1
|
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.
Collapse
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
| |
Collapse
|
2
|
Anderson DMG, Floyd KA, Barnes S, Clark JM, Clark JI, Mchaourab H, Schey KL. A method to prevent protein delocalization in imaging mass spectrometry of non-adherent tissues: application to small vertebrate lens imaging. Anal Bioanal Chem 2015; 407:2311-20. [PMID: 25665708 DOI: 10.1007/s00216-015-8489-5] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2014] [Revised: 01/05/2015] [Accepted: 01/13/2015] [Indexed: 11/29/2022]
Abstract
MALDI imaging requires careful sample preparation to obtain reliable, high-quality images of small molecules, peptides, lipids, and proteins across tissue sections. Poor crystal formation, delocalization of analytes, and inadequate tissue adherence can affect the quality, reliability, and spatial resolution of MALDI images. We report a comparison of tissue mounting and washing methods that resulted in an optimized method using conductive carbon substrates that avoids thaw mounting or washing steps, minimizes protein delocalization, and prevents tissue detachment from the target surface. Application of this method to image ocular lens proteins of small vertebrate eyes demonstrates the improved methodology for imaging abundant crystallin protein products. This method was demonstrated for tissue sections from rat, mouse, and zebrafish lenses resulting in good-quality MALDI images with little to no delocalization. The images indicate, for the first time in mouse and zebrafish, discrete localization of crystallin protein degradation products resulting in concentric rings of distinct protein contents that may be responsible for the refractive index gradient of vertebrate lenses.
Collapse
Affiliation(s)
- David M G Anderson
- Department of Biochemistry, Mass Spectrometry Research Center, Vanderbilt University School of Medicine, Nashville, TN, 37205-0146, USA
| | | | | | | | | | | | | |
Collapse
|
3
|
Optical properties of the lens: an explanation for the zones of discontinuity. Exp Eye Res 2014; 124:93-9. [PMID: 24880144 DOI: 10.1016/j.exer.2014.05.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Revised: 05/09/2014] [Accepted: 05/13/2014] [Indexed: 11/23/2022]
Abstract
The structural basis of zones of discontinuity in the living human eye lens has not been elucidated, and there is no conclusive explanation for what relevance they may have to the structure and function of the lens. Newly developed synchrotron radiation based X-ray Talbot interferometry has enabled the detection of subtle fluctuations in the human eye lens which, when used in mathematical modelling to simulate reflected and scattered light, can recreate the image of the lens seen in the living human eye. The results of this study show that the zones of discontinuity may be caused by subtle fluctuations in the refractive index gradient as well as from random scattering in the central regions. As the refractive index contours are created by cell layers with progressively varying protein concentrations, the zones are linked to growth and will contain information about ageing and development. The index gradient is important for image quality and fluctuations in this gradient may add to quality optimisation and serve as models for designs of new generation implant lenses.
Collapse
|
4
|
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.
Collapse
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:
| |
Collapse
|
5
|
Absence of SPARC leads to impaired lens circulation. Exp Eye Res 2009; 89:416-25. [PMID: 19401199 DOI: 10.1016/j.exer.2009.04.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2008] [Revised: 04/17/2009] [Accepted: 04/17/2009] [Indexed: 11/22/2022]
Abstract
SPARC is a matricellular glycoprotein involved in regulation of extracellular matrix, growth factors, adhesion, and migration. SPARC-null mice have altered basement membranes and develop posterior sub-capsular cataracts with cell swelling and equatorial vacuoles. Exchange of fluid, nutrients, and waste products in the avascular lens is driven by a unique circulating ion current. In the absence of SPARC, increased circulation of fluid, ions, and small molecules led to increased fluorescein distribution in vivo, loss of resting membrane polarization, and altered distribution of small molecules. Microarray analysis of SPARC-null lenses showed changes in gene expression of ion channels and receptors, matrix and adhesion genes, cytoskeleton, immune response genes, and cell signaling molecules. Our results confirm the hypothesis that the regulation of SPARC on cell-capsular matrix interactions can increase the circulation of fluid and ions in the lens, and the phenotype in the SPARC-null mouse lens is the result of multiple intersecting functional pathways.
Collapse
|
6
|
Lens intermediate filaments. Exp Eye Res 2008; 88:165-72. [PMID: 19071112 DOI: 10.1016/j.exer.2008.11.007] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2008] [Revised: 11/04/2008] [Accepted: 11/04/2008] [Indexed: 12/12/2022]
Abstract
The ocular lens assembles two separate intermediate filament systems sequentially with differentiation. Canonical 8-11 nm IFs composed of Vimentin are assembled in lens epithelial cells and younger fiber cells, while the fiber cell-specific beaded filaments are switched on as fiber cell elongation initiates. Some of the key features of both filament systems are reviewed.
Collapse
|
7
|
Yuen J, Li Y, Shapiro LG, Clark JI, Arnett E, Sage EH, Brinkley JF. Automated, computerized, feature-based phenotype analysis of slit lamp images of the mouse lens. Exp Eye Res 2008; 86:562-75. [PMID: 18304532 DOI: 10.1016/j.exer.2007.11.019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2007] [Revised: 11/27/2007] [Accepted: 11/28/2007] [Indexed: 11/19/2022]
Abstract
Longitudinal studies of a variety of transgenic mouse models for lens development can create substantial challenges in database management and analysis. We report a novel, automated, feature-based informatics approach to screening lens phenotypes in a large database of slit lamp images. Digital slit lamp images of normal and abnormal lenses in eyes of wild type (wt), SC1 null and SPARC null transgenic mice were recorded for quantitative evaluation of their structural phenotype. The images were processed to improve the contrast of structural features that corresponded to rings of opacity and fluctuations in scattering intensity in the lenses. Measurable attributes were assigned to the features in the lens images and given as an output vector of 46 dimensions. Characteristic patterns were correlated with the structural phenotype of each mutant and wt lens and a statistical fit for each phenotype was defined. The genotype was identified correctly in nearly 85% of the slit lamp images on the basis of an automated computer analysis of the lens structural phenotype. The automated computer algorithm has the potential to evaluate a large database of slit lamp images and distinguish mouse genotypes on the basis of lens phenotypes objectively using a neural network analysis of the structural features observed in the slit lamp images. The neural network approach is a promising technology for objective evaluation of genotype/phenotype relationships based on structural features and light scattering in lenses. Further improvements in the automated method can be expected to simplify and increase the accuracy and efficiency of the feature based analysis of structural phenotypes linked to genetic variation.
Collapse
Affiliation(s)
- Jenny Yuen
- Department of Computer Science and Engineering, University of Washington, Seattle, WA 98195, USA.
| | | | | | | | | | | | | |
Collapse
|
8
|
Muchowski PJ, Ramsden R, Nguyen Q, Arnett EE, Greiling TM, Anderson SK, Clark JI. Noninvasive measurement of protein aggregation by mutant huntingtin fragments or alpha-synuclein in the lens. J Biol Chem 2007; 283:6330-6. [PMID: 18167346 DOI: 10.1074/jbc.m709678200] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Many diverse human diseases are associated with protein aggregation in ordered fibrillar structures called amyloid. Amyloid formation may mediate aberrant protein interactions that culminate in neurodegeneration in Alzheimer, Huntington, and Parkinson diseases and in prion encephalopathies. Studies of protein aggregation in the brain are hampered by limitations in imaging techniques and often require invasive methods that can only be performed postmortem. Here we describe transgenic mice in which aggregation-prone proteins that cause Huntington and Parkinson disease are expressed in the ocular lens. Expression of a mutant huntingtin fragment or alpha-synuclein in the lens leads to protein aggregation and cataract formation, which can be monitored in real time by noninvasive, highly sensitive optical techniques. Expression of a mutant huntingtin fragment in mice lacking the major lens chaperone, alphaB-crystallin, markedly accelerated the onset and severity of aggregation, demonstrating that the endogenous chaperone activity of alphaB-crystallin suppresses aggregation in vivo. These novel mouse models will facilitate the characterization of protein aggregation in vivo and are being used in efficient and economical screens for chemical and genetic modifiers of disease-relevant protein aggregation.
Collapse
Affiliation(s)
- Paul J Muchowski
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA.
| | | | | | | | | | | | | |
Collapse
|
9
|
Emerson RO, Sage EH, Ghosh JG, Clark JI. Chaperone-like activity revealed in the matricellular protein SPARC. J Cell Biochem 2006; 98:701-5. [PMID: 16598771 DOI: 10.1002/jcb.20867] [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: 11/06/2022]
Abstract
SPARC (Secreted Protein, Acidic and Rich in Cysteine) is a matricellular glycoprotein that modulates cell proliferation, adhesion, migration, and extracellular matrix (ECM) production. In this report chaperone-like activity of SPARC was identified in a thermal aggregation assay in vitro. Ultraviolet circular dichroism (UVCD) spectroscopy determined that SPARC was stable at temperatures up to 50 degrees C. Unfolding and aggregation of the chaperone target protein, alcohol dehydrogenase (ADH), were initiated at 50 degrees C. SPARC inhibited the thermal aggregation of ADH in a concentration-dependent manner, with maximal inhibition at a 1:4 molar ratio of SPARC:ADH. Synergy between the chaperone-like activities of SPARC and alphaB-crystallin, a small heat shock protein and molecular chaperone in the lens, was observed in SPARC-alphaB-crystallin double -/- mice.
Collapse
Affiliation(s)
- Ryan O Emerson
- Department of Biological Structure, University of Washington, Seattle, WA 98195-7420, USA
| | | | | | | |
Collapse
|
10
|
Bettelheim FA. Light scattering in lens research: an essay on accomplishments and promises. Exp Eye Res 2005; 79:747-52. [PMID: 15642311 DOI: 10.1016/j.exer.2004.06.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2004] [Accepted: 06/09/2004] [Indexed: 11/29/2022]
Abstract
This paper briefly reviews light scattering methodologies in lens research. In the phenomenological sense cataract formation (lens opacities or turbidities) in its early stages can be described by enhanced scattering of light. In the analytical sense information is obtained on the molecular entities involved in light scattering. In Section 2, different methodologies (mainly static and dynamic) of light scattering experiments are described, which had been used successfully in lens research. In Section 3 the problem of interpretation of light scattering data in condensed phase is considered. It is pointed out that due to interparticle interactions the concentration dependence of the data must be considered. If dilution or thin sectioning of samples is not an option, it is better to report molecular parameters in terms of diffusion coefficients or decay times. In Section 4, a case is made to encourage light scattering experiments in the polarized/depolarized modes both in static and dynamic light scatterings. Preliminary data obtained with polarized/depolarized dynamic light scattering measurements on alpha-crystallin and interpreted in view of model systems and literature data imply that the molecule is a compact sphere with somewhat restricted segment mobility. The preliminary nature of this information is due to the unavailability of high power lasers and efficient polarizers in my lab at the time of these experiments.
Collapse
|