1
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Sugiyama Y, Murthy VV, Mbogo I, Morohashi Y, Masai I, Lovicu FJ. Concave-to-convex curve conversion of fiber cells correlates with Y-shaped suture formation at the poles of the rodent lens. Exp Eye Res 2024; 248:110066. [PMID: 39233305 DOI: 10.1016/j.exer.2024.110066] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2024] [Revised: 08/08/2024] [Accepted: 08/31/2024] [Indexed: 09/06/2024]
Abstract
The eye lens contains convexly curved fiber cells that align in concentric layers around the lens anterior-posterior pole axis. For lens fiber differentiation at the equator, cells elongate with their apical and basal tips migrating towards the anterior and posterior poles, respectively. At each pole, the fiber tips meet opposing tips of other fiber cells, to form a suture. Although umbilical or point sutures are observed in fish and birds, line, Y- or star-shaped sutures are detected in other vertebrate lenses. Sutures that do not converge at the point are thought to result from intricate movements of the fiber tips, rather than a straightforward migration along a meridional path. The triggers that give rise to these variations are currently not understood. Our findings revealed that in the mouse embryo, the early-stage lens contains only concave curved fibers, and later, a zone of concave-to-convex curve conversion develops. At this point, a nascent suture in a linear shape appears at the posterior pole and subsequently progresses into a V-shape. This V-shape appears to further develop into a Y-shape as a branch extends from the apex of the V-shape. In lens of zebrafish and Xenopus larvae that form point sutures, this curve-conversion zone is not observed. In lens of adult birds (e.g. zebra finch) that form a point suture, these too also lack a curve-conversion zone. In our previous studies, we demonstrated that murine lens fibers undergoing curve conversion extend membrane protrusions, or lamellipodia, at their basal membranes. In line with this, we did not observe protrusions at the basal tips of fibers in the non-mammalian lenses of zebrafish, Xenopus, and zebra finch in which curve conversion does not occur. We propose that the concave-to-convex conversion in rodent lenses introduces defined paths for fiber cell tips, leading to a more elaborate and complex suture formation, compared to the simple point suture of lower vertebrates.
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Affiliation(s)
- Yuki Sugiyama
- Save Sight Institute, The University of Sydney, Sydney, NSW, 2000, Australia; Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan; Molecular Cellular Biology Laboratory, Yokohama City University Graduate School of Medical Life Science, Tsurumi-ku, Yokohama, 230-0045, Japan.
| | - Varsha Venkatesha Murthy
- Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan
| | - Ivan Mbogo
- Evolutionary Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan
| | - Yuichi Morohashi
- Neuronal Mechanism for Critical Period Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan
| | - Ichiro Masai
- Developmental Neurobiology Unit, Okinawa Institute of Science and Technology Graduate University, Onna, Okinawa, 904-0495, Japan
| | - Frank J Lovicu
- Save Sight Institute, The University of Sydney, Sydney, NSW, 2000, Australia; Molecular and Cellular Biomedicine, School of Medical Sciences, The University of Sydney, Sydney, NSW, 2006, Australia
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2
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de Almeida Magalhaes T, Liu J, Chan C, Borges KS, Zhang J, Kane AJ, Wierbowski BM, Ge Y, Liu Z, Mannam P, Zeve D, Weiss R, Breault DT, Huang P, Salic A. Extracellular carriers control lipid-dependent secretion, delivery, and activity of WNT morphogens. Dev Cell 2024; 59:244-261.e6. [PMID: 38154460 PMCID: PMC10872876 DOI: 10.1016/j.devcel.2023.11.027] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2023] [Revised: 08/29/2023] [Accepted: 11/30/2023] [Indexed: 12/30/2023]
Abstract
WNT morphogens trigger signaling pathways fundamental for embryogenesis, regeneration, and cancer. WNTs are modified with palmitoleate, which is critical for binding Frizzled (FZD) receptors and activating signaling. However, it is unknown how WNTs are released and spread from cells, given their strong lipid-dependent membrane attachment. We demonstrate that secreted FZD-related proteins and WNT inhibitory factor 1 are WNT carriers, potently releasing lipidated WNTs and forming active soluble complexes. WNT release occurs by direct handoff from the membrane protein WNTLESS to the carriers. In turn, carriers donate WNTs to glypicans and FZDs involved in WNT reception and to the NOTUM hydrolase, which antagonizes WNTs by lipid moiety removal. WNT transfer from carriers to FZDs is greatly facilitated by glypicans that serve as essential co-receptors in Wnt signaling. Thus, an extracellular network of carriers dynamically controls secretion, posttranslational regulation, and delivery of WNT morphogens, with important practical implications for regenerative medicine.
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Affiliation(s)
| | - Jingjing Liu
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Charlene Chan
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Kleiton Silva Borges
- Division of Endocrinology, Boston Children's Hospital, Boston, MA 02115, USA; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
| | - Jiuchun Zhang
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Andrew J Kane
- Synthetic Biology Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Bradley M Wierbowski
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA
| | - Yunhui Ge
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Zhiwen Liu
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Prabhath Mannam
- Division of Endocrinology, Boston Children's Hospital, Boston, MA 02115, USA
| | - Daniel Zeve
- Division of Endocrinology, Boston Children's Hospital, Boston, MA 02115, USA; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA
| | - Ron Weiss
- Synthetic Biology Center, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - David T Breault
- Division of Endocrinology, Boston Children's Hospital, Boston, MA 02115, USA; Department of Pediatrics, Harvard Medical School, Boston, MA 02115, USA; Harvard Stem Cell Institute, 7 Divinity Avenue, Cambridge, MA 02138, USA
| | - Pengxiang Huang
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
| | - Adrian Salic
- Department of Cell Biology, Blavatnik Institute, Harvard Medical School, Boston, MA 02115, USA.
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3
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Zhang Z, Lin X, Wei L, Wu Y, Xu L, Wu L, Wei X, Zhao S, Zhu X, Xu F. A framework for Frizzled-G protein coupling and implications to the PCP signaling pathways. Cell Discov 2024; 10:3. [PMID: 38182578 PMCID: PMC10770037 DOI: 10.1038/s41421-023-00627-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2023] [Accepted: 11/19/2023] [Indexed: 01/07/2024] Open
Abstract
The ten Frizzled receptors (FZDs) are essential in Wnt signaling and play important roles in embryonic development and tumorigenesis. Among these, FZD6 is closely associated with lens development. Understanding FZD activation mechanism is key to unlock these emerging targets. Here we present the cryo-EM structures of FZD6 and FZD3 which are known to relay non-canonical planar cell polarity (PCP) signaling pathways as well as FZD1 in their G protein-coupled states and in the apo inactive states, respectively. Comparison of the three inactive/active pairs unveiled a shared activation framework among all ten FZDs. Mutagenesis along with imaging and functional analysis on the human lens epithelial tissues suggested potential crosstalk between the G-protein coupling of FZD6 and the PCP signaling pathways. Together, this study provides an integrated understanding of FZD structure and function, and lays the foundation for developing therapeutic modulators to activate or inhibit FZD signaling for a range of disorders including cancers and cataracts.
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Affiliation(s)
- Zhibin Zhang
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Xi Lin
- iHuman Institute, ShanghaiTech University, Shanghai, China
| | - Ling Wei
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, China
| | - Yiran Wu
- iHuman Institute, ShanghaiTech University, Shanghai, China
| | - Lu Xu
- iHuman Institute, ShanghaiTech University, Shanghai, China
| | - Lijie Wu
- iHuman Institute, ShanghaiTech University, Shanghai, China
| | - Xiaohu Wei
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Suwen Zhao
- iHuman Institute, ShanghaiTech University, Shanghai, China
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China
| | - Xiangjia Zhu
- Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, Shanghai, China.
| | - Fei Xu
- iHuman Institute, ShanghaiTech University, Shanghai, China.
- School of Life Science and Technology, ShanghaiTech University, Shanghai, China.
- Shanghai Clinical Research and Trial Center, Shanghai, China.
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4
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Yamada R, Oguri A, Fujiki K, Shirahige K, Hirate Y, Kanai-Azuma M, Takezoe H, Akimoto Y, Takahashi N, Kanai Y. MAB21L1 modulates gene expression and DNA metabolic processes in the lens placode. Dis Model Mech 2021; 14:dmm049251. [PMID: 34779479 PMCID: PMC8713989 DOI: 10.1242/dmm.049251] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2021] [Accepted: 11/09/2021] [Indexed: 11/20/2022] Open
Abstract
Mutations in human MAB21L1 cause aberrations in lens ectoderm morphogenesis and lead to congenital cerebellar, ocular, craniofacial and genital (COFG) syndrome. Murine Mab21l1-null mutations cause severe cell-autonomous defects in lens formation, leading to microphthalmia; therefore, Mab21l1-null mice are used as a mouse model for COFG syndrome. In this study, we investigated the early-onset single-cell-level phenotypes of murine Mab21l1-null lens ectoderms using electron microscopy and single-cell RNA sequencing (scRNA-seq). Electron microscopy and immunohistochemical analyses indicated endoplasmic reticulum stress at the 24- to 26-somite stage in Mab21l1-null lens placodes. scRNA-seq analysis revealed that 131 genes were downregulated and 148 were upregulated in Mab21l1-null lens ectoderms relative to the wild type. We successfully identified 21 lens-specific genes that were downregulated in Mab21l1-null cells, including three key genes involved in lens formation: Pitx3, Maf and Sfrp2. Moreover, gene ontology analysis of the 279 differentially expressed genes indicated enrichment in housekeeping genes associated with DNA/nucleotide metabolism prior to cell death. These findings suggest that MAB21L1 acts as a nuclear factor that modulates not only lens-specific gene expression but also DNA/nucleotide metabolic processes during lens placode formation.
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Affiliation(s)
- Ryuichi Yamada
- Department of Veterinary Anatomy, the University of Tokyo, Tokyo 113-8657, Japan
- Department of Applied Biological Chemistry, the University of Tokyo, Tokyo 113-8657, Japan
- RNA Company Limited, Tokyo 144-0051, Japan
| | - Akira Oguri
- Department of Applied Biological Chemistry, the University of Tokyo, Tokyo 113-8657, Japan
| | - Katsunori Fujiki
- Laboratory of Genome Structure and Function, Institute for Quantitative Biosciences, the University of Tokyo, Tokyo 113-0032, Japan
| | - Katsuhiko Shirahige
- Laboratory of Genome Structure and Function, Institute for Quantitative Biosciences, the University of Tokyo, Tokyo 113-0032, Japan
| | - Yoshikazu Hirate
- Department of Experimental Animal Model for Human Disease, Center for Experimental Animals, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | - Masami Kanai-Azuma
- Department of Experimental Animal Model for Human Disease, Center for Experimental Animals, Tokyo Medical and Dental University, Tokyo 113-8510, Japan
| | | | - Yoshihiro Akimoto
- Department of Anatomy, Kyorin University School of Medicine, Tokyo 181-8611, Japan
| | - Naoki Takahashi
- Department of Applied Biological Chemistry, the University of Tokyo, Tokyo 113-8657, Japan
- RNA Company Limited, Tokyo 144-0051, Japan
| | - Yoshiakira Kanai
- Department of Veterinary Anatomy, the University of Tokyo, Tokyo 113-8657, Japan
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5
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Secreted Frizzled-Related Protein 1 Promotes Odontoblastic Differentiation and Reparative Dentin Formation in Dental Pulp Cells. Cells 2021; 10:cells10092491. [PMID: 34572140 PMCID: PMC8468928 DOI: 10.3390/cells10092491] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Revised: 09/07/2021] [Accepted: 09/15/2021] [Indexed: 01/09/2023] Open
Abstract
Direct pulp capping is an effective treatment for preserving dental pulp against carious or traumatic pulp exposure via the formation of protective reparative dentin by odontoblast-like cells. Reparative dentin formation can be stimulated by several signaling molecules; therefore, we investigated the effects of secreted frizzled-related protein (SFRP) 1 that was reported to be strongly expressed in odontoblasts of newborn molar tooth germs on odontoblastic differentiation and reparative dentin formation. In developing rat incisors, cells in the dental pulp, cervical loop, and inner enamel epithelium, as well as ameloblasts and preodontoblasts, weakly expressed Sfrp1; however, Sfrp1 was strongly expressed in mature odontoblasts. Human dental pulp cells (hDPCs) showed stronger expression of SFRP1 compared with periodontal ligament cells and gingival cells. SFRP1 knockdown in hDPCs abolished calcium chloride-induced mineralized nodule formation and odontoblast-related gene expression and decreased BMP-2 gene expression. Conversely, SFRP1 stimulation enhanced nodule formation and expression of BMP-2. Direct pulp capping treatment with SFRP1 induced the formation of a considerable amount of reparative dentin that has a structure similar to primary dentin. Our results indicate that SFRP1 is crucial for dentinogenesis and is important in promoting reparative dentin formation in response to injury.
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Guan H, Zhang J, Luan J, Xu H, Huang Z, Yu Q, Gou X, Xu L. Secreted Frizzled Related Proteins in Cardiovascular and Metabolic Diseases. Front Endocrinol (Lausanne) 2021; 12:712217. [PMID: 34489867 PMCID: PMC8417734 DOI: 10.3389/fendo.2021.712217] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2021] [Accepted: 07/23/2021] [Indexed: 11/13/2022] Open
Abstract
Abnormal gene expression and secreted protein levels are accompanied by extensive pathological changes. Secreted frizzled related protein (SFRP) family members are antagonistic inhibitors of the Wnt signaling pathway, and they were recently found to be involved in the pathogenesis of a variety of metabolic diseases, which has led to extensive interest in SFRPs. Previous reports highlighted the importance of SFRPs in lipid metabolism, obesity, type 2 diabetes mellitus and cardiovascular diseases. In this review, we provide a detailed introduction of SFRPs, including their structural characteristics, receptors, inhibitors, signaling pathways and metabolic disease impacts. In addition to summarizing the pathologies and potential molecular mechanisms associated with SFRPs, this review further suggests the potential future use of SFRPs as disease biomarkers therapeutic targets.
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Affiliation(s)
- Hua Guan
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Engineering Research Center for Dental Materials and Advanced Manufacture, Department of Anethesiology, School of Stomatology, Fourth Military Medical University, Xi’an, China
- Shaanxi Key Laboratory of Ischemic Cardiovascular Disease, Institute of Basic and Translational Medicine, Xi’an Medical University, Xi’an, China
| | - Jin Zhang
- Department of Preventive Medicine, School of Stomatology, Fourth Military Medical University, Xi’an, China
| | - Jing Luan
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Engineering Research Center for Dental Materials and Advanced Manufacture, Department of Anethesiology, School of Stomatology, Fourth Military Medical University, Xi’an, China
- Shaanxi Key Laboratory of Brain Disorders & Institute of Basic and Translational Medicine, Xi’an Medical University, Xi’an, China
| | - Hao Xu
- Institution of Basic Medical Science, Xi’an Medical University, Xi’an, China
| | - Zhenghao Huang
- Shaanxi Key Laboratory of Ischemic Cardiovascular Disease, Institute of Basic and Translational Medicine, Xi’an Medical University, Xi’an, China
| | - Qi Yu
- Shaanxi Key Laboratory of Ischemic Cardiovascular Disease, Institute of Basic and Translational Medicine, Xi’an Medical University, Xi’an, China
| | - Xingchun Gou
- Shaanxi Key Laboratory of Brain Disorders & Institute of Basic and Translational Medicine, Xi’an Medical University, Xi’an, China
- *Correspondence: Lixian Xu, ; Xingchun Gou,
| | - Lixian Xu
- State Key Laboratory of Military Stomatology & National Clinical Research Center for Oral Diseases & Shaanxi Engineering Research Center for Dental Materials and Advanced Manufacture, Department of Anethesiology, School of Stomatology, Fourth Military Medical University, Xi’an, China
- *Correspondence: Lixian Xu, ; Xingchun Gou,
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7
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Kobayashi Y, Hayashi R, Shibata S, Quantock AJ, Nishida K. Ocular surface ectoderm instigated by WNT inhibition and BMP4. Stem Cell Res 2020; 46:101868. [PMID: 32603880 PMCID: PMC7347012 DOI: 10.1016/j.scr.2020.101868] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2019] [Revised: 03/27/2020] [Accepted: 05/20/2020] [Indexed: 12/13/2022] Open
Abstract
We sought to elucidate how and when the ocular surface ectoderm commits to its differentiation into the corneal epithelium in eye development from human induced pluripotent stem cells (hiPSCs) under the influence of WNT signaling and the actions of BMP4. These signals are key drivers ocular surface ectodermal cell fate determination. It was discovered that secreted frizzled related protein-2 (SFRP2) and Dickkopf1 (DKK1), which are expressed in neural ectoderm, are both influential in the differentiation of hiPSCs, where they act as canonical WNT antagonists. BMP4, moreover, was found to simultaneously initiate non-neural ectodermal differentiation into a corneal epithelial lineage. Combined treatment of hiPSCs with exogenous BMP4 aligned to WNT inhibition for the initial four days of differentiation increased the ocular surface ectodermal cell population and induced a corneal epithelial phenotype. Specification of a surface ectodermal lineage and its fate is thus determined by a fine balance of BMP4 exposure and WNT inhibition in the very earliest stages of human eye development.
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Affiliation(s)
- Yuki Kobayashi
- Department of Ophthalmology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan; Department of Stem Cells and Applied Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan
| | - Ryuhei Hayashi
- Department of Ophthalmology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan; Department of Stem Cells and Applied Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
| | - Shun Shibata
- Department of Stem Cells and Applied Medicine, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan; Research and Development Division, ROHTO Pharmaceutical Co Ltd, Osaka, Osaka 544-8666, Japan
| | - Andrew J Quantock
- Structural Biophysics Group, School of Optometry and Vision Sciences, College of Biomedical and Life Sciences, Cardiff University, Cardiff, CF24 4HQ Wales, UK
| | - Kohji Nishida
- Department of Ophthalmology, Osaka University Graduate School of Medicine, 2-2 Yamadaoka, Suita, Osaka 565-0871, Japan; Integrated Frontier Research for Medical Science Division, Institute for Open and Transdisciplinary Research Initiatives (OTRI), Osaka University, Suita, Osaka 565-0871, Japan
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8
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Esteve P, Crespo I, Kaimakis P, Sandonís A, Bovolenta P. Sfrp1 Modulates Cell-signaling Events Underlying Telencephalic Patterning, Growth and Differentiation. Cereb Cortex 2020; 29:1059-1074. [PMID: 30084950 DOI: 10.1093/cercor/bhy013] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 01/09/2018] [Indexed: 12/19/2022] Open
Abstract
The mammalian dorsal telencephalic neuroepithelium develops-from medial to lateral-into the choroid plaque, cortical hem, hippocampal primordium and isocortex under the influence of Bmp, Wnt and Notch signaling. Correct telencephalic development requires a tight coordination of the extent/duration of these signals, but the identification of possible molecular coordinators is still limited. Here, we postulated that Secreted Frizzled Related Protein 1 (Sfrp1), a multifunctional regulator of Bmp, Wnt and Notch signaling strongly expressed during early telencephalic development, may represent 1 of such molecules. We report that in E10.5-E12.5 Sfrp1-/- embryos, the hem and hippocampal domains are reduced in size whereas the prospective neocortex is medially extended. These changes are associated with a significant reduction of the medio-lateral telencephalic expression of Axin2, a read-out of Wnt/βcatenin signaling activation. Furthermore, in the absence of Sfrp1, Notch signaling is increased, cortical progenitor cell cycle is shorter, with expanded progenitor pools and enhanced generation of early-born neurons. Hence, in postnatal Sfrp1-/- animals the anterior hippocampus is reduced and the neocortex is shorter in the antero-posterior and medio-lateral axis but is thicker. We propose that, by controlling Wnt and Notch signaling in opposite directions, Sfrp1 promotes hippocampal patterning and balances medio-lateral and antero-posterior cortex expansion.
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Affiliation(s)
- Pilar Esteve
- Centro de Biología Molecular "Severo Ochoa", CSIC-UAM and CIBER de Enfermedades Raras (CIBERER), c/Nicolás Cabrera, Madrid, Spain
| | - Inmaculada Crespo
- Centro de Biología Molecular "Severo Ochoa", CSIC-UAM and CIBER de Enfermedades Raras (CIBERER), c/Nicolás Cabrera, Madrid, Spain
| | - Polynikis Kaimakis
- Centro de Biología Molecular "Severo Ochoa", CSIC-UAM and CIBER de Enfermedades Raras (CIBERER), c/Nicolás Cabrera, Madrid, Spain
| | - Africa Sandonís
- Centro de Biología Molecular "Severo Ochoa", CSIC-UAM and CIBER de Enfermedades Raras (CIBERER), c/Nicolás Cabrera, Madrid, Spain
| | - Paola Bovolenta
- Centro de Biología Molecular "Severo Ochoa", CSIC-UAM and CIBER de Enfermedades Raras (CIBERER), c/Nicolás Cabrera, Madrid, Spain
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9
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Cisneros E, di Marco F, Rueda-Carrasco J, Lillo C, Pereyra G, Martín-Bermejo MJ, Vargas A, Sanchez R, Sandonís Á, Esteve P, Bovolenta P. Sfrp1 deficiency makes retinal photoreceptors prone to degeneration. Sci Rep 2020; 10:5115. [PMID: 32198470 PMCID: PMC7083943 DOI: 10.1038/s41598-020-61970-8] [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] [Received: 12/13/2019] [Accepted: 03/05/2020] [Indexed: 12/11/2022] Open
Abstract
Millions of individuals worldwide suffer from impaired vision, a condition with multiple origins that often impinge upon the light sensing cells of the retina, the photoreceptors, affecting their integrity. The molecular components contributing to this integrity are however not yet fully understood. Here we have asked whether Secreted Frizzled Related Protein 1 (SFRP1) may be one of such factors. SFRP1 has a context-dependent function as modulator of Wnt signalling or of the proteolytic activity of A Disintegrin And Metalloproteases (ADAM) 10, a main regulator of neural cell-cell communication. We report that in Sfrp1−/− mice, the outer limiting membrane (OLM) is discontinuous and the photoreceptors disorganized and more prone to light-induced damage. Sfrp1 loss significantly enhances the effect of the Rpe65Leu450Leu genetic variant -present in the mouse genetic background- which confers sensitivity to light-induced stress. These alterations worsen with age, affect visual function and are associated to an increased proteolysis of Protocadherin 21 (PCDH21), localized at the photoreceptor outer segment, and N-cadherin, an OLM component. We thus propose that SFRP1 contributes to photoreceptor fitness with a mechanism that involves the maintenance of OLM integrity. These conclusions are discussed in view of the broader implication of SFRP1 in neurodegeneration and aging.
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Affiliation(s)
- Elsa Cisneros
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.,Departamento de Biología Celular y Patología, Universidad de Salamanca, Instituto de Neurociencias de Castilla y León and IBSAL, Salamanca, Spain.,Centro Universitario Internacional de Madrid (CUNIMAD), Dept. de Biología de Sistemas, Universidad de Alcalá, Madrid, Spain
| | - Fabiana di Marco
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain
| | | | - Concepción Lillo
- Departamento de Biología Celular y Patología, Universidad de Salamanca, Instituto de Neurociencias de Castilla y León and IBSAL, Salamanca, Spain
| | | | | | - Alba Vargas
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain
| | - Rocío Sanchez
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain
| | - África Sandonís
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Pilar Esteve
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Paola Bovolenta
- Centro de Biología Molecular Severo Ochoa, CSIC-UAM, Madrid, Spain. .,Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain.
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10
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Abstract
Cell-to-cell communication is fundamental for embryo development and subsequent tissue homeostasis. This communication is often mediated by a small number of signaling pathways in which a secreted ligand binds to the surface of a target cell, thereby activating signal transduction. In vertebrate neural development, these signaling mechanisms are repeatedly used to obtain different and context-dependent outcomes. Part of the versatility of these communication mechanisms depends on their finely tuned regulation that controls timing, spatial localization, and duration of the signaling. The existence of secreted antagonists, which prevent ligand–receptor interaction, is an efficient mechanism to regulate some of these pathways. The Hedgehog family of signaling proteins, however, activates a pathway that is controlled largely by the positive or negative activity of membrane-bound proteins such as Cdon, Boc, Gas1, or Megalin/LRP2. In this review, we will use the development of the vertebrate retina, from its early specification to neurogenesis, to discuss whether there is an advantage to the use of such regulators, pointing to unresolved or controversial issues.
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Affiliation(s)
- Viviana Gallardo
- Centro de Biología Molecular , CSIC-UAM, Madrid, 28049, Spain.,CIBER de Enfermedades Raras (CIBERER), Madrid, 28029, Spain
| | - Paola Bovolenta
- Centro de Biología Molecular , CSIC-UAM, Madrid, 28049, Spain.,CIBER de Enfermedades Raras (CIBERER), Madrid, 28029, Spain
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11
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Hua Y, Yang Y, Li Q, He X, Zhu W, Wang J, Gan X. Oligomerization of Frizzled and LRP5/6 protein initiates intracellular signaling for the canonical WNT/β-catenin pathway. J Biol Chem 2018; 293:19710-19724. [PMID: 30361437 DOI: 10.1074/jbc.ra118.004434] [Citation(s) in RCA: 45] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 10/24/2018] [Indexed: 12/19/2022] Open
Abstract
Upon binding to the canonical WNT glycoproteins, Frizzled family receptors (FZDs) and low-density lipoprotein receptor-related protein 5/6 (LRP5/6) undergo a series of polymerizations on the cell surface that elicit canonical WNT/β-catenin signaling. The hyperactivation of WNT/β-catenin signaling is the major cause of tumorigenesis, but the mechanism in tumors such as hepatoma remains unclear. Here, we observed that WNT3A manifested the hyperactivity in β-catenin-dependent signaling after binding to FZD's competitive inhibitory molecule secreted Frizzled-related protein 2 (SFRP2). To understand the mechanism of FZDs in the presence of SFRP2, we explored how FZDs can bind and activate the LRP5/6 signalosome independently of WNT glycoproteins. Our findings further revealed that oligomerizations of FZDs and LRP5/6 can integrate the cytoplasmic protein Dishevelled into the LRP5/6 signalosome, resulting in a robust activation of ligand-independent β-catenin signaling. We propose that besides WNT-bridged FZD-WNT-LRP5/6 protein complexes, the homo- and hetero-oligomerizations of WNT receptors may contribute to the formation of the LRP5/6 signalosome on the cell surface. Of note, we identified four highly expressed FZDs in the hepatoma cell line HepG2, all of which significantly promoted ligand-independent LRP5/β-catenin signaling. As FZDs are ectopically expressed in numerous tumors, our findings may provide a new perspective on tumor pathologies. Furthermore, the results in our study suggest that the composition and stoichiometry of FZDs and LRP5/6 within the LRP5/6 signalosome may tune the selection of bound WNT glycoproteins and configure downstream WNT/β-catenin signaling.
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Affiliation(s)
- Yue Hua
- From the Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Yilin Yang
- From the Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Qian Li
- From the Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Xinyu He
- From the Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Wei Zhu
- From the Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Jiyong Wang
- From the Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
| | - Xiaoqing Gan
- From the Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai 200032, China
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12
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Chen L, Peng W, Kong S, Pu F, Chen B, Zhou Z, Feng J, Li X, Xu P. Genetic Mapping of Head Size Related Traits in Common Carp ( Cyprinus carpio). Front Genet 2018; 9:448. [PMID: 30356829 PMCID: PMC6190898 DOI: 10.3389/fgene.2018.00448] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2017] [Accepted: 09/18/2018] [Indexed: 12/23/2022] Open
Abstract
Head size is important economic trait for many aquaculture fish which is directly linked to their carcass yield. The genetic basis of head size trait remains unclear in many widely cultured fish species. Common carp (Cyprinus carpio) is one of the most widely studied fish due to its importance on both economic and environmental aspects. In this study, we performed genome-wide association study using 433 Yellow River carp individuals from multiple families to identify loci and genes potentially associated with head size related traits including head length (HL), head length/body length ratio (HBR), eye diameter (ED), and eye cross (EC). QTL mapping was utilized to filter the effects of population stratification and improve power for the candidates identification in the largest surveyed family with a published genetic linkage map. Twelve SNPs showed significant for head size traits in GWAS and 18 QTLs were identified in QTL mapping. Our study combining both GWAS and QTL mapping could compensate the deficiency from each other and advance our understanding of head size traits in common carp. To acquire a better understanding of the correlation between head size and body growth, we also performed comparisons between QTLs of head size traits and growth-related traits. Candidate genes underlying head size traits were identified surrounding the significant SNPs, including parvalbumin, srpk2, fsrp5, igf1, igf3, grb10, igf1r, notch2, sfrp2. Many of these genes have been identified with potential functions on bone formation and growth. Igf1 was a putative gene associated with both head size and body growth in Yellow River carp. The teleost-specific igf3 was a candidate head size related gene, related to both HL and HBR. Our study also indicated the importance of Igf signaling pathway for both growth and head size determination in common carp, which could be potentially used in future selective breeding in common carp as well as other species.
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Affiliation(s)
- Lin Chen
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China.,College of Fisheries, Henan Normal University, Xinxiang, China
| | - Wenzhu Peng
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
| | - Shengnan Kong
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China.,College of Fisheries, Henan Normal University, Xinxiang, China
| | - Fei Pu
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
| | - Baohua Chen
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
| | - Zhixiong Zhou
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China
| | - Jianxin Feng
- Henan Academy of Fishery Sciences, Zhengzhou, China
| | - Xuejun Li
- College of Fisheries, Henan Normal University, Xinxiang, China
| | - Peng Xu
- State Key Laboratory of Marine Environmental Science, Xiamen University, Xiamen, China.,State Key Laboratory of Large Yellow Croaker Breeding, Ningde Fufa Fisheries Company Limited, Ningde, China.,Laboratory for Marine Biology and Biotechnology, Qingdao National Laboratory for Marine Science and Technology, Qingdao, China
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13
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Khan SY, Ali M, Kabir F, Renuse S, Na CH, Talbot CC, Hackett SF, Riazuddin SA. Proteome Profiling of Developing Murine Lens Through Mass Spectrometry. Invest Ophthalmol Vis Sci 2018; 59:100-107. [PMID: 29332127 PMCID: PMC5769801 DOI: 10.1167/iovs.17-21601] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/05/2022] Open
Abstract
Purpose We previously completed a comprehensive profile of the mouse lens transcriptome. Here, we investigate the proteome of the mouse lens through mass spectrometry–based protein sequencing at the same embryonic and postnatal time points. Methods We extracted mouse lenses at embryonic day 15 (E15) and 18 (E18) and postnatal day 0 (P0), 3 (P3), 6 (P6), and 9 (P9). The lenses from each time point were preserved in three distinct pools to serve as biological replicates for each developmental stage. The total cellular protein was extracted from the lens, digested with trypsin, and labeled with isobaric tandem mass tags (TMT) for three independent TMT experiments. Results A total of 5404 proteins were identified in the mouse ocular lens in at least one TMT set, 4244 in two, and 3155 were present in all three TMT sets. The majority of the proteins exhibited steady expression at all six developmental time points; nevertheless, we identified 39 proteins that exhibited an 8-fold differential (higher or lower) expression during the developmental time course compared to their respective levels at E15. The lens proteome is composed of diverse proteins that have distinct biological properties and functional characteristics, including proteins associated with cataractogenesis and autophagy. Conclusions We have established a comprehensive profile of the developing murine lens proteome. This repository will be helpful in identifying critical components of lens development and processes essential for the maintenance of its transparency.
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Affiliation(s)
- Shahid Y Khan
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Muhammad Ali
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Firoz Kabir
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Santosh Renuse
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Chan Hyun Na
- Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - C Conover Talbot
- Institute for Basic Biomedical Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - Sean F Hackett
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
| | - S Amer Riazuddin
- The Wilmer Eye Institute, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
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14
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Cvekl A, Zhang X. Signaling and Gene Regulatory Networks in Mammalian Lens Development. Trends Genet 2017; 33:677-702. [PMID: 28867048 DOI: 10.1016/j.tig.2017.08.001] [Citation(s) in RCA: 120] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2017] [Revised: 07/27/2017] [Accepted: 08/01/2017] [Indexed: 11/16/2022]
Abstract
Ocular lens development represents an advantageous system in which to study regulatory mechanisms governing cell fate decisions, extracellular signaling, cell and tissue organization, and the underlying gene regulatory networks. Spatiotemporally regulated domains of BMP, FGF, and other signaling molecules in late gastrula-early neurula stage embryos generate the border region between the neural plate and non-neural ectoderm from which multiple cell types, including lens progenitor cells, emerge and undergo initial tissue formation. Extracellular signaling and DNA-binding transcription factors govern lens and optic cup morphogenesis. Pax6, c-Maf, Hsf4, Prox1, Sox1, and a few additional factors regulate the expression of the lens structural proteins, the crystallins. Extensive crosstalk between a diverse array of signaling pathways controls the complexity and order of lens morphogenetic processes and lens transparency.
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Affiliation(s)
- Ales Cvekl
- Departments of Genetics and Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
| | - Xin Zhang
- Departments of Ophthalmology, Pathology and Cell Biology, Columbia University Medical Center, New York, NY 10032, USA.
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15
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Fujimura N. WNT/β-Catenin Signaling in Vertebrate Eye Development. Front Cell Dev Biol 2016; 4:138. [PMID: 27965955 PMCID: PMC5127792 DOI: 10.3389/fcell.2016.00138] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 11/09/2016] [Indexed: 01/04/2023] Open
Abstract
The vertebrate eye is a highly specialized sensory organ, which is derived from the anterior neural plate, head surface ectoderm, and neural crest-derived mesenchyme. The single central eye field, generated from the anterior neural plate, divides to give rise to the optic vesicle, which evaginates toward the head surface ectoderm. Subsequently, the surface ectoderm, in conjunction with the optic vesicle invaginates to form the lens vesicle and double-layered optic cup, respectively. This complex process is controlled by transcription factors and several intracellular and extracellular signaling pathways including WNT/β-catenin signaling. This signaling pathway plays an essential role in multiple developmental processes and has a profound effect on cell proliferation and cell fate determination. During eye development, the activity of WNT/β-catenin signaling is tightly controlled. Faulty regulation of WNT/β-catenin signaling results in multiple ocular malformations due to defects in the process of cell fate determination and differentiation. This mini-review summarizes recent findings on the role of WNT/β-catenin signaling in eye development. Whilst this mini-review focuses on loss-of-function and gain-of-function mutants of WNT/β-catenin signaling components, it also highlights some important aspects of β-catenin-independent WNT signaling in the eye development at later stages.
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Affiliation(s)
- Naoko Fujimura
- Laboratory of Eye Biology, BIOCEV Division, Institute of Molecular Genetics Prague, Czechia
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16
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Anand D, Lachke SA. Systems biology of lens development: A paradigm for disease gene discovery in the eye. Exp Eye Res 2016; 156:22-33. [PMID: 26992779 DOI: 10.1016/j.exer.2016.03.010] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2015] [Revised: 03/08/2016] [Accepted: 03/11/2016] [Indexed: 12/19/2022]
Abstract
Over the past several decades, the biology of the developing lens has been investigated using molecular genetics-based approaches in various vertebrate model systems. These efforts, involving target gene knockouts or knockdowns, have led to major advances in our understanding of lens morphogenesis and the pathological basis of cataracts, as well as of other lens related eye defects. In particular, we now have a functional understanding of regulators such as Pax6, Six3, Sox2, Oct1 (Pou2f1), Meis1, Pnox1, Zeb2 (Sip1), Mab21l1, Foxe3, Tfap2a (Ap2-alpha), Pitx3, Sox11, Prox1, Sox1, c-Maf, Mafg, Mafk, Hsf4, Fgfrs, Bmp7, and Tdrd7 in this tissue. However, whether these individual regulators interact or their targets overlap, and the significance of such interactions during lens morphogenesis, is not well defined. The arrival of high-throughput approaches for gene expression profiling (microarrays, RNA-sequencing (RNA-seq), etc.), which can be coupled with chromatin immunoprecipitation (ChIP) or RNA immunoprecipitation (RIP) assays, along with improved computational resources and publically available datasets (e.g. those containing comprehensive protein-protein, protein-DNA information), presents new opportunities to advance our understanding of the lens tissue on a global systems level. Such systems-level knowledge will lead to the derivation of the underlying lens gene regulatory network (GRN), defined as a circuit map of the regulator-target interactions functional in lens development, which can be applied to expedite cataract gene discovery. In this review, we cover the various systems-level approaches such as microarrays, RNA-seq, and ChIP that are already being applied to lens studies and discuss strategies for assembling and interpreting these vast amounts of high-throughput information for effective dispersion to the scientific community. In particular, we discuss strategies for effective interpretation of this new information in the context of the rich knowledge obtained through the application of traditional single-gene focused experiments on the lens. Finally, we discuss our vision for integrating these diverse high-throughput datasets in a single web-based user-friendly tool iSyTE (integrated Systems Tool for Eye gene discovery) - a resource that is already proving effective in the identification and characterization of genes linked to lens development and cataract. We anticipate that application of a similar approach to other ocular tissues such as the retina and the cornea, and even other organ systems, will significantly impact disease gene discovery.
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Affiliation(s)
- Deepti Anand
- Department of Biological Sciences, University of Delaware, Newark, DE, USA
| | - Salil A Lachke
- Department of Biological Sciences, University of Delaware, Newark, DE, USA; Center for Bioinformatics and Computational Biology, University of Delaware, Newark, DE, USA.
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17
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Mushirobira Y, Mizuta H, Luo W, Todo T, Hara A, Reading BJ, Sullivan CV, Hiramatsu N. Molecular cloning and partial characterization of a low‐density lipoprotein receptor‐related protein 13 (Lrp13) involved in vitellogenin uptake in the cutthroat trout (
Oncorhynchus clarki
). Mol Reprod Dev 2015; 82:986-1000. [DOI: 10.1002/mrd.22579] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2015] [Accepted: 08/30/2015] [Indexed: 01/01/2023]
Affiliation(s)
- Yuji Mushirobira
- Graduate School of Fisheries SciencesHokkaido UniversityHakodateJapan
| | - Hiroko Mizuta
- Graduate School of Fisheries SciencesHokkaido UniversityHakodateJapan
| | - Wenshu Luo
- Graduate School of Fisheries SciencesHokkaido UniversityHakodateJapan
| | - Takashi Todo
- Faculty of Fisheries SciencesHokkaido UniversityHakodateJapan
| | - Akihiko Hara
- Faculty of Fisheries SciencesHokkaido UniversityHakodateJapan
| | - Benjamin J. Reading
- Department of Applied EcologyNorth Carolina State UniversityRaleighNorth Carolina
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18
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Sugiyama Y, Shelley EJ, Badouel C, McNeill H, McAvoy JW. Atypical Cadherin Fat1 Is Required for Lens Epithelial Cell Polarity and Proliferation but Not for Fiber Differentiation. Invest Ophthalmol Vis Sci 2015; 56:4099-107. [PMID: 26114487 DOI: 10.1167/iovs.15-17008] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
PURPOSE The Fat family of atypical cadherins, originally identified in Drosophila, play diverse roles during embryogenesis and adult tissue maintenance. Among four mammalian members, Fat1 is essential for kidney and muscle organization, and is also essential for eye development; Fat1 knockout causes partial penetrant microphthalmia or anophthalmia. To account for the partial penetrance of the Fat1 phenotype, involvement of Fat4 in eye development was assessed. Lens phenotypes in Fat1 and 4 knockouts were also examined. METHODS Fat1 and Fat4 mRNA expression was examined by in situ hybridization. Knockout phenotypes of Fat1 and Fat4 were analyzed by hematoxylin and eosin (H&E) and immunofluorescent staining. RESULTS We found Fat4 knockout did not affect eye induction or enhance severity of Fat1 eye defects. Although Fat1 and Fat4 mRNAs are similarly expressed in the lens epithelial cells, only Fat1 knockout caused a fully penetrant lens epithelial cell defect, which was apparent at embryonic day 14.5 (E14.5). The columnar structure of the lens epithelial cells was disrupted and in some regions cell aggregates were formed. In these multilayered regions, apical cell junctions were fragmented and the apical-basal polarity was lost. EdU incorporation assay also showed enhanced proliferation in the lens epithelial cells. Interestingly, these defects were found mainly in the central zone of the epithelial layer. The lens epithelial cells of the germinative zone maintained their normal morphology and fiber differentiation occurred normally at the equator. CONCLUSIONS These observations indicate that Fat1 is essential for lens epithelial cell polarity and proliferation but not for terminal differentiation.
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Affiliation(s)
- Yuki Sugiyama
- Save Sight Institute University of Sydney, Sydney, New South Wales, Australia
| | - Elizabeth J Shelley
- Save Sight Institute University of Sydney, Sydney, New South Wales, Australia
| | - Caroline Badouel
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - Helen McNeill
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Toronto, Ontario, Canada
| | - John W McAvoy
- Save Sight Institute University of Sydney, Sydney, New South Wales, Australia
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