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Varadaraj K, Gao J, Mathias RT, Kumari S. Effect of hydrogen peroxide on lens transparency, intracellular pH, gap junction coupling, hydrostatic pressure and membrane water permeability. Exp Eye Res 2024; 245:109957. [PMID: 38843983 DOI: 10.1016/j.exer.2024.109957] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 06/02/2024] [Accepted: 06/03/2024] [Indexed: 06/09/2024]
Abstract
Clouding of the eye lens or cataract is an age-related anomaly that affects middle-aged humans. Exploration of the etiology points to a great extent to oxidative stress due to different forms of reactive oxygen species/metabolites such as Hydrogen peroxide (H2O2) that are generated due to intracellular metabolism and environmental factors like radiation. If accumulated and left unchecked, the imbalance between the production and degradation of H2O2 in the lens could lead to cataracts. Our objective was to explore ex vivo the effects of H2O2 on lens physiology. We investigated transparency, intracellular pH (pHi), intercellular gap junction coupling (GJC), hydrostatic pressure (HP) and membrane water permeability after subjecting two-month-old C57 wild-type (WT) mouse lenses for 3 h or 8 h in lens saline containing 50 μM H2O2; the results were compared with control lenses incubated in the saline without H2O2. There was a significant decrease in lens transparency in H2O2-treated lenses. In control lenses, pHi decreases from ∼7.34 in the surface fiber cells to 6.64 in the center. Experimental lenses exposed to H2O2 for 8 h showed a significant decrease in surface pH (from 7.34 to 6.86) and central pH (from 6.64 to 6.56), compared to the controls. There was a significant increase in GJC resistance in the differentiating (12-fold) and mature (1.4-fold) fiber cells compared to the control. Experimental lenses also showed a significant increase in HP which was ∼2-fold higher at the junction between the differentiating and mature fiber cells and ∼1.5-fold higher at the center compared to these locations in control lenses; HP at the surface was 0 mm Hg in either type lens. Fiber cell membrane water permeability significantly increased in H2O2-exposed lenses compared to controls. Our data demonstrate that elevated levels of lens intracellular H2O2 caused a decrease in intracellular pH and led to acidosis which most likely uncoupled GJs, and increased AQP0-dependent membrane water permeability causing a consequent rise in HP. We infer that an abnormal increase in intracellular H2O2 could induce acidosis, cause oxidative stress, alter lens microcirculation, and lead to the development of accelerated lens opacity and age-related cataracts.
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Affiliation(s)
- Kulandaiappan Varadaraj
- Physiology and Biophysics, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, USA.
| | - Junyuan Gao
- Physiology and Biophysics, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, USA
| | - Richard T Mathias
- Physiology and Biophysics, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, USA
| | - Sindhu Kumari
- Physiology and Biophysics, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, USA
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2
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Shiels A. Through the Cat-Map Gateway: A Brief History of Cataract Genetics. Genes (Basel) 2024; 15:785. [PMID: 38927721 PMCID: PMC11202810 DOI: 10.3390/genes15060785] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2024] [Revised: 06/06/2024] [Accepted: 06/13/2024] [Indexed: 06/28/2024] Open
Abstract
Clouding of the transparent eye lens, or cataract(s), is a leading cause of visual impairment that requires surgical replacement with a synthetic intraocular lens to effectively restore clear vision. Most frequently, cataract is acquired with aging as a multifactorial or complex trait. Cataract may also be inherited as a classic Mendelian trait-often with an early or pediatric onset-with or without other ocular and/or systemic features. Since the early 1990s, over 85 genes and loci have been genetically associated with inherited and/or age-related forms of cataract. While many of these underlying genes-including those for lens crystallins, connexins, and transcription factors-recapitulate signature features of lens development and differentiation, an increasing cohort of unpredicted genes, including those involved in cell-signaling, membrane remodeling, and autophagy, has emerged-providing new insights regarding lens homeostasis and aging. This review provides a brief history of gene discovery for inherited and age-related forms of cataract compiled in the Cat-Map database and highlights potential gene-based therapeutic approaches to delay, reverse, or even prevent cataract formation that may help to reduce the increasing demand for cataract surgery.
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Affiliation(s)
- Alan Shiels
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA
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3
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Mucke HAM. Drug Repurposing Patent Applications October-December 2023. Assay Drug Dev Technol 2024; 22:160-167. [PMID: 38437578 DOI: 10.1089/adt.2024.011] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/06/2024] Open
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Aihara K, Nakazawa Y, Takeda S, Hatsusaka N, Onouchi T, Hiramatsu N, Nagata M, Nagai N, Funakoshi-Tago M, Yamamoto N, Sasaki H. Aquaporins contribute to vacuoles formation in Nile grass type II diabetic rats. Med Mol Morphol 2023; 56:274-287. [PMID: 37493821 DOI: 10.1007/s00795-023-00365-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Accepted: 07/09/2023] [Indexed: 07/27/2023]
Abstract
Regulation of ion and water microcirculation within the lens is tightly controlled through aquaporin channels and connexin junctions. However, cataracts can occur when the lens becomes cloudy. Various factors can induce cataracts, including diabetes which is a well-known cause. The most common phenotype of diabetic cataracts is a cortical and/or posterior subcapsular opacity. In addition to the three main types and two subtypes of cataracts, a vacuole formation is frequently observed; however, their origin remains unclear. In this study, we focused on the aquaporins and connexins involved in diabetes-induced cataracts and vacuoles in Nile grass type II diabetes. The results showed that the expression of aquaporin 0 and aquaporin 5 increased, and that of connexin 43 decreased in diabetic rat lenses. Additionally, aquaporin 0 and 5 were strongly localized in peripheral of vacuoles, suggesting that aquaporins are involved in vacuoles formation. Transillumination photography revealed large vacuoles at the tip of the Y-suture in the anterior capsule of the diabetic lens, and several small vacuoles were observed in the posterior capsule. Within the vacuoles, cytoplasmic degradation and aggregation of fibrous material were observed. Our findings suggest that aquaporins are potential candidate proteins for preventing vacuole formation.
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Affiliation(s)
- Kana Aihara
- Faculty of Pharmacy, Keio University, 1-5-30, Shibako-en, Minato-ku, Tokyo, 105-8512, Japan
| | - Yosuke Nakazawa
- Faculty of Pharmacy, Keio University, 1-5-30, Shibako-en, Minato-ku, Tokyo, 105-8512, Japan.
| | - Shun Takeda
- Department of Ophthalmology, Kanazawa Medical University, 1-1 Daigaku Uchinada-machi, Kahoku-gun, Kahoku, Ishikawa, 920-0293, Japan
| | - Natsuko Hatsusaka
- Department of Ophthalmology, Kanazawa Medical University, 1-1 Daigaku Uchinada-machi, Kahoku-gun, Kahoku, Ishikawa, 920-0293, Japan
| | - Takanori Onouchi
- Research Promotion Headquarters, Fujita Health University, Toyoake, Aichi, 470-1192, Japan
| | - Noriko Hiramatsu
- Research Promotion Headquarters, Fujita Health University, Toyoake, Aichi, 470-1192, Japan
| | - Mayumi Nagata
- Department of Ophthalmology, Dokkyo Medical University, Shimotsugagun, Tochigi, 321-0293, Japan
| | - Noriaki Nagai
- Faculty of Pharmacy, Kindai University, Higashi-Osaka, Osaka, 577-8502, Japan
| | - Megumi Funakoshi-Tago
- Faculty of Pharmacy, Keio University, 1-5-30, Shibako-en, Minato-ku, Tokyo, 105-8512, Japan
| | - Naoki Yamamoto
- Research Promotion Headquarters, Fujita Health University, Toyoake, Aichi, 470-1192, Japan
| | - Hiroshi Sasaki
- Department of Ophthalmology, Kanazawa Medical University, 1-1 Daigaku Uchinada-machi, Kahoku-gun, Kahoku, Ishikawa, 920-0293, Japan.
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Giannone AA, Sellitto C, Rosati B, McKinnon D, White TW. Single-Cell RNA Sequencing Analysis of the Early Postnatal Mouse Lens Epithelium. Invest Ophthalmol Vis Sci 2023; 64:37. [PMID: 37870847 PMCID: PMC10599162 DOI: 10.1167/iovs.64.13.37] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Accepted: 10/06/2023] [Indexed: 10/24/2023] Open
Abstract
Purpose The lens epithelium maintains the overall health of the organ. We used single-cell RNA sequencing (scRNA-seq) technology to assess transcriptional heterogeneity between cells in the postnatal day 2 (P2) epithelium and identify distinct epithelial cell subtypes. Analysis of these data was used to better understand lens growth, differentiation, and homeostasis on P2. Methods scRNA-seq on P2 mouse lenses was performed using the 10x Genomics Chromium Single Cell 3' Kit (v3.1) and short-read Illumina sequencing. Sequence alignment and preprocessing of data were conducted using 10x Genomics Cell Ranger software. Seurat was employed for preprocessing, quality control, dimensionality reduction, and cell clustering, and Monocle was utilized for trajectory analysis to understand the developmental progression of the lens cells. CellChat and GO analyses were used to explore cell-cell communication networks and signaling interactions. Results Lens epithelial cells (LECs) were divided into seven subclusters, classified by specific gene markers. The expression of crystallin, cell-cycle, and metabolic genes was not uniform, indicating distinct functional roles of LECs. Trajectory analysis predicted a bifurcation of differentiating and cycling cells from an Igfbp5+ progenitor pool. We also identified heterogeneity in signaling molecules and pathways, suggesting that cycling and progenitor subclusters have prominent roles in coordinating crosstalk. Conclusions scRNA-seq corroborated many known markers of epithelial differentiation and proliferation while providing further insight into the pathways and genes directing these processes. Interestingly, we demonstrated that the developing epithelium can be divided into distinct subpopulations. These clusters reflect the transcriptionally diverse roles of the epithelium in proliferation, signaling, and maintenance.
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Affiliation(s)
- Adrienne A. Giannone
- Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook University, Stony Brook, New York, United States
| | - Caterina Sellitto
- Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook University, Stony Brook, New York, United States
| | - Barbara Rosati
- Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook University, Stony Brook, New York, United States
- Veterans Affairs Medical Center, Northport, New York, United States
| | - David McKinnon
- Department of Neurobiology and Behavior, Stony Brook University School of Medicine, Stony Brook University, Stony Brook, New York, United States
| | - Thomas W. White
- Department of Physiology and Biophysics, Stony Brook University School of Medicine, Stony Brook University, Stony Brook, New York, United States
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Rodríguez-Solana P, Arruti N, Nieves-Moreno M, Mena R, Rodríguez-Jiménez C, Guerrero-Carretero M, Acal JC, Blasco J, Peralta JM, Del Pozo Á, Montaño VEF, Dios-Blázquez LD, Fernández-Alcalde C, González-Atienza C, Sánchez-Cazorla E, Gómez-Cano MDLÁ, Delgado-Mora L, Noval S, Vallespín E. Whole Exome Sequencing of 20 Spanish Families: Candidate Genes for Non-Syndromic Pediatric Cataracts. Int J Mol Sci 2023; 24:11429. [PMID: 37511188 PMCID: PMC10380485 DOI: 10.3390/ijms241411429] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Revised: 06/23/2023] [Accepted: 07/11/2023] [Indexed: 07/30/2023] Open
Abstract
Non-syndromic pediatric cataracts are defined as opacification of the crystalline lens that occurs during the first years of life without affecting other organs. Given that this disease is one of the most frequent causes of reversible blindness in childhood, the main objective of this study was to propose new responsible gene candidates that would allow a more targeted genetic approach and expand our genetic knowledge about the disease. We present a whole exome sequencing (WES) study of 20 Spanish families with non-syndromic pediatric cataracts and a previous negative result on an ophthalmology next-generation sequencing panel. After ophthalmological evaluation and collection of peripheral blood samples from these families, WES was performed. We were able to reach a genetic diagnosis in 10% of the families analyzed and found genes that could cause pediatric cataracts in 35% of the cohort. Of the variants found, 18.2% were classified as pathogenic, 9% as likely pathogenic, and 72.8% as variants of uncertain significance. However, we did not find conclusive results in 55% of the families studied, which suggests further studies are needed. The results of this WES study allow us to propose LONP1, ACACA, TRPM1, CLIC5, HSPE1, ODF1, PIKFYVE, and CHMP4A as potential candidates to further investigate for their role in pediatric cataracts, and AQP5 and locus 2q37 as causal genes.
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Affiliation(s)
- Patricia Rodríguez-Solana
- Molecular Ophthalmology Section, Institute of Medical and Molecular Genetics (INGEMM), IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (P.R.-S.); (R.M.); (C.R.-J.); (V.E.F.M.); (C.G.-A.); (E.S.-C.)
| | - Natalia Arruti
- Department of Pediatric Ophthalmology, IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (N.A.); (M.N.-M.); (M.G.-C.); (J.C.A.); (J.B.); (J.M.P.); (C.F.-A.); (S.N.)
- European Reference Network on Eye Diseases (ERN-EYE), La Paz University Hospital, 28046 Madrid, Spain
| | - María Nieves-Moreno
- Department of Pediatric Ophthalmology, IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (N.A.); (M.N.-M.); (M.G.-C.); (J.C.A.); (J.B.); (J.M.P.); (C.F.-A.); (S.N.)
- European Reference Network on Eye Diseases (ERN-EYE), La Paz University Hospital, 28046 Madrid, Spain
| | - Rocío Mena
- Molecular Ophthalmology Section, Institute of Medical and Molecular Genetics (INGEMM), IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (P.R.-S.); (R.M.); (C.R.-J.); (V.E.F.M.); (C.G.-A.); (E.S.-C.)
- Biomedical Research Center in the Rare Diseases Network (CIBERER), Carlos II Health Institute (ISCIII), 28029 Madrid, Spain; (Á.D.P.); (M.d.L.Á.G.-C.); (L.D.-M.)
| | - Carmen Rodríguez-Jiménez
- Molecular Ophthalmology Section, Institute of Medical and Molecular Genetics (INGEMM), IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (P.R.-S.); (R.M.); (C.R.-J.); (V.E.F.M.); (C.G.-A.); (E.S.-C.)
| | - Marta Guerrero-Carretero
- Department of Pediatric Ophthalmology, IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (N.A.); (M.N.-M.); (M.G.-C.); (J.C.A.); (J.B.); (J.M.P.); (C.F.-A.); (S.N.)
| | - Juan Carlos Acal
- Department of Pediatric Ophthalmology, IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (N.A.); (M.N.-M.); (M.G.-C.); (J.C.A.); (J.B.); (J.M.P.); (C.F.-A.); (S.N.)
| | - Joana Blasco
- Department of Pediatric Ophthalmology, IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (N.A.); (M.N.-M.); (M.G.-C.); (J.C.A.); (J.B.); (J.M.P.); (C.F.-A.); (S.N.)
| | - Jesús M. Peralta
- Department of Pediatric Ophthalmology, IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (N.A.); (M.N.-M.); (M.G.-C.); (J.C.A.); (J.B.); (J.M.P.); (C.F.-A.); (S.N.)
| | - Ángela Del Pozo
- Biomedical Research Center in the Rare Diseases Network (CIBERER), Carlos II Health Institute (ISCIII), 28029 Madrid, Spain; (Á.D.P.); (M.d.L.Á.G.-C.); (L.D.-M.)
- Clinical Bioinformatics Section, Institute of Medical and Molecular Genetics (INGEMM), IdiPaz, CIBERER, La Paz University Hospital, 28046 Madrid, Spain;
| | - Victoria E. F. Montaño
- Molecular Ophthalmology Section, Institute of Medical and Molecular Genetics (INGEMM), IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (P.R.-S.); (R.M.); (C.R.-J.); (V.E.F.M.); (C.G.-A.); (E.S.-C.)
- Biomedical Research Center in the Rare Diseases Network (CIBERER), Carlos II Health Institute (ISCIII), 28029 Madrid, Spain; (Á.D.P.); (M.d.L.Á.G.-C.); (L.D.-M.)
| | - Lucía De Dios-Blázquez
- Clinical Bioinformatics Section, Institute of Medical and Molecular Genetics (INGEMM), IdiPaz, CIBERER, La Paz University Hospital, 28046 Madrid, Spain;
| | - Celia Fernández-Alcalde
- Department of Pediatric Ophthalmology, IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (N.A.); (M.N.-M.); (M.G.-C.); (J.C.A.); (J.B.); (J.M.P.); (C.F.-A.); (S.N.)
| | - Carmen González-Atienza
- Molecular Ophthalmology Section, Institute of Medical and Molecular Genetics (INGEMM), IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (P.R.-S.); (R.M.); (C.R.-J.); (V.E.F.M.); (C.G.-A.); (E.S.-C.)
| | - Eloísa Sánchez-Cazorla
- Molecular Ophthalmology Section, Institute of Medical and Molecular Genetics (INGEMM), IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (P.R.-S.); (R.M.); (C.R.-J.); (V.E.F.M.); (C.G.-A.); (E.S.-C.)
| | - María de Los Ángeles Gómez-Cano
- Biomedical Research Center in the Rare Diseases Network (CIBERER), Carlos II Health Institute (ISCIII), 28029 Madrid, Spain; (Á.D.P.); (M.d.L.Á.G.-C.); (L.D.-M.)
- Clinical Genetics Section, Institute of Medical and Molecular Genetics (INGEMM), IdiPaz, CIBERER, La Paz University Hospital, 28046 Madrid, Spain
| | - Luna Delgado-Mora
- Biomedical Research Center in the Rare Diseases Network (CIBERER), Carlos II Health Institute (ISCIII), 28029 Madrid, Spain; (Á.D.P.); (M.d.L.Á.G.-C.); (L.D.-M.)
- Clinical Genetics Section, Institute of Medical and Molecular Genetics (INGEMM), IdiPaz, CIBERER, La Paz University Hospital, 28046 Madrid, Spain
| | - Susana Noval
- Department of Pediatric Ophthalmology, IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (N.A.); (M.N.-M.); (M.G.-C.); (J.C.A.); (J.B.); (J.M.P.); (C.F.-A.); (S.N.)
- European Reference Network on Eye Diseases (ERN-EYE), La Paz University Hospital, 28046 Madrid, Spain
| | - Elena Vallespín
- Molecular Ophthalmology Section, Institute of Medical and Molecular Genetics (INGEMM), IdiPaz, La Paz University Hospital, 28046 Madrid, Spain; (P.R.-S.); (R.M.); (C.R.-J.); (V.E.F.M.); (C.G.-A.); (E.S.-C.)
- European Reference Network on Eye Diseases (ERN-EYE), La Paz University Hospital, 28046 Madrid, Spain
- Biomedical Research Center in the Rare Diseases Network (CIBERER), Carlos II Health Institute (ISCIII), 28029 Madrid, Spain; (Á.D.P.); (M.d.L.Á.G.-C.); (L.D.-M.)
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Liu Z, Huang S, Zheng Y, Zhou T, Hu L, Xiong L, Li DWC, Liu Y. The lens epithelium as a major determinant in the development, maintenance, and regeneration of the crystalline lens. Prog Retin Eye Res 2023; 92:101112. [PMID: 36055924 DOI: 10.1016/j.preteyeres.2022.101112] [Citation(s) in RCA: 14] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2022] [Revised: 07/28/2022] [Accepted: 08/02/2022] [Indexed: 02/01/2023]
Abstract
The crystalline lens is a transparent and refractive biconvex structure formed by lens epithelial cells (LECs) and lens fibers. Lens opacity, also known as cataracts, is the leading cause of blindness in the world. LECs are the principal cells of lens throughout human life, exhibiting different physiological properties and functions. During the embryonic stage, LECs proliferate and differentiate into lens fibers, which form the crystalline lens. Genetics and environment are vital factors that influence normal lens development. During maturation, LECs help maintain lens homeostasis through material transport, synthesis and metabolism as well as mitosis and proliferation. If disturbed, this will result in loss of lens transparency. After cataract surgery, the repair potential of LECs is activated and the structure and transparency of the regenerative tissue depends on postoperative microenvironment. This review summarizes recent research advances on the role of LECs in lens development, homeostasis, and regeneration, with a particular focus on the role of cholesterol synthesis (eg., lanosterol synthase) in lens development and homeostasis maintenance, and how the regenerative potential of LECs can be harnessed to develop surgical strategies and improve the outcomes of cataract surgery (Fig. 1). These new insights suggest that LECs are a major determinant of the physiological and pathological state of the lens. Further studies on their molecular biology will offer possibility to explore new approaches for cataract prevention and treatment.
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Affiliation(s)
- Zhenzhen Liu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Shan Huang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Yingfeng Zheng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Tian Zhou
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Leyi Hu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Lang Xiong
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - David Wan-Cheng Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China
| | - Yizhi Liu
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, 510060, China; Research Unit of Ocular Development and Regeneration, Chinese Academy of Medical Sciences, Beijing, 100085, China.
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8
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Quinlan RA, Clark JI. Insights into the biochemical and biophysical mechanisms mediating the longevity of the transparent optics of the eye lens. J Biol Chem 2022; 298:102537. [PMID: 36174677 PMCID: PMC9638808 DOI: 10.1016/j.jbc.2022.102537] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2021] [Revised: 09/20/2022] [Accepted: 09/22/2022] [Indexed: 11/18/2022] Open
Abstract
In the human eye, a transparent cornea and lens combine to form the "refracton" to focus images on the retina. This requires the refracton to have a high refractive index "n," mediated largely by extracellular collagen fibrils in the corneal stroma and the highly concentrated crystallin proteins in the cytoplasm of the lens fiber cells. Transparency is a result of short-range order in the spatial arrangement of corneal collagen fibrils and lens crystallins, generated in part by post-translational modifications (PTMs). However, while corneal collagen is remodeled continuously and replaced, lens crystallins are very long-lived and are not replaced and so accumulate PTMs over a lifetime. Eventually, a tipping point is reached when protein aggregation results in increased light scatter, inevitably leading to the iconic protein condensation-based disease, age-related cataract (ARC). Cataracts account for 50% of vision impairment worldwide, affecting far more people than other well-known protein aggregation-based diseases. However, because accumulation of crystallin PTMs begins before birth and long before ARC presents, we postulate that the lens protein PTMs contribute to a "cataractogenic load" that not only increases with age but also has protective effects on optical function by stabilizing lens crystallins until a tipping point is reached. In this review, we highlight decades of experimental findings that support the potential for PTMs to be protective during normal development. We hypothesize that ARC is preventable by protecting the biochemical and biophysical properties of lens proteins needed to maintain transparency, refraction, and optical function.
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Affiliation(s)
- Roy A Quinlan
- Department of Biosciences, Durham University, South Road Science Site, Durham, United Kingdom; Department of Biological Structure, University of Washington, Seattle, Washington, USA.
| | - John I Clark
- Department of Biological Structure, University of Washington, Seattle, Washington, USA.
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Sellitto C, Li L, White TW. Double Deletion of PI3K and PTEN Modifies Lens Postnatal Growth and Homeostasis. Cells 2022; 11:cells11172708. [PMID: 36078116 PMCID: PMC9455000 DOI: 10.3390/cells11172708] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Revised: 08/23/2022] [Accepted: 08/27/2022] [Indexed: 11/16/2022] Open
Abstract
We have previously shown that the conditional deletion of either the p110α catalytic subunit of phosphatidylinositol 3-kinase (PI3K), or its opposing phosphatase, phosphatase and tensin homolog (PTEN), had distinct effects on lens growth and homeostasis. The deletion of p110α reduced the levels of phosphorylated Akt and equatorial epithelial cell proliferation, and resulted in smaller transparent lenses in adult mice. The deletion of PTEN increased levels of phosphorylated Akt, altered lens sodium transport, and caused lens rupture and cataract. Here, we have generated conditional p110α/PTEN double-knockout mice, and evaluated epithelial cell proliferation and lens homeostasis. The double deletion of p110α and PTEN rescued the defect in lens size seen after the single knockout of p110α, but accelerated the lens rupture phenotype seen in PTEN single-knockout mice. Levels of phosphorylated Akt in double-knockout lenses were significantly higher than in wild-type lenses, but not as elevated as those reported for PTEN single-knockout lenses. These results showed that the double deletion of the p110α catalytic subunit of PI3K and its opposing phosphatase, PTEN, exacerbated the rupture defect seen in the single PTEN knockout and alleviated the growth defect observed in the single p110α knockout. Thus, the integrity of the PI3K signaling pathway was absolutely essential for proper lens homeostasis, but not for lens growth.
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Retamal MA, Altenberg GA. Role and Posttranslational Regulation of Cx46 Hemichannels and Gap Junction Channels in the Eye Lens. Front Physiol 2022; 13:864948. [PMID: 35431975 PMCID: PMC9006113 DOI: 10.3389/fphys.2022.864948] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2022] [Accepted: 03/14/2022] [Indexed: 12/31/2022] Open
Abstract
Connexins are a family of proteins that can form two distinct types of channels: hemichannels and gap junction channels. Hemichannels are composed of six connexin subunits and when open allow for exchanges between the cytoplasm and the extracellular milieu. Gap junction channels are formed by head-to-head docking of two hemichannels in series, each one from one of two adjacent cells. These channels allow for exchanges between the cytoplasms of contacting cells. The lens is a transparent structure located in the eye that focuses light on the retina. The transparency of the lens depends on its lack of blood irrigation and the absence of organelles in its cells. To survive such complex metabolic scenario, lens cells express Cx43, Cx46 and Cx50, three connexins isoforms that form hemichannels and gap junction channels that allow for metabolic cooperation between lens cells. This review focuses on the roles of Cx46 hemichannels and gap junction channels in the lens under physiological conditions and in the formation of cataracts, with emphasis on the modulation by posttranslational modifications.
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Affiliation(s)
- Mauricio A. Retamal
- Universidad del Desarrollo, Centro de Fisiología Celular e Integrativa, Clínica Alemana Facultad de Medicina, Santiago, Chile
- Universidad del Desarrollo, Programa de Comunicación Celular en Cáncer, Clínica Alemana Facultad de Medicina, Santiago, Chile
- Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- *Correspondence: Mauricio A. Retamal, ; Guillermo A. Altenberg,
| | - Guillermo A. Altenberg
- Department of Cell Physiology and Molecular Biophysics, and Center for Membrane Protein Research, School of Medicine, Texas Tech University Health Sciences Center, Lubbock, TX, United States
- *Correspondence: Mauricio A. Retamal, ; Guillermo A. Altenberg,
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