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Hultgren NW, Zhou T, Williams DS. Machine learning-based 3D segmentation of mitochondria in polarized epithelial cells. Mitochondrion 2024; 76:101882. [PMID: 38599302 DOI: 10.1016/j.mito.2024.101882] [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: 04/25/2023] [Revised: 03/18/2024] [Accepted: 04/07/2024] [Indexed: 04/12/2024]
Abstract
Mitochondria are dynamic organelles that alter their morphological characteristics in response to functional needs. Therefore, mitochondrial morphology is an important indicator of mitochondrial function and cellular health. Reliable segmentation of mitochondrial networks in microscopy images is a crucial initial step for further quantitative evaluation of their morphology. However, 3D mitochondrial segmentation, especially in cells with complex network morphology, such as in highly polarized cells, remains challenging. To improve the quality of 3D segmentation of mitochondria in super-resolution microscopy images, we took a machine learning approach, using 3D Trainable Weka, an ImageJ plugin. We demonstrated that, compared with other commonly used methods, our approach segmented mitochondrial networks effectively, with improved accuracy in different polarized epithelial cell models, including differentiated human retinal pigment epithelial (RPE) cells. Furthermore, using several tools for quantitative analysis following segmentation, we revealed mitochondrial fragmentation in bafilomycin-treated RPE cells.
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Affiliation(s)
- Nan W Hultgren
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles, CA 90095, USA.
| | - Tianli Zhou
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles, CA 90095, USA
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles, CA 90095, USA; Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA 90095, USA; Molecular Biology Institute, University of California, Los Angeles, CA 90095, USA; Brain Research Institute, University of California, Los Angeles, CA 90095, USA.
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2
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Iliescu DA, Ghita AC, Ilie LA, Voiculescu SE, Geamanu A, Ghita AM. Non-Neovascular Age-Related Macular Degeneration Assessment: Focus on Optical Coherence Tomography Biomarkers. Diagnostics (Basel) 2024; 14:764. [PMID: 38611677 PMCID: PMC11011935 DOI: 10.3390/diagnostics14070764] [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: 02/28/2024] [Revised: 03/27/2024] [Accepted: 03/31/2024] [Indexed: 04/14/2024] Open
Abstract
The imagistic evaluation of non-neovascular age-related macular degeneration (AMD) is crucial for diagnosis, monitoring progression, and guiding management of the disease. Dry AMD, characterized primarily by the presence of drusen and retinal pigment epithelium atrophy, requires detailed visualization of the retinal structure to assess its severity and progression. Several imaging modalities are pivotal in the evaluation of non-neovascular AMD, including optical coherence tomography, fundus autofluorescence, or color fundus photography. In the context of emerging therapies for geographic atrophy, like pegcetacoplan, it is critical to establish the baseline status of the disease, monitor the development and expansion of geographic atrophy, and to evaluate the retina's response to potential treatments in clinical trials. The present review, while initially providing a comprehensive description of the pathophysiology involved in AMD, aims to offer an overview of the imaging modalities employed in the evaluation of non-neovascular AMD. Special emphasis is placed on the assessment of progression biomarkers as discerned through optical coherence tomography. As the landscape of AMD treatment continues to evolve, advanced imaging techniques will remain at the forefront, enabling clinicians to offer the most effective and tailored treatments to their patients.
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Affiliation(s)
- Daniela Adriana Iliescu
- Department of Physiology, “Carol Davila” University of Medicine and Pharmacy, 8 Eroii Sanitari Bld., 050474 Bucharest, Romania; (S.E.V.); (A.M.G.)
- Ocularcare Ophthalmology Clinic, 128 Ion Mihalache Bld., 012244 Bucharest, Romania; (A.C.G.); (L.A.I.)
| | - Ana Cristina Ghita
- Ocularcare Ophthalmology Clinic, 128 Ion Mihalache Bld., 012244 Bucharest, Romania; (A.C.G.); (L.A.I.)
| | - Larisa Adriana Ilie
- Ocularcare Ophthalmology Clinic, 128 Ion Mihalache Bld., 012244 Bucharest, Romania; (A.C.G.); (L.A.I.)
| | - Suzana Elena Voiculescu
- Department of Physiology, “Carol Davila” University of Medicine and Pharmacy, 8 Eroii Sanitari Bld., 050474 Bucharest, Romania; (S.E.V.); (A.M.G.)
| | - Aida Geamanu
- Ophthalmology Department, Bucharest University Emergency Hospital, 169 Independence Street, 050098 Bucharest, Romania;
| | - Aurelian Mihai Ghita
- Department of Physiology, “Carol Davila” University of Medicine and Pharmacy, 8 Eroii Sanitari Bld., 050474 Bucharest, Romania; (S.E.V.); (A.M.G.)
- Ocularcare Ophthalmology Clinic, 128 Ion Mihalache Bld., 012244 Bucharest, Romania; (A.C.G.); (L.A.I.)
- Ophthalmology Department, Bucharest University Emergency Hospital, 169 Independence Street, 050098 Bucharest, Romania;
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Grubaugh CR, Dhingra A, Prakash B, Montenegro D, Sparrow JR, Daniele LL, Curcio CA, Bell BA, Hussain MM, Boesze-Battaglia K. Microsomal triglyceride transfer protein is necessary to maintain lipid homeostasis and retinal function. FASEB J 2024; 38:e23522. [PMID: 38445789 PMCID: PMC10949407 DOI: 10.1096/fj.202302491r] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2023] [Revised: 02/07/2024] [Accepted: 02/16/2024] [Indexed: 03/07/2024]
Abstract
Lipid processing by the retinal pigment epithelium (RPE) is necessary to maintain retinal health and function. Dysregulation of retinal lipid homeostasis due to normal aging or age-related disease triggers lipid accumulation within the RPE, on Bruch's membrane (BrM), and in the subretinal space. In its role as a hub for lipid trafficking into and out of the neural retina, the RPE packages a significant amount of lipid into lipid droplets for storage and into apolipoprotein B (APOB)-containing lipoproteins (Blps) for export. Microsomal triglyceride transfer protein (MTP), encoded by the MTTP gene, is essential for Blp assembly. Herein we test the hypothesis that MTP expression in the RPE is essential to maintain lipid balance and retinal function using the newly generated RPEΔMttp mouse model. Using non-invasive ocular imaging, electroretinography, and histochemical and biochemical analyses we show that genetic depletion of Mttp from the RPE results in intracellular lipid accumulation, increased photoreceptor-associated cholesterol deposits, and photoreceptor cell death, and loss of rod but not cone function. RPE-specific reduction in Mttp had no significant effect on plasma lipids and lipoproteins. While APOB was decreased in the RPE, most ocular retinoids remained unchanged, with the exception of the storage form of retinoid, retinyl ester. Thus suggesting that RPE MTP is critical for Blp synthesis and assembly but is not directly involved in plasma lipoprotein metabolism. These studies demonstrate that RPE-specific MTP expression is necessary to establish and maintain retinal lipid homeostasis and visual function.
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Affiliation(s)
- Catharina R. Grubaugh
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Anuradha Dhingra
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Binu Prakash
- Department of Foundations of Medicine, New York University Grossman Long Island School of Medicine, Mineola, NY, 11501 USA
| | - Diego Montenegro
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY, 10027 USA
| | - Janet R. Sparrow
- Department of Ophthalmology and Department of Pathology and Cell Biology, Columbia University, New York, NY, 10027 USA
| | - Lauren L. Daniele
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Christine A. Curcio
- Department of Ophthalmology and Visual Sciences, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Brent A. Bell
- Department of Ophthalmology, University of Pennsylvania, Philadelphia, PA, 19104 USA
| | - M. Mahmood Hussain
- Department of Foundations of Medicine, New York University Grossman Long Island School of Medicine, Mineola, NY, 11501 USA
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
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4
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Taninaka A, Kurokawa H, Kamiyanagi M, Ochiai T, Arashida Y, Takeuchi O, Matsui H, Shigekawa H. Polphylipoprotein-induced autophagy mechanism with high performance in photodynamic therapy. Commun Biol 2023; 6:1212. [PMID: 38017279 PMCID: PMC10684771 DOI: 10.1038/s42003-023-05598-0] [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: 09/01/2023] [Accepted: 11/16/2023] [Indexed: 11/30/2023] Open
Abstract
Polphylipoprotein (PLP) is a recently developed nanoparticle with high biocompatibility and tumor selectivity, and which has demonstrated unprecedentedly high performance photosensitizer in photodynamic therapy (PDT) and photodynamic diagnosis. On the basis of these discoveries, PLP is anticipated to have a very high potential for PDT. However, the mechanism by which PLP kills cancer cells effectively has not been sufficiently clarified. To comprehensively understand the PLP-induced PDT processes, we conduct multifaceted experiments using both normal cells and cancer cells originating from the same sources, namely, RGM1, a rat gastric epithelial cell line, and RGK1, a rat gastric mucosa-derived cancer-like mutant. We reveal that PLP enables highly effective cancer treatment through PDT by employing a unique mechanism that utilizes the process of autophagy. The dynamics of PLP-accumulated phagosomes immediately after light irradiation are found to be completely different between normal cells and cancer cells, and it becomes clear that this difference results in the manifestation of the characteristic effect of PDT when using PLP. Since PLP is originally developed as a drug delivery agent, this study also suggests the potential for intracellular drug delivery processes through PLP-induced autophagy.
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Affiliation(s)
- Atsushi Taninaka
- Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan
- TAKANO Co. LTD. Miyada-mura, Kamiina-gun, Nagano, 399-4301, Japan
| | - Hiromi Kurokawa
- Fuculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan
| | - Mayuka Kamiyanagi
- Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan
| | - Takahiro Ochiai
- TAKANO Co. LTD. Miyada-mura, Kamiina-gun, Nagano, 399-4301, Japan
| | - Yusuke Arashida
- Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan
| | - Osamu Takeuchi
- Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan
| | - Hirofumi Matsui
- Fuculty of Medicine, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan
| | - Hidemi Shigekawa
- Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8573, Japan.
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5
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Yu Y, Zhang Z, Yu Y. Timing of Phagosome Maturation Depends on Their Transport Switching from Actin to Microtubule Tracks. J Phys Chem B 2023; 127:9312-9322. [PMID: 37871280 PMCID: PMC10759163 DOI: 10.1021/acs.jpcb.3c05647] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2023]
Abstract
Phagosomes, specialized membrane compartments responsible for digesting internalized pathogens, undergo sequential dynamic and biochemical changes as they mature from nascent phagosomes to degradative phagolysosomes. Maturation of phagosomes depends on their transport along actin filaments and microtubules. However, the specific quantitative relationship between the biochemical transformation and transport dynamics remains poorly characterized. The autonomous nature of phagosomes, moving and maturing at different rates, makes understanding this relationship challenging. Addressing this challenge, in this study we engineered particle sensors to image and quantify single phagosomes' maturation. We found that as phagosomes move from the actin cortex to microtubule tracks, the timing of their actin-to-microtubule transition governs the duration of the early phagosome stage before acquiring degradative capacities. Prolonged entrapment of phagosomes in the actin cortex extends the early phagosome stage by delaying the dissociation of early endosome markers and phagosome acidification. Conversely, a shortened transition from actin- to microtubule-based movements causes the opposite effect on phagosome maturation. These results suggest that the actin- and microtubule-based transport of phagosomes functions like a "clock" to coordinate the timing of biochemical events during phagosome maturation, which is crucial for effective pathogen degradation.
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Affiliation(s)
- Yanqi Yu
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, United States
| | - Zihan Zhang
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, United States
| | - Yan Yu
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405-7102, United States
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Gilmore WB, Hultgren NW, Chadha A, Barocio SB, Zhang J, Kutsyr O, Flores-Bellver M, Canto-Soler MV, Williams DS. Expression of two major isoforms of MYO7A in the retina: Considerations for gene therapy of Usher syndrome type 1B. Vision Res 2023; 212:108311. [PMID: 37586294 PMCID: PMC10984346 DOI: 10.1016/j.visres.2023.108311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Revised: 07/25/2023] [Accepted: 07/28/2023] [Indexed: 08/18/2023]
Abstract
Usher syndrome type 1B (USH1B) is a deaf-blindness disorder, caused by mutations in the MYO7A gene, which encodes the heavy chain of an unconventional actin-based motor protein. Here, we examined the two retinal isoforms of MYO7A, IF1 and IF2. We compared 3D models of the two isoforms and noted that the 38-amino acid region that is present in IF1 but absent from IF2 affects the C lobe of the FERM1 domain and the opening of a cleft in this potentially important protein binding domain. Expression of each of the two isoforms of human MYO7A and pig and mouse Myo7a was detected in the RPE and neural retina. Quantification by qPCR showed that the expression of IF2 was typically ∼ 7-fold greater than that of IF1. We discuss the implications of these findings for any USH1B gene therapy strategy. Given the current incomplete knowledge of the functions of each isoform, both isoforms should be considered for targeting both the RPE and the neural retina in gene augmentation therapies.
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Affiliation(s)
- W Blake Gilmore
- Department of Ophthalmology and Stein Eye Institute, Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Nan W Hultgren
- Department of Ophthalmology and Stein Eye Institute, Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Abhishek Chadha
- Department of Ophthalmology and Stein Eye Institute, Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Sonia B Barocio
- Department of Ophthalmology and Stein Eye Institute, Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Joyce Zhang
- Department of Ophthalmology and Stein Eye Institute, Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Oksana Kutsyr
- CellSight Ocular Stem Cell and Regeneration Research Program, Department of Ophthalmology, Sue Anschutz-Rodgers Eye Center, University of Colorado, School of Medicine, Aurora, CO, USA
| | - Miguel Flores-Bellver
- CellSight Ocular Stem Cell and Regeneration Research Program, Department of Ophthalmology, Sue Anschutz-Rodgers Eye Center, University of Colorado, School of Medicine, Aurora, CO, USA
| | - M Valeria Canto-Soler
- CellSight Ocular Stem Cell and Regeneration Research Program, Department of Ophthalmology, Sue Anschutz-Rodgers Eye Center, University of Colorado, School of Medicine, Aurora, CO, USA
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute, Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
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Tan LX, Germer CJ, Thamban T, La Cunza N, Lakkaraju A. Optineurin tunes outside-in signaling to regulate lysosome biogenesis and phagocytic clearance in the retina. Curr Biol 2023; 33:3805-3820.e7. [PMID: 37586372 PMCID: PMC10529777 DOI: 10.1016/j.cub.2023.07.031] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 06/16/2023] [Accepted: 07/19/2023] [Indexed: 08/18/2023]
Abstract
Balancing the competing demands of phagolysosomal degradation and autophagy is a significant challenge for phagocytic tissues. Yet how this plasticity is accomplished in health and disease is poorly understood. In the retina, circadian phagocytosis and degradation of photoreceptor outer segments by the postmitotic retinal pigment epithelium (RPE) are essential for healthy vision. Disrupted autophagy due to mechanistic target of rapamycin (mTOR) overactivation in the RPE is associated with blinding macular degenerations; however, outer segment degradation is unaffected in these diseases, indicating that distinct mechanisms regulate these clearance mechanisms. Here, using advanced imaging and mouse models, we identify optineurin as a key regulator that tunes phagocytosis and lysosomal capacity to meet circadian demands and helps prioritize outer segment clearance by the RPE in macular degenerations. High-resolution live-cell imaging implicates optineurin in scissioning outer segment tips prior to engulfment, analogous to microglial trogocytosis of neuronal processes. Optineurin is essential for recruiting light chain 3 (LC3), which anchors outer segment phagosomes to microtubules and facilitates phagosome maturation and fusion with lysosomes. This dynamically activates transcription factor EB (TFEB) to induce lysosome biogenesis in an mTOR-independent, transient receptor potential-mucolipin 1 (TRPML1)-dependent manner. RNA-seq analyses show that expression of TFEB target genes temporally tracks with optineurin recruitment and that lysosomal and autophagy genes are controlled by distinct transcriptional programs in the RPE. The unconventional plasma membrane-to-nucleus signaling mediated by optineurin ensures outer segment degradation under conditions of impaired autophagy in macular degeneration models. Independent regulation of these critical clearance mechanisms would help safeguard the metabolic fitness of the RPE throughout the organismal lifespan.
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Affiliation(s)
- Li Xuan Tan
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Colin J Germer
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Thushara Thamban
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Nilsa La Cunza
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA
| | - Aparna Lakkaraju
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA; Pharmaceutical Sciences and Pharmacogenomics Graduate Program, University of California, San Francisco, San Francisco, CA 94143, USA; Department of Anatomy, School of Medicine, University of California, San Francisco, San Francisco, CA 94143, USA.
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8
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Paterson C, Cannon J, Vargis E. The impact of early RPE cell junction loss on VEGF, Ang-2, and TIMP secretion in vitro. Mol Vis 2023; 29:87-101. [PMID: 37859808 PMCID: PMC10584031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2022] [Accepted: 07/14/2023] [Indexed: 10/21/2023] Open
Abstract
Purpose The retinal pigment epithelium (RPE) is an important tissue for maintaining a healthy retina. Retinal pigment epithelial cells help regulate nutrient transport to photoreceptors and are heavily pigmented to prevent light scattering. These cells also have junction proteins to form monolayers. Monolayers are key players in pathologies such as age-related macular degeneration (AMD), a leading cause of vision loss in older adults. During AMD, RPE cell detachment can occur, resulting in a loss of junctions. Losing junctions can increase the expression of pro-angiogenic vascular endothelial growth factor (VEGF). This overexpression can cause abnormal blood vessel growth or angiogenesis in the retina. Age-related macular degeneration treatments target VEGF to slow angiogenesis progression. However, other proteins, such as angiopoietin-2 (Ang-2) and the tissue inhibitor of metalloproteinase-1 (TIMP-1), may also play important roles, making them potential targets for treatment. Controlling RPE junction formation will help elucidate the relationship between RPE cell detachment and additional angiogenic factor secretion, lead to more therapeutics, and increase the efficacy of current treatments. Methods Micropatterning was used to control the spatial arrangement of primary porcine RPE cells using polydimethylsiloxane (PDMS) stencils. Patterns were formed into PDMS stencils to mimic 10%, 25%, and 50% overall detachment of the RPE monolayer. Zonula-occludens-1 (ZO-1), Ang-2, and VEGF were visualized using immunocytochemical (ICC) staining. An enzyme-linked immunosorbent assay (ELISA) was used to quantify extracellular Ang-2, VEGF, TIMP-1, and TIMP-2 levels. A rod outer segment (OS) phagocytosis assay was performed to determine how RPE junction loss directly affects photoreceptor support. Results The growth of primary porcine RPE cells was successfully controlled using stencils. Morphological changes and a decrease in pigmentation were observed, showing a decline in barrier and light absorption functions as degeneration increased. One day after stencil removal, junction proteins were delocalized, and angiogenic factor secretions were correlated with increased levels of detachment. Secretion levels of Ang-2 and TIMP-1 were significantly increased, whereas VEGF and TIMP-2 concentrations were not as affected by varying levels of detachment. OS phagocytosis appeared lower in RPE cells when ZO-1 was affected. Conclusions These results suggest a correlation between loss of junctions, abnormal angiogenic protein secretion, and reduced OS phagocytosis. Furthermore, Ang-2 and TIMP-1 proteins might be beneficial targets for AMD treatments, and their roles in retinal diseases deserve further investigation.
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Affiliation(s)
- Chase Paterson
- Utah State University, Biological Engineering, Logan, UT
| | - Jamen Cannon
- Utah State University, Biological Engineering, Logan, UT
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9
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Messinger JD, Brinkmann M, Kimble JA, Berlin A, Freund KB, Grossman GH, Ach T, Curcio CA. Ex Vivo OCT-Based Multimodal Imaging of Human Donor Eyes for Research into Age-Related Macular Degeneration. J Vis Exp 2023:10.3791/65240. [PMID: 37306417 PMCID: PMC10795012 DOI: 10.3791/65240] [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] [Indexed: 06/13/2023] Open
Abstract
A progression sequence for age-related macular degeneration (AMD) learned from optical coherence tomography (OCT)-based multimodal (MMI) clinical imaging could add prognostic value to laboratory findings. In this work, ex vivo OCT and MMI were applied to human donor eyes prior to retinal tissue sectioning. The eyes were recovered from non-diabetic white donors aged ≥80 years old, with a death-to-preservation time (DtoP) of ≤6 h. The globes were recovered on-site, scored with an 18 mm trephine to facilitate cornea removal, and immersed in buffered 4% paraformaldehyde. Color fundus images were acquired after anterior segment removal with a dissecting scope and an SLR camera using trans-, epi-, and flash illumination at three magnifications. The globes were placed in a buffer within a custom-designed chamber with a 60 diopter lens. They were imaged with spectral domain OCT (30° macula cube, 30 µm spacing, averaging = 25), near-infrared reflectance, 488 nm autofluorescence, and 787 nm autofluorescence. The AMD eyes showed a change in the retinal pigment epithelium (RPE), with drusen or subretinal drusenoid deposits (SDDs), with or without neovascularization, and without evidence of other causes. Between June 2016 and September 2017, 94 right eyes and 90 left eyes were recovered (DtoP: 3.9 ± 1.0 h). Of the 184 eyes, 40.2% had AMD, including early intermediate (22.8%), atrophic (7.6%), and neovascular (9.8%) AMD, and 39.7% had unremarkable maculas. Drusen, SDDs, hyper-reflective foci, atrophy, and fibrovascular scars were identified using OCT. Artifacts included tissue opacification, detachments (bacillary, retinal, RPE, choroidal), foveal cystic change, an undulating RPE, and mechanical damage. To guide the cryo-sectioning, OCT volumes were used to find the fovea and optic nerve head landmarks and specific pathologies. The ex vivo volumes were registered with the in vivo volumes by selecting the reference function for eye tracking. The ex vivo visibility of the pathology seen in vivo depends on the preservation quality. Within 16 months, 75 rapid DtoP donor eyes at all stages of AMD were recovered and staged using clinical MMI methods.
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Affiliation(s)
- Jeffrey D Messinger
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham Heersink School of Medicine
| | - Max Brinkmann
- Department of Ophthalmology, University Hospital of Zurich
| | - James A Kimble
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham Heersink School of Medicine
| | - Andreas Berlin
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham Heersink School of Medicine
| | - K Bailey Freund
- Vitreous Retina Macula Consultants of New York; Department of Ophthalmology, New York University Grossman School of Medicine
| | | | - Thomas Ach
- Department of Ophthalmology, University Hospital Bonn
| | - Christine A Curcio
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham Heersink School of Medicine;
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10
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Umapathy A, Torten G, Paniagua AE, Chung J, Tomlinson M, Lim C, Williams DS. Spatiotemporal Live-Cell Analysis of Photoreceptor Outer Segment Membrane Ingestion by the Retinal Pigment Epithelium Reveals Actin-Regulated Scission. J Neurosci 2023; 43:2653-2664. [PMID: 36878726 PMCID: PMC10089248 DOI: 10.1523/jneurosci.1726-22.2023] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2022] [Revised: 01/16/2023] [Accepted: 01/18/2023] [Indexed: 03/08/2023] Open
Abstract
The photoreceptor outer segment (OS) is the phototransductive organelle in the vertebrate retina. OS tips are regularly ingested and degraded by the adjacent retinal pigment epithelium (RPE), offsetting the addition of new disk membrane at the base of the OS. This catabolic role of the RPE is essential for photoreceptor health, with defects in ingestion or degradation underlying different forms of retinal degeneration and blindness. Although proteins required for OS tip ingestion have been identified, spatiotemporal analysis of the ingestion process in live RPE cells is lacking; hence, the literature reflects no common understanding of the cellular mechanisms that affect ingestion. We imaged live RPE cells from mice (both sexes) to elucidate the ingestion events in real time. Our imaging revealed roles for f-actin dynamics and specific dynamic localizations of two BAR (Bin-Amphiphysin-Rvs) proteins, FBP17 and AMPH1-BAR, in shaping the RPE apical membrane as it surrounds the OS tip. Completion of ingestion was observed to occur by scission of the OS tip from the remainder of the OS, with a transient concentration of f-actin forming around the site of imminent scission. Actin dynamics were also required for regulating the size of the ingested OS tip, and the time course of the overall ingestion process. The size of the ingested tip is consistent with the term "phagocytosis." However, phagocytosis usually refers to engulfment of an entire particle or cell, whereas our observations of OS tip scission indicate a process that is more specifically described as "trogocytosis," in which one cell "nibbles" another cell.SIGNIFICANCE STATEMENT The ingestion of the photoreceptor outer segment (OS) tips by the retinal pigment epithelium (RPE) is a dynamic cellular process that has fascinated scientists for 60 years. Yet its molecular mechanisms had not been addressed in living cells. We developed a live-cell imaging approach to investigate OS tip ingestion, and focused on the dynamic participation of actin filaments and membrane-shaping BAR proteins. We observed scission of OS tips for the first time, and were able to monitor local changes in protein concentration preceding, during, and following scission. Our approach revealed that actin filaments were concentrated at the site of OS scission and were required for regulating the size of the ingested OS tip and the time course of the ingestion process.
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Affiliation(s)
- Ankita Umapathy
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Gil Torten
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Antonio E Paniagua
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Julie Chung
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Madeline Tomlinson
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - Caleb Lim
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute, and Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, California 90095
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11
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Dhingra A, Tobias JW, Philp NJ, Boesze-Battaglia K. Transcriptomic Changes Predict Metabolic Alterations in LC3 Associated Phagocytosis in Aged Mice. Int J Mol Sci 2023; 24:6716. [PMID: 37047689 PMCID: PMC10095460 DOI: 10.3390/ijms24076716] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2023] [Revised: 03/28/2023] [Accepted: 03/28/2023] [Indexed: 04/14/2023] Open
Abstract
LC3b (Map1lc3b) plays an essential role in canonical autophagy and is one of several components of the autophagy machinery that mediates non-canonical autophagic functions. Phagosomes are often associated with lipidated LC3b to promote phagosome maturation in a process called LC3-associated phagocytosis (LAP). Specialized phagocytes, such as mammary epithelial cells, retinal pigment epithelial (RPE) cells, and sertoli cells, utilize LAP for optimal degradation of phagocytosed material, including debris. In the visual system, LAP is critical to maintain retinal function, lipid homeostasis, and neuroprotection. In a mouse model of retinal lipid steatosis-mice lacking LC3b (LC3b-/-), we observed increased lipid deposition, metabolic dysregulation, and enhanced inflammation. Herein, we present a non-biased approach to determine if loss of LAP mediated processes modulate the expression of various genes related to metabolic homeostasis, lipid handling, and inflammation. A comparison of the RPE transcriptome of WT and LC3b-/- mice revealed 1533 DEGs, with ~73% upregulated and 27% downregulated. Enriched gene ontology (GO) terms included inflammatory response (upregulated DEGs), fatty acid metabolism, and vascular transport (downregulated DEGs). Gene set enrichment analysis (GSEA) identified 34 pathways; 28 were upregulated (dominated by inflammation/related pathways) and 6 were downregulated (dominated by metabolic pathways). Analysis of additional gene families identified significant differences for genes in the solute carrier family, RPE signature genes, and genes with a potential role in age-related macular degeneration. These data indicate that loss of LC3b induces robust changes in the RPE transcriptome contributing to lipid dysregulation and metabolic imbalance, RPE atrophy, inflammation, and disease pathophysiology.
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Affiliation(s)
- Anuradha Dhingra
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - John W. Tobias
- Penn Genomics and Sequencing Core, Department of Genetics, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Nancy J. Philp
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Kathleen Boesze-Battaglia
- Department of Basic and Translational Sciences, University of Pennsylvania, Philadelphia, PA 19104, USA
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12
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Dhingra A, Tobias JW, Philp NJ, Boesze-Battaglia K. Transcriptomic changes predict metabolic alterations in LC3 associated phagocytosis in aged mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.14.532586. [PMID: 36993501 PMCID: PMC10054970 DOI: 10.1101/2023.03.14.532586] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/21/2023]
Abstract
LC3b ( Map1lc3b ) plays an essential role in canonical autophagy and is one of several components of the autophagy machinery that mediates non-canonical autophagic functions. Phagosomes are often associated with lipidated LC3b, to pro-mote phagosome maturation in a process called LC3-associated phagocytosis (LAP). Specialized phagocytes such as mammary epithelial cells, retinal pigment epithelial (RPE) cells, and sertoli cells utilize LAP for optimal degradation of phagocytosed material, including debris. In the visual system, LAP is critical to maintain retinal function, lipid homeostasis and neuroprotection. In a mouse model of retinal lipid steatosis - mice lacking LC3b ( LC3b -/- ), we observed increased lipid deposition, metabolic dysregulation and enhanced inflammation. Herein we present a non-biased approach to determine if loss of LAP mediated processes modulate the expression of various genes related to metabolic homeostasis, lipid handling, and inflammation. A comparison of the RPE transcriptome of WT and LC3b -/- mice revealed 1533 DEGs, with ~73% upregulated and 27% down-regulated. Enriched gene ontology (GO) terms included inflammatory response (upregulated DEGs), fatty acid metabolism and vascular transport (downregulated DEGs). Gene set enrichment analysis (GSEA) identified 34 pathways; 28 were upregulated (dominated by inflammation/related pathways) and 6 were downregulated (dominated by metabolic pathways). Analysis of additional gene families identified significant differences for genes in the solute carrier family, RPE signature genes, and genes with potential role in age-related macular degeneration. These data indicate that loss of LC3b induces robust changes in the RPE transcriptome contributing to lipid dysregulation and metabolic imbalance, RPE atrophy, inflammation, and disease pathophysiology.
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13
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Vedula P, Fina ME, Bell BA, Nikonov SS, Kashina A, Dong DW. β -actin is essential for structural integrity and physiological function of the retina. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.27.534392. [PMID: 37034790 PMCID: PMC10081178 DOI: 10.1101/2023.03.27.534392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Lack of non-muscle β -actin gene (Actb) leads to early embryonic lethality in mice, however mice with β - to γ -actin replacement develop normally and show no detectable phenotypes at young age. Here we investigated the effect of this replacement in the retina. During aging, these mice have accelerated de-generation of retinal structure and function, including elongated microvilli and defective mitochondria of retinal pigment epithelium (RPE), abnormally bulging photoreceptor outer segments (OS) accompanied by reduced transducin concentration and light sensitivity, and accumulation of autofluorescent microglia cells in the subretinal space between RPE and OS. These defects are accompanied by changes in the F-actin binding of several key actin interacting partners, including ezrin, myosin, talin, and vinculin known to play central roles in modulating actin cytoskeleton and cell adhesion and mediating the phagocytosis of OS. Our data show that β -actin protein is essential for maintaining normal retinal structure and function.
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14
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Paniagua AE, Sabharwal HS, Kethu K, Chang AW, Williams DS. Revisiting the Daily Timing of POS Phagocytosis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1415:515-519. [PMID: 37440080 DOI: 10.1007/978-3-031-27681-1_75] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/14/2023]
Abstract
Retinal pigment epithelium (RPE) cells daily ingest the tips of the photoreceptor outer segments (POSs), with phagosome number varying throughout a 24-h cycle. A major focus in the literature has been on a peak in phagosome concentration shortly after lights-on. Moreover, this peak has frequently been inferred to represent a peak in POS tip ingestion. Here, we have reviewed old and new literature on the daily cycle of phagosome number in the RPE and conclude that there is more variation in the timing of phagosome concentration peaks than is currently acknowledged. We also discuss that phagosome quantity is affected by the rate of phagosome degradation as well as the rate of ingestion; given that phagosome half-life may not be constant throughout the daily cycle, maximal POS ingestion may not necessarily coincide with a peak in phagosome concentration.
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Affiliation(s)
- Antonio E Paniagua
- Departments of Ophthalmology and Neurobiology, Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
| | - Harjas S Sabharwal
- Departments of Ophthalmology and Neurobiology, Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Kausalya Kethu
- Departments of Ophthalmology and Neurobiology, Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Andrew W Chang
- Departments of Ophthalmology and Neurobiology, Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - David S Williams
- Departments of Ophthalmology and Neurobiology, Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
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15
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Zihni C, Georgiadis A, Ramsden CM, Sanchez-Heras E, Haas AJ, Nommiste B, Semenyuk O, Bainbridge JWB, Coffey PJ, Smith AJ, Ali RR, Balda MS, Matter K. Spatiotemporal control of actomyosin contractility by MRCKβ signaling drives phagocytosis. J Biophys Biochem Cytol 2022; 221:213476. [PMID: 36121394 PMCID: PMC9485704 DOI: 10.1083/jcb.202012042] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 07/08/2022] [Accepted: 08/19/2022] [Indexed: 12/24/2022] Open
Abstract
Phagocytosis requires actin dynamics, but whether actomyosin contractility plays a role in this morphodynamic process is unclear. Here, we show that in the retinal pigment epithelium (RPE), particle binding to Mer Tyrosine Kinase (MerTK), a widely expressed phagocytic receptor, stimulates phosphorylation of the Cdc42 GEF Dbl3, triggering activation of MRCKβ/myosin-II and its coeffector N-WASP, membrane deformation, and cup formation. Continued MRCKβ/myosin-II activity then drives recruitment of a mechanosensing bridge, enabling cytoskeletal force transmission, cup closure, and particle internalization. In vivo, MRCKβ is essential for RPE phagocytosis and retinal integrity. MerTK-independent activation of MRCKβ signaling by a phosphomimetic Dbl3 mutant rescues phagocytosis in retinitis pigmentosa RPE cells lacking functional MerTK. MRCKβ is also required for efficient particle translocation from the cortex into the cell body in Fc receptor–mediated phagocytosis. Thus, conserved MRCKβ signaling at the cortex controls spatiotemporal regulation of actomyosin contractility to guide distinct phases of phagocytosis in the RPE and represents the principle phagocytic effector pathway downstream of MerTK.
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Affiliation(s)
- Ceniz Zihni
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Anastasios Georgiadis
- UCL Institute of Ophthalmology, University College London, London, UK.,Gene and Cell Therapy Group, UCL Institute of Ophthalmology, University College London, London, UK
| | - Conor M Ramsden
- UCL Institute of Ophthalmology, University College London, London, UK
| | | | - Alexis J Haas
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Britta Nommiste
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Olha Semenyuk
- UCL Institute of Ophthalmology, University College London, London, UK.,Gene and Cell Therapy Group, UCL Institute of Ophthalmology, University College London, London, UK
| | - James W B Bainbridge
- UCL Institute of Ophthalmology, University College London, London, UK.,Gene and Cell Therapy Group, UCL Institute of Ophthalmology, University College London, London, UK.,National Institute for Health and Care Research Biomedical Research Centre at Moorfields Eye Hospital National Health Service Foundation Trust, London, UK
| | - Peter J Coffey
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Alexander J Smith
- Gene and Cell Therapy Group, UCL Institute of Ophthalmology, University College London, London, UK
| | - Robin R Ali
- UCL Institute of Ophthalmology, University College London, London, UK.,Gene and Cell Therapy Group, UCL Institute of Ophthalmology, University College London, London, UK.,National Institute for Health and Care Research Biomedical Research Centre at Moorfields Eye Hospital National Health Service Foundation Trust, London, UK
| | - Maria S Balda
- UCL Institute of Ophthalmology, University College London, London, UK
| | - Karl Matter
- UCL Institute of Ophthalmology, University College London, London, UK
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16
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Chang X, Yin Z, Zhang W, Shi J, Pu C, Shi Q, Wang J, Zhang J, Yan L, Yang W, Guo J. Data-independent acquisition-based quantitative proteomic analysis of m.3243A>G MELAS reveals novel potential pathogenesis and therapeutic targets. Medicine (Baltimore) 2022; 101:e30938. [PMID: 36254078 PMCID: PMC9575705 DOI: 10.1097/md.0000000000030938] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
The pathogenesis of mitochondrial myopathy, encephalopathy, lactic acidosis and stroke like episodes (MELAS) syndrome has not been fully elucidated. The m.3243A > G mutation which is responsible for 80% MELAS patients affects proteins with undetermined functions. Therefore, we performed quantitative proteomic analysis on skeletal muscle specimens from MELAS patients. We recruited 10 patients with definitive MELAS and 10 age- and gender- matched controls. Proteomic analysis based on nanospray liquid chromatography-mass spectrometry (LC-MS) was performed using data-independent acquisition (DIA) method and differentially expressed proteins were revealed by bioinformatics analysis. We identified 128 differential proteins between MELAS and controls, including 68 down-regulated proteins and 60 up-regulated proteins. The differential proteins involved in oxidative stress were identified, including heat shock protein beta-1 (HSPB1), alpha-crystallin B chain (CRYAB), heme oxygenase 1 (HMOX1), glucose-6-phosphate dehydrogenase (G6PD) and selenoprotein P. Gene ontology and kyoto encyclopedia of genes and genomes pathway analysis showed significant enrichment in phagosome, ribosome and peroxisome proliferator-activated receptors (PPAR) signaling pathway. The imbalance between oxidative stress and antioxidant defense, the activation of autophagosomes, and the abnormal metabolism of mitochondrial ribosome proteins (MRPs) might play an important role in m.3243A > G MELAS. The combination of proteomic and bioinformatics analysis could contribute potential molecular networks to the pathogenesis of MELAS in a comprehensive manner.
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Affiliation(s)
- Xueli Chang
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Zhaoxu Yin
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Wei Zhang
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Jiaying Shi
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Chuanqiang Pu
- Department of Neurology, Chinese People’s Liberation Army General Hospital, Beijing, China
| | - Qiang Shi
- Department of Neurology, Chinese People’s Liberation Army General Hospital, Beijing, China
| | - Juan Wang
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Jing Zhang
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Li Yan
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
| | - Wenqu Yang
- Department of Anesthesiology, Shanxi Bethune Hospital, Shanxi Academy of Medical Science, Taiyuan, Shanxi, China
| | - Junhong Guo
- Department of Neurology, First Hospital of Shanxi Medical University, Taiyuan, Shanxi, China
- *Correspondence: Junhong Guo, Department of Neurology, First Hospital, Shanxi Medical University, No. 85, Jiefang South Road, Taiyuan, 030001, Shanxi, China (e-mail: )
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17
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Moran AL, Fehilly JD, Floss Jones D, Collery R, Kennedy BN. Regulation of the rhythmic diversity of daily photoreceptor outer segment phagocytosis in vivo. FASEB J 2022; 36:e22556. [PMID: 36165194 PMCID: PMC9828801 DOI: 10.1096/fj.202200990rr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Revised: 08/30/2022] [Accepted: 09/06/2022] [Indexed: 01/12/2023]
Abstract
Outer segment phagocytosis (OSP) is a highly-regulated, biological process wherein photoreceptor outer segment (OS) tips are cyclically phagocytosed by the adjacent retinal pigment epithelium (RPE) cells. Often an overlooked retinal process, rhythmic OSP ensures the maintenance of healthy photoreceptors and vision. Daily, the photoreceptors renew OS at their base and the most distal, and likely oldest, OS tips, are phagocytosed by the RPE, preventing the accumulation of photo-oxidative compounds by breaking down phagocytosed OS tips and recycling useful components to the photoreceptors. Light changes often coincide with an escalation of OSP and within hours the phagosomes formed in each RPE cell are resolved. In the last two decades, individual molecular regulators were elucidated. Some of the molecular machinery used by RPE cells for OSP is highly similar to mechanisms used by other phagocytic cells for the clearance of apoptotic cells. Consequently, in the RPE, many molecular regulators of retinal phagocytosis have been elucidated. However, there is still a knowledge gap regarding the key regulators of physiological OSP in vivo between endogenous photoreceptors and the RPE. Understanding the regulation of OSP is of significant clinical interest as age-related macular degeneration (AMD) and inherited retinal diseases (IRD) are linked with altered OSP. Here, we review the in vivo timing of OSP peaks in selected species and focus on the reported in vivo environmental and molecular regulators of OSP.
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Affiliation(s)
- Ailis L. Moran
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
| | - John D. Fehilly
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
| | - Daniel Floss Jones
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
| | - Ross Collery
- Department of Cell Biology, Neurobiology and AnatomyMedical College of WisconsinMilwaukeeWisconsinUSA,Department of Ophthalmology and Visual SciencesMedical College of Wisconsin Eye InstituteMilwaukeeWisconsinUSA
| | - Breandán N. Kennedy
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland,UCD Conway InstituteUniversity College DublinDublinIreland
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18
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Yu Y, Zhang Z, Walpole GFW, Yu Y. Kinetics of phagosome maturation is coupled to their intracellular motility. Commun Biol 2022; 5:1014. [PMID: 36163370 PMCID: PMC9512794 DOI: 10.1038/s42003-022-03988-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Accepted: 09/12/2022] [Indexed: 11/09/2022] Open
Abstract
Immune cells degrade internalized pathogens in phagosomes through sequential biochemical changes. The degradation must be fast enough for effective infection control. The presumption is that each phagosome degrades cargos autonomously with a distinct but stochastic kinetic rate. However, here we show that the degradation kinetics of individual phagosomes is not stochastic but coupled to their intracellular motility. By engineering RotSensors that are optically anisotropic, magnetic responsive, and fluorogenic in response to degradation activities in phagosomes, we monitored cargo degradation kinetics in single phagosomes simultaneously with their translational and rotational dynamics. We show that phagosomes that move faster centripetally are more likely to encounter and fuse with lysosomes, thereby acidifying faster and degrading cargos more efficiently. The degradation rates increase nearly linearly with the translational and rotational velocities of phagosomes. Our results indicate that the centripetal motion of phagosomes functions as a clock for controlling the progression of cargo degradation.
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Affiliation(s)
- Yanqi Yu
- Department of Chemistry, Indiana University, Bloomington, IN, 47405-7102, USA
| | - Zihan Zhang
- Department of Chemistry, Indiana University, Bloomington, IN, 47405-7102, USA
| | - Glenn F W Walpole
- Program in Cell Biology, The Hospital for Sick Children, Toronto, Ontario, Canada
- Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Yan Yu
- Department of Chemistry, Indiana University, Bloomington, IN, 47405-7102, USA.
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19
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Zhang T, Huang X, Liu S, Bai X, Zhu X, Clegg DO, Jiang M, Sun X. Determining the optimal stage for cryopreservation of human embryonic stem cell-derived retinal pigment epithelial cells. Stem Cell Res Ther 2022; 13:454. [PMID: 36064625 PMCID: PMC9446586 DOI: 10.1186/s13287-022-03141-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Accepted: 08/15/2022] [Indexed: 11/10/2022] Open
Abstract
Background Human embryonic stem cell-derived retinal pigment epithelial cells (hESC-derived RPE) are a promising source for cell-replacement therapy to treat retinal degenerative diseases, but research on RPE cryopreservation is limited. This study aimed to determine the best phase for RPE cryopreservation to preserve the post-thaw function and uncover the mechanism underlying RPE freezing tolerance. Methods hESC-derived RPE cells were cryopreserved at various time points after seeding. After thawing, the survival and attachment rates, RPE marker gene expression, apical-basal polarity, PEDF secretion, transepithelial resistance, and phagocytotic ability of post-thaw RPE cells were evaluated. RNA sequencing was performed on RPE cells at three-time points, differentially expressed genes were identified, and gene ontology, Kyoto encyclopedia of genes and genomes, and protein–protein interaction analyses were used to investigate the key pathways or molecules associated with RPE cell freezing tolerance. Results RPE frozen at passage 2 day 5 (P2D5) had the highest cell viability and attachment after thawing. They also retained properly localized expression of RPE marker genes and biological functions such as PEDF secretion, high transepithelial resistance, and phagocytic ability. The RNA-sequencing analysis revealed that RPE cells at P2D5 expressed high levels of cell cycle/DNA replication and ECM binding associated genes, as well as THBS1, which may serve as a possible hub gene involved in freezing tolerance. We also confirmed that the RPE cells at P2D5 were in the exponential stage with active DNA replication. Conclusions We propose that freezing hESC-derived RPE cells during their exponential phase results in the best post-thawing outcome in terms of cell viability and preservation of RPE cell properties and functions. The high expression levels of the cell cycle and ECM binding associated genes, particularly THBS1, may contribute to better cell recovery at this stage. Supplementary Information The online version contains supplementary material available at 10.1186/s13287-022-03141-2.
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Affiliation(s)
- Ting Zhang
- National Clinical Research Center for Ophthalmic Diseases, Shanghai, China.,Department of Ophthalmology, Shanghai General Hospital (Shanghai First People's Hospital), Shanghai Jiao Tong University, School of Medicine, 100 Haining Road, Shanghai, 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai, China
| | - Xianyu Huang
- National Clinical Research Center for Ophthalmic Diseases, Shanghai, China.,Department of Ophthalmology, Shanghai General Hospital (Shanghai First People's Hospital), Shanghai Jiao Tong University, School of Medicine, 100 Haining Road, Shanghai, 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai, China
| | - Sujun Liu
- National Clinical Research Center for Ophthalmic Diseases, Shanghai, China.,Department of Ophthalmology, Shanghai General Hospital (Shanghai First People's Hospital), Shanghai Jiao Tong University, School of Medicine, 100 Haining Road, Shanghai, 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai, China
| | - Xinyue Bai
- National Clinical Research Center for Ophthalmic Diseases, Shanghai, China.,Department of Ophthalmology, Shanghai General Hospital (Shanghai First People's Hospital), Shanghai Jiao Tong University, School of Medicine, 100 Haining Road, Shanghai, 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai, China
| | - Xinyue Zhu
- National Clinical Research Center for Ophthalmic Diseases, Shanghai, China.,Department of Ophthalmology, Shanghai General Hospital (Shanghai First People's Hospital), Shanghai Jiao Tong University, School of Medicine, 100 Haining Road, Shanghai, 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai, China
| | - Dennis O Clegg
- Department of Molecular, Cellular and Developmental Biology, University of California, Santa Barbara, USA
| | - Mei Jiang
- National Clinical Research Center for Ophthalmic Diseases, Shanghai, China. .,Department of Ophthalmology, Shanghai General Hospital (Shanghai First People's Hospital), Shanghai Jiao Tong University, School of Medicine, 100 Haining Road, Shanghai, 200080, China. .,National Clinical Research Center for Eye Diseases, Shanghai, China. .,Shanghai Key Laboratory of Fundus Diseases, Shanghai, China. .,Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai, China.
| | - Xiaodong Sun
- National Clinical Research Center for Ophthalmic Diseases, Shanghai, China.,Department of Ophthalmology, Shanghai General Hospital (Shanghai First People's Hospital), Shanghai Jiao Tong University, School of Medicine, 100 Haining Road, Shanghai, 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai, China.,Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai, China
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20
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Bharti K, den Hollander AI, Lakkaraju A, Sinha D, Williams DS, Finnemann SC, Bowes-Rickman C, Malek G, D'Amore PA. Cell culture models to study retinal pigment epithelium-related pathogenesis in age-related macular degeneration. Exp Eye Res 2022; 222:109170. [PMID: 35835183 PMCID: PMC9444976 DOI: 10.1016/j.exer.2022.109170] [Citation(s) in RCA: 33] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2022] [Revised: 06/23/2022] [Accepted: 06/29/2022] [Indexed: 11/04/2022]
Abstract
Age-related macular degeneration (AMD) is a disease that affects the macula - the central part of the retina. It is a leading cause of irreversible vision loss in the elderly. AMD onset is marked by the presence of lipid- and protein-rich extracellular deposits beneath the retinal pigment epithelium (RPE), a monolayer of polarized, pigmented epithelial cells located between the photoreceptors and the choroidal blood supply. Progression of AMD to the late nonexudative "dry" stage of AMD, also called geographic atrophy, is linked to progressive loss of areas of the RPE, photoreceptors, and underlying choriocapillaris leading to a severe decline in patients' vision. Differential susceptibility of macular RPE in AMD and the lack of an anatomical macula in most lab animal models has promoted the use of in vitro models of the RPE. In addition, the need for high throughput platforms to test potential therapies has driven the creation and characterization of in vitro model systems that recapitulate morphologic and functional abnormalities associated with human AMD. These models range from spontaneously formed cell line ARPE19, immortalized cell lines such as hTERT-RPE1, RPE-J, and D407, to primary human (fetal or adult) or animal (mouse and pig) RPE cells, and embryonic and induced pluripotent stem cell (iPSC) derived RPE. Hallmark RPE phenotypes, such as cobblestone morphology, pigmentation, and polarization, vary significantly betweendifferent models and culture conditions used in different labs, which would directly impact their usability for investigating different aspects of AMD biology. Here the AMD Disease Models task group of the Ryan Initiative for Macular Research (RIMR) provides a summary of several currently used in vitro RPE models, historical aspects of their development, RPE phenotypes that are attainable in these models, their ability to model different aspects of AMD pathophysiology, and pros/cons for their use in the RPE and AMD fields. In addition, due to the burgeoning use of iPSC derived RPE cells, the critical need for developing standards for differentiating and rigorously characterizing RPE cell appearance, morphology, and function are discussed.
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Affiliation(s)
- Kapil Bharti
- Ocular and Stem Cell Translational Research Section, National Eye Institute, NIH, Bethesda, MD, USA.
| | - Anneke I den Hollander
- Department of Ophthalmology, Radboud University Medical Center, Nijmegen, the Netherlands; AbbVie, Genomics Research Center, Cambridge, MA, USA.
| | - Aparna Lakkaraju
- Department of Ophthalmology, School of Medicine, University of California, San Francisco, USA.
| | - Debasish Sinha
- Department of Ophthalmology, Cell Biology and Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, PA, USA; Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
| | - David S Williams
- Stein Eye Institute, Departments of Ophthalmology and Neurobiology, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA, USA.
| | - Silvia C Finnemann
- Center of Cancer, Genetic Diseases, and Gene Regulation, Department of Biological Sciences, Fordham University, Bronx, NY, USA.
| | - Catherine Bowes-Rickman
- Duke Eye Center, Department of Ophthalmology, Duke University School of Medicine, Durham, NC, USA; Department of Cell Biology, Duke University School of Medicine, Durham, NC, USA.
| | - Goldis Malek
- Duke Eye Center, Department of Ophthalmology, Duke University School of Medicine, Durham, NC, USA; Department of Pathology, Duke University School of Medicine, Durham, NC, USA.
| | - Patricia A D'Amore
- Mass Eye and Ear, Departments of Ophthalmology and Pathology, Harvard Medical School, Boston, MA, USA.
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21
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Moran AL, Carter SP, Kaylor JJ, Jiang Z, Broekman S, Dillon ET, Gómez Sánchez A, Minhas SK, van Wijk E, Radu RA, Travis GH, Carey M, Blacque OE, Kennedy BN. Dawn and dusk peaks of outer segment phagocytosis, and visual cycle function require Rab28. FASEB J 2022; 36:e22309. [PMID: 35471581 PMCID: PMC9322422 DOI: 10.1096/fj.202101897r] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Revised: 03/14/2022] [Accepted: 03/29/2022] [Indexed: 12/12/2022]
Abstract
RAB28 is a farnesylated, ciliary G-protein. Patient variants in RAB28 are causative of autosomal recessive cone-rod dystrophy (CRD), an inherited human blindness. In rodent and zebrafish models, the absence of Rab28 results in diminished dawn, photoreceptor, outer segment phagocytosis (OSP). Here, we demonstrate that Rab28 is also required for dusk peaks of OSP, but not for basal OSP levels. This study further elucidated the molecular mechanisms by which Rab28 controls OSP and inherited blindness. Proteomic profiling identified factors whose expression in the eye or whose expression at dawn and dusk peaks of OSP is dysregulated by loss of Rab28. Notably, transgenic overexpression of Rab28, solely in zebrafish cones, rescues the OSP defect in rab28 KO fish, suggesting rab28 gene replacement in cone photoreceptors is sufficient to regulate Rab28-OSP. Rab28 loss also perturbs function of the visual cycle as retinoid levels of 11-cRAL, 11cRP, and atRP are significantly reduced in larval and adult rab28 KO retinae (p < .05). These data give further understanding on the molecular mechanisms of RAB28-associated CRD, highlighting roles of Rab28 in both peaks of OSP, in vitamin A metabolism and in retinoid recycling.
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Affiliation(s)
- Ailís L. Moran
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway InstituteUniversity College DublinDublinIreland
| | - Stephen P. Carter
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway InstituteUniversity College DublinDublinIreland
| | - Joanna J. Kaylor
- Department of OphthalmologyDavid Geffen School of MedicineUCLA Stein Eye InstituteUniversity of California Los AngelesLos AngelesCaliforniaUSA
| | - Zhichun Jiang
- Department of OphthalmologyDavid Geffen School of MedicineUCLA Stein Eye InstituteUniversity of California Los AngelesLos AngelesCaliforniaUSA
| | - Sanne Broekman
- Department of OtorhinolaryngologyRadboud University Medical CenterNijmegenThe Netherlands
- Donders Institute for Brain, Cognition, and BehaviorNijmegenThe Netherlands
| | | | - Alicia Gómez Sánchez
- UCD Conway InstituteUniversity College DublinDublinIreland
- Ocupharm Diagnostic Group ResearchFaculty of Optic and OptometryUniversidad Complutense de MadridMadridSpain
| | - Sajal K. Minhas
- UCD School of Mathematics & StatisticsUniversity College DublinDublinIreland
| | - Erwin van Wijk
- Department of OtorhinolaryngologyRadboud University Medical CenterNijmegenThe Netherlands
- Donders Institute for Brain, Cognition, and BehaviorNijmegenThe Netherlands
| | - Roxana A. Radu
- Department of OphthalmologyDavid Geffen School of MedicineUCLA Stein Eye InstituteUniversity of California Los AngelesLos AngelesCaliforniaUSA
| | - Gabriel H. Travis
- Department of OphthalmologyDavid Geffen School of MedicineUCLA Stein Eye InstituteUniversity of California Los AngelesLos AngelesCaliforniaUSA
- Department of Biological ChemistryUniversity of CaliforniaLos Angeles School of MedicineLos AngelesCaliforniaUSA
| | - Michelle Carey
- UCD School of Mathematics & StatisticsUniversity College DublinDublinIreland
| | - Oliver E. Blacque
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway InstituteUniversity College DublinDublinIreland
| | - Breandán N. Kennedy
- UCD School of Biomolecular and Biomedical ScienceUniversity College DublinDublinIreland
- UCD Conway InstituteUniversity College DublinDublinIreland
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22
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Vargas JA, Finnemann SC. Probing Photoreceptor Outer Segment Phagocytosis by the RPE In Vivo: Models and Methodologies. Int J Mol Sci 2022; 23:ijms23073661. [PMID: 35409021 PMCID: PMC8998817 DOI: 10.3390/ijms23073661] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Revised: 03/23/2022] [Accepted: 03/24/2022] [Indexed: 01/27/2023] Open
Abstract
In the vertebrate retina, the light-sensitive photoreceptor rods and cones constantly undergo renewal by generating new portions of the outer segment and shedding their distal, spent tips. The neighboring RPE provides the critical function of engulfing the spent material by phagocytosis. RPE phagocytosis of shed rod outer segment fragments is a circadian process that occurs in a burst of activity shortly after daily light onset with low activity at other times, a rhythm that has been reported for many species and over 50 years. In this review, we compare studies on the rhythm and quantity of RPE phagocytosis using different in vivo model systems and assessment methods. We discuss how measurement methodology impacts the observation and analysis of RPE phagocytosis. Published studies on RPE phagocytosis investigating mice further suggest that differences in genetic background and housing conditions may affect results. Altogether, a comparison between RPE phagocytosis studies performed using differing methodology and strains of the same species is not as straightforward as previously thought.
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23
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Hazim RA, Williams DS. Microtubule Motor Transport of Organelles in a Specialized Epithelium: The RPE. Front Cell Dev Biol 2022; 10:852468. [PMID: 35309899 PMCID: PMC8930850 DOI: 10.3389/fcell.2022.852468] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 02/01/2022] [Indexed: 11/13/2022] Open
Abstract
The retinal pigment epithelium (RPE) is a uniquely polarized epithelium that lies adjacent to the photoreceptor cells in the retina, and is essential for photoreceptor function and viability. Two major motile organelles present in the RPE are the melanosomes, which are important for absorbing stray light, and phagosomes that result from the phagocytosis of the distal tips of the photoreceptor cilium, known as the photoreceptor outer segment (POS). These organelles are transported along microtubules, aligned with the apical-basal axis of the RPE. Although they undergo a directional migration, the organelles exhibit bidirectional movements, indicating both kinesin and dynein motor function in their transport. Apical melanosome localization requires dynein; it has been suggested that kinesin contribution might be complex with the involvement of more than one type of kinesin. POS phagosomes undergo bidirectional movements; roles of both plus- and minus-end directed motors appear to be important in the efficient degradation of phagosomes. This function is directly related to retinal health, with defects in motor proteins, or in the association of the phagosomes with the motors, resulting in retinal degenerative pathologies.
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Affiliation(s)
- Roni A. Hazim
- Department of Ophthalmology and Stein Eye Institute, Los Angeles, CA, United States
| | - David S. Williams
- Department of Ophthalmology and Stein Eye Institute, Los Angeles, CA, United States
- Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, United States
- Molecular Biology Institute, University of California, Los Angeles, Los Angeles, CA, United States
- Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, United States
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24
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Ji X, Zhao L, Umapathy A, Fitzmaurice B, Wang J, Williams DS, Chang B, Naggert JK, Nishina PM. Deficiency in Lyst function leads to accumulation of secreted proteases and reduced retinal adhesion. PLoS One 2022; 17:e0254469. [PMID: 35239671 PMCID: PMC8893605 DOI: 10.1371/journal.pone.0254469] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 02/18/2022] [Indexed: 11/19/2022] Open
Abstract
Chediak-Higashi syndrome, caused by mutations in the Lysosome Trafficking Regulator (Lyst) gene, is a recessive hypopigmentation disorder characterized by albinism, neuropathies, neurodegeneration, and defective immune responses, with enlargement of lysosomes and lysosome-related organelles. Although recent studies have suggested that Lyst mutations impair the regulation of sizes of lysosome and lysosome-related organelle, the underlying pathogenic mechanism of Chediak-Higashi syndrome is still unclear. Here we show striking evidence that deficiency in LYST protein function leads to accumulation of photoreceptor outer segment phagosomes in retinal pigment epithelial cells, and reduces adhesion between photoreceptor outer segment and retinal pigment epithelial cells in a mouse model of Chediak-Higashi syndrome. In addition, we observe elevated levels of cathepsins, matrix metallopeptidase (MMP) 3 and oxidative stress markers in the retinal pigment epithelium of Lyst mutants. Previous reports showed that impaired degradation of photoreceptor outer segment phagosomes causes elevated oxidative stress, which could consequently lead to increases of cysteine cathepsins and MMPs in the extracellular matrix. Taken together, we conclude that the loss of LYST function causes accumulation of phagosomes in the retinal pigment epithelium and elevation of several extracellular matrix-remodeling proteases through oxidative stress, which may, in turn, reduce retinal adhesion. Our work reveals previously unreported pathogenic events in the retinal pigment epithelium caused by Lyst deficiency. The same pathogenic events may be conserved in other professional phagocytic cells, such as macrophages in the immune system, contributing to overall Chediak-Higashi syndrome pathology.
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Affiliation(s)
- Xiaojie Ji
- The Jackson Laboratory, Bar Harbor, ME, United States of America
- Graduate School of Biomedical Science and Engineering, University of Maine, Orono, ME, United States of America
| | - Lihong Zhao
- The Jackson Laboratory, Bar Harbor, ME, United States of America
| | - Ankita Umapathy
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles, CA, United States of America
| | | | - Jieping Wang
- The Jackson Laboratory, Bar Harbor, ME, United States of America
| | - David S. Williams
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles, CA, United States of America
- Department of Neurobiology, David Geffen School of Medicine, UCLA, Los Angeles, CA, United States of America
- Molecular Biology Institute, UCLA, Los Angeles, CA, United States of America
- Brain Research Institute, UCLA, Los Angeles, CA, United States of America
| | - Bo Chang
- The Jackson Laboratory, Bar Harbor, ME, United States of America
| | | | - Patsy M. Nishina
- The Jackson Laboratory, Bar Harbor, ME, United States of America
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25
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Liu J, Bassal M, Schlichting S, Braren I, Di Spiezio A, Saftig P, Bartsch U. Intravitreal gene therapy restores the autophagy-lysosomal pathway and attenuates retinal degeneration in cathepsin D-deficient mice. Neurobiol Dis 2022; 164:105628. [PMID: 35033660 DOI: 10.1016/j.nbd.2022.105628] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 01/07/2022] [Accepted: 01/10/2022] [Indexed: 11/16/2022] Open
Abstract
Loss of vision due to progressive retinal degeneration is a hallmark of neuronal ceroid lipofuscinoses (NCL), a group of fatal neurodegenerative lysosomal storage diseases. Enzyme substitution therapies represent promising treatment options for NCLs caused by dysfunctions of soluble lysosomal enzymes. Here, we compared the efficacy of a cell-based enzyme substitution strategy and a gene therapy approach to attenuate the retinal pathology in cathepsin D- (CTSD) deficient mice, an animal model of CLN10 disease. Levels of enzymatically active CTSD in mutant retinas were significantly higher after an adeno-associated virus vector-mediated CTSD transfer to retinal glial cells and retinal pigment epithelial cells than after intravitreal transplantations of a CTSD overexpressing clonal neural stem cell line. In line with this finding, the gene therapy treatment restored the disrupted autophagy-lysosomal pathway more effectively than the cell-based approach, as indicated by a complete clearance of storage, significant attenuation of lysosomal hypertrophy, and normalized levels of the autophagy marker sequestosome 1/p62 and microtubule-associated protein 1 light chain 3-II. While the cell-based treatment did not prevent the rapidly progressing loss of various retinal cell types, the gene therapy approach markedly attenuated retinal degeneration as demonstrated by a pronounced rescue of photoreceptor cells and rod bipolar cells.
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Affiliation(s)
- Junling Liu
- Department of Ophthalmology, Experimental Ophthalmology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Mahmoud Bassal
- Department of Ophthalmology, Experimental Ophthalmology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Stefanie Schlichting
- Department of Ophthalmology, Experimental Ophthalmology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Ingke Braren
- Vector Facility, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | | | - Paul Saftig
- Institute of Biochemistry, Christian-Albrechts-University Kiel, 24118 Kiel, Germany
| | - Udo Bartsch
- Department of Ophthalmology, Experimental Ophthalmology, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
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26
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Haynes EM, Burnett KH, He J, Jean-Pierre MW, Jarzyna M, Eliceiri KW, Huisken J, Halloran MC. KLC4 shapes axon arbors during development and mediates adult behavior. eLife 2022; 11:74270. [PMID: 36222498 PMCID: PMC9596160 DOI: 10.7554/elife.74270] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Accepted: 10/11/2022] [Indexed: 11/13/2022] Open
Abstract
Development of elaborate and polarized neuronal morphology requires precisely regulated transport of cellular cargos by motor proteins such as kinesin-1. Kinesin-1 has numerous cellular cargos which must be delivered to unique neuronal compartments. The process by which this motor selectively transports and delivers cargo to regulate neuronal morphogenesis is poorly understood, although the cargo-binding kinesin light chain (KLC) subunits contribute to specificity. Our work implicates one such subunit, KLC4, as an essential regulator of axon branching and arborization pattern of sensory neurons during development. Using live imaging approaches in klc4 mutant zebrafish, we show that KLC4 is required for stabilization of nascent axon branches, proper microtubule (MT) dynamics, and endosomal transport. Furthermore, KLC4 is required for proper tiling of peripheral axon arbors: in klc4 mutants, peripheral axons showed abnormal fasciculation, a behavior characteristic of central axons. This result suggests that KLC4 patterns axonal compartments and helps establish molecular differences between central and peripheral axons. Finally, we find that klc4 mutant larva are hypersensitive to touch and adults show anxiety-like behavior in a novel tank test, implicating klc4 as a new gene involved in stress response circuits.
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Affiliation(s)
- Elizabeth M Haynes
- Department of Integrative Biology, University of Wisconsin-MadisonMadisonUnited States,Center for Quantitative Cell Imaging, University of Wisconsin-MadisonMadisonUnited States,Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States,Morgridge Institute for ResearchMadisonUnited States
| | - Korri H Burnett
- Department of Integrative Biology, University of Wisconsin-MadisonMadisonUnited States,Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
| | - Jiaye He
- Morgridge Institute for ResearchMadisonUnited States,National Innovation Center for Advanced Medical DevicesShenzenChina
| | - Marcel W Jean-Pierre
- Department of Integrative Biology, University of Wisconsin-MadisonMadisonUnited States,Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
| | - Martin Jarzyna
- Department of Integrative Biology, University of Wisconsin-MadisonMadisonUnited States,Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
| | - Kevin W Eliceiri
- Center for Quantitative Cell Imaging, University of Wisconsin-MadisonMadisonUnited States,Morgridge Institute for ResearchMadisonUnited States
| | - Jan Huisken
- Department of Integrative Biology, University of Wisconsin-MadisonMadisonUnited States,Morgridge Institute for ResearchMadisonUnited States,Department of Biology and Psychology, Georg-August-UniversityGöttingenGermany
| | - Mary C Halloran
- Department of Integrative Biology, University of Wisconsin-MadisonMadisonUnited States,Department of Neuroscience, University of Wisconsin-MadisonMadisonUnited States
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27
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Zhu XY, Chen YH, Zhang T, Liu SJ, Bai XY, Huang XY, Jiang M, Sun XD. Improvement of human embryonic stem cell-derived retinal pigment epithelium cell adhesion, maturation, and function through coating with truncated recombinant human vitronectin. Int J Ophthalmol 2021; 14:1160-1167. [PMID: 34414078 DOI: 10.18240/ijo.2021.08.04] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2021] [Accepted: 04/21/2021] [Indexed: 11/23/2022] Open
Abstract
AIM To explore an xeno-free and defined coating substrate suitable for the culture of H9 human embryonic stem cell-derived retinal pigment epithelial (hES-RPE) cells in vitro, and compare the behaviors and functions of hES-RPE cells on two culture substrates, laminin521 (LN-521) and truncated recombinant human vitronectin (VTN-N). METHODS hES-RPE cells were used in the experiment. The abilities of LN-521 and VTN-N at different concentrations to adhere to hES-RPE cells were compared with a high-content imaging system. Quantitative real-time polymerase chain reaction was used to evaluate RPE-specific gene expression levels midway (day 10) and at the end (day 20) of the time course. Cell polarity was observed by immunofluorescent staining for apical and basal markers of the RPE. The phagocytic ability of hES-RPE cells was identified by flow cytometry and immunofluorescence. RESULTS The cell adhesion assay showed that the ability of LN-521 to adhere to hES-RPE cells was dose-dependent. With increasing coating concentration, an increasing number of cells attached to the surface of LN-521-coated wells. In contrast, VTN-N presented a strong adhesive ability even at a low concentration. The optimal concentration of LN-521 and VTN-N required to coat and adhesion to hES-RPE cells were 2 and 0.25 µg/cm2, respectively. Furthermore, both LN-521 and VTN-N could facilitate adoption of the desired cobblestone cellular morphology with tight junction and showed polarity by the hES-RPE cells. However, hES-RPE cells cultivated in VTN-N had a greater phagocytic ability, and it took less time for these hES-RPE cells to mature. CONCLUSION VTN-N is a more suitable coating substrate for cultivating hES-RPE cells.
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Affiliation(s)
- Xin-Yue Zhu
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai 200080, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai 200080, China.,Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai 200080, China
| | - Yu-Hong Chen
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai 200080, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai 200080, China.,Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai 200080, China
| | - Ting Zhang
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai 200080, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai 200080, China.,Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai 200080, China
| | - Su-Jun Liu
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai 200080, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai 200080, China.,Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai 200080, China
| | - Xin-Yue Bai
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai 200080, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai 200080, China.,Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai 200080, China
| | - Xian-Yu Huang
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai 200080, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai 200080, China.,Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai 200080, China
| | - Mei Jiang
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai 200080, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai 200080, China.,Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai 200080, China
| | - Xiao-Dong Sun
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai 200080, China.,National Clinical Research Center for Eye Diseases, Shanghai 200080, China.,Shanghai Key Laboratory of Fundus Diseases, Shanghai 200080, China.,Shanghai Engineering Center for Visual Science and Photomedicine, Shanghai 200080, China
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28
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Sura AA, Chen L, Messinger JD, Swain TA, McGwin G, Freund KB, Curcio CA. Measuring the Contributions of Basal Laminar Deposit and Bruch's Membrane in Age-Related Macular Degeneration. Invest Ophthalmol Vis Sci 2021; 61:19. [PMID: 33186466 PMCID: PMC7671869 DOI: 10.1167/iovs.61.13.19] [Citation(s) in RCA: 76] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Purpose Basal laminar deposit (BLamD) is a consistent finding in age-related macular degeneration (AMD). We quantified BLamD thickness, appearance, and topography in eyes of aged donors with and without AMD and evaluated its relationship to other components of the retinal pigment epithelium-basal lamina/Bruch's membrane (RPE-BL-BrM) complex. Methods Donor eyes (n = 132) were classified as normal (n = 54), early to intermediate AMD (n = 24), geographic atrophy (GA; n = 13), and neovascular AMD (NV; n = 41). In high-resolution histology, we assessed RPE, BLamD, and BrM thicknesses and phenotypes at 3309 predefined locations in the central (foveal and perifovea) and superior (perifoveal) sections. Pre-mortem optical coherence tomography (OCT) imaging of a 90-year-old woman was compared to postmortem histopathology. Results In non-atrophic areas of AMD eyes, the RPE-BLamD is thick (normal = 13.7 µm, early-intermediate = 16.8 µm, GA = 17.4 µm, NV = 18.7 µm), because the BLamD is thick (normal = 0.3 µm, early-intermediate = 5.5 µm, GA = 4.1 µm, NV = 5.3 µm). RPE layer thickness is similar across these stages. Disease-associated variants of BLamD (thick, late, basal mounds) cluster subfoveally. A thick BLamD is visible on OCT as a hyporeflective split in the RPE-BL-BrM complex. BrM is thin (3.5 µm) in NV (normal = 4.2 µm, early to intermediate = 4.4 µm, and GA = 4.2 µm). Conclusions The RPE-BL-BrM complex is thick in AMD, driven by the accumulation and expansion of BLamD rather than expansion of either three-layer BrM, RPE-BL, or RPE. BLamD is clinically appreciable by OCT in some patients as a non-neovascular "split RPE-BL-BrM complex" or "double-layer sign." BLamD may contribute toward the formation and progression of high-risk drusen yet also exhibit protective properties.
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Affiliation(s)
- Amol A Sura
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, United States
| | - Ling Chen
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, United States.,The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Ophthalmology, and Chongqing Eye Institute, Chongqing, China
| | - Jeffrey D Messinger
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, United States
| | - Thomas A Swain
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, United States.,Department of Epidemiology, School of Public Health, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - Gerald McGwin
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, United States.,Department of Epidemiology, School of Public Health, University of Alabama at Birmingham, Birmingham, Alabama, United States
| | - K Bailey Freund
- Vitreous Retina Macula Consultants of New York, New York, New York, United States.,Department of Ophthalmology, Faculty of Medicine, University of Tsukuba, Ibaraki, Japan.,LuEsther T. Mertz Retinal Research Center, Manhattan Eye Ear and Throat Hospital, New York, New York, United States.,Department of Ophthalmology, NYU Langone School of Medicine, New York, New York, United States.,Columbia University College of Physicians and Surgeons, Harkness Eye Institute, New York, New York, United States
| | - Christine A Curcio
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham School of Medicine, Birmingham, Alabama, United States
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29
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Transcriptomic analysis of early stages of intestinal regeneration in Holothuria glaberrima. Sci Rep 2021; 11:346. [PMID: 33431961 PMCID: PMC7801731 DOI: 10.1038/s41598-020-79436-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Accepted: 12/04/2020] [Indexed: 01/29/2023] Open
Abstract
Echinoderms comprise a group of animals with impressive regenerative capabilities. They can replace complex internal organs following injury or autotomy. In holothurians or sea cucumbers, cellular processes of intestinal regeneration have been extensively studied. The molecular machinery behind this faculty, however, remains to be understood. Here we assembled and annotated a de novo transcriptome using RNA-seq data consisting of regenerating and non-regenerating intestinal tissues from the sea cucumber Holothuria glaberrima. Comparisons of differential expression were made using the mesentery as a reference against 24 h and 3 days regenerating intestine, revealing a large number of differentially expressed transcripts. Gene ontology and pathway enrichment analysis showed evidence of increasing transcriptional activity. Further analysis of transcripts associated with transcription factors revealed diverse expression patterns with mechanisms involving developmental and cancer-related activity that could be related to the regenerative process. Our study demonstrates the broad and diversified gene expression profile during the early stages of the process using the mesentery as the focal point of intestinal regeneration. It also establishes the genes that are the most important candidates in the cellular processes that underlie regenerative responses.
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30
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Subramaniam MD, Iyer M, Nair AP, Venkatesan D, Mathavan S, Eruppakotte N, Kizhakkillach S, Chandran MK, Roy A, Gopalakrishnan AV, Vellingiri B. Oxidative stress and mitochondrial transfer: A new dimension towards ocular diseases. Genes Dis 2020; 9:610-637. [PMID: 35782976 PMCID: PMC9243399 DOI: 10.1016/j.gendis.2020.11.020] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2020] [Revised: 09/18/2020] [Accepted: 11/27/2020] [Indexed: 12/12/2022] Open
Abstract
Ocular cells like, retinal pigment epithelium (RPE) is a highly specialized pigmented monolayer of post-mitotic cells, which is located in the posterior segment of the eye between neuro sensory retina and vascular choroid. It functions as a selective barrier and nourishes retinal visual cells. As a result of high-level oxygen consumption of retinal cells, RPE cells are vulnerable to chronic oxidative stress and an increased level of reactive oxygen species (ROS) generated from mitochondria. These oxidative stress and ROS generation in retinal cells lead to RPE degeneration. Various sources including mtDNA damage could be an important factor of oxidative stress in RPE. Gene therapy and mitochondrial transfer studies are emerging fields in ocular disease research. For retinal degenerative diseases stem cell-based transplantation methods are developed from basic research to preclinical and clinical trials. Translational research contributions of gene and cell therapy would be a new strategy to prevent, treat and cure various ocular diseases. This review focuses on the effect of oxidative stress in ocular cell degeneration and recent translational researches on retinal degenerative diseases to cure blindness.
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Affiliation(s)
- Mohana Devi Subramaniam
- SN ONGC Department of Genetics and Molecular Biology, Vision Research Foundation, Chennai 600006, Tamil Nadu, India
- Corresponding author.
| | - Mahalaxmi Iyer
- SN ONGC Department of Genetics and Molecular Biology, Vision Research Foundation, Chennai 600006, Tamil Nadu, India
- Department of Zoology, Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore 641 043, Tamil Nadu, India
| | - Aswathy P. Nair
- SN ONGC Department of Genetics and Molecular Biology, Vision Research Foundation, Chennai 600006, Tamil Nadu, India
| | - Dhivya Venkatesan
- Human Molecular Cytogenetics and Stem Cell Laboratory, Department of Human Genetics and Molecular Biology, Bharathiar University, Coimbatore 641046, Tamil Nadu, India
| | - Sinnakaruppan Mathavan
- SN ONGC Department of Genetics and Molecular Biology, Vision Research Foundation, Chennai 600006, Tamil Nadu, India
| | - Nimmisha Eruppakotte
- Human Molecular Cytogenetics and Stem Cell Laboratory, Department of Human Genetics and Molecular Biology, Bharathiar University, Coimbatore 641046, Tamil Nadu, India
| | - Soumya Kizhakkillach
- Human Molecular Cytogenetics and Stem Cell Laboratory, Department of Human Genetics and Molecular Biology, Bharathiar University, Coimbatore 641046, Tamil Nadu, India
| | - Manoj kumar Chandran
- Human Molecular Cytogenetics and Stem Cell Laboratory, Department of Human Genetics and Molecular Biology, Bharathiar University, Coimbatore 641046, Tamil Nadu, India
| | - Ayan Roy
- Department of Biotechnology, Lovely Professional University, Punjab 144411, India
| | - Abilash Valsala Gopalakrishnan
- Department of Biomedical Sciences, School of Bio Sciences and Technology (SBST), Vellore Institute of Technology (VIT), Vellore 600127, India
| | - Balachandar Vellingiri
- Human Molecular Cytogenetics and Stem Cell Laboratory, Department of Human Genetics and Molecular Biology, Bharathiar University, Coimbatore 641046, Tamil Nadu, India
- Corresponding author. Human Molecular Cytogenetics and Stem Cell, Laboratory, Department of Human Genetics and Molecular Biology, Bharathiar University, Coimbatore 641 046, Tamil Nadu, India.Fax: +91 422 2422387.
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31
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Kwon W, Freeman SA. Phagocytosis by the Retinal Pigment Epithelium: Recognition, Resolution, Recycling. Front Immunol 2020; 11:604205. [PMID: 33281830 PMCID: PMC7691529 DOI: 10.3389/fimmu.2020.604205] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2020] [Accepted: 10/20/2020] [Indexed: 12/13/2022] Open
Abstract
Tissue-resident phagocytes are responsible for the routine binding, engulfment, and resolution of their meals. Such populations of cells express appropriate surface receptors that are tailored to recognize the phagocytic targets of their niche and initiate the actin polymerization that drives internalization. Tissue-resident phagocytes also harbor enzymes and transporters along the endocytic pathway that orchestrate the resolution of ingested macromolecules from the phagolysosome. Solutes fluxed from the endocytic pathway and into the cytosol can then be reutilized by the phagocyte or exported for their use by neighboring cells. Such a fundamental metabolic coupling between resident phagocytes and the tissue in which they reside is well-emphasized in the case of retinal pigment epithelial (RPE) cells; specialized phagocytes that are responsible for the turnover of photoreceptor outer segments (POS). Photoreceptors are prone to photo-oxidative damage and their long-term health depends enormously on the disposal of aged portions of the outer segment. The phagocytosis of the POS by the RPE is the sole means of this turnover and clearance. RPE are themselves mitotically quiescent and therefore must resolve the ingested material to prevent their toxic accumulation in the lysosome that otherwise leads to retinal disorders. Here we describe the sequence of events underlying the healthy turnover of photoreceptors by the RPE with an emphasis on the signaling that ensures the phagocytosis of the distal POS and on the transport of solutes from the phagosome that supersedes its resolution. While other systems may utilize different receptors and transporters, the biophysical and metabolic manifestations of such events are expected to apply to all tissue-resident phagocytes that perform regular phagocytic programs.
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Affiliation(s)
- Whijin Kwon
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, ON, Canada
| | - Spencer A Freeman
- Program in Cell Biology, Peter Gilgan Centre for Research and Learning, Hospital for Sick Children, Toronto, ON, Canada.,Department of Biochemistry, University of Toronto, Toronto, ON, Canada
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32
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Toulis V, García-Monclús S, de la Peña-Ramírez C, Arenas-Galnares R, Abril JF, Todi SV, Khan N, Garanto A, Costa MDC, Marfany G. The Deubiquitinating Enzyme Ataxin-3 Regulates Ciliogenesis and Phagocytosis in the Retina. Cell Rep 2020; 33:108360. [PMID: 33176149 PMCID: PMC8738964 DOI: 10.1016/j.celrep.2020.108360] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 09/04/2020] [Accepted: 10/17/2020] [Indexed: 01/07/2023] Open
Abstract
Expansion of a CAG repeat in ATXN3 causes the dominant polyglutamine disease spinocerebellar ataxia type 3 (SCA3), yet the physiological role of ATXN3 remains unclear. Here, we focus on unveiling the function of Ataxin-3 (ATXN3) in the retina, a neurological organ amenable to morphological and physiological studies. Depletion of Atxn3 in zebrafish and mice causes morphological and functional retinal alterations and, more precisely, photoreceptor cilium and outer segment elongation, cone opsin mislocalization, and cone hyperexcitation. ATXN3 localizes at the basal body and axoneme of the cilium, supporting its role in regulating ciliary length. Abrogation of Atxn3 expression causes decreased levels of the regulatory protein KEAP1 in the retina and delayed phagosome maturation in the retinal pigment epithelium. We propose that ATXN3 regulates two relevant biological processes in the retina, namely, ciliogenesis and phagocytosis, by modulating microtubule polymerization and microtubule-dependent retrograde transport, thus positing ATXN3 as a causative or modifier gene in retinal/macular dystrophies. Toulis et al. show that depletion of Atxn3 causes retinal morphological and electrophysiological alterations, as well as diminished phagocytosis in vivo and in vitro. ATXN3 regulates retinal ciliogenesis and phagocytosis through the KEAP1-SQSTM1-HDAC6-acetylated tubulin pathway by modulating microtubule polymerization and microtubule-dependent retrograde transport.
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Affiliation(s)
- Vasileios Toulis
- Departament de Genètica, Microbiologia i Estadística, Avda. Diagonal 643, Universitat de Barcelona, Barcelona 08028, Spain; CIBERER, ISCIII, Universitat de Barcelona, Barcelona, Spain; Department of Neurology, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Sílvia García-Monclús
- Departament de Genètica, Microbiologia i Estadística, Avda. Diagonal 643, Universitat de Barcelona, Barcelona 08028, Spain
| | - Carlos de la Peña-Ramírez
- Departament de Genètica, Microbiologia i Estadística, Avda. Diagonal 643, Universitat de Barcelona, Barcelona 08028, Spain
| | - Rodrigo Arenas-Galnares
- Departament de Genètica, Microbiologia i Estadística, Avda. Diagonal 643, Universitat de Barcelona, Barcelona 08028, Spain; Institute of Biomedicine (IBUB, IBUB-IRSJD), Universitat de Barcelona, Barcelona, Spain
| | - Josep F Abril
- Departament de Genètica, Microbiologia i Estadística, Avda. Diagonal 643, Universitat de Barcelona, Barcelona 08028, Spain; Institute of Biomedicine (IBUB, IBUB-IRSJD), Universitat de Barcelona, Barcelona, Spain
| | - Sokol V Todi
- Department of Pharmacology, Wayne State University School of Medicine, Detroit, MI, USA; Department of Neurology, Wayne State University School of Medicine, Detroit, MI, USA
| | - Naheed Khan
- Department of Ophthalmology and Visual Sciences, W. K. Kellogg Eye Center, University of Michigan, Ann Arbor, MI, USA
| | - Alejandro Garanto
- Departament de Genètica, Microbiologia i Estadística, Avda. Diagonal 643, Universitat de Barcelona, Barcelona 08028, Spain; Department of Human Genetics, Radboud University Medical Center, 6525 GA Nijmegen, the Netherlands; Donders Institute for Brain, Cognition and Behaviour, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Maria do Carmo Costa
- Department of Neurology, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA.
| | - Gemma Marfany
- Departament de Genètica, Microbiologia i Estadística, Avda. Diagonal 643, Universitat de Barcelona, Barcelona 08028, Spain; CIBERER, ISCIII, Universitat de Barcelona, Barcelona, Spain; Institute of Biomedicine (IBUB, IBUB-IRSJD), Universitat de Barcelona, Barcelona, Spain.
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33
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Miller DT, Kurokawa K. Cellular-Scale Imaging of Transparent Retinal Structures and Processes Using Adaptive Optics Optical Coherence Tomography. Annu Rev Vis Sci 2020; 6:115-148. [PMID: 32609578 PMCID: PMC7864592 DOI: 10.1146/annurev-vision-030320-041255] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
High-resolution retinal imaging is revolutionizing how scientists and clinicians study the retina on the cellular scale. Its exquisite sensitivity enables time-lapse optical biopsies that capture minute changes in the structure and physiological processes of cells in the living eye. This information is increasingly used to detect disease onset and monitor disease progression during early stages, raising the possibility of personalized eye care. Powerful high-resolution imaging tools have been in development for more than two decades; one that has garnered considerable interest in recent years is optical coherence tomography enhanced with adaptive optics. State-of-the-art adaptive optics optical coherence tomography (AO-OCT) makes it possible to visualize even highly transparent cells and measure some of their internal processes at all depths within the retina, permitting reconstruction of a 3D view of the living microscopic retina. In this review, we report current AO-OCT performance and its success in visualizing and quantifying these once-invisible cells in human eyes.
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Affiliation(s)
- Donald T Miller
- School of Optometry, Indiana University, Bloomington, Indiana 47405, USA; ,
| | - Kazuhiro Kurokawa
- School of Optometry, Indiana University, Bloomington, Indiana 47405, USA; ,
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34
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Jiang M, Paniagua AE, Volland S, Wang H, Balaji A, Li DG, Lopes VS, Burgess BL, Williams DS. Microtubule motor transport in the delivery of melanosomes to the actin-rich apical domain of the retinal pigment epithelium. J Cell Sci 2020; 133:jcs242214. [PMID: 32661088 PMCID: PMC7420818 DOI: 10.1242/jcs.242214] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2019] [Accepted: 06/25/2020] [Indexed: 12/20/2022] Open
Abstract
Melanosomes are motile, light-absorbing organelles that are present in pigment cells of the skin and eye. It has been proposed that melanosome localization, in both skin melanocytes and the retinal pigment epithelium (RPE), involves melanosome capture from microtubule motors by an unconventional myosin, which dynamically tethers the melanosomes to actin filaments. Recent studies with melanocytes have questioned this cooperative capture model. Here, we test the model in RPE cells by imaging melanosomes associated with labeled actin filaments and microtubules, and by investigating the roles of different motor proteins. We found that a deficiency in cytoplasmic dynein phenocopies the lack of myosin-7a, in that melanosomes undergo fewer of the slow myosin-7a-dependent movements and are absent from the RPE apical domain. These results indicate that microtubule-based motility is required for the delivery of melanosomes to the actin-rich apical domain and support a capture mechanism that involves both microtubule and actin motors.
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Affiliation(s)
- Mei Jiang
- Departments of Ophthalmology and Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Antonio E Paniagua
- Departments of Ophthalmology and Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Stefanie Volland
- Departments of Ophthalmology and Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Hongxing Wang
- Departments of Ophthalmology and Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Adarsh Balaji
- Departments of Ophthalmology and Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - David G Li
- Departments of Ophthalmology and Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Vanda S Lopes
- Departments of Ophthalmology and Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - Barry L Burgess
- Departments of Ophthalmology and Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
| | - David S Williams
- Departments of Ophthalmology and Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Molecular Biology Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
- Brain Research Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095, USA
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35
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Carter SP, Moran AL, Matallanas D, McManus GJ, Blacque OE, Kennedy BN. Genetic Deletion of Zebrafish Rab28 Causes Defective Outer Segment Shedding, but Not Retinal Degeneration. Front Cell Dev Biol 2020; 8:136. [PMID: 32258030 PMCID: PMC7092623 DOI: 10.3389/fcell.2020.00136] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2019] [Accepted: 02/18/2020] [Indexed: 01/14/2023] Open
Abstract
The photoreceptor outer segment is the canonical example of a modified and highly specialized cilium, with an expanded membrane surface area in the form of disks or lamellae for efficient light detection. Many ciliary proteins are essential for normal photoreceptor function and cilium dysfunction often results in retinal degeneration leading to impaired vision. Herein, we investigate the function and localization of the ciliary G-protein RAB28 in zebrafish cone photoreceptors. CRISPR-Cas9 generated rab28 mutant zebrafish display significantly reduced shed outer segment material/phagosomes in the RPE at 1 month post fertilization (mpf), but otherwise normal visual function up to 21 dpf and retinal structure up to 12 mpf. Cone photoreceptor-specific transgenic reporter lines show Rab28 localizes almost exclusively to outer segments, independently of GTP/GDP nucleotide binding. Co-immunoprecipitation analysis demonstrates tagged Rab28 interacts with components of the phototransduction cascade, including opsins, phosphodiesterase 6C and guanylate cyclase 2D. Our data shed light on RAB28 function in cones and provide a model for RAB28-associated cone-rod dystrophy.
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Affiliation(s)
- Stephen P Carter
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland.,UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Ailís L Moran
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland.,UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - David Matallanas
- Systems Biology Ireland, University College Dublin, Dublin, Ireland
| | - Gavin J McManus
- School of Biochemistry and Immunology, Microscopy Facility, Trinity Biomedical Sciences Institute, Trinity College Dublin, Dublin, Ireland
| | - Oliver E Blacque
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland.,UCD Conway Institute, University College Dublin, Dublin, Ireland
| | - Breandán N Kennedy
- UCD School of Biomolecular and Biomedical Science, University College Dublin, Dublin, Ireland.,UCD Conway Institute, University College Dublin, Dublin, Ireland
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36
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Lakkaraju A, Umapathy A, Tan LX, Daniele L, Philp NJ, Boesze-Battaglia K, Williams DS. The cell biology of the retinal pigment epithelium. Prog Retin Eye Res 2020; 78:100846. [PMID: 32105772 PMCID: PMC8941496 DOI: 10.1016/j.preteyeres.2020.100846] [Citation(s) in RCA: 185] [Impact Index Per Article: 46.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2019] [Revised: 02/19/2020] [Accepted: 02/23/2020] [Indexed: 02/07/2023]
Abstract
The retinal pigment epithelium (RPE), a monolayer of post-mitotic polarized epithelial cells, strategically situated between the photoreceptors and the choroid, is the primary caretaker of photoreceptor health and function. Dysfunction of the RPE underlies many inherited and acquired diseases that cause permanent blindness. Decades of research have yielded valuable insight into the cell biology of the RPE. In recent years, new technologies such as live-cell imaging have resulted in major advancement in our understanding of areas such as the daily phagocytosis and clearance of photoreceptor outer segment tips, autophagy, endolysosome function, and the metabolic interplay between the RPE and photoreceptors. In this review, we aim to integrate these studies with an emphasis on appropriate models and techniques to investigate RPE cell biology and metabolism, and discuss how RPE cell biology informs our understanding of retinal disease.
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Affiliation(s)
- Aparna Lakkaraju
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, USA
| | - Ankita Umapathy
- Department of Ophthalmology and Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA
| | - Li Xuan Tan
- Department of Ophthalmology, University of California, San Francisco, San Francisco, CA, USA
| | - Lauren Daniele
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - Nancy J Philp
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, USA
| | - Kathleen Boesze-Battaglia
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA; Department of Neurobiology, David Geffen School of Medicine at UCLA, Los Angeles, CA, USA.
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37
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Genetic LAMP2 deficiency accelerates the age-associated formation of basal laminar deposits in the retina. Proc Natl Acad Sci U S A 2019; 116:23724-23734. [PMID: 31699817 PMCID: PMC6876195 DOI: 10.1073/pnas.1906643116] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Extracellular tissue debris accumulates with aging and in the most prevalent central-vision-threatening eye disorder, age-related macular degeneration (AMD). In this work, we discovered that lysosome-associated membrane protein-2 (LAMP2), a glycoprotein that plays a critical role in lysosomal biogenesis and maturation of autophagosomes/phagosomes, is preferentially expressed in the outermost, neuroepithelial layer of the retina, the retinal pigment epithelium (RPE), and contributes to the prevention of ultrastructural changes in extracellular basolaminar deposits including lipids and apolipoproteins. LAMP2 thus appears to play an important role in RPE biology, and its apparent decrease with aging and in AMD specimens suggests that its deficiency may accelerate the basolaminar deposit formation and RPE dysfunction seen in these conditions. The early stages of age-related macular degeneration (AMD) are characterized by the accumulation of basal laminar deposits (BLamDs). The mechanism for BLamDs accumulating between the retinal pigment epithelium (RPE) and its basal lamina remains elusive. Here we examined the role in AMD of lysosome-associated membrane protein-2 (LAMP2), a glycoprotein that plays a critical role in lysosomal biogenesis and maturation of autophagosomes/phagosomes. LAMP2 was preferentially expressed by RPE cells, and its expression declined with age. Deletion of the Lamp2 gene in mice resulted in age-dependent autofluorescence abnormalities of the fundus, thickening of Bruch’s membrane, and the formation of BLamDs, resembling histopathological changes occurring in AMD. Moreover, LAMP2-deficient mice developed molecular signatures similar to those found in human AMD—namely, the accumulation of APOE, APOA1, clusterin, and vitronectin—adjacent to BLamDs. In contrast, collagen 4, laminin, and fibronectin, which are extracellular matrix proteins constituting RPE basal lamina and Bruch’s membrane were reduced in Lamp2 knockout (KO) mice. Mechanistically, retarded phagocytic degradation of photoreceptor outer segments compromised lysosomal degradation and increased exocytosis in LAMP2-deficient RPE cells. The accumulation of BLamDs observed in LAMP2-deficient mice was eventually followed by loss of the RPE and photoreceptors. Finally, we observed loss of LAMP2 expression along with ultramicroscopic features of abnormal phagocytosis and exocytosis in eyes from AMD patients but not from control individuals. Taken together, these results indicate an important role for LAMP2 in RPE function in health and disease, suggesting that LAMP2 reduction may contribute to the formation of BLamDs in AMD.
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38
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Daniele LL, Caughey J, Volland S, Sharp RC, Dhingra A, Williams DS, Philp NJ, Boesze-Battaglia K. Peroxisome turnover and diurnal modulation of antioxidant activity in retinal pigment epithelia utilizes microtubule-associated protein 1 light chain 3B (LC3B). Am J Physiol Cell Physiol 2019; 317:C1194-C1204. [PMID: 31577510 DOI: 10.1152/ajpcell.00185.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The retinal pigment epithelium (RPE) supports the outer retina through essential roles in the retinoid cycle, nutrient supply, ion exchange, and waste removal. Each day the RPE removes the oldest ~10% of photoreceptor outer segment (OS) disk membranes through phagocytic uptake, which peaks following light onset. Impaired degradation of phagocytosed OS material by the RPE can lead to toxic accumulation of lipids, oxidative tissue damage, inflammation, and cell death. OSs are rich in very long chain fatty acids, which are preferentially catabolized in peroxisomes. Despite the importance of lipid degradation in RPE function, the regulation of peroxisome number and activity relative to diurnal OS ingestion is relatively unexplored. Using immunohistochemistry, immunoblot analysis, and catalase activity assays, we investigated peroxisome abundance and activity at 6 AM, 7 AM (light onset), 8 AM, and 3 PM, in wild-type (WT) mice and mice lacking microtubule-associated protein 1 light chain 3B (Lc3b), which have impaired phagosome degradation. We found that catalase activity, but not the amount of catalase protein, is 50% higher in the morning compared with 3 PM, in RPE of WT, but not Lc3b-/-, mice. Surprisingly, we found that peroxisome abundance was stable during the day in RPE of WT mice; however, numbers were elevated overall in Lc3b-/- mice, implicating LC3B in autophagic organelle turnover in RPE. Our data suggest that RPE peroxisome function is regulated in coordination with phagocytosis, possibly through direct enzyme regulation, and may serve to prepare RPE peroxisomes for daily surges in ingested lipid-rich OS.
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Affiliation(s)
- Lauren L Daniele
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Jennifer Caughey
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Stefanie Volland
- Department of Ophthalmology, Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, California.,Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Rachel C Sharp
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - Anuradha Dhingra
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
| | - David S Williams
- Department of Ophthalmology, Stein Eye Institute, David Geffen School of Medicine, University of California, Los Angeles, California.,Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles, California
| | - Nancy J Philp
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania
| | - Kathleen Boesze-Battaglia
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania
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39
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Liu Z, Kurokawa K, Hammer DX, Miller DT. In vivo measurement of organelle motility in human retinal pigment epithelial cells. BIOMEDICAL OPTICS EXPRESS 2019; 10:4142-4158. [PMID: 31453000 PMCID: PMC6701538 DOI: 10.1364/boe.10.004142] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/16/2019] [Revised: 06/24/2019] [Accepted: 06/24/2019] [Indexed: 05/18/2023]
Abstract
Retinal pigment epithelial (RPE) cells are well known to play a central role in the progression of numerous retinal diseases. Changes in the structure and function of these cells thus may serve as sensitive biomarkers of disease onset. While in vivo studies have focused on structural changes, functional ones may better capture cell health owing to their more direct connection to cell physiology. In this study, we developed a method based on adaptive optics optical coherence tomography (AO-OCT) and speckle field dynamics for characterizing organelle motility in individual RPE cells. We quantified the dynamics in terms of an exponential decay time constant, the time required for the speckle field to decorrelate. Using seven normal subjects, we found the RPE speckle field to decorrelate in about 5 s. This result has two fundamental implications for future clinical use. First, it establishes a path for generating a normative baseline to which motility of diseased RPE cells can be compared. Second, it predicts an AO-OCT image acquisition time that is 36 times faster than used in our earlier report for individuating RPE cells, thus a major improvement in clinical efficacy.
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Affiliation(s)
- Zhuolin Liu
- Center for Devices and Radiological Health (CDRH), U.S. Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA
| | - Kazuhiro Kurokawa
- School of Optometry, Indiana University, 800 East Atwater Avenue, Bloomington, IN 47405, USA
| | - Daniel X. Hammer
- Center for Devices and Radiological Health (CDRH), U.S. Food and Drug Administration, 10903 New Hampshire Ave, Silver Spring, MD, 20993, USA
| | - Donald T. Miller
- School of Optometry, Indiana University, 800 East Atwater Avenue, Bloomington, IN 47405, USA
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40
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The Cytoskeleton of the Retinal Pigment Epithelium: from Normal Aging to Age-Related Macular Degeneration. Int J Mol Sci 2019; 20:ijms20143578. [PMID: 31336621 PMCID: PMC6678077 DOI: 10.3390/ijms20143578] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2019] [Revised: 07/15/2019] [Accepted: 07/18/2019] [Indexed: 12/15/2022] Open
Abstract
The retinal pigment epithelium (RPE) is a unique epithelium, with major roles which are essential in the visual cycle and homeostasis of the outer retina. The RPE is a monolayer of polygonal and pigmented cells strategically placed between the neuroretina and Bruch membrane, adjacent to the fenestrated capillaries of the choriocapillaris. It shows strong apical (towards photoreceptors) to basal/basolateral (towards Bruch membrane) polarization. Multiple functions are bound to a complex structure of highly organized and polarized intracellular components: the cytoskeleton. A strong connection between the intracellular cytoskeleton and extracellular matrix is indispensable to maintaining the function of the RPE and thus, the photoreceptors. Impairments of these intracellular structures and the regular architecture they maintain often result in a disrupted cytoskeleton, which can be found in many retinal diseases, including age-related macular degeneration (AMD). This review article will give an overview of current knowledge on the molecules and proteins involved in cytoskeleton formation in cells, including RPE and how the cytoskeleton is affected under stress conditions—especially in AMD.
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41
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Rosales MAB, Shu DY, Iacovelli J, Saint-Geniez M. Loss of PGC-1α in RPE induces mesenchymal transition and promotes retinal degeneration. Life Sci Alliance 2019; 2:2/3/e201800212. [PMID: 31101737 PMCID: PMC6526284 DOI: 10.26508/lsa.201800212] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Revised: 05/07/2019] [Accepted: 05/09/2019] [Indexed: 01/07/2023] Open
Abstract
Sustained loss of PGC-1α in RPE cells triggers mitochondrial/autophagic dysfunction and oxidative damage resulting in epithelial dedifferentiation and mesenchymal transition. RPE dysfunction caused by deletion of the PGC-1 coactivators in vivo causes retinal degeneration. The retinal pigment epithelium (RPE) supports visual processing and photoreceptor homeostasis via energetically demanding cellular functions. Here, we describe the consequences of repressing peroxisome proliferator-activated receptor γ coactivator-1 α (PGC-1α), a master regulator of mitochondrial function and biogenesis, on RPE epithelial integrity. The sustained silencing of PGC-1α in differentiating human RPE cells affected mitochondria/autophagy function, redox state, and impaired energy sensor activity ultimately inducing epithelial to mesenchymal transition (EMT). Adult conditional knockout of PGC-1 coactivators in mice resulted in rapid RPE dysfunction and transdifferentiation associated with severe photoreceptor degeneration. RPE anomalies were characteristic of autophagic defect and mesenchymal transition comparable with the ones observed in age-related macular degeneration. These findings demonstrate that PGC-1α is required to maintain the functional and phenotypic status of RPE by supporting the cells’ oxidative metabolism and autophagy-mediated repression of EMT.
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Affiliation(s)
- Mariana Aparecida Brunini Rosales
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Boston, MA.,Department of Ophthalmology, Harvard Medical School, Boston, MA
| | - Daisy Y Shu
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Boston, MA.,Department of Ophthalmology, Harvard Medical School, Boston, MA
| | - Jared Iacovelli
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Boston, MA.,Department of Ophthalmology, Harvard Medical School, Boston, MA
| | - Magali Saint-Geniez
- Schepens Eye Research Institute of Massachusetts Eye and Ear, Boston, MA .,Department of Ophthalmology, Harvard Medical School, Boston, MA
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42
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Toms M, Burgoyne T, Tracey-White D, Richardson R, Dubis AM, Webster AR, Futter C, Moosajee M. Phagosomal and mitochondrial alterations in RPE may contribute to KCNJ13 retinopathy. Sci Rep 2019; 9:3793. [PMID: 30846767 PMCID: PMC6405871 DOI: 10.1038/s41598-019-40507-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2018] [Accepted: 02/18/2019] [Indexed: 12/29/2022] Open
Abstract
Mutations in KCNJ13 are associated with two retinal disorders; Leber congenital amaurosis (LCA) and snowflake vitreoretinal degeneration (SVD). We examined the retina of kcnj13 mutant zebrafish (obelixtd15, c.502T > C p.[Phe168Leu]) to provide new insights into the pathophysiology underlying these conditions. Detailed phenotyping of obelixtd15 fish revealed a late onset retinal degeneration at 12 months. Electron microscopy of the obelixtd15 retinal pigment epithelium (RPE) uncovered reduced phagosome clearance and increased mitochondrial number and size prior any signs of retinal degeneration. Melanosome distribution was also affected in dark-adapted 12-month obelixtd15 fish. At 6 and 12 months, ATP levels were found to be reduced along with increased expression of glial fibrillary acidic protein and heat shock protein 60. Quantitative RT-PCR of polg2, fis1, opa1, sod1/2 and bcl2a from isolated retina showed expression changes consistent with altered mitochondrial activity and retinal stress. We propose that the retinal disease in this model is primarily a failure of phagosome physiology with a secondary mitochondrial dysfunction. Our findings suggest that alterations in the RPE and photoreceptor cellular organelles may contribute to KCNJ13-related retinal degeneration and provide a therapeutic target.
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Affiliation(s)
- Maria Toms
- UCL Institute of Ophthalmology, London, UK
| | | | | | | | - Adam M Dubis
- UCL Institute of Ophthalmology, London, UK.,Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | - Andrew R Webster
- UCL Institute of Ophthalmology, London, UK.,Moorfields Eye Hospital NHS Foundation Trust, London, UK
| | | | - Mariya Moosajee
- UCL Institute of Ophthalmology, London, UK. .,Moorfields Eye Hospital NHS Foundation Trust, London, UK. .,Great Ormond Street Hospital for Children NHS Foundation Trust, London, UK.
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43
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Cell Culture Analysis of the Phagocytosis of Photoreceptor Outer Segments by Primary Mouse RPE Cells. Methods Mol Biol 2019. [PMID: 29564781 DOI: 10.1007/978-1-4939-7720-8_4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/18/2023]
Abstract
The phagocytosis of photoreceptor outer segments (POSs) by the retinal pigment epithelium (RPE) is essential for retinal homeostasis. Defects in this process can be caused by mutations in the photoreceptor cells, the RPE cells, or both cell types. This function can be experimentally investigated by performing an in vitro phagocytosis assay, in which cultured RPE cells are challenged with isolated POSs, and subsequently tested for their ability to degrade the POSs. A significant advantage of this approach is that mutant phenotypes can be attributed either to the photoreceptor or the RPE cells, by experimenting with different permutations of mutant and control photoreceptor and RPE cells. In this chapter, we detail the method for a double-immunofluorescence assay for analysis of the binding, ingestion, and subsequent degradation of isolated mouse POSs by cultured mouse primary RPE cells.
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44
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Umapathy A, Williams DS. Live Imaging of Organelle Motility in RPE Flatmounts. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1185:389-393. [PMID: 31884643 DOI: 10.1007/978-3-030-27378-1_64] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/20/2024]
Abstract
The retinal pigment epithelium (RPE) performs several functions that are crucial for normal retinal function and vision, including the daily phagocytosis of photoreceptor outer segment (POS) membranes. Defects in the motility and degradation of POS phagosomes may be associated with some inherited and age-related retinal degenerations. Given the apical to basal translocation of phagosomes during maturation and degradation, studies of the underlying mechanisms require analyses of the dynamics in 3-D. In this chapter, we report a method for investigating the 3-D motility of POS phagosomes and lysosomes, utilizing high-speed, spinning disk confocal microscopy of live RPE flatmounts.
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Affiliation(s)
- Ankita Umapathy
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles (UCLA),, Los Angeles, CA, USA
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles (UCLA), Los Angeles, CA, USA.
- Department of Neurobiology, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA, USA.
- Molecular Biology Institute, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA, USA.
- Brain Research Institute, David Geffen School of Medicine, University of California, Los Angeles (UCLA), Los Angeles, CA, USA.
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45
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Curcio CA. Soft Drusen in Age-Related Macular Degeneration: Biology and Targeting Via the Oil Spill Strategies. Invest Ophthalmol Vis Sci 2018; 59:AMD160-AMD181. [PMID: 30357336 PMCID: PMC6733535 DOI: 10.1167/iovs.18-24882] [Citation(s) in RCA: 173] [Impact Index Per Article: 28.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
AMD is a major cause of legal blindness in older adults approachable through multidisciplinary research involving human tissues and patients. AMD is a vascular-metabolic-inflammatory disease, in which two sets of extracellular deposits, soft drusen/basal linear deposit (BLinD) and subretinal drusenoid deposit (SDD), confer risk for end-stages of atrophy and neovascularization. Understanding how deposits form can lead to insights for new preventions and therapy. The topographic correspondence of BLinD and SDD with cones and rods, respectively, suggest newly realized exchange pathways among outer retinal cells and across Bruch's membrane and the subretinal space, in service of highly evolved, eye-specific physiology. This review focuses on soft drusen/BLinD, summarizing evidence that a major ultrastructural component is large apolipoprotein B,E-containing, cholesterol-rich lipoproteins secreted by the retinal pigment epithelium (RPE) that offload unneeded lipids of dietary and outer segment origin to create an atherosclerosis-like progression in the subRPE-basal lamina space. Clinical observations and an RPE cell culture system combine to suggest that soft drusen/BLinD form when secretions of functional RPE back up in the subRPE-basal lamina space by impaired egress across aged Bruch's membrane-choriocapillary endothelium. The soft drusen lifecycle includes growth, anterior migration of RPE atop drusen, then collapse, and atrophy. Proof-of-concept studies in humans and animal models suggest that targeting the “Oil Spill in Bruch's membrane” offers promise of treating a process in early AMD that underlies progression to both end-stages. A companion article addresses the antecedents of soft drusen within the biology of the macula.
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Affiliation(s)
- Christine A Curcio
- Department of Ophthalmology and Visual Sciences, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States
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46
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Curcio CA. Antecedents of Soft Drusen, the Specific Deposits of Age-Related Macular Degeneration, in the Biology of Human Macula. Invest Ophthalmol Vis Sci 2018; 59:AMD182-AMD194. [PMID: 30357337 PMCID: PMC6733529 DOI: 10.1167/iovs.18-24883] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
AMD pathobiology was irreversibly changed by the recent discovery of extracellular cholesterol-containing deposits in the subretinal space, between the photoreceptors and retinal pigment epithelium (RPE), called subretinal drusenoid deposits (SDDs). SDDs strikingly mirror the topography of rod photoreceptors in human macula, raising the question of whether an equivalent process results in a deposition related to foveal cones. Herein we propose that AMD's pathognomonic lesion-soft drusen and basal linear deposit (BLinD, same material, diffusely distributed)-is the leading candidate. Epidemiologic, clinical, and histologic data suggest that these deposits are most abundant in the central macula, under the fovea. Strong evidence presented in a companion article supports the idea that the dominant ultrastructural component is large apolipoprotein B,E-containing lipoproteins, constitutively secreted by RPE. Lipoprotein fatty acids are dominated by linoleate (implicating diet) rather than docosahexaenoate (implicating photoreceptors); we seek within the retina cellular relationships and dietary drivers to explain soft druse topography. The delivery of xanthophyll pigments to highly evolved and numerous Müller cells in the human fovea, through RPE, is one strong candidate, because Müller cells are the main reservoir of these pigments, which replenish from diet. We propose that the evolution of neuroglial relations and xanthophyll delivery that underlie exquisite human foveal vision came with a price, that is, soft drusen and sequela, long after our reproductive years.
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Affiliation(s)
- Christine A Curcio
- Department of Ophthalmology and Visual Sciences, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama, United States
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47
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Hazim RA, Volland S, Yen A, Burgess BL, Williams DS. Rapid differentiation of the human RPE cell line, ARPE-19, induced by nicotinamide. Exp Eye Res 2018; 179:18-24. [PMID: 30336127 DOI: 10.1016/j.exer.2018.10.009] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2018] [Revised: 09/17/2018] [Accepted: 10/13/2018] [Indexed: 12/31/2022]
Abstract
Human RPE cell lines, especially the ARPE-19 cell line, are widely-used in eye research, as well as general epithelial cell studies. In comparison with primary RPE cells, they offer relative convenience and consistency, but cultures derived from these lines are typically not well differentiated. We describe a simple, rapid method to establish cultures from ARPE-19 cells, with significantly improved epithelial cell morphology and cytoskeletal organization, and RPE-related functions. We identify the presence of nicotinamide, a member of the vitamin B family, as an essential factor in promoting the observed differentiation, indicating the importance of metabolism in RPE cell differentiation.
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Affiliation(s)
- Roni A Hazim
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles, CA, USA
| | - Stefanie Volland
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles, CA, USA
| | - Alice Yen
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles, CA, USA
| | - Barry L Burgess
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles, CA, USA
| | - David S Williams
- Department of Ophthalmology and Stein Eye Institute, University of California, Los Angeles, CA, USA; Department of Neurobiology, David Geffen School of Medicine at UCLA, University of California, Los Angeles, CA, USA; Molecular Biology Institute, University of California, Los Angeles, CA, USA; Brain Research Institute, University of California, Los Angeles, CA, USA.
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48
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Zhang Q, Presswalla F, Feathers K, Cao X, Hughes BA, Zacks DN, Thompson DA, Miller JML. A platform for assessing outer segment fate in primary human fetal RPE cultures. Exp Eye Res 2018; 178:212-222. [PMID: 30336126 DOI: 10.1016/j.exer.2018.10.008] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Revised: 10/01/2018] [Accepted: 10/13/2018] [Indexed: 12/14/2022]
Abstract
The daily shedding and renewal of photoreceptor outer segments (OS) is critical for maintaining vision. This process relies on the efficient uptake, degradation, and sorting of shed OS material by the retinal pigment epithelium (RPE). Poor OS degradation has been linked to retinal degenerations such as Stargardt disease and may contribute to macular degeneration. While primary human fetal RPE cultures have emerged as a valuable model of in vivo human RPE function, surprisingly few studies have utilized the model for tracking the degradation and fate of OS components in the RPE. Here, we establish an improved platform for studying this topic by modifying existing protocols and creating new methods. Our human fetal culture model facilitates studies of RPE secretion in response to OS ingestion, preserves RPE differentiation and polarization during live-cell imaging of OS phagocytosis, and minimizes costs. We optimize Mer tyrosine kinase-dependent OS phagocytosis assays specifically in human fetal cultures and provide a simple and accurate method for measuring total OS consumption by the RPE. Finally, we utilize chemical transfection, dextran labeling, and immunocytochemistry to evaluate key players in OS degradation, including lysosomes and autophagy proteins. To facilitate quantification of autophagy vesicles, we develop customized image analysis macros in the Fiji/ImageJ software environment. These protocols will facilitate a broad range of studies in human fetal RPE cultures aimed at determining the ultimate fate of OS components after ingestion, a critical step in understanding the pathogenesis of numerous retinal diseases.
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Affiliation(s)
- Qitao Zhang
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Feriel Presswalla
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Kecia Feathers
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Xu Cao
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Bret A Hughes
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - David N Zacks
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA
| | - Debra A Thompson
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA; Department of Biological Chemistry, University of Michigan, Ann Arbor, MI, USA
| | - Jason M L Miller
- Department of Ophthalmology and Visual Sciences, Kellogg Eye Center, Michigan Medicine, University of Michigan, Ann Arbor, MI, USA.
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49
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Dhingra A, Bell BA, Peachey NS, Daniele LL, Reyes-Reveles J, Sharp RC, Jun B, Bazan NG, Sparrow JR, Kim HJ, Philp NJ, Boesze-Battaglia K. Microtubule-Associated Protein 1 Light Chain 3B, (LC3B) Is Necessary to Maintain Lipid-Mediated Homeostasis in the Retinal Pigment Epithelium. Front Cell Neurosci 2018; 12:351. [PMID: 30349463 PMCID: PMC6186781 DOI: 10.3389/fncel.2018.00351] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 09/19/2018] [Indexed: 12/25/2022] Open
Abstract
Like other neurons, retinal cells utilize autophagic pathways to maintain cell homeostasis. The mammalian retina relies on heterophagy and selective autophagy to efficiently degrade and metabolize ingested lipids with disruption in autophagy associated degradation contributing to age related retinal disorders. The retinal pigment epithelium (RPE) supports photoreceptor cell renewal by daily phagocytosis of shed photoreceptor outer segments (OS). The daily ingestion of these lipid-rich OS imposes a constant degradative burden on these terminally differentiated cells. These cells rely on Microtubule-Associated Protein 1 Light Chain 3 (LC3) family of proteins for phagocytic clearance of the ingested OS. The LC3 family comprises of three highly homologous members, MAP1LC3A (LC3A), MAP1LC3B (LC3B), and MAP1LC3C (LC3C). The purpose of this study was to determine whether the LC3B isoform plays a specific role in maintaining RPE lipid homeostasis. We examined the RPE and retina of the LC3B-/- mouse as a function of age using in vivo ocular imaging and electroretinography coupled with ex vivo, lipidomic analyses of lipid mediators, assessment of bisretinoids as well as imaging of lipid aggregates. Deletion of LC3B resulted in defects within the RPE including increased phagosome accumulation, decreased fatty acid oxidation and a subsequent increase in RPE and sub-RPE lipid deposits. Age-dependent RPE changes included elevated levels of oxidized cholesterol, deposition of 4-HNE lipid peroxidation products, bisretinoid lipofuscin accumulation, and subretinal migration of microglia, collectively likely contributing to loss of retinal function. These observations are consistent with a critical role for LC3B-dependent processes in the maintenance of normal lipid homeostasis in the aging RPE, and suggest that LC3 isoform specific disruption in autophagic processes contribute to AMD-like pathogenesis.
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Affiliation(s)
- Anuradha Dhingra
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Brent A Bell
- Scheie Eye Institute, University of Pennsylvania, Philadelphia, PA, United States
| | - Neal S Peachey
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, United States.,Louis Stokes Cleveland VA Medical Center, Cleveland, OH, United States.,Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, OH, United States
| | - Lauren L Daniele
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Juan Reyes-Reveles
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Rachel C Sharp
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
| | - Bokkyoo Jun
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Nicolas G Bazan
- Neuroscience Center of Excellence, School of Medicine, Louisiana State University Health New Orleans, New Orleans, LA, United States
| | - Janet R Sparrow
- Department of Ophthalmology, Columbia University Medical Center, New York, NY, United States
| | - Hye Jin Kim
- Department of Ophthalmology, Columbia University Medical Center, New York, NY, United States
| | - Nancy J Philp
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, United States
| | - Kathleen Boesze-Battaglia
- Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, United States
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50
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Yu B, Egbejimi A, Dharmat R, Xu P, Zhao Z, Long B, Miao H, Chen R, Wensel TG, Cai J, Chen Y. Phagocytosed photoreceptor outer segments activate mTORC1 in the retinal pigment epithelium. Sci Signal 2018; 11:11/532/eaag3315. [PMID: 29844054 DOI: 10.1126/scisignal.aag3315] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The retinal pigment epithelium (RPE) transports nutrients and metabolites between the microvascular bed that maintains the outer retina and photoreceptor neurons. The RPE removes photoreceptor outer segments (POS) by receptor-mediated phagocytosis, a process that peaks in the morning. Uptake and degradation of POS initiates signaling cascades in the RPE. Upstream stimuli from various metabolic activities converge on mechanistic target of rapamycin complex 1 (mTORC1), and aberrant mTORC1 signaling is implicated in aging and age-related degeneration of the RPE. We measured mTORC1-mediated responses to RPE phagocytosis in vivo and in vitro. During the morning burst of POS shedding, there was transient activation of mTORC1-mediated signaling in the RPE. POS activated mTORC1 through lysosome-independent mechanisms, and engulfed POS served as a docking platform for mTORC1 assembly. The identification of POS as endogenous stimuli of mTORC1 in the RPE provides a mechanistic link underlying the photoreceptor-RPE interaction in the outer retina.
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Affiliation(s)
- Bo Yu
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Anuoluwapo Egbejimi
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Rachayata Dharmat
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA
| | - Pei Xu
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Zhenyang Zhao
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Bo Long
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Hongyu Miao
- Department of Biostatistics and Data Science, School of Public Health, University of Texas Health Science Center, Houston, TX 77030, USA
| | - Rui Chen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX 77030, USA.,Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030, USA
| | - Theodore G Wensel
- Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030, USA
| | - Jiyang Cai
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA.,Department of Neuroscience, Cell Biology and Anatomy, University of Texas Medical Branch, Galveston, TX 77555, USA
| | - Yan Chen
- Department of Ophthalmology and Visual Science, University of Texas Medical Branch, Galveston, TX 77555, USA. .,Department of Neuroscience, Cell Biology and Anatomy, University of Texas Medical Branch, Galveston, TX 77555, USA
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