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Crellin HA, Buckley CE. Using Optogenetics to Investigate the Shared Mechanisms of Apical-Basal Polarity and Mitosis. Cells Tissues Organs 2023; 213:161-180. [PMID: 36599311 DOI: 10.1159/000528796] [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: 07/25/2022] [Accepted: 12/18/2022] [Indexed: 01/05/2023] Open
Abstract
The initiation of apical-basal (AB) polarity and the process of mitotic cell division are both characterised by the generation of specialised plasma membrane and cortical domains. These are generated using shared mechanisms, such as asymmetric protein accumulation, Rho GTPase signalling, cytoskeletal reorganisation, vesicle trafficking, and asymmetric phosphoinositide distribution. In epithelial tissue, the coordination of AB polarity and mitosis in space and time is important both during initial epithelial development and to maintain tissue integrity and ensure appropriate cell differentiation at later stages. Whilst significant progress has been made in understanding the mechanisms underlying cell division and AB polarity, it has so far been challenging to fully unpick the complex interrelationship between polarity, signalling, morphogenesis, and cell division. However, the recent emergence of optogenetic protein localisation techniques is now allowing researchers to reversibly control protein activation, localisation, and signalling with high spatiotemporal resolution. This has the potential to revolutionise our understanding of how subcellular processes such as AB polarity are integrated with cell behaviours such as mitosis and how these processes impact whole tissue morphogenesis. So far, these techniques have been used to investigate processes such as cleavage furrow ingression, mitotic spindle positioning, and in vivo epithelial morphogenesis. This review describes some of the key shared mechanisms of cell division and AB polarity establishment, how they are coordinated during development and how the advance of optogenetic techniques is furthering this research field.
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Affiliation(s)
- Helena A Crellin
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
| | - Clare E Buckley
- Department of Physiology, Development and Neuroscience, University of Cambridge, Cambridge, UK
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2
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Gupta VK, Nam S, Yim D, Camuglia J, Martin JL, Sanders EN, O'Brien LE, Martin AC, Kim T, Chaudhuri O. The nature of cell division forces in epithelial monolayers. J Cell Biol 2021; 220:212389. [PMID: 34132746 PMCID: PMC8240854 DOI: 10.1083/jcb.202011106] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 04/05/2021] [Accepted: 05/19/2021] [Indexed: 02/06/2023] Open
Abstract
Epithelial cells undergo striking morphological changes during division to ensure proper segregation of genetic and cytoplasmic materials. These morphological changes occur despite dividing cells being mechanically restricted by neighboring cells, indicating the need for extracellular force generation. Beyond driving cell division itself, forces associated with division have been implicated in tissue-scale processes, including development, tissue growth, migration, and epidermal stratification. While forces generated by mitotic rounding are well understood, forces generated after rounding remain unknown. Here, we identify two distinct stages of division force generation that follow rounding: (1) Protrusive forces along the division axis that drive division elongation, and (2) outward forces that facilitate postdivision spreading. Cytokinetic ring contraction of the dividing cell, but not activity of neighboring cells, generates extracellular forces that propel division elongation and contribute to chromosome segregation. Forces from division elongation are observed in epithelia across many model organisms. Thus, division elongation forces represent a universal mechanism that powers cell division in confining epithelia.
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Affiliation(s)
- Vivek K Gupta
- Department of Mechanical Engineering, Stanford University, Stanford, CA
| | - Sungmin Nam
- Department of Mechanical Engineering, Stanford University, Stanford, CA.,Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge, MA.,Wyss Institute for Biologically Inspired Engineering, Cambridge, MA
| | - Donghyun Yim
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN
| | - Jaclyn Camuglia
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA
| | - Judy Lisette Martin
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA
| | - Erin Nicole Sanders
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA
| | - Lucy Erin O'Brien
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA
| | - Adam C Martin
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA
| | - Taeyoon Kim
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN
| | - Ovijit Chaudhuri
- Department of Mechanical Engineering, Stanford University, Stanford, CA
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3
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Stooke-Vaughan GA, Davidson LA, Woolner S. Xenopus as a model for studies in mechanical stress and cell division. Genesis 2017; 55. [PMID: 28095623 DOI: 10.1002/dvg.23004] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2016] [Revised: 11/17/2016] [Accepted: 11/17/2016] [Indexed: 01/03/2023]
Abstract
We exist in a physical world, and cells within biological tissues must respond appropriately to both environmental forces and forces generated within the tissue to ensure normal development and homeostasis. Cell division is required for normal tissue growth and maintenance, but both the direction and rate of cell division must be tightly controlled to avoid diseases of over-proliferation such as cancer. Recent studies have shown that mechanical cues can cause mitotic entry and orient the mitotic spindle, suggesting that physical force could play a role in patterning tissue growth. However, to fully understand how mechanics guides cells in vivo, it is necessary to assess the interaction of mechanical strain and cell division in a whole tissue context. In this mini-review we first summarise the body of work linking mechanics and cell division, before looking at the advantages that the Xenopus embryo can offer as a model organism for understanding: (1) the mechanical environment during embryogenesis, and (2) factors important for cell division. Finally, we introduce a novel method for applying a reproducible strain to Xenopus embryonic tissue and assessing subsequent cell divisions.
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Affiliation(s)
- Georgina A Stooke-Vaughan
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, United Kingdom
| | - Lance A Davidson
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, Pennsylvania, 15213.,Department of Developmental Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, 15213.,Department of Computational and Systems Biology, University of Pittsburgh, Pittsburgh, Pennsylvania, 15213
| | - Sarah Woolner
- Wellcome Trust Centre for Cell-Matrix Research, Faculty of Biology, Medicine and Health, University of Manchester, Oxford Road, Manchester, M13 9PT, United Kingdom
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4
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Baumholtz AI, Simard A, Nikolopoulou E, Oosenbrug M, Collins MM, Piontek A, Krause G, Piontek J, Greene NDE, Ryan AK. Claudins are essential for cell shape changes and convergent extension movements during neural tube closure. Dev Biol 2017; 428:25-38. [PMID: 28545845 PMCID: PMC5523803 DOI: 10.1016/j.ydbio.2017.05.013] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 05/08/2017] [Accepted: 05/14/2017] [Indexed: 11/29/2022]
Abstract
During neural tube closure, regulated changes at the level of individual cells are translated into large-scale morphogenetic movements to facilitate conversion of the flat neural plate into a closed tube. Throughout this process, the integrity of the neural epithelium is maintained via cell interactions through intercellular junctions, including apical tight junctions. Members of the claudin family of tight junction proteins regulate paracellular permeability, apical-basal cell polarity and link the tight junction to the actin cytoskeleton. Here, we show that claudins are essential for neural tube closure: the simultaneous removal of Cldn3, −4 and −8 from tight junctions caused folate-resistant open neural tube defects. Their removal did not affect cell type differentiation, neural ectoderm patterning nor overall apical-basal polarity. However, apical accumulation of Vangl2, RhoA, and pMLC were reduced, and Par3 and Cdc42 were mislocalized at the apical cell surface. Our data showed that claudins act upstream of planar cell polarity and RhoA/ROCK signaling to regulate cell intercalation and actin-myosin contraction, which are required for convergent extension and apical constriction during neural tube closure, respectively. Simultaneous removal of Cldn3, −4 and −8 causes open neural tube defects. Folic acid cannot rescue open NTDs caused by depletion of Cldn3, −4 and −8. Removal of Cldn3, −4 and −8 prevents convergent extension. Apical constriction to form the median hinge point requires Cldn3, −4 and −8. Claudins localize polarity complex components to the apical surface.
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Affiliation(s)
- Amanda I Baumholtz
- Department of Human Genetics, McGill University, Canada; The Research Institute of the McGill University Health Centre, Montréal, Québec, Canada.
| | - Annie Simard
- Department of Experimental Medicine, McGill University, Canada; The Research Institute of the McGill University Health Centre, Montréal, Québec, Canada.
| | - Evanthia Nikolopoulou
- Developmental Biology and Cancer Programme, Birth Defects Research Centre, UCL Institute of Child Health, London, UK.
| | - Marcus Oosenbrug
- Department of Anatomy and Cell Biology, McGill University, Canada; The Research Institute of the McGill University Health Centre, Montréal, Québec, Canada.
| | - Michelle M Collins
- Department of Human Genetics, McGill University, Canada; The Research Institute of the McGill University Health Centre, Montréal, Québec, Canada.
| | - Anna Piontek
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP, Berlin, Germany.
| | - Gerd Krause
- Leibniz-Forschungsinstitut für Molekulare Pharmakologie, FMP, Berlin, Germany.
| | - Jörg Piontek
- Institute of Clinical Physiology, Charité-Universitätsmedizin Berlin, Berlin, Germany.
| | - Nicholas D E Greene
- Developmental Biology and Cancer Programme, Birth Defects Research Centre, UCL Institute of Child Health, London, UK.
| | - Aimee K Ryan
- Department of Human Genetics, McGill University, Canada; Department of Experimental Medicine, McGill University, Canada; Department of Pediatrics, McGill University, Canada; The Research Institute of the McGill University Health Centre, Montréal, Québec, Canada.
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5
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Zhong T, Zhou J. Orientation of the Mitotic Spindle in the Development of Tubular Organs. J Cell Biochem 2017; 118:1630-1633. [DOI: 10.1002/jcb.25865] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Accepted: 01/04/2017] [Indexed: 01/04/2023]
Affiliation(s)
- Tao Zhong
- Institute of Biomedical Sciences, College of Life Sciences, Key Laboratory of Animal Resistance Biology of Shandong Province; Shandong Normal University; Jinan Shandong 250014 China
| | - Jun Zhou
- Institute of Biomedical Sciences, College of Life Sciences, Key Laboratory of Animal Resistance Biology of Shandong Province; Shandong Normal University; Jinan Shandong 250014 China
- State Key Laboratory of Medicinal Chemical Biology, Key Laboratory of Bioactive Materials of the Ministry of Education, College of Life Sciences; Nankai University; Tianjin 300071 China
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6
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He L, Chen W, Wu PH, Jimenez A, Wong BS, San A, Konstantopoulos K, Wirtz D. Local 3D matrix confinement determines division axis through cell shape. Oncotarget 2016; 7:6994-7011. [PMID: 26515603 PMCID: PMC4872764 DOI: 10.18632/oncotarget.5848] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 10/03/2015] [Indexed: 12/24/2022] Open
Abstract
How the division axis is determined in mammalian cells embedded in three-dimensional (3D) matrices remains elusive, despite that many types of cells divide in 3D environments. Cells on two-dimensional (2D) substrates typically round up completely to divide. Here, we show that in 3D collagen matrices, mammalian cells such as HT1080 human fibrosarcoma and MDA-MB-231 breast cancer cells exhibit division modes distinct from their Counterparts on 2D substrates, with a markedly higher fraction of cells remaining highly elongated through mitosis in 3D matrices. The long axis of elongated mitotic cells accurately predicts the division axis, independently of matrix density and cell-matrix interactions. This 3D-specific elongated division mode is determined by the local confinement produced by the matrix and the ability of cells to protrude and locally remodel the matrix via β1 integrin. Elongated division is readily recapitulated using collagen-coated microfabricated channels. Cells depleted of β1 integrin still divide in the elongated mode in microchannels, suggesting that 3D confinement is sufficient to induce the elongated cell-division phenotype.
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Affiliation(s)
- Lijuan He
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA.,Johns Hopkins Physical Sciences - Oncology Center, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Weitong Chen
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Pei-Hsun Wu
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA.,Johns Hopkins Physical Sciences - Oncology Center, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Angela Jimenez
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA.,Johns Hopkins Physical Sciences - Oncology Center, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Bin Sheng Wong
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA.,Johns Hopkins Physical Sciences - Oncology Center, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Angela San
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Konstantinos Konstantopoulos
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA.,Johns Hopkins Physical Sciences - Oncology Center, The Johns Hopkins University, Baltimore, Maryland 21218, USA.,Departments of Oncology and Pathology and Sidney Kimmel Comprehensive Cancer Center, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | - Denis Wirtz
- Department of Chemical and Biomolecular Engineering, The Johns Hopkins University, Baltimore, Maryland 21218, USA.,Johns Hopkins Physical Sciences - Oncology Center, The Johns Hopkins University, Baltimore, Maryland 21218, USA.,Departments of Oncology and Pathology and Sidney Kimmel Comprehensive Cancer Center, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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7
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Lu R, Wilson JM. Rab14 specifies the apical membrane through Arf6-mediated regulation of lipid domains and Cdc42. Sci Rep 2016; 6:38249. [PMID: 27901125 PMCID: PMC5128791 DOI: 10.1038/srep38249] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Accepted: 11/07/2016] [Indexed: 12/13/2022] Open
Abstract
The generation of cell polarity is essential for the development of multi-cellular organisms as well as for the function of epithelial organs in the mature animal. Small GTPases regulate the establishment and maintenance of polarity through effects on cytoskeleton, membrane trafficking, and signaling. Using short-term 3-dimensional culture of MDCK cells, we find that the small GTPase Rab14 is required for apical membrane specification. Rab14 knockdown results in disruption of polarized lipid domains and failure of the Par/aPKC/Cdc42 polarity complex to localize to the apical membrane. These effects are mediated through tight control of lipid localization, as overexpression of the phosphatidylinositol 4-phosphate 5-kinase α [PtdIns(4)P5K] activator Arf6 or PtdIns(4)P5K alone, or treatment with the phosphatidylinositol 3-kinase (PtdInsI3K) inhibitor wortmannin, rescued the multiple-apical domain phenotype observed after Rab14 knockdown. Rab14 also co-immunoprecipitates and colocalizes with the small GTPase Cdc42, and Rab14 knockdown results in increased Cdc42 activity. Furthermore, Rab14 regulates trafficking of vesicles to the apical domain, mitotic spindle orientation, and midbody position, consistent with Rab14’s reported localization to the midbody as well as its effects upon Cdc42. These results position Rab14 at the top of a molecular cascade that regulates the establishment of cell polarity.
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Affiliation(s)
- Ruifeng Lu
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85724, USA
| | - Jean M Wilson
- Department of Cellular and Molecular Medicine, University of Arizona, Tucson, AZ 85724, USA
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8
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Walck-Shannon E, Lucas B, Chin-Sang I, Reiner D, Kumfer K, Cochran H, Bothfeld W, Hardin J. CDC-42 Orients Cell Migration during Epithelial Intercalation in the Caenorhabditis elegans Epidermis. PLoS Genet 2016; 12:e1006415. [PMID: 27861585 PMCID: PMC5127194 DOI: 10.1371/journal.pgen.1006415] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 10/10/2016] [Indexed: 12/22/2022] Open
Abstract
Cell intercalation is a highly directed cell rearrangement that is essential for animal morphogenesis. As such, intercalation requires orchestration of cell polarity across the plane of the tissue. CDC-42 is a Rho family GTPase with key functions in cell polarity, yet its role during epithelial intercalation has not been established because its roles early in embryogenesis have historically made it difficult to study. To circumvent these early requirements, in this paper we use tissue-specific and conditional loss-of-function approaches to identify a role for CDC-42 during intercalation of the Caenorhabditis elegans dorsal embryonic epidermis. CDC-42 activity is enriched in the medial tips of intercalating cells, which extend as cells migrate past one another. Moreover, CDC-42 is involved in both the efficient formation and orientation of cell tips during cell rearrangement. Using conditional loss-of-function we also show that the PAR complex functions in tip formation and orientation. Additionally, we find that the sole C. elegans Eph receptor, VAB-1, functions during this process in an Ephrin-independent manner. Using epistasis analysis, we find that vab-1 lies in the same genetic pathway as cdc-42 and is responsible for polarizing CDC-42 activity to the medial tip. Together, these data establish a previously uncharacterized role for polarized CDC-42, in conjunction with PAR-6, PAR-3 and an Eph receptor, during epithelial intercalation. As embryos develop, tissues must change shape to establish an animal’s form. One key form-shaping movement, cell intercalation, often occurs when a tissue elongates in a preferred direction. How cells in epithelial sheets can intercalate while maintaining tissue integrity is not well understood. Here we use the dorsal epidermis in embryos of the nematode worm, C. elegans, to study cell intercalation. As cells begin to intercalate, they form highly polarized tips that lead their migration. While some mechanisms that polarize intercalating cells have been established in other systems, our work identifies a new role for CDC-42—a highly conserved, highly regulated protein that controls the actin cytoskeleton. We previously established that a related protein, Rac, is involved in tip extension during dorsal intercalation. CDC-42 also contributes to this process in addition to helping orient the extending tip. CDC-42 appears to work in conjunction with two other known cell polarity proteins, PAR-3 and PAR-6, and the cell surface receptor, VAB-1. Our work identifies a novel pathway involving proteins conserved from worms to humans that regulates a ubiquitous process during animal development.
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Affiliation(s)
- Elise Walck-Shannon
- Department of Zoology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Bethany Lucas
- Program in Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Ian Chin-Sang
- Department of Biology, Queen's University, Kingston, Ontario, Canada
| | - David Reiner
- Center for Translational Cancer Research, Institute of Biosciences and Technology and Department of Medical Physiology, Texas A&M Health Science Center, Houston, Texas, United States of America
| | - Kraig Kumfer
- Department of Medicine, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Hunter Cochran
- Department of Zoology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - William Bothfeld
- Department of Zoology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
| | - Jeff Hardin
- Department of Zoology, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- Program in Genetics, University of Wisconsin-Madison, Madison, Wisconsin, United States of America
- * E-mail:
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9
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Fededa JP, Esk C, Mierzwa B, Stanyte R, Yuan S, Zheng H, Ebnet K, Yan W, Knoblich JA, Gerlich DW. MicroRNA-34/449 controls mitotic spindle orientation during mammalian cortex development. EMBO J 2016; 35:2386-2398. [PMID: 27707753 PMCID: PMC5109238 DOI: 10.15252/embj.201694056] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2016] [Revised: 08/18/2016] [Accepted: 09/06/2016] [Indexed: 01/07/2023] Open
Abstract
Correct orientation of the mitotic spindle determines the plane of cellular cleavage and is crucial for organ development. In the developing cerebral cortex, spindle orientation defects result in severe neurodevelopmental disorders, but the precise mechanisms that control this important event are not fully understood. Here, we use a combination of high-content screening and mouse genetics to identify the miR-34/449 family as key regulators of mitotic spindle orientation in the developing cerebral cortex. By screening through all cortically expressed miRNAs in HeLa cells, we show that several members of the miR-34/449 family control mitotic duration and spindle rotation. Analysis of miR-34/449 knockout (KO) mouse embryos demonstrates significant spindle misorientation phenotypes in cortical progenitors, resulting in an excess of radial glia cells at the expense of intermediate progenitors and a significant delay in neurogenesis. We identify the junction adhesion molecule-A (JAM-A) as a key target for miR-34/449 in the developing cortex that might be responsible for those defects. Our data indicate that miRNA-dependent regulation of mitotic spindle orientation is crucial for cell fate specification during mammalian neurogenesis.
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Affiliation(s)
- Juan Pablo Fededa
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA) Vienna Biocenter (VBC), Vienna, Austria
| | - Christopher Esk
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA) Vienna Biocenter (VBC), Vienna, Austria
| | - Beata Mierzwa
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA) Vienna Biocenter (VBC), Vienna, Austria
| | - Rugile Stanyte
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA) Vienna Biocenter (VBC), Vienna, Austria
| | - Shuiqiao Yuan
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Huili Zheng
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Klaus Ebnet
- Institute-associated Research Group "Cell Adhesion and Cell Polarity", Institute of Medical Biochemistry, ZMBE, Münster, Germany
| | - Wei Yan
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, NV, USA
| | - Juergen A Knoblich
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA) Vienna Biocenter (VBC), Vienna, Austria
| | - Daniel W Gerlich
- Institute of Molecular Biotechnology of the Austrian Academy of Sciences (IMBA) Vienna Biocenter (VBC), Vienna, Austria
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10
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Hanovice NJ, McMains E, Gross JM. A GAL4-inducible transgenic tool kit for the in vivo modulation of Rho GTPase activity in zebrafish. Dev Dyn 2016; 245:844-53. [PMID: 27105927 PMCID: PMC4946996 DOI: 10.1002/dvdy.24412] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 03/21/2016] [Accepted: 03/29/2016] [Indexed: 01/03/2023] Open
Abstract
BACKGROUND Rho GTPases are small monomeric G-proteins that play key roles in many cellular processes. Due to Rho GTPases' widespread expression and broad functions, analyses of their function during late development require tissue-specific modulation of activity. The GAL4/UAS system provides an excellent tool for investigating the function of Rho GTPases in vivo. With this in mind, we created a transgenic tool kit enabling spatial and temporal modulation of Rho GTPase activity in zebrafish. RESULTS Transgenic constructs were assembled driving dominant-negative, constitutively active, and wild-type versions of Cdc42, RhoA, and Rac1 under 10XUAS control. The self-cleaving viral peptide F2A was utilized to allow bicistronic expression of a fluorescent reporter and Rho GTPase. Global heat shock of hsp70l:gal4(+) transgenic embryos confirmed GAL4-specific construct expression. Western blot analysis indicated myc-tagged Rho GTPases were expressed only in the presence of GAL4. Construct expression was confined to proper cells when combined with pou4f3:gal4 or ptf1a:gal4. Finally, transgene expression resulted in reproducible defects in lens formation, indicating that the transgenes are functional in vivo. CONCLUSIONS We generated and validated 10 transgenic lines, creating a versatile tool kit for the temporal-spatial modulation of Cdc42, RhoA, and Rac1 activity in vivo. These lines will enable systematic analysis of Rho GTPase function in any tissue of interest. Developmental Dynamics 245:844-853, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Nicholas J Hanovice
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas
- Department of Ophthalmology, Louis J. Fox Center for Vision Restoration, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
| | - Emily McMains
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas
| | - Jeffrey M Gross
- Department of Molecular Biosciences, Institute for Cellular and Molecular Biology, The University of Texas at Austin, Austin, Texas
- Department of Ophthalmology, Louis J. Fox Center for Vision Restoration, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
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11
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Fujiwara M, Okamoto M, Hori M, Suga H, Jikihara H, Sugihara Y, Shimamoto F, Mori T, Nakaoji K, Hamada K, Ota T, Wiedemuth R, Temme A, Tatsuka M. Radiation-Induced RhoGDIβ Cleavage Leads to Perturbation of Cell Polarity: A Possible Link to Cancer Spreading. J Cell Physiol 2016; 231:2493-505. [DOI: 10.1002/jcp.25362] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2015] [Accepted: 02/23/2016] [Indexed: 01/17/2023]
Affiliation(s)
- Mamoru Fujiwara
- Faculty of Life and Environmental Sciences; Department of Life Sciences; Prefectural University of Hiroshima; Shoubara Hiroshima Japan
| | - Mayumi Okamoto
- Faculty of Life and Environmental Sciences; Department of Life Sciences; Prefectural University of Hiroshima; Shoubara Hiroshima Japan
| | - Masato Hori
- Faculty of Life and Environmental Sciences; Department of Life Sciences; Prefectural University of Hiroshima; Shoubara Hiroshima Japan
| | - Hiroshi Suga
- Faculty of Life and Environmental Sciences; Department of Life Sciences; Prefectural University of Hiroshima; Shoubara Hiroshima Japan
| | - Hiroshi Jikihara
- Department of Health Sciences; Faculty of Human Culture and Science; Prefectural University of Hiroshima; Minami-ku Hiroshima Japan
| | - Yuka Sugihara
- Department of Health Sciences; Faculty of Human Culture and Science; Prefectural University of Hiroshima; Minami-ku Hiroshima Japan
| | - Fumio Shimamoto
- Department of Health Sciences; Faculty of Human Culture and Science; Prefectural University of Hiroshima; Minami-ku Hiroshima Japan
| | - Toshio Mori
- Radioisotope Research Center; Nara Medical University School of Medicine; Kashihara Nara Japan
| | - Koichi Nakaoji
- Research & Development Division; Pias Corporation; Kobe Japan
| | - Kazuhiko Hamada
- Research & Development Division; Pias Corporation; Kobe Japan
| | - Takahide Ota
- Department of Life Science; Medical Research Institute; Kanazawa Medical University; Uchinada Ishikawa Japan
| | - Ralf Wiedemuth
- Department of Neurosurgery; University Hospital Carl Gustav Carus; Technical University Dresden; Dresden Germany
| | - Achim Temme
- Department of Neurosurgery; University Hospital Carl Gustav Carus; Technical University Dresden; Dresden Germany
| | - Masaaki Tatsuka
- Faculty of Life and Environmental Sciences; Department of Life Sciences; Prefectural University of Hiroshima; Shoubara Hiroshima Japan
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12
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Muccioli M, Qaisi D, Herman K, Plageman TF. Lens placode planar cell polarity is dependent on Cdc42-mediated junctional contraction inhibition. Dev Biol 2016; 412:32-43. [PMID: 26902112 DOI: 10.1016/j.ydbio.2016.02.016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 02/17/2016] [Accepted: 02/18/2016] [Indexed: 12/18/2022]
Abstract
Development of the ocular lens commences with the formation of the lens placode, an epithelial structure that thickens and subsequently bends inward in a process called invagination. Invagination is observed during the development of many embryonic structures, but the spectrum of morphogenetic events driving this process are, in most cases, not fully understood. A characteristic commonly found in embryonic tissues undergoing epithelial reorganization is planar polarity, a property where cells are geometrically and/or molecularly orientated in a specific direction along the plane of an epithelium. Planar polarity is known to drive the morphogenesis of several epithelial structures, however its role during invagination events is less clear. We have found that at the onset of invagination, cells of the lens placode become geometrically planar polarized such that they are orientated toward a central point in the lens placode. Further investigation revealed that this is due to contraction of radially orientated junctions and the elongation of those circumferentially orientated. Radial junctions have an elevated localization of actomyosin and their contraction is dependent on the F-actin and Rho-kinase binding protein, Shroom3. Elongation of circumferential junctions is dependent upon Cdc42, a Rho-GTPase known to regulate polarity via the Par-complex. We determined that Cdc42 and members of the Par-complex inhibit Shroom3-induced contractility and promote anisotropic placode cell geometry through inhibition of junctional contraction. We postulate that invagination of the lens placode requires careful orchestration of these opposing processes which are mediated by the planar polarization of junctional proteins.
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Affiliation(s)
- Maria Muccioli
- College of Optometry, The Ohio State University, Columbus, OH 43210, United States
| | - Dalya Qaisi
- College of Optometry, The Ohio State University, Columbus, OH 43210, United States
| | - Ken Herman
- College of Optometry, The Ohio State University, Columbus, OH 43210, United States
| | - Timothy F Plageman
- College of Optometry, The Ohio State University, Columbus, OH 43210, United States
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13
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Eom DS, Bain EJ, Patterson LB, Grout ME, Parichy DM. Long-distance communication by specialized cellular projections during pigment pattern development and evolution. eLife 2015; 4. [PMID: 26701906 PMCID: PMC4764569 DOI: 10.7554/elife.12401] [Citation(s) in RCA: 90] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2015] [Accepted: 12/23/2015] [Indexed: 02/06/2023] Open
Abstract
Changes in gene activity are essential for evolutionary diversification. Yet, elucidating the cellular behaviors that underlie modifications to adult form remains a profound challenge. We use neural crest-derived adult pigmentation of zebrafish and pearl danio to uncover cellular bases for alternative pattern states. We show that stripes in zebrafish require a novel class of thin, fast cellular projection to promote Delta-Notch signaling over long distances from cells of the xanthophore lineage to melanophores. Projections depended on microfilaments and microtubules, exhibited meandering trajectories, and stabilized on target cells to which they delivered membraneous vesicles. By contrast, the uniformly patterned pearl danio lacked such projections, concomitant with Colony stimulating factor 1-dependent changes in xanthophore differentiation that likely curtail signaling available to melanophores. Our study reveals a novel mechanism of cellular communication, roles for differentiation state heterogeneity in pigment cell interactions, and an unanticipated morphogenetic behavior contributing to a striking difference in adult form. DOI:http://dx.doi.org/10.7554/eLife.12401.001 Animals have very different patterns of skin pigmentation, and these patterns can be important for survival and reproduction. Zebrafish, for example, have horizontal dark and light stripes along their bodies, while a closely related fish called the pearl danio has an almost uniform pattern. The dark stripes of the zebrafish contain cells called melanophores, while the lighter regions contain two other types of cells known as xanthophores and iridophores. These pigment cell types interact with each other to create stripes. The iridophores establish the lighter stripes and specify the position and orientation of the dark stripes. They also produce a protein called Csf1, which allows the xanthophores to mature. As the stripes form, melanophores present in lighter stripes move into nearby dark stripes. Pearl danios also contain these three types of pigment cells, but these cells remain intermingled giving the fish their uniform color. Eom et al. have now used microscopy to image pigment cells in zebrafish and pearl danio to uncover how interactions between these cells differ in species with different pigment patterns. The technique involved tagging pigment cells with fluorescent markers and using time-lapse imaging to track them during the formation of the adult pigmentation pattern. The experiments show that stripes form in zebrafish because the cells that make the xanthophores form long, thin projections that extend to neighboring melanophores. These so-called ‘airinemes’ deliver materials to melanophores and help to clear the melanophores from interstripe regions, partly by activating a cell communication pathway called Delta-Notch signaling. These cell projections are mostly absent from the cells that make xanthophores in the pearl danio due to differences in when Csf1 is produced. This alters the timing of when the xanthophores develop, leading to the loss of long-distance airineme signaling. Eom et al.’s findings identify a new way in which cells can communicate and an unanticipated cell behavior that contributes to a striking difference in the pigmentation patterns of zebrafish and pearl danio. Future studies should further our understanding of these unique projections and reveal whether they are produced by other types of cells. DOI:http://dx.doi.org/10.7554/eLife.12401.002
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Affiliation(s)
- Dae Seok Eom
- Department of Biology, University of Washington, Seattle, United States
| | - Emily J Bain
- Department of Biology, University of Washington, Seattle, United States
| | | | - Megan E Grout
- Department of Biology, University of Washington, Seattle, United States
| | - David M Parichy
- Department of Biology, University of Washington, Seattle, United States.,Institute for Stem Cell and Regenerative Medicine, University of Washington, Seattle, United States
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14
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Tuncay H, Brinkmann BF, Steinbacher T, Schürmann A, Gerke V, Iden S, Ebnet K. JAM-A regulates cortical dynein localization through Cdc42 to control planar spindle orientation during mitosis. Nat Commun 2015; 6:8128. [PMID: 26306570 PMCID: PMC4560831 DOI: 10.1038/ncomms9128] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Accepted: 07/22/2015] [Indexed: 01/08/2023] Open
Abstract
Planar spindle orientation in polarized epithelial cells depends on the precise localization of the dynein–dynactin motor protein complex at the lateral cortex. The contribution of cell adhesion molecules to the cortical localization of the dynein–dynactin complex is poorly understood. Here we find that junctional adhesion molecule-A (JAM-A) regulates the planar orientation of the mitotic spindle during epithelial morphogenesis. During mitosis, JAM-A triggers a transient activation of Cdc42 and PI(3)K, generates a gradient of PtdIns(3,4,5)P3 at the cortex and regulates the formation of the cortical actin cytoskeleton. In the absence of functional JAM-A, dynactin localization at the cortex is reduced, the mitotic spindle apparatus is misaligned and epithelial morphogenesis in three-dimensional culture is compromised. Our findings indicate that a PI(3)K- and cortical F-actin-dependent pathway of planar spindle orientation operates in polarized epithelial cells to regulate epithelial morphogenesis, and we identify JAM-A as a junctional regulator of this pathway. Polarized epithelial cells orient their mitotic spindles in the plane of the sheet but the role of cell adhesion molecules in this process is poorly understood. Here Tuncay et al. show that JAM-A regulates spindle orientation by creating a gradient of PtdIns(3,4,5)P3, regulating cortical actin assembly and localizing dynactin to the cell cortex.
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Affiliation(s)
- Hüseyin Tuncay
- Institute-Associated Research Group 'Cell Adhesion and Cell Polarity', University of Münster, 48149 Münster, Germany.,Institute of Medical Biochemistry, ZMBE, University of Münster, 48149 Münster, Germany
| | - Benjamin F Brinkmann
- Institute-Associated Research Group 'Cell Adhesion and Cell Polarity', University of Münster, 48149 Münster, Germany.,Institute of Medical Biochemistry, ZMBE, University of Münster, 48149 Münster, Germany.,Interdisciplinary Clinical Research Center (IZKF), University of Münster, 48149 Münster, Germany
| | - Tim Steinbacher
- Institute-Associated Research Group 'Cell Adhesion and Cell Polarity', University of Münster, 48149 Münster, Germany.,Institute of Medical Biochemistry, ZMBE, University of Münster, 48149 Münster, Germany
| | - Annika Schürmann
- Institute-Associated Research Group 'Cell Adhesion and Cell Polarity', University of Münster, 48149 Münster, Germany.,Institute of Medical Biochemistry, ZMBE, University of Münster, 48149 Münster, Germany
| | - Volker Gerke
- Institute of Medical Biochemistry, ZMBE, University of Münster, 48149 Münster, Germany.,Cells-in-Motion Cluster of Excellence (EXC 1003-CiM), University of Münster, 48149 Münster, Germany
| | - Sandra Iden
- Institute-Associated Research Group 'Cell Adhesion and Cell Polarity', University of Münster, 48149 Münster, Germany.,Institute of Medical Biochemistry, ZMBE, University of Münster, 48149 Münster, Germany
| | - Klaus Ebnet
- Institute-Associated Research Group 'Cell Adhesion and Cell Polarity', University of Münster, 48149 Münster, Germany.,Institute of Medical Biochemistry, ZMBE, University of Münster, 48149 Münster, Germany.,Interdisciplinary Clinical Research Center (IZKF), University of Münster, 48149 Münster, Germany
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15
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Xia J, Swiercz JM, Bañón-Rodríguez I, Matković I, Federico G, Sun T, Franz T, Brakebusch CH, Kumanogoh A, Friedel RH, Martín-Belmonte F, Gröne HJ, Offermanns S, Worzfeld T. Semaphorin-Plexin Signaling Controls Mitotic Spindle Orientation during Epithelial Morphogenesis and Repair. Dev Cell 2015; 33:299-313. [PMID: 25892012 DOI: 10.1016/j.devcel.2015.02.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 12/17/2014] [Accepted: 02/02/2015] [Indexed: 01/02/2023]
Abstract
Morphogenesis, homeostasis, and regeneration of epithelial tissues rely on the accurate orientation of cell divisions, which is specified by the mitotic spindle axis. To remain in the epithelial plane, symmetrically dividing epithelial cells align their mitotic spindle axis with the plane. Here, we show that this alignment depends on epithelial cell-cell communication via semaphorin-plexin signaling. During kidney morphogenesis and repair, renal tubular epithelial cells lacking the transmembrane receptor Plexin-B2 or its semaphorin ligands fail to correctly orient the mitotic spindle, leading to severe defects in epithelial architecture and function. Analyses of a series of transgenic and knockout mice indicate that Plexin-B2 controls the cell division axis by signaling through its GTPase-activating protein (GAP) domain and Cdc42. Our data uncover semaphorin-plexin signaling as a central regulatory mechanism of mitotic spindle orientation necessary for the alignment of epithelial cell divisions with the epithelial plane.
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Affiliation(s)
- Jingjing Xia
- Department of Pharmacology, Max-Planck-Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | - Jakub M Swiercz
- Department of Pharmacology, Max-Planck-Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | | | - Ivana Matković
- Institute of Pharmacology, Biochemical-Pharmacological Center (BPC), University of Marburg, 35043 Marburg, Germany
| | - Giuseppina Federico
- Department of Cellular and Molecular Pathology, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Tianliang Sun
- Department of Pharmacology, Max-Planck-Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | - Timo Franz
- Department of Pharmacology, Max-Planck-Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany
| | - Cord H Brakebusch
- Biotech Research and Innovation Centre, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Atsushi Kumanogoh
- Department of Respiratory Medicine, Allergy and Rheumatic Diseases, Osaka University, Osaka 565-0871, Japan
| | - Roland H Friedel
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY 10029, USA
| | | | - Hermann-Josef Gröne
- Department of Cellular and Molecular Pathology, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
| | - Stefan Offermanns
- Department of Pharmacology, Max-Planck-Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany; Medical Faculty, University of Frankfurt, 60590 Frankfurt, Germany
| | - Thomas Worzfeld
- Department of Pharmacology, Max-Planck-Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany; Institute of Pharmacology, Biochemical-Pharmacological Center (BPC), University of Marburg, 35043 Marburg, Germany.
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16
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Eagleson G, Pfister K, Knowlton AL, Skoglund P, Keller R, Stukenberg PT. Kif2a depletion generates chromosome segregation and pole coalescence defects in animal caps and inhibits gastrulation of the Xenopus embryo. Mol Biol Cell 2015; 26:924-37. [PMID: 25568341 PMCID: PMC4342028 DOI: 10.1091/mbc.e13-12-0721] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Characterization of Kif2a in Xenopus embryos identifies new roles for the Kif2a microtubule depolymerase in coordinating cytokinesis and centrosome coalescence. In addition, defects in mitosis can inhibit large-scale developmental movements in vertebrate tissues. Kif2a is a member of the kinesin-13 microtubule depolymerases, which tightly regulate microtubule dynamics for many cellular processes. We characterized Kif2a depletion in Xenopus animal caps and embryos. Kif2a depletion generates defects in blastopore closure. These defects are rescued by removing the animal cap, suggesting that Kif2a-depleted animal caps are not compliant enough to allow gastrulation movements. Gastrulation defects are not rescued by a Kif2a mutated in an Aurora kinase phosphorylation site, suggesting that the phenotypes are caused by problems in mitosis. During animal cap mitoses, Kif2a localizes to the spindle poles and centromeres. Depletion of Kif2a generated multipolar spindles in stage 12 embryos. Kif2a-depleted animal caps have anaphase lagging chromosomes in stage 9 and 10 embryos and subsequent cytokinesis failure. Later divisions have greater than two centrosomes, generating extra spindle poles. Kif2a-depleted embryos are also defective at coalescing extra spindle poles into a bipolar spindle. The gastrulation and mitotic phenotypes can be rescued by either human Kif2a or Kif2b, which suggests that the two homologues redundantly regulate mitosis in mammals. These studies demonstrate that defects in mitosis can inhibit large-scale developmental movements in vertebrate tissues.
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Affiliation(s)
- Gerald Eagleson
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908
| | - Katherine Pfister
- Department of Biology, University of Virginia, Charlottesville, VA 22904
| | - Anne L Knowlton
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908
| | - Paul Skoglund
- Department of Biology, University of Virginia, Charlottesville, VA 22904
| | - Ray Keller
- Department of Biology, University of Virginia, Charlottesville, VA 22904
| | - P Todd Stukenberg
- Department of Biochemistry and Molecular Genetics, University of Virginia School of Medicine, Charlottesville, VA 22908
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17
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Nestor-Bergmann A, Goddard G, Woolner S. Force and the spindle: mechanical cues in mitotic spindle orientation. Semin Cell Dev Biol 2014; 34:133-9. [PMID: 25080021 PMCID: PMC4169662 DOI: 10.1016/j.semcdb.2014.07.008] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The mechanical environment of a cell has a profound effect on its behaviour, from dictating cell shape to driving the transcription of specific genes. Recent studies have demonstrated that mechanical forces play a key role in orienting the mitotic spindle, and therefore cell division, in both single cells and tissues. Whilst the molecular machinery that mediates the link between external force and the mitotic spindle remains largely unknown, it is becoming increasingly clear that this is a widely used mechanism which could prove vital for coordinating cell division orientation across tissues in a variety of contexts.
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Affiliation(s)
| | - Georgina Goddard
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom
| | - Sarah Woolner
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester M13 9PT, United Kingdom.
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18
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Huebner RJ, Lechler T, Ewald AJ. Developmental stratification of the mammary epithelium occurs through symmetry-breaking vertical divisions of apically positioned luminal cells. Development 2014; 141:1085-94. [PMID: 24550116 DOI: 10.1242/dev.103333] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Mammary ducts are elongated during development by stratified epithelial structures, known as terminal end buds (TEBs). TEBs exhibit reduced apicobasal polarity and extensive proliferation. A major unanswered question concerns the mechanism by which the simple ductal epithelium stratifies during TEB formation. We sought to elucidate this mechanism using real-time imaging of growth factor-induced stratification in 3D cultures of mouse primary epithelial organoids. We hypothesized that stratification could result from vertical divisions in either the apically positioned luminal epithelial cells or the basally positioned myoepithelial cells. Stratification initiated exclusively from vertical apical cell divisions, both in 3D culture and in vivo. During vertical apical divisions, only the mother cell retained tight junctions and segregated apical membranes. Vertical daughter cells initiated an unpolarized cell population located between the luminal and myoepithelial cells, similar to the unpolarized body cells in the TEB. As stratification and loss of apicobasal polarity are early hallmarks of cancer, we next determined the cellular mechanism of oncogenic stratification. Expression of activated ERBB2 induced neoplastic stratification through analogous vertical divisions of apically positioned luminal epithelial cells. However, ERBB2-induced stratification was accompanied by tissue overgrowth and acute loss of both tight junctions and apical polarity. Expression of phosphomimetic MEK (MEK1DD), a major ERBB2 effector, also induced stratification through vertical apical cell divisions. However, MEK1DD-expressing organoids exhibited normal levels of growth and retained apicobasal polarity. We conclude that both normal and neoplastic stratification are accomplished through receptor tyrosine kinase signaling dependent vertical cell divisions within the luminal epithelial cell layer.
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Affiliation(s)
- Robert J Huebner
- Departments of Cell Biology and Oncology, Center for Cell Dynamics, School of Medicine, Johns Hopkins University, 855 N. Wolfe Street, 452 Rangos Building, Baltimore, MD 21205, USA
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19
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Ramel MC, Hill CS. The ventral to dorsal BMP activity gradient in the early zebrafish embryo is determined by graded expression of BMP ligands. Dev Biol 2013; 378:170-82. [PMID: 23499658 PMCID: PMC3899928 DOI: 10.1016/j.ydbio.2013.03.003] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 02/26/2013] [Accepted: 03/04/2013] [Indexed: 12/26/2022]
Abstract
In the early zebrafish embryo, a ventral to dorsal gradient of bone morphogenetic protein (BMP) activity is established, which is essential for the specification of cell fates along this axis. To visualise and mechanistically determine how this BMP activity gradient forms, we have used a transgenic zebrafish line that expresses monomeric red fluorescent protein (mRFP) under the control of well-characterised BMP responsive elements. We demonstrate that mRFP expression in this line faithfully reports BMP and GDF signalling at both early and late stages of development. Taking advantage of the unstable nature of mRFP transcripts, we use in situ hybridisation to reveal the dynamic spatio-temporal pattern of BMP activity and establish the timing and sequence of events that lead to the formation of the BMP activity gradient. We show that the BMP transcriptional activity gradient is established between 30% and 40% epiboly stages and that it is preceded by graded mRNA expression of the BMP ligands. Both Dharma and FGF signalling contribute to graded bmp transcription during these early stages and it is subsequently maintained through autocrine BMP signalling. We show that BMP2B protein is also expressed in a gradient as early as blastula stages, but do not find any evidence of diffusion of this BMP to generate the BMP transcriptional activity gradient. Thus, in contrast to diffusion/transport-based models of BMP gradient formation in Drosophila, our results indicate that the establishment of the BMP activity gradient in early zebrafish embryos is determined by graded expression of the BMP ligands.
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Affiliation(s)
| | - Caroline S. Hill
- Laboratory of Developmental Signalling, Cancer Research UK London Research Institute, 44 Lincoln's Inn Fields, London, WC2A 3LY, United Kingdom
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20
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Massarwa R, Niswander L. In toto live imaging of mouse morphogenesis and new insights into neural tube closure. Development 2012; 140:226-36. [PMID: 23175632 DOI: 10.1242/dev.085001] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In the field of developmental biology, live imaging is a powerful tool for studying, in real time, the dynamic behaviors of tissues and cells during organ formation. Mammals, which develop in utero, have presented a challenge for live imaging. Here, we offer a novel, prolonged and robust live imaging system for visualizing the development of a variety of embryonic tissues in the midgestation mouse embryo. We demonstrate the advantages of this imaging system by following the dynamics of neural tube closure during mouse embryogenesis and reveal extensive movements of the cranial neural tissue that are independent of neural fold zipping.
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Affiliation(s)
- R'ada Massarwa
- Howard Hughes Medical Institute, Department of Pediatrics, University of Colorado Anschutz Medical Campus and Children's Hospital Colorado, Aurora, CO 80045, USA.
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21
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Wallingford JB. Planar cell polarity and the developmental control of cell behavior in vertebrate embryos. Annu Rev Cell Dev Biol 2012; 28:627-53. [PMID: 22905955 DOI: 10.1146/annurev-cellbio-092910-154208] [Citation(s) in RCA: 186] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Planar cell polarity (PCP), the orientation and alignment of cells within a sheet, is a ubiquitous cellular property that is commonly governed by the conserved set of proteins encoded by so-called PCP genes. The PCP proteins coordinate developmental signaling cues with individual cell behaviors in a wildly diverse array of tissues. Consequently, disruptions of PCP protein functions are linked to defects in axis elongation, inner ear patterning, neural tube closure, directed ciliary beating, and left/right patterning, to name only a few. This review attempts to synthesize what is known about PCP and the PCP proteins in vertebrate animals, with a particular focus on the mechanisms by which individual cells respond to PCP cues in order to execute specific cellular behaviors.
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Affiliation(s)
- John B Wallingford
- Howard Hughes Medical Institute, Section of Molecular, Cell and Developmental Biology, University of Texas, Austin, Texas 78712, USA.
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22
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Abstract
Cell polarization is an evolutionarily conserved process that facilitates asymmetric distribution of organelles and proteins and that is modified dynamically during physiological processes such as cell division, migration, and morphogenesis. The plasticity with which cells change their behavior and phenotype in response to cell intrinsic and extrinsic cues is an essential feature of normal physiology. In disease states such as cancer, cells lose their ability to behave normally in response to physiological cues. A molecular understanding of mechanisms that alter the behavior of cancer cells is limited. Cell polarity proteins are a recognized class of molecules that can receive and interpret both intrinsic and extrinsic signals to modulate cell behavior. In this review, we discuss how cell polarity proteins regulate a diverse array of biological processes and how they can contribute to alterations in the behavior of cancer cells.
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Affiliation(s)
- Senthil K Muthuswamy
- Ontario Cancer Institute, Campbell Family Institute for Breast Cancer Research, University of Toronto, Toronto M5G 2M9, Canada.
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23
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Spindle position in symmetric cell divisions during epiboly is controlled by opposing and dynamic apicobasal forces. Dev Cell 2012; 22:775-87. [PMID: 22406140 PMCID: PMC3332010 DOI: 10.1016/j.devcel.2012.01.002] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Revised: 11/08/2011] [Accepted: 01/11/2012] [Indexed: 11/21/2022]
Abstract
Orientation of cell division is a vital aspect of tissue morphogenesis and growth. Asymmetric divisions generate cell fate diversity and epithelial stratification, whereas symmetric divisions contribute to tissue growth, spreading, and elongation. Here, we describe a mechanism for positioning the spindle in symmetric cell divisions of an embryonic epithelium. We show that during the early stages of epiboly, spindles in the epithelium display dynamic behavior within the plane of the epithelium but are kept firmly within this plane to give a symmetric division. This dynamic stability relies on balancing counteracting forces: an apically directed force exerted by F-actin/myosin-2 via active cortical flow and a basally directed force mediated by microtubules and myosin-10. When both forces are disrupted, spindle orientation deviates from the epithelial plane, and epithelial surface is reduced. We propose that this dynamic mechanism maintains symmetric divisions while allowing the quick adjustment of division plane to facilitate even tissue spreading.
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24
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Sakamori R, Das S, Yu S, Feng S, Stypulkowski E, Guan Y, Douard V, Tang W, Ferraris RP, Harada A, Brakebusch C, Guo W, Gao N. Cdc42 and Rab8a are critical for intestinal stem cell division, survival, and differentiation in mice. J Clin Invest 2012; 122:1052-65. [PMID: 22354172 DOI: 10.1172/jci60282] [Citation(s) in RCA: 88] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2011] [Accepted: 01/10/2012] [Indexed: 01/01/2023] Open
Abstract
The constant self renewal and differentiation of adult intestinal stem cells maintains a functional intestinal mucosa for a lifetime. However, the molecular mechanisms that regulate intestinal stem cell division and epithelial homeostasis are largely undefined. We report here that the small GTPases Cdc42 and Rab8a are critical regulators of these processes in mice. Conditional ablation of Cdc42 in the mouse intestinal epithelium resulted in the formation of large intracellular vacuolar structures containing microvilli (microvillus inclusion bodies) in epithelial enterocytes, a phenotype reminiscent of human microvillus inclusion disease (MVID), a devastating congenital intestinal disorder that results in severe nutrient deprivation. Further analysis revealed that Cdc42-deficient stem cells had cell division defects, reduced capacity for clonal expansion and differentiation into Paneth cells, and increased apoptosis. Cdc42 deficiency impaired Rab8a activation and its association with multiple effectors, and prevented trafficking of Rab8a vesicles to the midbody. This impeded cytokinesis, triggering crypt apoptosis and disrupting epithelial morphogenesis. Rab8a was also required for Cdc42-GTP activity in the intestinal epithelium, where continued cell division takes place. Furthermore, mice haploinsufficient for both Cdc42 and Rab8a in the intestine demonstrated abnormal crypt morphogenesis and epithelial transporter physiology, further supporting their functional interaction. These data suggest that defects of the stem cell niche can cause MVID. This hypothesis represents a conceptual departure from the conventional view of this disease, which has focused on the affected enterocytes, and suggests stem cell-based approaches could be beneficial to infants with this often lethal condition.
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Affiliation(s)
- Ryotaro Sakamori
- Department of Biological Sciences, Rutgers University, Newark, New Jersey, USA
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25
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Poulson ND, Lechler T. Asymmetric cell divisions in the epidermis. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2012; 295:199-232. [PMID: 22449491 DOI: 10.1016/b978-0-12-394306-4.00012-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Generation of three-dimensional tissues with distinct cell types is required for the development of all organs. On its own, mitotic spindle orientation allows tissues to change in length or shape. In combination with intrinsic or extrinsic cues, this can also be coupled to the generation of diverse cell fates-a process known as asymmetric cell division (ACD). Understanding ACDs has been greatly aided by studies in invertebrate model systems, where genetics and live imaging have provided the basis for much of what we know. ACDs also drive the development and differentiation of the epidermis in mammals. While similar to the invertebrate models, the epidermis is distinct in balancing symmetric and asymmetric divisions to yield a tissue of the correct surface area and thickness. Here, we review the roles of spindle orientation in driving both morphogenesis and cell fate decisions. We highlight the epidermis as a unique model system to study not only basic mechanisms of ACD but also their regulation during development.
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Affiliation(s)
- Nicholas D Poulson
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina, USA
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26
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Castanon I, González-Gaitán M. Oriented cell division in vertebrate embryogenesis. Curr Opin Cell Biol 2011; 23:697-704. [PMID: 22000622 DOI: 10.1016/j.ceb.2011.09.009] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Revised: 09/16/2011] [Accepted: 09/23/2011] [Indexed: 10/16/2022]
Abstract
Tissue morphogenesis depends on the spatial arrangement of cells during development. A number of mechanisms have been described to contribute to the final shape of a tissue or organ, ranging from cell intercalation to the response of cells to chemotactic cues. One such mechanism is oriented cell division. Oriented cell division is determined by the position of the mitotic spindle. Indeed, there is increasing evidence implicating spindle misorientation in tissue and organ misshaping, which underlies disease conditions such as tumorigenesis or polycystic kidneys. Here we review recent studies addressing how the direction of tissue growth is determined by the orientation of cell division and how both extrinsic and intrinsic cues control the position of the mitotic spindle.
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Affiliation(s)
- Irinka Castanon
- Department of Biochemistry and Molecular Biology, Sciences II, 30 Quai Ernest-Ansermet, CH 1211 Geneva 4, Switzerland
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27
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Roles of planar cell polarity pathways in the development of neural [correction of neutral] tube defects. J Biomed Sci 2011; 18:66. [PMID: 21864354 PMCID: PMC3175158 DOI: 10.1186/1423-0127-18-66] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 08/24/2011] [Indexed: 02/08/2023] Open
Abstract
Neural tube defects (NTDs) are the second most common birth defect in humans. Despite many advances in the understanding of NTDs and the identification of many genes related to NTDs, the fundamental etiology for the majority of cases of NTDs remains unclear. Planar cell polarity (PCP) signaling pathway, which is important for polarized cell movement (such as cell migration) and organ morphogenesis through the activation of cytoskeletal pathways, has been shown to play multiple roles during neural tube closure. The disrupted function of PCP pathway is connected with some NTDs. Here, we summarize our current understanding of how PCP factors affect the pathogenesis of NTDs.
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Divide and polarize: recent advances in the molecular mechanism regulating epithelial tubulogenesis. Curr Opin Cell Biol 2011; 23:638-46. [PMID: 21807489 DOI: 10.1016/j.ceb.2011.07.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2011] [Revised: 06/28/2011] [Accepted: 07/07/2011] [Indexed: 11/22/2022]
Abstract
Epithelial organs are generated from groups of non-polarized cells by a combination of processes that induce the acquisition of cell polarity, lumen formation, and the subsequent steps required for tubulogenesis. The subcellular mechanisms associated to these processes are still poorly understood. The extracellular environment provides a cue for the initial polarization, while cytoskeletal rearrangements build up the three-dimensional architecture that supports the central lumen. The proper orientation of cell division in the epithelium has been found to be required for the normal formation of the central lumen in epithelial morphogenesis. Moreover, recent data in cellular models and in vivo have shed light into the underlying mechanisms that connect the spindle orientation machinery with cell polarity. In addition, recent work has clarified the core molecular components of the vesicle trafficking machinery in epithelial morphogenesis, including Rab-GTPases and the Exocyst, as well as an increasing list of microtubule-binding and actin-binding proteins and motors, most of which are conserved from yeast to humans. In this review we will focus on the discussion of novel findings that have unveiled important clues for the mechanisms that regulate epithelial tubulogenesis.
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29
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Tang N, Marshall WF, McMahon M, Metzger RJ, Martin GR. Control of mitotic spindle angle by the RAS-regulated ERK1/2 pathway determines lung tube shape. Science 2011; 333:342-345. [PMID: 21764747 DOI: 10.1126/science.1204831] [Citation(s) in RCA: 133] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
During early lung development, airway tubes change shape. Tube length increases more than circumference as a large proportion of lung epithelial cells divide parallel to the airway longitudinal axis. We show that this bias is lost in mutants with increased extracellular signal-regulated kinase 1 (ERK1) and ERK2 activity, revealing a link between the ERK1/2 signaling pathway and the control of mitotic spindle orientation. Using a mathematical model, we demonstrate that change in airway shape can occur as a function of spindle angle distribution determined by ERK1/2 signaling, independent of effects on cell proliferation or cell size and shape. We identify sprouty genes, which encode negative regulators of fibroblast growth factor 10 (FGF10)-mediated RAS-regulated ERK1/2 signaling, as essential for controlling airway shape change during development through an effect on mitotic spindle orientation.
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Affiliation(s)
- Nan Tang
- Department of Anatomy, University of California, San Francisco, CA 94158, USA
| | - Wallace F Marshall
- Department of Biochemistry and Biophysics, University of California, San Francisco, CA 94158, USA
| | - Martin McMahon
- Cancer Research Institute and Department of Cellular and Molecular Pharmacology, University of California, San Francisco, CA 94158, USA
| | - Ross J Metzger
- Department of Anatomy, University of California, San Francisco, CA 94158, USA
| | - Gail R Martin
- Department of Anatomy, University of California, San Francisco, CA 94158, USA
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30
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Halacheva V, Fuchs M, Dönitz J, Reupke T, Püschel B, Viebahn C. Planar cell movements and oriented cell division during early primitive streak formation in the mammalian embryo. Dev Dyn 2011; 240:1905-16. [DOI: 10.1002/dvdy.22687] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
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31
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Žigman M, Trinh LA, Fraser SE, Moens CB. Zebrafish neural tube morphogenesis requires Scribble-dependent oriented cell divisions. Curr Biol 2010; 21:79-86. [PMID: 21185191 DOI: 10.1016/j.cub.2010.12.005] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2010] [Revised: 10/18/2010] [Accepted: 12/02/2010] [Indexed: 11/17/2022]
Abstract
How control of subcellular events in single cells determines morphogenesis on the scale of the tissue is largely unresolved. The stereotyped cross-midline mitoses of progenitors in the zebrafish neural keel provide a unique experimental paradigm for defining the role and control of single-cell orientation for tissue-level morphogenesis in vivo. We show here that the coordinated orientation of individual progenitor cell division in the neural keel is the cellular determinant required for morphogenesis into a neural tube epithelium with a single straight lumen. We find that Scribble is required for oriented cell division and that its function in this process is independent of canonical apicobasal and planar polarity pathways. We identify a role for Scribble in controlling clustering of α-catenin foci in dividing progenitors. Loss of either Scrib or N-cadherin results in abnormally oriented mitoses, reduced cross-midline cell divisions, and similar neural tube defects. We propose that Scribble-dependent nascent cell-cell adhesion clusters between neuroepithelial progenitors contribute to define orientation of their cell division. Finally, our data demonstrate that while oriented mitoses of individual cells determine neural tube architecture, the tissue can in turn feed back on its constituent cells to define their polarization and cell division orientation to ensure robust tissue morphogenesis.
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Affiliation(s)
- Mihaela Žigman
- Howard Hughes Medical Institute and Division of Basic Science, Fred Hutchinson Cancer Research Center, B2-152, 1100 Fairview Avenue North, Seattle, WA 98109, USA.
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32
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Tabler JM, Yamanaka H, Green JBA. PAR-1 promotes primary neurogenesis and asymmetric cell divisions via control of spindle orientation. Development 2010; 137:2501-5. [DOI: 10.1242/dev.049833] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
In both invertebrate and vertebrate embryonic central nervous systems, deep cells differentiate while superficial (ventricular) epithelial cells remain in a proliferative, stem cell state. The conserved polarity protein PAR-1, which is basolaterally localised in epithelia, promotes and is required for differentiating deep layer cell types, including ciliated cells and neurons. It has recently been shown that atypical protein kinase C (aPKC), which is apically enriched, inhibits neurogenesis and acts as a nuclear determinant, raising the question of how PAR-1 antagonises aPKC activity to promote neurogenesis. Here we show that PAR-1 stimulates the generation of deep cell progeny from the superficial epithelium of the neural plate and that these deep cells have a corresponding (i.e. deep cell) neuronal phenotype. We further show that gain- and loss-of-function of PAR-1 increase and decrease, respectively, the proportion of epithelial mitotic spindles with a vertical orientation, thereby respectively increasing and decreasing the number of cleavages that generate deep daughter cells. PAR-1 is therefore a crucial regulator of the balance between symmetric (two superficial daughters) and asymmetric (one superficial and one deep daughter) cell divisions. Vertebrate PAR-1 thus antagonises the anti-neurogenic influence of apical aPKC by physically partitioning cells away from it in vivo.
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Affiliation(s)
- Jacqueline M. Tabler
- King's College London, Department of Craniofacial Development, Floor 27, Guy's Tower, London SE1 9RT, UK
| | - Hiroaki Yamanaka
- King's College London, Department of Craniofacial Development, Floor 27, Guy's Tower, London SE1 9RT, UK
| | - Jeremy B. A. Green
- King's College London, Department of Craniofacial Development, Floor 27, Guy's Tower, London SE1 9RT, UK
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Kieserman EK, Lee C, Gray RS, Park TJ, Wallingford JB. High-magnification in vivo imaging of Xenopus embryos for cell and developmental biology. Cold Spring Harb Protoc 2010; 2010:pdb.prot5427. [PMID: 20439414 DOI: 10.1101/pdb.prot5427] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Embryos of the frog Xenopus laevis are an ideal model system for in vivo imaging of dynamic biological processes, from the inner workings of individual cells to the reshaping of tissues during embryogenesis. Their externally developing embryos are more amenable to in vivo analysis than internally developing mammalian embryos, and the large size of the embryos make them particularly suitable for time-lapse analysis of tissue-level morphogenetic events. In addition, individual cells in Xenopus embryos are larger than those in other vertebrate models, making them ideal for imaging cell behavior and subcellular processes (e.g., following the dynamics of fluorescent fusion proteins in living or fixed cells and tissues). Xenopus embryos are amenable to simple manipulations of gene function, including knockdown and misexpression, and the large number of embryos available allows even an inexperienced researcher to perform hundreds of such manipulations per day. Transgenesis is quite effective as well. Finally, because the fate map of Xenopus embryos is stereotypical, simple targeted microinjections can reliably deliver reagents into specific tissues and cell types for gene manipulation or for imaging. Although yolk opacity can hinder deep imaging in intact embryos, almost any cell in the early embryo can be placed into organotypic culture, such that the cells of interest are directly apposed to the cover glass. Furthermore, live imaging techniques can be complemented with immunostaining and in situ hybridization approaches in fixed tissues. This protocol describes methods for labeling and high-magnification time-lapse imaging of cell biological and developmental processes in Xenopus embryos by confocal microscopy.
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Affiliation(s)
- Esther K Kieserman
- Howard Hughes Medical Institute and Section of Molecular Cell and Developmental Biology, University of Texas, Austin, TX 78712, USA
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Pyrgaki C, Trainor P, Hadjantonakis AK, Niswander L. Dynamic imaging of mammalian neural tube closure. Dev Biol 2010; 344:941-7. [PMID: 20558153 DOI: 10.1016/j.ydbio.2010.06.010] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Revised: 06/07/2010] [Accepted: 06/07/2010] [Indexed: 10/19/2022]
Abstract
Neurulation, the process of neural tube formation, is a complex morphogenetic event. In the mammalian embryo, an understanding of the dynamic nature of neurulation has been hampered due to its in utero development. Here we use laser point scanning confocal microscopy of a membrane expressed fluorescent protein to visualize the dynamic cell behaviors comprising neural tube closure in the cultured mouse embryo. In particular, we have focused on the final step wherein the neural folds approach one another and seal to form the closed neural tube. Our unexpected findings reveal a mechanism of closure in the midbrain different from the zipper-like process thought to occur more generally. Individual non-neural ectoderm cells on opposing sides of the neural folds undergo a dramatic change in shape to protrude from the epithelial layer and then form intermediate closure points to "button-up" the folds. Cells from the juxtaposed neural folds extend long and short flexible extensions and form bridges across the physical gap of the closing folds. Thus, the combination of live embryo culture with dynamic imaging provides intriguing insight into the cell biological processes that mold embryonic tissues in mammals.
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Affiliation(s)
- Christina Pyrgaki
- HHMI, Department of Pediatrics, Molecular Biology Graduate Program, University of Colorado Denver, Aurora, CO 80045, USA
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