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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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Sun Q, Li J, Ma J, Zheng Y, Ju R, Li X, Ren X, Huang L, Chen R, Tan X, Luo L. JAM-C Is Important for Lens Epithelial Cell Proliferation and Lens Fiber Maturation in Murine Lens Development. Invest Ophthalmol Vis Sci 2023; 64:15. [PMID: 38095908 PMCID: PMC10723223 DOI: 10.1167/iovs.64.15.15] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2023] [Accepted: 11/16/2023] [Indexed: 12/17/2023] Open
Abstract
Purpose The underlying mechanism of congenital cataracts caused by deficiency or mutation of junctional adhesion molecule C (JAM-C) gene remains unclear. Our study aims to elucidate the abnormal developmental process in Jamc-/- lenses and reveal the genes related to lens development that JAM-C may regulate. Methods Jamc knockout (Jamc-/-) mouse embryos and pups were generated for in vivo studies. Four key developmental stages from embryonic day (E) 12.5 to postnatal day (P) 0.5 were selected for the following experiments. Hematoxylin and eosin staining was used for histological analysis. The 5-bromo-2'-deoxyuridine (BrdU) incorporation assay and TUNEL staining were performed to label lens epithelial cell (LEC) proliferation and apoptosis, respectively. Immunofluorescence and Western blot were used to analyze the markers of lens epithelium, cell cycle exit, and lens fiber differentiation. Results JAM-C was expressed throughout the process of lens development. Deletion of Jamc resulted in decreased lens size and disorganized lens fibers, which arose from E16.5 and aggravated gradually. The LECs of Jamc-/- lenses showed decreased quantity and proliferation, accompanied with reduction of key transcription factor, FOXE3. The fibers in Jamc-/- lenses were disorganized. Moreover, Jamc-deficient lens fibers showed significantly altered distribution patterns of Cx46 and Cx50. The marker of fiber homeostasis, γ-crystallin, was also decreased in the inner cortex and core fibers of Jamc-/- lenses. Conclusions Deletion of JAM-C exhibits malfunction of LEC proliferation and fiber maturation during murine lens development, which may be related to the downregulation of FOXE3 expression and abnormal localization patterns of Cx46 and Cx50.
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Affiliation(s)
- Qihang Sun
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Jiani Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Jingyu Ma
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Yuxing Zheng
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Rong Ju
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Xuri Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Xiangrong Ren
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Lijuan Huang
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Rongyuan Chen
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Xuhua Tan
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Lixia Luo
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
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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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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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Li J, Tan X, Sun Q, Li X, Chen R, Luo L. Deficiency of Jamc Leads to Congenital Nuclear Cataract and Activates the Unfolded Protein Response in Mouse Lenses. Invest Ophthalmol Vis Sci 2022; 63:1. [PMID: 36048019 PMCID: PMC9440611 DOI: 10.1167/iovs.63.10.1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The malfunction of junctional adhesion molecule C (JAM-C) has been reported to induce congenital cataract in humans and mice; however, specific characters and the mechanism of this cataract are still unclear. This study aimed to characterize abnormal lens development in Jamc knockout mice and clarify the underlying mechanism. Methods Jamc knockout mice backcrossed onto the C57BL/6 genetic background were used for this research. Slit-lamp and darkfield images showed the cataract phenotype of Jamc−/− mice. Hematoxylin and eosin staining was performed to visualize the morphological and histological features. RNA sequencing was applied to detect differentially expressed genes. Quantitative RT-PCR, western blot, and immunofluorescence were used to determine the level of unfolded protein response (UPR)-related genes. TUNEL staining was utilized to label cell death. Results Jamc knockout mice exhibited nuclear cataract with abnormal lens morphology and defective degradation of nuclei and organelles in lens fiber cells. Compared with wild-type control mice, the expression level of BiP, CHOP, TRIB3, and CHAC1, genes involved in endoplasmic reticulum stress and the UPR, were highly upregulated in Jamc−/− lenses, suggesting that abnormal lens development was accompanied by UPR activation. Moreover, increased cell death was also found in Jamc−/− lenses. Conclusions Congenital nuclear cataract caused by Jamc deficiency is accompanied by defective degradation of nuclei and organelles in lens fiber cells, lens structure disorder, and UPR activation, suggesting that JAM-C is required for maintaining normal lens development and that UPR activation is involved in cataract formation in Jamc-deficient lenses.
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Affiliation(s)
- Jiani Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Xuhua Tan
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Qihang Sun
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Xuri Li
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Rongyuan Chen
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
| | - Lixia Luo
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangdong Provincial Key Laboratory of Ophthalmology and Visual Science, Guangzhou, China
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Shiels A, Hejtmancik JF. Inherited cataracts: Genetic mechanisms and pathways new and old. Exp Eye Res 2021; 209:108662. [PMID: 34126080 PMCID: PMC8595562 DOI: 10.1016/j.exer.2021.108662] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 05/13/2021] [Accepted: 06/01/2021] [Indexed: 12/15/2022]
Abstract
Cataract(s) is the clinical equivalent of lens opacity and is caused by light scattering either by high molecular weight protein aggregates in lens cells or disruption of the lens microarchitecture itself. Genetic mutations underlying inherited cataract can provide insight into the biological processes and pathways critical for lens homeostasis and transparency, classically including the lens crystallins, connexins, membrane proteins or components, and intermediate filament proteins. More recently, cataract genes have been expanded to include newly identified biological processes such as chaperone or protein degradation components, transcription or growth factors, channels active in the lens circulation, and collagen and extracellular matrix components. Cataracts can be classified by age, and in general congenital cataracts are caused by severe mutations resulting in major damage to lens proteins, while age related cataracts are associated with variants that merely destabilize proteins thereby increasing susceptibility to environmental insults over time. Thus there might be separate pathways to opacity for congenital and age-related cataracts whereby congenital cataracts induce the unfolded protein response (UPR) and apoptosis to destroy the lens microarchitecture, while in age related cataract high molecular weight (HMW) aggregates formed by denatured crystallins bound by α-crystallin result in light scattering without severe damage to the lens microarchitecture.
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Affiliation(s)
- Alan Shiels
- Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO, 63110, USA.
| | - J Fielding Hejtmancik
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD, 20892-1860, USA.
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Guan L, Zhan Z, Yang Y, Miao Y, Huang X, Ding M. Alleviating chronic ER stress by p38-Ire1-Xbp1 pathway and insulin-associated autophagy in C. elegans neurons. PLoS Genet 2020; 16:e1008704. [PMID: 32986702 PMCID: PMC7544145 DOI: 10.1371/journal.pgen.1008704] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Revised: 10/08/2020] [Accepted: 08/11/2020] [Indexed: 01/07/2023] Open
Abstract
ER stress occurs in many physiological and pathological conditions. However, how chronic ER stress is alleviated in specific cells in an intact organism is an outstanding question. Here, overexpressing the gap junction protein UNC-9 (Uncoordinated) in C. elegans neurons triggers the Ire1-Xbp1-mediated stress response in an age-dependent and cell-autonomous manner. The p38 MAPK PMK-3 regulates the chronic stress through IRE-1 phosphorylation. Overexpressing gap junction protein also activates autophagy. The insulin pathway functions through autophagy, but not the transcription of genes encoding ER chaperones, to counteract the p38-Ire1-Xbp1-mediated stress response. Together, these results reveal an intricate cellular regulatory network in response to chronic stress in a subset of cells in multicellular organism. The accumulation of unfolded proteins triggers the ER stress response (UPR), which allows cells to fight against fluctuations in protein expression under both physiological and pathological conditions. Severe acute ER stress responses can be induced by drug treatment. However, such intense ER stress rarely occurs ubiquitously in every cell type in vivo. Here, we designed a genetic system in the nematode C. elegans, which allows us to induce ER stress in specific cells, without drug treatment or any other external stimuli, and then to monitor the stress response. The p38 MAPK directly acts on the phosphorylation of IRE-1 to promote the stress response. Meanwhile, the insulin receptor function through autophagy activation to counteract the p38-IRE-1-XBP-1 pathway. Together, these results reveal an intricate cellular regulatory network in response to chronic stress in multicellular organism.
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Affiliation(s)
- Liying Guan
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- * E-mail: (LG); (MD)
| | - Zhigao Zhan
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yongzhi Yang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Yue Miao
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Xun Huang
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Mei Ding
- State Key Laboratory of Molecular Developmental Biology, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, Beijing, China
- University of Chinese Academy of Sciences, Beijing, China
- * E-mail: (LG); (MD)
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8
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Tjahjono N, Xia CH, Li R, Chu S, Wang J, Gong X. Connexin 50-R205G Mutation Perturbs Lens Epithelial Cell Proliferation and Differentiation. Invest Ophthalmol Vis Sci 2020; 61:25. [PMID: 32182330 PMCID: PMC7401428 DOI: 10.1167/iovs.61.3.25] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Purpose To investigate the underlying mechanisms for how the mouse Cx50-R205G point mutation, a homologue of the human Cx50-R198W mutation that is linked to cataract-microcornea syndrome, affects proper lens growth and fiber cell differentiation to lead to severe lens phenotypes. Methods EdU labeling, immunostaining, confocal imaging analysis, and primary lens epithelial cell culture were performed to characterize the lens epithelial cell (LEC) proliferation and fiber cell differentiation in wild-type and Cx50-R205G mutant lenses in vivo and in vitro. Results The Cx50-R205G mutation severely disrupts the lens size and transparency. Heterozygous and homozygous Cx50-R205G mutant and Cx50 knockout lenses all show decreased central epithelium proliferation while only the homozygous Cx50-R205G mutant lenses display obviously decreased proliferating LECs in the germinative zone of neonatal lenses. Cultured Cx50-R205G lens epithelial cells reveal predominantly reduced Cx50 gap junction staining but no change of the endoplasmic reticulum stress marker BiP. The heterozygous Cx50-R205G lens fibers show moderately disrupted Cx50 and Cx46 gap junctions while the homozygous Cx50-R205G lens fibers have drastically reduced Cx50 and Cx46 gap junctions with severely altered fiber cell shape in vivo. Conclusions The Cx50-R205G mutation inhibits both central and equatorial lens epithelial cell proliferation to cause small lenses. This mutation also disrupts the assembly and functions of both Cx50 and Cx46 gap junctions in lens fibers to alter fiber cell differentiation and shape to lead to severe lens phenotypes.
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Li L, Fan DB, Zhao YT, Li Y, Yang ZB, Zheng GY. GJA8 missense mutation disrupts hemichannels and induces cell apoptosis in human lens epithelial cells. Sci Rep 2019; 9:19157. [PMID: 31844091 PMCID: PMC6915756 DOI: 10.1038/s41598-019-55549-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Accepted: 11/29/2019] [Indexed: 12/16/2022] Open
Abstract
Autosomal dominant congenital cataract (ADCC), the most common hereditary disease, is a major cause of eye disease in children. Due to its high genetic and clinical heterogeneity, the identification of ADCC-associated gene mutations is essential for the development of molecular therapies. In this study, we examined a four-generation Chinese pedigree with ADCC and identified putative mutations in ADCC candidate genes via next-generation sequencing (NGS) followed by Sanger sequencing. A novel missense mutation in GJA8 (c.T217C) in ADCC patients causes a serine-to-proline substitution at residue 73 of connexin 50 (Cx50); no mutation was found in unaffected family members and unrelated healthy individuals. Functional analysis revealed that this missense mutation disrupts protein function in human lens epithelial cells (HLEpiCs), which fails to form calcium-sensitive hemichannels. Furthermore, mutant Cx50 leads to decreased ROS scavenging by inhibiting G6PD expression and thus induces cell apoptosis via aberrant activation of the unfolded protein response (UPR). In conclusion, we report a novel GJA8 heterozygous mutation in a Chinese family with a vital role in ADCC, broadening the genetic spectrum of this disease.
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Affiliation(s)
- Li Li
- Ophthalmologic Center, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China
| | - Da-Bei Fan
- Endocrine Department, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China
| | - Ya-Ting Zhao
- Ophthalmologic Center, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China
| | - Yun Li
- Ophthalmologic Center, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China
| | - Zi-Bing Yang
- Ophthalmologic Center, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China
| | - Guang-Ying Zheng
- Ophthalmologic Center, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China.
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10
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Abstract
Cataract, the clinical correlate of opacity or light scattering in the eye lens, is usually caused by the presence of high-molecular-weight (HMW) protein aggregates or disruption of the lens microarchitecture. In general, genes involved in inherited cataracts reflect important processes and pathways in the lens including lens crystallins, connexins, growth factors, membrane proteins, intermediate filament proteins, and chaperones. Usually, mutations causing severe damage to proteins cause congenital cataracts, while milder variants increasing susceptibility to environmental insults are associated with age-related cataracts. These may have different pathogenic mechanisms: Congenital cataracts induce the unfolded protein response and apoptosis. By contrast, denatured crystallins in age-related cataracts are bound by α-crystallin and form light-scattering HMW aggregates. New therapeutic approaches to age-related cataracts use chemical chaperones to solubilize HMW aggregates, while attempts are being made to regenerate lenses using endogenous stem cells to treat congenital cataracts.
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Affiliation(s)
- Alan Shiels
- Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, Missouri 63110, USA;
| | - J Fielding Hejtmancik
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, Maryland 20892-1860, USA;
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11
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Vetrivel S, Tiso N, Kügler A, Irmler M, Horsch M, Beckers J, Hladik D, Giesert F, Gailus-Durner V, Fuchs H, Sabrautzki S, Hrabě de Angelis M, Graw J. Mutation in the mouse histone gene Hist2h3c1 leads to degeneration of the lens vesicle and severe microphthalmia. Exp Eye Res 2019; 188:107632. [PMID: 30991053 PMCID: PMC6876282 DOI: 10.1016/j.exer.2019.03.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Revised: 03/20/2019] [Accepted: 03/30/2019] [Indexed: 12/21/2022]
Abstract
During an ENU (N-ethyl-N-nitrosourea) mutagenesis screen, we observed a dominant small-eye mutant mouse with viable homozygotes. A corresponding mutant line was established and referred to as Aey69 (abnormality of the eye #69). Comprehensive phenotyping of the homozygous Aey69 mutants in the German Mouse Clinic revealed only a subset of statistically significant alterations between wild types and homozygous mutants. The mutation causes microphthalmia without a lens but with retinal hyperproliferation. Linkage was demonstrated to mouse chromosome 3 between the markers D3Mit188 and D3Mit11. Sequencing revealed a 358 A-> C mutation (Ile120Leu) in the Hist2h3c1 gene and a 71 T-> C (Val24Ala) mutation in the Gja8 gene. Detailed analysis of eye development in the homozygous mutant mice documented a perturbed lens development starting from the lens vesicle stage including decreasing expression of crystallins as well as of lens-specific transcription factors like PITX3 and FOXE3. In contrast, we observed an early expression of retinal progenitor cells characterized by several markers including BRN3 (retinal ganglion cells) and OTX2 (cone photoreceptors). The changes in the retina at the early embryonic stages of E11.5-E15.5 happen in parallel with apoptotic processes in the lens at the respective stages. The excessive retinal hyperproliferation is characterized by an increased level of Ki67. The hyperproliferation, however, does not disrupt the differentiation and appearance of the principal retinal cell types at postnatal stages, even if the overgrowing retina covers finally the entire bulbus of the eye. Morpholino-mediated knock-down of the hist2h3ca1 gene in zebrafish leads to a specific perturbation of lens development. When injected into zebrafish zygotes, only the mutant mouse mRNA leads to severe malformations, ranging from cyclopia to severe microphthalmia. The wild-type Hist2h3c1 mRNA can rescue the morpholino-induced defects corroborating its specific function in lens development. Based upon these data, it is concluded that the ocular function of the Hist2h3c1 gene (encoding a canonical H3.2 variant) is conserved throughout evolution. Moreover, the data highlight also the importance of Hist2h3c1 in the coordinated formation of lens and retina during eye development. A dominant small-eye mutant mouse is caused by a mutation in the histone gene Hist2H3c1. Morpholino-mediated knock-down of hist2h3ca1 in the zebrafish validated this finding. The mutation leads to degeneration of the lens vesicle and retina hyperproliferation.
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Affiliation(s)
- Sharmilee Vetrivel
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Developmental Genetics, D-85764 Neuherberg, Germany
| | - Natascia Tiso
- Department of Biology, University of Padova, I-35131 Padova, Italy.
| | - Andrea Kügler
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Developmental Genetics, D-85764 Neuherberg, Germany
| | - Martin Irmler
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Experimental Genetics, D-85764 Neuherberg, Germany
| | - Marion Horsch
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Experimental Genetics, D-85764 Neuherberg, Germany
| | - Johannes Beckers
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Experimental Genetics, D-85764 Neuherberg, Germany; Chair of Experimental Genetics, School of Life Science Weihenstephan, Technische Universität München, D-85354 Freising, Germany; German Center for Diabetes Research (DZD), D-85764 Neuherberg, Germany
| | - Daniela Hladik
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Developmental Genetics, D-85764 Neuherberg, Germany
| | - Florian Giesert
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Developmental Genetics, D-85764 Neuherberg, Germany
| | - Valerie Gailus-Durner
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Experimental Genetics, D-85764 Neuherberg, Germany
| | - Helmut Fuchs
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Experimental Genetics, D-85764 Neuherberg, Germany
| | - Sibylle Sabrautzki
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Experimental Genetics, D-85764 Neuherberg, Germany; Helmholtz Center Munich, German Research Center for Environmental Health, Research Unit Comparative Medicine, D-85764 Neuherberg, Germany
| | - Martin Hrabě de Angelis
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Experimental Genetics, D-85764 Neuherberg, Germany; Chair of Experimental Genetics, School of Life Science Weihenstephan, Technische Universität München, D-85354 Freising, Germany; German Center for Diabetes Research (DZD), D-85764 Neuherberg, Germany
| | - Jochen Graw
- Helmholtz Center Munich, German Research Center for Environmental Health, Institute of Developmental Genetics, D-85764 Neuherberg, Germany.
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12
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Aasen T, Johnstone S, Vidal-Brime L, Lynn KS, Koval M. Connexins: Synthesis, Post-Translational Modifications, and Trafficking in Health and Disease. Int J Mol Sci 2018; 19:ijms19051296. [PMID: 29701678 PMCID: PMC5983588 DOI: 10.3390/ijms19051296] [Citation(s) in RCA: 62] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2018] [Revised: 04/20/2018] [Accepted: 04/21/2018] [Indexed: 02/06/2023] Open
Abstract
Connexins are tetraspan transmembrane proteins that form gap junctions and facilitate direct intercellular communication, a critical feature for the development, function, and homeostasis of tissues and organs. In addition, a growing number of gap junction-independent functions are being ascribed to these proteins. The connexin gene family is under extensive regulation at the transcriptional and post-transcriptional level, and undergoes numerous modifications at the protein level, including phosphorylation, which ultimately affects their trafficking, stability, and function. Here, we summarize these key regulatory events, with emphasis on how these affect connexin multifunctionality in health and disease.
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Affiliation(s)
- Trond Aasen
- Translational Molecular Pathology, Vall d'Hebron Institute of Research (VHIR), Autonomous University of Barcelona, CIBERONC, 08035 Barcelona, Spain.
| | - Scott Johnstone
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, P.O. Box 801394, Charlottesville, VI 22908, USA.
- Institute of Cardiovascular and Medical Sciences, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8TT, UK.
| | - Laia Vidal-Brime
- Translational Molecular Pathology, Vall d'Hebron Institute of Research (VHIR), Autonomous University of Barcelona, CIBERONC, 08035 Barcelona, Spain.
| | - K Sabrina Lynn
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
| | - Michael Koval
- Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Department of Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA.
- Department of Cell Biology, Emory University School of Medicine, Atlanta, GA 30322, USA.
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13
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Two novel mutations identified in ADCC families impair crystallin protein distribution and induce apoptosis in human lens epithelial cells. Sci Rep 2017; 7:17848. [PMID: 29259299 PMCID: PMC5736644 DOI: 10.1038/s41598-017-18222-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Accepted: 12/07/2017] [Indexed: 01/20/2023] Open
Abstract
Congenital cataract (CC) is a clinical and genetically heterogeneous eye disease that primarily causes lens disorder and even amblyopic blindness in children. As the mechanism underlying CC is genetically inherited, identification of CC-associated gene mutations and their role in protein distribution are topics of both pharmacological and biological research. Through physical and ophthalmic examinations, two Chinese pedigrees with autosomal dominant congenital cataract (ADCC) were recruited for this study. Mutation analyses of CC candidate genes by next-generation sequencing (NGS) and Sanger sequencing revealed a novel missense mutation in CRYBB2 (p.V146L) and a deletion mutation in CRYAA (p.116_118del). Both mutations fully co-segregated were not observed in unaffected family members or in 100 unrelated healthy controls. The CRYBB2 missense mutation disrupts the distribution of CRYBB2 in human lens epithelial cells (HLEpiCs), and the CRYAA deletion mutation causes hyperdispersion of CRYAA. Furthermore, these two crystallin mutations result in aberrant expression of unfolded protein response (UPR) marker genes as well as apoptosis in HLEpiCs. Collectively, these findings broaden the genetic spectrum of ADCC.
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14
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Endoplasmic Reticulum Stress in Hearing Loss. JOURNAL OF OTORHINOLARYNGOLOGY, HEARING AND BALANCE MEDICINE 2017. [DOI: 10.3390/ohbm1010003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
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15
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Shiels A, Hejtmancik JF. Mutations and mechanisms in congenital and age-related cataracts. Exp Eye Res 2017; 156:95-102. [PMID: 27334249 PMCID: PMC5538314 DOI: 10.1016/j.exer.2016.06.011] [Citation(s) in RCA: 136] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2015] [Revised: 06/09/2016] [Accepted: 06/16/2016] [Indexed: 01/06/2023]
Abstract
The crystalline lens plays an important role in the refractive vision of vertebrates by facilitating variable fine focusing of light onto the retina. Loss of lens transparency, or cataract, is a frequently acquired cause of visual impairment in adults and may also present during childhood. Genetic studies have identified mutations in over 30 causative genes for congenital or other early-onset forms of cataract as well as several gene variants associated with age-related cataract. However, the pathogenic mechanisms resulting from genetic determinants of cataract are only just beginning to be understood. Here, we briefly summarize current concepts pointing to differences in the molecular mechanisms underlying congenital and age-related forms of cataract.
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Affiliation(s)
- Alan Shiels
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - J Fielding Hejtmancik
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD 20892-1860, USA.
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16
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Abstract
The lens is an avascular organ composed of an anterior epithelial cell layer and fiber cells that form the bulk of the organ. The lens expresses connexin43 (Cx43), connexin46 (Cx46) and connexin50 (Cx50). Epithelial Cx50 has critical roles in cell proliferation and differentiation, likely involving growth factor-dependent signaling pathways. Both Cx46 and Cx50 are crucial for lens transparency; mutations in their genes have been linked to congenital and age-related cataracts. Congenital cataract-associated connexin mutants can affect protein trafficking, stability and/or function, and the functional effects may differ between gap junction channels and hemichannels. Dominantly inherited cataracts may result from effects of the connexin mutant on its wild type isotype, the other co-expressed wild type connexin and/or its interaction with other cellular components.
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Affiliation(s)
| | - Anaclet Ngezahayo
- Institute of Biophysics, Leibniz University Hannover, Hannover, Germany.
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17
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Berthoud VM, Minogue PJ, Lambert PA, Snabb JI, Beyer EC. The Cataract-linked Mutant Connexin50D47A Causes Endoplasmic Reticulum Stress in Mouse Lenses. J Biol Chem 2016; 291:17569-78. [PMID: 27317663 DOI: 10.1074/jbc.m115.707950] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Indexed: 11/06/2022] Open
Abstract
Mice expressing connexin50D47A (Cx50D47A) exhibit nuclear cataracts and impaired differentiation. Cx50D47A does not traffic properly, and homozygous mutant lenses show increased levels of the stress-responsive αB-crystallins. Therefore, we assessed whether expression of Cx50D47A led to endoplasmic reticulum (ER) stress in the lens in vivo Although pharmacologic induction of ER stress can be transduced by three different pathways, we found no evidence for activation of the IRE1α or ATF6 pathways in Cx50D47A-expressing lenses. In contrast, heterozygous and homozygous Cx50D47A lenses showed an increase in phosphorylated PERK immunoreactivity and in the ratio of phosphorylated to total EIF2α (2.4- and 3.3-fold, respectively) compared with wild type. Levels of ATF4 were similar in wild type and heterozygous lenses but elevated in homozygotes (391%). In both heterozygotes and homozygotes, levels of calreticulin protein were increased (184 and 262%, respectively), as was Chop mRNA (1.9- and 12.4-fold, respectively). CHOP protein was increased in homozygotes (384%). TUNEL staining was increased in Cx50D47A lenses, especially in homozygous mice. Levels of two factors that may be pro-survival, Irs2 and Trib3, were greatly increased in homozygous lenses. These results suggest that expression of Cx50D47A induces ER stress, triggering activation of the PERK-ATF4 pathway, which potentially contributes to the lens pathology and leads to increased expression of anti-apoptotic factors, allowing cell survival.
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Affiliation(s)
| | | | - Paul A Lambert
- the Pritzker School of Medicine, University of Chicago, Chicago, Illinois 60637
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18
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Zhou Y, Bennett TM, Shiels A. Lens ER-stress response during cataract development in Mip-mutant mice. Biochim Biophys Acta Mol Basis Dis 2016; 1862:1433-42. [PMID: 27155571 DOI: 10.1016/j.bbadis.2016.05.003] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2016] [Revised: 04/25/2016] [Accepted: 05/03/2016] [Indexed: 12/22/2022]
Abstract
Major intrinsic protein (MIP) is a functional water-channel (AQP0) that also plays a key role in establishing lens fiber cell architecture. Genetic variants of MIP have been associated with inherited and age-related forms of cataract; however, the underlying pathogenic mechanisms are unclear. Here we have used lens transcriptome profiling by microarray-hybridization and qPCR to identify pathogenic changes during cataract development in Mip-mutant (Lop/+) mice. In postnatal Lop/+ lenses (P7) 99 genes were up-regulated and 75 were down-regulated (>2-fold, p=<0.05) when compared with wild-type. A pathway analysis of up-regulated genes in the Lop/+ lens (P7) was consistent with endoplasmic reticulum (ER)-stress and activation of the unfolded protein response (UPR). The most up-regulated UPR genes (>4-fold) in the Lop/+ lens included Chac1>Ddit3>Atf3>Trib3>Xbp1 and the most down-regulated genes (>5-fold) included two anti-oxidant genes, Hspb1 and Hmox1. Lop/+ lenses were further characterized by abundant TUNEL-positive nuclei within central degenerating fiber cells, glutathione depletion, free-radical overproduction, and calpain hyper-activation. These data suggest that Lop/+ lenses undergo proteotoxic ER-stress induced cell-death resulting from prolonged activation of the Eif2ak3/Perk-Atf4-Ddit3-Chac1 branch of the UPR coupled with severe oxidative-stress.
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Affiliation(s)
- Yuefang Zhou
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Thomas M Bennett
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Alan Shiels
- Department of Ophthalmology and Visual Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA.
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19
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Ma Z, Yao W, Chan CC, Kannabiran C, Wawrousek E, Hejtmancik JF. Human βA3/A1-crystallin splicing mutation causes cataracts by activating the unfolded protein response and inducing apoptosis in differentiating lens fiber cells. Biochim Biophys Acta Mol Basis Dis 2016; 1862:1214-27. [PMID: 26851658 DOI: 10.1016/j.bbadis.2016.02.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2015] [Revised: 01/16/2016] [Accepted: 02/02/2016] [Indexed: 11/15/2022]
Abstract
βγ-Crystallins, having a uniquely stable two domain four Greek key structure, are crucial for transparency of the eye lens,. Mutations in lens crystallins have been proposed to cause cataract formation by a variety of mechanisms most of which involve destabilization of the protein fold. The underlying molecular mechanism for autosomal dominant zonular cataracts with sutural opacities in an Indian family caused by a c.215+1G>A splice mutation in the βA3/A1-crystallin gene CRYBA1 was elucidated using three transgenic mice models. This mutation causes a splice defect in which the mutant mRNA escapes nonsense mediated decay by skipping both exons 3 and 4. Skipping these exons results in an in-frame deletion of the mRNA and synthesis of an unstable p.Ile33_Ala119del mutant βA3/A1-crystallin protein. Transgenic expression of mutant βA3/A1-crystallin but not the wild type protein results in toxicity and abnormalities in the maturation and orientation of differentiating lens fibers in c.97_357del CRYBA1 transgenic mice, leading to a small spherical lens, cataract, and often lens capsule rupture. On a cellular level, the lenses accumulated p.Ile33_Ala119del βA3/A1-crystallin with resultant activation of the stress signaling pathway - unfolded protein response (UPR) and inhibition of normal protein synthesis, culminating in apoptosis. This highlights the mechanistic contrast between mild mutations that destabilize crystallins and other proteins, resulting in their being bound by the α-crystallins that buffer lens cells against damage by denatured proteins, and severely misfolded proteins that are not bound by α-crystallin but accumulate and have a direct toxic effect on lens cells, resulting in early onset cataracts.
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Affiliation(s)
- Zhiwei Ma
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Wenliang Yao
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD, USA; Medimmune, Gaithersburg, MD, USA
| | | | - Chitra Kannabiran
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD, USA
| | - Eric Wawrousek
- Laboratory of Molecular and Developmental Biology, National Eye Institute, NIH, USA
| | - J Fielding Hejtmancik
- Ophthalmic Genetics and Visual Function Branch, National Eye Institute, National Institutes of Health, Bethesda, MD, USA.
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20
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Sala G, Badalamenti S, Ponticelli C. The Renal Connexome and Possible Roles of Connexins in Kidney Diseases. Am J Kidney Dis 2015; 67:677-87. [PMID: 26613807 DOI: 10.1053/j.ajkd.2015.09.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2015] [Accepted: 09/30/2015] [Indexed: 12/21/2022]
Abstract
Connexins are membrane-spanning proteins that allow for the formation of cell-to-cell channels and cell-to-extracellular space hemichannels. Many connexin subtypes are expressed in kidney cells. Some mutations in connexin genes have been linked to various human pathologies, including cardiovascular, neurodegenerative, lung, and skin diseases, but the exact role of connexins in kidney disease remains unclear. Some hypotheses about a connection between genetic mutations, endoplasmic reticulum (ER) stress, and the unfolded protein response (UPR) in kidney pathology have been explored. The potential relationship of kidney disease to abnormal production of connexin proteins, mutations in their genes together with ER stress, or the UPR is still a matter of debate. In this scenario, it is tantalizing to speculate about a possible role of connexins in the setting of kidney pathologies that are thought to be caused by a deregulated podocyte protein expression, the so-called podocytopathies. In this article, we give examples of the roles of connexins in kidney (patho)physiology and propose avenues for further research concerning connexins, ER stress, and UPR in podocytopathies that may ultimately help refine drug treatment.
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Affiliation(s)
- Gabriele Sala
- Nephrology and Dialysis Unit, Humanitas Clinical Research Center, Rozzano (Milano), Italy.
| | - Salvatore Badalamenti
- Nephrology and Dialysis Unit, Humanitas Clinical Research Center, Rozzano (Milano), Italy
| | - Claudio Ponticelli
- Nephrology and Dialysis Unit, Humanitas Clinical Research Center, Rozzano (Milano), Italy
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21
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Lyu L, Whitcomb EA, Jiang S, Chang ML, Gu Y, Duncan MK, Cvekl A, Wang WL, Limi S, Reneker LW, Shang F, Du L, Taylor A. Unfolded-protein response-associated stabilization of p27(Cdkn1b) interferes with lens fiber cell denucleation, leading to cataract. FASEB J 2015; 30:1087-95. [PMID: 26590164 DOI: 10.1096/fj.15-278036] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2015] [Accepted: 11/02/2015] [Indexed: 12/21/2022]
Abstract
Failure of lens fiber cell denucleation (LFCD) is associated with congenital cataracts, but the pathobiology awaits elucidation. Recent work has suggested that mechanisms that direct the unidirectional process of LFCD are analogous to the cyclic processes associated with mitosis. We found that lens-specific mutations that elicit an unfolded-protein response (UPR) in vivo accumulate p27(Cdkn1b), show cyclin-dependent kinase (Cdk)-1 inhibition, retain their LFC nuclei, and are cataractous. Although a UPR was not detected in lenses expressing K6W-Ub, they also accumulated p27 and showed failed LFCD. Induction of a UPR in human lens epithelial cells (HLECs) also induced accumulation of p27 associated with decreased levels of S-phase kinase-associated protein (Skp)-2, a ubiquitin ligase that regulates mitosis. These cells also showed decreased lamin A/C phosphorylation and metaphase arrest. The suppression of lamin A/C phosphorylation and metaphase transition induced by the UPR was rescued by knockdown of p27. Taken together, these data indicate that accumulation of p27, whether related to the UPR or not, prevents the phosphorylation of lamin A/C and LFCD in maturing LFCs in vivo, as well as in dividing HLECs. The former leads to cataract and the latter to metaphase arrest. These results suggest that accumulation of p27 is a common mechanism underlying retention of LFC nuclei.
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Affiliation(s)
- Lei Lyu
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Elizabeth A Whitcomb
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Shuhong Jiang
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Min-Lee Chang
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Yumei Gu
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Melinda K Duncan
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Ales Cvekl
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Wei-Lin Wang
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Saima Limi
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Lixing W Reneker
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Fu Shang
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Linfang Du
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
| | - Allen Taylor
- *Ministry of Education Key Laboratory of Bio-resource and Eco-environment, College of Life Science, Sichuan University, Sichuan China; Laboratory for Nutrition and Vision Research, Jean Mayer U.S. Department of Agriculture Human Nutrition Research Center on Aging, Tufts University, Boston, Massachusetts, USA; Department of Biological Sciences, University of Delaware, Newark, Delaware, USA; Department of Genetics and Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, New York, USA; and Department of Ophthalmology, School of Medicine, University of Missouri, Columbia, Missouri, USA
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Kelly JJ, Simek J, Laird DW. Mechanisms linking connexin mutations to human diseases. Cell Tissue Res 2014; 360:701-21. [DOI: 10.1007/s00441-014-2024-4] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2014] [Accepted: 09/26/2014] [Indexed: 11/30/2022]
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Berthoud VM, Minogue PJ, Yu H, Snabb JI, Beyer EC. Connexin46fs380 causes progressive cataracts. Invest Ophthalmol Vis Sci 2014; 55:6639-48. [PMID: 25103261 PMCID: PMC4207115 DOI: 10.1167/iovs.14-15012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2014] [Accepted: 07/28/2014] [Indexed: 01/17/2023] Open
Abstract
PURPOSE Although many connexin46 (Cx46) mutants have been linked to inherited human cataracts, there are no adequate animal models for their study. The current experiments were designed to characterize the consequences of expression of one such mutant, Cx46fs380, in the mouse lens. METHODS Mice expressing Cx46fs380 were generated by a knockin strategy. Levels and distribution of specific proteins were analyzed by immunoblotting and immunofluorescence. RESULTS Dark-field microscopy revealed that lenses of young heterozygous and homozygous Cx46fs380 mice did not have opacities, but they developed anterior nuclear cataracts that became more severe with age. Immunofluorescence and immunoblotting showed that Cx46 was severely reduced in both heterozygous and homozygous Cx46fs380 lenses at 1 month of age, whereas immunoreactive connexin50 (Cx50) was moderately decreased. The reduction in Cx50 became more severe in older lenses. The solubilities of crystallins from young wild-type and fs380 mice were similar, but older fs380 lenses exhibited abnormalities of abundance, solubility, and modification of some crystallins. CONCLUSIONS Major decreases in connexin levels precede the development of cataracts. These mice represent a useful model for elucidation of the progression of lens abnormalities during cataractogenesis especially as caused by a mutant connexin.
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Affiliation(s)
- Viviana M Berthoud
- Department of Pediatrics, University of Chicago, Chicago, Illinois, United States
| | - Peter J Minogue
- Department of Pediatrics, University of Chicago, Chicago, Illinois, United States
| | - Helena Yu
- Department of Pediatrics, University of Chicago, Chicago, Illinois, United States
| | - Joseph I Snabb
- Department of Pediatrics, University of Chicago, Chicago, Illinois, United States
| | - Eric C Beyer
- Department of Pediatrics, University of Chicago, Chicago, Illinois, United States
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Berger AC, Kelly JJ, Lajoie P, Shao Q, Laird DW. Mutations in Cx30 that are linked to skin disease and non-syndromic hearing loss exhibit several distinct cellular pathologies. J Cell Sci 2014; 127:1751-64. [DOI: 10.1242/jcs.138230] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
ABSTRACT
Connexin 30 (Cx30), a member of the large gap-junction protein family, plays a role in the homeostasis of the epidermis and inner ear through gap junctional intercellular communication (GJIC). Here, we investigate the underlying mechanisms of four autosomal dominant Cx30 gene mutations that are linked to hearing loss and/or various skin diseases. First, the T5M mutant linked to non-syndromic hearing loss formed functional gap junction channels and hemichannels, similar to wild-type Cx30. The loss-of-function V37E mutant associated with Clouston syndrome or keratitis-ichthyosis-deafness syndrome was retained in the endoplasmic reticulum and significantly induced apoptosis. The G59R mutant linked to the Vohwinkel and Bart-Pumphrey syndromes was retained primarily in the Golgi apparatus and exhibited loss of gap junction channel and hemichannel function but did not cause cell death. Lastly, the A88V mutant, which is linked to the development of Clouston syndrome, also significantly induced apoptosis but through an endoplasmic-reticulum-independent mechanism. Collectively, we discovered that four unique Cx30 mutants might cause disease through different mechanisms that also likely include their selective trans-dominant effects on coexpressed connexins, highlighting the overall complexity of connexin-linked diseases and the importance of GJIC in disease prevention.
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Affiliation(s)
- Amy C. Berger
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - John J. Kelly
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Patrick Lajoie
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Qing Shao
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
| | - Dale W. Laird
- Department of Physiology and Pharmacology, University of Western Ontario, London, ON N6A 5C1, Canada
- Department of Anatomy and Cell Biology, University of Western Ontario, London, ON N6A 5C1, Canada
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25
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Berthoud VM, Minogue PJ, Yu H, Schroeder R, Snabb JI, Beyer EC. Connexin50D47A decreases levels of fiber cell connexins and impairs lens fiber cell differentiation. Invest Ophthalmol Vis Sci 2013; 54:7614-22. [PMID: 24204043 PMCID: PMC3835270 DOI: 10.1167/iovs.13-13188] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 09/30/2013] [Indexed: 11/24/2022] Open
Abstract
PURPOSE Substitutions of aspartate-47 (D47) of Connexin50 (Cx50) have been linked to autosomal dominant congenital cataracts in several human pedigrees. To elucidate the lens abnormalities caused by a substitution at this position, we studied No2 mice, which carry the Cx50D47A mutation and parallel the human pathology. METHODS Lenses from mice of different ages (neonatal to 4 months) were examined by dark-field and immunofluorescence microscopy. Protein levels were determined by immunoblotting using primary antibodies directed against connexins, other membrane proteins, crystallins, and proteins residing in different organelles. RESULTS Lenses of both heterozygous and homozygous Cx50D47A mice had cataracts and were smaller than those of wild-type littermates. Levels of Cx50 were severely reduced in mutant animals as compared with those in wild-type mice (<20% in heterozygotes and ≤3% in homozygotes). Levels of Cx46 and aquaporin0 were also decreased, but to a lesser extent. The immunostaining pattern of lens connexins was altered in mutant animals. The lenses of Cx50D47A mice showed persistence of nuclear remnants in deep regions of the lens and elevated levels of H3 histone and the mitochondrial protein, Tom20. γ-Crystallin levels were decreased in lenses of all mutant mice, and β-crystallins were reduced in homozygotes. CONCLUSIONS These data suggest that mice expressing Cx50D47A develop cataracts due to a severe decrease in the abundance of functional connexin channels. They also implicate Cx50 in fiber cell differentiation, since mutant lenses showed impaired degradation of organelles and decreased levels of some crystallins.
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Beyer EC, Ebihara L, Berthoud VM. Connexin mutants and cataracts. Front Pharmacol 2013; 4:43. [PMID: 23596416 PMCID: PMC3625720 DOI: 10.3389/fphar.2013.00043] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2013] [Accepted: 03/26/2013] [Indexed: 10/27/2022] Open
Abstract
The lens is a multicellular, but avascular tissue that must stay transparent to allow normal transmission of light and focusing of it on the retina. Damage to lens cells and/or proteins can cause cataracts, opacities that disrupt these processes. The normal survival of the lens is facilitated by an extensive network of gap junctions formed predominantly of connexin46 and connexin50. Mutations of the genes that encode these connexins (GJA3 and GJA8) have been identified and linked to inheritance of cataracts in human families and mouse lines. In vitro expression studies of several of these mutants have shown that they exhibit abnormalities that may lead to disease. Many of the mutants reduce or modify intercellular communication due to channel alterations (including loss of function or altered gating) or due to impaired cellular trafficking which reduces the number of gap junction channels within the plasma membrane. However, the abnormalities detected in studies of other mutants suggest that they cause cataracts through other mechanisms including gain of hemichannel function (leading to cell injury and death) and formation of cytoplasmic accumulations (that may act as light scattering particles). These observations and the anticipated results of ongoing studies should elucidate the mechanisms of cataract development due to mutations of lens connexins and abnormalities of other lens proteins. They may also contribute to our understanding of the mechanisms of disease due to connexin mutations in other tissues.
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Affiliation(s)
- Eric C Beyer
- Department of Pediatrics, University of Chicago Chicago, IL, USA
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