1
|
Arjona MI, Najafi J, Minc N. Cytoplasm mechanics and cellular organization. Curr Opin Cell Biol 2023; 85:102278. [PMID: 37979412 DOI: 10.1016/j.ceb.2023.102278] [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: 07/13/2023] [Revised: 10/17/2023] [Accepted: 10/18/2023] [Indexed: 11/20/2023]
Abstract
As cells organize spatially or divide, they translocate many micron-scale organelles in their cytoplasm. These include endomembrane vesicles, nuclei, microtubule asters, mitotic spindles, or chromosomes. Organelle motion is powered by cytoskeleton forces but is opposed by viscoelastic forces imparted by the surrounding crowded cytoplasm medium. These resistive forces associated to cytoplasm physcial properties remain generally underappreciated, yet reach significant values to slow down organelle motion or even limit their displacement by springing them back towards their original position. The cytoplasm may also be itself organized in time and space, being for example stiffer or more fluid at certain locations or during particular cell cycle phases. Thus, cytoplasm mechanics may be viewed as a labile module that contributes to organize cells. We here review emerging methods, mechanisms, and concepts to study cytoplasm mechanical properties and their function in organelle positioning, cellular organization and division.
Collapse
Affiliation(s)
- María Isabel Arjona
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France; Equipe Labellisée LIGUE Contre le Cancer, France
| | - Javad Najafi
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France; Equipe Labellisée LIGUE Contre le Cancer, France
| | - Nicolas Minc
- Université de Paris, CNRS, Institut Jacques Monod, F-75006 Paris, France; Equipe Labellisée LIGUE Contre le Cancer, France.
| |
Collapse
|
2
|
Chen X, Roeters SJ, Cavanna F, Alvarado J, Baiz CR. Crowding alters F-actin secondary structure and hydration. Commun Biol 2023; 6:900. [PMID: 37660224 PMCID: PMC10475093 DOI: 10.1038/s42003-023-05274-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2023] [Accepted: 08/22/2023] [Indexed: 09/04/2023] Open
Abstract
Actin, an important component of eukaryotic cell cytoskeleton, regulates cell shape and transport. The morphology and biochemical properties of actin filaments are determined by their structure and protein-protein contacts. Crowded environments can organize filaments into bundles, but less is known about how they affect F-actin structure. This study used 2D IR spectroscopy and spectral calculations to examine how crowding and bundling impact the secondary structure and local environments in filaments and weakly or strongly bundled networks. The results reveal that bundling induces changes in actin's secondary structure, leading to a decrease in β-sheet and an increase in loop conformations. Strongly bundled networks exhibit a decrease in backbone solvent exposure, with less perturbed α-helices and nearly "locked" β-sheets. Similarly, the loops become less hydrated but maintain a dynamic environment. These findings highlight the role of loop structure in actin network morphology and stability under morphology control by PEG.
Collapse
Affiliation(s)
- Xiaobing Chen
- Department of Chemistry, University of Texas at Austin, Austin, TX, USA
| | - Steven J Roeters
- Department of Chemistry, Aarhus University, Aarhus, Denmark
- Department of Anatomy and Neurosciences, Vrije Universiteit, Amsterdam UMC, Amsterdam, Netherlands
| | - Francis Cavanna
- Department of Physics, University of Texas at Austin, Center for Nonlinear Dynamics, Austin, TX, USA
| | - José Alvarado
- Department of Physics, University of Texas at Austin, Center for Nonlinear Dynamics, Austin, TX, USA
| | - Carlos R Baiz
- Department of Chemistry, University of Texas at Austin, Austin, TX, USA.
| |
Collapse
|
3
|
Su É, Villard C, Manneville JB. Mitochondria: At the crossroads between mechanobiology and cell metabolism. Biol Cell 2023; 115:e2300010. [PMID: 37326132 DOI: 10.1111/boc.202300010] [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: 01/17/2023] [Revised: 06/11/2023] [Accepted: 06/13/2023] [Indexed: 06/17/2023]
Abstract
Metabolism and mechanics are two key facets of structural and functional processes in cells, such as growth, proliferation, homeostasis and regeneration. Their reciprocal regulation has been increasingly acknowledged in recent years: external physical and mechanical cues entail metabolic changes, which in return regulate cell mechanosensing and mechanotransduction. Since mitochondria are pivotal regulators of metabolism, we review here the reciprocal links between mitochondrial morphodynamics, mechanics and metabolism. Mitochondria are highly dynamic organelles which sense and integrate mechanical, physical and metabolic cues to adapt their morphology, the organization of their network and their metabolic functions. While some of the links between mitochondrial morphodynamics, mechanics and metabolism are already well established, others are still poorly documented and open new fields of research. First, cell metabolism is known to correlate with mitochondrial morphodynamics. For instance, mitochondrial fission, fusion and cristae remodeling allow the cell to fine-tune its energy production through the contribution of mitochondrial oxidative phosphorylation and cytosolic glycolysis. Second, mechanical cues and alterations in mitochondrial mechanical properties reshape and reorganize the mitochondrial network. Mitochondrial membrane tension emerges as a decisive physical property which regulates mitochondrial morphodynamics. However, the converse link hypothesizing a contribution of morphodynamics to mitochondria mechanics and/or mechanosensitivity has not yet been demonstrated. Third, we highlight that mitochondrial mechanics and metabolism are reciprocally regulated, although little is known about the mechanical adaptation of mitochondria in response to metabolic cues. Deciphering the links between mitochondrial morphodynamics, mechanics and metabolism still presents significant technical and conceptual challenges but is crucial both for a better understanding of mechanobiology and for potential novel therapeutic approaches in diseases such as cancer.
Collapse
Affiliation(s)
- Émilie Su
- Laboratoire Matière et Systèmes Complexes (MSC), Université Paris Cité - CNRS, UMR 7057, Paris, France
- Laboratoire Interdisciplinaire des Énergies de Demain (LIED), Université Paris Cité - CNRS, UMR 8236, Paris, France
| | - Catherine Villard
- Laboratoire Interdisciplinaire des Énergies de Demain (LIED), Université Paris Cité - CNRS, UMR 8236, Paris, France
| | - Jean-Baptiste Manneville
- Laboratoire Matière et Systèmes Complexes (MSC), Université Paris Cité - CNRS, UMR 7057, Paris, France
| |
Collapse
|
4
|
Shamipour S, Hofmann L, Steccari I, Kardos R, Heisenberg CP. Yolk granule fusion and microtubule aster formation regulate cortical granule translocation and exocytosis in zebrafish oocytes. PLoS Biol 2023; 21:e3002146. [PMID: 37289834 DOI: 10.1371/journal.pbio.3002146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2023] [Accepted: 05/03/2023] [Indexed: 06/10/2023] Open
Abstract
Dynamic reorganization of the cytoplasm is key to many core cellular processes, such as cell division, cell migration, and cell polarization. Cytoskeletal rearrangements are thought to constitute the main drivers of cytoplasmic flows and reorganization. In contrast, remarkably little is known about how dynamic changes in size and shape of cell organelles affect cytoplasmic organization. Here, we show that within the maturing zebrafish oocyte, the surface localization of exocytosis-competent cortical granules (Cgs) upon germinal vesicle breakdown (GVBD) is achieved by the combined activities of yolk granule (Yg) fusion and microtubule aster formation and translocation. We find that Cgs are moved towards the oocyte surface through radially outward cytoplasmic flows induced by Ygs fusing and compacting towards the oocyte center in response to GVBD. We further show that vesicles decorated with the small Rab GTPase Rab11, a master regulator of vesicular trafficking and exocytosis, accumulate together with Cgs at the oocyte surface. This accumulation is achieved by Rab11-positive vesicles being transported by acentrosomal microtubule asters, the formation of which is induced by the release of CyclinB/Cdk1 upon GVBD, and which display a net movement towards the oocyte surface by preferentially binding to the oocyte actin cortex. We finally demonstrate that the decoration of Cgs by Rab11 at the oocyte surface is needed for Cg exocytosis and subsequent chorion elevation, a process central in egg activation. Collectively, these findings unravel a yet unrecognized role of organelle fusion, functioning together with cytoskeletal rearrangements, in orchestrating cytoplasmic organization during oocyte maturation.
Collapse
Affiliation(s)
- Shayan Shamipour
- Institute of Science and Technology Austria, Klosterneuburg, Austria
- Department of Molecular Life Sciences, University of Zurich, Zurich, Switzerland
| | - Laura Hofmann
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Irene Steccari
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | - Roland Kardos
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | | |
Collapse
|
5
|
Najafi J, Dmitrieff S, Minc N. Size- and position-dependent cytoplasm viscoelasticity through hydrodynamic interactions with the cell surface. Proc Natl Acad Sci U S A 2023; 120:e2216839120. [PMID: 36802422 PMCID: PMC9992773 DOI: 10.1073/pnas.2216839120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Accepted: 01/23/2023] [Indexed: 02/23/2023] Open
Abstract
Many studies of cytoplasm rheology have focused on small components in the submicrometer scale. However, the cytoplasm also baths large organelles like nuclei, microtubule asters, or spindles that often take significant portions of cells and move across the cytoplasm to regulate cell division or polarization. Here, we translated passive components of sizes ranging from few up to ~50 percents of the cell diameter, through the vast cytoplasm of live sea urchin eggs, with calibrated magnetic forces. Creep and relaxation responses indicate that for objects larger than the micron size, the cytoplasm behaves as a Jeffreys material, viscoelastic at short timescales, and fluidizing at longer times. However, as component size approached that of cells, cytoplasm viscoelastic resistance increased in a nonmonotonic manner. Flow analysis and simulations suggest that this size-dependent viscoelasticity emerges from hydrodynamic interactions between the moving object and the static cell surface. This effect also yields to position-dependent viscoelasticity with objects initially closer to the cell surface being harder to displace. These findings suggest that the cytoplasm hydrodynamically couples large organelles to the cell surface to restrain their motion, with important implications for cell shape sensing and cellular organization.
Collapse
Affiliation(s)
- Javad Najafi
- Université de Paris, CNRS, Institut Jacques Monod,75006Paris, France
- Equipe Labellisée Ligue Contre le Cancer, 75013Paris, France
| | - Serge Dmitrieff
- Université de Paris, CNRS, Institut Jacques Monod,75006Paris, France
- Equipe Labellisée Ligue Contre le Cancer, 75013Paris, France
| | - Nicolas Minc
- Université de Paris, CNRS, Institut Jacques Monod,75006Paris, France
- Equipe Labellisée Ligue Contre le Cancer, 75013Paris, France
| |
Collapse
|
6
|
Manipulation of New Fluorescent Magnetic Nanoparticles with an Electromagnetic Needle, Allowed Determining the Viscosity of the Cytoplasm of M-HeLa Cells. Pharmaceuticals (Basel) 2023. [DOI: 10.3390/ph16020200] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Magnetic nanoparticles (MNPs) have recently begun to be actively used in biomedicine applications, for example, for targeted drug delivery, in tissue engineering, and in magnetic resonance imaging. The study of the magnetic field effect on MNPs internalized into living cells is of particular importance since it allows a non-invasive influence on cellular activity. There is data stating the possibility to manipulate and control individual MNPs utilizing the local magnetic field gradient created by electromagnetic needles (EN). The present work aimed to demonstrate the methodological and technical approach for manipulating the local magnetic field gradient, generated by EN, novel luminescent MNPs internalized in HeLa cancer cells. The controlling of the magnetic field intensity and estimation of the attractive force of EN was demonstrated. Both designs of EN and their main characteristics are also described. Depending on the distance and applied voltage, the attractive force ENs ranged from 0.056 ± 0.002 to 37.85 ± 3.40 pN. As a practical application of the presented, the evaluation of viscous properties of the HeLa cell’s cytoplasm, based on the measurement of the movement rate of MNPs inside cells under impact of a known magnetic force, was carried out; the viscosity was 1.45 ± 0.04 Pa·s.
Collapse
|
7
|
Dor YB, Kafri Y, Kardar M, Tailleur J. Passive objects in confined active fluids: A localization transition. Phys Rev E 2022; 106:044604. [PMID: 36397585 DOI: 10.1103/physreve.106.044604] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2022] [Accepted: 09/20/2022] [Indexed: 06/16/2023]
Abstract
We study how walls confining active fluids interact with asymmetric passive objects placed in their bulk. We show that the objects experience nonconservative long-ranged forces mediated by the active bath. To leading order, these forces can be computed using a generalized image theorem. The walls repel asymmetric objects, irrespective of their microscopic properties or their orientations. For circular cavities, we demonstrate how this may lead to the localization of asymmetric objects in the center of the cavity, something impossible for symmetric ones.
Collapse
Affiliation(s)
- Ydan Ben Dor
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Yariv Kafri
- Department of Physics, Technion-Israel Institute of Technology, Haifa 32000, Israel
| | - Mehran Kardar
- Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Julien Tailleur
- Université Paris Cité, Laboratoire Matière et Systèmes Complexes (MSC), UMR 7057 CNRS, F-75205 Paris, France
| |
Collapse
|
8
|
Dema A, van Haren J, Wittmann T. Optogenetic EB1 inactivation shortens metaphase spindles by disrupting cortical force-producing interactions with astral microtubules. Curr Biol 2022; 32:1197-1205.e4. [PMID: 35090591 PMCID: PMC8930524 DOI: 10.1016/j.cub.2022.01.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2021] [Revised: 12/09/2021] [Accepted: 01/07/2022] [Indexed: 10/19/2022]
Abstract
Chromosome segregation is accomplished by the mitotic spindle, a bipolar micromachine built primarily from microtubules. Different microtubule populations contribute to spindle function: kinetochore microtubules attach and transmit forces to chromosomes, antiparallel interpolar microtubules support spindle structure, and astral microtubules connect spindle poles to the cell cortex.1,2 In mammalian cells, end-binding (EB) proteins associate with all growing microtubule plus ends throughout the cell cycle and serve as adaptors for diverse +TIPs that control microtubule dynamics and interactions with other intracellular structures.3 Because binding of many +TIPs to EB1 and thus microtubule-end association is switched off by mitotic phosphorylation,4-6 the mitotic function of EBs remains poorly understood. To analyze how EB1 and associated +TIPs on different spindle microtubule populations contribute to mitotic spindle dynamics, we use a light-sensitive EB1 variant, π-EB1, that allows local, acute, and reversible inactivation of +TIP association with growing microtubule ends in live cells.7 We find that acute π-EB1 photoinactivation results in rapid and reversible metaphase spindle shortening and transient relaxation of tension across the central spindle. However, in contrast to interphase, π-EB1 photoinactivation does not inhibit microtubule growth in metaphase but instead increases astral microtubule length and number. Yet in the absence of EB1 activity, astral microtubules fail to engage the cortical dynein/dynactin machinery, and spindle poles move away from regions of π-EB1 photoinactivation. In conclusion, our optogenetic approach reveals mitotic EB1 functions that remain hidden in genetic experiments, likely due to compensatory molecular systems regulating vertebrate spindle dynamics.
Collapse
Affiliation(s)
- Alessandro Dema
- Department of Cell & Tissue Biology, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA
| | | | - Torsten Wittmann
- Department of Cell & Tissue Biology, University of California, San Francisco, 513 Parnassus Avenue, San Francisco, CA 94143, USA.
| |
Collapse
|
9
|
Luciano M, Versaevel M, Vercruysse E, Procès A, Kalukula Y, Remson A, Deridoux A, Gabriele S. Appreciating the role of cell shape changes in the mechanobiology of epithelial tissues. BIOPHYSICS REVIEWS 2022; 3:011305. [PMID: 38505223 PMCID: PMC10903419 DOI: 10.1063/5.0074317] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/07/2021] [Accepted: 02/23/2022] [Indexed: 03/21/2024]
Abstract
The wide range of epithelial cell shapes reveals the complexity and diversity of the intracellular mechanisms that serve to construct their morphology and regulate their functions. Using mechanosensitive steps, epithelial cells can sense a variety of different mechanochemical stimuli and adapt their behavior by reshaping their morphology. These changes of cell shape rely on a structural reorganization in space and time that generates modifications of the tensional state and activates biochemical cascades. Recent studies have started to unveil how the cell shape maintenance is involved in mechanical homeostatic tasks to sustain epithelial tissue folding, identity, and self-renewal. Here, we review relevant works that integrated mechanobiology to elucidate some of the core principles of how cell shape may be conveyed into spatial information to guide collective processes such as epithelial morphogenesis. Among many other parameters, we show that the regulation of the cell shape can be understood as the result of the interplay between two counteracting mechanisms: actomyosin contractility and intercellular adhesions, and that both do not act independently but are functionally integrated to operate on molecular, cellular, and tissue scales. We highlight the role of cadherin-based adhesions in force-sensing and mechanotransduction, and we report recent developments that exploit physics of liquid crystals to connect cell shape changes to orientational order in cell aggregates. Finally, we emphasize that the further intermingling of different disciplines to develop new mechanobiology assays will lead the way toward a unified picture of the contribution of cell shape to the pathophysiological behavior of epithelial tissues.
Collapse
Affiliation(s)
- Marine Luciano
- University of Mons, Interfaces and Complex Fluids Laboratory, Mechanobiology and Biomaterials Group, Research Institute for Biosciences, CIRMAP, 20 Place du Parc, B-7000 Mons, Belgium
| | - Marie Versaevel
- University of Mons, Interfaces and Complex Fluids Laboratory, Mechanobiology and Biomaterials Group, Research Institute for Biosciences, CIRMAP, 20 Place du Parc, B-7000 Mons, Belgium
| | - Eléonore Vercruysse
- University of Mons, Interfaces and Complex Fluids Laboratory, Mechanobiology and Biomaterials Group, Research Institute for Biosciences, CIRMAP, 20 Place du Parc, B-7000 Mons, Belgium
| | - Anthony Procès
- University of Mons, Interfaces and Complex Fluids Laboratory, Mechanobiology and Biomaterials Group, Research Institute for Biosciences, CIRMAP, 20 Place du Parc, B-7000 Mons, Belgium
| | - Yohalie Kalukula
- University of Mons, Interfaces and Complex Fluids Laboratory, Mechanobiology and Biomaterials Group, Research Institute for Biosciences, CIRMAP, 20 Place du Parc, B-7000 Mons, Belgium
| | - Alexandre Remson
- University of Mons, Interfaces and Complex Fluids Laboratory, Mechanobiology and Biomaterials Group, Research Institute for Biosciences, CIRMAP, 20 Place du Parc, B-7000 Mons, Belgium
| | - Amandine Deridoux
- University of Mons, Interfaces and Complex Fluids Laboratory, Mechanobiology and Biomaterials Group, Research Institute for Biosciences, CIRMAP, 20 Place du Parc, B-7000 Mons, Belgium
| | - Sylvain Gabriele
- University of Mons, Interfaces and Complex Fluids Laboratory, Mechanobiology and Biomaterials Group, Research Institute for Biosciences, CIRMAP, 20 Place du Parc, B-7000 Mons, Belgium
| |
Collapse
|
10
|
Contribution of cytoplasm viscoelastic properties to mitotic spindle positioning. Proc Natl Acad Sci U S A 2022; 119:2115593119. [PMID: 35169074 PMCID: PMC8872784 DOI: 10.1073/pnas.2115593119] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/28/2021] [Indexed: 11/21/2022] Open
Abstract
The regulation of mitotic spindle positioning is a key process for tissue architecture, embryo development, and stem cells. To date, most models have assumed that spindles are positioned by forces exerted by polar cytoskeleton networks, like microtubule asters or actomyosin bundles. Here, using in situ magnetic tweezers to apply calibrated forces and torques to mitotic spindles in live dividing sea urchin cells, we found that the viscoelastic properties of the cytoplasm medium in which spindles are embedded can hold spindles in place and move them back if their original position is perturbed. These viscoelastic forces are large and may significantly participate in the force balance that position and orient mitotic spindles in many cell types. Cells are filled with macromolecules and polymer networks that set scale-dependent viscous and elastic properties to the cytoplasm. Although the role of these parameters in molecular diffusion, reaction kinetics, and cellular biochemistry is being increasingly recognized, their contributions to the motion and positioning of larger organelles, such as mitotic spindles for cell division, remain unknown. Here, using magnetic tweezers to displace and rotate mitotic spindles in living embryos, we uncovered that the cytoplasm can impart viscoelastic reactive forces that move spindles, or passive objects with similar size, back to their original positions. These forces are independent of cytoskeletal force generators yet reach hundreds of piconewtons and scale with cytoplasm crowding. Spindle motion shears and fluidizes the cytoplasm, dissipating elastic energy and limiting spindle recoils with functional implications for asymmetric and oriented divisions. These findings suggest that bulk cytoplasm material properties may constitute important control elements for the regulation of division positioning and cellular organization.
Collapse
|
11
|
Lacroix B, Dumont J. Spatial and Temporal Scaling of Microtubules and Mitotic Spindles. Cells 2022; 11:cells11020248. [PMID: 35053364 PMCID: PMC8774166 DOI: 10.3390/cells11020248] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 01/07/2022] [Accepted: 01/09/2022] [Indexed: 02/01/2023] Open
Abstract
During cell division, the mitotic spindle, a macromolecular structure primarily comprised of microtubules, drives chromosome alignment and partitioning between daughter cells. Mitotic spindles can sense cellular dimensions in order to adapt their length and mass to cell size. This scaling capacity is particularly remarkable during early embryo cleavage when cells divide rapidly in the absence of cell growth, thus leading to a reduction of cell volume at each division. Although mitotic spindle size scaling can occur over an order of magnitude in early embryos, in many species the duration of mitosis is relatively short, constant throughout early development and independent of cell size. Therefore, a key challenge for cells during embryo cleavage is not only to assemble a spindle of proper size, but also to do it in an appropriate time window which is compatible with embryo development. How spatial and temporal scaling of the mitotic spindle is achieved and coordinated with the duration of mitosis remains elusive. In this review, we will focus on the mechanisms that support mitotic spindle spatial and temporal scaling over a wide range of cell sizes and cellular contexts. We will present current models and propose alternative mechanisms allowing cells to spatially and temporally coordinate microtubule and mitotic spindle assembly.
Collapse
Affiliation(s)
- Benjamin Lacroix
- Centre de Recherche de Biologie Cellulaire de Montpellier (CRBM), CNRS UMR 5237, Université de Montpellier, 1919 Route de Mende, CEDEX 5, 34293 Montpellier, France
- Correspondence:
| | - Julien Dumont
- Université de Paris, CNRS, Institut Jacques Monod, F-75013 Paris, France;
| |
Collapse
|
12
|
Peddireddy KR, Michieletto D, Aguirre G, Garamella J, Khanal P, Robertson-Anderson RM. DNA Conformation Dictates Strength and Flocculation in DNA-Microtubule Composites. ACS Macro Lett 2021; 10:1540-1548. [PMID: 35549144 PMCID: PMC9239750 DOI: 10.1021/acsmacrolett.1c00638] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Polymer topology has been shown to play a key role in tuning the dynamics of complex fluids and gels. At the same time, polymer composites, ubiquitous in everyday life, have been shown to exhibit emergent desirable mechanical properties not attainable in single-species systems. Yet, how topology impacts the dynamics and structure of polymer composites remains poorly understood. Here, we create composites of rigid rods (microtubules) polymerized within entangled solutions of flexible linear and ring polymers (DNA) of equal length. We couple optical tweezers microrheology with confocal microscopy and scaled particle theory to show that composites with linear DNA exhibit a strongly nonmonotonic dependence of elasticity and stiffness on microtubule concentration due to depletion-driven polymerization and flocculation of microtubules. In contrast, composites containing ring DNA show a much more modest monotonic increase in elastic strength with microtubule concentration, which we demonstrate arises from the decreased conformational size and increased miscibility of rings.
Collapse
Affiliation(s)
- Karthik R Peddireddy
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, California 92110, United States
| | - Davide Michieletto
- School of Physics and Astronomy, University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, United Kingdom
- MRC Human Genetics Unit, Institute of Genetics and Molecular Medicine University of Edinburgh, Edinburgh EH4 2XU, United Kingdom
| | - Gina Aguirre
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, California 92110, United States
| | - Jonathan Garamella
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, California 92110, United States
| | - Pawan Khanal
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, California 92110, United States
| | - Rae M Robertson-Anderson
- Department of Physics and Biophysics, University of San Diego, 5998 Alcala Park, San Diego, California 92110, United States
| |
Collapse
|
13
|
Cell division geometries as central organizers of early embryo development. Semin Cell Dev Biol 2021; 130:3-11. [PMID: 34419349 DOI: 10.1016/j.semcdb.2021.08.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Accepted: 08/08/2021] [Indexed: 11/24/2022]
Abstract
Early cellular patterning is a critical step of embryonic development that determines the proper progression of morphogenesis in all metazoans. It relies on a series of rapid reductive divisions occurring simultaneously with the specification of the fate of different subsets of cells. Multiple species developmental strategies emerged in the form of a unique cleavage pattern with stereotyped division geometries. Cleavage geometries have long been associated to the emergence of canonical developmental features such as cell cycle asynchrony, zygotic genome activation and fate specification. Yet, the direct causal role of division positioning on blastomere cell behavior remain partially understood. Oriented and/or asymmetric divisions define blastomere cell sizes, contacts and positions, with potential immediate impact on cellular decisions, lineage specification and morphogenesis. Division positions also instruct daughter cells polarity, mechanics and geometries, thereby influencing subsequent division events, in an emergent interplay that may pattern early embryos independently of firm deterministic genetic programs. We here review the recent literature which helped to delineate mechanisms and functions of division positioning in early embryos.
Collapse
|
14
|
Mechanical Mechanisms of Chromosome Segregation. Cells 2021; 10:cells10020465. [PMID: 33671543 PMCID: PMC7926803 DOI: 10.3390/cells10020465] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Revised: 02/17/2021] [Accepted: 02/19/2021] [Indexed: 12/11/2022] Open
Abstract
Chromosome segregation—the partitioning of genetic material into two daughter cells—is one of the most crucial processes in cell division. In all Eukaryotes, chromosome segregation is driven by the spindle, a microtubule-based, self-organizing subcellular structure. Extensive research performed over the past 150 years has identified numerous commonalities and contrasts between spindles in different systems. In this review, we use simple coarse-grained models to organize and integrate previous studies of chromosome segregation. We discuss sites of force generation in spindles and fundamental mechanical principles that any understanding of chromosome segregation must be based upon. We argue that conserved sites of force generation may interact differently in different spindles, leading to distinct mechanical mechanisms of chromosome segregation. We suggest experiments to determine which mechanical mechanism is operative in a particular spindle under study. Finally, we propose that combining biophysical experiments, coarse-grained theories, and evolutionary genetics will be a productive approach to enhance our understanding of chromosome segregation in the future.
Collapse
|
15
|
Shamipour S, Caballero-Mancebo S, Heisenberg CP. Cytoplasm's Got Moves. Dev Cell 2021; 56:213-226. [PMID: 33321104 DOI: 10.1016/j.devcel.2020.12.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 10/22/2020] [Accepted: 11/30/2020] [Indexed: 01/01/2023]
Abstract
Cytoplasm is a gel-like crowded environment composed of various macromolecules, organelles, cytoskeletal networks, and cytosol. The structure of the cytoplasm is highly organized and heterogeneous due to the crowding of its constituents and their effective compartmentalization. In such an environment, the diffusive dynamics of the molecules are restricted, an effect that is further amplified by clustering and anchoring of molecules. Despite the crowded nature of the cytoplasm at the microscopic scale, large-scale reorganization of the cytoplasm is essential for important cellular functions, such as cell division and polarization. How such mesoscale reorganization of the cytoplasm is achieved, especially for large cells such as oocytes or syncytial tissues that can span hundreds of micrometers in size, is only beginning to be understood. In this review, we will discuss recent advances in elucidating the molecular, cellular, and biophysical mechanisms by which the cytoskeleton drives cytoplasmic reorganization across different scales, structures, and species.
Collapse
Affiliation(s)
- Shayan Shamipour
- Institute of Science and Technology Austria, Klosterneuburg, Austria
| | | | | |
Collapse
|
16
|
Pelletier JF, Field CM, Fürthauer S, Sonnett M, Mitchison TJ. Co-movement of astral microtubules, organelles and F-actin by dynein and actomyosin forces in frog egg cytoplasm. eLife 2020; 9:e60047. [PMID: 33284105 PMCID: PMC7759381 DOI: 10.7554/elife.60047] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Accepted: 12/05/2020] [Indexed: 12/22/2022] Open
Abstract
How bulk cytoplasm generates forces to separate post-anaphase microtubule (MT) asters in Xenopus laevis and other large eggs remains unclear. Previous models proposed that dynein-based, inward organelle transport generates length-dependent pulling forces that move centrosomes and MTs outwards, while other components of cytoplasm are static. We imaged aster movement by dynein and actomyosin forces in Xenopus egg extracts and observed outward co-movement of MTs, endoplasmic reticulum (ER), mitochondria, acidic organelles, F-actin, keratin, and soluble fluorescein. Organelles exhibited a burst of dynein-dependent inward movement at the growing aster periphery, then mostly halted inside the aster, while dynein-coated beads moved to the aster center at a constant rate, suggesting organelle movement is limited by brake proteins or other sources of drag. These observations call for new models in which all components of the cytoplasm comprise a mechanically integrated aster gel that moves collectively in response to dynein and actomyosin forces.
Collapse
Affiliation(s)
- James F Pelletier
- Department of Systems Biology, Harvard Medical SchoolBostonUnited States
- Marine Biological LaboratoryWoods HoleUnited States
- Department of Physics, Massachusetts Institute of TechnologyCambridgeUnited States
| | - Christine M Field
- Department of Systems Biology, Harvard Medical SchoolBostonUnited States
- Marine Biological LaboratoryWoods HoleUnited States
| | | | - Matthew Sonnett
- Department of Systems Biology, Harvard Medical SchoolBostonUnited States
| | - Timothy J Mitchison
- Department of Systems Biology, Harvard Medical SchoolBostonUnited States
- Marine Biological LaboratoryWoods HoleUnited States
| |
Collapse
|
17
|
Palenzuela H, Lacroix B, Sallé J, Minami K, Shima T, Jegou A, Romet-Lemonne G, Minc N. In Vitro Reconstitution of Dynein Force Exertion in a Bulk Viscous Medium. Curr Biol 2020; 30:4534-4540.e7. [PMID: 32946749 DOI: 10.1016/j.cub.2020.08.078] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2020] [Revised: 08/03/2020] [Accepted: 08/24/2020] [Indexed: 11/28/2022]
Abstract
The forces generated by microtubules (MTs) and their associated motors orchestrate essential cellular processes ranging from vesicular trafficking to centrosome positioning [1, 2]. To date, most studies have focused on MT force exertion by motors anchored to a static surface, such as the cell cortex in vivo or glass surfaces in vitro [2-4]. However, motors also transport large cargos and endomembrane networks, whose hydrodynamic interactions with the viscous cytoplasm should generate sizable forces in bulk. Such forces may contribute to MT aster centration, organization, and orientation [5-14] but have yet to be evidenced and studied in a minimal reconstituted system. By developing a bulk motility assay, based on stabilized MTs and dynein-coated beads freely floating in a viscous medium away from any surface, we demonstrate that the motion of a cargo exerts a pulling force on the MT and propels it in opposite direction. Quantification of resulting MT movements for different motors, motor velocities, over a range of cargo sizes and medium viscosities shows that the efficiency of this mechanism is primarily determined by cargo size and MT length. Forces exerted by cargos are additive, allowing us to recapitulate tug-of-war situations or bi-dimensional motions of minimal asters. These data also reveal unappreciated effects of the nature of viscous crowders and hydrodynamic interactions between cargos and MTs, likely relevant to understand this mode of force exertion in living cells. This study reinforces the notion that endomembrane transport can exert significant forces on MTs.
Collapse
Affiliation(s)
| | - Benjamin Lacroix
- Institut Jacques Monod, Université de Paris, CNRS, 75006 Paris, France
| | - Jérémy Sallé
- Institut Jacques Monod, Université de Paris, CNRS, 75006 Paris, France
| | - Katsuhiko Minami
- Graduate School of Science, The University of Tokyo, 113-0033 Tokyo, Japan
| | - Tomohiro Shima
- Graduate School of Science, The University of Tokyo, 113-0033 Tokyo, Japan
| | - Antoine Jegou
- Institut Jacques Monod, Université de Paris, CNRS, 75006 Paris, France
| | | | - Nicolas Minc
- Institut Jacques Monod, Université de Paris, CNRS, 75006 Paris, France.
| |
Collapse
|
18
|
Ierushalmi N, Malik-Garbi M, Manhart A, Abu Shah E, Goode BL, Mogilner A, Keren K. Centering and symmetry breaking in confined contracting actomyosin networks. eLife 2020; 9:55368. [PMID: 32314730 PMCID: PMC7173961 DOI: 10.7554/elife.55368] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 03/19/2020] [Indexed: 11/13/2022] Open
Abstract
Centering and decentering of cellular components is essential for internal organization of cells and their ability to perform basic cellular functions such as division and motility. How cells achieve proper localization of their organelles is still not well-understood, especially in large cells such as oocytes. Here, we study actin-based positioning mechanisms in artificial cells with persistently contracting actomyosin networks, generated by encapsulating cytoplasmic Xenopus egg extracts into cell-sized ‘water-in-oil’ droplets. We observe size-dependent localization of the contraction center, with a symmetric configuration in larger cells and a polar one in smaller cells. Centering is achieved via a hydrodynamic mechanism based on Darcy friction between the contracting network and the surrounding cytoplasm. During symmetry breaking, transient attachments to the cell boundary drive the contraction center to a polar location. The centering mechanism is cell-cycle dependent and weakens considerably during interphase. Our findings demonstrate a robust, yet tunable, mechanism for subcellular localization. In order to survive, cells need to react to their environment and change their shape or the localization of their internal components. For example, the nucleus – the compartment that contains the genetic information – is often localized at the center of the cell, but it can also be positioned at the side, for instance when cells move or divide asymmetrically. Cells use multiple positioning mechanisms to move their internal components, including a process that relies on networks of filaments made of a protein known as actin. These networks are constantly remodeled as actin proteins are added and removed from the network. Embedded molecular motors can cause the network of actin filaments to contract and push or pull on the compartments. Yet, the exact way these networks localize components in the cell remains unclear, especially in eggs and other large cells. To investigate this question, Ierushalmi et al. studied the actin networks in artificial cells that they created by enclosing the contents of frog eggs in small droplets surrounded by oil. This showed that the networks contracted either to the center of the cell or to its side. Friction between the contracting actin network and the fluid in the cell generated a force that tends to push the contraction center towards the middle of the cell. In larger cells, this led to the centering of the actin network. In smaller cells however, the network transiently attached to the boundary of the cell, leading the contraction center to be pulled to one side. By developing simpler artificial cells that mimic the positioning processes seen in real-life cells, Ierushalmi et al. discovered new mechanisms for how cells may center or de-center their components. This knowledge may be useful to understand diseases that can emerge when the nucleus or other compartments fail to move to the right location, and which are associated with certain organs developing incorrectly.
Collapse
Affiliation(s)
- Niv Ierushalmi
- Department of Physics, Technion- Israel Institute of Technology, Haifa, Israel
| | - Maya Malik-Garbi
- Department of Physics, Technion- Israel Institute of Technology, Haifa, Israel
| | - Angelika Manhart
- Department of Mathematics, University College London, London, United Kingdom
| | - Enas Abu Shah
- Department of Physics, Technion- Israel Institute of Technology, Haifa, Israel.,Kennedy Institute of Rheumatology, University of Oxford, Oxford, United Kingdom
| | - Bruce L Goode
- Department of Biology, Brandeis University, Waltham, United States
| | - Alex Mogilner
- Courant Institute of Mathematical Sciences and Department of Biology, New York University, New York, United States
| | - Kinneret Keren
- Department of Physics, Technion- Israel Institute of Technology, Haifa, Israel.,Network Biology Research Laboratories and Russell Berrie Nanotechnology Institute, Technion - Israel Institute of Technology, Haifa, Israel
| |
Collapse
|