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Bergman MR, Hernandez SA, Deffler C, Yeo J, Deravi LF. Design and Characterization of Model Systems that Promote and Disrupt Transparency of Vertebrate Crystallins In Vitro. Adv Sci (Weinh) 2023; 10:e2303279. [PMID: 37897315 PMCID: PMC10724405 DOI: 10.1002/advs.202303279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/20/2023] [Revised: 08/31/2023] [Indexed: 10/30/2023]
Abstract
Positioned within the eye, the lens supports vision by transmitting and focusing light onto the retina. As an adaptive glassy material, the lens is constituted primarily by densely-packed, polydisperse crystallin proteins that organize to resist aggregation and crystallization at high volume fractions, yet the details of how crystallins coordinate with one another to template and maintain this transparent microstructure remain unclear. The role of individual crystallin subtypes (α, β, and γ) and paired subtype compositions, including how they experience and resist crowding-induced turbidity in solution, is explored using combinations of spectrophotometry, hard-sphere simulations, and surface pressure measurements. After assaying crystallin combinations, β-crystallins emerged as a principal component in all mixtures that enabled dense fluid-like packing and short-range order necessary for transparency. These findings helped inform the design of lens-like hydrogel systems, which are used to monitor and manipulate the loss of transparency under different crowding conditions. When taken together, the findings illustrate the design and characterization of adaptive materials made from lens proteins that can be used to better understand mechanisms regulating transparency.
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Affiliation(s)
- Michael R. Bergman
- Department of Chemistry and Chemical BiologyNortheastern University360 Huntington AveBostonMA02115USA
| | - Sophia A. Hernandez
- Department of Chemistry and Chemical BiologyNortheastern University360 Huntington AveBostonMA02115USA
| | - Caitlin Deffler
- Department of Chemistry and Chemical BiologyNortheastern University360 Huntington AveBostonMA02115USA
| | - Jingjie Yeo
- Sibley School of Mechanical and Aerospace EngineeringCornell University413 Upson Hall, 124 Hoy RdIthacaNY14850USA
| | - Leila F. Deravi
- Department of Chemistry and Chemical BiologyNortheastern University360 Huntington AveBostonMA02115USA
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2
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Tashiro M, Nakamura A, Kuratani Y, Takada M, Iwamoto S, Oka M, Ando S. Effects of truncations in the N- and C-terminal domains of filensin on filament formation with phakinin in cell-free conditions and cultured cells. FEBS Open Bio 2023; 13:1990-2004. [PMID: 37615966 PMCID: PMC10626283 DOI: 10.1002/2211-5463.13700] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2023] [Revised: 07/27/2023] [Accepted: 08/22/2023] [Indexed: 08/25/2023] Open
Abstract
Filensin and phakinin are lens fiber cell-specific proteins that constitute the beaded filaments (BFs) that are critical for maintaining lens transparency. In the Shumiya cataract rat, filensin 94 kDa undergoes N- and C-terminal proteolytic processing to give a transient 50 kDa fragment and a final 38 kDa fragment, just before opacification. To characterize the effects of this processing on filensin function, recombinant proteins representing the two filensin fragments, termed Fil(30-416) and Fil(30-369), respectively, were examined. Fil(30-416) lacks the N-terminal 29 amino acids and the C-terminal 248 amino acids. Fil(30-369) lacks the N-terminal 29 residues and the C-terminal 295 residues. In cell-free assembly characterized by electron microscopy, filensin and Fil(30-416) co-polymerized with phakinin and formed rugged, entangled filaments, whereas Fil(30-369) formed only aggregates. In cultured SW-13 and MCF-7 cells expressing fluorescent fusion proteins, filensin and Fil(30-416) co-polymerized with phakinin and formed cytoplasmic sinuous filaments with different widths, while Fil(30-369) gave aggregates. Therefore, while truncation of the N-terminal 29 amino acids did not affect filament formation, truncation of the C-terminal 295 but not the 248 residues resulted in failure of filament formation. These results indicate that the tail B region (residues 370-416) of rat filensin is essential for filament formation with phakinin. Truncation of the tail B region by proteolytic processing in the cataract rat lens might interfere with BF formation and thereby contribute to opacification.
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Affiliation(s)
- Moe Tashiro
- Faculty of Biotechnology and Life ScienceSojo UniversityKumamotoJapan
| | - Akari Nakamura
- Faculty of Biotechnology and Life ScienceSojo UniversityKumamotoJapan
| | - Yamato Kuratani
- Faculty of Biotechnology and Life ScienceSojo UniversityKumamotoJapan
| | - Miyako Takada
- Faculty of Biotechnology and Life ScienceSojo UniversityKumamotoJapan
| | - Satoshi Iwamoto
- Faculty of Biotechnology and Life ScienceSojo UniversityKumamotoJapan
| | - Mikako Oka
- Faculty of PharmacyKeio UniversityTokyoJapan
- Present address:
Yokohama University of Pharmacy601 Matano‐cho, Totsuka‐kuYokohama245‐0066Japan
| | - Shoji Ando
- Faculty of Biotechnology and Life ScienceSojo UniversityKumamotoJapan
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3
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He M, Zhou G, Lin Q, Zhou N. The role of mip in the development of lens in zebrafish. Gene Expr Patterns 2023; 49:119330. [PMID: 37369320 DOI: 10.1016/j.gep.2023.119330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2023] [Revised: 06/10/2023] [Accepted: 06/23/2023] [Indexed: 06/29/2023]
Abstract
Major intrinsic protein (MIP) functions as a water channel and a cell-junction molecule in the vertebrate eye lens. The pathogenic mechanism behind the loss of MIP function in the lens, which leads to degraded optical quality and cataract formation, is still unclear. In this study, a zebrafish model with the mipb mutant was produced. The expression of mipb mRNA and protein was dramatically reduced in the mutant. Immunological analysis reveals that loss function of mip leads to the diffuse distribution of ZL-1 in the mutant lens. Furthermore, in situ hybridization reveals that mip knockout results in a decrease in the transcripts of beaded filament structural protein 2 (Bfsp2) in the lens. Histology study shows that lens fibers in the mutants are less uniform in shape and the fiber arrangement is disrupted. The presented data provides evidence for the essential role of mipb in the development of lens fibers. The absence of mipb during lens formation is likely to result in aberrant lens fiber formation and impaired lens function.
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Affiliation(s)
- Mingyan He
- Department of Ophthalmology, the Second Affiliated Hospital of Harbin Medical University, 150081, Harbin, China
| | - Guangkai Zhou
- The Third Affiliated Hospital of Harbin Medical University, 150081, Harbin, China
| | - Qinghong Lin
- Department of Ophthalmology, the Second Affiliated Hospital of Harbin Medical University, 150081, Harbin, China
| | - Nan Zhou
- Department of Ophthalmology, the Second Affiliated Hospital of Harbin Medical University, 150081, Harbin, China.
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4
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Rodriguez J, Tan Q, Šikić H, Taber LA, Bassnett S. The effect of fibre cell remodelling on the power and optical quality of the lens. J R Soc Interface 2023; 20:20230316. [PMID: 37727073 PMCID: PMC10509584 DOI: 10.1098/rsif.2023.0316] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 08/22/2023] [Indexed: 09/21/2023] Open
Abstract
Vertebrate eye lenses are uniquely adapted to form a refractive index gradient (GRIN) for improved acuity, and to grow slowly in size despite constant cell proliferation. The mechanisms behind these adaptations remain poorly understood. We hypothesize that cell compaction contributes to both. To test this notion, we examined the relationship between lens size and shape, refractive characteristics and the cross-sectional areas of constituent fibre cells in mice of different ages. We developed a block-face imaging method to visualize cellular cross sections and found that the cross-sectional areas of fibre cells rose and then decreased over time, with the most significant reduction occurring in denucleating cells in the adult lens cortex, followed by cells in the embryonic nucleus. These findings help reconcile differences between the predictions of lens growth models and empirical data. Biomechanical simulations suggested that compressive forces generated from continuous deposition of fibre cells could contribute to cellular compaction. However, optical measurements revealed that the GRIN did not mirror the pattern of cellular compaction, implying that compaction alone cannot account for GRIN formation and that additional mechanisms are likely to be involved.
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Affiliation(s)
- J. Rodriguez
- Department of Basic Sciences, University of Health Sciences and Pharmacy in St. Louis, 1 Pharmacy Place, St. Louis, MO 63110, USA
| | - Q. Tan
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, 660 South Euclid Ave, Campus Box 8096, St. Louis, MO 63110, USA
| | - H. Šikić
- Department of Mathematics, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - L. A. Taber
- Department of Biomedical Engineering, Washington University, St. Louis, MO 63130, USA
| | - S. Bassnett
- Department of Ophthalmology & Visual Sciences, Washington University School of Medicine, 660 South Euclid Ave, Campus Box 8096, St. Louis, MO 63110, USA
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Gerhart J, George-Weinstein M. Myo/Nog Cells: The Jekylls and Hydes of the Lens. Cells 2023; 12:1725. [PMID: 37443759 PMCID: PMC10340492 DOI: 10.3390/cells12131725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Revised: 06/21/2023] [Accepted: 06/24/2023] [Indexed: 07/15/2023] Open
Abstract
Herein, we review a unique and versatile lineage composed of Myo/Nog cells that may be beneficial or detrimental depending on their environment and nature of the pathological stimuli they are exposed to. While we will focus on the lens, related Myo/Nog cell behaviors and functions in other tissues are integrated into the narrative of our research that spans over three decades, examines multiple species and progresses from early stages of embryonic development to aging adults. Myo/Nog cells were discovered in the embryonic epiblast by their co-expression of the skeletal muscle-specific transcription factor MyoD, the bone morphogenetic protein inhibitor Noggin and brain-specific angiogenesis inhibitor 1. They were tracked from the epiblast into the developing lens, revealing heterogeneity of cell types within this structure. Depletion of Myo/Nog cells in the epiblast results in eye malformations arising from the absence of Noggin. In the adult lens, Myo/Nog cells are the source of myofibroblasts whose contractions produce wrinkles in the capsule. Eliminating this population within the rabbit lens during cataract surgery reduces posterior capsule opacification to below clinically significant levels. Parallels are drawn between the therapeutic potential of targeting Myo/Nog cells to prevent fibrotic disease in the lens and other ocular tissues.
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Jarrin M, Kalligeraki AA, Uwineza A, Cawood CS, Brown AP, Ward EN, Le K, Freitag-Pohl S, Pohl E, Kiss B, Tapodi A, Quinlan RA. Independent Membrane Binding Properties of the Caspase Generated Fragments of the Beaded Filament Structural Protein 1 (BFSP1) Involves an Amphipathic Helix. Cells 2023; 12:1580. [PMID: 37371051 DOI: 10.3390/cells12121580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 06/04/2023] [Accepted: 06/05/2023] [Indexed: 06/29/2023] Open
Abstract
BACKGROUND BFSP1 (beaded filament structural protein 1) is a plasma membrane, Aquaporin 0 (AQP0/MIP)-associated intermediate filament protein expressed in the eye lens. BFSP1 is myristoylated, a post-translation modification that requires caspase cleavage at D433. Bioinformatic analyses suggested that the sequences 434-452 were α-helical and amphipathic. METHODS AND RESULTS By CD spectroscopy, we show that the addition of trifluoroethanol induced a switch from an intrinsically disordered to a more α-helical conformation for the residues 434-467. Recombinantly produced BFSP1 fragments containing this amphipathic helix bind to lens lipid bilayers as determined by surface plasmon resonance (SPR). Lastly, we demonstrate by transient transfection of non-lens MCF7 cells that these same BFSP1 C-terminal sequences localise to plasma membranes and to cytoplasmic vesicles. These can be co-labelled with the vital dye, lysotracker, but other cell compartments, such as the nuclear and mitochondrial membranes, were negative. The N-terminal myristoylation of the amphipathic helix appeared not to change either the lipid affinity or membrane localisation of the BFSP1 polypeptides or fragments we assessed by SPR and transient transfection, but it did appear to enhance its helical content. CONCLUSIONS These data support the conclusion that C-terminal sequences of human BFSP1 distal to the caspase site at G433 have independent membrane binding properties via an adjacent amphipathic helix.
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Affiliation(s)
- Miguel Jarrin
- Department of Biosciences, Upper Mountjoy Science Site, The University of Durham, South Road, Durham DH1 3LE, UK
- Biophysical Sciences Institute, Durham University, Upper Mountjoy, South Road, Durham DH1 3LE, UK
| | - Alexia A Kalligeraki
- Department of Biosciences, Upper Mountjoy Science Site, The University of Durham, South Road, Durham DH1 3LE, UK
- Biophysical Sciences Institute, Durham University, Upper Mountjoy, South Road, Durham DH1 3LE, UK
| | - Alice Uwineza
- Department of Biosciences, Upper Mountjoy Science Site, The University of Durham, South Road, Durham DH1 3LE, UK
- Biophysical Sciences Institute, Durham University, Upper Mountjoy, South Road, Durham DH1 3LE, UK
| | - Chris S Cawood
- Department of Biosciences, Upper Mountjoy Science Site, The University of Durham, South Road, Durham DH1 3LE, UK
- Biophysical Sciences Institute, Durham University, Upper Mountjoy, South Road, Durham DH1 3LE, UK
| | - Adrian P Brown
- Department of Biosciences, Upper Mountjoy Science Site, The University of Durham, South Road, Durham DH1 3LE, UK
| | - Edward N Ward
- Department of Biosciences, Upper Mountjoy Science Site, The University of Durham, South Road, Durham DH1 3LE, UK
- Biophysical Sciences Institute, Durham University, Upper Mountjoy, South Road, Durham DH1 3LE, UK
| | - Khoa Le
- Biophysical Sciences Institute, Durham University, Upper Mountjoy, South Road, Durham DH1 3LE, UK
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
| | - Stefanie Freitag-Pohl
- Department of Chemistry, Durham University, Lower Mountjoy, South Road, Durham DH1 3LE, UK
| | - Ehmke Pohl
- Biophysical Sciences Institute, Durham University, Upper Mountjoy, South Road, Durham DH1 3LE, UK
- Department of Chemistry, Durham University, Lower Mountjoy, South Road, Durham DH1 3LE, UK
| | - Bence Kiss
- Department of Biochemistry and Medical Chemistry, Medical School, University of Pécs, 7624 Pécs, Hungary
| | - Antal Tapodi
- Department of Biosciences, Upper Mountjoy Science Site, The University of Durham, South Road, Durham DH1 3LE, UK
- Biophysical Sciences Institute, Durham University, Upper Mountjoy, South Road, Durham DH1 3LE, UK
- Department of Biochemistry and Medical Chemistry, Medical School, University of Pécs, 7624 Pécs, Hungary
| | - Roy A Quinlan
- Department of Biosciences, Upper Mountjoy Science Site, The University of Durham, South Road, Durham DH1 3LE, UK
- Biophysical Sciences Institute, Durham University, Upper Mountjoy, South Road, Durham DH1 3LE, UK
- Department of Biological Structure, University of Washington, Seattle, WA 98195, USA
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7
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D’Antin JC, Tresserra F, Barraquer RI, Michael R. Soemmerring's Rings Developed around IOLs, in Human Donor Eyes, Can Present Internal Transparent Areas. Int J Mol Sci 2022; 23:13294. [PMID: 36362082 PMCID: PMC9656497 DOI: 10.3390/ijms232113294] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 10/26/2022] [Accepted: 10/27/2022] [Indexed: 02/09/2024] Open
Abstract
Soemmerring's rings consist of a ring of lens epithelial derived cells that grow along the periphery of an aphakic lens capsule, or around an intraocular lens. These rings when visualized frontally, appear opaque, however, in some cases the cells that compose these rings are organized in the same fashion as those in normal transparent adult lenses. Thus, our purpose was to test whether any part of the adult Soemmerring's ring could be transparent and how this related to morphological factors. To study this, 16 Soemmerring's rings were extracted from donor eye globes. After imaging, they were thickly sectioned sagittally in order to analyze the degrees of transparency of different areas. All samples were also histologically analyzed using alpha smooth muscle actin, Vimentin, wheat germ agglutinin and DAPI. Our results showed that many samples had some transparent areas, mostly towards the center of their cross-section. Of the factors that we analyzed, only lens fiber organization at the bow region and an increased area of mature lens fiber cells had a significant relation to the degree of transparency at the center. Thus, we can conclude that as Soemmerring's rings mature, they can develop organized and transparent areas of lens cells.
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Affiliation(s)
- Justin Christopher D’Antin
- Institut Universitari Barraquer, Universitat Autònoma de Barcelona, 08021 Barcelona, Spain
- Centro de Oftalmología Barraquer, 08021 Barcelona, Spain
| | - Francesc Tresserra
- Department of Pathology, Institut Universitari Dexeus, 08028 Barcelona, Spain
| | - Rafael I. Barraquer
- Institut Universitari Barraquer, Universitat Autònoma de Barcelona, 08021 Barcelona, Spain
- Centro de Oftalmología Barraquer, 08021 Barcelona, Spain
- Department of Medicine, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, 08017 Barcelona, Spain
| | - Ralph Michael
- Institut Universitari Barraquer, Universitat Autònoma de Barcelona, 08021 Barcelona, Spain
- Centro de Oftalmología Barraquer, 08021 Barcelona, Spain
- Institute for Medical Informatics, Statistics, and Epidemiology (IMISE), Leipzig University, 04109 Leipzig, Germany
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8
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Zahraei A, Guo G, Varnava KG, Demarais NJ, Donaldson PJ, Grey AC. Mapping Glucose Uptake, Transport and Metabolism in the Bovine Lens Cortex. Front Physiol 2022; 13:901407. [PMID: 35711316 PMCID: PMC9194507 DOI: 10.3389/fphys.2022.901407] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2022] [Accepted: 05/04/2022] [Indexed: 11/13/2022] Open
Abstract
Purpose: To spatially correlate the pattern of glucose uptake to glucose transporter distributions in cultured lenses and map glucose metabolism in different lens regions. Methods: Ex vivo bovine lenses were incubated in artificial aqueous humour containing normoglycaemic stable isotopically-labelled (SIL) glucose (5 mM) for 5 min-20 h. Following incubations, lenses were frozen for subsequent matrix-assisted laser desorption/ionisation (MALDI) imaging mass spectrometry (IMS) analysis using high resolution mass spectrometry. Manually dissected, SIL-incubated lenses were subjected to gas chromatography-mass spectrometry (GC-MS) to verify the identity of metabolites detected by MALDI-IMS. Normal, unincubated lenses were manually dissected into epithelium flat mounts and fibre cell fractions and then subjected to either gel-based proteomic analysis (Gel-LC/MS) to detect facilitative glucose transporters (GLUTs) by liquid chromatography tandem mass spectrometry (LC-MS/MS). Indirect immunofluorescence and confocal microscopy of axial lens sections from unincubated fixed lenses labelled with primary antibodies specific for GLUT 1 or GLUT 3 were utilised for protein localisation. Results: SIL glucose uptake at 5 min was concentrated in the equatorial region of the lens. At later timepoints, glucose gradually distributed throughout the epithelium and the cortical lens fibres, and eventually the deeper lens nucleus. SIL glucose metabolites found in glycolysis, the sorbitol pathway, the pentose phosphate pathway, and UDP-glucose formation were mapped to specific lens regions, with distinct regional signal changes up to 20 h of incubation. Spatial proteomic analysis of the lens epithelium detected GLUT1 and GLUT3. GLUT3 was in higher abundance than GLUT1 throughout the epithelium, while GLUT1 was more abundant in lens fibre cells. Immunohistochemical mapping localised GLUT1 to epithelial and cortical fibre cell membranes. Conclusion: The major uptake site of glucose in the bovine lens has been mapped to the lens equator. SIL glucose is rapidly metabolised in epithelial and fibre cells to many metabolites, which are most abundant in the metabolically more active cortical fibre cells in comparison to central fibres, with low levels of metabolic activity observed in the nucleus.
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Affiliation(s)
- Ali Zahraei
- Department of Physiology in the School of Medical Sciences, Auckland, New Zealand
| | - George Guo
- Department of Physiology in the School of Medical Sciences, Auckland, New Zealand.,Mass Spectrometry Hub, Auckland, New Zealand
| | - Kyriakos G Varnava
- Department of Physiology in the School of Medical Sciences, Auckland, New Zealand.,Mass Spectrometry Hub, Auckland, New Zealand
| | - Nicholas J Demarais
- Mass Spectrometry Hub, Auckland, New Zealand.,School of Biological Sciences, University of Auckland, Auckland, New Zealand
| | - Paul J Donaldson
- Department of Physiology in the School of Medical Sciences, Auckland, New Zealand
| | - Angus C Grey
- Department of Physiology in the School of Medical Sciences, Auckland, New Zealand.,Mass Spectrometry Hub, Auckland, New Zealand
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9
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Varadaraj K, FitzGerald PG, Kumari SS. Deletion of beaded filament proteins or the C-terminal end of Aquaporin 0 causes analogous abnormal distortion aberrations in mouse lens. Exp Eye Res 2021; 209:108645. [PMID: 34087204 DOI: 10.1016/j.exer.2021.108645] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Revised: 05/22/2021] [Accepted: 05/26/2021] [Indexed: 11/28/2022]
Abstract
Lens-specific beaded filament (BF) proteins CP49 and filensin interact with the C-terminus of the water channel protein Aquaporin 0 (AQP0). Previously we have reported that a C-terminally end-deleted AQP0-expressing transgenic mouse model AQP0ΔC/ΔC developed abnormal optical aberrations in the lens. This investigation was undertaken to find out whether the total loss of the BF structural proteins alter the optical properties of the lens and cause optical aberrations similar to those in AQP0ΔC/ΔC lenses; also, to map the changes in the optical quality as a function of age in the single or double BF protein knockouts as well as to assess whether there is any significant change in the water channel function of AQP0 in these knockouts. A double knockout mouse (2xKO) model for CP49 and filensin was developed by crossing CP49-KO and filensin-KO mice. Wild type, CP49-KO, filensin-KO, and 2xKO lenses at different ages, and AQP0ΔC/ΔC lenses at postnatal day-17 were imaged through the optical axis and compared for optical quality and focusing property. All three knockout models showed loss of transparency, and development of abnormal optical distortion aberration similar to that in AQP0ΔC/ΔC. Copper grid focusing by the lenses at 6, 9 and 12 months of age showed an increase in aberrations as age advanced. With progression in age, the grid images produced by the lenses of all KO models showed a transition from a positive barrel distortion aberration to a pincushion distortion aberration with the formation of three distinct aberration zones similar to those produced by AQP0ΔC/ΔC lenses. Water permeability of fiber cell membrane vesicles prepared from CP49-KO, filensin-KO and 2xKO models, measured using the osmotic shrinking method, remained similar to that of the wild type without any statistically significant alteration (P > 0.05). Western blotting and quantification revealed the expression of comparable quantities of AQP0 in all three BF protein KOs. Our study reveals that loss of single or both beaded filament proteins significantly affect lens refractive index gradient, transparency and focusing ability in an age-dependent manner and the interaction of BF proteins with AQP0 is critical for the proper functioning of the lens. The presence of BF proteins is necessary to prevent abnormal optical aberrations and maintain homeostasis in the aging lens.
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Affiliation(s)
| | - Paul G FitzGerald
- Cell Biology and Human Anatomy, School of Medicine, University of California-Davis, Davis, CA, USA
| | - S Sindhu Kumari
- Physiology and Biophysics, Renaissance School of Medicine, Stony Brook University, NY, USA.
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10
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Koch CR, D'Antin JC, Tresserra F, Barraquer RI, Michael R. Histological comparison of in vitro and in vivo development of peripheral posterior capsule opacification in human donor tissue. Exp Eye Res 2019; 188:107807. [PMID: 31539543 DOI: 10.1016/j.exer.2019.107807] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 09/16/2019] [Accepted: 09/16/2019] [Indexed: 01/05/2023]
Abstract
In order to study the mechanisms involved in the development of posterior capsule opacification (PCO) we compared in vivo developed PCO with PCO formed in tissue culture with focus on the periphery of the lens capsule to evaluate lens regeneration potential. We studied three human tissue groups: Cultured lens capsules after mock cataract surgery (n = 6, 30 days), lens capsules from donors that had previously undergone cataract surgery (IOL capsules) (n = 12) and intact lenses (n = 6). All samples were stained with Vimentin, alpha Smooth Muscle Actin, Picro Sirius Red (for collagen) and Paired box protein (Pax6). We found that cultured capsules and less developed IOL capsules consisted mainly of monolayers of mesenchymal cells, while more developed IOL capsules, contained lens epithelial cells (LECs), globular cells and lens fiber cells. Many IOL capsule samples expressed collagen I and III in areas where cells were in contact with the IOL. Pax6 had a similar dispersed distribution in less developed IOL capsules and cultured capsules, while more developed IOL capsules and intact lenses, concentrated Pax6 in LECs at the equatorial lens bow. The similarities between cultured capsules and less developed IOL capsules indicate that our in vitro developed PCO is comparable to early in vivo developed PCO. The similar morphology of more developed IOL capsules and intact lenses seems to indicate an attempt at lens regeneration.
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Affiliation(s)
- Camila Ribeiro Koch
- Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Barcelona, Spain; Department of Ophthalmology, University of São Paulo, São Paulo, Brazil
| | - Justin Christopher D'Antin
- Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Barcelona, Spain; Centro de Oftalmología Barraquer, Barcelona, Spain
| | | | - Rafael I Barraquer
- Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Barcelona, Spain; Centro de Oftalmología Barraquer, Barcelona, Spain; Universitat Internacional de Catalunya, Barcelona, Spain.
| | - Ralph Michael
- Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Barcelona, Spain; Centro de Oftalmología Barraquer, Barcelona, Spain
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11
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Gerhart J, Behling K, Paessler M, Milton L, Bramblett G, Garcia D, Pitts M, Hurtt R, Crawford M, Lackman R, Nguyen D, Infanti J, FitzGerald P, George-Weinstein M. Rhabdomyosarcoma and Wilms tumors contain a subpopulation of noggin producing, myogenic cells immunoreactive for lens beaded filament proteins. PLoS One 2019; 14:e0214758. [PMID: 30973903 PMCID: PMC6459534 DOI: 10.1371/journal.pone.0214758] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2018] [Accepted: 03/19/2019] [Indexed: 12/26/2022] Open
Abstract
Myo/Nog cells are identified by their expression of the skeletal muscle specific transcription factor MyoD and the bone morphogenetic protein inhibitor noggin, and binding of the G8 monoclonal antibody. Their release of noggin is critical for morphogenesis and skeletal myogenesis. In the adult, Myo/Nog cells are present in normal tissues, wounds and skin tumors. Myo/Nog cells in the lens give rise to myofibroblasts that synthesize skeletal muscle proteins. The purpose of this study was to screen human lens tissue, rhabdomyosarcoma cell lines, and tissue sections from rhabdomyosarcoma, Wilms and tumors lacking features of skeletal muscle for co-localization of antibodies to Myo/Nog cell markers and the lens beaded filament proteins filensin and CP49. Immunofluorescence localization experiments revealed that Myo/Nog cells of the lens bind antibodies to beaded filament proteins. Co-localization of antibodies to G8, noggin, filensin and CP49 was observed in most RC13 and a subpopulation of RD human rhabdomyosarcoma cell lines. Western blotting with beaded filament antibodies revealed bands of similar molecular weights in RC13 and murine lens cells. Human alveolar, embryonal, pleomorphic and spindle cell rhabdomyosarcomas and Wilms tumors contained a subpopulation of cells immunoreactive for G8, noggin, MyoD and beaded filaments. G8 was also co-localized with filensin mRNA. Staining for beaded filament proteins was not detected in G8 positive cells in leiomyosarcomas, squamous and basal cell carcinomas, syringocarciomas and malignant melanomas. Lens beaded filament proteins were thought to be present only in the lens. Myo/Nog-like cells immunoreactive for beaded filaments may be diagnostic of tumors related to the skeletal muscle lineage.
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Affiliation(s)
- Jacquelyn Gerhart
- Philadelphia College of Osteopathic Medicine, Philadelphia, PA, United States of America
| | - Kathryn Behling
- Dept. of Biomedical Sciences, Cooper Medical School of Rowan University, Camden, NJ, United States of America
- Dept. of Pathology, Cooper University Health Care, Camden, NJ, United States of America
| | - Michele Paessler
- Division of Hematopathology, Children’s Hospital of Philadelphia, Philadelphia, PA, United States of America
| | - LaBraya Milton
- Dept. of Orthopaedics, Cooper University Health Care, Camden, NJ, United States of America
| | - Gregory Bramblett
- Lankenau Institute for Medical Research, Wynnewood, PA, United States of America
| | - Denise Garcia
- Dept. of Biomedical Sciences, Cooper Medical School of Rowan University, Camden, NJ, United States of America
| | - Meghan Pitts
- Lankenau Institute for Medical Research, Wynnewood, PA, United States of America
| | - Reginald Hurtt
- Dept. of Biomedical Sciences, Cooper Medical School of Rowan University, Camden, NJ, United States of America
| | - Mitchell Crawford
- Philadelphia College of Osteopathic Medicine, Philadelphia, PA, United States of America
| | - Richard Lackman
- Dept. of Orthopaedics, Cooper University Health Care, Camden, NJ, United States of America
| | - Daniela Nguyen
- Philadelphia College of Osteopathic Medicine, Philadelphia, PA, United States of America
| | - Joseph Infanti
- Philadelphia College of Osteopathic Medicine, Philadelphia, PA, United States of America
| | - Paul FitzGerald
- Dept. of Cell Biology and Human Anatomy, University of California, Davis, Davis, CA, United States of America
| | - Mindy George-Weinstein
- Philadelphia College of Osteopathic Medicine, Philadelphia, PA, United States of America
- * E-mail:
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12
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Tapodi A, Clemens DM, Uwineza A, Jarrin M, Goldberg MW, Thinon E, Heal WP, Tate EW, Nemeth-Cahalan K, Vorontsova I, Hall JE, Quinlan RA. BFSP1 C-terminal domains released by post-translational processing events can alter significantly the calcium regulation of AQP0 water permeability. Exp Eye Res 2019; 185:107585. [PMID: 30790544 PMCID: PMC6713518 DOI: 10.1016/j.exer.2019.02.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Revised: 01/26/2019] [Accepted: 02/03/2019] [Indexed: 01/20/2023]
Abstract
BFSP1 (beaded filament structural protein 1, filensin) is a cytoskeletal protein expressed in the eye lens. It binds AQP0 in vitro and its C-terminal sequences have been suggested to regulate the water channel activity of AQP0. A myristoylated fragment from the C-terminus of BFSP1 was found in AQP0 enriched fractions. Here we identify BFSP1 as a substrate for caspase-mediated cleavage at several C-terminal sites including D433. Cleavage at D433 exposes a cryptic myristoylation sequence (434–440). We confirm that this sequence is an excellent substrate for both NMT1 and 2 (N-myristoyl transferase). Thus caspase cleavage may promote formation of myristoylated fragments derived from the BFSP1 C-terminus (G434-S665). Myristoylation at G434 is not required for membrane association. Biochemical fractionation and immunogold labeling confirmed that C-terminal BFSP1 fragments containing the myristoylation sequence colocalized with AQP0 in the same plasma membrane compartments of lens fibre cells. To determine the functional significance of the association of BFSP1 G434-S665 sequences with AQP0, we measured AQP0 water permeability in Xenopus oocytes co-transfected with transcripts expressing both AQP0 and various C-terminal domain fragments of BFSP1 generated by caspase cleavage. We found that different fragments dramatically alter the response of AQP0 to different concentrations of Ca2+. The complete C-terminal fragment (G434-S665) eliminates calcium regulation altogether. Shorter fragments can enhance regulation by elevated calcium or reverse the response, indicative of the regulatory potential of BFSP1 with respect to AQP0. In particular, elimination of the myristoylation site by the mutation G434A reverses the order of water permeability sensitivity to different Ca2+ concentrations.
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Affiliation(s)
- Antal Tapodi
- Department of Biosciences, The University of Durham, South Road, Durham, DH1 3LE, UK
| | | | - Alice Uwineza
- Department of Biosciences, The University of Durham, South Road, Durham, DH1 3LE, UK
| | - Miguel Jarrin
- Department of Biosciences, The University of Durham, South Road, Durham, DH1 3LE, UK
| | - Martin W Goldberg
- Department of Biosciences, The University of Durham, South Road, Durham, DH1 3LE, UK
| | - Emmanuelle Thinon
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, Wood Lane, London, W12 0BZ, UK; Institute of Chemical Biology, Molecular Sciences Research Hub, Imperial College London, Wood Lane, London, W12 0BZ, UK
| | - William P Heal
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, Wood Lane, London, W12 0BZ, UK; Institute of Chemical Biology, Molecular Sciences Research Hub, Imperial College London, Wood Lane, London, W12 0BZ, UK
| | - Edward W Tate
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London, Wood Lane, London, W12 0BZ, UK; Institute of Chemical Biology, Molecular Sciences Research Hub, Imperial College London, Wood Lane, London, W12 0BZ, UK
| | | | | | - James E Hall
- Physiology and Biophysics, UC Irvine, Irvine, CA, USA.
| | - Roy A Quinlan
- Department of Biosciences, The University of Durham, South Road, Durham, DH1 3LE, UK; Biophysical Sciences Institute, The University of Durham, South Road, Durham, DH1 3LE, UK.
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13
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Zhao Y, Wilmarth PA, Cheng C, Limi S, Fowler VM, Zheng D, David LL, Cvekl A. Proteome-transcriptome analysis and proteome remodeling in mouse lens epithelium and fibers. Exp Eye Res 2019; 179:32-46. [PMID: 30359574 PMCID: PMC6360118 DOI: 10.1016/j.exer.2018.10.011] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2018] [Revised: 08/31/2018] [Accepted: 10/20/2018] [Indexed: 12/21/2022]
Abstract
Epithelial cells and differentiated fiber cells represent distinct compartments in the ocular lens. While previous studies have revealed proteins that are preferentially expressed in epithelial vs. fiber cells, a comprehensive proteomics library comparing the molecular compositions of epithelial vs. fiber cells is essential for understanding lens formation, function, disease and regenerative potential, and for efficient differentiation of pluripotent stem cells for modeling of lens development and pathology in vitro. To compare protein compositions between the lens epithelium and fibers, we employed tandem mass spectrometry (2D-LC/MS) analysis of microdissected mouse P0.5 lenses. Functional classifications of the top 525 identified proteins into gene ontology categories by molecular processes and subcellular localizations, were adapted for the lens. Expression levels of both epithelial and fiber proteomes were compared with whole lens proteome and mRNA levels using E14.5, E16.5, E18.5, and P0.5 RNA-Seq data sets. During this developmental time window, multiple complex biosynthetic and catabolic processes generate the molecular and structural foundation for lens transparency. As expected, crystallins showed a high correlation between their mRNA and protein levels. Comprehensive data analysis confirmed and/or predicted roles for transcription factors (TFs), RNA-binding proteins (e.g. Carhsp1), translational apparatus including ribosomal heterogeneity and initiation factors, microtubules, cytoskeletal [e.g. non-muscle myosin IIA heavy chain (Myh9) and βB2-spectrin (Sptbn2)] and membrane proteins in lens formation and maturation. Our data highlighted many proteins with unknown functions in the lens that were preferentially enriched in epithelium or fibers, setting the stage for future studies to further dissect the roles of these proteins in fiber cell differentiation vs. epithelial cell maintenance. In conclusion, the present proteomic datasets represent the first mouse lens epithelium and fiber cell proteomes, establish comparative analyses of protein and RNA-Seq data, and characterize the major proteome remodeling required to form the mature lens fiber cells.
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Affiliation(s)
- Yilin Zhao
- Departments Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, NY, 10461, USA; Genetics, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Phillip A Wilmarth
- Department of Biochemistry & Molecular Biology, Oregon Health Sciences University, 3181 Southwest Sam Jackson Park Road, Portland, OR, 97239, USA
| | - Catherine Cheng
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Saima Limi
- Departments Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, NY, 10461, USA; Genetics, Albert Einstein College of Medicine, Bronx, NY, 10461, USA
| | - Velia M Fowler
- Department of Molecular Medicine, The Scripps Research Institute, La Jolla, CA, 92037, USA
| | - Deyou Zheng
- Genetics, Albert Einstein College of Medicine, Bronx, NY, 10461, USA; Neurology, Albert Einstein College of Medicine, Bronx, NY, 10461, USA; Neuroscience, Albert Einstein College of Medicine, Bronx, NY, 10461, USA; Department of Neurosurgery, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, 200120, China
| | - Larry L David
- Department of Biochemistry & Molecular Biology, Oregon Health Sciences University, 3181 Southwest Sam Jackson Park Road, Portland, OR, 97239, USA
| | - Ales Cvekl
- Departments Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, NY, 10461, USA; Genetics, Albert Einstein College of Medicine, Bronx, NY, 10461, USA.
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14
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D'Antin JC, Barraquer RI, Tresserra F, Michael R. Prevention of posterior capsule opacification through intracapsular hydrogen peroxide or distilled water treatment in human donor tissue. Sci Rep 2018; 8:12739. [PMID: 30143742 PMCID: PMC6109042 DOI: 10.1038/s41598-018-31178-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2018] [Accepted: 08/14/2018] [Indexed: 12/18/2022] Open
Abstract
In order to determine whether posterior capsule opacification after cataract surgery, could be delayed or inhibited through the application of hydrogen peroxide (H2O2) or distilled water (H2Od),we extracted lens capsules from 25 human donor eye globes. Samples were treated for 5 min with either 30 mM H2O2 or H2Od or used as controls, and cultured for one month, during which dark field and tilt illumination photos were taken. These were used to observe and quantify, time until cellular growth and confluence on the posterior capsule. After culture, histological sections were stained for H&E, α-SMA, Ki-67 and vimentin and evaluated. We prevented cellular growth in 50% of H2Od and 58% H2O2 of treated samples. The overall prevention of cell growth compared to cultured controls was significant for both treatments while there was no significant difference between them. In the cases where cellular growth was not prevented, both treatments significantly delay cellular growth. Until day 28 none of the treated samples of either type that had shown growth reached total confluence. All cultured controls reached total confluence before treated samples (median = day 11.5). Also, histologically, there was a clear morphological difference between cultured controls and treated samples.
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Affiliation(s)
- Justin Christopher D'Antin
- Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Barcelona, Spain.,Centro de Oftalmología Barraquer, Barcelona, Spain
| | - Rafael I Barraquer
- Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Barcelona, Spain. .,Centro de Oftalmología Barraquer, Barcelona, Spain. .,Universitat Internacional de Catalunya, Barcelona, Spain.
| | | | - Ralph Michael
- Institut Universitari Barraquer, Universitat Autònoma de Barcelona, Barcelona, Spain.,Centro de Oftalmología Barraquer, Barcelona, Spain
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15
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Quinlan RA, Schwarz N, Windoffer R, Richardson C, Hawkins T, Broussard JA, Green KJ, Leube RE. A rim-and-spoke hypothesis to explain the biomechanical roles for cytoplasmic intermediate filament networks. J Cell Sci 2018; 130:3437-3445. [PMID: 29032358 DOI: 10.1242/jcs.202168] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 08/02/2017] [Indexed: 12/17/2022] Open
Abstract
Textbook images of keratin intermediate filament (IF) networks in epithelial cells and the functional compromization of the epidermis by keratin mutations promulgate a mechanical role for this important cytoskeletal component. In stratified epithelia, keratin filaments form prominent radial spokes that are focused onto cell-cell contact sites, i.e. the desmosomes. In this Hypothesis, we draw attention to a subset of keratin filaments that are apposed to the plasma membrane. They form a rim of filaments interconnecting the desmosomes in a circumferential network. We hypothesize that they are part of a rim-and-spoke arrangement of IFs in epithelia. From our review of the literature, we extend this functional role for the subplasmalemmal rim of IFs to any cell, in which plasma membrane support is required, provided these filaments connect directly or indirectly to the plasma membrane. Furthermore, cytoplasmic IF networks physically link the outer nuclear and plasma membranes, but their participation in mechanotransduction processes remain largely unconsidered. Therefore, we also discuss the potential biomechanical and mechanosensory role(s) of the cytoplasmic IF network in terms of such a rim (i.e. subplasmalemmal)-and-spoke arrangement for cytoplasmic IF networks.
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Affiliation(s)
- Roy A Quinlan
- Department of Biosciences, University of Durham, Upper Mountjoy, Stockton Road, Durham DH1 3LE, UK .,Biophysical Sciences Institute, University of Durham, Upper Mountjoy, Stockton Road, Durham DH1 3LE, UK
| | - Nicole Schwarz
- RWTH Aachen University, Institute of Molecular and Cellular Anatomy, Wendlingweg 2, 52074 Aachen, Germany
| | - Reinhard Windoffer
- RWTH Aachen University, Institute of Molecular and Cellular Anatomy, Wendlingweg 2, 52074 Aachen, Germany
| | - Christine Richardson
- Department of Biosciences, University of Durham, Upper Mountjoy, Stockton Road, Durham DH1 3LE, UK
| | - Tim Hawkins
- Department of Biosciences, University of Durham, Upper Mountjoy, Stockton Road, Durham DH1 3LE, UK
| | - Joshua A Broussard
- Dept. of Pathology W127, Tarry Bldg, Room 3-735, Northwestern University, Feinberg School of Medicine, 303 E. Chicago Ave., Chicago, IL 60611, USA
| | - Kathleen J Green
- Dept. of Pathology W127, Tarry Bldg, Room 3-735, Northwestern University, Feinberg School of Medicine, 303 E. Chicago Ave., Chicago, IL 60611, USA
| | - Rudolf E Leube
- RWTH Aachen University, Institute of Molecular and Cellular Anatomy, Wendlingweg 2, 52074 Aachen, Germany
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16
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Chaves JM, Gupta R, Srivastava K, Srivastava O. Human alpha A-crystallin missing N-terminal domain poorly complexes with filensin and phakinin. Biochem Biophys Res Commun 2017; 494:402-8. [PMID: 28935373 DOI: 10.1016/j.bbrc.2017.09.088] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2017] [Accepted: 09/15/2017] [Indexed: 11/23/2022]
Abstract
The aim of this study was to determine relative importance of N-terminal domain and C-terminal extension of αA-crystallin during their in vitro complex formation with phakinin and filensin (the two lens-specific intermediate filament [IF] proteins). Cloned phakinin, filensin and vimentin were purified under a denaturing conditions by consecutive DEAE-cellulose-, hydroxyapatite- and Sephadex G-75-column chromatographic methods. WTαA-crystallin, αA-NT (N-terminal domain [residue number 1-63])-deleted and αA-CT (C-terminal terminal extension [residue number 140-173]-deleted), were cloned in pET 100 TOPO vector, expressed in BL-21 (DE3) cells using 1% IPTG, and purified using a Ni2+-affinity column. The following two in vitro methods were used to determine complex formation of WT-αA, αA-NT, or αA-CT with phakinin, filensin or both phakinin plus filensin together: an ultracentrifugation sedimentation (centrifugation at 80,000 × g for 30 min at 20 °C) followed by SDS-PAGE analysis, and an electron microscopic analysis. In the first method, the individual control proteins (WT-αA, αA-NT and αA-CT crystallin species) remained in the supernatant fractions whereas phakinin, filensin, and vimentin were recovered in the pellet fractions. On complex formation by individual WT-αA-, αA-NT or αA-CT-species with filensin, phakinin or both phakinin and filensin, WT-αA and αA-CT were recovered in the pellet fraction with phakinin, filensin or both filensin and phakinin, whereas αA-NT remained mostly in the supernatant, suggesting its poor complex formation property. EM-studies showed filamentous structure formation between WT-αA and αA-CT with phakinin or filensin, or with both filensin and phakinin together but relatively poor filamentous structures with αA-NT. Together, the results suggest that the N-terminal domain of αA-crystallin is required during in vitro complex formation with filensin and phakinin.
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17
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Cvekl A, Zhang X. Signaling and Gene Regulatory Networks in Mammalian Lens Development. Trends Genet 2017; 33:677-702. [PMID: 28867048 DOI: 10.1016/j.tig.2017.08.001] [Citation(s) in RCA: 111] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 07/27/2017] [Accepted: 08/01/2017] [Indexed: 11/16/2022]
Abstract
Ocular lens development represents an advantageous system in which to study regulatory mechanisms governing cell fate decisions, extracellular signaling, cell and tissue organization, and the underlying gene regulatory networks. Spatiotemporally regulated domains of BMP, FGF, and other signaling molecules in late gastrula-early neurula stage embryos generate the border region between the neural plate and non-neural ectoderm from which multiple cell types, including lens progenitor cells, emerge and undergo initial tissue formation. Extracellular signaling and DNA-binding transcription factors govern lens and optic cup morphogenesis. Pax6, c-Maf, Hsf4, Prox1, Sox1, and a few additional factors regulate the expression of the lens structural proteins, the crystallins. Extensive crosstalk between a diverse array of signaling pathways controls the complexity and order of lens morphogenetic processes and lens transparency.
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Affiliation(s)
- Ales Cvekl
- Departments of Genetics and Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Xin Zhang
- Departments of Ophthalmology, Pathology and Cell Biology, Columbia University Medical Center, New York, NY 10032, USA.
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18
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Cheng C, Nowak RB, Fowler VM. The lens actin filament cytoskeleton: Diverse structures for complex functions. Exp Eye Res 2016; 156:58-71. [PMID: 26971460 DOI: 10.1016/j.exer.2016.03.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2015] [Revised: 03/01/2016] [Accepted: 03/07/2016] [Indexed: 01/05/2023]
Abstract
The eye lens is a transparent and avascular organ in the front of the eye that is responsible for focusing light onto the retina in order to transmit a clear image. A monolayer of epithelial cells covers the anterior hemisphere of the lens, and the bulk of the lens is made up of elongated and differentiated fiber cells. Lens fiber cells are very long and thin cells that are supported by sophisticated cytoskeletal networks, including actin filaments at cell junctions and the spectrin-actin network of the membrane skeleton. In this review, we highlight the proteins that regulate diverse actin filament networks in the lens and discuss how these actin cytoskeletal structures assemble and function in epithelial and fiber cells. We then discuss methods that have been used to study actin in the lens and unanswered questions that can be addressed with novel techniques.
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Affiliation(s)
- Catherine Cheng
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Roberta B Nowak
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Velia M Fowler
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
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19
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Jarrin M, Young L, Wu W, Girkin JM, Quinlan RA. In vivo, Ex Vivo, and In Vitro Approaches to Study Intermediate Filaments in the Eye Lens. Methods Enzymol 2016; 568:581-611. [DOI: 10.1016/bs.mie.2015.09.010] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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20
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Abstract
The primary function of the lens resides in its transparency and ability to focus light on the retina. These require both that the lens cells contain high concentrations of densely packed lens crystallins to maintain a refractive index constant over distances approximating the wavelength of the light to be transmitted, and a specific arrangement of anterior epithelial cells and arcuate fiber cells lacking organelles in the nucleus to avoid blocking transmission of light. Because cells in the lens nucleus have shed their organelles, lens crystallins have to last for the lifetime of the organism, and are specifically adapted to this function. The lens crystallins comprise two major families: the βγ-crystallins are among the most stable proteins known and the α-crystallins, which have a chaperone-like function. Other proteins and metabolic activities of the lens are primarily organized to protect the crystallins from damage over time and to maintain homeostasis of the lens cells. Membrane protein channels maintain osmotic and ionic balance across the lens, while the lens cytoskeleton provides for the specific shape of the lens cells, especially the fiber cells of the nucleus. Perhaps most importantly, a large part of the metabolic activity in the lens is directed toward maintaining a reduced state, which shelters the lens crystallins and other cellular components from damage from UV light and oxidative stress. Finally, the energy requirements of the lens are met largely by glycolysis and the pentose phosphate pathway, perhaps in response to the avascular nature of the lens. Together, all these systems cooperate to maintain lens transparency over time.
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Affiliation(s)
- J Fielding Hejtmancik
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland, USA
| | - S Amer Riazuddin
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Rebecca McGreal
- Department of Genetics and Ophthalmology, Albert Einstein College of Medicine, Bronx, New York, USA; Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Wei Liu
- Department of Genetics and Ophthalmology, Albert Einstein College of Medicine, Bronx, New York, USA; Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Ales Cvekl
- Department of Genetics and Ophthalmology, Albert Einstein College of Medicine, Bronx, New York, USA; Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA
| | - Alan Shiels
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri, USA.
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21
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Nam TS, Kim JH, Chang CH, Yoon W, Jung YS, Kang SY, Shin BA, Perng MD, Choi SY, Kim MK. Identification of a novel nonsense mutation in the rod domain of GFAP that is associated with Alexander disease. Eur J Hum Genet 2015; 23:72-8. [PMID: 24755947 DOI: 10.1038/ejhg.2014.68] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Revised: 02/23/2014] [Accepted: 03/05/2014] [Indexed: 11/09/2022] Open
Abstract
Alexander disease (AxD) is an astrogliopathy that primarily affects the white matter of the central nervous system (CNS). AxD is caused by mutations in a gene encoding GFAP (glial fibrillary acidic protein). The GFAP mutations in AxD have been reported to act in a gain-of-function manner partly because the identified mutations generate practically full-length GFAP. We found a novel nonsense mutation (c.1000 G>T, p.(Glu312Ter); also termed p.(E312*)) within a rod domain of GFAP in a 67-year-old Korean man with a history of memory impairment and leukoencephalopathy. This mutation, GFAP p.(E312*), removes part of the 2B rod domain and the whole tail domain from the GFAP. We characterized GFAP p.(E312*) using western blotting, in vitro assembly and sedimentation assay, and transient transfection of human adrenal cortex carcinoma SW13 (Vim(+)) cells with plasmids encoding GFAP p.(E312*). The GFAP p.(E312*) protein, either alone or in combination with wild-type GFAP, elicited self-aggregation. In addition, the assembled GFAP p.(E312*) aggregated into paracrystal-like structures, and GFAP p.(E312*) elicited more GFAP aggregation than wild-type GFAP in the human adrenal cortex carcinoma SW13 (Vim(+)) cells. Our findings are the first report, to the best of our knowledge, on this novel nonsense mutation of GFAP that is associated with AxD and paracrystal formation.
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22
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Sugiyama Y, Shelley EJ, Wen L, Stump RJW, Shimono A, Lovicu FJ, McAvoy JW. Sfrp1 and Sfrp2 are not involved in Wnt/β-catenin signal silencing during lens induction but are required for maintenance of Wnt/β-catenin signaling in lens epithelial cells. Dev Biol 2013; 384:181-93. [PMID: 24140542 DOI: 10.1016/j.ydbio.2013.10.008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2013] [Revised: 10/03/2013] [Accepted: 10/07/2013] [Indexed: 02/07/2023]
Abstract
During eye lens development, regulation of Wnt/β-catenin signaling is critical for two major processes: initially it must be silent in the lens placode for lens development to proceed, but subsequently it is required for maintenance of the lens epithelium. It is not known how these different phases of Wnt/β-catenin activity/inactivity are regulated. Secreted frizzled related protein-2 (Sfrp2), a putative Wnt-Fz antagonist, is expressed in lens placode and in lens epithelial cells and has been put forward as a candidate for regional Wnt/β-catenin pathway regulation. Here we show its closely-related isoform, Sfrp1, has a complimentary pattern of expression in the lens, being absent from the placode and epithelium but expressed in the fibers. As mice with single knockouts of Sfrp1 or Sfrp2 had no defects in lens formation, we examined lenses of Sfrp1 and Sfrp2 double knockout (DKO) mice and showed that they formed lens placode and subsequent lens structures. Consistent with this we did not observe ectopic TCF/Lef activity in lens placode of DKOs. This indicates that Sfrp1 and Sfrp2 individually, or together, do not constitute the putative negative regulator that blocks Wnt/β-catenin signaling during lens induction. In contrast, Sfrp1 and Sfrp2 appear to have a positive regulatory function because Wnt/β-catenin signaling in lens epithelial cells was reduced in Sfrp1 and Sfrp2 DKO mice. Lenses that formed in DKO mice were smaller than controls and exhibited a deficient epithelium. Thus Sfrps play a role in lens development, at least in part, by regulating aspects of Wnt/β-catenin signaling in lens epithelial cells.
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Affiliation(s)
- Yuki Sugiyama
- Save Sight Institute, The University of Sydney, Australia
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23
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Abstract
Injury to lens epithelial cells (LECs) leads to epithelial–mesenchymal transition (EMT) with resultant fibrosis. The tropomyosin (Tpm) family of cytoskeleton proteins is involved in regulating and stabilizing actin microfilaments. Aberrant expression of Tpms leads to abnormal morphological changes with disintegration of epithelial integrity. The EMT of LECs has been proposed as a major cause of posterior capsule opacification (PCO) after cataract surgery. Using in vivo rodent PCO and human cataractous LECs, we demonstrated that the aberrant expression of rat Tpm and human Tpm1α/2β suggested their association in remodelling of the actin cytoskeleton during EMT of LECs. Expression analysis from abnormally growing LECs after lens extraction revealed elevated expression of α-smooth muscle actin (α-SMA), a marker for EMT. Importantly, these cells displayed increased expression of Tpm1α/2β following EMT/PCO formation. Expression of Tpm1α/2β was up-regulated in LECs isolated from cataractous lenses of Shumiya Cataract Rats (SCRs), compared with non-cataractous lenses. Also, LECs from human patients with nuclear cataract and anterior subcapsular fibrosis (ASF) displayed significantly increased expression of Tpm2β mRNA, suggesting that similar signalling invokes the expression of these molecules in LECs of cataractous SCR and human lenses. EMT was observed in LECs overexpressed with Tpm1α/2β, as evidenced by increased expression of α-SMA. These conditions were correlated with remodelling of actin filaments, possibly leading to EMT/PCO and ASF. The present findings may help clarify the condition of the actin cytoskeleton during morphogenetic EMT, and may contribute to development of Tpm-based inhibitors for postponing PCO and cataractogenesis.
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Affiliation(s)
- Eri Kubo
- Department of Ophthalmology, Kanazawa Medical University, Kahoku, Ishikawa, Japan.
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24
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Gokhin DS, Nowak RB, Kim NE, Arnett EE, Chen AC, Sah RL, Clark JI, Fowler VM. Tmod1 and CP49 synergize to control the fiber cell geometry, transparency, and mechanical stiffness of the mouse lens. PLoS One 2012; 7:e48734. [PMID: 23144950 PMCID: PMC3492431 DOI: 10.1371/journal.pone.0048734] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 09/28/2012] [Indexed: 11/25/2022] Open
Abstract
The basis for mammalian lens fiber cell organization, transparency, and biomechanical properties has contributions from two specialized cytoskeletal systems: the spectrin-actin membrane skeleton and beaded filament cytoskeleton. The spectrin-actin membrane skeleton predominantly consists of α2β2-spectrin strands interconnecting short, tropomyosin-coated actin filaments, which are stabilized by pointed-end capping by tropomodulin 1 (Tmod1) and structurally disrupted in the absence of Tmod1. The beaded filament cytoskeleton consists of the intermediate filament proteins CP49 and filensin, which require CP49 for assembly and contribute to lens transparency and biomechanics. To assess the simultaneous physiological contributions of these cytoskeletal networks and uncover potential functional synergy between them, we subjected lenses from mice lacking Tmod1, CP49, or both to a battery of structural and physiological assays to analyze fiber cell disorder, light scattering, and compressive biomechanical properties. Findings show that deletion of Tmod1 and/or CP49 increases lens fiber cell disorder and light scattering while impairing compressive load-bearing, with the double mutant exhibiting a distinct phenotype compared to either single mutant. Moreover, Tmod1 is in a protein complex with CP49 and filensin, indicating that the spectrin-actin network and beaded filament cytoskeleton are biochemically linked. These experiments reveal that the spectrin-actin membrane skeleton and beaded filament cytoskeleton establish a novel functional synergy critical for regulating lens fiber cell geometry, transparency, and mechanical stiffness.
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Affiliation(s)
- David S. Gokhin
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Roberta B. Nowak
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Nancy E. Kim
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
| | - Ernest E. Arnett
- Department of Biological Structure, University of Washington, Seattle, Washington, United States of America
| | - Albert C. Chen
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - Robert L. Sah
- Department of Bioengineering, University of California San Diego, La Jolla, California, United States of America
| | - John I. Clark
- Department of Biological Structure, University of Washington, Seattle, Washington, United States of America
| | - Velia M. Fowler
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California, United States of America
- * E-mail:
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25
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Abstract
γS-crystallin (γS) is a highly conserved component of the eye lens. To gain insights into the functional role(s) of this protein, the mouse gene (Crygs) was deleted. Although mutations in γS can cause severe cataracts, loss of function of γS in knockout (KO) mice produced no obvious lens opacity, but was associated with focusing defects. Electron microscopy showed no major differences in lens cell organization, suggesting that the optical defects are primarily cytoplasmic in origin. KO lenses were also grossly normal by light microscopy but showed evidence of incomplete clearance of cellular organelles in maturing fiber cells. Phalloidin labeling showed an unusual distribution of F-actin in a band of mature fiber cells in KO lenses, suggesting a defect in the organization or processing of the actin cytoskeleton. Indeed, in wild-type lenses, γS and F-actin colocalize along the fiber cell plasma membrane. Relative levels of F-actin and G-actin in wild-type and KO lenses were estimated from fluorescent staining profiles and from isolation of actin fractions from whole lenses. Both methods showed a two-fold reduction in the F-actin/G-actin ratio in KO lenses, whereas no difference in tubulin organization was detected. In vitro experiments showed that recombinant mouse γS can directly stabilize F-actin. This suggests that γS may have a functional role related to actin, perhaps in 'shepherding' filaments to maintain the optical properties of the lens cytoplasm and normal fiber cell maturation.
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Affiliation(s)
- Jianguo Fan
- Section on Molecular Structure and Functional Genomics, National Eye Institute, National Institutes of Health, Bethesda, MD 20892-0608, USA
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26
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Costello MJ, Burette A, Weber M, Metlapally S, Gilliland KO, Fowler WC, Mohamed A, Johnsen S. Electron tomography of fiber cell cytoplasm and dense cores of multilamellar bodies from human age-related nuclear cataracts. Exp Eye Res 2012; 101:72-81. [PMID: 22728317 DOI: 10.1016/j.exer.2012.06.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Revised: 06/09/2012] [Accepted: 06/11/2012] [Indexed: 01/29/2023]
Abstract
Human nuclear cataract formation is a multi-factorial disease with contributions to light scattering from many cellular sources that change their scattering properties over decades. The aging process produces aggregation of cytoplasmic crystallin proteins, which alters the protein packing and texture of the cytoplasm. Previous studies of the cytoplasmic texture quantified increases in density fluctuations in protein packing and theoretically predicted the corresponding scattering. Multilamellar bodies (MLBs) are large particles with a core of crystallin cytoplasm that have been suggested to be major sources of scattering in human nuclei. The core has been shown to condense over time such that the refractive index increases compared to the adjacent aged and textured cytoplasm. Electron tomography is used here to visualize the 3D arrangement of protein aggregates in aged and cataractous lens nuclear cytoplasm compared to the dense protein packing in the cores of MLBs. Thin sections, 70 nm thick, were prepared from epoxy-embedded human transparent donor lenses and nuclear cataracts. Tilt series were collected on an FEI T20 transmission electron microscope (TEM) operated at 200 kV using 15 nm gold particles as fiducial markers. Images were aligned and corrected with FEI software and reconstructed with IMOD and other software packages to produce animated tilt series and stereo anaglyphs. The 3D views of protein density showed the relatively uniform packing of proteins in aged transparent lens nuclear cytoplasm and less dense packing of aged cataractous cytoplasm where many low-density regions can be appreciated in the absence of the TEM projection artifacts. In contrast the cores of the MLBs showed a dense packing of protein with minimal density fluctuations. These observations support the conclusion that, during the nuclear cataract formation, alterations in protein packing are extensive and can result in pronounced density fluctuations. Aging causes the MLB cores to become increasingly different in their protein packing from the adjacent cytoplasm. These results support the hypothesis that the MLBs increase their scattering with age and nuclear cataract formation.
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Affiliation(s)
- M Joseph Costello
- Department of Cell and Developmental Biology, CB 7090, University of North Carolina, Chapel Hill, NC 27599, USA.
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27
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Yamashiro S, Gokhin DS, Kimura S, Nowak RB, Fowler VM. Tropomodulins: pointed-end capping proteins that regulate actin filament architecture in diverse cell types. Cytoskeleton (Hoboken) 2012; 69:337-70. [PMID: 22488942 DOI: 10.1002/cm.21031] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2011] [Revised: 03/23/2012] [Accepted: 03/26/2012] [Indexed: 01/31/2023]
Abstract
Tropomodulins are a family of four proteins (Tmods 1-4) that cap the pointed ends of actin filaments in actin cytoskeletal structures in a developmentally regulated and tissue-specific manner. Unique among capping proteins, Tmods also bind tropomyosins (TMs), which greatly enhance the actin filament pointed-end capping activity of Tmods. Tmods are defined by a TM-regulated/Pointed-End Actin Capping (TM-Cap) domain in their unstructured N-terminal portion, followed by a compact, folded Leucine-Rich Repeat/Pointed-End Actin Capping (LRR-Cap) domain. By inhibiting actin monomer association and dissociation from pointed ends, Tmods regulate actin dynamics and turnover, stabilizing actin filament lengths and cytoskeletal architecture. In this review, we summarize the genes, structural features, molecular and biochemical properties, actin regulatory mechanisms, expression patterns, and cell and tissue functions of Tmods. By understanding Tmods' functions in the context of their molecular structure, actin regulation, binding partners, and related variants (leiomodins 1-3), we can draw broad conclusions that can explain the diverse morphological and functional phenotypes that arise from Tmod perturbation experiments in vitro and in vivo. Tmod-based stabilization and organization of intracellular actin filament networks provide key insights into how the emergent properties of the actin cytoskeleton drive tissue morphogenesis and physiology.
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Affiliation(s)
- Sawako Yamashiro
- Department of Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA
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28
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Qu B, Landsbury A, Schönthaler HB, Dahm R, Liu Y, Clark JI, Prescott AR, Quinlan RA. Evolution of the vertebrate beaded filament protein, Bfsp2; comparing the in vitro assembly properties of a "tailed" zebrafish Bfsp2 to its "tailless" human orthologue. Exp Eye Res 2011; 94:192-202. [PMID: 22182672 DOI: 10.1016/j.exer.2011.12.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2011] [Revised: 11/30/2011] [Accepted: 12/02/2011] [Indexed: 11/25/2022]
Abstract
In bony fishes, Bfsp2 orthologues are predicted to possess a C-terminal tail domain, which is absent from avian, amphibian and mammalian Bfsp2 sequences. These sequences, are however, not conserved between fish species and therefore questions whether they have a functional role. For other intermediate filament proteins, the C-terminal tail domain is important for both filament assembly and regulating interactions between filaments. We confirm that zebrafish has a single Bfsp2 gene by radiation mapping. Two transcripts (bfsp2α and bfsp2β) are produced by alternative splicing of the last exon. Using a polyclonal antibody specific to a tridecameric peptide in the C-terminal tail domain common to both zebrafish Bfsp2 splice variants, we have confirmed its expression in zebrafish lens fibre cells. We have also determined the in vitro assembly properties of zebrafish Bfsp2α and conclude that the C-terminal sequences are required to regulate not only the diameter and uniformity of the in vitro assembly filaments, but also their filament-filament associations in vitro. Therefore we conclude zebrafish Bfsp2α is a functional orthologue conforming more closely to the conventional domain structure of intermediate filament proteins. Data mining of the genome databases suggest that the loss of this tail domain could occur in several stages leading eventually to completely tailless orthologues, such as human BFSP2.
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29
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Chen YS, Lim SC, Chen MH, Quinlan RA, Perng MD. Alexander disease causing mutations in the C-terminal domain of GFAP are deleterious both to assembly and network formation with the potential to both activate caspase 3 and decrease cell viability. Exp Cell Res 2011; 317:2252-66. [PMID: 21756903 DOI: 10.1016/j.yexcr.2011.06.017] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Revised: 06/23/2011] [Accepted: 06/27/2011] [Indexed: 12/12/2022]
Abstract
Alexander disease is a primary genetic disorder of astrocyte caused by dominant mutations in the astrocyte-specific intermediate filament glial fibrillary acidic protein (GFAP). While most of the disease-causing mutations described to date have been found in the conserved α-helical rod domain, some mutations are found in the C-terminal non-α-helical tail domain. Here, we compare five different mutations (N386I, S393I, S398F, S398Y and D417M14X) located in the C-terminal domain of GFAP on filament assembly properties in vitro and in transiently transfected cultured cells. All the mutations disrupted in vitro filament assembly. The mutations also affected the solubility and promoted filament aggregation of GFAP in transiently transfected MCF7, SW13 and U343MG cells. This correlated with the activation of the p38 stress-activated protein kinase and an increased association with the small heat shock protein (sHSP) chaperone, αB-crystallin. Of the mutants studied, D417M14X GFAP caused the most significant effects both upon filament assembly in vitro and in transiently transfected cells. This mutant also caused extensive filament aggregation coinciding with the sequestration of αB-crystallin and HSP27 as well as inhibition of the proteosome and activation of p38 kinase. Associated with these changes were an activation of caspase 3 and a significant decrease in astrocyte viability. We conclude that some mutations in the C-terminus of GFAP correlate with caspase 3 cleavage and the loss of cell viability, suggesting that these could be contributory factors in the development of Alexander disease.
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Affiliation(s)
- Yi-Song Chen
- Institute of Molecular Medicine, College of Life Sciences, National Tsing Hua University, Hsinchu 300, Taiwan
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30
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Su SP, McArthur JD, Truscott RJW, Aquilina JA. Truncation, cross-linking and interaction of crystallins and intermediate filament proteins in the aging human lens. Biochim Biophys Acta 2011; 1814:647-56. [PMID: 21447408 DOI: 10.1016/j.bbapap.2011.03.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/05/2010] [Revised: 02/14/2011] [Accepted: 03/22/2011] [Indexed: 11/30/2022]
Abstract
The optical properties of the lens are dependent upon the integrity of proteins within the fiber cells. During aging, crystallins, the major intra-cellular structural proteins of the lens, aggregate and become water-insoluble. Modifications to crystallins and the lens intermediate filaments have been implicated in this phenomenon. In this study, we examined changes to, and interactions between, human lens crystallins and intermediate filament proteins in lenses from a variety of age groups (0-86years). Among the lens-specific intermediate filament proteins, filensin was extensively cleaved in all postnatal lenses, with truncated products of various sizes being found in both the lens cortical and nuclear extracts. Phakinin was also truncated and was not detected in the lens nucleus. The third major intermediate filament protein, vimentin, remained intact in lens cortical fiber cells across the age range except for an 86year lens, where a single ~49kDa breakdown product was observed. An αB-crystallin fusion protein (maltose-binding protein-αB-crystallin) was found to readily exchange subunits with endogenous α-crystallin, and following mild heat stress, to bind to filensin, phakinin and vimentin and to several of their truncated products. Tryptic digestion of a truncated form of filensin suggested that the binding site for α-crystallin may be in the N-terminal region. The presence of significant amounts of small peptides derived from γS- and βB1-crystallins in the water-insoluble fraction of the lens indicates that these interact tightly with cytoskeletal or membrane components. Interestingly, water-soluble complexes (~40kDa) contained predominantly γS- and βB1-crystallins, suggesting that cross-linking is an alternative pathway for modified β- and γ-crystallins in the lens.
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Affiliation(s)
- Shih-Ping Su
- School of Biological Sciences, University of Wollongong, Wollongong, NSW 2522, Australia.
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31
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Al-Ghoul KJ, Lindquist TP, Kirk SS, Donohue ST. A novel terminal web-like structure in cortical lens fibers: architecture and functional assessment. Anat Rec (Hoboken) 2011; 293:1805-15. [PMID: 20730867 DOI: 10.1002/ar.21216] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
This study describes a novel cytoskeletal array in fiber cells of the ocular lens of the rat and shows its relationship to the classical terminal web of other epithelial tissues. Naive adult Sprague-Dawley rats (n = 28) were utilized. F-actin, fodrin, myosin IIA, and CP49 distribution was assessed in anterior and posterior polar sections. For functional analysis, lenses were cultured with or without cytochalasin-D for 3 hr, then processed for confocal microscopy or assessed by laser scan analysis along sutures. Phalloidin labeling demonstrated a dense mesh of F-actin adjacent to posterior sutural domains to a subcapsular depth of 400 μm. Anterior polar sections revealed a comparable actin structure adjacent to anterior suture branches however, it was not developed in superficial fibers. Fodrin and myosin were localized within the web-like actin apparatus. The data was used to construct a model showing that the cytoskeletal array is located within the blunt, variable-width fiber ends that abut at sutures such that the "terminal web" flanks the suture on either side. Treatment with cytochalasin-D resulted in partial disassembly of the "terminal web" and perturbed cellular organization. Laser scan analysis revealed that cytochalasin-D treated lenses had significantly greater focal variability than control lenses (P = 0.020). We conclude that cortical fibers of rat lenses contain a bipolar structure that is structurally and compositionally analogous to classical terminal webs. The results indicate that the lens "terminal web" functions to stabilize lens fiber ends at sutures thus minimizing structural disorder, which in turn, promotes the establishment and maintenance of lens transparency.
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Affiliation(s)
- Kristin J Al-Ghoul
- Department of Anatomy and Cell Biology, Rush University Medical Center, Chicago, Illinois, USA.
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32
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Abstract
PURPOSE To investigate proteomic profiles of normal human lenses and their key proteins in protein-protein interactions (PPIs). MATERIALS AND METHODS Water-soluble and water-insoluble proteins extracted from human lenses were first separated by one-dimensional sodium dodecyl sulfate polyacrylamide gel, and then in-gel digested with trypsin into peptides eluted by reversed-phase high-performance liquid chromatography. The eluted peptides were analyzed by linear ion trap tandem mass spectrometry (MS/MS). The raw data was filtered by TurboSEQUEST algorithm. The reverse database was used for peptide false-positive rate estimation. A network chart was constructed by the identified lens PPIs in accordance with interaction database systems. RESULTS From normal human lenses 339 proteins in total were identified, including many formerly unidentified low-abundance proteins. Key proteins we recognized included plectin, actin, spectrin (alpha, beta), vimentin, 14-3-3 protein (beta/alpha, zeta/delta, epsilon, gamma, eta), TSC2, guanine nucleotide-releasing protein, laminin gamma, mitogen-activated protein kinase, alpha-A-crystallin, heat-shock protein (alpha, beta), glyceraldehyde 3-phosphate dehydrogenase, and collagen IV alpha. CONCLUSIONS Key proteins of normal human lenses were studied by constructing a network chart of the identified lens PPIs. The results suggest that linear ion trap MS/MS is an effective tool for detecting low-abundance proteins of human lenses. This study provides valuable data for further proteomic research of the human lens development and lens diseases.
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Affiliation(s)
- Zhibin Yao
- Department of Ophthalmology, Fourth Affiliated Hospital, China Medical University, Shenyang, China
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33
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Yang C, Yang Y, Brennan L, Bouhassira EE, Kantorow M, Cvekl A. Efficient generation of lens progenitor cells and lentoid bodies from human embryonic stem cells in chemically defined conditions. FASEB J 2010; 24:3274-83. [PMID: 20410439 DOI: 10.1096/fj.10-157255] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
The eye lens is an encapsulated avascular organ whose function is to focus light on the retina. Lens comprises a single progenitor cell lineage in multiple states of differentiation. Disruption of lens function leading to protein aggregation and opacity results in age-onset cataract. Cataract is a complex disease involving genetic and environmental factors. Here, we report the development of a new 3-stage system that differentiates human embryonic stem cells (hESCs) into large quantities of lens progenitor-like cells and differentiated 3-dimensional lentoid bodies. Inhibition of BMP signaling by noggin triggered differentiation of hESCs toward neuroectoderm. Subsequent reactivation of BMP and activation of FGF signaling stimulated formation of lens progenitor cells marked by the expression of PAX6 and alpha-crystallins. The formation of lentoid bodies was most efficient in the presence of FGF2 and Wnt-3a, yielding approximately 1000 lentoid bodies/30-mm well. Lentoid bodies expressed and accumulated lens-specific markers including alphaA-, alphaB-, beta-, and gamma-crystallins, filensin, CP49, and MIP/aquaporin 0. Collectively, these studies identify a novel procedure to generate lens cells from hESCs that can be applied for studies of lens differentiation and cataractogenesis using induced pluripotent stem (iPS) cells derived from various cataract patients.
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Affiliation(s)
- Chunbo Yang
- Department of Ophthalmology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
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34
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Sugiyama Y, Akimoto K, Robinson ML, Ohno S, Quinlan RA. A cell polarity protein aPKClambda is required for eye lens formation and growth. Dev Biol 2009; 336:246-56. [PMID: 19835853 PMCID: PMC2806522 DOI: 10.1016/j.ydbio.2009.10.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2009] [Revised: 10/03/2009] [Accepted: 10/05/2009] [Indexed: 11/28/2022]
Abstract
The organisation of individual cells into a functional three-dimensional tissue is still a major question in developmental biology. Modulation of epithelial cell shape is a critical driving force in forming tissues. This is well illustrated in the eye lens where epithelial cells elongate extensively during their differentiation into fibre cells. It is at the lens equator that epithelial cells elongate along their apical–basal axis. During this process the elongating epithelial cells and their earliest fibre cell derivatives remain anchored at their apical tips, forming a discrete region or modiolus, which we term the lens fulcrum. How this is achieved has received scant attention and is little understood. Here, we show that conditional depletion of aPKCλ, a central effector of the PAR polarity complex, disrupts the apical junctions in elongating epithelial cells so that the lens fulcrum fails to form. This results in disorganised fibre cell alignment that then causes cataract. Interestingly, aPKCλ depletion also promotes epithelial–mesenchymal transition of the lens epithelial cells, reducing their proliferation, leading ultimately to a small lens and microphthalmia. These observations indicate that aPKCλ, a regulator of polarity and apical junctions, is required for development of a lens that is the correct size and shape.
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Affiliation(s)
- Yuki Sugiyama
- School of Biological and Biomedical Sciences, University of Durham, Durham, UK
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35
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Song S, Landsbury A, Dahm R, Liu Y, Zhang Q, Quinlan RA. Functions of the intermediate filament cytoskeleton in the eye lens. J Clin Invest 2009; 119:1837-48. [PMID: 19587458 DOI: 10.1172/jci38277] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Intermediate filaments (IFs) are a key component of the cytoskeleton in virtually all vertebrate cells, including those of the lens of the eye. IFs help integrate individual cells into their respective tissues. This Review focuses on the lens-specific IF proteins beaded filament structural proteins 1 and 2 (BFSP1 and BFSP2) and their role in lens physiology and disease. Evidence generated in studies in both mice and humans suggests a critical role for these proteins and their filamentous polymers in establishing the optical properties of the eye lens and in maintaining its transparency. For instance, mutations in both BFSP1 and BFSP2 cause cataract in humans. We also explore the potential role of BFSP1 and BFSP2 in aging processes in the lens.
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Affiliation(s)
- Shuhua Song
- Center for Ophthalmic Research/Surgery, Brigham and Women's Hospital, and Department of Ophthalmology, Harvard Medical School, Boston, Massachusetts, USA
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36
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De Maria A, Shi Y, Kumar NM, Bassnett S. Calpain expression and activity during lens fiber cell differentiation. J Biol Chem 2009; 284:13542-13550. [PMID: 19269960 PMCID: PMC2679455 DOI: 10.1074/jbc.m900561200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2009] [Revised: 03/05/2009] [Indexed: 12/28/2022] Open
Abstract
In animal models, the dysregulated activity of calcium-activated proteases, calpains, contributes directly to cataract formation. However, the physiological role of calpains in the healthy lens is not well defined. In this study, we examined the expression pattern of calpains in the mouse lens. Real time PCR and Western blotting data indicated that calpain 1, 2, 3, and 7 were expressed in lens fiber cells. Using controlled lysis, depth-dependent expression profiles for each calpain were obtained. These indicated that, unlike calpain 1, 2, and 7, which were most abundant in cells near the lens surface, calpain 3 expression was strongest in the deep cortical region of the lens. We detected calpain activities in vitro and showed that calpains were active in vivo by microinjecting fluorogenic calpain substrates into cortical fiber cells. To identify endogenous calpain substrates, membrane/cytoskeleton preparations were treated with recombinant calpain, and cleaved products were identified by two-dimensional difference electrophoresis/mass spectrometry. Among the calpain substrates identified by this approach was alphaII-spectrin. An antibody that specifically recognized calpain-cleaved spectrin was used to demonstrate that spectrin is cleaved in vivo, late in fiber cell differentiation, at or about the time that lens organelles are degraded. The generation of the calpain-specific spectrin cleavage product was not observed in lens tissue from calpain 3-null mice, indicating that calpain 3 is uniquely activated during lens fiber differentiation. Our data suggest a role for calpains in the remodeling of the membrane cytoskeleton that occurs with fiber cell maturation.
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Affiliation(s)
- Alicia De Maria
- Department of Ophthalmology and Visual Sciences, Washington University, St. Louis, Missouri 63110
| | - Yanrong Shi
- Department of Ophthalmology and Visual Sciences, Washington University, St. Louis, Missouri 63110
| | - Nalin M Kumar
- Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, Illinois 60612
| | - Steven Bassnett
- Department of Ophthalmology and Visual Sciences, Washington University, St. Louis, Missouri 63110.
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37
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Schietroma C, Fain N, Zampighi LM, Lanzavecchia S, Zampighi GA. The structure of the cytoplasm of lens fibers as determined by conical tomography. Exp Eye Res 2009; 88:566-74. [PMID: 19103200 DOI: 10.1016/j.exer.2008.11.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Revised: 11/12/2008] [Accepted: 11/12/2008] [Indexed: 11/21/2022]
Abstract
Studies using conventional electron microscopy describe the cytoplasm of lens fiber cells as having essentially an amorphous structure. We hypothesized that significant structural detail might have been lost as a result of projecting the entire thickness of the section (50-100 nm) onto a single plane (the "projection artifact"). To test this hypothesis, we studied the 3D-structure of rat lens cortical fibers before and after extracting the "soluble" crystallins with low ionic strength buffers to make "ghosts." Tomographic series in conical geometry were collected at 55 degrees tilts and by 5 degrees rotations until completing a 360 degrees turn by low dose methods. They were aligned using fiduciary points, reconstructed with the weighted back projection algorithm and refined by projection matching. Analysis of the 3D-maps included semiautomatic density segmentation using a computer program based on the watershed algorithm. We found that the cytoplasm of cortical fibers, though appearing amorphous in regions of the highest density, was in fact comprised of an ordered structure resembling a "clustered matrix." The matrix was comprised of thin ( approximately 6 nm diameter) filaments bent sharply at 110-120 degrees angles and studded with cube-shaped particles (the "beaded" filaments). In cortical fibers, the particles measured a=14+/-2, b=13+/-2 and c=10+/-2.4 nm (n=30, mean+/-SD) and were spaced at distances measuring 27.5+/-2.4 nm apart (n=8, mean+/-SD), center-to-center. The matrix was formed as "beaded" filaments, bound to clusters of "soluble" proteins, crossed each other at nearly perpendicular angles. The matrix also made contact with the plasma membrane at a large number of distinct regions. We thus concluded that the cytoplasm of cortical lens fibers is comprised of a cytoskeletal matrix of "beaded" filaments that organize the "soluble" crystallins in separate regions. The association of this matrix with the plasma membrane allows the lens to maintain its structural integrity, while its association with crystallins yields its long-term transparency. Loss of either function likely would play a significant role in cataract formation.
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Abstract
The ocular lens assembles two separate intermediate filament systems sequentially with differentiation. Canonical 8-11 nm IFs composed of Vimentin are assembled in lens epithelial cells and younger fiber cells, while the fiber cell-specific beaded filaments are switched on as fiber cell elongation initiates. Some of the key features of both filament systems are reviewed.
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Bornheim R, Müller M, Reuter U, Herrmann H, Büssow H, Magin TM. A dominant vimentin mutant upregulates Hsp70 and the activity of the ubiquitin-proteasome system, and causes posterior cataracts in transgenic mice. J Cell Sci 2008; 121:3737-46. [PMID: 18940912 DOI: 10.1242/jcs.030312] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Vimentin is the main intermediate filament (IF) protein of mesenchymal cells and tissues. Unlike other IF-/- mice, vimentin-/- mice provided no evidence of an involvement of vimentin in the development of a specific disease. Therefore, we generated two transgenic mouse lines, one with a (R113C) point mutation in the IF-consensus motif in coil1A and one with the complete deletion of coil 2B of the rod domain. In epidermal keratins and desmin, point mutations in these parts of the alpha-helical rod domain cause keratinopathies and desminopathies, respectively. Here, we demonstrate that substoichiometric amounts of vimentin carrying the R113C point mutation disrupted the endogenous vimentin network in all tissues examined but caused a disease phenotype only in the eye lens, leading to a posterior cataract that was paralleled by the formation of extensive protein aggregates in lens fibre cells. Unexpectedly, central, postmitotic fibres became depleted of aggregates, indicating that they were actively removed. In line with an increase in misfolded proteins, the amounts of Hsp70 and ubiquitylated vimentin were increased, and proteasome activity was raised. We demonstrate here for the first time that the expression of mutated vimentin induces a protein-stress response that contributes to disease pathology in mice, and hypothesise that vimentin mutations cause cataracts in humans.
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Affiliation(s)
- Roland Bornheim
- Institut für Biochemie and Molekularbiologie, Abteilung für Zellbiochemie und LIMES, Universität Bonn, Nussallee 11, 53115 Bonn, Germany
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40
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Leonard M, Chan Y, Menko AS. Identification of a novel intermediate filament-linked N-cadherin/gamma-catenin complex involved in the establishment of the cytoarchitecture of differentiated lens fiber cells. Dev Biol 2008; 319:298-308. [PMID: 18514185 PMCID: PMC2518943 DOI: 10.1016/j.ydbio.2008.04.036] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2007] [Revised: 04/14/2008] [Accepted: 04/18/2008] [Indexed: 10/22/2022]
Abstract
Tissue morphogenesis and maintenance of complex tissue architecture requires a variety of cell-cell junctions. Typically, cells adhere to one another through cadherin junctions, both adherens and desmosomal junctions, strengthened by association with cytoskeletal networks during development. Both beta- and gamma-catenins are reported to link classical cadherins to the actin cytoskeleton, but only gamma-catenin binds to the desmosomal cadherins, which links them to intermediate filaments through its association with desmoplakin. Here we provide the first biochemical evidence that, in vivo, gamma-catenin also mediates interactions between classical cadherins and the intermediate filament cytoskeleton, linked through desmoplakin. In the developing lens, which has no desmosomes, we discovered that vimentin became linked to N-cadherin complexes in a differentiation-state specific manner. This newly identified junctional complex was tissue specific but not unique to the lens. To determine whether in this junction N-cadherin was linked to vimentin through gamma-catenin or beta-catenin we developed an innovative "double" immunoprecipitation technique. This approach made possible, for the first time, the separation of N-cadherin/gamma-catenin from N-cadherin/beta-catenin complexes and the identification of multiple members of each of these isolated protein complexes. The study revealed that vimentin was associated exclusively with N-cadherin/gamma-catenin junctions. Assembly of this novel class of cadherin junctions was coincident with establishment of the unique cytoarchitecture of lens fiber cells. In addition, gamma-catenin had a distinctive localization to the vertices of these hexagonally shaped differentiating lens fiber cells, a region devoid of actin; while beta-catenin co-localized with actin at lateral cell interfaces. We believe this novel vimentin-linked N-cadherin/gamma-catenin junction provides the tensile strength necessary to establish and maintain structural integrity in tissues that lack desmosomes.
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Affiliation(s)
- Michelle Leonard
- Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, 571 Jefferson Alumni Hall, 1020 Locust Street, Philadelphia, PA 19107, USA
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41
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Abstract
The combination of laser capture microdissection and mass spectrometry represents a powerful technology for studying spatially resolved proteomes. Moreover, the compositions of integral membrane proteomes have rarely been studied in a spatially resolved manner. In this study, ocular lens tissue was carefully dissected by laser capture microdissection and conditions for membrane protein enrichment, trypsin digestion, and mass spectrometry analysis were optimized. Proteomic analysis allowed the identification of 170 proteins, 136 of which were identified with more than one peptide match. Spatial differences in protein expression were observed between cortical and nuclear samples. In addition, the spatial distribution of post-translational modifications to lens membrane proteins, such as the lens major intrinsic protein AQP0, were investigated and regional differences were measured for AQP0 C-terminal phosphorylation and truncation.
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Affiliation(s)
- Zhen Wang
- Medical University of South Carolina, Charleston, SC 29425
| | - Jun Han
- Medical University of South Carolina, Charleston, SC 29425
| | - Kevin L Schey
- Medical University of South Carolina, Charleston, SC 29425
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42
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Vasavada A, Johar K, Praveen M, Nishi O. Confirmation of the presence of lens epithelial cells in the anterior chamber after phacoemulsification. Eye (Lond) 2009; 23:1170-5. [DOI: 10.1038/eye.2008.182] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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43
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Harding RL, Howley S, Baker LJ, Murphy TR, Archer WE, Wistow G, Hyde DR, Vihtelic TS. Lengsin expression and function during zebrafish lens formation. Exp Eye Res 2008; 86:807-18. [PMID: 18406404 DOI: 10.1016/j.exer.2008.02.009] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2007] [Revised: 02/13/2008] [Accepted: 02/22/2008] [Indexed: 11/15/2022]
Abstract
A zebrafish ortholog of human lengsin was identified by EST analysis of an adult lens cDNA library. During zebrafish development, lengsin transcription is first detected at 24 h post-fertilization (hpf). Immunolocalization, using polyclonal antiserum generated against a Lengsin bacterial fusion protein, detects lens-specific protein in whole-mount embryos at 30 hpf. Lengsin expression in zebrafish follows the temporal expression of the alphaA- alphaB1- and betaB1-crystallin proteins in the lens. At 72 hpf, Lengsin is localized to a subpopulation of differentiating secondary fiber cells, while no expression is detected in the lens epithelial cells or central lens fibers. In the adult lens, Lengsin is restricted to a narrow band of cortical fibers and co-localizes with actin at the lateral faces of these interdigitating cells. Stable transgenic lines, using a 3 kb lengsin genomic fragment to regulate EGFP expression, recapitulate the Lengsin temporal and spatial expression patterns. Lengsin function in zebrafish lens formation was examined by antisense morpholino-mediated translation and mRNA splice inhibition. At 72 hpf, the lengsin morphant lenses are reduced in size and exhibit separations within the cortex due to defects in secondary fiber morphogenesis. The location of the morphant lens defects correlates with the Lengsin protein localization at this age. These results demonstrate Lengsin is required for proper fiber cell differentiation by playing roles in either cell elongation or the establishment of cell interactions.
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Affiliation(s)
- Rachel L Harding
- University of Notre Dame, Department of Biological Sciences and Center for Zebrafish Research, Galvin Life Science Center, Notre Dame, IN 46556-0369, USA
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44
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Wyatt K, Gao C, Tsai JY, Fariss RN, Ray S, Wistow G. A role for lengsin, a recruited enzyme, in terminal differentiation in the vertebrate lens. J Biol Chem 2008; 283:6607-15. [PMID: 18178558 DOI: 10.1074/jbc.m709144200] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lengsin is an eye lens-specific member of the glutamine synthetase (GS) superfamily. Lengsin has no GS activity, suggesting that it has a structural rather than catalytic role in lens. In situ hybridization and immunofluorescence showed that lengsin is expressed in terminally differentiating secondary lens fiber cells. Yeast two-hybrid (Y2H) and recombinant protein experiments showed that full-length lengsin can bind the 2B filament region of vimentin. In affinity chromatography, lengsin also bound the equivalent region of CP49 (BFSP2; phakinin), a related intermediate filament protein specific to the lens. Both the vimentin and CP49 2B fragments bound lengsin in surface plasmon resonance spectroscopy with fast association and slow dissociation kinetics. Lengsin expression correlates with a transition zone in maturing lens fiber cells in which cytoskeleton is reorganized. Lengsin and lens intermediate filament proteins co-localize at the plasma membrane in maturing fiber cells. This suggests that lengsin may act as a component of the cytoskeleton itself or as a chaperone for the reorganization of intermediate filament proteins during terminal differentiation in the lens.
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Affiliation(s)
- Keith Wyatt
- National Eye Institute, National Institutes of Health, Bethesda, MD 20892, USA
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45
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Abstract
The transparent properties of the lens and its ability to focus light onto the retina are critical for normal vision. Optical clarity of the lens is achieved and maintained by a unique, highly regulated integration of lens cell proliferation and differentiation that persists throughout life. Zebrafish is a powerful genetic model for studying vertebrate lens differentiation and growth because the structural organization of the lens and gene functions are largely conserved with mammals, including humans. However, some features of zebrafish lens developmental morphology and gene expression are different from those of mammals and other terrestrial vertebrates. For example, the presumptive zebrafish lens delaminates from the surface ectoderm to form a solid mass of cells, in which the primary fibers differentiate by elongating in circular fashion. Both mutational and candidate gene analyses have identified and characterized developmental gene functions of the lens in zebrafish. This chapter presents the recent morphological analysis of zebrafish lens formation. In addition, the roles of Pitx3, Foxe3, and the lens-specific protein Lengsin (LENS Glutamine SYNthetase-like) in lens development are analyzed. Selected zebrafish lens mutants defective in early developmental processes and the maintenance of lens transparency are also discussed.
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Affiliation(s)
- Thomas S Vihtelic
- Department of Biological Sciences and Center for Zebrafish Research, Galvin Life Sciences Center, University of Notre Dame, Notre Dame, Indiana 46556, USA
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46
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Abstract
Filensin (BFSP1) and CP49 (BFSP2) represent two members of the IF protein superfamily that are thus far exclusively expressed in the eye lens. Mutations in both proteins cause lens cataract and careful consideration of the detail of these cataract phenotypes alerts us to several interesting features concerning the function of filensin (BFSP1) and CP49 (BFSP2) in the lens. With the first filensin (BFSP1) mutation now having been reported to cause a recessive cataract phenotype, there is the suggestion that the mutation could predispose heterozygote carriers to the early onset of age-related nuclear cataract. In the case of CP49 (BFSP2), there are now three unrelated families who have been identified with a common E233 Delta mutation. Very interestingly this is linked to myopia in one family. Despite the apparent phenotypic differences of the filensin (BFSP1) and CP49 (BFSP2) mutations, the data are still consistent with the beaded filament proteins being essential for lens function and specifically contributing to the optical properties of the lens. The fact that none of the mutations thus far reported affect either the conserved LNDR or TYRKLLEGE motifs that flank the central rod domain supports the view that this pair of IF proteins have unusual structural features and a distinctive assembly mechanism. The multiple sequence divergences suggest these proteins have been adapted to the specific functional requirements of lens fibre cells, a function that can be traced from squid to man.
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Affiliation(s)
- Ming-Der Perng
- School of Biological and Biomedical Sciences, The University of Durham, DH1 3LE, UK.
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Der Perng M, Su M, Wen SF, Li R, Gibbon T, Prescott AR, Brenner M, Quinlan RA. The Alexander disease-causing glial fibrillary acidic protein mutant, R416W, accumulates into Rosenthal fibers by a pathway that involves filament aggregation and the association of alpha B-crystallin and HSP27. Am J Hum Genet 2006; 79:197-213. [PMID: 16826512 PMCID: PMC1559481 DOI: 10.1086/504411] [Citation(s) in RCA: 102] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2006] [Accepted: 03/20/2006] [Indexed: 11/04/2022] Open
Abstract
Here, we describe the early events in the disease pathogenesis of Alexander disease. This is a rare and usually fatal neurodegenerative disorder whose pathological hallmark is the abundance of protein aggregates in astrocytes. These aggregates, termed "Rosenthal fibers," contain the protein chaperones alpha B-crystallin and HSP27 as well as glial fibrillary acidic protein (GFAP), an intermediate filament (IF) protein found almost exclusively in astrocytes. Heterozygous, missense GFAP mutations that usually arise spontaneously during spermatogenesis have recently been found in the majority of patients with Alexander disease. In this study, we show that one of the more frequently observed mutations, R416W, significantly perturbs in vitro filament assembly. The filamentous structures formed resemble assembly intermediates but aggregate more strongly. Consistent with the heterozygosity of the mutation, this effect is dominant over wild-type GFAP in coassembly experiments. Transient transfection studies demonstrate that R416W GFAP induces the formation of GFAP-containing cytoplasmic aggregates in a wide range of different cell types, including astrocytes. The aggregates have several important features in common with Rosenthal fibers, including the association of alpha B-crystallin and HSP27. This association occurs simultaneously with the formation of protein aggregates containing R416W GFAP and is also specific, since HSP70 does not partition with them. Monoclonal antibodies specific for R416W GFAP reveal, for the first time for any IF-based disease, the presence of the mutant protein in the characteristic histopathological feature of the disease, namely Rosenthal fibers. Collectively, these data confirm that the effects of the R416W GFAP are dominant, changing the assembly process in a way that encourages aberrant filament-filament interactions that then lead to protein aggregation and chaperone sequestration as early events in Alexander disease.
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Affiliation(s)
- Ming Der Perng
- School of Biological and Biomedical Sciences, The University of Durham, Durham, United Kingdom
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48
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Abstract
The eye lens is a fascinating organ as it is in essence living transparent matter. Lenticular transparency is achieved through the peculiarities of lens morphology, a semi-apoptotic process where cells elongate and loose their organelles and the precise molecular arrangement of the bulk of soluble lenticular proteins, the crystallins. The 16 crystallins ubiquitous in mammals and their modifications have been extensively characterized by 2-DE, liquid chromatography, mass spectrometry and other protein analysis techniques. The various solubility dependant fractions as well as subproteomes of lenticular morphological sections have also been explored in detail. Extensive post translational modification of the crystallins is encountered throughout the lens as a result of ageing and disease resulting in a vast number of protein species. Proteomics methodology is therefore ideal to further comprehensive understanding of this organ and the factors involved in cataractogenesis.
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Affiliation(s)
- W Hoehenwarter
- Max Planck Institute for Infection Biology, Core Facility Protein Analysis, Berlin, Germany
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49
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Affiliation(s)
- Ming Der Perng
- School of Biological and Biomedical Sciences, The University of Durham, Durham DH1 3LE, UK
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50
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Sinha D, Hose S, Zhang C, Neal R, Ghosh M, O'Brien TP, Sundin O, Goldberg MF, Robison WG, Russell P, Lo WK, Samuel Zigler J. A spontaneous mutation affects programmed cell death during development of the rat eye. Exp Eye Res 2005; 80:323-35. [PMID: 15721615 DOI: 10.1016/j.exer.2004.09.014] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2004] [Accepted: 09/29/2004] [Indexed: 12/30/2022]
Abstract
We have discovered a spontaneous mutation in the Sprague-Dawley rat with a novel eye phenotype that we have named Nuc1. The Nuc1 mutation behaves as a single semi-dominant locus with an intermediate phenotype in the heterozygotes. Heterozygotes exhibit nuclear cataracts. Homozygous Nuc1 rats are fully viable and have microphthalmia, retinal abnormalities and disruption of lens structure shortly before birth. The homozygous mutant shows no obvious pathology outside of the eye, indicating that the mutation is highly eye specific in its effects. An unusual feature of the mutation is that it prevents the normal programmed loss of nuclei from lens fiber cells, but does not affect the loss of other organelles. TUNEL, light, and electron microscopic studies show normal intact nuclei in lens fibers, in contrast to many other models with degenerate nuclei and unlike normal lenses where no such nuclei remain. The beaded filament protein, filensin, is down-regulated in fibers of Nuc1, while heat shock cognate 70 is up-regulated. Homozygous retinas are thicker than normal, and TUNEL labeling indicates roughly half the number of apoptotic cells compared to a wild-type retina. The transient layer of Chievitz persists in adult Nuc1 retina, indicative of delayed development. Hence, Nuc1 is a novel mutation that could be an eye-specific regulator of apoptosis.
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Affiliation(s)
- Debasish Sinha
- Department of Ophthalmology, School of Medicine, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD 21287, USA.
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