual acuity in the right/left eye was 1.30 (0.15-2.28)/1.30 (0.15-2.28) in the logarithm of the minimum angle of resolution unit. Ten patients (10/38, 27.0%) showed confined macular dysfunction, and 27 (27/37, 73.7%) had generalized retinal dysfunction. Fifty-eight pathogenic/likely pathogenic ABCA4 variants, including 14 novel variants, were identified. Eight patients (8/35, 22.8%) harbored multiple deleterious variants, and 17 (17/35, 48.6%) had a single deleterious variant. Significant associations were revealed between subjective functional, retinal imaging, and objective functional groups, identifying a significant genotype-phenotype association. This study illustrates a large phenotypic/genotypic spectrum in a large well-characterized STGD1 cohort. A distinct genetic background of the Chinese population from the Caucasian population was identified; meanwhile, a genotype-phenotype association was similarly represented.
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Affiliation(s)
- Xiao Liu
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China.,Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan.,Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Xiaohong Meng
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Lizhu Yang
- Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan.,Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Yanling Long
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Yu Fujinami-Yokokawa
- Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan.,Department of Health Policy and Management, Keio University School of Medicine, Tokyo, Japan.,Department of Public Health Research, Yokokawa Clinic, Osaka, Japan
| | - Jiayun Ren
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Toshihide Kurihara
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Kazuo Tsubota
- Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan
| | - Kazushige Tsunoda
- Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan
| | - Kaoru Fujinami
- Laboratory of Visual Physiology, Division of Vision Research, National Institute of Sensory Organs, National Hospital Organization Tokyo Medical Center, Tokyo, Japan.,Department of Ophthalmology, Keio University School of Medicine, Tokyo, Japan.,UCL Institute of Ophthalmology, London, UK.,Moorfields Eye Hospital, London, UK
| | - Shiying Li
- Southwest Hospital/Southwest Eye Hospital, Third Military Medical University (Army Medical University), Chongqing, China
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Huang D, Thompson JA, Charng J, Chelva E, McLenachan S, Chen S, Zhang D, McLaren TL, Lamey TM, Constable IJ, De Roach JN, Aung‐Htut MT, Adams A, Fletcher S, Wilton SD, Chen FK. Phenotype-genotype correlations in a pseudodominant Stargardt disease pedigree due to a novel ABCA4 deletion-insertion variant causing a splicing defect. Mol Genet Genomic Med 2020; 8:e1259. [PMID: 32627976 PMCID: PMC7336727 DOI: 10.1002/mgg3.1259] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 03/18/2020] [Accepted: 03/19/2020] [Indexed: 12/27/2022] Open
Abstract
BACKGROUND Deletion-insertion (delins) variants in the retina-specific ATP-binding cassette transporter gene, subfamily A, member 4 (ABCA4) accounts for <1% in Stargardt disease. The consequences of these delins variants on splicing cannot be predicted with certainty without supporting in vitro data. METHODS Candidate ABCA4 variants were revealed by genetic and segregation analysis of a family with pseudodominant Stargardt disease using a commercial panel and Sanger sequencing. RNA extracted from patient-derived fibroblasts was analyzed by RT-PCR to evaluate splicing behavior of the ABCA4 variants. RESULTS Affected members carrying the novel c.6031_6044delinsAGTATTTAACCAATATTT variant in exon 44 presented with contrasting phenotypes; from early-onset cone-rod dystrophy to late-onset macular dystrophy. This variant resulted in a 56-nucleotide deletion in the mutant allele by activation of a cryptic splice acceptor site which disrupts the reading frame and results in a premature termination codon (p.Ile2003LeufsTer41). If translated, the crucial functional domains near the C-terminus would be truncated from the ABCA4 protein. CONCLUSION This work demonstrates the intrafamilial phenotypic variability in a pseudodominant Stargardt disease pedigree and the use of patient-derived fibroblasts to evaluate the effect of a novel ABCA4 delins variant on splicing to complement in silico pathogenicity assessment.
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Affiliation(s)
- Di Huang
- Centre for Molecular Medicine and Innovative TherapeuticsMurdoch UniversityMurdochWestern AustraliaAustralia
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
- Centre for Neuromuscular and Neurological DisordersThe University of Western Australia and Perron Institute for Neurological and Translational ScienceNedlandsWestern AustraliaAustralia
| | - Jennifer A. Thompson
- Australian Inherited Retinal Disease Registry and DNA BankDepartment of Medical Technology and PhysicsSir Charles Gairdner HospitalNedlandsWestern AustraliaAustralia
| | - Jason Charng
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
| | - Enid Chelva
- Australian Inherited Retinal Disease Registry and DNA BankDepartment of Medical Technology and PhysicsSir Charles Gairdner HospitalNedlandsWestern AustraliaAustralia
| | - Samuel McLenachan
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
| | - Shang‐Chih Chen
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
| | - Dan Zhang
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
| | - Terri L. McLaren
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
- Australian Inherited Retinal Disease Registry and DNA BankDepartment of Medical Technology and PhysicsSir Charles Gairdner HospitalNedlandsWestern AustraliaAustralia
| | - Tina M. Lamey
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
- Australian Inherited Retinal Disease Registry and DNA BankDepartment of Medical Technology and PhysicsSir Charles Gairdner HospitalNedlandsWestern AustraliaAustralia
| | - Ian J. Constable
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
- Department of OphthalmologySir Charles Gairdner HospitalNedlandsWestern AustraliaAustralia
| | - John N. De Roach
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
- Australian Inherited Retinal Disease Registry and DNA BankDepartment of Medical Technology and PhysicsSir Charles Gairdner HospitalNedlandsWestern AustraliaAustralia
| | - May Thandar Aung‐Htut
- Centre for Molecular Medicine and Innovative TherapeuticsMurdoch UniversityMurdochWestern AustraliaAustralia
- Centre for Neuromuscular and Neurological DisordersThe University of Western Australia and Perron Institute for Neurological and Translational ScienceNedlandsWestern AustraliaAustralia
| | - Abbie Adams
- Centre for Molecular Medicine and Innovative TherapeuticsMurdoch UniversityMurdochWestern AustraliaAustralia
| | - Sue Fletcher
- Centre for Molecular Medicine and Innovative TherapeuticsMurdoch UniversityMurdochWestern AustraliaAustralia
- Centre for Neuromuscular and Neurological DisordersThe University of Western Australia and Perron Institute for Neurological and Translational ScienceNedlandsWestern AustraliaAustralia
| | - Steve D. Wilton
- Centre for Molecular Medicine and Innovative TherapeuticsMurdoch UniversityMurdochWestern AustraliaAustralia
- Centre for Neuromuscular and Neurological DisordersThe University of Western Australia and Perron Institute for Neurological and Translational ScienceNedlandsWestern AustraliaAustralia
| | - Fred K. Chen
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
- Australian Inherited Retinal Disease Registry and DNA BankDepartment of Medical Technology and PhysicsSir Charles Gairdner HospitalNedlandsWestern AustraliaAustralia
- Department of OphthalmologyRoyal Perth HospitalPerthWestern AustraliaAustralia
- Department of OphthalmologyPerth Children's HospitalNedlandsWestern AustraliaAustralia
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Tao T, Wang L, Chong W, Yang L, Li G. Characteristics of genotype and phenotype in Chinese patients with Bardet-Biedl syndrome. Int Ophthalmol 2020; 40:2325-2343. [PMID: 32448990 DOI: 10.1007/s10792-020-01415-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 05/02/2020] [Indexed: 12/31/2022]
Abstract
PURPOSE To investigate complex and different phenotypes in seven Chinese patients diagnosed with Bardet-Biedl syndrome (BBS) and carrying pathogenic mutations. METHODS Seven unrelated BBS patients were enrolled. Their medical and ophthalmic histories were reviewed, and comprehensive clinical examinations, such as fundus photography, optical coherence tomography, and medical imaging, were performed. A specific hereditary eye disease enrichment panel based on exome-capture technology was used to collect and amplify the protein-coding regions of 441 targeted hereditary eye disease genes, followed by high-throughput sequencing using the Illumina HiSeq platform. RESULTS All patients exhibited the primary clinical phenotype of BBS. Seven BBS mutations were found in five patients (BBS7 in two patients, BBS10 in two patients, BBS12 in one patient), for a detection rate of 71% (5/7). The ratio of novel to known BBS mutations was 5:2. CONCLUSIONS This study showed the phenotypic and genotypic spectrum of BBS patients from China, and the findings underscore the importance of obtaining comprehensive clinical observations and molecular analyses for ciliopathies.
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Affiliation(s)
- Tianchang Tao
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Lab, Beijing, People's Republic of China
| | - Lei Wang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Lab, Beijing, People's Republic of China
| | - Weihua Chong
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Lab, Beijing, People's Republic of China
| | - Liping Yang
- Department of Ophthalmology, Peking University Third Hospital, Key Laboratory of Restoration of Damaged Ocular Nerve Beijing, Beijing, People's Republic of China
| | - Genlin Li
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University; Beijing Ophthalmology & Visual Sciences Key Lab, Beijing, People's Republic of China.
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von Lintig J, Moon J, Babino D. Molecular components affecting ocular carotenoid and retinoid homeostasis. Prog Retin Eye Res 2020; 80:100864. [PMID: 32339666 DOI: 10.1016/j.preteyeres.2020.100864] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 04/13/2020] [Accepted: 04/17/2020] [Indexed: 12/15/2022]
Abstract
The photochemistry of vision employs opsins and geometric isomerization of their covalently bound retinylidine chromophores. In different animal classes, these light receptors associate with distinct G proteins that either hyperpolarize or depolarize photoreceptor membranes. Vertebrates also use the acidic form of chromophore, retinoic acid, as the ligand of nuclear hormone receptors that orchestrate eye development. To establish and sustain these processes, animals must acquire carotenoids from the diet, transport them, and metabolize them to chromophore and retinoic acid. The understanding of carotenoid metabolism, however, lagged behind our knowledge about the biology of their receptor molecules. In the past decades, much progress has been made in identifying the genes encoding proteins that mediate the transport and enzymatic transformations of carotenoids and their retinoid metabolites. Comparative analysis in different animal classes revealed how evolutionary tinkering with a limited number of genes evolved different biochemical strategies to supply photoreceptors with chromophore. Mutations in these genes impair carotenoid metabolism and induce various ocular pathologies. This review summarizes this advancement and introduces the involved proteins, including the homeostatic regulation of their activities.
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Affiliation(s)
- Johannes von Lintig
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA.
| | - Jean Moon
- Department of Pharmacology, School of Medicine, Case Western Reserve University, Cleveland, OH, USA
| | - Darwin Babino
- Department of Ophthalmology, School of Medicine, University of Washington, Seattle, WA, USA
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Abu-Ameerh M, Mohammad H, Dardas Z, Barham R, Ali D, Bijawi M, Tawalbeh M, Amr S, Hatmal MM, Al-Bdour M, Awidi A, Azab B. Extending the spectrum of CLRN1- and ABCA4-associated inherited retinal dystrophies caused by novel and recurrent variants using exome sequencing. Mol Genet Genomic Med 2020; 8:e1123. [PMID: 31968401 PMCID: PMC7057102 DOI: 10.1002/mgg3.1123] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2019] [Revised: 12/14/2019] [Accepted: 12/27/2019] [Indexed: 01/13/2023] Open
Abstract
Background Inherited retinal dystrophies (IRDs) are characterized by extreme genetic and clinical heterogeneity. There are many genes that are known to cause IRD which makes the identification of the underlying genetic causes quite challenging. And in view of the emergence of therapeutic options, it is essential to combine molecular and clinical data to correctly diagnose IRD patients. In this study, we aimed to identify the disease‐causing variants (DCVs) in four consanguineous Jordanian families with IRDs and describe genotype–phenotype correlations. Methods Exome sequencing (ES) was employed on the proband patients of each family, followed by segregation analysis of candidate variants in affected and unaffected family members by Sanger sequencing. Simulation analysis was done on one novel CLRN1 variant to characterize its effect on mRNA processing. Clinical evaluation included history, slit‐lamp biomicroscopy, and indirect ophthalmoscopy. Results We identified two novel variants in CLRN1 [(c.433+1G>A) and (c.323T>C, p.Leu108Pro)], and two recurrent variants in ABCA4 [(c.1648G>A, p.Gly550Arg) and (c.5460+1G>A)]. Two families with the same DCV were found to have different phenotypes and another family was shown to have sector RP. Moreover, simulation analysis for the CLRN1 splice donor variant (c.433+1G>A) showed that the variant might affect mRNA processing resulting in the formation of an abnormal receptor. Also, a family that was previously diagnosed with nonsyndromic RP was found to have Usher syndrome based on their genetic assessment and audiometry. Conclusion Our findings extend the spectrum of CLRN1‐ and ABCA4‐associated IRDs and describe new phenotypes for these genes. We also highlighted the importance of combining molecular and clinical data to correctly diagnose IRDs and the utility of simulation analysis to predict the effect of splice donor variants on protein formation and function.
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Affiliation(s)
- Mohammed Abu-Ameerh
- Department of Ophthalmology, Jordan University Hospital, The University of Jordan, Amman, Jordan
| | | | - Zain Dardas
- Department of Pathology, Microbiology and Forensic Medicine, School of Medicine, The University of Jordan, Amman, Jordan
| | - Raghda Barham
- Cell Therapy Center, The University of Jordan, Amman, Jordan
| | - Dema Ali
- Cell Therapy Center, The University of Jordan, Amman, Jordan
| | - Maysa Bijawi
- Cell Therapy Center, The University of Jordan, Amman, Jordan
| | - Mohamed Tawalbeh
- Department of Otolaryngology, Jordan University Hospital, The University of Jordan, Amman, Jordan
| | - Sami Amr
- Department of Pathology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Ma'mon M Hatmal
- Department of Medical Laboratory Sciences, Faculty of Allied Health Sciences, The Hashemite University, Zarqa, Jordan
| | - Muawyah Al-Bdour
- Department of Ophthalmology, Jordan University Hospital, The University of Jordan, Amman, Jordan
| | - Abdalla Awidi
- Cell Therapy Center, The University of Jordan, Amman, Jordan.,Department of Medicine and Hematology, Jordan University Hospital, The University of Jordan, Amman, Jordan
| | - Belal Azab
- Department of Pathology, Microbiology and Forensic Medicine, School of Medicine, The University of Jordan, Amman, Jordan.,Human and Molecular Genetics, Medical College of Virginia, Virginia Commonwealth University, Richmond, VA, USA
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All-trans-retinal induces autophagic cell death via oxidative stress and the endoplasmic reticulum stress pathway in human retinal pigment epithelial cells. Toxicol Lett 2020; 322:77-86. [PMID: 31931077 DOI: 10.1016/j.toxlet.2020.01.005] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Revised: 01/03/2020] [Accepted: 01/06/2020] [Indexed: 11/20/2022]
Abstract
Failure of all-trans-retinal (atRAL) clearance contributes to retina degeneration. However, whether autophagy can be activated by excess atRAL accumulation in retinal pigment epithelial (RPE) cells is not known. This study showed that atRAL provoked mitochondria-associated reactive oxygen species (ROS) production, activated the nuclear factor (erythroid-derived 2)-like 2 and apoptosis in a human RPE cell line, ARPE-19 cells. Moreover, we found that autophagic flux was functionally activated after atRAL treatment. The antioxidant N-acetylcysteine attenuated the expression of autophagy markers, suggesting that ROS triggered atRAL-activated autophagy. In addition, autophagic cell death was observed in atRAL-treated RPE cells, while inhibition of autophagy with 3-methyladenine or LC3, Beclin1, p62 silencing ameliorated atRAL-induced cytotoxicity. Suppression of autophagy quenched mitochondrial ROS and inhibited HO-1 and γ-GCSh expression, indicating that atRAL-activated autophagy enhances intracellular oxidative stress, thereby promoting RPE cell apoptosis. Furthermore, we found that inhibiting endoplasmic reticulum (ER) stress suppressed atRAL-induced mitochondrial ROS generation, subsequently attenuated autophagy and apoptosis in RPE cells. Taken together, these results suggest that atRAL-induced oxidative stress and ER stress modulate autophagy, which may contribute to RPE degeneration. There may be positive feedback regulatory mechanisms between atRAL-induced oxidative stress and autophagy or ER stress.
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Arrigo A, Romano F, Aragona E, di Nunzio C, Sperti A, Bandello F, Battaglia Parodi M. OCTA-Based Identification of Different Vascular Patterns in Stargardt Disease. Transl Vis Sci Technol 2019; 8:26. [PMID: 31832280 PMCID: PMC6900965 DOI: 10.1167/tvst.8.6.26] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Accepted: 10/02/2019] [Indexed: 12/16/2022] Open
Abstract
Purpose The aim of the present study was to analyze quantitative optical coherence tomography (OCT) and OCT angiography (OCTA) parameters to identify clinically relevant cutoff values able to detect clinically different Stargardt's disease (STGD) subgroups. Methods Consecutive STGD patients were recruited and underwent complete ophthalmologic examination, including multimodal imaging. Several quantitative parameters were extracted both from structural OCT and OCTA images and were statistically analyzed. A post hoc analysis was performed to identify a quantitative cutoff able to distinguish two clinically different STGD subgroups. Main outcome measures were total retinal thickness, central macular thickness (CMT), retinal layers thickness, retinal and choroidal hyperreflective foci (HF) number, vessel density (VD), vessel tortuosity (VT), vessel dispersion (Vdisp), and vessel rarefaction (VR) of macular and optic nerve head plexa. Results Overall, 54 eyes of 54 STGD patients (18 males) and 54 eyes of 54 healthy age- and sex-matched controls were included in the analysis. All quantitative parameters resulted significantly worse in STGD than controls (P < 0.01). Moreover, a VT cutoff of 5 allowed to distinguish the following two categories: a functionally and anatomically better STGD group and a worse group. BCVA resulted 0.42 ± 0.28 logMAR in the best group versus 1.09 ± 0.36 logMAR in the worst (P < 0.01). Structural OCT and OCTA parameters significantly differed between the two STGD groups. Conclusions Quantitative OCTA was able to detect different morphofunctional STGD phenotypes. Translational Relevance OCTA-based classification of STGD patients detected different patients' subgroups, differing in terms of morphologic and functional features, with a potential impact on clinical and research settings.
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Affiliation(s)
- Alessandro Arrigo
- Department of Ophthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, Milan, Italy
| | - Francesco Romano
- Department of Ophthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, Milan, Italy.,Eye Clinic, Department of Biomedical and Clinical Science, Luigi Sacco University Hospital, Milan, Italy
| | - Emanuela Aragona
- Department of Ophthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, Milan, Italy
| | - Carlo di Nunzio
- Department of Ophthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, Milan, Italy
| | - Andrea Sperti
- Department of Ophthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, Milan, Italy
| | - Francesco Bandello
- Department of Ophthalmology, IRCCS Ospedale San Raffaele, University Vita-Salute, Milan, Italy
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Xia QQ, Zhang LM, Zhou YY, Wu YL, Li J. All-trans-retinoic acid generation is an antidotal clearance pathway for all-trans-retinal in the retina. J Zhejiang Univ Sci B 2019; 20:960-971. [PMID: 31749343 DOI: 10.1631/jzus.b1900271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The present study was designed to analyze the metabolites of all-trans-retinal (atRal) and compare the cytotoxicity of atRal versus its derivative all-trans-retinoic acid (atRA) in human retinal pigment epithelial (RPE) cells. We confirmed that atRA was produced in normal pig neural retina and RPE. The amount of all-trans-retinol (atROL) converted from atRal was about 2.7 times that of atRal-derived atRA after incubating RPE cells with 10 μmol/L atRal for 24 h, whereas atRA in medium supernatant is more plentiful (91 vs. 29 pmol/mL), suggesting that atRA conversion facilitates elimination of excess atRal in the retina. Moreover, we found that mRNA expression of retinoic acid-specific hydroxylase CYP26b1 was dose-dependently up-regulated by atRal exposure in RPE cells, indicating that atRA inactivation may be also initiated in atRal-accumulated RPE cells. Our data show that atRA-caused viability inhibition was evidently reduced compared with the equal concentration of its precursor atRal. Excess accumulation of atRal provoked intracellular reactive oxygen species (ROS) overproduction, heme oxygenase-1 (HO-1) expression, and increased cleaved poly(ADP-ribose) polymerase 1 (PARP1) expression in RPE cells. In contrast, comparable dosage of atRA-induced oxidative stress was much weaker, and it could not activate apoptosis in RPE cells. These results suggest that atRA generation is an antidotal metabolism pathway for atRal in the retina. Moreover, we found that in the eyes of ABCA4-/-RDH8-/- mice, a mouse model with atRal accumulation in the retina, the atRA content was almost the same as that in the wild type. It is possible that atRal accumulation simultaneously and equally promotes atRA synthesis and clearance in eyes of ABCA4-/-RDH8-/- mice, thus inhibiting the further increase of atRA in the retina. Our present study provides further insights into atRal clearance in the retina.
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Affiliation(s)
- Qing-Qing Xia
- Central Laboratory, Department of Laboratory Medicine, Huangyan Hospital of Wenzhou Medical University, Taizhou First People's Hospital, Taizhou 318020, China
| | - Ling-Min Zhang
- Central Laboratory, Department of Laboratory Medicine, Huangyan Hospital of Wenzhou Medical University, Taizhou First People's Hospital, Taizhou 318020, China
| | - Ying-Ying Zhou
- Central Laboratory, Department of Laboratory Medicine, Huangyan Hospital of Wenzhou Medical University, Taizhou First People's Hospital, Taizhou 318020, China
| | - Ya-Lin Wu
- Eye Institute of Xiamen University, Fujian Provincial Key Laboratory of Ophthalmology and Visual Science, School of Medicine, Xiamen University, Xiamen 361102, China
| | - Jie Li
- Central Laboratory, Department of Laboratory Medicine, Huangyan Hospital of Wenzhou Medical University, Taizhou First People's Hospital, Taizhou 318020, China
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Amawi H, Sim HM, Tiwari AK, Ambudkar SV, Shukla S. ABC Transporter-Mediated Multidrug-Resistant Cancer. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1141:549-580. [PMID: 31571174 DOI: 10.1007/978-981-13-7647-4_12] [Citation(s) in RCA: 144] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
ATP-binding cassette (ABC) transporters are involved in active pumping of many diverse substrates through the cellular membrane. The transport mediated by these proteins modulates the pharmacokinetics of many drugs and xenobiotics. These transporters are involved in the pathogenesis of several human diseases. The overexpression of certain transporters by cancer cells has been identified as a key factor in the development of resistance to chemotherapeutic agents. In this chapter, the localization of ABC transporters in the human body, their physiological roles, and their roles in the development of multidrug resistance (MDR) are reviewed. Specifically, P-glycoprotein (P-GP), multidrug resistance-associated proteins (MRPs), and breast cancer resistance protein (BCRP/ABCG2) are described in more detail. The potential of ABC transporters as therapeutic targets to overcome MDR and strategies for this purpose are discussed as well as various explanations for the lack of efficacy of ABC drug transporter inhibitors to increase the efficiency of chemotherapy.
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Affiliation(s)
- Haneen Amawi
- Department of Pharmacy Practice, Faculty of Pharmacy, Yarmouk University, Irbid, Jordan
| | - Hong-May Sim
- Department of Pharmacy, Faculty of Science, National University of Singapore, Singapore, Singapore
| | - Amit K Tiwari
- Department of Pharmacology and Experimental Therapeutics, College of Pharmacy & Pharmaceutical Sciences, University of Toledo, Toledo, OH, USA
| | - Suresh V Ambudkar
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA
| | - Suneet Shukla
- Laboratory of Cell Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA.
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40
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Hu FY, Li JK, Gao FJ, Qi YH, Xu P, Zhang YJ, Wang DD, Wang LS, Li W, Wang M, Chen F, Shen SM, Xu GZ, Zhang SH, Chang Q, Wu JH. ABCA4 Gene Screening in a Chinese Cohort With Stargardt Disease: Identification of 37 Novel Variants. Front Genet 2019; 10:773. [PMID: 31543898 PMCID: PMC6739639 DOI: 10.3389/fgene.2019.00773] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2019] [Accepted: 07/22/2019] [Indexed: 11/13/2022] Open
Abstract
Purpose: To clarify the mutation spectrum and frequency of ABCA4 in a Chinese cohort with Stargardt disease (STGD1). Methods: A total of 153 subjects, comprising 25 families (25 probands and their family members) and 71 sporadic cases, were recruited for the analysis of ABCA4 variants. All probands with STGD1 underwent a comprehensive ophthalmologic examination. Overall, 792 genes involved in common inherited eye diseases were screened for variants by panel-based next-generation sequencing (NGS). Variants were filtered and analyzed to evaluate possible pathogenicity. Results: The total variant detection rate of at least one ABCA4 mutant allele was 84.3% (129/153): two or three disease-associated variants in 86 subjects (56.2%), one mutant allele in 43 subjects (28.1%), and no variants in 24 subjects (15.7%). Ninety-six variants were identified in the total cohort, which included 62 missense (64%), 15 splicing (16%), 11 frameshift (12%), 6 nonsense (6%), and 2 small insertion or deletion (2%) variants. Thirty-seven novel variants were found, including a de novo variant, c.4561delA. The most prevalent variant was c.101_106delCTTTAT (10.5%), followed by c.2894A > G (6.5%) and c.6563T > C (4.6%), in STGD1 patients from eastern China. Conclusion: Thirty-seven novel variants were detected using panel-based NGS, including one de novo variant, further extending the mutation spectrum of ABCA4. The common variants in a population from eastern China with STGD1 were also identified.
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Affiliation(s)
- Fang-Yuan Hu
- Eye Institute, Eye and ENT Hospital, College of Medicine, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Science and Technology Commission of Shanghai Municipality, Shanghai, China.,Key Laboratory of Myopia (Fudan University), Chinese Academy of Medical Sciences, National Health Commission, Shanghai, China
| | - Jian-Kang Li
- BGI-Shenzhen, Shenzhen, China.,Department of Computer Science, City University of Hong Kong, Kowloon, Hong Kong
| | - Feng-Juan Gao
- Eye Institute, Eye and ENT Hospital, College of Medicine, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Science and Technology Commission of Shanghai Municipality, Shanghai, China.,Key Laboratory of Myopia (Fudan University), Chinese Academy of Medical Sciences, National Health Commission, Shanghai, China
| | - Yu-He Qi
- Eye Institute, Eye and ENT Hospital, College of Medicine, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Science and Technology Commission of Shanghai Municipality, Shanghai, China.,Key Laboratory of Myopia (Fudan University), Chinese Academy of Medical Sciences, National Health Commission, Shanghai, China
| | - Ping Xu
- Eye Institute, Eye and ENT Hospital, College of Medicine, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Science and Technology Commission of Shanghai Municipality, Shanghai, China.,Key Laboratory of Myopia (Fudan University), Chinese Academy of Medical Sciences, National Health Commission, Shanghai, China
| | - Yong-Jin Zhang
- Eye Institute, Eye and ENT Hospital, College of Medicine, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Science and Technology Commission of Shanghai Municipality, Shanghai, China.,Key Laboratory of Myopia (Fudan University), Chinese Academy of Medical Sciences, National Health Commission, Shanghai, China
| | - Dan-Dan Wang
- Eye Institute, Eye and ENT Hospital, College of Medicine, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Science and Technology Commission of Shanghai Municipality, Shanghai, China.,Key Laboratory of Myopia (Fudan University), Chinese Academy of Medical Sciences, National Health Commission, Shanghai, China
| | - Lu-Sheng Wang
- Department of Computer Science, City University of Hong Kong, Kowloon, Hong Kong
| | - Wei Li
- BGI-Shenzhen, Shenzhen, China.,BGI Education Center, University of Chinese Academy of Sciences, Shenzhen, China
| | - Min Wang
- Eye Institute, Eye and ENT Hospital, College of Medicine, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Science and Technology Commission of Shanghai Municipality, Shanghai, China.,Key Laboratory of Myopia (Fudan University), Chinese Academy of Medical Sciences, National Health Commission, Shanghai, China
| | - Fang Chen
- BGI-Shenzhen, Shenzhen, China.,Laboratory of Genomics and Molecular Biomedicine, Department of Biology, University of Copenhagen, Copenhagen, Denmark.,Shenzhen Engineering Laboratory for Birth Defects Screening, BGI-Shenzhen, Shenzhen, China
| | | | - Ge-Zhi Xu
- Eye Institute, Eye and ENT Hospital, College of Medicine, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Science and Technology Commission of Shanghai Municipality, Shanghai, China.,Key Laboratory of Myopia (Fudan University), Chinese Academy of Medical Sciences, National Health Commission, Shanghai, China
| | - Sheng-Hai Zhang
- Eye Institute, Eye and ENT Hospital, College of Medicine, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Science and Technology Commission of Shanghai Municipality, Shanghai, China.,Key Laboratory of Myopia (Fudan University), Chinese Academy of Medical Sciences, National Health Commission, Shanghai, China
| | - Qing Chang
- Eye Institute, Eye and ENT Hospital, College of Medicine, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Science and Technology Commission of Shanghai Municipality, Shanghai, China.,Key Laboratory of Myopia (Fudan University), Chinese Academy of Medical Sciences, National Health Commission, Shanghai, China
| | - Ji-Hong Wu
- Eye Institute, Eye and ENT Hospital, College of Medicine, Fudan University, Shanghai, China.,State Key Laboratory of Medical Neurobiology, Institutes of Brain Science and Collaborative Innovation Center for Brain Science, Shanghai Medical College, Fudan University, Shanghai, China.,Shanghai Key Laboratory of Visual Impairment and Restoration, Science and Technology Commission of Shanghai Municipality, Shanghai, China.,Key Laboratory of Myopia (Fudan University), Chinese Academy of Medical Sciences, National Health Commission, Shanghai, China
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41
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Liu Q, Sabirzhanova I, Bergbower EAS, Yanda M, Guggino WG, Cebotaru L. The CFTR Corrector, VX-809 (Lumacaftor), Rescues ABCA4 Trafficking Mutants: a Potential Treatment for Stargardt Disease. Cell Physiol Biochem 2019; 53:400-412. [PMID: 31403270 DOI: 10.33594/000000146] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Accepted: 08/08/2019] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND/AIMS Mutations in ABCA4 cause Stargardt macular degeneration, which invariably ends in legal blindness. We studied two common mutants, A1038V (in NBD1) and G1961E (in NBD2), with the purpose of exploring how they interact with the cell's quality control mechanism. The study was designed to determine how these mutants can be rescued. METHODS We expressed wt and mutant ABCA4 in HEK293 cells and studied the effect of the mutations on trafficking and processing and the ability of correctors to rescue them. We used a combination of western blotting, confocal microscopy and surface biotinylation coupled with pulldown of plasma membrane proteins. RESULTS G1961E is sensitive to inhibitors of the aggresome, tubacin and the lysosome, bafilomycin A. Both mutants cause a reduction in heat shock protein, Hsp27. Incubation of HEK293 cells expressing the mutants with VX-809, an FDA approved drug for the treatment of cystic fibrosis, increased the levels of A1038V and G1961E by 2- to 3-fold. Importantly, VX-809 increased the levels of both mutants at the plasma membrane suggesting that trafficking had been restored. Transfecting additional Hsp27 to the cells also increased the steady state levels of both mutants. However, in combination with VX-809 the addition of Hsp27 caused a dramatic increase in the protein expression particularly in the G1961 mutant which increased approximately 5-fold. CONCLUSION Our results provide a new mechanism for the rescue of ABCA4 trafficking mutants based on the restoration of Hsp27. Our results provide a pathway for the treatment of Stargardt disease.
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Affiliation(s)
- Qiangni Liu
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Inna Sabirzhanova
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Emily Anne Smith Bergbower
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Murali Yanda
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - William G Guggino
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA
| | - Liudmila Cebotaru
- Division of Gastroenterology and Hepatology, Departments of Medicine, Johns Hopkins University, Baltimore, MD, USA,
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42
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Garanto A, Duijkers L, Tomkiewicz TZ, Collin RWJ. Antisense Oligonucleotide Screening to Optimize the Rescue of the Splicing Defect Caused by the Recurrent Deep-Intronic ABCA4 Variant c.4539+2001G>A in Stargardt Disease. Genes (Basel) 2019; 10:genes10060452. [PMID: 31197102 PMCID: PMC6628380 DOI: 10.3390/genes10060452] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2019] [Revised: 06/04/2019] [Accepted: 06/11/2019] [Indexed: 12/17/2022] Open
Abstract
Deep-sequencing of the ABCA4 locus has revealed that ~10% of autosomal recessive Stargardt disease (STGD1) cases are caused by deep-intronic mutations. One of the most recurrent deep-intronic variants in the Belgian and Dutch STGD1 population is the c.4539+2001G>A mutation. This variant introduces a 345-nt pseudoexon to the ABCA4 mRNA transcript in a retina-specific manner. Antisense oligonucleotides (AONs) are short sequences of RNA that can modulate splicing. In this work, we designed 26 different AONs to perform a thorough screening to identify the most effective AONs to correct splicing defects associated with c.4539+2001G>A. All AONs were tested in patient-derived induced pluripotent stem cells (iPSCs) that were differentiated to photoreceptor precursor cells (PPCs). AON efficacy was assessed through RNA analysis and was based on correction efficacy, and AONs were grouped and their properties assessed. We (a) identified nine AONs with significant correction efficacies (>50%), (b) confirmed that a single nucleotide mismatch was sufficient to significantly decrease AON efficacy, and (c) found potential correlations between efficacy and some of the parameters analyzed. Overall, our results show that AON-based splicing modulation holds great potential for treating Stargardt disease caused by splicing defects in ABCA4.
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Affiliation(s)
- Alejandro Garanto
- Department of Human Genetics and Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525GA Nijmegen, The Netherlands.
| | - Lonneke Duijkers
- Department of Human Genetics, Radboud University Medical Center, 6525GA Nijmegen, The Netherlands.
| | - Tomasz Z Tomkiewicz
- Department of Human Genetics and Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525GA Nijmegen, The Netherlands.
| | - Rob W J Collin
- Department of Human Genetics and Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, 6525GA Nijmegen, The Netherlands.
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43
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Garces F, Jiang K, Molday LL, Stöhr H, Weber BH, Lyons CJ, Maberley D, Molday RS. Correlating the Expression and Functional Activity of ABCA4 Disease Variants With the Phenotype of Patients With Stargardt Disease. Invest Ophthalmol Vis Sci 2019; 59:2305-2315. [PMID: 29847635 PMCID: PMC5937799 DOI: 10.1167/iovs.17-23364] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Purpose Stargardt disease (STGD1), the most common early-onset recessive macular degeneration, is caused by mutations in the gene encoding the ATP-binding cassette transporter ABCA4. Although extensive genetic studies have identified more than 1000 mutations that cause STGD1 and related ABCA4-associated diseases, few studies have investigated the extent to which mutations affect the biochemical properties of ABCA4. The purpose of this study was to correlate the expression and functional activities of missense mutations in ABCA4 identified in a cohort of Canadian patients with their clinical phenotype. Methods Eleven patients from British Columbia were diagnosed with STGD1. The exons and exon-intron boundaries were sequenced to identify potential pathologic mutations in ABCA4. Missense mutations were expressed in HEK293T cells and their level of expression, retinoid substrate binding properties, and ATPase activities were measured and correlated with the phenotype of the STGD1 patients. Results Of the 11 STGD1 patients analyzed, 7 patients had two mutations in ABCA4, 3 patients had one detected mutation, and 1 patient had no mutations in the exons and flanking regions. Included in this cohort of patients was a severely affected 11-year-old child who was homozygous for the novel p.Ala1794Pro mutation. Expression and functional analysis of this variant and other disease-associated variants compared favorably with the phenotypes of this cohort of STGD1 patients. Conclusions Although many factors contribute to the phenotype of STGD1 patients, the expression and residual activity of ABCA4 mutants play a major role in determining the disease severity of STGD1 patients.
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Affiliation(s)
- Fabian Garces
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Kailun Jiang
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Laurie L Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada
| | - Heidi Stöhr
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Bernhard H Weber
- Institute of Human Genetics, University of Regensburg, Regensburg, Germany
| | - Christopher J Lyons
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - David Maberley
- Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
| | - Robert S Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, British Columbia, Canada.,Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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44
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Identification of novel pathogenic ABCA4 variants in a Han Chinese family with Stargardt disease. Biosci Rep 2019; 39:BSR20180872. [PMID: 30563929 PMCID: PMC6331664 DOI: 10.1042/bsr20180872] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 12/05/2018] [Accepted: 12/11/2018] [Indexed: 12/16/2022] Open
Abstract
Stargardt disease (STGD1, OMIM 248200) is a common hereditary juvenile or early adult onset macular degeneration. It ultimately leads to progressive central vision loss. Here, we sought to identify gene mutations associated with STGD1 in a three-generation Han Chinese pedigree by whole exome sequencing and Sanger sequencing. Two novel potentially pathogenic variants in a compound heterozygous state, c.3607G>T (p.(Gly1203Trp)) and c.6722T>C (p.(Leu2241Pro)), in the ATP binding cassette subfamily A member 4 gene (ABCA4) were identified as contributing to the family’s STGD1 phenotype. These variants may impact the ABCA4 protein structure and reduce the retinal-activated ATPase activity, leading to abnormal all-trans retinal accumulation in photoreceptor outer segments and in retinal pigment epithelium cells. The present study broadens the mutational spectrum of the ABCA4 responsible for STGD1. A combination of whole exome sequencing and Sanger sequencing is likely to be a time-saving and cost-efficient approach to screen pathogenic variants in genetic disorders caused by sizable genes, as well as avoiding misdiagnosis. These results perhaps refine genetic counseling and ABCA4-targetted treatments for families affected by STGD1.
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45
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Molday LL, Wahl D, Sarunic MV, Molday RS. Localization and functional characterization of the p.Asn965Ser (N965S) ABCA4 variant in mice reveal pathogenic mechanisms underlying Stargardt macular degeneration. Hum Mol Genet 2019; 27:295-306. [PMID: 29145636 DOI: 10.1093/hmg/ddx400] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Accepted: 11/08/2017] [Indexed: 11/12/2022] Open
Abstract
ABCA4 is a member of the superfamily of ATP-binding cassette (ABC) proteins that transports N-retinylidene-phosphatidylethanolamine (N-Ret-PE) across outer segment disc membranes thereby facilitating the removal of potentially toxic retinoid compounds from photoreceptor cells. Mutations in the gene encoding ABCA4 are responsible for Stargardt disease (STGD1), an autosomal recessive retinal degenerative disease that causes severe vision loss. To define the molecular basis for STGD1 associated with the p.Asn965Ser (N965S) mutation in the Walker A motif of nucleotide binding domain 1 (NBD1), we generated a p.Asn965Ser knockin mouse and compared the subcellular localization and molecular properties of the disease variant with wild-type (WT) ABCA4. Here, we show that the p.Asn965Ser ABCA4 variant expresses at half the level of WT ABCA4, partially mislocalizes to the endoplasmic reticulum (ER) of photoreceptors, is devoid of N-Ret-PE activated ATPase activity, and causes an increase in autofluorescence and the bisretinoid A2E associated with lipofuscin deposits in retinal pigment epithelial cells as found in Stargardt patients and Abca4 knockout mice. We also show for the first time that a significant fraction of WT ABCA4 is retained in the inner segment of photoreceptors. On the basis of these studies we conclude that loss in substrate-dependent ATPase activity and protein misfolding are mechanisms underlying STGD1 associated with the p.Asn965Ser mutation in ABCA4. Functional and molecular modeling studies further suggest that similar pathogenic mechanisms are responsible for Tangiers disease associated with the p.Asn935Ser (N935S) mutation in the NBD1 Walker A motif of ABCA1.
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Affiliation(s)
- Laurie L Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada V6T 1Z3
| | - Daniel Wahl
- School of Engineering Science, Simon Fraser University, Burnaby, BC, Canada V5A 1S6
| | - Marinko V Sarunic
- School of Engineering Science, Simon Fraser University, Burnaby, BC, Canada V5A 1S6
| | - Robert S Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC, Canada V6T 1Z3.,Department of Ophthalmology and Visual Sciences, University of British Columbia, Vancouver, BC, Canada V5Z 3N9
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Abstract
The transport of specific molecules across lipid membranes is an essential function of all living organisms. The processes are usually mediated by specific transporters. One of the largest transporter families is the ATP-binding cassette (ABC) family. More than 40 ABC transporters have been identified in human, which are divided into 7 subfamilies (ABCA to ABCG) based on their gene structure, amino acid sequence, domain organization, and phylogenetic analysis. Of them, at least 11 ABC transporters including P-glycoprotein (P-GP/ABCB1), multidrug resistance-associated proteins (MRPs/ABCCs), and breast cancer resistance protein (BCRP/ABCG2) are involved in multidrug resistance (MDR) development. These ABC transporters are expressed in various tissues such as the liver, intestine, kidney, and brain, playing important roles in absorption, distribution, and excretion of drugs. Some ABC transporters are also involved in diverse cellular processes such as maintenance of osmotic homeostasis, antigen processing, cell division, immunity, cholesterol, and lipid trafficking. Several human diseases such as cystic fibrosis, sitosterolemia, Tangier disease, intrahepatic cholestasis, and retinal degeneration are associated with mutations in corresponding transporters. This chapter will describe function and expression of several ABC transporters (such as P-GP, BCRP, and MRPs), their substrates and inhibitors, as well as their clinical significance.
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Affiliation(s)
- Xiaodong Liu
- China Pharmaceutical University, Nanjing, China.
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47
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Substrate polyspecificity and conformational relevance in ABC transporters: new insights from structural studies. Biochem Soc Trans 2018; 46:1475-1484. [PMID: 30514765 DOI: 10.1042/bst20180146] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2018] [Revised: 10/09/2018] [Accepted: 10/30/2018] [Indexed: 12/17/2022]
Abstract
Transport of molecules and ions across biological membranes is an essential process in all organisms. It is carried out by a range of evolutionarily conserved primary and secondary transporters. A significant portion of the primary transporters belong to the ATP-binding cassette (ABC) superfamily, which utilise the free-energy from ATP hydrolysis to shuttle many different substrates across various biological membranes, and consequently, are involved in both normal and abnormal physiology. In humans, ABC transporter-associated pathologies are perhaps best exemplified by multidrug-resistance transporters that efflux many xenobiotic compounds due to their remarkable substrate polyspecificity. Accordingly, understanding the transport mechanism(s) is of great significance, and indeed, much progress has been made in recent years, particularly from structural studies on ABC exporters. Consequently, the general mechanism of 'alternate access' has been modified to describe individual transporter nuances, though some aspects of the transport process remain unclear. Moreover, as new information has emerged, the physiological relevance of the 'open-apo' conformation of MsbA (a bacterial exporter) has been questioned and, by extension, its contribution to mechanistic models. We present here a comprehensive overview of the most recently solved structures of ABC exporters, focusing on new insights regarding the nature of substrate polyspecificity and the physiological relevance of the 'open-apo' conformation. This review evaluates the claim that the latter may be an artefact of detergent solubilisation, and we hypothesise that the biophysical properties of the membrane play a key role in the function of ABC exporters allowing them to behave like a 'spring-hinge' during their transport cycle.
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48
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ABC transporters as cancer drivers: Potential functions in cancer development. Biochim Biophys Acta Gen Subj 2018; 1863:52-60. [PMID: 30268729 DOI: 10.1016/j.bbagen.2018.09.019] [Citation(s) in RCA: 83] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2018] [Revised: 08/30/2018] [Accepted: 09/25/2018] [Indexed: 02/07/2023]
Abstract
BACKGROUND ABC transporters have attracted considerable attention for their function as drug transporters in a broad range of tumours and are therefore considered as major players in cancer chemoresistance. However, less attention has been focused on their potential role as active players in cancer development and progression. SCOPE OF REVIEW This review presents the evidence suggesting that ABC transporters might have a more active role in cancer other than the well known involvement in multidrug resistance and discusses the potential strategies to target each ABC transporter for a specific tumour setting. MAJOR CONCLUSIONS Emerging evidence suggests that ABC transporters are able to transport bioactive molecules capable of playing key roles in tumour development. Characterization of the effects of these transporters in specific cancer settings opens the possibility for the development of personalized treatments. GENERAL SIGNIFICANCE A more targeted approach of ABC transporters should be implemented that considers which specific transporter is playing a major role in a particular tumour setting in order to achieve a more successful outcome for ABC transporters inhibitors in cancer therapy.
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49
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Salles MV, Motta FL, Martin R, Filippelli-Silva R, Dias da Silva E, Varela P, Costa KA, Chiang JP, Pesquero JB, Sallum JMF. Variants in the ABCA4 gene in a Brazilian population with Stargardt disease. Mol Vis 2018; 24:546-559. [PMID: 30093795 PMCID: PMC6070459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Accepted: 07/30/2018] [Indexed: 11/24/2022] Open
Abstract
PURPOSE The aim of this study was to analyze and report pathogenic variants in the ABCA4 gene in Brazilian patients with a clinical diagnosis of Stargardt disease. METHODS This retrospective study evaluated variants in the ABCA4 gene in Brazilian patients with Stargardt disease. The patients' visual acuity and age of symptom onset were obtained from previous medical records. The patients were classified according to the autofluorescence patterns. RESULTS Fifty patients aged between 10 and 65 years from 44 families were included in the study. Among these cases, the mean age of symptom onset was 14 years (range, 5-40 years). ABCA4 gene sequencing was conclusive in 40 patients (80%), negative in two patients (4%), and inconclusive in eight patients (16%). Four families carried homozygous pathogenic variants. Segregation analysis results were available for 23 families. One novel variant was found: p.Ala2084Pro. The most frequent pathogenic variant in this group was p.Arg602Trp (12/100 alleles). Based on the phenotypic characteristics assessed with fundus autofluorescence imaging, 12 patients were classified as having type I phenotype, 16 as having type II, and 18 patients as having type III. The cases classified as type III phenotype included patients who were homozygous for the p.Asn96Asp and p.Arg2030* variants. One patient with a type I phenotype carried the homozygous intronic variant c.3862+1G>A. CONCLUSIONS Next-generation sequencing was effective for the molecular diagnosis of genetic diseases and specifically allowed a conclusive diagnosis in 80% (40/50) of the patients. As the ABCA4 gene does not show a preferential region for pathogenic variants, the diagnosis of Stargardt disease depends on broader analysis of the gene. The most common pathogenic variants in the ABCA4 gene described in the literature were also found in these Brazilian patients. Although some genotype-phenotype correlations were found, more studies regarding the progression of Stargardt disease will help increase our understanding of the pathogenicity of these gene variants.
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Affiliation(s)
- Mariana Vallim Salles
- Department of Ophthalmology and Visual Sciences, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
| | - Fabiana Louise Motta
- Department of Ophthalmology and Visual Sciences, Federal University of São Paulo (UNIFESP), São Paulo, Brazil,Department of Biophysics, UNIFESP, São Paulo, Brazil
| | - Renan Martin
- Department of Biophysics, UNIFESP, São Paulo, Brazil
| | | | | | | | - Kárita Antunes Costa
- Department of Ophthalmology and Visual Sciences, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
| | | | | | - Juliana-Maria Ferraz Sallum
- Department of Ophthalmology and Visual Sciences, Federal University of São Paulo (UNIFESP), São Paulo, Brazil
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50
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Taubitz T, Tschulakow AV, Tikhonovich M, Illing B, Fang Y, Biesemeier A, Julien-Schraermeyer S, Schraermeyer U. Ultrastructural alterations in the retinal pigment epithelium and photoreceptors of a Stargardt patient and three Stargardt mouse models: indication for the central role of RPE melanin in oxidative stress. PeerJ 2018; 6:e5215. [PMID: 30038866 PMCID: PMC6054867 DOI: 10.7717/peerj.5215] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2018] [Accepted: 06/19/2018] [Indexed: 12/18/2022] Open
Abstract
Background Stargardt disease (SD) is characterized by the accumulation of the age-pigment lipofuscin in the retinal pigment epithelium (RPE) and subsequent neuroretinal degeneration. The disease leads to vision loss early in life. Here, we investigate age-dependent ultrastructural changes in three SD mouse models: albino Abca4-/- and pigmented Abca4-/- and Abca4-/-.Rdh8-/- mice. Since we found indications for oxidative stress primarily in albino SD mice, we tested RPE melanin for its antioxidative capabilities. Methods SD mouse eyes were investigated by light, fluorescence and electron microscopy and were compared to the respective albino and pigmented wild type mice and to a human donor SD eye. To confirm the role of RPE melanin in scavenging oxidative stress, melanin from S. officinalis as a standard and porcine RPE were tested for their capability to quench superoxide anions. Results Histological alterations indicative of oxidative stress and/or lysosomal dysfunction were present in albino Abca4-/- and Abca4-/-.Rdh8-/- mice. Retinal damage, such as inner segment rupture and pyknotic or free photoreceptor nuclei in the subretinal space and RPE vacuolization were exclusively found in albino Abca4-/- mice. Shortened and disorganized photoreceptor outer segments and dead RPE cells were found in albino Abca4-/- and Abca4-/-.Rdh8-/- mice, with earlier onset in albino Abca4-/- mice. Undegraded phagosomes and lipofuscin accumulation were present in the RPE of all three SD strains, but numbers were highest in Abca4-/-.Rdh8-/- mice. Lipofuscin morphology differed between SD strains: (melano-)lipofuscin granules in pigmented Abca4-/- mice had a homogenous electron density and sharp demarcations, while lipofuscin in albino Abca4-/- mice had a flocculent electron density and often lacked a surrounding membrane, indicating loss of lysosomal integrity. Young Abca4-/-.Rdh8-/- mice showed (melano-)lipofuscin granules with homogenous electron density, while in aged animals granules with flocculent electron density predominated. Both strains of pigmented SD mice had melanolipofuscin clusters as found in the human SD eye. Like melanin from S. officinalis, porcine RPE melanin can also quench superoxide anions. Discussion The presented pathologies in albino Abca4-/- and Abca4-/-.Rdh8-/- mice suggest oxidative stress and/or lysosomal dysfunction within the RPE. Since albino Abca4-/- mice have the earliest onset and severest damage and as absence of melanin and also melanin turnover with age are known to diminish RPEs anti-oxidative properties, we assume that RPE melanin plays a role in SD related damages. A lack of pathology in pigmented Abca4-/- mice due to lower stress levels as compared to the Abca4-/-.Rdh8-/- mice underlines this hypothesis. It is also supported by the finding that RPE melanin can quench superoxide anions. We therefore suppose that RPE melanin is important in retinal health and we discuss its role as an oxidative stress scavenger.
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Affiliation(s)
- Tatjana Taubitz
- Division of Experimental Vitreoretinal Surgery, Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
| | - Alexander V Tschulakow
- Division of Experimental Vitreoretinal Surgery, Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
| | - Marina Tikhonovich
- Division of Experimental Vitreoretinal Surgery, Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
| | - Barbara Illing
- Division of Experimental Vitreoretinal Surgery, Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
| | - Yuan Fang
- Division of Experimental Vitreoretinal Surgery, Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
| | - Antje Biesemeier
- Division of Experimental Vitreoretinal Surgery, Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
| | - Sylvie Julien-Schraermeyer
- Division of Experimental Vitreoretinal Surgery, Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
| | - Ulrich Schraermeyer
- Division of Experimental Vitreoretinal Surgery, Centre for Ophthalmology, University of Tuebingen, Tuebingen, Germany
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