1
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Hughes JM, Martinez-Torres C, Beta C, Edelstein-Keshet L, Yochelis A. A dissipative mass conserved reaction-diffusion system reveals switching between coexisting polar and oscillatory cell motility states. CHAOS (WOODBURY, N.Y.) 2025; 35:051103. [PMID: 40424020 DOI: 10.1063/5.0274689] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/08/2025] [Accepted: 05/08/2025] [Indexed: 05/28/2025]
Abstract
Motile eukaryotic cells display distinct modes of migration that often occur within the same cell type. It remains unclear, however, whether transitions between the migratory modes require changes in external conditions, or whether the different modes are coexisting states that emerge from the underlying signaling network. Using a simplified mass-conserved reaction-diffusion model of small GTPase signaling with F-actin mediated feedback, we uncover a distinct bistable mechanism (involving gradient-like phase-separation and traveling waves) and a regime where a polarized mode of migration coexists with spatiotemporal oscillations; the latter, in larger domains, including in three-dimensional surface geometry, result in disordered patterns even in the absence of noise or shape deformations. Indeed, experimental observations of Dictyostelium discoideum show that, upon collision with a rigid boundary, cells may switch from polarized to disordered motion.
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Affiliation(s)
- Jack M Hughes
- Department of Mathematics, University of British Columbia, Vancouver V6T 1Z2, Canada
| | | | - Carsten Beta
- Institute of Physics and Astronomy, University of Potsdam, Potsdam 14476, Germany
| | - Leah Edelstein-Keshet
- Department of Mathematics, University of British Columbia, Vancouver V6T 1Z2, Canada
| | - Arik Yochelis
- Swiss Institute for Dryland Environmental and Energy Research, Sede Boqer Campus, Midreshet Ben-Gurion 8499000, Israel
- Department of Physics, Ben-Gurion University of the Negev, Be'er Sheva 8410501, Israel
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2
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Chomchai D, Leda M, Golding A, von Dassow G, Bement WM, Goryachev AB. Rho GTPase dynamics distinguish between models of cortical excitability. Curr Biol 2025; 35:1414-1421.e4. [PMID: 40010332 DOI: 10.1016/j.cub.2025.02.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2024] [Revised: 01/06/2025] [Accepted: 02/03/2025] [Indexed: 02/28/2025]
Abstract
The Rho GTPases pattern the cell cortex in a variety of fundamental cell-morphogenetic processes, including division, wound repair, and locomotion. It has recently become apparent that this patterning arises from the ability of the Rho GTPases to self-organize into static and migrating spots, contractile pulses, and propagating waves in cells from yeasts to mammals.1 These self-organizing Rho GTPase patterns have been explained by a variety of theoretical models that require multiple interacting positive and negative feedback loops. However, it is often difficult, if not impossible, to discriminate between different models simply because the available experimental data do not simultaneously capture the dynamics of multiple molecular concentrations and biomechanical variables at fine spatial and temporal resolution. Specifically, most studies typically provide either the total Rho GTPase signal or the Rho GTPase activity, as reported by various sensors, but not both. Therefore, it remains largely unknown how membrane accumulation of Rho GTPases (i.e., Rho membrane enrichment) is related to Rho activity. Here, we dissect the dynamics of RhoA by simultaneously imaging both total RhoA and active RhoA in propagating waves of Rho activity and F-actin polymerization.2,3,4,5 We find that within nascent waves, accumulation of active RhoA precedes that of total RhoA, and we exploit this finding to distinguish between two popular theoretical models previously used to explain propagating cortical Rho waves.
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Affiliation(s)
- Dominic Chomchai
- Graduate Program in Cellular and Molecular Biology, University of Wisconsin-Madison, 250 N Mills St, Madison, WI 53706, USA; Center for Quantitative Imaging, University of Wisconsin-Madison, 250 N Mills St, Madison, WI 53706, USA; Department of Integrative Biology, University of Wisconsin-Madison, 250 N Mills St, Madison, WI 53706, USA
| | - Marcin Leda
- Centre for Engineering Biology, School of Biological Sciences, University of Edinburgh, C.H. Waddington Building, Max Born Crescent, EH9 3BF Edinburgh, UK
| | - Adriana Golding
- Graduate Program in Cellular and Molecular Biology, University of Wisconsin-Madison, 250 N Mills St, Madison, WI 53706, USA; Neurosciences and Cellular and Structural Biology Division, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 1 Center Dr, Bethesda, MD 20892, USA
| | - George von Dassow
- Oregon Institute of Marine Biology, 63466 Boat Basin Road, Charleston, OR 97420, USA.
| | - William M Bement
- Graduate Program in Cellular and Molecular Biology, University of Wisconsin-Madison, 250 N Mills St, Madison, WI 53706, USA; Center for Quantitative Imaging, University of Wisconsin-Madison, 250 N Mills St, Madison, WI 53706, USA; Department of Integrative Biology, University of Wisconsin-Madison, 250 N Mills St, Madison, WI 53706, USA.
| | - Andrew B Goryachev
- Centre for Engineering Biology, School of Biological Sciences, University of Edinburgh, C.H. Waddington Building, Max Born Crescent, EH9 3BF Edinburgh, UK.
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3
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Li Y, Zhang H, Yang F, Zhu D, Chen S, Wang Z, Wei Z, Yang Z, Jia J, Zhang Y, Wang D, Ma M, Kang X. Mechanisms and therapeutic potential of disulphidptosis in cancer. Cell Prolif 2025; 58:e13752. [PMID: 39354653 DOI: 10.1111/cpr.13752] [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: 06/19/2024] [Revised: 08/30/2024] [Accepted: 09/14/2024] [Indexed: 10/04/2024] Open
Abstract
SLC7A11 plays a pivotal role in tumour development by facilitating cystine import to enhance glutathione synthesis and counteract oxidative stress. Disulphidptosis, an emerging form of cell death observed in cells with high expression of SLC7A11 under glucose deprivation, is regulated through reduction-oxidation reactions and disulphide bond formation. This process leads to contraction and collapse of the F-actin cytoskeleton from the plasma membrane, ultimately resulting in cellular demise. Compared to other forms of cell death, disulphidptosis exhibits distinctive characteristics and regulatory mechanisms. This mechanism provides novel insights and innovative strategies for cancer treatment while also inspiring potential therapeutic approaches for other diseases. Our review focuses on elucidating the molecular mechanism underlying disulphidptosis and its connection with the actin cytoskeleton, identifying alternative metabolic forms of cell death, as well as offering insights into disulphidptosis-based cancer therapy. A comprehensive understanding of disulphidptosis will contribute to our knowledge about fundamental cellular homeostasis and facilitate the development of groundbreaking therapies for disease treatment.
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Affiliation(s)
- Yanhu Li
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
| | - Haijun Zhang
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
- The Second People's Hospital of Gansu Province, Lanzhou, PR China
| | - Fengguang Yang
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
| | - Daxue Zhu
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
| | - Shijie Chen
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
| | - Zhaoheng Wang
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
| | - Ziyan Wei
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
| | - Zhili Yang
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
| | - Jingwen Jia
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
| | - Yizhi Zhang
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
| | - Dongxin Wang
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
| | - Mingdong Ma
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
| | - Xuewen Kang
- Lanzhou University Second Hospital, Lanzhou, PR China
- Orthopaedics Key Laboratory of Gansu Province, Lanzhou, PR China
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4
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Šoštar M, Marinović M, Filić V, Pavin N, Weber I. Oscillatory dynamics of Rac1 activity in Dictyostelium discoideum amoebae. PLoS Comput Biol 2024; 20:e1012025. [PMID: 39652619 DOI: 10.1371/journal.pcbi.1012025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2024] [Revised: 12/19/2024] [Accepted: 11/21/2024] [Indexed: 12/21/2024] Open
Abstract
Small GTPases of the Rho family play a central role in the regulation of cell motility by controlling the remodeling of the actin cytoskeleton. In the amoeboid cells of Dictyostelium discoideum, the active form of the Rho GTPase Rac1 regulates actin polymerases at the leading edge and actin filament bundling proteins at the posterior cortex of polarized cells. We monitored the spatiotemporal dynamics of Rac1 and its effector DGAP1 in vegetative amoebae using specific fluorescent probes. We observed that plasma membrane domains enriched in active Rac1 not only exhibited stable polarization, but also showed rotations and oscillations, whereas DGAP1 was depleted from these regions. To simulate the observed dynamics of the two proteins, we developed a mass-conserving reaction-diffusion model based on the circulation of Rac1 between the membrane and the cytoplasm coupled with its activation by GEFs, deactivation by GAPs and interaction with DGAP1. Our theoretical model accurately reproduced the experimentally observed dynamic patterns, including the predominant anti-correlation between active Rac1 and DGAP1. Significantly, the model predicted a new colocalization regime of these two proteins in polarized cells, which we confirmed experimentally. In summary, our results improve the understanding of Rac1 dynamics and reveal how the occurrence and transitions between different regimes depend on biochemical reaction rates, protein levels and cell size. This study not only expands our knowledge of the behavior of Rac1 GTPases in D. discoideum amoebae but also demonstrates how specific modes of interaction between Rac1 and its effector DGAP1 lead to their counterintuitively anti-correlated dynamics.
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Affiliation(s)
- Marko Šoštar
- Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | - Maja Marinović
- Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | - Vedrana Filić
- Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
| | - Nenad Pavin
- Department of Physics, Faculty of Science, University of Zagreb, Zagreb, Croatia
| | - Igor Weber
- Division of Molecular Biology, Ruđer Bošković Institute, Zagreb, Croatia
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5
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Waechtler BE, Jayasankar R, Morin EP, Robinson DN. Benefits and challenges of reconstituting the actin cortex. Cytoskeleton (Hoboken) 2024; 81:843-863. [PMID: 38520148 PMCID: PMC11417134 DOI: 10.1002/cm.21855] [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: 12/05/2023] [Revised: 02/21/2024] [Accepted: 03/05/2024] [Indexed: 03/25/2024]
Abstract
The cell's ability to change shape is a central feature in many cellular processes, including cytokinesis, motility, migration, and tissue formation. The cell constructs a network of contractile proteins underneath the cell membrane to form the cortex, and the reorganization of these components directly contributes to cellular shape changes. The desire to mimic these cell shape changes to aid in the creation of a synthetic cell has been increasing. Therefore, membrane-based reconstitution experiments have flourished, furthering our understanding of the minimal components the cell uses throughout these processes. Although biochemical approaches increased our understanding of actin, myosin II, and actin-associated proteins, using membrane-based reconstituted systems has further expanded our understanding of actin structures and functions because membrane-cortex interactions can be analyzed. In this review, we highlight the recent developments in membrane-based reconstitution techniques. We examine the current findings on the minimal components needed to recapitulate distinct actin structures and functions and how they relate to the cortex's impact on cellular mechanical properties. We also explore how co-processing of computational models with wet-lab experiments enhances our understanding of these properties. Finally, we emphasize the benefits and challenges inherent to membrane-based, reconstitution assays, ranging from the advantage of precise control over the system to the difficulty of integrating these findings into the complex cellular environment.
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Affiliation(s)
- Brooke E. Waechtler
- Department of Cell Biology, Johns Hopkins University, School of Medicine, 725 N Wolfe Street, Baltimore, MD 21205
| | - Rajan Jayasankar
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Whiting School of Engineering, 725 N Wolfe Street, Baltimore, MD 21205
| | - Emma P. Morin
- Department of Cell Biology, Johns Hopkins University, School of Medicine, 725 N Wolfe Street, Baltimore, MD 21205
| | - Douglas N. Robinson
- Department of Cell Biology, Johns Hopkins University, School of Medicine, 725 N Wolfe Street, Baltimore, MD 21205
- Department of Chemical and Biomolecular Engineering, Johns Hopkins University, Whiting School of Engineering, 725 N Wolfe Street, Baltimore, MD 21205
- Department of Pharmacology and Molecular Sciences, Johns Hopkins University, School of Medicine, 725 N Wolfe Street, Baltimore, MD 21205
- Department of Medicine, Johns Hopkins University, School of Medicine, 725 N Wolfe Street, Baltimore, MD 21205
- Department of Oncology, Johns Hopkins University, School of Medicine, 725 N Wolfe Street, Baltimore, MD 21205
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6
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Murray EC, Hodge GM, Lee LS, Mitchell CAR, Lombardo AT. The Rho effector ARHGAP18 coordinates a Hippo pathway feedback loop through YAP and Merlin to regulate the cytoskeleton and epithelial cell polarity. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.11.26.625473. [PMID: 39651219 PMCID: PMC11623603 DOI: 10.1101/2024.11.26.625473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 12/11/2024]
Abstract
The organization of the cell's cytoskeletal filaments is coordinated through a complex symphony of signaling cascades originating from internal and external cues. Two major actin regulatory pathways are signal transduction through Rho family GTPases and growth and proliferation signaling through the Hippo pathway. These two pathways act to define the actin cytoskeleton, controlling foundational cellular attributes such as morphology and polarity. In this study, we use human epithelial cells to investigate the interplay between the Hippo and Rho Family signaling pathways, which have predominantly been characterized as independent actin regulatory mechanisms. We identify that the RhoA effector, ARHGAP18, forms a complex with the Hippo pathway transcription factor YAP to address a long-standing enigma in the field. Using super resolution STORM microscopy, we characterize the changes in the actin cytoskeleton, on the single filament level, that arise from CRISPR/Cas9 knockout of ARHGAP18. We report that the loss of ARHGAP18 results in alterations of the cell that derive from both aberrant RhoA signaling and inappropriate nuclear localization of YAP. These findings indicate that the Hippo and Rho family GTPase signaling cascades are coordinated in their temporal and spatial control of the actin cytoskeleton.
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7
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Cebrián-Lacasa D, Leda M, Goryachev AB, Gelens L. Wave-driven phase wave patterns in a ring of FitzHugh-Nagumo oscillators. Phys Rev E 2024; 110:054208. [PMID: 39690647 DOI: 10.1103/physreve.110.054208] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2024] [Accepted: 09/24/2024] [Indexed: 12/19/2024]
Abstract
We explore a biomimetic model that simulates a cell, with the internal cytoplasm represented by a two-dimensional circular domain and the external cortex by a surrounding ring, both modeled using FitzHugh-Nagumo systems. The external ring is dynamically influenced by a pacemaker-driven wave originating from the internal domain, leading to the emergence of three distinct dynamical states based on the varying strengths of coupling. The range of dynamics observed includes phase patterning, the propagation of phase waves, and interactions between traveling and phase waves. A simplified linear model effectively explains the mechanisms behind the variety of phase patterns observed, providing insights into the complex interplay between a cell's internal and external environments.
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Affiliation(s)
| | | | | | - Lendert Gelens
- Laboratory of Dynamics in Biological Systems, Department of Cellular and Molecular Medicine, KU Leuven, Herestraat 49, 3000 Leuven, Belgium
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8
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Harrell MA, Liu Z, Campbell BF, Chinsen O, Hong T, Das M. Arp2/3-dependent endocytosis ensures Cdc42 oscillations by removing Pak1-mediated negative feedback. J Cell Biol 2024; 223:e202311139. [PMID: 39012625 PMCID: PMC11259211 DOI: 10.1083/jcb.202311139] [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: 11/21/2023] [Revised: 05/10/2024] [Accepted: 07/01/2024] [Indexed: 07/17/2024] Open
Abstract
The GTPase Cdc42 regulates polarized growth in most eukaryotes. In the bipolar yeast Schizosaccharomyces pombe, Cdc42 activation cycles periodically at sites of polarized growth. These periodic cycles are caused by alternating positive feedback and time-delayed negative feedback loops. At each polarized end, negative feedback is established when active Cdc42 recruits the Pak1 kinase to prevent further Cdc42 activation. It is unclear how Cdc42 activation returns to each end after Pak1-dependent negative feedback. We find that disrupting branched actin-mediated endocytosis disables Cdc42 reactivation at the cell ends. Using experimental and mathematical approaches, we show that endocytosis-dependent Pak1 removal from the cell ends allows the Cdc42 activator Scd1 to return to that end to enable reactivation of Cdc42. Moreover, we show that Pak1 elicits its own removal via activation of endocytosis. These findings provide a deeper insight into the self-organization of Cdc42 regulation and reveal previously unknown feedback with endocytosis in the establishment of cell polarity.
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Affiliation(s)
| | - Ziyi Liu
- Department of Biochemistry and Cellular & Molecular Biology, University of Tennessee, Knoxville, TN, USA
| | | | - Olivia Chinsen
- Biology Department, Boston College, Chestnut Hill, MA, USA
| | - Tian Hong
- Department of Biochemistry and Cellular & Molecular Biology, University of Tennessee, Knoxville, TN, USA
| | - Maitreyi Das
- Biology Department, Boston College, Chestnut Hill, MA, USA
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9
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Werner ME, Ray DD, Breen C, Staddon MF, Jug F, Banerjee S, Maddox AS. Mechanical and biochemical feedback combine to generate complex contractile oscillations in cytokinesis. Curr Biol 2024; 34:3201-3214.e5. [PMID: 38991614 PMCID: PMC11634113 DOI: 10.1016/j.cub.2024.06.037] [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: 12/08/2023] [Revised: 04/22/2024] [Accepted: 06/13/2024] [Indexed: 07/13/2024]
Abstract
The actomyosin cortex is an active material that generates force to drive shape changes via cytoskeletal remodeling. Cytokinesis is the essential cell division event during which a cortical actomyosin ring closes to separate two daughter cells. Our active gel theory predicted that actomyosin systems controlled by a biochemical oscillator and experiencing mechanical strain would exhibit complex spatiotemporal behavior. To test whether active materials in vivo exhibit spatiotemporally complex kinetics, we imaged the C. elegans embryo with unprecedented temporal resolution and discovered that sections of the cytokinetic cortex undergo periodic phases of acceleration and deceleration. Contractile oscillations exhibited a range of periodicities, including those much longer periods than the timescale of RhoA pulses, which was shorter in cytokinesis than in any other biological context. Modifying mechanical feedback in vivo or in silico revealed that the period of contractile oscillation is prolonged as a function of the intensity of mechanical feedback. Fast local ring ingression occurs where speed oscillations have long periods, likely due to increased local stresses and, therefore, mechanical feedback. Fast ingression also occurs where material turnover is high, in vivo and in silico. We propose that downstream of initiation by pulsed RhoA activity, mechanical feedback, including but not limited to material advection, extends the timescale of contractility beyond that of biochemical input and, therefore, makes it robust to fluctuations in activation. Circumferential propagation of contractility likely allows for sustained contractility despite cytoskeletal remodeling necessary to recover from compaction. Thus, like biochemical feedback, mechanical feedback affords active materials responsiveness and robustness.
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Affiliation(s)
- Michael E Werner
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Dylan D Ray
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Coleman Breen
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA
| | - Michael F Staddon
- Center for Systems Biology Dresden, Max Planck Institute for the Physics of Complex Systems, and Max Planck Institute of Molecular Cell Biology and Genetics, Dresden, Germany
| | - Florian Jug
- Computational Biology Research Centre, Human Technopole, Milan, Italy
| | - Shiladitya Banerjee
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | - Amy Shaub Maddox
- Department of Biology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599, USA.
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10
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Jackson JA, Denk-Lobnig M, Kitzinger KA, Martin AC. Change in RhoGAP and RhoGEF availability drives transitions in cortical patterning and excitability in Drosophila. Curr Biol 2024; 34:2132-2146.e5. [PMID: 38688282 PMCID: PMC11111359 DOI: 10.1016/j.cub.2024.04.021] [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: 11/08/2023] [Revised: 02/13/2024] [Accepted: 04/09/2024] [Indexed: 05/02/2024]
Abstract
Actin cortex patterning and dynamics are critical for cell shape changes. These dynamics undergo transitions during development, often accompanying changes in collective cell behavior. Although mechanisms have been established for individual cells' dynamic behaviors, the mechanisms and specific molecules that result in developmental transitions in vivo are still poorly understood. Here, we took advantage of two developmental systems in Drosophila melanogaster to identify conditions that altered cortical patterning and dynamics. We identified a Rho guanine nucleotide exchange factor (RhoGEF) and Rho GTPase activating protein (RhoGAP) pair required for actomyosin waves in egg chambers. Specifically, depletion of the RhoGEF, Ect2, or the RhoGAP, RhoGAP15B, disrupted actomyosin wave induction, and both proteins relocalized from the nucleus to the cortex preceding wave formation. Furthermore, we found that overexpression of a different RhoGEF and RhoGAP pair, RhoGEF2 and Cumberland GAP (C-GAP), resulted in actomyosin waves in the early embryo, during which RhoA activation precedes actomyosin assembly by ∼4 s. We found that C-GAP was recruited to actomyosin waves, and disrupting F-actin polymerization altered the spatial organization of both RhoA signaling and the cytoskeleton in waves. In addition, disrupting F-actin dynamics increased wave period and width, consistent with a possible role for F-actin in promoting delayed negative feedback. Overall, we showed a mechanism involved in inducing actomyosin waves that is essential for oocyte development and is general to other cell types, such as epithelial and syncytial cells.
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Affiliation(s)
- Jonathan A Jackson
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA; Graduate Program in Biophysics, Harvard University, 86 Brattle Street, Cambridge, MA 02138, USA
| | - Marlis Denk-Lobnig
- Department of Biophysics, University of Michigan, 1109 Geddes Ave., Ann Arbor, MI 48109, USA
| | - Katherine A Kitzinger
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA
| | - Adam C Martin
- Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA.
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11
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Chomchai D, Leda M, Golding A, von Dassow G, Bement WM, Goryachev AB. Testing models of cell cortex wave generation by Rho GTPases. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.29.591685. [PMID: 38746143 PMCID: PMC11092441 DOI: 10.1101/2024.04.29.591685] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2024]
Abstract
The Rho GTPases pattern the cell cortex in a variety of fundamental cell-morphogenetic processes including division, wound repair, and locomotion. It has recently become apparent that this patterning arises from the ability of the Rho GTPases to self-organize into static and migrating spots, contractile pulses, and propagating waves in cells from yeasts to mammals 1 . These self-organizing Rho GTPase patterns have been explained by a variety of theoretical models which require multiple interacting positive and negative feedback loops. However, it is often difficult, if not impossible, to discriminate between different models simply because the available experimental data do not simultaneously capture the dynamics of multiple molecular concentrations and biomechanical variables at fine spatial and temporal resolution. Specifically, most studies typically provide either the total Rho GTPase signal or the Rho GTPase activity as reported by various sensors, but not both. Therefore, it remains largely unknown how membrane accumulation of Rho GTPases (i.e., Rho membrane enrichment) is related to Rho activity. Here we dissect the dynamics of RhoA by simultaneously imaging both total RhoA and active RhoA in the regime of acute cortical excitability 2 , characterized by pronounced waves of Rho activity and F-actin polymerization 3-5 . We find that within nascent waves, accumulation of active RhoA precedes that of total RhoA, and we exploit this finding to distinguish between two popular theoretical models previously used to explain propagating cortical Rho waves.
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12
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Théry M, Blanchoin L. Reconstituting the dynamic steady states of actin networks in vitro. Nat Cell Biol 2024; 26:494-497. [PMID: 38538835 DOI: 10.1038/s41556-024-01379-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/18/2024]
Affiliation(s)
- Manuel Théry
- Université Paris Sciences et Lettres, CEA, ESPCI, Institut Pierre-Gilles de Gennes, CytoMorpho Lab, Paris, France.
- Université Grenoble-Alpes, CEA, CNRS, INRA, Interdisciplinary Research Institute of Grenoble, CytoMorpho Lab, Grenoble, France.
| | - Laurent Blanchoin
- Université Paris Sciences et Lettres, CEA, ESPCI, Institut Pierre-Gilles de Gennes, CytoMorpho Lab, Paris, France.
- Université Grenoble-Alpes, CEA, CNRS, INRA, Interdisciplinary Research Institute of Grenoble, CytoMorpho Lab, Grenoble, France.
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13
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Bement WM, Goryachev AB, Miller AL, von Dassow G. Patterning of the cell cortex by Rho GTPases. Nat Rev Mol Cell Biol 2024; 25:290-308. [PMID: 38172611 DOI: 10.1038/s41580-023-00682-z] [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] [Accepted: 10/20/2023] [Indexed: 01/05/2024]
Abstract
The Rho GTPases - RHOA, RAC1 and CDC42 - are small GTP binding proteins that regulate basic biological processes such as cell locomotion, cell division and morphogenesis by promoting cytoskeleton-based changes in the cell cortex. This regulation results from active (GTP-bound) Rho GTPases stimulating target proteins that, in turn, promote actin assembly and myosin 2-based contraction to organize the cortex. This basic regulatory scheme, well supported by in vitro studies, led to the natural assumption that Rho GTPases function in vivo in an essentially linear matter, with a given process being initiated by GTPase activation and terminated by GTPase inactivation. However, a growing body of evidence based on live cell imaging, modelling and experimental manipulation indicates that Rho GTPase activation and inactivation are often tightly coupled in space and time via signalling circuits and networks based on positive and negative feedback. In this Review, we present and discuss this evidence, and we address one of the fundamental consequences of coupled activation and inactivation: the ability of the Rho GTPases to self-organize, that is, direct their own transition from states of low order to states of high order. We discuss how Rho GTPase self-organization results in the formation of diverse spatiotemporal cortical patterns such as static clusters, oscillatory pulses, travelling wave trains and ring-like waves. Finally, we discuss the advantages of Rho GTPase self-organization and pattern formation for cell function.
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Affiliation(s)
- William M Bement
- Center for Quantitative Cell Imaging, Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI, USA.
| | - Andrew B Goryachev
- Center for Engineering Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.
| | - Ann L Miller
- Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA.
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14
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Werner ME, Ray DD, Breen C, Staddon MF, Jug F, Banerjee S, Maddox AS. Mechanical positive feedback and biochemical negative feedback combine to generate complex contractile oscillations in cytokinesis. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.01.569672. [PMID: 38076901 PMCID: PMC10705528 DOI: 10.1101/2023.12.01.569672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
Contractile force generation by the cortical actomyosin cytoskeleton is essential for a multitude of biological processes. The actomyosin cortex behaves as an active material that drives local and large-scale shape changes via cytoskeletal remodeling in response to biochemical cues and feedback loops. Cytokinesis is the essential cell division event during which a cortical actomyosin ring generates contractile force to change cell shape and separate two daughter cells. Our recent work with active gel theory predicts that actomyosin systems under the control of a biochemical oscillator and experiencing mechanical strain will exhibit complex spatiotemporal behavior, but cytokinetic contractility was thought to be kinetically simple. To test whether active materials in vivo exhibit spatiotemporally complex kinetics, we used 4-dimensional imaging with unprecedented temporal resolution and discovered sections of the cytokinetic cortex undergo periodic phases of acceleration and deceleration. Quantification of ingression speed oscillations revealed wide ranges of oscillation period and amplitude. In the cytokinetic ring, activity of the master regulator RhoA pulsed with a timescale of approximately 20 seconds, shorter than that reported for any other biological context. Contractility oscillated with 20-second periodicity and with much longer periods. A combination of in vivo and in silico approaches to modify mechanical feedback revealed that the period of contractile oscillation is prolonged as a function of the intensity of mechanical feedback. Effective local ring ingression is characterized by slower speed oscillations, likely due to increased local stresses and therefore mechanical feedback. Fast ingression also occurs where material turnover is high, in vivo and in silico . We propose that downstream of initiation by pulsed RhoA activity, mechanical positive feedback, including but not limited to material advection, extends the timescale of contractility beyond that of biochemical input and therefore makes it robust to fluctuations in activation. Circumferential propagation of contractility likely allows sustained contractility despite cytoskeletal remodeling necessary to recover from compaction. Our work demonstrates that while biochemical feedback loops afford systems responsiveness and robustness, mechanical feedback must also be considered to describe and understand the behaviors of active materials in vivo .
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15
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Harrell M, Liu Z, Campbell BF, Chinsen O, Hong T, Das M. The Arp2/3 complex promotes periodic removal of Pak1-mediated negative feedback to facilitate anticorrelated Cdc42 oscillations. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.08.566261. [PMID: 38106068 PMCID: PMC10723479 DOI: 10.1101/2023.11.08.566261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
The conserved GTPase Cdc42 is a major regulator of polarized growth in most eukaryotes. Cdc42 periodically cycles between active and inactive states at sites of polarized growth. These periodic cycles are caused by positive feedback and time-delayed negative feedback loops. In the bipolar yeast S. pombe, both growing ends must regulate Cdc42 activity. At each cell end, Cdc42 activity recruits the Pak1 kinase which prevents further Cdc42 activation thus establishing negative feedback. It is unclear how Cdc42 activation returns to the end after Pak1-dependent negative feedback. Using genetic and chemical perturbations, we find that disrupting branched actin-mediated endocytosis disables Cdc42 reactivation at the cell ends. With our experimental data and mathematical models, we show that endocytosis-dependent Pak1 removal from the cell ends allows the Cdc42 activator Scd1 to return to that end to enable reactivation of Cdc42. Moreover, we show that Pak1 elicits its own removal via activation of endocytosis. In agreement with these observations, our model and experimental data show that in each oscillatory cycle, Cdc42 activation increases followed by an increase in Pak1 recruitment at that end. These findings provide a deeper insight into the self-organization of Cdc42 regulation and reveal previously unknown feedback with endocytosis in the establishment of cell polarity.
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Affiliation(s)
- Marcus Harrell
- Biology Department, Boston College, Chestnut Hill, MA, 02467
| | - Ziyi Liu
- Department of Biochemistry and Cellular & Molecular Biology, University of Tennessee, TN, 37916
| | | | - Olivia Chinsen
- Biology Department, Boston College, Chestnut Hill, MA, 02467
| | - Tian Hong
- Department of Biochemistry and Cellular & Molecular Biology, University of Tennessee, TN, 37916
| | - Maitreyi Das
- Biology Department, Boston College, Chestnut Hill, MA, 02467
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16
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Jackson JA, Denk-Lobnig M, Kitzinger KA, Martin AC. Change in RhoGAP and RhoGEF availability drives transitions in cortical patterning and excitability in Drosophila. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.11.06.565883. [PMID: 37986763 PMCID: PMC10659369 DOI: 10.1101/2023.11.06.565883] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2023]
Abstract
Actin cortex patterning and dynamics are critical for cell shape changes. These dynamics undergo transitions during development, often accompanying changes in collective cell behavior. While mechanisms have been established for individual cells' dynamic behaviors, mechanisms and specific molecules that result in developmental transitions in vivo are still poorly understood. Here, we took advantage of two developmental systems in Drosophila melanogaster to identify conditions that altered cortical patterning and dynamics. We identified a RhoGEF and RhoGAP pair whose relocalization from nucleus to cortex results in actomyosin waves in egg chambers. Furthermore, we found that overexpression of a different RhoGEF and RhoGAP pair resulted in actomyosin waves in the early embryo, during which RhoA activation precedes actomyosin assembly and RhoGAP recruitment by ~4 seconds. Overall, we showed a mechanism involved in inducing actomyosin waves that is essential for oocyte development and is general to other cell types.
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Affiliation(s)
- Jonathan A. Jackson
- Department of Biology, Massachusetts Institute of Technology
- Graduate Program in Biophysics, Harvard University
| | | | | | - Adam C. Martin
- Department of Biology, Massachusetts Institute of Technology
- Lead contact
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17
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Beta C, Edelstein-Keshet L, Gov N, Yochelis A. From actin waves to mechanism and back: How theory aids biological understanding. eLife 2023; 12:e87181. [PMID: 37428017 DOI: 10.7554/elife.87181] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2023] [Accepted: 06/01/2023] [Indexed: 07/11/2023] Open
Abstract
Actin dynamics in cell motility, division, and phagocytosis is regulated by complex factors with multiple feedback loops, often leading to emergent dynamic patterns in the form of propagating waves of actin polymerization activity that are poorly understood. Many in the actin wave community have attempted to discern the underlying mechanisms using experiments and/or mathematical models and theory. Here, we survey methods and hypotheses for actin waves based on signaling networks, mechano-chemical effects, and transport characteristics, with examples drawn from Dictyostelium discoideum, human neutrophils, Caenorhabditis elegans, and Xenopus laevis oocytes. While experimentalists focus on the details of molecular components, theorists pose a central question of universality: Are there generic, model-independent, underlying principles, or just boundless cell-specific details? We argue that mathematical methods are equally important for understanding the emergence, evolution, and persistence of actin waves and conclude with a few challenges for future studies.
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Affiliation(s)
- Carsten Beta
- Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany
| | | | - Nir Gov
- Department of Chemical and Biological Physics, Weizmann Institute of Science, Rehovot, Israel
| | - Arik Yochelis
- Swiss Institute for Dryland Environmental and Energy Research, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer Campus, Midreshet Ben-Gurion, Israel
- Department of Physics, Ben-Gurion University of the Negev, Be'er Sheva, Israel
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18
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Caballero N, Kruse K, Giamarchi T. Phase separation on surfaces in the presence of matter exchange. Phys Rev E 2023; 108:L012801. [PMID: 37583133 DOI: 10.1103/physreve.108.l012801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Accepted: 05/17/2023] [Indexed: 08/17/2023]
Abstract
We present a field theory to describe the composition of a surface spontaneously exchanging matter with its bulk environment. By only assuming matter conservation in the system, we show with extensive numerical simulations that, depending on the matter exchange rates, a complex patterned composition distribution emerges on the surface. For one-dimensional systems we show analytically and numerically that coarsening is arrested and as a consequence domains have a characteristic length scale. Our results show that the causes of heterogeneous lipid composition in cellular membranes may be justified in simple physical terms.
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Affiliation(s)
- Nirvana Caballero
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
| | - Karsten Kruse
- Department of Biochemistry, Department of Theoretical Physics, and NCCR Chemical Biology, University of Geneva, 1211 Geneva, Switzerland
| | - Thierry Giamarchi
- Department of Quantum Matter Physics, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva, Switzerland
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19
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Michaud A, Leda M, Swider ZT, Kim S, He J, Landino J, Valley JR, Huisken J, Goryachev AB, von Dassow G, Bement WM. A versatile cortical pattern-forming circuit based on Rho, F-actin, Ect2, and RGA-3/4. J Cell Biol 2022; 221:e202203017. [PMID: 35708547 PMCID: PMC9206115 DOI: 10.1083/jcb.202203017] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Revised: 05/09/2022] [Accepted: 05/30/2022] [Indexed: 01/16/2023] Open
Abstract
Many cells can generate complementary traveling waves of actin filaments (F-actin) and cytoskeletal regulators. This phenomenon, termed cortical excitability, results from coupled positive and negative feedback loops of cytoskeletal regulators. The nature of these feedback loops, however, remains poorly understood. We assessed the role of the Rho GAP RGA-3/4 in the cortical excitability that accompanies cytokinesis in both frog and starfish. RGA-3/4 localizes to the cytokinetic apparatus, "chases" Rho waves in an F-actin-dependent manner, and when coexpressed with the Rho GEF Ect2, is sufficient to convert the normally quiescent, immature Xenopus oocyte cortex into a dramatically excited state. Experiments and modeling show that changing the ratio of RGA-3/4 to Ect2 produces cortical behaviors ranging from pulses to complex waves of Rho activity. We conclude that RGA-3/4, Ect2, Rho, and F-actin form the core of a versatile circuit that drives a diverse range of cortical behaviors, and we demonstrate that the immature oocyte is a powerful model for characterizing these dynamics.
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Affiliation(s)
- Ani Michaud
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-Madison, Madison, WI
- Center for Quantitative Cell Imaging, University of Wisconsin-Madison, Madison, WI
| | - Marcin Leda
- Center for Synthetic and Systems Biology, University of Edinburgh, Edinburgh, UK
| | - Zachary T. Swider
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-Madison, Madison, WI
- Center for Quantitative Cell Imaging, University of Wisconsin-Madison, Madison, WI
| | - Songeun Kim
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-Madison, Madison, WI
- Center for Quantitative Cell Imaging, University of Wisconsin-Madison, Madison, WI
| | - Jiaye He
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI
- Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI
| | - Jennifer Landino
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan-Ann Arbor, Ann Arbor, MI
| | - Jenna R. Valley
- Oregon Institute of Marine Biology, University of Oregon, Charleston, OR
| | - Jan Huisken
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI
- Morgridge Institute for Research, University of Wisconsin-Madison, Madison, WI
| | - Andrew B. Goryachev
- Center for Synthetic and Systems Biology, University of Edinburgh, Edinburgh, UK
| | - George von Dassow
- Oregon Institute of Marine Biology, University of Oregon, Charleston, OR
| | - William M. Bement
- Center for Quantitative Cell Imaging, University of Wisconsin-Madison, Madison, WI
- Department of Integrative Biology, University of Wisconsin-Madison, Madison, WI
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20
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Swider ZT, Michaud A, Leda M, Landino J, Goryachev AB, Bement WM. Cell cycle and developmental control of cortical excitability in Xenopus laevis. Mol Biol Cell 2022; 33:ar73. [PMID: 35594176 PMCID: PMC9635278 DOI: 10.1091/mbc.e22-01-0025] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Interest in cortical excitability—the ability of the cell cortex to generate traveling waves of protein activity—has grown considerably over the past 20 years. Attributing biological functions to cortical excitability requires an understanding of the natural behavior of excitable waves and the ability to accurately quantify wave properties. Here we have investigated and quantified the onset of cortical excitability in Xenopus laevis eggs and embryos and the changes in cortical excitability throughout early development. We found that cortical excitability begins to manifest shortly after egg activation. Further, we identified a close relationship between wave properties—such as wave frequency and amplitude—and cell cycle progression as well as cell size. Finally, we identified quantitative differences between cortical excitability in the cleavage furrow relative to nonfurrow cortical excitability and showed that these wave regimes are mutually exclusive.
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Affiliation(s)
- Zachary T Swider
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-Madison Madison, WI 53706.,Center for Quantitative Cell Imaging, University of Wisconsin-Madison Madison, WI 53706
| | - Ani Michaud
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-Madison Madison, WI 53706.,Center for Quantitative Cell Imaging, University of Wisconsin-Madison Madison, WI 53706
| | - Marcin Leda
- Centre for Synthetic and Systems Biology, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - Jennifer Landino
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan-Ann Arbor, Ann Arbor, MI 48109
| | - Andrew B Goryachev
- Centre for Synthetic and Systems Biology, University of Edinburgh, Edinburgh EH9 3BF, UK
| | - William M Bement
- Cellular and Molecular Biology Graduate Program, University of Wisconsin-Madison Madison, WI 53706.,Center for Quantitative Cell Imaging, University of Wisconsin-Madison Madison, WI 53706.,Department of Integrative Biology, University of Wisconsin-Madison Madison, WI 53706
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21
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Yao B, Donoughe S, Michaux J, Munro E. Modulating RhoA effectors induces transitions to oscillatory and more wavelike RhoA dynamics in C. elegans zygotes. Mol Biol Cell 2022; 33:ar58. [PMID: 35138935 PMCID: PMC9265151 DOI: 10.1091/mbc.e21-11-0542] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Pulsatile RhoA dynamics underlie a wide range of cell and tissue behaviors. The circuits that produce these dynamics in different cells share common architectures based on fast positive and delayed negative feedback through F-actin, but they can produce very different spatiotemporal patterns of RhoA activity. However, the underlying causes of this variation remain poorly understood. Here we asked how this variation could arise through modulation of actin network dynamics downstream of active RhoA in early C. elegans embryos. We find that perturbing two RhoA effectors - formin and anillin - induce transitions from non-recurrent focal pulses to either large noisy oscillatory pulses (formin depletion) or noisy oscillatory waves (anillin depletion). In both cases these transitions could be explained by changes in local F-actin levels and depletion dynamics, leading to changes in spatial and temporal patterns of RhoA inhibition. However, the underlying mechanisms for F-actin depletion are distinct, with different dependencies on myosin II activity. Thus, modulating actomyosin network dynamics could shape the spatiotemporal dynamics of RhoA activity for different physiological or morphogenetic functions. [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text] [Media: see text].
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Affiliation(s)
- Baixue Yao
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637.,Committee on Cell Biology, University of Chicago, Chicago, IL 60637
| | - Seth Donoughe
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637.,Committee on Development, Regeneration and Stem Cell Biology, University of Chicago, Chicago, IL 60637
| | | | - Edwin Munro
- Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, IL 60637.,Committee on Cell Biology, University of Chicago, Chicago, IL 60637.,Committee on Development, Regeneration and Stem Cell Biology, University of Chicago, Chicago, IL 60637.,Institute for Biophysical Dynamics, University of Chicago, Chicago, IL 60637
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