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Srivastava LK, Ehrlicher AJ. Sensing the squeeze: nuclear mechanotransduction in health and disease. Nucleus 2024; 15:2374854. [PMID: 38951951 PMCID: PMC11221475 DOI: 10.1080/19491034.2024.2374854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Accepted: 06/26/2024] [Indexed: 07/03/2024] Open
Abstract
The nucleus not only is a repository for DNA but also a center of cellular and nuclear mechanotransduction. From nuclear deformation to the interplay between mechanosensing components and genetic control, the nucleus is poised at the nexus of mechanical forces and cellular function. Understanding the stresses acting on the nucleus, its mechanical properties, and their effects on gene expression is therefore crucial to appreciate its mechanosensitive function. In this review, we examine many elements of nuclear mechanotransduction, and discuss the repercussions on the health of cells and states of illness. By describing the processes that underlie nuclear mechanosensation and analyzing its effects on gene regulation, the review endeavors to open new avenues for studying nuclear mechanics in physiology and diseases.
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Affiliation(s)
| | - Allen J. Ehrlicher
- Department of Bioengineering, McGill University, Montreal, Canada
- Department of Biomedical Engineering, McGill University, Montreal, Canada
- Department of Anatomy and Cell Biology, McGill University, Montreal, Canada
- Centre for Structural Biology, McGill University, Montreal, Canada
- Department of Mechanical Engineering, McGill University, Montreal, Canada
- Rosalind and Morris Goodman Cancer Institute, McGill University, Montreal, Canada
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2
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Girard M, de la Cruz MO, Marko JF, Erbaş A. Heterogeneous flexibility can contribute to chromatin segregation in the cell nucleus. Phys Rev E 2024; 110:014403. [PMID: 39160964 PMCID: PMC11371272 DOI: 10.1103/physreve.110.014403] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2023] [Accepted: 05/29/2024] [Indexed: 08/21/2024]
Abstract
The highly and slightly condensed forms of chromatin, heterochromatin and euchromatin, respectively, segregate in the cell nucleus. Heterochromatin is more abundant in the nucleus periphery. Here we study the mechanism of heterochromatin segregation by modeling interphase chromosomes as diblock ring copolymers confined in a rigid spherical shell using molecular dynamics simulations. In our model, heterochromatin and euchromatin are distinguished by their bending stiffnesses only, while an interaction potential between the spherical shell and chromatin is used to model lamin-associated proteins. Our simulations indicate that in the absence of attractive interactions between the nuclear shell and the chromatin, most heterochromatin segregates towards the nuclear interior due to the depletion of less flexible heterochromatin segments from the nuclear periphery. This inverted chromatin distribution,which is opposite to the conventional case with heterochromatin dominating at the periphery, is in accord with experimental observations in rod cells. This "inversion" is also found to be independent of the heterochromatin concentration and chromosome number. The chromatin distribution at the periphery found in vivo can be recovered by further increasing the bending stiffness of heterochromatin segments or by turning on attractive interactions between the nuclear shell and heterochromatin. Our results indicate that the bending stiffness of chromatin could be a contributor to chromosome organization along with differential effects of HP1α-driven phase segregation and of loop extruders and interactions with the nuclear envelope and topological constraints.
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Affiliation(s)
| | - Monica Olvera de la Cruz
- Department of Materials Science and Engineering, Department of Chemistry, Department of Chemical and Biological Engineering, and Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208, USA
| | | | - Aykut Erbaş
- UNAM-National Nanotechnology Research Center and Institute of Materials Science & Nanotechnology, Bilkent University, Ankara 06800, Turkey
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3
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Lightsey S, Sharma B. Natural Killer Cell Mechanosensing in Solid Tumors. Bioengineering (Basel) 2024; 11:328. [PMID: 38671750 PMCID: PMC11048000 DOI: 10.3390/bioengineering11040328] [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: 03/01/2024] [Revised: 03/21/2024] [Accepted: 03/25/2024] [Indexed: 04/28/2024] Open
Abstract
Natural killer (NK) cells, which are an exciting alternative cell source for cancer immunotherapies, must sense and respond to their physical environment to traffic to and eliminate cancer cells. Herein, we review the mechanisms by which NK cells receive mechanical signals and explore recent key findings regarding the impact of the physical characteristics of solid tumors on NK cell functions. Data suggest that different mechanical stresses present in solid tumors facilitate NK cell functions, especially infiltration and degranulation. Moreover, we review recent engineering advances that can be used to systemically study the role of mechanical forces on NK cell activity. Understanding the mechanisms by which NK cells interpret their environment presents potential targets to enhance NK cell immunotherapies for the treatment of solid tumors.
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Affiliation(s)
| | - Blanka Sharma
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL 23610, USA;
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4
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Campellone KG, Lebek NM, King VL. Branching out in different directions: Emerging cellular functions for the Arp2/3 complex and WASP-family actin nucleation factors. Eur J Cell Biol 2023; 102:151301. [PMID: 36907023 DOI: 10.1016/j.ejcb.2023.151301] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2022] [Revised: 02/07/2023] [Accepted: 02/25/2023] [Indexed: 03/06/2023] Open
Abstract
The actin cytoskeleton impacts practically every function of a eukaryotic cell. Historically, the best-characterized cytoskeletal activities are in cell morphogenesis, motility, and division. The structural and dynamic properties of the actin cytoskeleton are also crucial for establishing, maintaining, and changing the organization of membrane-bound organelles and other intracellular structures. Such activities are important in nearly all animal cells and tissues, although distinct anatomical regions and physiological systems rely on different regulatory factors. Recent work indicates that the Arp2/3 complex, a broadly expressed actin nucleator, drives actin assembly during several intracellular stress response pathways. These newly described Arp2/3-mediated cytoskeletal rearrangements are coordinated by members of the Wiskott-Aldrich Syndrome Protein (WASP) family of actin nucleation-promoting factors. Thus, the Arp2/3 complex and WASP-family proteins are emerging as crucial players in cytoplasmic and nuclear activities including autophagy, apoptosis, chromatin dynamics, and DNA repair. Characterizations of the functions of the actin assembly machinery in such stress response mechanisms are advancing our understanding of both normal and pathogenic processes, and hold great promise for providing insights into organismal development and interventions for disease.
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Affiliation(s)
- Kenneth G Campellone
- Department of Molecular and Cell Biology, Institute for Systems Genomics; University of Connecticut; Storrs, CT, USA.
| | - Nadine M Lebek
- Department of Molecular and Cell Biology, Institute for Systems Genomics; University of Connecticut; Storrs, CT, USA
| | - Virginia L King
- Department of Molecular and Cell Biology, Institute for Systems Genomics; University of Connecticut; Storrs, CT, USA
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5
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Wong DCP, Ding JL. The mechanobiology of NK cells- 'Forcing NK to Sense' target cells. Biochim Biophys Acta Rev Cancer 2023; 1878:188860. [PMID: 36791921 DOI: 10.1016/j.bbcan.2023.188860] [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: 11/23/2022] [Revised: 01/06/2023] [Accepted: 01/16/2023] [Indexed: 02/16/2023]
Abstract
Natural killer (NK) cells are innate immune lymphocytes that recognize and kill cancer and infected cells, which makes them unique 'off-the-shelf' candidates for a new generation of immunotherapies. Biomechanical forces in homeostasis and pathophysiology accrue additional immune regulation for NK immune responses. Indeed, cellular and tissue biomechanics impact NK receptor clustering, cytoskeleton remodeling, NK transmigration through endothelial cells, nuclear mechanics, and even NK-dendritic cell interaction, offering a plethora of unexplored yet important dynamic regulation for NK immunotherapy. Such events are made more complex by the heterogeneity of human NK cells. A significant question remains on whether and how biochemical and biomechanical cues collaborate for NK cell mechanotransduction, a process whereby mechanical force is sensed, transduced, and translated to downstream mechanical and biochemical signalling. Herein, we review recent advances in understanding how NK cells perceive and mechanotransduce biophysical cues. We focus on how the cellular cytoskeleton crosstalk regulates NK cell function while bearing in mind the heterogeneity of NK cells, the direct and indirect mechanical cues for NK anti-tumor activity, and finally, engineering advances that are of translational relevance to NK cell biology at the systems level.
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Affiliation(s)
- Darren Chen Pei Wong
- Department of Biological Sciences, National University of Singapore, 117543, Singapore.
| | - Jeak Ling Ding
- Department of Biological Sciences, National University of Singapore, 117543, Singapore; Integrative Sciences and Engineering Programme, National University of Singapore, 119077, Singapore.
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6
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Kalukula Y, Stephens AD, Lammerding J, Gabriele S. Mechanics and functional consequences of nuclear deformations. Nat Rev Mol Cell Biol 2022; 23:583-602. [PMID: 35513718 PMCID: PMC9902167 DOI: 10.1038/s41580-022-00480-z] [Citation(s) in RCA: 120] [Impact Index Per Article: 60.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/29/2022] [Indexed: 02/08/2023]
Abstract
As the home of cellular genetic information, the nucleus has a critical role in determining cell fate and function in response to various signals and stimuli. In addition to biochemical inputs, the nucleus is constantly exposed to intrinsic and extrinsic mechanical forces that trigger dynamic changes in nuclear structure and morphology. Emerging data suggest that the physical deformation of the nucleus modulates many cellular and nuclear functions. These functions have long been considered to be downstream of cytoplasmic signalling pathways and dictated by gene expression. In this Review, we discuss an emerging perspective on the mechanoregulation of the nucleus that considers the physical connections from chromatin to nuclear lamina and cytoskeletal filaments as a single mechanical unit. We describe key mechanisms of nuclear deformations in time and space and provide a critical review of the structural and functional adaptive responses of the nucleus to deformations. We then consider the contribution of nuclear deformations to the regulation of important cellular functions, including muscle contraction, cell migration and human disease pathogenesis. Collectively, these emerging insights shed new light on the dynamics of nuclear deformations and their roles in cellular mechanobiology.
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Affiliation(s)
- Yohalie Kalukula
- University of Mons, Soft Matter and Biomaterials group, Interfaces and Complex Fluids Laboratory, Research Institute for Biosciences, CIRMAP, Place du Parc, 20 B-7000 Mons, Belgium
| | - Andrew D. Stephens
- Biology Department, University of Massachusetts Amherst, Amherst, MA, USA
| | - Jan Lammerding
- Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA,Nancy E. and Peter C. Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853, USA
| | - Sylvain Gabriele
- University of Mons, Soft Matter and Biomaterials group, Interfaces and Complex Fluids Laboratory, Research Institute for Biosciences, CIRMAP, Place du Parc, 20 B-7000 Mons, Belgium
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7
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Seirin-Lee S, Yamamoto K, Kimura A. The extra-embryonic space and the local contour are crucial geometric constraints regulating cell arrangement. Development 2022; 149:275369. [PMID: 35552395 PMCID: PMC9148568 DOI: 10.1242/dev.200401] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Accepted: 03/23/2022] [Indexed: 12/29/2022]
Abstract
In multicellular systems, cells communicate with adjacent cells to determine their positions and fates, an arrangement important for cellular development. Orientation of cell division, cell-cell interactions (i.e. attraction and repulsion) and geometric constraints are three major factors that define cell arrangement. In particular, geometric constraints are difficult to reveal in experiments, and the contribution of the local contour of the boundary has remained elusive. In this study, we developed a multicellular morphology model based on the phase-field method so that precise geometric constraints can be incorporated. Our application of the model to nematode embryos predicted that the amount of extra-embryonic space, the empty space within the eggshell that is not occupied by embryonic cells, affects cell arrangement in a manner dependent on the local contour and other factors. The prediction was validated experimentally by increasing the extra-embryonic space in the Caenorhabditis elegans embryo. Overall, our analyses characterized the roles of geometrical contributors, specifically the amount of extra-embryonic space and the local contour, on cell arrangements. These factors should be considered for multicellular systems. Summary: The local contour and the extra-embryonic space, the empty space within the eggshell not occupied by embryonic cells, are important geometric constraints in cell arrangement of nematode embryos.
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Affiliation(s)
- Sungrim Seirin-Lee
- Institute for the Advanced Study of Human Biology (ASHBi), Kyoto University Institute for Advanced Study, Kyoto University, Kyoto 606-8315, Japan.,JST CREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
| | - Kazunori Yamamoto
- Department of Applied Bioscience, Faculty of Applied Bioscience, Kanagawa Institute of Technology, Atsugi 243-0292, Japan
| | - Akatsuki Kimura
- Cell Architecture Laboratory, Department of Chromosome Science, National Institute of Genetics, Mishima 411-8540, Japan.,Department of Genetics, The Graduate University for Advanced Studies, Sokendai, Mishima 411-8540, Japan
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8
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Bertho S, Clapp M, Banisch TU, Bandemer J, Raz E, Marlow FL. Zebrafish dazl regulates cystogenesis and germline stem cell specification during the primordial germ cell to germline stem cell transition. Development 2021; 148:dev187773. [PMID: 33722898 PMCID: PMC8077517 DOI: 10.1242/dev.187773] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 03/04/2021] [Indexed: 01/14/2023]
Abstract
Fertility and gamete reserves are maintained by asymmetric divisions of the germline stem cells to produce new stem cells or daughters that differentiate as gametes. Before entering meiosis, differentiating germ cells (GCs) of sexual animals typically undergo cystogenesis. This evolutionarily conserved process involves synchronous and incomplete mitotic divisions of a GC daughter (cystoblast) to generate sister cells connected by intercellular bridges that facilitate the exchange of materials to support rapid expansion of the gamete progenitor population. Here, we investigated cystogenesis in zebrafish and found that early GCs are connected by ring canals, and show that Deleted in azoospermia-like (Dazl), a conserved vertebrate RNA-binding protein (Rbp), is a regulator of this process. Analysis of dazl mutants revealed the essential role of Dazl in regulating incomplete cytokinesis, germline cyst formation and germline stem cell specification before the meiotic transition. Accordingly, dazl mutant GCs form defective ring canals, and ultimately remain as individual cells that fail to differentiate as meiocytes. In addition to promoting cystoblast divisions and meiotic entry, dazl is required for germline stem cell establishment and fertility.
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Affiliation(s)
- Sylvain Bertho
- Department of Cell, Developmental and Regenerative Medicine, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place Box 1020 New York, NY 10029-6574, USA
| | - Mara Clapp
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
| | - Torsten U. Banisch
- Institute of Cell Biology Center for Molecular Biology of Inflammation, Von-Esmarch-Str. 56, D-48149 Muenster, Germany
- New York University School of Medicine, Department of Cell Biology, New York, NY 10012, USA
| | - Jan Bandemer
- Institute of Cell Biology Center for Molecular Biology of Inflammation, Von-Esmarch-Str. 56, D-48149 Muenster, Germany
| | - Erez Raz
- Institute of Cell Biology Center for Molecular Biology of Inflammation, Von-Esmarch-Str. 56, D-48149 Muenster, Germany
| | - Florence L. Marlow
- Department of Cell, Developmental and Regenerative Medicine, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place Box 1020 New York, NY 10029-6574, USA
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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9
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dos Santos Á, Toseland CP. Regulation of Nuclear Mechanics and the Impact on DNA Damage. Int J Mol Sci 2021; 22:3178. [PMID: 33804722 PMCID: PMC8003950 DOI: 10.3390/ijms22063178] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 03/15/2021] [Accepted: 03/18/2021] [Indexed: 02/06/2023] Open
Abstract
In eukaryotic cells, the nucleus houses the genomic material of the cell. The physical properties of the nucleus and its ability to sense external mechanical cues are tightly linked to the regulation of cellular events, such as gene expression. Nuclear mechanics and morphology are altered in many diseases such as cancer and premature ageing syndromes. Therefore, it is important to understand how different components contribute to nuclear processes, organisation and mechanics, and how they are misregulated in disease. Although, over the years, studies have focused on the nuclear lamina-a mesh of intermediate filament proteins residing between the chromatin and the nuclear membrane-there is growing evidence that chromatin structure and factors that regulate chromatin organisation are essential contributors to the physical properties of the nucleus. Here, we review the main structural components that contribute to the mechanical properties of the nucleus, with particular emphasis on chromatin structure. We also provide an example of how nuclear stiffness can both impact and be affected by cellular processes such as DNA damage and repair.
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Affiliation(s)
- Ália dos Santos
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, UK
| | - Christopher P. Toseland
- Department of Oncology and Metabolism, University of Sheffield, Sheffield S10 2RX, UK
- Insigneo Institute for in Silico Medicine, University of Sheffield, Sheffield S10 2RX, UK
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10
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Ghanbarzadeh Nodehi S, Shivashankar GV, Prost J, Mohammad-Rafiee F. The characteristics of nuclear membrane fluctuations in stem cells. J R Soc Interface 2021; 18:20201010. [PMID: 33715401 DOI: 10.1098/rsif.2020.1010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
We analyse the stem cell nucleus shape fluctuation spectrum obtained from optical confocal microscopy on an hour time scale with 10 s resolution. In particular, we investigate the angular and time dependencies of these fluctuations, define appropriate correlation functions that reveal the fundamentally out of equilibrium nature of the observed fluctuations as well as their global anisotropy. Langevin equations respecting the symmetry of the system allow us to model the damped oscillatory behaviour of the time correlations.
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Affiliation(s)
| | - G V Shivashankar
- Department of Health Sciences and Technology (D-HEST), ETH Zurich, Switzerland.,Paul Scherrer Institute, Villigen, Switzerland
| | - Jacques Prost
- Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.,Laboratoire Physico Chimie Curie, Institut Curie, Paris Sciences Lettres Research University, CNRS UMR168, 75005 Paris, France
| | - Farshid Mohammad-Rafiee
- Department of Physics, Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran.,Research Center for Basic Sciences and Modern Technologies (RBST), Institute for Advanced Studies in Basic Sciences (IASBS), Zanjan 45137-66731, Iran
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11
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Seirin-Lee S. The Role of Cytoplasmic MEX-5/6 Polarity in Asymmetric Cell Division. Bull Math Biol 2021; 83:29. [PMID: 33594535 PMCID: PMC7886744 DOI: 10.1007/s11538-021-00860-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 01/14/2021] [Indexed: 11/29/2022]
Abstract
In the process of asymmetric cell division, the mother cell induces polarity in both the membrane and the cytosol by distributing substrates and components asymmetrically. Such polarity formation results from the harmonization of the upstream and downstream polarities between the cell membrane and the cytosol. MEX-5/6 is a well-investigated downstream cytoplasmic protein, which is deeply involved in the membrane polarity of the upstream transmembrane protein PAR in the Caenorhabditis elegans embryo. In contrast to the extensive exploration of membrane PAR polarity, cytoplasmic polarity is poorly understood, and the precise contribution of cytoplasmic polarity to the membrane PAR polarity remains largely unknown. In this study, we explored the interplay between the cytoplasmic MEX-5/6 polarity and the membrane PAR polarity by developing a mathematical model that integrates the dynamics of PAR and MEX-5/6 and reflects the cell geometry. Our investigations show that the downstream cytoplasmic protein MEX-5/6 plays an indispensable role in causing a robust upstream PAR polarity, and the integrated understanding of their interplay, including the effect of the cell geometry, is essential for the study of polarity formation in asymmetric cell division.
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Affiliation(s)
- Sungrim Seirin-Lee
- Department of Mathematics, Department of Mathematical and Life Sciences, Graduate School of Integrated Science for Life, Hiroshima University, Kagamiyama 1-3-1, Hiroshima, 700-0046, Japan.
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12
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Actin on and around the Nucleus. Trends Cell Biol 2020; 31:211-223. [PMID: 33376040 DOI: 10.1016/j.tcb.2020.11.009] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 11/15/2020] [Accepted: 11/19/2020] [Indexed: 12/14/2022]
Abstract
Actin plays roles in many important cellular processes, including cell motility, organelle movement, and cell signaling. The discovery of transmembrane actin-binding proteins at the outer nuclear membrane (ONM) raises the exciting possibility that actin can play a role in direct force transmission to the nucleus and the genome at its interior. Actin-dependent nucleus displacement was first described a decade ago. We are now gaining a more detailed understanding of its mechanisms, as well as new roles for actin during mitosis and meiosis, for gene expression, and in the cell's response to mechanical stimuli. Here we review these recent developments, the actin-binding proteins involved, the tissue specificity of these mechanisms, and methods developed to reconstitute and study this interaction in vitro.
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Ling YTT, Pease ME, Jefferys JL, Kimball EC, Quigley HA, Nguyen TD. Pressure-Induced Changes in Astrocyte GFAP, Actin, and Nuclear Morphology in Mouse Optic Nerve. Invest Ophthalmol Vis Sci 2020; 61:14. [PMID: 32910133 PMCID: PMC7488631 DOI: 10.1167/iovs.61.11.14] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2020] [Accepted: 08/12/2020] [Indexed: 12/17/2022] Open
Abstract
Purpose To conduct quantitative analysis of astrocytic glial fibrillary acidic protein (GFAP), actin and nuclei distribution in mouse optic nerve (ON) and investigate changes in the measured features after 3 days of ocular hypertension (OHT). Method Serial cross-sections of 3-day microbead-induced OHT and control ONs were fluorescently labelled and imaged using confocal microscope. Eighteen structural features were measured from the acquired images, including GFAP coverage, actin area fraction, process thickness, and aspect ratio of cell nucleus. The measured features were analyzed for variations with axial locations along ON and radial zones transverse to ON, as well as for the correlations with degree of intraocular pressure (IOP) change. Results The most significant changes in structural features after 3-day OHT occurred in the unmyelinated ON region (R1), and the changes were greater with greater IOP elevation. Although the GFAP, actin, axonal, and ON areas all increased in 3-day OHT ONs in R1 (P ≤ 0.004 for all), the area fraction of GFAP actually decreased (P = 0.02), the actin area fraction was stable and individual axon compartments were unchanged in size. Within R1, the number of nuclear clusters increased (P < 0.001), but the mean size of nuclear clusters was smaller (P = 0.02) and the clusters became rounder (P < 0.001). In all cross-sections of control ONs, astrocytic processes were thickest in the rim zone compared with the central and peripheral zones (P ≤ 0.002 for both), whereas the overall process width in R1 decreased after 3 days of OHT (P < 0.001). Conclusions The changes in structure elucidated IOP-generated alterations that underlie astrocyte mechanotranslational responses relevant to glaucoma.
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Affiliation(s)
- Yik Tung Tracy Ling
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, United States
| | - Mary E. Pease
- Wilmer Ophthalmological Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, United States
| | - Joan L. Jefferys
- Wilmer Ophthalmological Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, United States
| | - Elizabeth C. Kimball
- Wilmer Ophthalmological Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, United States
| | - Harry A. Quigley
- Wilmer Ophthalmological Institute, Johns Hopkins School of Medicine, Baltimore, Maryland, United States
| | - Thao D. Nguyen
- Department of Mechanical Engineering, The Johns Hopkins University, Baltimore, Maryland, United States
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