1
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Cheng C. Tissue, cellular, and molecular level determinants for eye lens stiffness and elasticity. FRONTIERS IN OPHTHALMOLOGY 2024; 4:1456474. [PMID: 39176256 PMCID: PMC11339033 DOI: 10.3389/fopht.2024.1456474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 06/28/2024] [Accepted: 07/26/2024] [Indexed: 08/24/2024]
Abstract
The eye lens is a transparent, ellipsoid tissue in the anterior chamber that is required for the fine focusing of light onto the retina to transmit a clear image. The focusing function of the lens is tied to tissue transparency, refractive index, and biomechanical properties. The stiffness and elasticity or resilience of the human lens allows for shape changes during accommodation to focus light from objects near and far. It has long been hypothesized that changes in lens biomechanical properties with age lead to the loss of accommodative ability and the need for reading glasses with age. However, the cellular and molecular mechanisms that influence lens biomechanical properties and/or change with age remain unclear. Studies of lens stiffness and resilience in mouse models with genetic defects or at advanced age inform us of the cytoskeletal, structural, and morphometric parameters that are important for biomechanical stability. In this review, we will explore whether: 1) tissue level changes, including the capsule, lens volume, and nucleus volume, 2) cellular level alterations, including cell packing, suture organization, and complex membrane interdigitations, and 3) molecular scale modifications, including the F-actin and intermediate filament networks, protein modifications, lipids in the cell membrane, and hydrostatic pressure, influence overall lens biomechanical properties.
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Affiliation(s)
- Catherine Cheng
- School of Optometry and Vision Science Program, Indiana University, Bloomington, IN, United States
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2
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Greiling TM, Clark JM, Clark JI. The significance of growth shells in development of symmetry, transparency, and refraction of the human lens. FRONTIERS IN OPHTHALMOLOGY 2024; 4:1434327. [PMID: 39100140 PMCID: PMC11294239 DOI: 10.3389/fopht.2024.1434327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/17/2024] [Accepted: 06/27/2024] [Indexed: 08/06/2024]
Abstract
Human visual function depends on the biological lens, a biconvex optical element formed by coordinated, synchronous generation of growth shells produced from ordered cells at the lens equator, the distal edge of the epithelium. Growth shells are comprised of straight (St) and S-shaped (SSh) lens fibers organized in highly symmetric, sinusoidal pattern which optimizes both the refractile, transparent structure and the unique microcirculation that regulates hydration and nutrition over the lifetime of an individual. The fiber cells are characterized by diversity in composition and age. All fiber cells remain interconnected in their growth shells throughout the life of the adult lens. As an optical element, cellular differentiation is constrained by the physical properties of light and its special development accounts for its characteristic symmetry, gradient of refractive index (GRIN), short range transparent order (SRO), and functional longevity. The complex sinusoidal structure is the basis for the lens microcirculation required for the establishment and maintenance of image formation.
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Affiliation(s)
- Teri M. Greiling
- Department of Dermatology, School of Medicine, Oregon Health & Science University, Portland, OR, United States
| | - Judy M. Clark
- Department of Biological Structure, University of Washington, Seattle, WA, United States
| | - John I. Clark
- Department of Biological Structure, University of Washington, Seattle, WA, United States
- Department of Biological Structure & Ophthalmology, School of Medicine, University of Washington, Seattle, WA, United States
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3
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Tahsini V, Gil IC, Kling S. Storage-induced mechanical changes of porcine lenses assessed with optical coherence elastography and inverse finite element modeling. Front Bioeng Biotechnol 2024; 12:1398659. [PMID: 38938986 PMCID: PMC11208870 DOI: 10.3389/fbioe.2024.1398659] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2024] [Accepted: 05/27/2024] [Indexed: 06/29/2024] Open
Abstract
Introduction In an effort of gaining a better understanding of the lens mechanics, ex vivo lenses samples are often used. Yet, ex vivo tissue might undergo important postmortem changes depending on the unavoidable preservation method employed. The purpose of this study was to assess how various storage conditions and the removal of the lens capsule affect the mechanical properties of ex vivo porcine lens samples. Methods A total of 81 freshly enucleated porcine eyes were obtained and divided into six groups and preserved differently. In the first three groups, the lens within the intact eye was preserved for 24 h by: (i) freezing at -80°C (n = 12), (ii) freezing at -20°C (n = 12), and (iii) refrigeration at +8°C (n = 12). In the remaining groups, the lenses were immediately extracted and treated as follows: (iv) kept intact, no storage (n = 12), (v) decapsulated, no storage (n = 21), and (vi) immersed in Minimum Essential Medium (MEM) at +8°C (n = 12) for 24 h. Frozen lenses were thawed at room temperature. Each lens was compressed between two glass lamella and subjected, first to a period of relaxation during which the compression force was recorded and second to an oscillating micro-compression while the deformation was recorded with a total of 256 subsequent B-scans via optical coherence tomography. The corresponding axial strain was retrieved via phase-sensitive image processing and subsequently used as input for an inverse finite element analysis (iFEA) to retrieve the visco-hyperelastic material properties of the lenses. Results After freezing at temperatures of -80°C and -20°C, the cortical strains increased by 14% (p = 0.01) and 34% (p < 0.001), and the nuclear strains decreased by 17% (p = 0.014) and 36% (p < 0.001), compared to the lenses tested immediately after postmortem, respectively. According to iFEA, this resulted from an increased ratio of the nuclear: cortical E-modulus (4.06 and 7.06) in -80°C and -20°C frozen lenses compared to fresh lenses (3.3). Decapsulation had the largest effect on the material constant C10, showing an increase both in the nucleus and cortex. Preservation of the intact eye in the refrigerator induced the least mechanical alterations in the lens, compared to the intact fresh condition. Discussion Combining iFEA with optical coherence elastography allowed us to identify important changes in the lens mechanics induced after different preserving ex vivo methods.
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Affiliation(s)
- Vahoura Tahsini
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
| | - Iulen Cabeza Gil
- Aragón Institute of Engineering Research (i3A), University of Zaragoza, Zaragoza, Spain
| | - Sabine Kling
- ARTORG Center for Biomedical Engineering Research, University of Bern, Bern, Switzerland
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Xiang J, Pompetti AJ, Faranda AP, Wang Y, Novo SG, Li DWC, Duncan MK. ATF4 May Be Essential for Adaption of the Ocular Lens to Its Avascular Environment. Cells 2023; 12:2636. [PMID: 37998373 PMCID: PMC10670291 DOI: 10.3390/cells12222636] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Revised: 10/30/2023] [Accepted: 11/03/2023] [Indexed: 11/25/2023] Open
Abstract
The late embryonic mouse lens requires the transcription factor ATF4 for its survival although the underlying mechanisms were unknown. Here, RNAseq analysis revealed that E16.5 Atf4 null mouse lenses downregulate the mRNA levels of lens epithelial markers as well as known markers of late lens fiber cell differentiation. However, a comparison of this list of differentially expressed genes (DEGs) with other known transcriptional regulators of lens development indicated that ATF4 expression is not directly controlled by the previously described lens gene regulatory network. Pathway analysis revealed that the Atf4 DEG list was enriched in numerous genes involved in nutrient transport, amino acid biosynthesis, and tRNA charging. These changes in gene expression likely result in the observed reductions in lens free amino acid and glutathione levels, which would result in the observed low levels of extractable lens protein, finally leading to perinatal lens disintegration. These data demonstrate that ATF4, via its function in the integrated stress response, is likely to play a crucial role in mediating the adaption of the lens to the avascularity needed to maintain lens transparency.
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Affiliation(s)
- Jiawen Xiang
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510230, China
| | - Anthony J. Pompetti
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Adam P. Faranda
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Yan Wang
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - Samuel G. Novo
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
| | - David Wan-Cheng Li
- The State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou 510230, China
| | - Melinda K. Duncan
- Department of Biological Sciences, University of Delaware, Newark, DE 19716, USA
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5
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Paidi SK, Zhang Q, Yang Y, Xia CH, Ji N, Gong X. Adaptive optical two-photon fluorescence microscopy probes cellular organization of ocular lenses in vivo. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.01.17.524320. [PMID: 36711806 PMCID: PMC9882239 DOI: 10.1101/2023.01.17.524320] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The mammalian ocular lens is an avascular multicellular organ that grows continuously throughout life. Traditionally, its cellular organization is investigated using dissected lenses, which eliminates in vivo environmental and structural support. Here, we demonstrated that two-photon fluorescence microscopy (2PFM) can visualize lens cells in vivo. To maintain subcellular resolution at depth, we employed adaptive optics (AO) to correct aberrations due to ocular and lens tissues, which led to substantial signal and resolution improvements. Imaging lens cells up to 980 μm deep, we observed novel cellular organizations including suture-associated voids, enlarged vacuoles, and large cavities, contrary to the conventional view of a highly ordered organization. We tracked these features longitudinally over weeks and observed the incorporation of new cells during growth. Taken together, non-invasive longitudinal in vivo imaging of lens morphology using AO 2PFM will allow us to directly observe the development or alterations of lens cellular organization in living animals.
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Affiliation(s)
- Santosh Kumar Paidi
- School of Optometry, University of California, Berkeley, California 94720, USA
| | - Qinrong Zhang
- Department of Physics, University of California, Berkeley, California 94720, USA,Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA
| | - Yuhan Yang
- Department of Physics, University of California, Berkeley, California 94720, USA
| | - Chun-Hong Xia
- School of Optometry, University of California, Berkeley, California 94720, USA,Vision Science Program, University of California, Berkeley, California 94720, USA
| | - Na Ji
- Department of Physics, University of California, Berkeley, California 94720, USA,Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720, USA,Helen Wills Neuroscience Institute, University of California, Berkeley, CA 94720, USA,Molecular Biophysics and Integrated Bioimaging Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA,Corresponding authors: Xiaohua Gong () and Na Ji ()
| | - Xiaohua Gong
- School of Optometry, University of California, Berkeley, California 94720, USA,Vision Science Program, University of California, Berkeley, California 94720, USA,Corresponding authors: Xiaohua Gong () and Na Ji ()
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6
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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] [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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7
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Cheng C, Wang K, Hoshino M, Uesugi K, Yagi N, Pierscionek B. EphA2 Affects Development of the Eye Lens Nucleus and the Gradient of Refractive Index. Invest Ophthalmol Vis Sci 2022; 63:2. [PMID: 34978559 PMCID: PMC8742528 DOI: 10.1167/iovs.63.1.2] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Purpose Our studies in mouse eye lenses demonstrate that ephrin-A5 and EphA2 are needed for normal epithelial cells and lens transparency. We sought to determine whether EphA2 and ephrin-A5 are important for lens morphometrics, nucleus formation, and refractive index. Methods We performed tissue morphometric measurements, electron microscopy, Western blots, and interferometric measurements using an X-ray synchrotron beam source to measure the gradient of refractive index (GRIN) to compare mouse lenses with genetic disruption of EphA2 or ephrin-A5. Results Morphometric analysis revealed that although there is no change in the overall lens volume, there is a change in lens shape in both EphA2-/- lenses and ephrin-A5-/- lenses. Surprisingly, EphA2-/- lenses had small and soft lens nuclei different from hard lens nuclei of control lenses. SEM images revealed changes in cell morphology of EphA2-/- fiber cells close to the center of the lens. Inner EphA2-/- lens fibers had more pronounced tongue-and-groove interdigitations and formed globular membrane morphology only in the deepest layers of the lens nucleus. We did not observe nuclear defects in ephrin-A5-/- lenses. There was an overall decrease in magnitude of refractive index across EphA2-/- lenses, which is most pronounced in the nucleus. Conclusions This work reveals that Eph-ephrin signaling plays a role in fiber cell maturation, nuclear compaction, and lens shape. Loss of EphA2 disrupts the nuclear compaction resulting in a small lens nucleus. Our data suggest that Eph-ephrin signaling may be required for fiber cell membrane reorganization and compaction and for establishing a normal GRIN.
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Affiliation(s)
- Catherine Cheng
- School of Optometry, Indiana University, Bloomington, IN, United States
| | - Kehao Wang
- Beijing Advanced Innovation Centre for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Engineering Medicine, Beihang University, Beijing, China
| | - Masato Hoshino
- Japan Synchrotron Radiation Research Institute (Spring-8), 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 Japan
| | - Kentaro Uesugi
- Japan Synchrotron Radiation Research Institute (Spring-8), 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 Japan
| | - Naoto Yagi
- Japan Synchrotron Radiation Research Institute (Spring-8), 1-1-1, Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198 Japan
| | - Barbara Pierscionek
- Faculty of Health, Education, Medicine and Social Care, Medical Technology Research Centre, Anglia Ruskin University, Chelmsford Campus, United Kingdom
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8
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Cheng C. EphA2 and Ephrin-A5 Guide Eye Lens Suture Alignment and Influence Whole Lens Resilience. Invest Ophthalmol Vis Sci 2021; 62:3. [PMID: 34854885 PMCID: PMC8648058 DOI: 10.1167/iovs.62.15.3] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Fine focusing of light by the eye lens onto the retina relies on the ability of the lens to change shape during the process of accommodation. Little is known about the cellular structures that regulate elasticity and resilience. We tested whether Eph–ephrin signaling is involved in lens biomechanical properties. Methods We used confocal microscopy and tissue mechanical testing to examine mouse lenses with genetic disruption of EphA2 or ephrin-A5. Results Confocal imaging revealed misalignment of the suture between each shell of newly added fiber cells in knockout lenses. Despite having disordered sutures, loss of EphA2 or ephrin-A5 did not affect lens stiffness. Surprisingly, knockout lenses were more resilient and recovered almost completely after load removal. Confocal microscopy and quantitative image analysis from live lenses before, during, and after compression revealed that knockout lenses had misaligned Y-sutures, leading to a change in force distribution during compression. Knockout lenses displayed decreased separation of fiber cell tips at the anterior suture at high loads and had more complete recovery after load removal, which leads to improved whole-lens resiliency. Conclusions EphA2 and ephrin-A5 are needed for normal patterning of fiber cell tips and the formation of a well-aligned Y-suture with fiber tips stacked on top of previous generations of fiber cells. The misalignment of lens sutures leads to increased resilience after compression. The data suggest that alignment of the Y-suture may constrain the overall elasticity and resilience of the lens.
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Affiliation(s)
- Catherine Cheng
- School of Optometry and Vision Science Program, Indiana University, Bloomington, Indiana, United States
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9
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Bradley AE, Wancket LM, Rinke M, Gruebbel MM, Saladino BH, Schafer K, Katsuta O, Garcia B, Chanut F, Hughes K, Nelson K, Himmel L, McInnes E, Schucker A, Uchida K. International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of the Rabbit. J Toxicol Pathol 2021; 34:183S-292S. [PMID: 34712007 PMCID: PMC8544166 DOI: 10.1293/tox.34.183s] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for
Lesions Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of
Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North
America (STP) to develop an internationally accepted nomenclature for proliferative and
non-proliferative lesions in laboratory animals. The purpose of this publication is to
provide a standardized nomenclature for classifying microscopic lesions observed in most
tissues and organs from the laboratory rabbit used in nonclinical safety studies. Some of
the lesions are illustrated by color photomicrographs. The standardized nomenclature
presented in this document is also available electronically on the internet
(http://www.goreni.org/). Sources of material included histopathology databases from
government, academia, and industrial laboratories throughout the world. Content includes
spontaneous lesions as well as lesions induced by exposure to test materials. Relevant
infectious and parasitic lesions are included as well. A widely accepted and utilized
international harmonization of nomenclature for lesions in laboratory animals will provide
a common language among regulatory and scientific research organizations in different
countries and increase and enrich international exchanges of information among
toxicologists and pathologists.
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Affiliation(s)
- Alys E Bradley
- Charles River Laboratories Edinburgh Ltd, Tranent, Scotland, UK
| | | | | | | | | | | | | | - Begonya Garcia
- Charles River Laboratories Edinburgh Ltd, Tranent, Scotland, UK
| | - Franck Chanut
- Sanofi, 1 Avenue Pierre Brosselette, 91380 Chilly-Mazarin, France
| | | | | | - Lauren Himmel
- Vanderbilt University Medical Center, Nashville, TN, USA
| | | | - Adrienne Schucker
- American Preclinical Services, LLC, 8945 Evergreen Blvd, Minneapolis, MN 55433
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Colman K, Andrews RN, Atkins H, Boulineau T, Bradley A, Braendli-Baiocco A, Capobianco R, Caudell D, Cline M, Doi T, Ernst R, van Esch E, Everitt J, Fant P, Gruebbel MM, Mecklenburg L, Miller AD, Nikula KJ, Satake S, Schwartz J, Sharma A, Shimoi A, Sobry C, Taylor I, Vemireddi V, Vidal J, Wood C, Vahle JL. International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Non-proliferative and Proliferative Lesions of the Non-human Primate ( M. fascicularis). J Toxicol Pathol 2021; 34:1S-182S. [PMID: 34712008 PMCID: PMC8544165 DOI: 10.1293/tox.34.1s] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for Lesions Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North America (STP) to develop an internationally accepted nomenclature for proliferative and nonproliferative lesions in laboratory animals. The purpose of this publication is to provide a standardized nomenclature for classifying microscopic lesions observed in most tissues and organs from the nonhuman primate used in nonclinical safety studies. Some of the lesions are illustrated by color photomicrographs. The standardized nomenclature presented in this document is also available electronically on the internet (http://www.goreni.org/). Sources of material included histopathology databases from government, academia, and industrial laboratories throughout the world. Content includes spontaneous lesions as well as lesions induced by exposure to test materials. Relevant infectious and parasitic lesions are included as well. A widely accepted and utilized international harmonization of nomenclature for lesions in laboratory animals will provide a common language among regulatory and scientific research organizations in different countries and increase and enrich international exchanges of information among toxicologists and pathologists.
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Affiliation(s)
- Karyn Colman
- Novartis Institutes for BioMedical Research, Cambridge, MA,
USA
| | - Rachel N. Andrews
- Wake Forest School of Medicine, Department of Radiation
Oncology, Winston-Salem, NC, USA
| | - Hannah Atkins
- Penn State College of Medicine, Department of Comparative
Medicine, Hershey, PA, USA
| | | | - Alys Bradley
- Charles River Laboratories Edinburgh Ltd., Tranent,
Scotland, UK
| | - Annamaria Braendli-Baiocco
- Roche Pharma Research and Early Development, Pharmaceutical
Sciences, Roche Innovation Center Basel, Switzerland
| | - Raffaella Capobianco
- Janssen Research & Development, a Division of Janssen
Pharmaceutica NV, Beerse, Belgium
| | - David Caudell
- Department of Pathology, Section on Comparative Medicine,
Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Mark Cline
- Department of Pathology, Section on Comparative Medicine,
Wake Forest School of Medicine, Winston-Salem, NC, USA
| | - Takuya Doi
- LSIM Safety Institute Corporation, Ibaraki, Japan
| | | | | | - Jeffrey Everitt
- Department of Pathology, Duke University School of
Medicine, Durham, NC, USA
| | | | | | | | - Andew D. Miller
- Cornell University College of Veterinary Medicine, Ithaca,
NY, USA
| | | | - Shigeru Satake
- Shin Nippon Biomedical Laboratories, Ltd., Kagoshima and
Tokyo, Japan
| | | | - Alok Sharma
- Covance Laboratories, Inc., Madison, WI, USA
| | | | | | | | | | | | - Charles Wood
- Boehringer Ingelheim Pharmaceuticals, Inc., Ridgefield, CT,
USA
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11
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Wang K, Vorontsova I, Hoshino M, Uesugi K, Yagi N, Hall JE, Schilling TF, Pierscionek BK. Aquaporins Have Regional Functions in Development of Refractive Index in the Zebrafish Eye Lens. Invest Ophthalmol Vis Sci 2021; 62:23. [PMID: 33724295 PMCID: PMC7980049 DOI: 10.1167/iovs.62.3.23] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
Purpose In the eye lens, cytosolic protein concentrations increase progressively from the periphery to the center, contributing to the gradient of refractive index (GRIN). Aquaporins are membrane proteins of lens fiber cells that regulate water transport and adhesion and interact with cytoskeletal proteins. This study investigates how these membrane proteins contribute to proper development of the lens GRIN. Methods Loss-of-function deletions of aqp0a and/or aqp0b in zebrafish were generated using CRISPR/Cas9 gene editing. Lenses of single aqp0a−/− mutants, single aqp0b−/− mutants, and double aqp0a−/−/aqp0b−/− mutants from larval to elderly adult stages were measured using x-ray Talbot interferometry at SPring8 in Japan. The three-dimensional GRIN profiles in two orthogonal cross-sectional planes of each lens were analyzed and compared with in vivo images and previous results obtained from wild-type lenses. Results Single aqp0a−/− mutants tended to show asymmetric GRIN profiles, with the central plateau regions shifted anteriorly. Single aqp0b−/− mutants had smooth, symmetric GRIN profiles throughout development until spoke opacities appeared in several extremely old samples. Double aqp0a−/−/aqp0b−/− mutants showed lower magnitude GRIN profiles, as well as dips in the central plateau region. Conclusions These findings suggest that Aqp0a and Aqp0b have region-specific functions in the lens: Aqp0a is active peripherally, regulating centralization of the plateau region, and this function cannot be compensated for by Aqp0b. In the lens center, either Aqp0a or Aqp0b is required for formation of the plateau region, as well as for the GRIN to reach its maximum magnitude in mature lenses.
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Affiliation(s)
- Kehao Wang
- Beijing Advanced Innovation Centre for Biomedical Engineering, Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, Beijing, China
| | - Irene Vorontsova
- Department of Physiology and Biophysics, University of California Irvine, Irvine, California, United States.,Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States
| | - Masato Hoshino
- Japan Synchrotron Radiation Research Institute, Hyogo, Japan
| | - Kentaro Uesugi
- Japan Synchrotron Radiation Research Institute, Hyogo, Japan
| | - Naoto Yagi
- Japan Synchrotron Radiation Research Institute, Hyogo, Japan
| | - James Ewbank Hall
- Department of Physiology and Biophysics, University of California Irvine, Irvine, California, United States
| | - Thomas Friedrich Schilling
- Department of Developmental and Cell Biology, University of California Irvine, Irvine, California, United States
| | - Barbara Krystyna Pierscionek
- School of Life Sciences and Education, Staffordshire University, Stoke-on-Trent, United Kingdom.,Faculty of Health, Education, Medicine and Social Care, Chelmsford Campus, Anglia Ruskin University, United Kingdom
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12
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Gupta A, Ruminski D, Jimenez Villar A, Duarte Toledo R, Manzanera S, Panezai S, Mompean J, Artal P, Grulkowski I. In vivo SS-OCT imaging of crystalline lens sutures. BIOMEDICAL OPTICS EXPRESS 2020; 11:5388-5400. [PMID: 33149958 PMCID: PMC7587285 DOI: 10.1364/boe.401254] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Revised: 08/20/2020] [Accepted: 08/26/2020] [Indexed: 05/07/2023]
Abstract
We demonstrate in vivo three-dimensional (3-D) visualization of crystalline lens sutures in healthy eyes using swept source optical coherence tomography (SS-OCT). Volumetric data sets of the crystalline lenses were acquired and processed to obtain enhanced contrast projection images and to extract suture patterns in both anterior and posterior lens. The results presented different types of the sutures including Y-sutures, simple and complex star sutures. Age-related changes in suture arrangement were characterized quantitatively. Crystalline lens suture imaging with SS-OCT might be a useful tool in fundamental studies on development and ageing of human lens.
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Affiliation(s)
- Ashish Gupta
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, ul. Grudziądzka 5, 87-100 Toruń, Poland
| | - Daniel Ruminski
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, ul. Grudziądzka 5, 87-100 Toruń, Poland
| | - Alfonso Jimenez Villar
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, ul. Grudziądzka 5, 87-100 Toruń, Poland
| | - Raúl Duarte Toledo
- Laboratorio de Óptica, Instituto Universitario de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo, E-30100, Murcia, Spain
| | - Silvestre Manzanera
- Laboratorio de Óptica, Instituto Universitario de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo, E-30100, Murcia, Spain
| | - Spozmai Panezai
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, ul. Grudziądzka 5, 87-100 Toruń, Poland
| | - Juan Mompean
- Laboratorio de Óptica, Instituto Universitario de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo, E-30100, Murcia, Spain
| | - Pablo Artal
- Laboratorio de Óptica, Instituto Universitario de Investigación en Óptica y Nanofísica, Universidad de Murcia, Campus de Espinardo, E-30100, Murcia, Spain
| | - Ireneusz Grulkowski
- Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University, ul. Grudziądzka 5, 87-100 Toruń, Poland
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13
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Logan CM, Menko AS. Microtubules: Evolving roles and critical cellular interactions. Exp Biol Med (Maywood) 2019; 244:1240-1254. [PMID: 31387376 DOI: 10.1177/1535370219867296] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Microtubules are cytoskeletal elements known as drivers of directed cell migration, vesicle and organelle trafficking, and mitosis. In this review, we discuss new research in the lens that has shed light into further roles for stable microtubules in the process of development and morphogenesis. In the lens, as well as other systems, distinct roles for characteristically dynamic microtubules and stabilized populations are coming to light. Understanding the mechanisms of microtubule stabilization and the associated microtubule post-translational modifications is an evolving field of study. Appropriate cellular homeostasis relies on not only one cytoskeletal element, but also rather an interaction between cytoskeletal proteins as well as other cellular regulators. Microtubules are key integrators with actin and intermediate filaments, as well as cell–cell junctional proteins and other cellular regulators including myosin and RhoGTPases to maintain this balance.Impact statementThe role of microtubules in cellular functioning is constantly expanding. In this review, we examine new and exciting fields of discovery for microtubule’s involvement in morphogenesis, highlight our evolving understanding of differential roles for stabilized versus dynamic subpopulations, and further understanding of microtubules as a cellular integrator.
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Affiliation(s)
- Caitlin M Logan
- Pathology Anatomy and Cell Biology Department, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - A Sue Menko
- Pathology Anatomy and Cell Biology Department, Thomas Jefferson University, Philadelphia, PA 19107, USA
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14
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Utlu B, Akyol Salman İ, Öztürk N. Pigment epithelial-derived factor in the lens anterior capsule of patients with senile cataract with pseudoexfoliation. Clin Exp Optom 2019; 103:207-211. [PMID: 31090113 DOI: 10.1111/cxo.12922] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 03/21/2019] [Accepted: 04/11/2019] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND This study sought to evaluate pigment epithelial-derived factor (PEDF) levels in lens anterior capsule material taken during cataract surgery from patients with senile cataract with pseudoexfoliation. METHODS The study included 90 eyes of 86 patients who were diagnosed with, and underwent surgery for, cataracts. Sixty of the eyes included in the study had senile cataract. Thirty eyes of 30 young patients with other forms of cataract were included as a control group. Pseudoexfoliation was present in 21 patients with senile cataract. PEDF levels in the lens anterior capsule material - extracted with capsulorhexis in the classical phacoemulsification procedure - were measured by the enzyme-linked immunosorbent assay method and compared between the groups. RESULTS The PEDF level in the lens anterior capsule in the senile cataract patient group was 149.36 ± 17.46 pg/ml. A statistically significant lower level of PEDF was found in the lens anterior capsule of patients with senile cataract compared with the other groups. In the patient group with pseudoexfoliation, the PEDF level in the lens anterior capsule was found to be statistically significantly lower than the patient group without pseudoexfoliation. CONCLUSION PEDF levels decrease with senile cataract and pseudoexfoliation. These findings may clarify the pathogenesis of these conditions and point toward alternative treatment modalities.
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Affiliation(s)
- Bahadır Utlu
- Ophthalmology, Regional Training and Research Hospital, Health Sciences University, Erzurum, Turkey
| | | | - Nurinnisa Öztürk
- Medical Biochemistry, Faculty of Medicine, Atatürk University, Erzurum, Turkey
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15
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Chicken GRIFIN: binding partners, developmental course of localization and activation of its lens-specific gene expression by L-Maf/Pax6. Cell Tissue Res 2018; 375:665-683. [PMID: 30328540 DOI: 10.1007/s00441-018-2931-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Accepted: 09/18/2018] [Indexed: 01/11/2023]
Abstract
Tissue lectins appear to be involved in a broad range of physiological processes, as reflected for the members of the family of galectins by referring to them as adhesion/growth-regulatory effectors. In order to clarify the significance of galectin presence, key challenges are to define their binding partners and the profile of localization. Having identified the chicken galectin-related interfiber protein (C-GRIFIN) as lens-specific protein present in the main body of adult lens, we here report its interaction with lens proteins in ligand blotting. The assumption for pairing with α-, β- and δ-crystallins was ascertained by mass spectrometric detection of their presence in eluted fractions obtained by affinity chromatography. Biochemical and immunohistochemical monitoring revealed protein presence from about 3-day-old embryos onwards, mostly in the cytoplasm of elongated posterior cells, later in secondary lens fiber cells. On the level of gene expression, its promoter was activated by transcription factor L-Maf alone and together with Pax6 like a crystallin gene, substantiating C-GRIFIN's status as lens-specific galectin. Using this combined strategy for counterreceptor and expression profiling by bio- and histochemical methods including light, electron and fluorescence microscopy, respective monitoring in lens development can now be taken to the level of the complete galectin family.
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16
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Li J, Xia CH, Wang E, Yao K, Gong X. Screening, genetics, risk factors, and treatment of neonatal cataracts. Birth Defects Res 2017; 109:734-743. [PMID: 28544770 DOI: 10.1002/bdr2.1050] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2017] [Accepted: 04/15/2017] [Indexed: 12/21/2022]
Abstract
Neonatal cataracts remain the most common cause of visual loss in children worldwide and have diverse, often unknown, etiologies. This review summarizes current knowledge about the detection, treatment, genetics, risk factors, and molecular mechanisms of congenital cataracts. We emphasize significant progress and topics requiring further study in both clinical cataract therapy and basic lens research. Advances in genetic screening and surgical technologies have improved the diagnosis, management, and visual outcomes of affected children. For example, mutations in lens crystallins and membrane/cytoskeletal components that commonly underlie genetically inherited cataracts are now known. However, many questions still remain regarding the causes, progression, and pathology of neonatal cataracts. Further investigations are also required to improve diagnostic criteria for determining the timing of appropriate interventions, such as the implantation of intraocular lenses and postoperative management strategies, to ensure safety and predictable visual outcomes for children. Birth Defects Research 109:734-743, 2017. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Jinyu Li
- Eye Center, Second Affiliated Hospital of Medical College, Zhejiang University, Hangzhou, Zhejiang, China.,Key Laboratory of Ophthalmology of Zhejiang Province, China
| | - Chun-Hong Xia
- School of Optometry and Vision Science Program, University of California, Berkeley, California, USA
| | - Eddie Wang
- School of Optometry and Vision Science Program, University of California, Berkeley, California, USA
| | - Ke Yao
- Eye Center, Second Affiliated Hospital of Medical College, Zhejiang University, Hangzhou, Zhejiang, China.,Key Laboratory of Ophthalmology of Zhejiang Province, China
| | - Xiaohua Gong
- School of Optometry and Vision Science Program, University of California, Berkeley, California, USA
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17
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Wu JJ, Wu W, Tholozan FM, Saunter CD, Girkin JM, Quinlan RA. A dimensionless ordered pull-through model of the mammalian lens epithelium evidences scaling across species and explains the age-dependent changes in cell density in the human lens. J R Soc Interface 2016; 12:20150391. [PMID: 26236824 PMCID: PMC4528606 DOI: 10.1098/rsif.2015.0391] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
We present a mathematical (ordered pull-through; OPT) model of the cell-density profile for the mammalian lens epithelium together with new experimental data. The model is based upon dimensionless parameters, an important criterion for inter-species comparisons where lens sizes can vary greatly (e.g. bovine (approx. 18 mm); mouse (approx. 2 mm)) and confirms that mammalian lenses scale with size. The validated model includes two parameters: β/α, which is the ratio of the proliferation rate in the peripheral and in the central region of the lens; and γGZ, a dimensionless pull-through parameter that accounts for the cell transition and exit from the epithelium into the lens body. Best-fit values were determined for mouse, rat, rabbit, bovine and human lens epithelia. The OPT model accounts for the peak in cell density at the periphery of the lens epithelium, a region where cell proliferation is concentrated and reaches a maximum coincident with the germinative zone. The β/α ratio correlates with the measured FGF-2 gradient, a morphogen critical to lens cell survival, proliferation and differentiation. As proliferation declines with age, the OPT model predicted age-dependent changes in cell-density profiles, which we observed in mouse and human lenses.
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Affiliation(s)
- Jun Jie Wu
- Biophysical Sciences Institute and School of Engineering and Computing Sciences, Durham University, Durham DH1 3LE, UK
- e-mail:
| | - Weiju Wu
- Biophysical Sciences Institute and School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, UK
| | - Frederique M. Tholozan
- Biophysical Sciences Institute and School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, UK
| | - Christopher D. Saunter
- Biophysical Sciences Institute and Department of Physics, Durham University, Durham DH1 3LE, UK
| | - John M. Girkin
- Biophysical Sciences Institute and Department of Physics, Durham University, Durham DH1 3LE, UK
| | - Roy A. Quinlan
- Biophysical Sciences Institute and School of Biological and Biomedical Sciences, Durham University, Durham DH1 3LE, UK
- e-mail:
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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] [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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Abstract
PURPOSE A distinct subset of genes, so-called "late fiber genes," is expressed in cells bordering the central, organelle-free zone (OFZ) of the lens. The purpose of this study was to identify additional members of this group. METHODS Fiber cells were harvested from various layers of the lens by laser micro-dissection and subjected to microarray, in situ hybridization, and Western blot analysis. RESULTS Expression of Livin, a member of the inhibitor of apoptosis protein (IAP) family encoded by Birc7, was strongly upregulated in deep cortical fiber cells. The depth-dependent distribution of Livin mRNA was confirmed by quantitative PCR and in situ hybridization. The onset of Livin expression coincided with loss of organelles from primary fiber cells. Livin expression peaked at 1 month but was sustained even in aged lenses. Antibodies raised against mouse Livin labeled multiple bands on immunoblots, reflecting progressive proteolysis of the parent molecule during differentiation. Mice harboring a floxed Birc7 allele were generated and used to conditionally delete Birc7 in lens. Lenses from knockout mice grew normally and retained their transparency, suggesting that Livin does not have an indispensable role in fiber cell differentiation. CONCLUSIONS Birc7 is a late fiber gene of the mouse lens. In tumor cells, Livin acts as an antiapoptotic protein, but its function in the lens is enigmatic. Livin is a RING domain protein with putative E3 ubiquitin ligase activity. Its expression in cells bordering the OFZ is consistent with a role in organelle degradation, a process in which the ubiquitin proteasome pathway has been implicated previously.
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20
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Cheng C, Nowak RB, Gao J, Sun X, Biswas SK, Lo WK, Mathias RT, Fowler VM. Lens ion homeostasis relies on the assembly and/or stability of large connexin 46 gap junction plaques on the broad sides of differentiating fiber cells. Am J Physiol Cell Physiol 2015; 308:C835-47. [PMID: 25740157 PMCID: PMC4436989 DOI: 10.1152/ajpcell.00372.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2014] [Accepted: 03/03/2015] [Indexed: 12/31/2022]
Abstract
The eye lens consists of layers of tightly packed fiber cells, forming a transparent and avascular organ that is important for focusing light onto the retina. A microcirculation system, facilitated by a network of gap junction channels composed of connexins 46 and 50 (Cx46 and Cx50), is hypothesized to maintain and nourish lens fiber cells. We measured lens impedance in mice lacking tropomodulin 1 (Tmod1, an actin pointed-end capping protein), CP49 (a lens-specific intermediate filament protein), or both Tmod1 and CP49. We were surprised to find that simultaneous loss of Tmod1 and CP49, which disrupts cytoskeletal networks in lens fiber cells, results in increased gap junction coupling resistance, hydrostatic pressure, and sodium concentration. Protein levels of Cx46 and Cx50 in Tmod1(-/-);CP49(-/-) double-knockout (DKO) lenses were unchanged, and electron microscopy revealed normal gap junctions. However, immunostaining and quantitative analysis of three-dimensional confocal images showed that Cx46 gap junction plaques are smaller and more dispersed in DKO differentiating fiber cells. The localization and sizes of Cx50 gap junction plaques in DKO fibers were unaffected, suggesting that Cx46 and Cx50 form homomeric channels. We also demonstrate that gap junction plaques rest in lacunae of the membrane-associated actin-spectrin network, suggesting that disruption of the actin-spectrin network in DKO fibers may interfere with gap junction plaque accretion into micrometer-sized domains or alter the stability of large plaques. This is the first work to reveal that normal gap junction plaque localization and size are associated with normal lens coupling conductance.
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Affiliation(s)
- Catherine Cheng
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California
| | - Roberta B Nowak
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California
| | - Junyuan Gao
- Department of Physiology and Biophysics, State University of New York at Stony Brook, Stony Brook, New York; and
| | - Xiurong Sun
- Department of Physiology and Biophysics, State University of New York at Stony Brook, Stony Brook, New York; and
| | - Sondip K Biswas
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, Georgia
| | - Woo-Kuen Lo
- Department of Neurobiology, Morehouse School of Medicine, Atlanta, Georgia
| | - Richard T Mathias
- Department of Physiology and Biophysics, State University of New York at Stony Brook, Stony Brook, New York; and
| | - Velia M Fowler
- Department of Cell and Molecular Biology, The Scripps Research Institute, La Jolla, California;
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21
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Cheng C, Ansari MM, Cooper JA, Gong X. EphA2 and Src regulate equatorial cell morphogenesis during lens development. Development 2013; 140:4237-45. [PMID: 24026120 DOI: 10.1242/dev.100727] [Citation(s) in RCA: 57] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
High refractive index and transparency of the eye lens require uniformly shaped and precisely aligned lens fiber cells. During lens development, equatorial epithelial cells undergo cell-to-cell alignment to form meridional rows of hexagonal cells. The mechanism that controls this morphogenesis from randomly packed cuboidal epithelial cells to highly organized hexagonal fiber cells remains unknown. In Epha2(-/-) mouse lenses, equatorial epithelial cells fail to form precisely aligned meridional rows; moreover, the lens fulcrum, where the apical tips of elongating epithelial cells constrict to form an anchor point before fiber cell differentiation and elongation at the equator, is disrupted. Phosphorylated Src-Y424 and cortactin-Y466, actin and EphA2 cluster at the vertices of wild-type hexagonal epithelial cells in organized meridional rows. However, phosphorylated Src and phosphorylated cortactin are not detected in disorganized Epha2(-/-) cells with altered F-actin distribution. E-cadherin junctions, which are normally located at the basal-lateral ends of equatorial epithelial cells and are diminished in newly differentiating fiber cells, become widely distributed in the apical, lateral and basal sides of epithelial cells and persist in differentiating fiber cells in Epha2(-/-) lenses. Src(-/-) equatorial epithelial cells also fail to form precisely aligned meridional rows and lens fulcrum. These results indicate that EphA2/Src signaling is essential for the formation of the lens fulcrum. EphA2 also regulates Src/cortactin/F-actin complexes at the vertices of hexagonal equatorial cells for cell-to-cell alignment. This mechanistic information explains how EphA2 mutations lead to disorganized lens cells that subsequently contribute to altered refractive index and cataracts in humans and mice.
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Affiliation(s)
- Catherine Cheng
- School of Optometry and Vision Science Program, University of California Berkeley, Berkeley, CA 94720, USA
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22
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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] [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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23
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Alapure BV, Stull JK, Firtina Z, Duncan MK. The unfolded protein response is activated in connexin 50 mutant mouse lenses. Exp Eye Res 2012; 102:28-37. [PMID: 22713599 DOI: 10.1016/j.exer.2012.06.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Revised: 04/25/2012] [Accepted: 06/08/2012] [Indexed: 10/28/2022]
Abstract
The unfolded protein response is a set of cell signaling pathways recently recognized to be activated in the lens during both normal development and endoplasmic reticulum stress induced by either unfolded proteins or oxidative damage. While mutations in the gene for connexin 50 are known to cause autosomal dominant cataracts, it has not been previously reported whether mutant connexins can activate the unfolded protein response in the lens. Mice homozygous for the S50P or G22R mutation of connexin 50 have reduced amounts of connexin 50 protein at the cell membrane, with some intracellular staining consistent with retention in the endoplasmic reticulum. Connexin 50 mutants have elevated levels of BiP expression in both lens epithelial and fiber cells from E15.5 with the most robust elevation detected in newborns. While this elevation decreases in magnitude postnatally, BiP expression is still abnormally high in adults, particularly in the perinuclear endoplasmic reticulum of cell nuclei that are inappropriately retained in adult homozygous mutant lenses. Xbp1 splicing was elevated in lenses from both connexin mutants studied, while Atf4 and Atf6 levels were not majorly affected. Overall, these data suggest that UPR may be a contributing factor to the phenotype of connexin 50 mutant lenses even though the relatively modest extent of the response suggests that it is unlikely to be a major driver of the pathology.
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Affiliation(s)
- Bhagwat V Alapure
- Department of Biological Sciences, University of Delaware, 327 Wolf Hall, The Green, Newark, DE 19716, USA
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24
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Vaghefi E, Walker K, Pontre BP, Jacobs MD, Donaldson PJ. Magnetic resonance and confocal imaging of solute penetration into the lens reveals a zone of restricted extracellular space diffusion. Am J Physiol Regul Integr Comp Physiol 2012; 302:R1250-9. [DOI: 10.1152/ajpregu.00611.2011] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
It has been proposed that in the absence of blood supply, the ocular lens operates an internal microcirculation system that delivers nutrients to internalized fiber cells faster and more efficiently than would occur by passive diffusion alone. To visualize the extracellular space solute fluxes potentially generated by this system, bovine lenses were organ cultured in artificial aqueous humor (AAH) for 4 h in the presence or absence of two gadolinium-based contrast agents, ionic Gd3+, or a chelated form of Gd3+, Gd-diethylenetriamine penta-acetic acid (Gd-DTPA; mol mass = 590 Da). Contrast reagent penetration into the lens core was monitored in real time using inversion recovery-spin echo (IR-SE) magnetic resonance imaging (MRI), while steady-state accumulation of [Gd-DTPA]−2 was also determined by calculating T1 values. After incubation, lenses were fixed and cryosectioned, and sections were labeled with the membrane marker wheat germ agglutinin (WGA). Sections were imaged by confocal microscopy using standard and reflectance imaging modalities to visualize the fluorescent WGA label and gadolinium reagents, respectively. Real-time IR-SE MRI showed rapid penetration of Gd3+ into the outer cortex of the lens and a subsequent bloom of signal in the core. These two areas of signal were separated by an area in the inner cortex that limited entry of Gd3+. Similar results were obtained for Gd-DTPA, but the penetration of the larger negatively charged molecule into the core could only be detected by calculating T1 values. The presence of Gd-DTPA in the extracellular space of the outer cortex and core, but its apparent absence from the inner cortex was confirmed using reflectance imaging of equatorial sections. In axial sections, Gd-DTPA was associated with the sutures, suggesting these structures provide a pathway from the surface, across the inner cortex barrier to the lens core. Our studies have revealed inner and outer boundaries of a zone within which a narrowing of the extracellular space restricts solute diffusion and acts to direct fluxes into the lens core via the sutures.
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Affiliation(s)
- Ehsan Vaghefi
- Department of Optometry and Vision Sciences, New Zealand National Eye Centre, University of Auckland, New Zealand
- Auckland Bioengineering Institute, University of Auckland, New Zealand
| | - Kerry Walker
- Department of Optometry and Vision Sciences, New Zealand National Eye Centre, University of Auckland, New Zealand
| | - Beau P. Pontre
- Centre for Advanced MRI, University of Auckland, New Zealand; and
| | - Marc D. Jacobs
- Auckland Bioengineering Institute, University of Auckland, New Zealand
| | - Paul J. Donaldson
- Department of Optometry and Vision Sciences, New Zealand National Eye Centre, University of Auckland, New Zealand
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25
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Nowak RB, Fowler VM. Tropomodulin 1 constrains fiber cell geometry during elongation and maturation in the lens cortex. J Histochem Cytochem 2012; 60:414-27. [PMID: 22473940 DOI: 10.1369/0022155412440881] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Lens fiber cells exhibit a high degree of hexagonal packing geometry, determined partly by tropomodulin 1 (Tmod1), which stabilizes the spectrin-actin network on lens fiber cell membranes. To ascertain whether Tmod1 is required during epithelial cell differentiation to fiber cells or during fiber cell elongation and maturation, the authors quantified the extent of fiber cell disorder in the Tmod1-null lens and determined locations of disorder by confocal microscopy and computational image analysis. First, nearest neighbor analysis of fiber cell geometry in Tmod1-null lenses showed that disorder is confined to focal patches. Second, differentiating epithelial cells at the equator aligned into ordered meridional rows in Tmod1-null lenses, with disordered patches first observed in elongating fiber cells. Third, as fiber cells were displaced inward in Tmod1-null lenses, total disordered area increased due to increased sizes (but not numbers) of individual disordered patches. The authors conclude that Tmod1 is required first to coordinate fiber cell shapes and interactions during tip migration and elongation and second to stabilize ordered fiber cell geometry during maturation in the lens cortex. An unstable spectrin-actin network without Tmod1 may result in imbalanced forces along membranes, leading to fiber cell rearrangements during elongation, followed by propagation of disorder as fiber cells mature.
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Gutierrez DB, Garland D, Schey KL. Spatial analysis of human lens aquaporin-0 post-translational modifications by MALDI mass spectrometry tissue profiling. Exp Eye Res 2011; 93:912-20. [PMID: 22036630 DOI: 10.1016/j.exer.2011.10.007] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2011] [Revised: 10/17/2011] [Accepted: 10/17/2011] [Indexed: 10/16/2022]
Abstract
Aquaporin-0 (AQP0), the major integral membrane protein in lens fiber cells, becomes highly modified with increasing age. The functional consequences of these modifications are being revealed, and the next step is to determine how these modifications affect the ocular lens, which is directly related to their abundances and spatial distributions. The aim of this study was to utilize matrix-assisted laser desorption ionization (MALDI) direct tissue profiling methods, which produce spatially-resolved protein profiles, to map and quantify AQP0 post-translational modifications (PTMs). Direct tissue profiling was performed using frozen, equatorial human lens sections of various ages prepared by conditions optimized for MALDI mass spectrometry profiling of membrane proteins. Modified forms of AQP0 were identified and further investigated using liquid chromatography tandem mass spectrometry (LC-MS/MS). The distributions of unmodified, truncated, and oleoylated forms of AQP0 were examined with a maximum spatial resolution of 500 μm. Direct tissue profiling of intact human lens sections provided high quality, spatially-resolved, relative quantitative information of AQP0 and its modified forms indicating that 50% of AQP0 is truncated at a fiber cell age of 24 ± 1 year in all lenses examined. Furthermore, direct tissue profiling also revealed previously unidentified AQP0 modifications including N-terminal acetylation and carbamylation. N-terminal acetylation appears to provide a protective effect against N-terminal truncation.
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Affiliation(s)
- Danielle B Gutierrez
- Laboratory of Retinal Cell and Molecular Biology, National Eye Institute, National Institutes of Health, MD, USA
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Schonthaler HB, Franz-Odendaal TA, Hodel C, Gehring I, Geisler R, Schwarz H, Neuhauss SCF, Dahm R. The zebrafish mutant bumper shows a hyperproliferation of lens epithelial cells and fibre cell degeneration leading to functional blindness. Mech Dev 2010; 127:203-19. [PMID: 20117205 DOI: 10.1016/j.mod.2010.01.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2009] [Revised: 01/25/2010] [Accepted: 01/26/2010] [Indexed: 10/19/2022]
Abstract
The development of the eye lens is one of the classical paradigms of induction during embryonic development in vertebrates. But while there have been numerous studies aimed at discovering the genetic networks controlling early lens development, comparatively little is known about later stages, including the differentiation of secondary lens fibre cells. The analysis of mutant zebrafish isolated in forward genetic screens is an important way to investigate the roles of genes in embryogenesis. In this study we describe the zebrafish mutant bumper (bum), which shows a transient, tumour-like hyperproliferation of the lens epithelium as well as a progressively stronger defect in secondary fibre cell differentiation, which results in a significantly reduced lens size and ectopic location of the lens within the neural retina. Interestingly, the initial hyperproliferation of the lens epithelium in bum spontaneously regresses, suggesting this mutant as a valuable model to study the molecular control of tumour progression/suppression. Behavioural analyses demonstrate that, despite a morphologically normal retina, larval and adult bum(-/-) zebrafish are functionally blind. We further show that these fish have defects in their craniofacial skeleton with normal but delayed formation of the scleral ossicles within the eye, several reduced craniofacial bones resulting in an abnormal skull shape, and asymmetric ectopic bone formation within the mandible. Genetic mapping located the mutation in bum to a 4cM interval on chromosome 7 with the closest markers located at 0.2 and 0cM, respectively.
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Affiliation(s)
- Helia B Schonthaler
- Max Planck Institute for Developmental Biology, Department of Genetics, Spemannstr. 35, D-72076 Tübingen, Germany
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28
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Vaghefi E, Pontre B, Donaldson PJ, Hunter PJ, Jacobs MD. Visualization of transverse diffusion paths across fiber cells of the ocular lens by small animal MRI. Physiol Meas 2009; 30:1061-73. [PMID: 19738316 DOI: 10.1088/0967-3334/30/10/007] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The sense of vision requires that light penetrate through the ocular lens. Experiments, performed and published by many research groups, have suggested that the lens, which has no blood vessels, relies on internally directed ion and water fluxes for its circulation, survival and transparency. We investigated the internal diffusive pathways of the lens in order to better understand the constraints that may be operating on directional lens fluxes. Small animal magnetic resonance imaging, including T2-weighted and diffusion tensor imaging, was used to measure tissue properties and diffusivity throughout cultured bovine lenses. A range of concentric regions of signal intensity was distinguished inside the lens, by both T2-weighted signal and mean diffusivity. Diffusivity mapping of the lens revealed novel anisotropic polar and equatorial zones of pronounced diffusivity directed transverse to the fiber cells. In contrast, an inner zone including the lens nucleus showed isotropic and weak diffusivity. Our results lend support to models of internally directed lens micro-circulation, by placing non-structural diffusive constraints on global patterns of fluid circulation.
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Affiliation(s)
- Ehsan Vaghefi
- Auckland Bioengineering Institute, The University of Auckland, Auckland, New Zealand
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29
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Kong CW, Gerometta R, Alvarez LJ, Candia OA. Changes in rabbit and cow lens shape and volume upon imposition of anisotonic conditions. Exp Eye Res 2009; 89:469-78. [PMID: 19427852 DOI: 10.1016/j.exer.2009.04.013] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2008] [Revised: 04/28/2009] [Accepted: 04/28/2009] [Indexed: 10/20/2022]
Abstract
In vivo, mammalian lenses have the capacity to effect fully reversible changes in shape, and possibly volume, during the accommodation process. Isolated lenses also change shape by readily swelling or shrinking when placed in anisotonic media. However, the manner by which the lens changes its shape when its volume is changed osmotically is not firmly established. Putatively, the lens could swell or shrink evenly in all directions, or manifest distinctive swelling and/or shrinking patterns when exposed to anisotonic media. The present study measured physical changes in lenses consistent with the latter alternative using methods we developed for determining rapid changes in lens shape and volume. It was found in isolated rabbit and cow lenses that the length of the axis between the anterior and posterior poles (A-P length) primarily increases under hypotonic conditions (-40 to -100 mOsM), with smaller, or no changes, in equatorial diameter (ED). Hypertonic conditions (+50 to +100 mOsM) on rabbit lenses elicited a predominant reduction in ED, while the A-P length was only marginally reduced. Hypertonic solutions of +150 mOsM were required to obtain similar changes in cow lens shape. The ratio of the A-P length to the ED was taken as a measure of "circularity". This ratio increased gradually in rabbit and cow lenses bathed in hypotonic solutions because of the increase in the A-P length. The calculated lens volume increased in tandem with the increase in "circularity". Lens circularity also increased under hypertonic conditions due to the decrease in ED, but this increase in circularity during shrinkage was not as pronounced as that which occurred during swelling. As such, the lens has a tendency upon swelling to change its shape by approaching the structure of a globular spheroid (as occurs during accommodation for near focusing), but lens shrinkage does not result in a flatter lens with a reduced A-P length as occurs during dis-accommodation for distance focusing. Moreover, osmotically evoked shape changes appear irreversible, in contrast to the mechanically elicited shape changes of accommodation.
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Affiliation(s)
- Chi-Wing Kong
- Department of Ophthalmology, Mount Sinai School of Medicine, 100th Street and 5th Avenue, New York, NY 10029, USA.
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30
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Basic Science of the Lens. Ophthalmology 2009. [DOI: 10.1016/b978-0-323-04332-8.00057-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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31
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Chepelinsky AB. Structural function of MIP/aquaporin 0 in the eye lens; genetic defects lead to congenital inherited cataracts. Handb Exp Pharmacol 2008:265-97. [PMID: 19096783 DOI: 10.1007/978-3-540-79885-9_14] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Aquaporin 0 (AQP0) was originally characterized as a membrane intrinsic protein, specifically expressed in the lens fibers of the ocular lens and designated MIP, for major intrinsic protein of the lens. Once the gene was cloned, an internal repeat was identified, encoding for the amino acids Asp-Pro-Ala, the NPA repeat. Shortly, the MIP gene family was emerging, with members being characterized in mammals, insects, and plants. Once Peter Agre's laboratory developed a functional assay for water channels, the MIP family became the aquaporin family and MIP became known as aquaporin 0. Besides functioning as a water channel, aquaporin 0 also plays a structural role, being required for maintaining the transparency and optical accommodation of the ocular lens. Mutations in the AQP0 gene in human and mice result in genetic cataracts; deletion of the MIP/AQP0 gene in mice results in lack of suture formation required for maintenance of the lens fiber architecture, resulting in perturbed accommodation and focus properties of the ocular lens. Crystallography studies support the notion of the double function of aquaporin 0 as a water channel (open configuration) or adhesion molecule (closed configuration) in the ocular lens fibers. The functions of MIP/AQP0, both as a water channel and an adhesive molecule in the lens fibers, contribute to the narrow intercellular space of the lens fibers that is required for lens transparency and accommodation.
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Affiliation(s)
- Ana B Chepelinsky
- National Institutes of Health, National Eye Institute, Bldg. 31, Room 6A-32, Bethesda, MD, 20892-2510, USA.
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Chen X, Taube JR, Simirskii VI, Patel TP, Duncan MK. Dual roles for Prox1 in the regulation of the chicken betaB1-crystallin promoter. Invest Ophthalmol Vis Sci 2008; 49:1542-52. [PMID: 18385074 DOI: 10.1167/iovs.07-1300] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Lens fiber cell differentiation is marked by the onset of betaB1-crystallin expression and is controlled by the cooperative action of a set of transcription factors including Prox1, an atypical homeodomain protein. Previously, the authors reported that Prox1 directly interacts with the OL2 element found in the chicken betaB1-crystallin basal promoter to activate the expression of this gene. Here they mapped the location of activating and repressing sequences of the full-length chicken betaB1-crystallin promoter (-432/+30) in lens epithelial cells, annular pad cells, and intact lens and characterized Prox1-binding sites found in this region. METHODS Transfection analysis and transgenic mice were used to characterize upstream regions of the chicken betaB1-crystallin gene. DNaseI footprinting and chromatin immunoprecipitation was performed to identify Prox1-binding sites, and transfection analyses were used to characterize these sites functionally. RESULTS Sequences between -152 and -432 of the chicken betaB1-crystallin promoter mediated either promoter activation or repression, depending on the stage of lens differentiation tested. Two new Prox1-binding sites were found in this region that bound Prox1 more avidly than the OL2 element. However, neither binding site conferred Prox1-mediated activation on a heterologous promoter; instead, each allowed Prox1 to repress promoter function. CONCLUSIONS The function of the upstream region of the chicken betaB1-crystallin promoter changes depending on cellular context. These data suggest that Prox1 function as a transcriptional activator could be regulated at the DNA level based on the characteristics of the responsive elements.
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Affiliation(s)
- Xiaoren Chen
- Department of Biological Sciences, University of Delaware, Newark, Delaware 19716, USA
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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: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [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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O'Connor MD, Wederell ED, de Iongh R, Lovicu FJ, McAvoy JW. Generation of transparency and cellular organization in lens explants. Exp Eye Res 2008; 86:734-45. [PMID: 18343368 DOI: 10.1016/j.exer.2008.01.020] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2007] [Revised: 01/02/2008] [Accepted: 01/29/2008] [Indexed: 10/22/2022]
Abstract
The lens grows via the proliferation and differentiation of lens epithelial cells into lens fibres. This differentiation process, thought to be controlled by factors present in the vitreous fluid, generates tightly-packed, parallel-aligned fibre cells that confer transparency to the lens. Using lens epithelial-cell explants we examined how explant orientation and growth factor treatment can affect cellular arrangement and explant transparency. Fibre cell differentiation was induced in lens explants by culturing cells with fibroblast growth factor (FGF) or bovine vitreous. Cell shape and arrangement was investigated using confocal microscopy, electron microscopy, immunofluorescence and in situ hybridization. Explant transparency was measured using light microscopy. Confocal microscopy demonstrated that explant orientation determined cellular arrangement, irrespective of the differentiation stimuli used. In explants where epithelial cells were confined between their normal basement membrane (the lens capsule) and the base of the culture dish, the cells became elongated, thin and parallel-aligned. In contrast, in explants cultured with cells directly exposed to the culture media the cells appeared to be shorter, globular and haphazardly arranged. FGF initiated the differentiation of most lens epithelial cells; however, abnormal cellular morphologies developed with subsequent culture of the cells. As a result, the transparency of these explants decreased with prolonged culture. Interestingly, explants cultured with vitreous (i) did not develop abnormal cellular morphologies, (ii) contained two distinct cell types (retained epithelial cells and newly differentiated fibre cells) and (iii) remained transparent throughout the lengthy culture period. In summary, we have developed a culture system that generates a transparent tissue with a cellular arrangement resembling that of the lens in vivo. We have shown that while FGF and vitreous initiate differentiation within this system, better maintenance of fibre cell integrity, more appropriate regulation of molecular events, and better maintenance of explant transparency was achieved in the presence of vitreous. This system offers an opportunity to further investigate the process of lens fibre cell differentiation as well as a means of better identifying the factors that contribute to the development of tissue transparency in vitro.
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Affiliation(s)
- Michael D O'Connor
- Save Sight Institute and Department of Clinical Ophthalmology & Eye Health, The University of Sydney, Sydney, NSW 2006, Australia.
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35
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Dahm R, Procter JE, Ireland ME, Lo WK, Mogensen MM, Quinlan RA, Prescott AR. Reorganization of centrosomal marker proteins coincides with epithelial cell differentiation in the vertebrate lens. Exp Eye Res 2007; 85:696-713. [PMID: 17888905 DOI: 10.1016/j.exer.2007.07.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2007] [Revised: 07/26/2007] [Accepted: 07/31/2007] [Indexed: 12/24/2022]
Abstract
The differentiation of epithelial cells in the vertebrate lens involves a series of changes that includes the degradation of all intracellular organelles and a dramatic elongation of the cells. The latter is accompanied by a substantial remodelling of the cytoskeleton and changes in the distribution of the actin, microtubule and intermediate filament cytoskeletons during lens cell differentiation have been well documented. There have, however, been no studies of microtubule organizing centres (MTOCs) and specifically centrosomes during lens cell differentiation. We have investigated the fate of the centrosomal MTOCs during cellular differentiation in the bovine lens using gamma-tubulin, ninein, centrin 2 and centrin 3 as markers. Our studies show that these markers oscillate between a clear centrosome-based association in epithelial cells and a defocused cluster in lens fibre cells. Our data further reveal a transient loss of signal for the typical centrosomal marker gamma-tubulin as the lens epithelial cells begin to differentiate into lens fibre cells. This marker apparently disappears in the most distal epithelial cells at the lens equator, only to reappear in early lens fibre cells. The changes in gamma-tubulin distribution are mirrored by the other centrosomal markers, centrins 2 and 3 and ninein that also show a similar transient loss of their signals and subsequent clustering at the apical ends of differentiating fibre cells. The transient loss of staining for these centrosomal markers in the most posterior epithelial cells is a distinctive feature that precedes lens cell elongation. The dramatic reorganization of MTOC markers coincides with gap junction reorganization as seen by the loss of connexin 43 (alpha1-connexin) in these lens epithelial cells suggesting that these events mark a significant change preceding subsequent cell elongation and differentiation into fibre cells.
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Affiliation(s)
- Ralf Dahm
- Department of Biochemistry, Medical Sciences Institute, University of Dundee, Dundee, DD1 4HN, UK.
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36
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Gerometta R, Zamudio AC, Escobar DP, Candia OA. Volume change of the ocular lens during accommodation. Am J Physiol Cell Physiol 2007; 293:C797-804. [PMID: 17537805 DOI: 10.1152/ajpcell.00094.2007] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
During accommodation, mammalian lenses change shape from a rounder configuration (near focusing) to a flatter one (distance focusing). Thus the lens must have the capacity to change its volume, capsular surface area, or both. Because lens topology is similar to a torus, we developed an approach that allows volume determination from the lens cross-sectional area (CSA). The CSA was obtained from photographs taken perpendicularly to the lenticular anterior-posterior (A-P) axis and computed with software. We calculated the volume of isolated bovine lenses in conditions simulating accommodation by forcing shape changes with a custom-built stretching device in which the ciliary body-zonulae-lens complex (CB-Z-L) was placed. Two measurements were taken (CSA and center of mass) to calculate volume. Mechanically stretching the CB-Z-L increased the equatorial length and decreased the A-P length, CSA, and lens volume. The control parameters were restored when the lenses were stretched and relaxed in an aqueous physiological solution, but not when submerged in oil, a condition with which fluid leaves the lens and does not reenter. This suggests that changes in lens CSA previously observed in humans could have resulted from fluid movement out of the lens. Thus accommodation may involve changes not only in capsular surface but also in volume. Furthermore, we calculated theoretical volume changes during accommodation in models of human lenses using published structural parameters. In conclusion, we suggest that impediments to fluid flow between the aquaporin-rich lens fibers and the lens surface could contribute to the aging-related loss of accommodative power.
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Affiliation(s)
- R Gerometta
- Dept of Ophthalmology, Mount Sinai School of Medicine, One Gustave L Levy Place, New York, NY 10029, USA
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37
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Maddala R, Skiba N, Vasantha Rao P. Lens fiber cell elongation and differentiation is associated with a robust increase in myosin light chain phosphorylation in the developing mouse. Differentiation 2007; 75:713-25. [PMID: 17459090 DOI: 10.1111/j.1432-0436.2007.00173.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Myosin II, a molecular motor, plays a critical role in cell migration, cell shape changes, cell adhesion, and cytokinesis. To understand the role of myosin II in lens fiber cell elongation and differentiation, we determined the distribution pattern of nonmuscle myosin IIA, IIB, and phosphorylated regulatory myosin light chain-2 (phospho-MLC) in frozen sections of the developing mouse lens by immunofluorescence analysis. While myosin IIA was distributed uniformly throughout the differentiating lens, including the epithelium and fibers, myosin IIB was localized predominantly to the epithelium and the posterior tips of the lens fibers. In contrast, immunostaining with a di-phospho-MLC antibody localized intensely and precisely to the elongating and differentiating primary and secondary lens fibers, co-localizing with actin filaments. An in situ analysis of Rho GTPase activation revealed that Rho-GTP was distributed uniformly throughout the embryonic lens, including epithelium and fibers. Inhibition of myosin light chain kinase (MLCK) activity by ML-7 in organ cultured mouse lenses led to development of nuclear lens opacity in association with abnormal fiber cell organization. Taken together, these data reveal a distinct spatial distribution pattern of myosin II isoforms in the developing lens and a robust activation of MLC phosphorylation in the differentiating lens fibers. Moreover, the regulation of MLC phosphorylation by MLCK appears to be critical for crystallin organization and for maintenance of lens transparency and lens membrane function.
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Affiliation(s)
- Rupalatha Maddala
- Department of Ophthalmology, Duke University School of Medicine, Box 3802, Erwin Road, Durham, North Carolina 27710, USA
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Dunia I, Cibert C, Gong X, Xia CH, Recouvreur M, Levy E, Kumar N, Bloemendal H, Benedetti EL. Structural and immunocytochemical alterations in eye lens fiber cells from Cx46 and Cx50 knockout mice. Eur J Cell Biol 2006; 85:729-52. [PMID: 16740340 DOI: 10.1016/j.ejcb.2006.03.006] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2005] [Revised: 03/02/2006] [Accepted: 03/07/2006] [Indexed: 11/28/2022] Open
Abstract
In the current study we describe the changes of overall organization of lens fiber cells in connexin 46 (Cx46) and connexin 50 (Cx50) knockout mice. Morphometric analyses and the application of immunocytochemical techniques revealed that in Cx46 knockout lens (Cx46 -/-), where Cx50 is expressed alone, the postnatal differentiation of secondary fiber cells proceeds faster and is characterized by an increased number of smaller fiber cells. Conversely, in Cx50 knockout mice (Cx50 -/-), the lenticular mass is considerably reduced and characterized by a small number of fiber cells added during the postnatal period. The process of terminal differentiation was impaired and generated larger fiber cells still possessing cytoplasmic organelles. Freeze-fracture and fracture labeling revealed that the junctional assembly, packing organization and topographic interactions between connexons and MP26 differed when Cx46 and Cx50 were co-assembled in the wild-type or expressed separately in the two distinct knockout phenotypes. Filipin cytochemistry provided indirect evidence that Cx46 and Cx50 expressed alone are recruited into different lipid environments. Our results represent the structural proof that interaction of connexins and MP26 contributes to the overall organization of the fiber cells.
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Affiliation(s)
- Irene Dunia
- Biologie Cellulaire, Institut Jacques Monod, CNRS, Universités Paris 6-Paris 7, 2, place Jussieu, F-75251 Paris Cedex 5, France.
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Castellini M, Wolf LV, Chauhan BK, Galileo DS, Kilimann MW, Cvekl A, Duncan MK. Palm is expressed in both developing and adult mouse lens and retina. BMC Ophthalmol 2005; 5:14. [PMID: 15969763 PMCID: PMC1183217 DOI: 10.1186/1471-2415-5-14] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2005] [Accepted: 06/21/2005] [Indexed: 11/30/2022] Open
Abstract
Background Paralemmin (Palm) is a prenyl-palmitoyl anchored membrane protein that can drive membrane and process formation in neurons. Earlier studies have shown brain preferred Palm expression, although this protein is a major water insoluble protein in chicken lens fiber cells and the Palm gene may be regulated by Pax6. Methods The expression profile of Palm protein in the embryonic, newborn and adult mouse eye as well as dissociated retinal neurons was determined by confocal immunofluorescence. The relative mRNA levels of Palm, Palmdelphin (PalmD) and paralemmin2 (Palm2) in the lens and retina were determined by real time rt-PCR. Results In the lens, Palm is already expressed at 9.5 dpc in the lens placode, and this expression is maintained in the lens vesicle throughout the formation of the adult lens. Palm is largely absent from the optic vesicle but is detectable at 10.5 dpc in the optic cup. In the developing retina, Palm expression transiently upregulates during the formation of optic nerve as well as in the formation of both the inner and outer plexiform layers. In short term dissociated chick retinal cultures, Palm protein is easily detectable, but the levels appear to reduce sharply as the cultures age. Palm mRNA was found at much higher levels relative to Palm2 or PalmD in both the retina and lens. Conclusion Palm is the major paralemmin family member expressed in the retina and lens and its expression in the retina transiently upregulates during active neurite outgrowth. The expression pattern of Palm in the eye is consistent with it being a Pax6 responsive gene. Since Palm is known to be able to drive membrane formation in brain neurons, it is possible that this molecule is crucial for the increase in membrane formation during lens fiber cell differentiation.
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Affiliation(s)
- Meryl Castellini
- Department of Biological Sciences, University of Delaware, Newark, DE 19716 USA
- Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University, Philadelphia, PA 19107 USA
| | - Louise V Wolf
- Depts. of Ophthalmology and Visual Sciences and Molecular Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA
| | - Bharesh K Chauhan
- Depts. of Ophthalmology and Visual Sciences and Molecular Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA
- Developmental Biology Division and Department of Ophthalmology, Children's Hospital Research Foundation, 3333 Burnet Avenue, Cincinnati, OH 45229 USA
| | - Deni S Galileo
- Department of Biological Sciences, University of Delaware, Newark, DE 19716 USA
| | - Manfred W Kilimann
- Department of Cell and Molecular Biology, Uppsala University, S-75124 Uppsala Sweden
| | - Ales Cvekl
- Depts. of Ophthalmology and Visual Sciences and Molecular Genetics, Albert Einstein College of Medicine, Bronx, NY 10461 USA
| | - Melinda K Duncan
- Department of Biological Sciences, University of Delaware, Newark, DE 19716 USA
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40
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Segev F, Mor O, Segev A, Belkin M, Assia EI. Downregulation of gene expression in the ageing lens: a possible contributory factor in senile cataract. Eye (Lond) 2005; 19:80-5. [PMID: 15105821 DOI: 10.1038/sj.eye.6701423] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
PURPOSE To study the molecular characteristics of lens epithelial cells from patients with senile cataract by cDNA microarray technique. METHODS Lens epithelial cells adhering to anterior capsules taken during cataract surgery collected from 108 patients, aged 56-92 years (senile cataract group), were pooled. Pooled epithelial cells of normal, noncataractous lenses from one patient with ocular trauma, one patient with lens subluxation, and 25 cadaveric eyes, all under the age of 55 years, served as a control. Total RNA was extracted by conventional methods from the two groups of cells, and a fluorescent probe was prepared for each group. The probes were hybridized on 9700 known human cDNA clones. Hybridized clones were analysed using a scanning laser and the results were processed by GEMTools (Incyte Genomics) software. RESULTS A total of 1827 clones hybridized with the two probes. Of these, 400 showed differences of more than two-fold in gene expression between the two probes. Relative to controls, gene expression in the senile cataract lenses was upregulated in 318 clones and downregulated in 82. Three genes-filensin, inwardly rectifying potassium channel (IRPC), and pigment epithelium-derived factor (PEDF) were strongly downregulated (by 41.3-, 6.8-, and 5.9-fold, respectively) in senile cataract. CONCLUSIONS Cataractogenesis is associated with numerous changes in the genetic profile of the lens epithelial cells. Since filensin, IRPC, and PEDF genes are known to have important roles in the physiology and morphology of the transparent lens, substantial downregulation of their expression might contribute to the formation of senile cataract.
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Affiliation(s)
- F Segev
- Department of Ophthalmology, Meir Hospital, Sapir Medical Center, Kfar-Saba, Israel.
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Abstract
Accommodation in humans refers to the ability of the lens to change shape in order to bring near objects into focus. Accommodative loss begins during childhood, with symptomatic presbyopia, or presbyopia that affects one's day to day activities, striking during midlife. While symptomatic presbyopia has traditionally been treated with reading glasses or contact lenses, a number of surgical interventions and devices are being actively developed in an attempt to restore at least some level of accommodation. This is occurring at a time when the underlying cause of presbyopia remains unknown, and even the mechanism of accommodation is occasionally debated. While Helmholtz' theory regarding the mechanism of accommodation is generally accepted with regard to broad issues, additional details continue to emerge. Age-related changes in anterior segment structures associated with accommodation have been documented, often through in vitro and/or rhesus monkey studies. A review of these findings suggests that presbyopia develops very differently in humans compared to non-human primates. Focusing on non-invasive in vivo human imaging technologies, including Scheimpflug photography and high-resolution magnetic resonance imaging (MRI), the data suggest that the human uveal tract acts as a unit in response to age-related increasing lens thickness and strongly implicates lifelong lens growth as the causal factor in the development of presbyopia.
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Affiliation(s)
- Susan A Strenk
- Department of Surgery, Robert Wood Johnson Medical School-University of Medicine and Dentistry of New Jersey, Piscataway, NJ 08855, USA
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42
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Perng MD, Sandilands A, Kuszak J, Dahm R, Wegener A, Prescott AR, Quinlan RA. The intermediate filament systems in the eye lens. Methods Cell Biol 2005; 78:597-624. [PMID: 15646633 DOI: 10.1016/s0091-679x(04)78021-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Affiliation(s)
- Ming Der Perng
- School of Biological and Biomedical Sciences, The University of Durham, Durham DH1 3LE, UK
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43
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Kennedy BN, Stearns GW, Smyth VA, Ramamurthy V, van Eeden F, Ankoudinova I, Raible D, Hurley JB, Brockerhoff SE. Zebrafish rx3 and mab21l2 are required during eye morphogenesis. Dev Biol 2004; 270:336-49. [PMID: 15183718 DOI: 10.1016/j.ydbio.2004.02.026] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2003] [Revised: 02/20/2004] [Accepted: 02/25/2004] [Indexed: 10/26/2022]
Abstract
Two alleles of an eyeless mutant, chokh (chk), were identified in ongoing zebrafish F(3) mutagenesis screens. Morphologically, chk mutants can be identified at 15 h post-fertilization by the failure of optic primordia to evaginate from the forebrain. The chk phenotype appears specific, as marker genes in the forebrain, midbrain, and pineal are expressed in normal temporal, spatial, and circadian patterns. Sequence analysis of the chk alleles revealed nonsense or missense mutations in the rx3 homeobox. Rx genes encode paired-type homeodomain transcription factors known to be key regulators of eye development in mouse, medaka, Xenopus, and zebrafish. To uncover novel Rx targets, we analyzed the expression of multiple eye development genes in chk. We find that expression of mab21l2, mab21l1 and rx2 are specifically absent in the eye field of chk embryos. Knockdown of Mab21l2 by antisense morpholino microinjections partially phenocopies the rx3 mutation, leading to microphthalmia, incomplete eye maturation, and dramatic increases in apoptotic eye progenitors. We propose that mab21l2 is an early downstream effector of rx3 and is critical for survival of eye progenitors.
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Affiliation(s)
- Breandán N Kennedy
- Department of Biochemistry, University of Washington, Seattle, WA 98195, USA.
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44
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Foley JD, Rosenbaum H, Griep AE. Temporal regulation of VEID-7-amino-4-trifluoromethylcoumarin cleavage activity and caspase-6 correlates with organelle loss during lens development. J Biol Chem 2004; 279:32142-50. [PMID: 15161922 DOI: 10.1074/jbc.m313683200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Lens fiber cell differentiation involves extensive reconstruction of the cell's architecture, including the degradation and elimination of all membrane-bound organelles via a process that has been likened to apoptosis. Using caspase reporter assays under conditions in which nonspecific cleavage of the reporter peptides by the proteasome has been inhibited, we investigated whether any specific caspase activities are temporally correlated with this process of organelle loss. Extracts from neonatal mouse lenses contained strong VEID-7-amino-4-trifluoromethylcoumarin (AFC) and minor IETD-AFC and LEVD-AFC cleavage activities, but no DEVD-AFC cleavage activity. Further testing suggested that the VEID-AFC and IETD-AFC cleavage activities were likely due to the same enzyme. In lens extracts from rat embryos, VEID-AFC cleavage activity increased during the period when organelles are eliminated, between embryonic days 15.5 and 18.5, whereas procaspase-6 protein levels decreased, suggesting that this enzyme is responsible for VEID-AFC cleavage. By contrast, in extracts from alpha AE7 transgenic mouse lenses in which apoptosis was induced, strong DEVD-AFC cleavage activity and activated caspase-3 protein were detected. Thus, within the same tissue, different caspase activities can predominate depending on the context, normal differentiation versus apoptosis. These results highlight the difference between normal fiber cell differentiation and apoptosis and the capacity of the lens to differentially regulate these two processes.
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Affiliation(s)
- John D Foley
- Department of Anatomy, University of Wisconsin Medical School, Madison, 53706, USA
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45
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Abstract
Epidemiological studies have indicated that ultraviolet radiation (UVR) is one of the main factors leading to senile cataract formation. We investigated morphological changes in the eye lens caused by UVR-A. Twenty three pairs of lenses obtained from 23 one-year-old calves were used for this study. For each pair, one lens was exposed to 44 J/m(2) UVR in the 365 nm wavelength region while the contralateral lens was not exposed and served as a control. The lenses were placed in specially designed organ culture containers for pre-incubation. Lenses were exposed to UVR after one day in culture. After irradiation, lens optical quality was monitored throughout additional 15 days of the culture period and lenses were taken for morphological analysis by scanning electron microscopy. Damage to lens optical quality was evident as early as day 8 after the irradiation and increased with time in culture. We found irregularity of fiber morphology in lenses exposed to UV-A irradiation (but not in control lenses), similar to that reported previously for aged lenses. At the end of the culture period (day 16), lens fiber membranes also showed holes in fiber membranes. We conclude that UVR-A caused damage to cell membranes of the lens and alterations in lens optics, which may subsequently lead to senile cataract formation.
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Affiliation(s)
- Naiel Azzam
- B. Rappaport Faculty of Medicine, Technion-Israel Institute of Technology, 7 Efron St., P.O. Box 9649, Haifa 31096, Israel
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46
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Guo W, Shang F, Liu Q, Urim L, West-Mays J, Taylor A. Differential regulation of components of the ubiquitin-proteasome pathway during lens cell differentiation. Invest Ophthalmol Vis Sci 2004; 45:1194-201. [PMID: 15037588 PMCID: PMC1446108 DOI: 10.1167/iovs.03-0830] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
PURPOSE To investigate the role for the ubiquitin-proteasome pathway in controlling lens cell proliferation and differentiation and the regulation of the ubiquitin conjugation machinery during the differentiation process. METHODS bFGF-induced lens cell proliferation and differentiation was monitored in rat lens epithelial explants by bromodeoxyuridine (BrdU) incorporation and expression of crystallins and other differentiation markers. Levels of typical substrates for the ubiquitin-proteasome pathway, p21(WAF) and p27(Kip), were monitored during the differentiation process, as were levels and activities of the enzymes involved in ubiquitin conjugation. RESULTS Explants treated with bFGF initially underwent enhanced proliferation as indicated by BrdU incorporation. Then they withdrew from the cell cycle as indicated by diminished BrdU incorporation and accumulation of p21(WAF) and p27(Kip). bFGF-induced cell proliferation was prohibited or delayed by proteasome inhibitors. Lens epithelial explants treated with bFGF for 7 days displayed characteristics of lens fibers, including expression of large quantities of crystallins. Whereas levels of E1 remained constant during the differentiation process, the levels of ubiquitin-conjugating enzyme (Ubc)-1 increased approximately twofold, and the thiol ester form of Ubc1 increased approximately threefold on 7 days of bFGF treatment. Levels of Ubc2 increased moderately on bFGF treatment, and most of the Ubc2 was found in the thiol ester form. Although levels of total Ubc3 and -7 remained unchanged, the proportions of Ubc3 and -7 in the thiol ester form were significantly higher in the bFGF-treated explants. Levels of Ubc4/5 and -9 also increased significantly on treatment with bFGF, and more than 90% of Ubc9 was found in the thiol ester form in the bFGF-treated explants. In contrast, levels of Cul1, the backbone of the SCF type of E3s, decreased 50% to 70% in bFGF-treated explants. CONCLUSIONS The data show that proteolysis through the ubiquitin-proteasome pathway is required for bFGF-induced lens cell proliferation and differentiation. Various components of the ubiquitin-proteasome pathway are differentially regulated during lens cell differentiation. The downregulation of Cul1 appears to contribute to the accumulation of p21(WAF) and p27(Kip), which play an important role in establishing a differentiated phenotype.
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Affiliation(s)
- Weimin Guo
- From the Laboratory for Nutrition and Vision Research, Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts; the
| | - Fu Shang
- From the Laboratory for Nutrition and Vision Research, Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts; the
| | - Qing Liu
- From the Laboratory for Nutrition and Vision Research, Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts; the
| | - Lyudmila Urim
- Department of Ophthalmology, New England Medical Center, Boston, Massachusetts; and the
| | - Judith West-Mays
- Department of Pathology and Molecular Medicine, McMaster University, Hamilton, Canada
| | - Allen Taylor
- From the Laboratory for Nutrition and Vision Research, Jean Mayer United States Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts; the
- Corresponding author: Allen Taylor, Laboratory for Nutrition and Vision Research, JMUSDA-HNRCA at Tufts University, Boston, MA 02111;
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47
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Cannell MB, Jacobs MD, Donaldson PJ, Soeller C. Probing microscopic diffusion by 2-photon flash photolysis: measurement of isotropic and anisotropic diffusion in lens fiber cells. Microsc Res Tech 2004; 63:50-7. [PMID: 14677133 DOI: 10.1002/jemt.10422] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Two-photon excited flash photolysis (TPEFP) was used to photorelease caged fluorescein in test solutions and inside fiber cells of the eye lens. Accurate alignment between the focus of the IR beam and the probe beam from the confocal microscope was achieved with an accessory focussing lens and computer models of diffusion were fit to experimental data to extract apparent diffusion coefficients. Inside a fiber cell, the diffusion coefficient for fluorescein was 4 x 10(-7) cm(2)/s at 21 degrees C, a value an order of magnitude lower than observed in free solution. Fluorescence also diffused between fiber cells via gap junctions. In the periphery, diffusion between cells occurred mainly in a radial direction while deep in the lens the diffusion between cells appeared more isotropic. Diffusion between cells was slower than inside cells and corresponded to less than approximately 1% of the area between cells being available for diffusion. This value is in good agreement with that expected from measurements of gap junction structure and packing density if a 1-1.5-nm aqueous gap junction pore is nearly always open.
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Affiliation(s)
- M B Cannell
- Department of Physiology, School of Medicine and Health Sciences, University of Auckland, Auckland, New Zealand.
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Jacobs MD, Donaldson PJ, Cannell MB, Soeller C. Resolving morphology and antibody labeling over large distances in tissue sections. Microsc Res Tech 2003; 62:83-91. [PMID: 12938120 DOI: 10.1002/jemt.10360] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Protein expression patterns are a primary determinant of tissue function and in this study we developed methods to study protein expression over macroscopic distances at subcellular levels of detail. Using the mammalian lens as a model tissue system, we show that by combining two-photon microscopy with novel image montage methods (fast beam blanking coupled with mathematical alignment tools) we have extended the limited field of view of laser scanning microscopes. To illustrate the utility of our approach, the distribution of connexin-46 was visualized across equatorial sections of the rat mammalian lens. By optimizing fixation protocols, good morphological preservation could be achieved over the thickness of the lens (approximately 4 mm) while preserving antigenicity of lens proteins. Using the same image data, changes in lens fiber cell morphology were mapped quantitatively by automatic image analysis routines. The methods presented should be generally applicable to any tissue system where changes in antibody labeling and tissue structure occur over large and small distances.
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Affiliation(s)
- Marc D Jacobs
- Department of Physiology, School of Medical and Health Sciences, The University of Auckland, Auckland, New Zealand
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49
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Al-Ghoul KJ, Kirk T, Kuszak AJ, Zoltoski RK, Shiels A, Kuszak JR. Lens structure in MIP-deficient mice. THE ANATOMICAL RECORD. PART A, DISCOVERIES IN MOLECULAR, CELLULAR, AND EVOLUTIONARY BIOLOGY 2003; 273:714-30. [PMID: 12845708 DOI: 10.1002/ar.a.10080] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this study we used correlative light, scanning, and transmission (freeze-etch) electron microscopy to characterize lens structure in normal mice and compare it with that in mice deficient in the major intrinsic protein (MIP) of fiber cells. Grossly, wild-type lenses were transparent and had typical Y sutures at all of the ages examined. These lenses had fibers of uniform shape (hexagonal in cross section) arranged in ordered concentric growth shells and radial cell columns. In addition, these fibers had normal opposite end curvature and lateral interdigitations regularly arrayed along their length. Ultrastructural evaluation of these fibers revealed anterior and posterior end segments characterized by square array membrane on low-amplitude wavy fiber membrane. Approximately 13% of the equatorial or mid segments of these same fibers were specialized as gap junctions (GJs). In contrast, heterozygote lenses, while initially transparent at birth, were translucent by 3 weeks of age, except for a peripheral transparent region that contained fibers in the early stages of elongation. This degradation in clarity was correlated with abnormal fiber structure. Specifically, although the mid segment of these fibers was essentially normal, their end segments lacked normal opposite end curvature, were larger than normal, and had a distinct non-hexagonal shape. As a result, these fibers failed to form typical Y sutures. Furthermore, the nuclear fibers of heterozygote lenses were even larger and lacked any semblance of an ordered packing arrangement. Grossly, homozygote lenses were opaque at all ages examined, except for a peripheral transparent region that contained fibers in the early stages of elongation. All fibers from homozygote lenses lacked opposite end curvature, and thus failed to form any sutures. Also, these fibers were essentially devoid of interlocking devices, and only 7% of their mid segment was specialized as GJs. The results of this study suggest that MIP has essential roles in the establishment and maintenance of uniform fiber structure, and the organization of fibers, and as such is essential for lens function.
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Affiliation(s)
- Kristin J Al-Ghoul
- Department of Anatomy and Cell Biology, Rush-Presbyterian-St. Luke's Medical Center, Chicago, Illinois 60612, USA
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50
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Sweeney MHJ, Garland DL, Truscott RJW. Movement of cysteine in intact monkey lenses: the major site of entry is the germinative region. Exp Eye Res 2003; 77:245-51. [PMID: 12873456 DOI: 10.1016/s0014-4835(03)00110-6] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Monkey lenses were incubated with 35S-L-cysteine for various times and the movement of label within the lens followed by autoradiography. Cysteine appeared to enter primarily at the germinative region of the lens. No evidence was found for major transport through either the anterior or posterior faces of the lens. The movement of cysteine within different parts of the lens was followed over time. The data suggest that, for cysteine, the major pathway for transport within the lens involves entry at the germinative region followed by movement along the fibre cells. The data were consistent with orthogonal movement across the fibres in the equatorial plane but little or no movement across the fibres at the anterior pole or posterior faces of the lens. Such a scenario is in accord with the distribution of connexons, indicating that this pattern of entry may also be observed for other small molecules. The finding of high permeability at the lens germinative region is in accord with the anatomy of the eye, since this is the lens surface in contact with the posterior chamber. Thus, cysteine secreted by the ciliary body into the aqueous humor would come into contact initially with the region of the lens best able to absorb this amino acid. Although this aspect was not addressed in the current study, the same phenomenon may also be observed with other lens nutrients.
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