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Xu T, Molday L, Molday R. Retinal-phospholipid Schiff-base conjugates and their interaction with ABCA4, the ABC transporter associated with Stargardt Disease. J Biol Chem 2023; 299:104614. [PMID: 36931393 PMCID: PMC10127136 DOI: 10.1016/j.jbc.2023.104614] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2022] [Revised: 03/10/2023] [Accepted: 03/11/2023] [Indexed: 03/17/2023] Open
Abstract
N-retinylidene-phosphatidylethanolamine (N-Ret-PE), the Schiff-base conjugate formed through the reversible reaction of retinal (Vitamin A-aldehyde) and phosphatidylethanolamine, plays a crucial role in the visual cycle and visual pigment photoregeneration. However, N-Ret-PE can react with another molecule of retinal to form toxic di-retinoids if not removed from photoreceptors through its transport across photoreceptor membranes by the ATP-binding-cassette transporter ABCA4. Loss-of-function mutations in ABCA4 are known to cause Stargardt disease (STGD1), an inherited retinal degenerative disease associated with the accumulation of fluorescent di-retinoids and severe loss in vision. A larger assessment of retinal-phospholipid Schiff-base conjugates in photoreceptors is needed, along with further investigation of ABCA4 residues important for N-Ret-PE binding. In this study we show that N-Ret-PE formation is dependent on pH and phospholipid content. When retinal is added to liposomes or photoreceptor membranes, 40-60% is converted to N-Ret-PE at physiological pH. Phosphatidylserine and taurine also react with retinal to form N-retinylidene-phosphatidylserine (N-Ret-PS) and N-retinylidene-taurine, respectively, but at significantly lower levels. N-Ret-PS is not a substrate for ABCA4 and reacts poorly with retinal to form di-retinoids. Additionally, amino acid residues within the binding pocket of ABCA4 that contribute to its interaction with N-Ret-PE were identified and characterized using site-directed mutagenesis together with functional and binding assays. Substitution of arginine residues and hydrophobic residues with alanine or residues implicated in STGD1 significantly reduced or in some cases eliminated substrate-activated ATPase activity and substrate binding. Collectively, this study provides important insight into conditions which affect retinal-phospholipid Schiff-base formation and mechanisms underlying the pathogenesis of STGD1.
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Affiliation(s)
- Tongzhou Xu
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, B.C. V6T 1Z3 Canada
| | - LaurieL Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, B.C. V6T 1Z3 Canada
| | - RobertS Molday
- Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, B.C. V6T 1Z3 Canada.
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Krašovec T, Volk M, Šuštar Habjan M, Hawlina M, Vidović Valentinčič N, Fakin A. The Clinical Spectrum and Disease Course of DRAM2 Retinopathy. Int J Mol Sci 2022; 23:7398. [PMID: 35806404 PMCID: PMC9266529 DOI: 10.3390/ijms23137398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Revised: 06/22/2022] [Accepted: 06/28/2022] [Indexed: 11/26/2022] Open
Abstract
Pathogenic variants in DNA-damage regulated autophagy modulator 2 gene (DRAM2) cause a rare autosomal recessive retinal dystrophy and its disease course is not well understood. We present two Slovenian patients harboring a novel DRAM2 variant and a detailed review of all 23 other patients described to date. Whole exome and whole genome sequencing were performed in the two patients, and both underwent ophthalmological examination with a 2-year follow-up. PubMed was searched for papers with clinical descriptions of DRAM2 retinopathy. Patient 1 was homozygous for a novel variant, p.Met1?, and presented with the acute onset of photopsia and retina-wide retinopathy at the age of 35 years. The patient was first thought to have an autoimmune retinopathy and was treated with mycophenolate mofetil, which provided some symptomatic relief. Patient 2 was compound heterozygous for p.Met1? and p.Leu246Pro and presented with late-onset maculopathy at the age of 59 years. On review, patients with DRAM2 retinopathy usually present in the third decade with central visual loss, outer retinal layer loss on optical coherence tomography and a hyperautofluorescent ring on fundus autofluorescence. Either cone–rod or rod–cone dystrophy phenotype is observed on electroretinography, reflecting the importance of DRAM2 in both photoreceptor types. Non-null variants can result in milder disease.
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Abstract
Retinitis pigmentosa (RP) belongs to a group of pigmentary retinopathies. It is the most common form of inherited retinal dystrophy, characterized by progressive degradation of photoreceptors that leads to nyctalopia, and ultimately, complete vision loss. RP is distinguished by the continuous retinal degeneration that progresses from the mid-periphery to the central and peripheral retina. RP was first described and named by Franciscus Cornelius Donders in the year 1857. It is one of the leading causes of bilateral blindness in adults, with an incidence of 1 in 3000 people worldwide. In this review, we are going to focus on the genetic heterogeneity of this disease, which is provided by various inheritance patterns, numerosity of variations and inter-/intra-familial variations based upon penetrance and expressivity. Although over 90 genes have been identified in RP patients, the genetic cause of approximately 50% of RP cases remains unknown. Heterogeneity of RP makes it an extremely complicated ocular impairment. It is so complicated that it is known as “fever of unknown origin”. For prognosis and proper management of the disease, it is necessary to understand its genetic heterogeneity so that each phenotype related to the various genetic variations could be treated.
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Affiliation(s)
- Aarti Bhardwaj
- Department of Genetics, M. D. University, Rohtak, Haryana, India
| | - Anshu Yadav
- Department of Genetics, M. D. University, Rohtak, Haryana, India
| | - Manoj Yadav
- Department of Genetics, M. D. University, Rohtak, Haryana, India
| | - Mukesh Tanwar
- Department of Genetics, M. D. University, Rohtak, Haryana, India
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Chan LW, Sung YC, Wu DC, Chen CY, Yang CH, Yang CM, Chen PL, Chen TC. PREDICTED PROTEIN STRUCTURE VARIATIONS INDICATE THE CLINICAL PRESENTATION OF CYP4V2-RELATED BIETTI CRYSTALLINE DYSTROPHY. Retina 2022; 42:797-806. [PMID: 34923510 DOI: 10.1097/iae.0000000000003381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
PURPOSE To investigate the relationship between different CYP4V2 disease-causing variants and disease severity in Bietti crystalline dystrophy (BCD). METHODS Twenty-one subjects from 19 unrelated families with a clinical diagnosis of BCD were enrolled. A novel severity prediction score for BCD based on the predicted molecular impact of CYP4V2 variants was applied for grouping and subsequent analyses. The more severe variants led to less CYP4V2 protein function preservation and a higher severity prediction score. RESULTS All subjects harbored two alleles of CYP4V2 disease-causing variants, of which c.802-8_810del17insGC was the most prevalent (14/21, 66.67%) and c.1507G>C was novel. According to the severity score, the subjects were categorized into severe, moderate, and mild groups with different preservation of central vision (mean logMAR visual acuity 0.95 ± 0.82, 0.89 ± 1.22, and 0.56 ± 0.64, respectively). The patients with a lower severity score had slower disease progression. CONCLUSION This is the first cohort study of BCD in Taiwan, and we established a novel BCD severity index based on the molecular impact of different CYP4V2 variants. More severe impairment of CYP4V2 protein led to a more severe disease course with earlier progression. Our results could be helpful in identifying a therapeutic window for patients with BCD.
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Affiliation(s)
- Li-Wei Chan
- Department of Ophthalmology, Taipei Tzu Chi Hospital, The Buddhist Tzu Chi Medical Foundation, Taipei, Taiwan
| | - Yu-Chi Sung
- Department of Medical Education, National Taiwan University Hospital, Taipei, Taiwan
- Department of Ophthalmology, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan
| | - Dung-Chi Wu
- Genome and Systems Biology Degree Program, Academia Sinica and National Taiwan University, Taipei, Taiwan
| | | | - Chang-Hao Yang
- Department of Ophthalmology, National Taiwan University, Taipei, Taiwan
- Department of Ophthalmology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Chung-May Yang
- Department of Ophthalmology, National Taiwan University, Taipei, Taiwan
- Department of Ophthalmology, College of Medicine, National Taiwan University, Taipei, Taiwan
| | - Pei-Lung Chen
- Graduate Institute of Clinical Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan
- Graduate Institute of Medical Genomics and Proteomics, College of Medicine, National Taiwan University, Taipei, Taiwan; and
- Department of Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan
| | - Ta-Ching Chen
- Department of Ophthalmology, National Taiwan University, Taipei, Taiwan
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Dong H, Wang M, Li Q. Exosomal miR-4488 and miR-1273g-5p inhibit the epithelial-mesenchymal transition of transforming growth factor β2-mediated retinal pigment epithelial cells by targeting ATP-binding cassette A4. Bioengineered 2021; 12:9693-9706. [PMID: 34592902 PMCID: PMC8810054 DOI: 10.1080/21655979.2021.1987068] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Exosomal microRNAs (miRNAs) have been shown to be involved in the regulation of many disease progression, including proliferative vitreoretinopathy (PVR). However, the roles of exosomal miR-4488 and miR-1273g-5p in PVR progression have not been demonstrated. Transforming growth factor β2 (TGF-β2)-induced ARPE-19 cells were used to stimulate the epithelial-mesenchymal transition (EMT) of cells. Exosomes derived from TGF-β2-induced ARPE-19 cells were identified by transmission electron microscopy and nanoparticle tracking analysis. The expression levels of miR-4488, miR-1273g-5p and ATP-binding cassette A4 (ABCA4) were measured by quantitative real-time PCR. The promotion levels of exosomes markers, EMT markers, apoptosis markers and ABCA4 were determined by western blot analysis. The migration, invasion and apoptosis of cells were determined by transwell assay, wound healing assay and flow cytometry. Our data showed that miR-4488 and miR-1273g-5p were lowly expressed in TGF-β2-induced ARPE-19 cells. Overexpressed exosomal miR-4488 and miR-1273g-5p could inhibit the EMT, migration, invasion, and promote apoptosis in TGF-β2-induced ARPE-19 cells. In addition, ABCA4 was a target of miR-4488 and miR-1273g-5p. Overexpressed ABCA4 also could reverse the negatively regulation of exosomal miR-4488 and miR-1273g-5p on the EMT, migration, and invasion of TGF-β2-induced ARPE-19 cells. In conclusion, our data showed that exosomal miR-4488 and miR-1273g-5p could inhibit TGF-β2-stimulated EMT in ARPE-19 cells through targeting ABCA4.
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Affiliation(s)
- Hongtao Dong
- Department of Ophthalmology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou City, 450052, Henan, China
| | - Menghua Wang
- Department of Ophthalmology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou City, 450052, Henan, China
| | - Qiuming Li
- Department of Ophthalmology, the First Affiliated Hospital of Zhengzhou University, Zhengzhou City, 450052, Henan, China
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Abstract
Stargardt disease (STGD1) is an autosomal recessive retinal dystrophy, characterised by bilateral progressive central vision loss and subretinal deposition of lipofuscin-like substances. Recent advances in molecular diagnosis and therapeutic options are complemented by the increasing recognition of new multimodal imaging biomarkers that may predict genotype and disease progression. Unique non-invasive imaging features of STDG1 are useful for gene variant interpretation and may even provide insight into the underlying molecular pathophysiology. In addition, pathognomonic imaging features of STGD1 have been used to train neural networks to improve time efficiency in lesion segmentation and disease progression measurements. This review will discuss the role of key imaging modalities, correlate imaging signs across varied STGD1 presentations and illustrate the use of multimodal imaging as an outcome measure in determining the efficacy of emerging STGD1 specific therapies.
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Affiliation(s)
- Rachael C. Heath Jeffery
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
- Department of OphthalmologyRoyal Perth HospitalPerthWestern AustraliaAustralia
| | - Fred K. Chen
- Centre for Ophthalmology and Visual Science (Incorporating Lions Eye Institute)The University of Western AustraliaNedlandsWestern AustraliaAustralia
- Department of OphthalmologyRoyal Perth HospitalPerthWestern AustraliaAustralia
- Australian Inherited Retinal Disease Registry and DNA Bank, Department of Medical Technology and PhysicsSir Charles Gairdner HospitalPerthWestern AustraliaAustralia
- Department of OphthalmologyPerth Children's HospitalNedlandsWestern AustraliaAustralia
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Abstract
PURPOSE OF REVIEW Stargardt disease is the most common inherited macular dystrophy but has a wide clinical spectrum, and several inherited macular dystrophies have phenotypic similarities that can make clinical diagnosis challenging. This review seeks to highlight key clinical and multimodal imaging features to aid clinicians in accurate diagnosis. RECENT FINDINGS Multimodal imaging has provided additional information to aid in the diagnosis of Stargardt disease and its masquerades. These data from multimodal imaging are important to correlate with findings from clinical examination to help support the clinical diagnosis or guide molecular investigations. SUMMARY This review highlights the key similarities and differences, in history, clinical examination and multimodal imaging, to help distinguish between Stargardt disease and other macular dystrophies. These findings can help direct a focused molecular analysis for accurate diagnosis, which is critical in the era of gene and stem cell therapies.
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Affiliation(s)
- Aaron M Ricca
- Institute for Vision Research, Department of Ophthalmology and Visual Sciences, Carver College of Medicine, University of Iowa, Iowa City, Iowa, USA
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