1
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Alonso A, Kirkegaard JB, Endres RG. Persistent pseudopod splitting is an effective chemotaxis strategy in shallow gradients. Proc Natl Acad Sci U S A 2025; 122:e2502368122. [PMID: 40339116 PMCID: PMC12088397 DOI: 10.1073/pnas.2502368122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2025] [Accepted: 03/29/2025] [Indexed: 05/10/2025] Open
Abstract
Single-cell organisms and various cell types use a range of motility modes when following a chemical gradient, but it is unclear which mode is best suited for different gradients. Here, we model directional decision-making in chemotactic amoeboid cells as a stimulus-dependent actin recruitment contest. Pseudopods extending from the cell body compete for a finite actin pool to push the cell in their direction until one pseudopod wins and determines the direction of movement. Our minimal model provides a quantitative understanding of the strategies cells use to reach the physical limit of accurate chemotaxis, aligning with data without explicit gradient sensing or cellular memory for persistence. To generalize our model, we employ reinforcement learning optimization to study the effect of pseudopod suppression, a simple but effective cellular algorithm by which cells can suppress possible directions of movement. Different pseudopod-based chemotaxis strategies emerge naturally depending on the environment and its dynamics. For instance, in static gradients, cells can react faster at the cost of pseudopod accuracy, which is particularly useful in noisy, shallow gradients where it paradoxically increases chemotactic accuracy. In contrast, in dynamics gradients, cells form de novo pseudopods. Overall, our work demonstrates mechanical intelligence for high chemotaxis performance with minimal cellular regulation.
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Affiliation(s)
- Albert Alonso
- Niels Bohr Institute, University of Copenhagen, Copenhagen2100, Denmark
| | - Julius B. Kirkegaard
- Niels Bohr Institute, University of Copenhagen, Copenhagen2100, Denmark
- Department of Computer Science, University of Copenhagen, Copenhagen2100, Denmark
| | - Robert G. Endres
- Department of Life Sciences and Centre for Integrative Systems Biology and Bioinformatics, Imperial College London, LondonSW7 2AZ, United Kingdom
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2
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Alonso A, Endres RG, Kirkegaard JB. Local Clustering and Global Spreading of Receptors for Optimal Spatial Gradient Sensing. PHYSICAL REVIEW LETTERS 2025; 134:158401. [PMID: 40315515 DOI: 10.1103/physrevlett.134.158401] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2024] [Accepted: 03/11/2025] [Indexed: 05/04/2025]
Abstract
Spatial information from cell-surface receptors is crucial for processes that require signal processing and sensing of the environment. Here, we investigate the optimal placement of such receptors through a theoretical model that minimizes uncertainty in gradient estimation. Without requiring a priori knowledge of the physical limits of sensing or biochemical processes, we reproduce the emergence of clusters that closely resemble those observed in real cells. On perfect spherical surfaces, optimally placed receptors spread uniformly. When perturbations break their symmetry, receptors cluster in regions of high curvature, massively reducing estimation uncertainty. This agrees in many scenarios with mechanistic models that minimize elastic preference discrepancies between receptors and cell membranes. We further extend our model to motile receptors responding to cell-shape changes and external fluid flow, demonstrating the biological relevance of our model. Our findings provide a simple and utilitarian explanation for receptor clustering at high-curvature regions when high sensing accuracy is paramount.
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Affiliation(s)
- Albert Alonso
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
| | - Robert G Endres
- Imperial College, Department of Life Sciences and Centre for Integrative Systems Biology and Bioinformatics, London, United Kingdom
| | - Julius B Kirkegaard
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
- University of Copenhagen, Department of Computer Science, Copenhagen, Denmark
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3
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McCusker DR, Lubensky DK. Physical limits on chemical sensing in bounded domains. Phys Rev E 2025; 111:034404. [PMID: 40247576 DOI: 10.1103/physreve.111.034404] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2024] [Accepted: 02/11/2025] [Indexed: 04/19/2025]
Abstract
Cells respond to chemical signals, and the precision with which they can sense these signals is fundamentally limited by the stochastic nature of diffusion and ligand binding. Berg and Purcell famously investigated how well a small sensor in an infinite ligand bath can determine the ligand concentration, and a number of subsequent analyses have refined and built upon their classical estimates. Not all concentration-sensing problems, however, occur in such an infinite geometry. At different scales, subcellular sensors and cells in tissues are both often confronted with signals whose diffusion is affected by confining boundaries. It is thus valuable to understand how basic limits on chemosensation depend on the sensor's size and on its position in the domain in which ligand diffuses. Here we compute how sensor size and proximity to reflecting boundaries affect the diffusion-limited precision of chemosensation for various geometries in one and three dimensions. We derive analytical expressions for the sensing limit in these geometries. Among our conclusions is the surprising result that, in certain circumstances, smaller sensors can be more effective than larger sensors. This effect arises from a trade-off between spatial averaging and time averaging that we analyze in detail. We also find that proximity to confining boundaries can degrade a sensor's precision significantly compared to the precision of the same sensor far from any boundaries.
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Affiliation(s)
- Daniel R McCusker
- University of Michigan, Applied Physics Graduate Program, Ann Arbor, Michigan 48109, USA
| | - David K Lubensky
- University of Michigan, Department of Physics, Ann Arbor, Michigan 48109, USA
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4
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Giese W, Albrecht JP, Oppenheim O, Akmeriç EB, Kraxner J, Schmidt D, Harrington K, Gerhardt H. Polarity-JaM: an image analysis toolbox for cell polarity, junction and morphology quantification. Nat Commun 2025; 16:1474. [PMID: 39922822 PMCID: PMC11807127 DOI: 10.1038/s41467-025-56643-x] [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: 05/14/2024] [Accepted: 01/24/2025] [Indexed: 02/10/2025] Open
Abstract
Cell polarity involves the asymmetric distribution of cellular components such as signalling molecules and organelles within a cell, alterations in cell morphology and cell-cell contacts. Advances in fluorescence microscopy and deep learning algorithms open up a wealth of unprecedented opportunities to characterise various aspects of cell polarity, but also create new challenges for comprehensible and interpretable image data analysis workflows to fully exploit these new opportunities. Here we present Polarity-JaM, an open source package for reproducible exploratory image analysis that provides versatile methods for single cell segmentation, feature extraction and statistical analysis. We demonstrate our analysis using fluorescence image data of endothelial cells and their collective behaviour, which has been shown to be essential for vascular development and disease. The general architecture of the software allows its application to other cell types and imaging modalities, as well as seamless integration into common image analysis workflows, see https://polarityjam.readthedocs.io . We also provide a web application for circular statistics and data visualisation, available at www.polarityjam.com , and a Napari plug-in, each with a graphical user interface to facilitate exploratory analysis. We propose a holistic image analysis workflow that is accessible to the end user in bench science, enabling comprehensive analysis of image data.
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Affiliation(s)
- Wolfgang Giese
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany.
- DZHK (German Center for Cardiovascular Research), Berlin, Germany.
| | - Jan Philipp Albrecht
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- HELMHOLTZ IMAGING, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- Faculty of Mathematics and Natural Sciences, Humboldt-Universität zu Berlin, Berlin, Germany
| | - Olya Oppenheim
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- DZHK (German Center for Cardiovascular Research), Berlin, Germany
- Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Emir Bora Akmeriç
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- DZHK (German Center for Cardiovascular Research), Berlin, Germany
- Charité - Universitätsmedizin Berlin, Berlin, Germany
| | - Julia Kraxner
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- DZHK (German Center for Cardiovascular Research), Berlin, Germany
| | - Deborah Schmidt
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- HELMHOLTZ IMAGING, Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
| | - Kyle Harrington
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- Chan Zuckerberg Institute for Advanced Biological Imaging, Redwood City, CA, USA
| | - Holger Gerhardt
- Max Delbrück Center for Molecular Medicine in the Helmholtz Association, Berlin, Germany
- DZHK (German Center for Cardiovascular Research), Berlin, Germany
- Charité - Universitätsmedizin Berlin, Berlin, Germany
- Berlin Institute of Health, Berlin, Germany
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5
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Colgren J, Burkhardt P. Electrical signaling and coordinated behavior in the closest relative of animals. SCIENCE ADVANCES 2025; 11:eadr7434. [PMID: 39772683 PMCID: PMC11708886 DOI: 10.1126/sciadv.adr7434] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/15/2024] [Accepted: 12/04/2024] [Indexed: 01/11/2025]
Abstract
The transition from simple to complex multicellularity involves division of labor and specialization of cell types. In animals, complex sensory-motor systems are primarily built around specialized cells of muscles and neurons, though the evolutionary origins of these and their integration remain unclear. Here, to investigate sensory-behavior coupling in the closest relatives of animals, we established a line of the choanoflagellate, Salpingoeca rosetta, which stably expresses the calcium indicator RGECO1. Using this, we identify a previously unknown cellular behavior associated with electrical signaling, in which ciliary arrest is coupled with apical-basal contraction of the cell. This behavior and the associated calcium transients are synchronized in the multicellular state and result in coordinated ciliary arrest and colony-wide contraction, suggesting that information is spread among the cells. Our work reveals fundamental insights into how choanoflagellates sense and respond to their environment and enhances our understanding of the integration of cellular and organism-wide behavior in the closest protistan relatives of animals.
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Affiliation(s)
- Jeffrey Colgren
- Michael Sars Centre, University of Bergen, 5008 Bergen, Norway
| | - Pawel Burkhardt
- Michael Sars Centre, University of Bergen, 5008 Bergen, Norway
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6
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Nakamura K, Kobayashi TJ. Gradient sensing limit of an elongated cell with orientational control. Phys Rev E 2024; 110:064407. [PMID: 39916211 DOI: 10.1103/physreve.110.064407] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2024] [Accepted: 11/26/2024] [Indexed: 05/07/2025]
Abstract
Eukaryotic cells perform chemotaxis by determining the direction of chemical gradients based on stochastic sensing of concentrations at the cell surface. To examine the efficiency of this process, previous studies have investigated the limit of estimation accuracy for gradients. However, most studies have treated a circular cell shape, and the few considering elongated shapes assume the elongated direction as fixed. This leaves the question of how adaptive regulation of cell shape affects the estimation limit. Dynamics of cell shape during gradient sensing is biologically ubiquitous and can influence the estimation by altering the way the concentration is measured, and cells may strategically regulate their shape to improve estimation accuracy. To address this gap, we investigate the estimation limits in dynamic situations where elongated cells change their orientation adaptively depending on the sensed signal. We approach this problem by analyzing the stationary solution of the Bayesian nonlinear filtering equation. By applying diffusion approximation to the ligand-receptor binding process and the Laplace method for the posterior expectation under a high signal-to-noise ratio regime, we obtain an analytical expression for the estimation limit. This expression indicates that estimation accuracy can be improved by aligning the elongated direction perpendicular to the estimated direction, which is also confirmed by numerical simulations. Our analysis provides a basis for clarifying the interplay between estimation and control in gradient sensing and sheds light on how cells optimize their shape to enhance chemotactic efficiency.
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Affiliation(s)
- Kento Nakamura
- RIKEN Center for Brain Science, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan
| | - Tetsuya J Kobayashi
- The University of Tokyo, Institute of Industrial Science, 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505 Japan
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7
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LeFebre R, Landsittel JA, Stone DE, Mugler A. Role of Signal Degradation in Directional Chemosensing. PHYSICAL REVIEW LETTERS 2024; 133:138402. [PMID: 39392964 DOI: 10.1103/physrevlett.133.138402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2023] [Accepted: 08/23/2024] [Indexed: 10/13/2024]
Abstract
Directional chemosensing is ubiquitous in cell biology, but some cells such as mating yeast paradoxically degrade the signal they aim to detect. While the data processing inequality suggests that such signal modification cannot increase the sensory information, we show using a reaction-diffusion model and an exactly solvable discrete-state reduction that it can. We identify a non-Markovian step in the information chain allowing the system to evade the data processing inequality, reflecting the nonlocal nature of diffusion. Our results apply to any sensory system in which degradation couples to diffusion. Experimental data suggest that mating yeast operate in the beneficial regime where degradation improves sensing.
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8
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Jiang H, Wang S. Physical extraction of antigen and information. Proc Natl Acad Sci U S A 2024; 121:e2320537121. [PMID: 39302963 PMCID: PMC11441497 DOI: 10.1073/pnas.2320537121] [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: 11/21/2023] [Accepted: 07/18/2024] [Indexed: 09/22/2024] Open
Abstract
To respond and adapt, cells use surface receptors to sense environmental cues. While biochemical signal processing inside the cell is studied in depth, less is known about how physical processes during cell-cell contact impact signal acquisition. New experiments found that fast-evolving immune B cells in germinal centers (GCs) apply force to acquire antigen clusters prior to internalization, suggesting adaptive benefits of physical information extraction. We present a theory of stochastic antigen transfer and show that maximizing information gain via physical extraction can explain the dramatic phenotypic transition from naive to GC B cells-attenuated receptor signaling, enhanced force usage, and decentralized contact architecture. Our model suggests that binding-lifetime measurement and physical extraction serve as complementary modes of antigen recognition, greatly extending the dynamic range of affinity discrimination when combined. This physical-information framework further predicts that the optimal size of receptor clusters decreases as affinity improves, rationalizing the use of a multifocal synaptic pattern seen in GC B cells. By linking extraction dynamics to selection fidelity via discriminatory performance, we propose that cells may physically enhance information acquisition to sustain adaptive evolution.
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Affiliation(s)
- Hongda Jiang
- Department of Physics and Astronomy, University of California, Los Angeles, CA90095
| | - Shenshen Wang
- Department of Physics and Astronomy, University of California, Los Angeles, CA90095
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9
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Alonso A, Kirkegaard JB. Learning optimal integration of spatial and temporal information in noisy chemotaxis. PNAS NEXUS 2024; 3:pgae235. [PMID: 38952456 PMCID: PMC11216223 DOI: 10.1093/pnasnexus/pgae235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Accepted: 06/06/2024] [Indexed: 07/03/2024]
Abstract
We investigate the boundary between chemotaxis driven by spatial estimation of gradients and chemotaxis driven by temporal estimation. While it is well known that spatial chemotaxis becomes disadvantageous for small organisms at high noise levels, it is unclear whether there is a discontinuous switch of optimal strategies or a continuous transition exists. Here, we employ deep reinforcement learning to study the possible integration of spatial and temporal information in an a priori unconstrained manner. We parameterize such a combined chemotactic policy by a recurrent neural network and evaluate it using a minimal theoretical model of a chemotactic cell. By comparing with constrained variants of the policy, we show that it converges to purely temporal and spatial strategies at small and large cell sizes, respectively. We find that the transition between the regimes is continuous, with the combined strategy outperforming in the transition region both the constrained variants as well as models that explicitly integrate spatial and temporal information. Finally, by utilizing the attribution method of integrated gradients, we show that the policy relies on a nontrivial combination of spatially and temporally derived gradient information in a ratio that varies dynamically during the chemotactic trajectories.
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Affiliation(s)
- Albert Alonso
- Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
| | - Julius B Kirkegaard
- Niels Bohr Institute, University of Copenhagen, Copenhagen 2100, Denmark
- Department of Computer Science, University of Copenhagen, Copenhagen 2100, Denmark
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10
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Knight J, García-Galindo P, Pausch J, Pruessner G. Memoryless chemotaxis with discrete cues. J R Soc Interface 2024; 21:20240100. [PMID: 39081250 PMCID: PMC11289677 DOI: 10.1098/rsif.2024.0100] [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: 02/09/2024] [Revised: 05/06/2024] [Accepted: 06/24/2024] [Indexed: 08/02/2024] Open
Abstract
Biological systems such as axonal growth cones perform chemotaxis at micrometre-level length scales, where chemotactic molecules are sparse. Such systems lie outside the range of validity of existing models, which assume smoothly varying chemical gradients. We investigate the effect of introducing discrete chemoattractant molecules by constructing a minimal dynamical model consisting of a chemotactic cell without internal memory. Significant differences are found in the behaviour of the cell as the chemical gradient is changed from smoothly varying to discrete, including the emergence of a homing radius beyond which chemotaxis is not reliably performed.
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Affiliation(s)
- Jacob Knight
- Department of Mathematics, Imperial College London, South Kensington, LondonSW7 2BZ, UK
| | - Paula García-Galindo
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Philippa Fawcett Drive, CambridgeCB3 0AS, UK
| | - Johannes Pausch
- Department of Mathematics, Imperial College London, South Kensington, LondonSW7 2BZ, UK
| | - Gunnar Pruessner
- Department of Mathematics, Imperial College London, South Kensington, LondonSW7 2BZ, UK
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11
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Wan KY. Active oscillations in microscale navigation. Anim Cogn 2023; 26:1837-1850. [PMID: 37665482 PMCID: PMC10769930 DOI: 10.1007/s10071-023-01819-5] [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: 05/22/2023] [Revised: 07/27/2023] [Accepted: 08/12/2023] [Indexed: 09/05/2023]
Abstract
Living organisms routinely navigate their surroundings in search of better conditions, more food, or to avoid predators. Typically, animals do so by integrating sensory cues from the environment with their locomotor apparatuses. For single cells or small organisms that possess motility, fundamental physical constraints imposed by their small size have led to alternative navigation strategies that are specific to the microscopic world. Intriguingly, underlying these myriad exploratory behaviours or sensory functions is the onset of periodic activity at multiple scales, such as the undulations of cilia and flagella, the vibrations of hair cells, or the oscillatory shape modes of migrating neutrophils. Here, I explore oscillatory dynamics in basal microeukaryotes and hypothesize that these active oscillations play a critical role in enhancing the fidelity of adaptive sensorimotor integration.
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Affiliation(s)
- Kirsty Y Wan
- Living Systems Institute, University of Exeter, Stocker Road, Exeter, EX4 4QD, UK.
- Department of Mathematics and Statistics, University of Exeter, Stocker Road, Exeter, EX4 4QL, UK.
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12
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González L, Mugler A. Collective effects in flow-driven cell migration. Phys Rev E 2023; 108:054406. [PMID: 38115469 DOI: 10.1103/physreve.108.054406] [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: 05/05/2023] [Accepted: 10/17/2023] [Indexed: 12/21/2023]
Abstract
Autologous chemotaxis is the process in which cells secrete and detect molecules to determine the direction of fluid flow. Experiments and theory suggest that autologous chemotaxis fails at high cell densities because molecules from other cells interfere with a given cell's signal. We investigate autologous chemotaxis using a three-dimensional Monte Carlo-based motility simulation that couples spatial and temporal gradient sensing with cell-cell repulsion. Surprisingly, we find that when temporal gradient sensing dominates, high-density clusters chemotax faster than individual cells. To explain this observation, we propose a mechanism by which temporal gradient sensing allows cells to form a collective sensory unit. We demonstrate using computational fluid mechanics that that this mechanism indeed allows a cluster of cells to outperform single cells in terms of the detected anisotropy of the signal, a finding that we demonstrate with analytic scaling arguments. Our work suggests that collective autologous chemotaxis at high cell densities is possible and requires only known, ubiquitous cell capabilities.
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Affiliation(s)
- Louis González
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - Andrew Mugler
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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13
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Alanko J, Uçar MC, Canigova N, Stopp J, Schwarz J, Merrin J, Hannezo E, Sixt M. CCR7 acts as both a sensor and a sink for CCL19 to coordinate collective leukocyte migration. Sci Immunol 2023; 8:eadc9584. [PMID: 37656776 DOI: 10.1126/sciimmunol.adc9584] [Citation(s) in RCA: 20] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 08/09/2023] [Indexed: 09/03/2023]
Abstract
Immune responses rely on the rapid and coordinated migration of leukocytes. Whereas it is well established that single-cell migration is often guided by gradients of chemokines and other chemoattractants, it remains poorly understood how these gradients are generated, maintained, and modulated. By combining experimental data with theory on leukocyte chemotaxis guided by the G protein-coupled receptor (GPCR) CCR7, we demonstrate that in addition to its role as the sensory receptor that steers migration, CCR7 also acts as a generator and a modulator of chemotactic gradients. Upon exposure to the CCR7 ligand CCL19, dendritic cells (DCs) effectively internalize the receptor and ligand as part of the canonical GPCR desensitization response. We show that CCR7 internalization also acts as an effective sink for the chemoattractant, dynamically shaping the spatiotemporal distribution of the chemokine. This mechanism drives complex collective migration patterns, enabling DCs to create or sharpen chemotactic gradients. We further show that these self-generated gradients can sustain the long-range guidance of DCs, adapt collective migration patterns to the size and geometry of the environment, and provide a guidance cue for other comigrating cells. Such a dual role of CCR7 as a GPCR that both senses and consumes its ligand can thus provide a novel mode of cellular self-organization.
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Affiliation(s)
- Jonna Alanko
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
- MediCity and InFLAMES Research Flagship Center, University of Turku, Turku, Finland
| | - Mehmet Can Uçar
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Nikola Canigova
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Julian Stopp
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Jan Schwarz
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
- Ibidi GmbH, Gräfelfing, Germany
| | - Jack Merrin
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Edouard Hannezo
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
| | - Michael Sixt
- Institute of Science and Technology Austria (ISTA), Klosterneuburg, Austria
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14
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Bernoff AJ, Jilkine A, Navarro Hernández A, Lindsay AE. Single-cell directional sensing from just a few receptor binding events. Biophys J 2023; 122:3108-3116. [PMID: 37355773 PMCID: PMC10432224 DOI: 10.1016/j.bpj.2023.06.015] [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: 04/11/2023] [Revised: 06/08/2023] [Accepted: 06/20/2023] [Indexed: 06/26/2023] Open
Abstract
Identifying the directionality of signaling sources from noisy input to membrane receptors is an essential task performed by many cell types. A variety of models have been proposed to explain directional sensing in cells. However, many of these require significant computational and memory capacities for the cell. We propose and analyze a simple mechanism in which a cell adopts the direction associated with the first few membrane binding events. This model yields an accurate angular estimate to the source long before steady state is reached in biologically relevant scenarios. Our proposed mechanism allows for reliable estimates of the directionality of external signals using temporal information and assumes minimal computational capacities of the cell.
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Affiliation(s)
- Andrew J Bernoff
- Department of Mathematics, Harvey Mudd College, Claremont, California
| | - Alexandra Jilkine
- Department of Applied & Computational Mathematics & Statistics, University of Notre Dame, South Bend, Indiana
| | - Adrián Navarro Hernández
- Department of Applied & Computational Mathematics & Statistics, University of Notre Dame, South Bend, Indiana
| | - Alan E Lindsay
- Department of Applied & Computational Mathematics & Statistics, University of Notre Dame, South Bend, Indiana.
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15
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Biswal S, Wasnik V. Accuracy in readout of glutamate concentrations by neuronal cells. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2023; 46:30. [PMID: 37076657 DOI: 10.1140/epje/s10189-023-00287-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Accepted: 03/28/2023] [Indexed: 05/03/2023]
Abstract
Glutamate and glycine are important neurotransmitters in the brain. An action potential propagating in the terminal of a presynaptic neuron causes the release of glutamate and glycine in the synapse by vesicles fusing with the cell membrane, which then activate various receptors on the cell membrane of the post-synaptic neuron. Entry of Ca[Formula: see text] through the activated NMDA receptors leads to a host of cellular processes of which long-term potentiation is of crucial importance because it is widely considered to be one of the major mechanisms behind learning and memory. By analysing the readout of glutamate concentration by the post-synaptic neurons during Ca[Formula: see text] signaling, we find that the average receptor density in hippocampal neurons has evolved to allow for accurate measurement of the glutamate concentration in the synaptic cleft.
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Affiliation(s)
- Swoyam Biswal
- Indian Institute of Technology Goa At Goa College of Engineering Campus, Farmagudi, Ponda-403401, Goa, India
| | - Vaibhav Wasnik
- Indian Institute of Technology Goa At Goa College of Engineering Campus, Farmagudi, Ponda-403401, Goa, India.
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16
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Lindsay AE, Bernoff AJ, Navarro Hernández A. Short-time diffusive fluxes over membrane receptors yields the direction of a signalling source. ROYAL SOCIETY OPEN SCIENCE 2023; 10:221619. [PMID: 37122946 PMCID: PMC10130716 DOI: 10.1098/rsos.221619] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/19/2022] [Accepted: 03/31/2023] [Indexed: 05/03/2023]
Abstract
An essential ability of many cell types is to detect stimuli in the form of shallow chemical gradients. Such cues may indicate the direction that new growth should occur, or the location of a mate. Amplification of these faint signals is due to intra-cellular mechanisms, while the cue itself is generated by the noisy arrival of signalling molecules to surface bound membrane receptors. We employ a new hybrid numerical-asymptotic technique coupling matched asymptotic analysis and numerical inverse Laplace transform to rapidly and accurately solve the parabolic exterior problem describing the dynamic diffusive fluxes to receptors. We observe that equilibration occurs on long timescales, potentially limiting the usefulness of steady-state quantities for localization at practical biological timescales. We demonstrate that directional information is encoded primarily in early arrivals to the receptors, while equilibrium quantities inform on source distance. We develop a new homogenization result showing that complex receptor configurations can be replaced by a uniform effective condition. In the extreme scenario where the cell adopts the angular direction of the first impact, we show this estimate to be surprisingly accurate.
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Affiliation(s)
- Alan E. Lindsay
- Department of Applied and Computational Math and Statistics, University of Notre Dame, Notre Dame, IN 46617, USA
| | - Andrew J. Bernoff
- Department of Mathematics, Harvey Mudd College, Claremont, CA 91711, USA
| | - Adrián Navarro Hernández
- Department of Applied and Computational Math and Statistics, University of Notre Dame, Notre Dame, IN 46617, USA
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17
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Jiang H, Wang S. Immune cells use active tugging forces to distinguish affinity and accelerate evolution. Proc Natl Acad Sci U S A 2023; 120:e2213067120. [PMID: 36897986 PMCID: PMC10089171 DOI: 10.1073/pnas.2213067120] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Accepted: 01/11/2023] [Indexed: 03/12/2023] Open
Abstract
Cells are known to exert forces to sense their physical surroundings for guidance of motion and fate decisions. Here, we propose that cells might do mechanical work to drive their own evolution, taking inspiration from the adaptive immune system. Growing evidence indicates that immune B cells-capable of rapid Darwinian evolution-use cytoskeletal forces to actively extract antigens from other cells' surfaces. To elucidate the evolutionary significance of force usage, we develop a theory of tug-of-war antigen extraction that maps receptor binding characteristics to clonal reproductive fitness, revealing physical determinants of selection strength. This framework unifies mechanosensing and affinity-discrimination capabilities of evolving cells: Pulling against stiff antigen tethers enhances discrimination stringency at the expense of absolute extraction. As a consequence, active force usage can accelerate adaptation but may also cause extinction of cell populations, resulting in an optimal range of pulling strength that matches molecular rupture forces observed in cells. Our work suggests that nonequilibrium, physical extraction of environmental signals can make biological systems more evolvable at a moderate energy cost.
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Affiliation(s)
- Hongda Jiang
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA90095
| | - Shenshen Wang
- Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA90095
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18
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Luthra M, Todd PM. Social Search and Resource Clustering as Emergent Stable States. ARTIFICIAL LIFE 2023; 29:118-140. [PMID: 36264224 DOI: 10.1162/artl_a_00391] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Social search has stably evolved across various species and is often used by humans to search for resources (such as food, information, social partners). In turn, these resources frequently come distributed in patches or clusters. In the current work, we use an ecologically inspired agent-based model to investigate whether social search and clustering are stable outcomes of the dynamical mutual interactions between the two. While previous research has studied unidirectional influences of social search on resource clustering and vice versa, the current work investigates the consequential patterns emerging from their two-way interactions over time. In our model, consumers evolved search strategies (ranging from competitive to social) as adaptations to their environmental resource structures, and resources varied in distributions (ranging from random to clustered) that were shaped by agents' consumption patterns. Across four experiments, we systematically analyzed the patterns of influence that search strategies and environment structure have on each other to identify stable attractor states of both. In Experiment 1, we fixed resource clustering at various levels and observed its influence on social search, and in Experiment 2, we observed the influence of social search on resource distribution. In both these experiments we found that increasing levels of one variable produced increases in the other; however, at very high levels of the manipulated variable, the dependent variable tended to fall. Finally in Experiments 3 and 4, we studied the dynamics that arose when resource clustering and social search could both change and mutually influence each other, finding that low levels of social search and clustering were stable attractor states. Our simple 2D model yielded results that qualitatively resemble those across a wide range of search domains (from physical search for food to abstract search for information), highlighting some stable outcomes of mutually interacting consumer/resource systems.
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Affiliation(s)
- Mahi Luthra
- Indiana University Bloomington, Cognitive Science Program, Department of Psychological and Brain Sciences.
| | - Peter M Todd
- Indiana University Bloomington, Cognitive Science Program, Department of Psychological and Brain Sciences
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19
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Dobramysl U, Holcman D. Computational methods and diffusion theory in triangulation sensing to model neuronal navigation. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2022; 85:104601. [PMID: 36075196 DOI: 10.1088/1361-6633/ac906b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Accepted: 09/08/2022] [Indexed: 06/15/2023]
Abstract
Computational methods are now recognized as powerful and complementary approaches in various applied sciences such as biology. These computing methods are used to explore the gap between scales such as the one between molecular and cellular. Here we present recent progress in the development of computational approaches involving diffusion modeling, asymptotic analysis of the model partial differential equations, hybrid methods and simulations in the generic context of cell sensing and guidance via external gradients. Specifically, we highlight the reconstruction of the location of a point source in two and three dimensions from the steady-state diffusion fluxes arriving to narrow windows located on the cell. We discuss cases in which these windows are located on the boundary of a two-dimensional plane or three-dimensional half-space, on a disk in free space or inside a two-dimensional corridor, or a ball in three dimensions. The basis of this computational approach is explicit solutions of the Neumann-Green's function for the mentioned geometry. This analysis can be used to design hybrid simulations where Brownian paths are generated only in small regions in which the local spatial organization is relevant. Particle trajectories outside of this region are only implicitly treated by generating exit points at the boundary of this domain of interest. This greatly accelerates the simulation time by avoiding the explicit computation of Brownian paths in an infinite domain and serves to generate statistics, without following all trajectories at the same time, a process that can become numerically expensive quickly. Moreover, these computational approaches are used to reconstruct a point source and estimating the uncertainty in the source reconstruction due to an additive noise perturbation present in the fluxes. We also discuss the influence of various window configurations (cluster vs uniform distributions) on recovering the source position. Finally, the applications in developmental biology are formulated into computational principles that could underly neuronal navigation in the brain.
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Affiliation(s)
- Ulrich Dobramysl
- Peter Medawar Building for Pathogen Research, University of Oxford, Oxford, United Kingdom
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge, United Kingdom
| | - David Holcman
- Group of Data Modeling and Computational Biology, IBENS-PSL Ecole Normale Superieure, Paris, France
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20
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Vennettilli M, González L, Hilgert N, Mugler A. Autologous chemotaxis at high cell density. Phys Rev E 2022; 106:024413. [PMID: 36109906 DOI: 10.1103/physreve.106.024413] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 06/24/2022] [Indexed: 06/15/2023]
Abstract
Autologous chemotaxis, in which cells secrete and detect molecules to determine the direction of fluid flow, is thwarted at high cell density because molecules from other cells interfere with a given cell's signal. Using a minimal model of autologous chemotaxis, we determine the cell density at which sensing fails, and we find that it agrees with experimental observations of metastatic cancer cells. To understand this agreement, we derive a physical limit to autologous chemotaxis in terms of the cell density, the Péclet number, and the lengthscales of the cell and its environment. Surprisingly, in an environment that is uniformly oversaturated in the signaling molecule, we find that not only can sensing fail, but it can be reversed, causing backwards cell motion. Our results get to the heart of the competition between chemical and mechanical cellular sensing, and they shed light on a sensory strategy employed by cancer cells in dense tumor environments.
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Affiliation(s)
- Michael Vennettilli
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
| | - Louis González
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - Nicholas Hilgert
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
| | - Andrew Mugler
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
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21
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Wang ZJ, Thomson M. Localization of signaling receptors maximizes cellular information acquisition in spatially structured natural environments. Cell Syst 2022; 13:530-546.e12. [PMID: 35679857 DOI: 10.1016/j.cels.2022.05.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2021] [Revised: 02/08/2022] [Accepted: 05/12/2022] [Indexed: 01/25/2023]
Abstract
Cells in natural environments, such as tissue or soil, sense and respond to extracellular ligands with intricately structured and non-monotonic spatial distributions, sculpted by processes such as fluid flow and substrate adhesion. In this work, we show that spatial sensing and navigation can be optimized by adapting the spatial organization of signaling pathways to the spatial structure of the environment. We develop an information-theoretic framework for computing the optimal spatial organization of a sensing system for a given signaling environment. We find that receptor localization previously observed in cells maximizes information acquisition in simulated natural contexts, including tissue and soil. Specifically, information acquisition is maximized when receptors form localized patches at regions of maximal ligand concentration. Receptor localization extends naturally to produce a dynamic protocol for continuously redistributing signaling receptors, which when implemented using simple feedback, boosts cell navigation efficiency by 30-fold.
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Affiliation(s)
- Zitong Jerry Wang
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
| | - Matt Thomson
- Division of Biology and Biological Engineering, California Institute of Technology, Pasadena, CA 91125, USA.
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22
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Wasnik V. Limitations on concentration measurements and gradient discerning times in cellular systems. Phys Rev E 2022; 105:034410. [PMID: 35428148 DOI: 10.1103/physreve.105.034410] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2021] [Accepted: 02/28/2022] [Indexed: 06/14/2023]
Abstract
This work reports on two results. At first we revisit the Berg and Purcell calculation that provides a lower bound to the error in concentration measurement by cells by considering the realistic case when the cell starts measuring the moment it comes in contact with the chemoattractants, instead of measuring after equilibrating with the chemotactic concentration as done in the classic Berg and Purcell paper. We find that the error in concentration measurement is still the same as evaluated by Berg and Purcell. We next derive a lower bound on measurement time below which it is not possible for the cell to discern extracellular chemotactic gradients through spatial sensing mechanisms. This bound is independent of diffusion rate and concentration of the chemoattracts and is instead set by detachment rate of ligands from the cell receptors. The result could help explain experimental observations.
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Affiliation(s)
- Vaibhav Wasnik
- Department of Physical Sciences, Indian Institute of Technology Goa, Ponda 403401, Goa, India
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23
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Abstract
Accurate decoding of spatial chemical landscapes is critical for many cell functions. Eukaryotic cells decode local chemical gradients to orient growth or movement in productive directions. Recent work on yeast model systems, whose gradient sensing pathways display much less complexity than those in animal cells, has suggested new paradigms for how these very small cells successfully exploit information in noisy and dynamic pheromone gradients to identify their mates. Pheromone receptors regulate a polarity circuit centered on the conserved Rho-family GTPase, Cdc42. The polarity circuit contains both positive and negative feedback pathways, allowing spontaneous symmetry breaking and also polarity site disassembly and relocation. Cdc42 orients the actin cytoskeleton, leading to focused vesicle traffic that promotes movement of the polarity site and also reshapes the cortical distribution of receptors at the cell surface. In this article, we review the advances from work on yeasts and compare them with the excitable signaling pathways that have been revealed in chemotactic animal cells. Expected final online publication date for the Annual Review of Biophysics, Volume 51 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Debraj Ghose
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, USA;
| | - Timothy Elston
- Department of Pharmacology, University of North Carolina at Chapel Hill, North Carolina, USA
| | - Daniel Lew
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, USA;
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24
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Moon HR, Saha S, Mugler A, Han B. Signal processing capacity of the cellular sensory machinery regulates the accuracy of chemotaxis under complex cues. iScience 2021; 24:103242. [PMID: 34746705 PMCID: PMC8554535 DOI: 10.1016/j.isci.2021.103242] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 09/16/2021] [Accepted: 10/05/2021] [Indexed: 10/29/2022] Open
Abstract
Chemotaxis is ubiquitous in many biological processes, but it still remains elusive how cells sense and decipher multiple chemical cues. In this study, we postulate a hypothesis that the chemotactic performance of cells under complex cues is regulated by the signal processing capacity of the cellular sensory machinery. The underlying rationale is that cells in vivo should be able to sense and process multiple chemical cues, whose magnitude and compositions are entangled, to determine their migration direction. We experimentally show that the combination of transforming growth factor-β and epidermal growth factor suppresses the chemotactic performance of cancer cells using independent receptors to sense the two cues. Based on this observation, we develop a biophysical framework suggesting that the antagonism is caused by the saturation of the signal processing capacity but not by the mutual repression. Our framework suggests the significance of the signal processing capacity in the cellular sensory machinery.
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Affiliation(s)
- Hye-ran Moon
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907, USA
| | - Soutick Saha
- Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA
| | - Andrew Mugler
- Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA
- Purdue Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA
- Department of Physics and Astronomy, University of Pittsburgh, 3941 O'Hara St, Pittsburgh, PA 15260, USA
| | - Bumsoo Han
- School of Mechanical Engineering, Purdue University, 585 Purdue Mall, West Lafayette, IN 47907, USA
- Purdue Center for Cancer Research, Purdue University, West Lafayette, IN 47907, USA
- Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA
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25
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Dobramysl U, Holcman D. Reconstructing a point source from diffusion fluxes to narrow windows in three dimensions. Proc Math Phys Eng Sci 2021. [DOI: 10.1098/rspa.2021.0271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We develop a computational approach to locate the source of a steady-state gradient of diffusing particles from the fluxes through narrow windows distributed either on the boundary of a three-dimensional half-space or on a sphere. This approach is based on solving the mixed boundary stationary diffusion equation with Neumann–Green’s function. The method of matched asymptotic expansions enables the computation of the probability fluxes. To explore the range of validity of this expansion, we develop a fast analytical-Brownian numerical scheme. This scheme accelerates the simulation time by avoiding the explicit computation of Brownian trajectories in the infinite domain. The results obtained from our derived analytical formulae and the fast numerical simulation scheme agree on a large range of parameters. Using the analytical representation of the particle fluxes, we show how to reconstruct the location of the point source. Furthermore, we investigate the uncertainty in the source reconstruction due to additive fluctuations present in the fluxes. We also study the influence of various window configurations: clustered versus uniform distributions on recovering the source position. Finally, we discuss possible applications for cell navigation in biology.
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Affiliation(s)
- U. Dobramysl
- Wellcome Trust / Cancer Research UK Gurdon Institute, University of Cambridge, Cambridge, UK
| | - D. Holcman
- Group of Applied Mathematics, data modeling and computational biology, IBENS-PSL Ecole Normale Superieure, Paris, France
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26
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Vennettilli M, Saha S, Roy U, Mugler A. Precision of Protein Thermometry. PHYSICAL REVIEW LETTERS 2021; 127:098102. [PMID: 34506193 DOI: 10.1103/physrevlett.127.098102] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2020] [Accepted: 08/06/2021] [Indexed: 05/23/2023]
Abstract
Temperature sensing is a ubiquitous cell behavior, but the fundamental limits to the precision of temperature sensing are poorly understood. Unlike in chemical concentration sensing, the precision of temperature sensing is not limited by extrinsic fluctuations in the temperature field itself. Instead, we find that precision is limited by the intrinsic copy number, turnover, and binding kinetics of temperature-sensitive proteins. Developing a model based on the canonical TlpA protein, we find that a cell can estimate temperature to within 2%. We compare this prediction with in vivo data on temperature sensing in bacteria.
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Affiliation(s)
- Michael Vennettilli
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
| | - Soutick Saha
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
| | - Ushasi Roy
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Centre for BioSystems Science and Engineering, Indian Institute of Science, Bangalore 560012, India
| | - Andrew Mugler
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
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27
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van Gestel J, Bareia T, Tenennbaum B, Dal Co A, Guler P, Aframian N, Puyesky S, Grinberg I, D’Souza GG, Erez Z, Ackermann M, Eldar A. Short-range quorum sensing controls horizontal gene transfer at micron scale in bacterial communities. Nat Commun 2021; 12:2324. [PMID: 33875666 PMCID: PMC8055654 DOI: 10.1038/s41467-021-22649-4] [Citation(s) in RCA: 54] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2020] [Accepted: 03/17/2021] [Indexed: 02/02/2023] Open
Abstract
In bacterial communities, cells often communicate by the release and detection of small diffusible molecules, a process termed quorum-sensing. Signal molecules are thought to broadly diffuse in space; however, they often regulate traits such as conjugative transfer that strictly depend on the local community composition. This raises the question how nearby cells within the community can be detected. Here, we compare the range of communication of different quorum-sensing systems. While some systems support long-range communication, we show that others support a form of highly localized communication. In these systems, signal molecules propagate no more than a few microns away from signaling cells, due to the irreversible uptake of the signal molecules from the environment. This enables cells to accurately detect micron scale changes in the community composition. Several mobile genetic elements, including conjugative elements and phages, employ short-range communication to assess the fraction of susceptible host cells in their vicinity and adaptively trigger horizontal gene transfer in response. Our results underscore the complex spatial biology of bacteria, which can communicate and interact at widely different spatial scales.
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Affiliation(s)
- Jordi van Gestel
- grid.5801.c0000 0001 2156 2780Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland ,grid.418656.80000 0001 1551 0562Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, Switzerland ,grid.7400.30000 0004 1937 0650Department of Evolutionary Biology and Environmental Studies, University of Zürich, Zürich, Switzerland ,grid.419765.80000 0001 2223 3006Swiss Institute of Bioinformatics, Lausanne, Switzerland ,grid.266102.10000 0001 2297 6811Present Address: Department of Microbiology and Immunology, University of California, San Francisco, San Francisco, CA USA
| | - Tasneem Bareia
- grid.12136.370000 0004 1937 0546The Shmunis School of Biomedicine and Cancer Research, Tel-Aviv University, Tel-Aviv, Israel
| | - Bar Tenennbaum
- grid.12136.370000 0004 1937 0546The Shmunis School of Biomedicine and Cancer Research, Tel-Aviv University, Tel-Aviv, Israel
| | - Alma Dal Co
- grid.5801.c0000 0001 2156 2780Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland ,grid.418656.80000 0001 1551 0562Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, Switzerland ,grid.38142.3c000000041936754XSchool of Engineering and Applied Sciences, Harvard University, Cambridge, MA USA
| | - Polina Guler
- grid.12136.370000 0004 1937 0546The Shmunis School of Biomedicine and Cancer Research, Tel-Aviv University, Tel-Aviv, Israel
| | - Nitzan Aframian
- grid.12136.370000 0004 1937 0546The Shmunis School of Biomedicine and Cancer Research, Tel-Aviv University, Tel-Aviv, Israel
| | - Shani Puyesky
- grid.12136.370000 0004 1937 0546The Shmunis School of Biomedicine and Cancer Research, Tel-Aviv University, Tel-Aviv, Israel
| | - Ilana Grinberg
- grid.12136.370000 0004 1937 0546The Shmunis School of Biomedicine and Cancer Research, Tel-Aviv University, Tel-Aviv, Israel
| | - Glen G. D’Souza
- grid.5801.c0000 0001 2156 2780Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland ,grid.418656.80000 0001 1551 0562Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
| | - Zohar Erez
- grid.13992.300000 0004 0604 7563Department of Molecular Genetics, Weizmann Institute of Science, Rehovot, Israel
| | - Martin Ackermann
- grid.5801.c0000 0001 2156 2780Department of Environmental Systems Science, ETH Zürich, Zürich, Switzerland ,grid.418656.80000 0001 1551 0562Department of Environmental Microbiology, Swiss Federal Institute of Aquatic Science and Technology (Eawag), Dübendorf, Switzerland
| | - Avigdor Eldar
- grid.12136.370000 0004 1937 0546The Shmunis School of Biomedicine and Cancer Research, Tel-Aviv University, Tel-Aviv, Israel
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28
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Nakamura K, Kobayashi TJ. Connection between the Bacterial Chemotactic Network and Optimal Filtering. PHYSICAL REVIEW LETTERS 2021; 126:128102. [PMID: 33834835 DOI: 10.1103/physrevlett.126.128102] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 02/12/2021] [Indexed: 06/12/2023]
Abstract
The chemotactic network of Escherichia coli has been studied extensively both biophysically and information theoretically. Nevertheless, connection between these two aspects is still elusive. In this work, we report such a connection. We derive an optimal filtering dynamics under the assumption that E. coli's sensory system optimally infers the binary information whether it is swimming up or down along an exponential ligand gradient from noisy sensory signals. Then we show that a standard biochemical model of the chemotactic network is mathematically equivalent to this information-theoretically optimal dynamics. Moreover, we demonstrate that an experimentally observed nonlinear response relation can be reproduced from the optimal dynamics. These results suggest that the biochemical network of E. coli chemotaxis is designed to optimally extract the binary information along an exponential gradient in a noisy condition.
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Affiliation(s)
- Kento Nakamura
- Department of Mathematical Informatics, Graduate School of Information Science and Technology, The University of Tokyo, Tokyo 113-8654, Japan
| | - Tetsuya J Kobayashi
- Department of Mathematical Informatics, Graduate School of Information Science and Technology, The University of Tokyo, Tokyo 113-8654, Japan
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29
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Wasnik V. Average search time bounds in cue-based searches. Phys Rev E 2021; 103:022124. [PMID: 33736104 DOI: 10.1103/physreve.103.022124] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 02/02/2021] [Indexed: 11/07/2022]
Abstract
In this work we consider search problems that evaluate the probability distribution of finding the source at each step in the search. We start with a sample strategy where the movement at each time step is in the immediate neighborhood. The jump probability is taken to be proportional to the normalized difference between the probability of finding the source at the jump location with the probability of finding the source at the present location. We evaluate a lower bound on the average search time for a searcher using this strategy. We next consider the problem of evaluating the lower bound on the search time for a generic strategy which would utilize the source probability distribution to figure out the position of the source. We derive an expression for the lower bound on the search time. We present an analytic expression for this lower bound in a case in which the particles emitted by the source diffuse in a homogeneous manner. For a general probability distribution with entropy E, we find that the lower bound goes as e^{E/2}.
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Affiliation(s)
- Vaibhav Wasnik
- Indian Institute of Technology Goa, Ponda 403401, Goa, India
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30
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Abstract
All living cells interact dynamically with a constantly changing world. Eukaryotes, in particular, evolved radically new ways to sense and react to their environment. These advances enabled new and more complex forms of cellular behaviour in eukaryotes, including directional movement, active feeding, mating, and responses to predation. But what are the key events and innovations during eukaryogenesis that made all of this possible? Here we describe the ancestral repertoire of eukaryotic excitability and discuss five major cellular innovations that enabled its evolutionary origin. The innovations include a vastly expanded repertoire of ion channels, the emergence of cilia and pseudopodia, endomembranes as intracellular capacitors, a flexible plasma membrane and the relocation of chemiosmotic ATP synthesis to mitochondria, which liberated the plasma membrane for more complex electrical signalling involved in sensing and reacting. We conjecture that together with an increase in cell size, these new forms of excitability greatly amplified the degrees of freedom associated with cellular responses, allowing eukaryotes to vastly outperform prokaryotes in terms of both speed and accuracy. This comprehensive new perspective on the evolution of excitability enriches our view of eukaryogenesis and emphasizes behaviour and sensing as major contributors to the success of eukaryotes. This article is part of the theme issue 'Basal cognition: conceptual tools and the view from the single cell'.
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Affiliation(s)
- Kirsty Y. Wan
- Living Systems Institute, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
| | - Gáspár Jékely
- Living Systems Institute, University of Exeter, Stocker Road, Exeter EX4 4QD, UK
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31
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Dubois C, Gupta S, Mugler A, Félix MA. Temporally regulated cell migration is sensitive to variation in body size. Development 2021; 148:dev196949. [PMID: 33593818 PMCID: PMC10683003 DOI: 10.1242/dev.196949] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 01/14/2021] [Indexed: 12/15/2022]
Abstract
Few studies have measured the robustness to perturbations of the final position of a long-range migrating cell. In the nematode Caenorhabditis elegans, the QR neuroblast migrates anteriorly, while undergoing three division rounds. We study the final position of two of its great-granddaughters, the end of migration of which was previously shown to depend on a timing mechanism. We find that the variance in their final position is similar to that of other long-range migrating neurons. As expected from the timing mechanism, the position of QR descendants depends on body size, which we varied by changing maternal age or using body size mutants. Using a mathematical model, we show that body size variation is partially compensated for. Applying environmental perturbations, we find that the variance in final position increased following starvation at hatching. The mean position is displaced upon a temperature shift. Finally, highly significant variation was found among C. elegans wild isolates. Overall, this study reveals that the final position of these neurons is quite robust to stochastic variation, shows some sensitivity to body size and to external perturbations, and varies in the species.This article has an associated 'The people behind the papers' interview.
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Affiliation(s)
- Clément Dubois
- Institut de Biologie de l'Ecole Normale Supérieure, CNRS, Inserm, 75005 Paris, France
| | - Shivam Gupta
- Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA
| | - Andrew Mugler
- Department of Physics and Astronomy, Purdue University, West Lafayette, IN 47907, USA
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260, USA
| | - Marie-Anne Félix
- Institut de Biologie de l'Ecole Normale Supérieure, CNRS, Inserm, 75005 Paris, France
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32
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Moran JL, Wheat PM, Marine NA, Posner JD. Chemokinesis-driven accumulation of active colloids in low-mobility regions of fuel gradients. Sci Rep 2021; 11:4785. [PMID: 33637781 PMCID: PMC7910604 DOI: 10.1038/s41598-021-83963-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Accepted: 02/02/2021] [Indexed: 12/31/2022] Open
Abstract
Many motile cells exhibit migratory behaviors, such as chemotaxis (motion up or down a chemical gradient) or chemokinesis (dependence of speed on chemical concentration), which enable them to carry out vital functions including immune response, egg fertilization, and predator evasion. These have inspired researchers to develop self-propelled colloidal analogues to biological microswimmers, known as active colloids, that perform similar feats. Here, we study the behavior of half-platinum half-gold (Pt/Au) self-propelled rods in antiparallel gradients of hydrogen peroxide fuel and salt, which tend to increase and decrease the rods' speed, respectively. Brownian Dynamics simulations, a Fokker-Planck theoretical model, and experiments demonstrate that, at steady state, the rods accumulate in low-speed (salt-rich, peroxide-poor) regions not because of chemotaxis, but because of chemokinesis. Chemokinesis is distinct from chemotaxis in that no directional sensing or reorientation capabilities are required. The agreement between simulations, model, and experiments bolsters the role of chemokinesis in this system. This work suggests a novel strategy of exploiting chemokinesis to effect accumulation of motile colloids in desired areas.
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Affiliation(s)
- Jeffrey L Moran
- Department of Mechanical Engineering, George Mason University, Fairfax, VA, USA.
| | - Philip M Wheat
- Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, AZ, USA
| | - Nathan A Marine
- Ira A. Fulton Schools of Engineering, Arizona State University, Tempe, AZ, USA
| | - Jonathan D Posner
- Department of Mechanical Engineering, University of Washington, Seattle, WA, USA. .,Department of Chemical Engineering, University of Washington, Seattle, WA, USA. .,Department of Family Medicine, School of Medicine, University of Washington, Seattle, WA, USA.
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33
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Vennettilli M, Erez A, Mugler A. Multicellular sensing at a feedback-induced critical point. Phys Rev E 2020; 102:052411. [PMID: 33327087 DOI: 10.1103/physreve.102.052411] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 10/06/2020] [Indexed: 11/07/2022]
Abstract
Feedback in sensory biochemical networks can give rise to bifurcations in cells' behavioral response. These bifurcations share many properties with thermodynamic critical points. Evidence suggests that biological systems may operate near these critical points, but the functional benefit of doing so remains poorly understood. Here we investigate a simple biochemical model with nonlinear feedback and multicellular communication to determine if criticality provides a functional benefit in terms of the ability to gain information about a stochastic chemical signal. We find that when signal fluctuations are slow, the mutual information between the signal and the intracellular readout is maximized at criticality, because the benefit of high signal susceptibility outweighs the detriment of high readout noise. When cells communicate, criticality gives rise to long-range correlations in readout molecule number among cells. Consequently, we find that communication increases the mutual information between a given cell's readout and the spatial average of the signal across the population. Finally, we find that both with and without communication, the sensory benefits of criticality compete with critical slowing down, such that the information rate, as opposed to the information itself, is minimized at the critical point. Our results reveal the costs and benefits of feedback-induced criticality for multicellular sensing.
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Affiliation(s)
- Michael Vennettilli
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
| | - Amir Erez
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, USA
- The Racah Institute of Physics, Hebrew University, Jerusalem 91904, Israel
| | - Andrew Mugler
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260, USA
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34
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Beroz F, Zhou D, Mao X, Lubensky DK. Physical limits to sensing material properties. Nat Commun 2020; 11:5170. [PMID: 33056989 PMCID: PMC7560877 DOI: 10.1038/s41467-020-18995-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2019] [Accepted: 08/25/2020] [Indexed: 12/03/2022] Open
Abstract
All materials respond heterogeneously at small scales, which limits what a sensor can learn. Although previous studies have characterized measurement noise arising from thermal fluctuations, the limits imposed by structural heterogeneity have remained unclear. In this paper, we find that the least fractional uncertainty with which a sensor can determine a material constant λ0 of an elastic medium is approximately [Formula: see text] for a ≫ d ≫ ξ, [Formula: see text], and D > 1, where a is the size of the sensor, d is its spatial resolution, ξ is the correlation length of fluctuations in λ0, Δλ is the local variability of λ0, and D is the dimension of the medium. Our results reveal how one can construct devices capable of sensing near these limits, e.g. for medical diagnostics. We use our theoretical framework to estimate the limits of mechanosensing in a biopolymer network, a sensory process involved in cellular behavior, medical diagnostics, and material fabrication.
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Affiliation(s)
- Farzan Beroz
- Department of Physics, University of Michigan, Ann Arbor, MI, 48109, USA.
| | - Di Zhou
- Department of Physics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - Xiaoming Mao
- Department of Physics, University of Michigan, Ann Arbor, MI, 48109, USA
| | - David K Lubensky
- Department of Physics, University of Michigan, Ann Arbor, MI, 48109, USA
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35
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Dobramysl U, Holcman D. Triangulation Sensing to Determine the Gradient Source from Diffusing Particles to Small Cell Receptors. PHYSICAL REVIEW LETTERS 2020; 125:148102. [PMID: 33064548 DOI: 10.1103/physrevlett.125.148102] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Accepted: 09/03/2020] [Indexed: 06/11/2023]
Abstract
How does a cell locate the source of molecular guidance cues from within a concentration gradient? We present a computational approach to recover the source from the absorbed fluxes at narrow receptor windows located on the surface of the cell. In the limit of fast binding, we solve the steady-state diffusion equation using an asymptotic approach and hybrid stochastic-analytical simulations. We show that the sensitivity to the gradient direction decays too rapidly to enable long-distance sensing. We illustrate how this constraint can be alleviated when triangulating the source with an increasing number of receptor windows and quantify the susceptibility of this process to flux perturbations.
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Affiliation(s)
- Ulrich Dobramysl
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Cambridge CB3 0WA, United Kingdom
- Wellcome Trust / CRUK Gurdon Institute, University of Cambridge, Cambridge CB2 1QN, United Kingdom
| | - David Holcman
- Group Computational Biology and Data modeling, IBENS, Ecole Normale Superieure - PSL, Paris, France
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36
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Desponds J, Vergassola M, Walczak AM. A mechanism for hunchback promoters to readout morphogenetic positional information in less than a minute. eLife 2020; 9:49758. [PMID: 32723476 PMCID: PMC7428309 DOI: 10.7554/elife.49758] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2019] [Accepted: 07/29/2020] [Indexed: 12/14/2022] Open
Abstract
Cell fate decisions in the fly embryo are rapid: hunchback genes decide in minutes whether nuclei follow the anterior/posterior developmental blueprint by reading out positional information in the Bicoid morphogen. This developmental system is a prototype of regulatory decision processes that combine speed and accuracy. Traditional arguments based on fixed-time sampling of Bicoid concentration indicate that an accurate readout is impossible within the experimental times. This raises the general issue of how speed-accuracy tradeoffs are achieved. Here, we compare fixed-time to on-the-fly decisions, based on comparing the likelihoods of anterior/posterior locations. We found that these more efficient schemes complete reliable cell fate decisions within the short embryological timescales. We discuss the influence of promoter architectures on decision times and error rates, present concrete examples that rapidly readout the morphogen, and predictions for new experiments. Lastly, we suggest a simple mechanism for RNA production and degradation that approximates the log-likelihood function.
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Affiliation(s)
- Jonathan Desponds
- Physics Department, University of California, San Diego, La Jolla, United States
| | - Massimo Vergassola
- Physics Department, University of California, San Diego, La Jolla, United States
| | - Aleksandra M Walczak
- Laboratoire de Physique, Ecole Normale Supérieure, PSL Research University, CNRS, Sorbonne Université, Paris, France
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37
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Avanzini F, Falasco G, Esposito M. Chemical cloaking. Phys Rev E 2020; 101:060102. [PMID: 32688465 DOI: 10.1103/physreve.101.060102] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2019] [Accepted: 05/22/2020] [Indexed: 11/07/2022]
Abstract
Hiding an object in a chemical gradient requires one to suppress the distortions it would naturally cause on it. To do so, we propose a strategy based on coating the object with a chemical reaction-diffusion network which can act as an active cloaking device. By controlling the concentration of some species in its immediate surrounding, the chemical reactions redirect the gradient as if the object was not there. We also show that a substantial fraction of the energy required to cloak can be extracted from the chemical gradient itself.
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Affiliation(s)
- Francesco Avanzini
- Complex Systems and Statistical Mechanics, Department of Physics and Materials Science, University of Luxembourg, L-1511, Luxembourg
| | - Gianmaria Falasco
- Complex Systems and Statistical Mechanics, Department of Physics and Materials Science, University of Luxembourg, L-1511, Luxembourg
| | - Massimiliano Esposito
- Complex Systems and Statistical Mechanics, Department of Physics and Materials Science, University of Luxembourg, L-1511, Luxembourg
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38
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Lawley SD, Lindsay AE, Miles CE. Receptor Organization Determines the Limits of Single-Cell Source Location Detection. PHYSICAL REVIEW LETTERS 2020; 125:018102. [PMID: 32678664 DOI: 10.1103/physrevlett.125.018102] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Accepted: 06/09/2020] [Indexed: 06/11/2023]
Abstract
Many types of cells require the ability to pinpoint the location of an external stimulus from the arrival of diffusing signaling molecules at cell-surface receptors. How does the organization (number and spatial configuration) of these receptors shape the limit of a cell's ability to infer the source location? In the idealized scenario of a spherical cell, we apply asymptotic analysis to compute splitting probabilities between individual receptors and formulate an information-theoretic framework to quantify the role of receptor organization. Clustered configurations of receptors provide an advantage in detecting sources aligned with the clusters, suggesting a possible multiscale mechanism for single-cell source inference.
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Affiliation(s)
- Sean D Lawley
- Department of Mathematics, University of Utah, Salt Lake City, Utah 84112, USA
| | - Alan E Lindsay
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame, South Bend, Indiana 46556, USA
| | - Christopher E Miles
- Courant Institute of Mathematical Sciences, New York University, New York, New York 10005, USA
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39
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Fancher S, Vennettilli M, Hilgert N, Mugler A. Precision of Flow Sensing by Self-Communicating Cells. PHYSICAL REVIEW LETTERS 2020; 124:168101. [PMID: 32383913 DOI: 10.1103/physrevlett.124.168101] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Accepted: 03/23/2020] [Indexed: 06/11/2023]
Abstract
Metastatic cancer cells detect the direction of lymphatic flow by self-communication: they secrete and detect a chemical which, due to the flow, returns to the cell surface anisotropically. The secretion rate is low, meaning detection noise may play an important role, but the sensory precision of this mechanism has not been explored. Here we derive the precision of flow sensing for two ubiquitous detection methods: absorption vs reversible binding to surface receptors. We find that binding is more precise due to the fact that absorption distorts the signal that the cell aims to detect. Comparing to experiments, our results suggest that the cancer cells operate remarkably close to the physical detection limit. Our prediction that cells should bind the chemical reversibly, not absorb it, is supported by endocytosis data for this ligand-receptor pair.
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Affiliation(s)
- Sean Fancher
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Michael Vennettilli
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
| | - Nicholas Hilgert
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
| | - Andrew Mugler
- Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA
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40
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Heemskerk I. Full of potential: Pluripotent stem cells for the systems biology of embryonic patterning. Dev Biol 2020; 460:86-98. [DOI: 10.1016/j.ydbio.2019.05.004] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Revised: 05/03/2019] [Accepted: 05/03/2019] [Indexed: 02/07/2023]
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41
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Trötschel C, Hamzeh H, Alvarez L, Pascal R, Lavryk F, Bönigk W, Körschen HG, Müller A, Poetsch A, Rennhack A, Gui L, Nicastro D, Strünker T, Seifert R, Kaupp UB. Absolute proteomic quantification reveals design principles of sperm flagellar chemosensation. EMBO J 2020; 39:e102723. [PMID: 31880004 PMCID: PMC7024835 DOI: 10.15252/embj.2019102723] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 11/19/2019] [Accepted: 11/22/2019] [Indexed: 11/19/2022] Open
Abstract
Cilia serve as cellular antennae that translate sensory information into physiological responses. In the sperm flagellum, a single chemoattractant molecule can trigger a Ca2+ rise that controls motility. The mechanisms underlying such ultra-sensitivity are ill-defined. Here, we determine by mass spectrometry the copy number of nineteen chemosensory signaling proteins in sperm flagella from the sea urchin Arbacia punctulata. Proteins are up to 1,000-fold more abundant than the free cellular messengers cAMP, cGMP, H+ , and Ca2+ . Opto-chemical techniques show that high protein concentrations kinetically compartmentalize the flagellum: Within milliseconds, cGMP is relayed from the receptor guanylate cyclase to a cGMP-gated channel that serves as a perfect chemo-electrical transducer. cGMP is rapidly hydrolyzed, possibly via "substrate channeling" from the channel to the phosphodiesterase PDE5. The channel/PDE5 tandem encodes cGMP turnover rates rather than concentrations. The rate-detection mechanism allows continuous stimulus sampling over a wide dynamic range. The textbook notion of signal amplification-few enzyme molecules process many messenger molecules-does not hold for sperm flagella. Instead, high protein concentrations ascertain messenger detection. Similar mechanisms may occur in other small compartments like primary cilia or dendritic spines.
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Affiliation(s)
- Christian Trötschel
- Fakultät für Biologie und BiotechnologieRuhr‐Universität BochumBochumGermany
| | - Hussein Hamzeh
- Center of Advanced European Studies and Research (caesar), Molecular Sensory SystemsBonnGermany
- Marine Biological LaboratoryWoods HoleMAUSA
| | - Luis Alvarez
- Center of Advanced European Studies and Research (caesar), Molecular Sensory SystemsBonnGermany
| | - René Pascal
- Center of Advanced European Studies and Research (caesar), Molecular Sensory SystemsBonnGermany
| | - Fedir Lavryk
- Center of Advanced European Studies and Research (caesar), Molecular Sensory SystemsBonnGermany
| | - Wolfgang Bönigk
- Center of Advanced European Studies and Research (caesar), Molecular Sensory SystemsBonnGermany
| | - Heinz G Körschen
- Center of Advanced European Studies and Research (caesar), Molecular Sensory SystemsBonnGermany
| | - Astrid Müller
- Center of Advanced European Studies and Research (caesar), Molecular Sensory SystemsBonnGermany
| | - Ansgar Poetsch
- Fakultät für Biologie und BiotechnologieRuhr‐Universität BochumBochumGermany
- Present address:
Center for Marine and Molecular BiotechnologyQNLMQindaoChina
- Present address:
College of Marine Life SciencesOcean University of ChinaQingdaoChina
| | - Andreas Rennhack
- Center of Advanced European Studies and Research (caesar), Molecular Sensory SystemsBonnGermany
| | - Long Gui
- Departments of Cell Biology and BiophysicsUniversity of Texas Southwestern Medical CenterDallasTXUSA
| | - Daniela Nicastro
- Departments of Cell Biology and BiophysicsUniversity of Texas Southwestern Medical CenterDallasTXUSA
| | - Timo Strünker
- Center of Advanced European Studies and Research (caesar), Molecular Sensory SystemsBonnGermany
- Marine Biological LaboratoryWoods HoleMAUSA
- Center of Reproductive Medicine and AndrologyUniversity Hospital MünsterMünsterGermany
| | - Reinhard Seifert
- Center of Advanced European Studies and Research (caesar), Molecular Sensory SystemsBonnGermany
- Marine Biological LaboratoryWoods HoleMAUSA
| | - U Benjamin Kaupp
- Center of Advanced European Studies and Research (caesar), Molecular Sensory SystemsBonnGermany
- Marine Biological LaboratoryWoods HoleMAUSA
- Life& Medical Sciences Institute (LIMES)University of BonnBonnGermany
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42
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Qiu H, Yuan Z, Zhou T, Chen L. Different effects of fast and slow input fluctuations on output in gene regulation. CHAOS (WOODBURY, N.Y.) 2020; 30:023104. [PMID: 32113227 DOI: 10.1063/1.5133148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 01/14/2020] [Indexed: 06/10/2023]
Abstract
An important task in the post-gene era is to understand the role of stochasticity in gene regulation. Here, we analyze a cascade model of stochastic gene expression, where the upstream gene stochastically generates proteins that regulate, as transcription factors, stochastic synthesis of the downstream output. We find that in contrast to fast input fluctuations that do not change the behavior of the downstream system qualitatively, slow input fluctuations can induce different modes of the distribution of downstream output and even stochastic focusing or defocusing of the downstream output level, although the regulatory protein follows the same distribution in both cases. This finding is counterintuitive but can have broad biological implications, e.g., slow input rather than fast fluctuations may both increase the survival probability of cells and enhance the sensitivity of intracellular regulation. In addition, we find that input fluctuations can minimize the output noise.
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Affiliation(s)
- Huahai Qiu
- School of Mathematics and Computers, Wuhan Textile University, Wuhan 430200, China
| | - Zhanjiang Yuan
- Guangdong Province Key Laboratory of Computational Science, School of Mathematics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Tianshou Zhou
- Guangdong Province Key Laboratory of Computational Science, School of Mathematics, Sun Yat-Sen University, Guangzhou 510275, China
| | - Luonan Chen
- Key Laboratory of Systems Biology, Center for Excellence in Molecular Cell Science, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China
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43
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Abstract
Even single-celled eukaryotes are capable of highly complex behaviors. A new study reveals how one unicellular predator actively manipulates and remodels its unique cytoskeletal morphology to achieve rapid shape changes and a remarkable hunting strategy.
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Affiliation(s)
- Kirsty Y Wan
- Living Systems Institute, University of Exeter, Stocker Road, EX4 4QD, UK.
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44
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Hopkins A, Camley BA. Leader cells in collective chemotaxis: Optimality and trade-offs. Phys Rev E 2019; 100:032417. [PMID: 31639926 DOI: 10.1103/physreve.100.032417] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2019] [Indexed: 11/06/2022]
Abstract
Clusters of cells can work together in order to follow a signal gradient, chemotaxing even when single cells do not. Cells in different regions of collectively migrating neural crest streams show different gene expression profiles, suggesting that cells may specialize to leader and follower roles. We use a minimal mathematical model to understand when this specialization is advantageous. In our model, leader cells sense the gradient with an accuracy that depends on the kinetics of ligand-receptor binding, while follower cells follow the cluster's direction with a finite error. Intuitively, specialization into leaders and followers should be optimal when a few cells have more information than the rest of the cluster, such as in the presence of a sharp transition in chemoattractant concentration. We do find this-but also find that high levels of specialization can be optimal in the opposite limit of very shallow gradients. We also predict that the best location for leaders may not be at the front of the cluster. In following leaders, clusters may have to choose between speed and flexibility. Clusters with only a few leaders can take orders of magnitude more time to reorient than all-leader clusters.
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Affiliation(s)
- Austin Hopkins
- Department of Physics & Astronomy, Johns Hopkins University, Baltimore, Maryland 21218, USA
| | - Brian A Camley
- Department of Physics & Astronomy and Department of Biophysics, Johns Hopkins University, Baltimore, Maryland 21218, USA
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45
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Wasnik VH, Lipp P, Kruse K. Accuracy of position determination in Ca^{2+} signaling. Phys Rev E 2019; 100:022401. [PMID: 31574643 DOI: 10.1103/physreve.100.022401] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Indexed: 02/02/2023]
Abstract
A living cell senses its environment and responds to external signals. In this paper, we study theoretically the precision at which cells can determine the position of a spatially localized transient extracellular signal. To this end, we focus on the case where the stimulus is converted into the release of a small molecule that acts as a second messenger, for example, Ca^{2+}, and activates kinases that change the activity of enzymes by phosphorylating them. We analyze the spatial distribution of phosphorylation events using stochastic simulations as well as a mean-field approach. Kinases that need to bind to the cell membrane for getting activated provide more accurate estimates than cytosolic kinases. Our results could explain why the rate of Ca^{2+} detachment from the membrane-binding conventional protein kinase Cα is larger than its phosphorylation rate.
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Affiliation(s)
- Vaibhav H Wasnik
- NCCR Chemical Biology, Departments of Biochemistry and Theoretical Physics, University of Geneva, 1211 Geneva, Switzerland.,Indian Institute of Technology Goa, Ponda 403401, India
| | - Peter Lipp
- Institute for Molecular Cell Biology, Research Centre for Molecular Imaging and Screening, Center for Molecular Signaling, Medical Faculty, Saarland University, Homburg/Saar, Germany
| | - Karsten Kruse
- NCCR Chemical Biology, Departments of Biochemistry and Theoretical Physics, University of Geneva, 1211 Geneva, Switzerland
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46
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Wasnik VH, Lipp P, Kruse K. Positional Information Readout in Ca^{2+} Signaling. PHYSICAL REVIEW LETTERS 2019; 123:058102. [PMID: 31491303 DOI: 10.1103/physrevlett.123.058102] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2017] [Revised: 07/20/2018] [Indexed: 06/10/2023]
Abstract
Living cells respond to spatially confined signals. Intracellular signal transmission often involves the release of second messengers like Ca^{2+}. They eventually trigger a physiological response, for example, by activating kinases that in turn activate target proteins through phosphorylation. Here, we investigate theoretically how positional information can be accurately read out by protein phosphorylation in spite of rapid second messenger diffusion. We find that accuracy is increased by binding of kinases to the cell membrane prior to phosphorylation and by increasing the rate of Ca^{2+} loss from the cell interior. These findings could explain some salient features of the conventional protein kinase Cα.
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Affiliation(s)
- Vaibhav H Wasnik
- NCCR Chemical Biology, Departments of Biochemistry and Theoretical Physics, University of Geneva, 1211 Geneva, Switzerland
- Indian Institute of Technology Goa, Ponda 403401, India
| | - Peter Lipp
- Institute for Molecular Cell Biology, Research Centre for Molecular Imaging and Screening, Center for Molecular Signaling (PZMS), Medical Faculty, Saarland University, 66421 Homburg/Saar, Germany
| | - Karsten Kruse
- NCCR Chemical Biology, Departments of Biochemistry and Theoretical Physics, University of Geneva, 1211 Geneva, Switzerland
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47
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Bacteria push the limits of chemotactic precision to navigate dynamic chemical gradients. Proc Natl Acad Sci U S A 2019; 116:10792-10797. [PMID: 31097577 DOI: 10.1073/pnas.1816621116] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Ephemeral aggregations of bacteria are ubiquitous in the environment, where they serve as hotbeds of metabolic activity, nutrient cycling, and horizontal gene transfer. In many cases, these regions of high bacterial concentration are thought to form when motile cells use chemotaxis to navigate to chemical hotspots. However, what governs the dynamics of bacterial aggregations is unclear. Here, we use an experimental platform to create realistic submillimeter-scale nutrient pulses with controlled nutrient concentrations. By combining experiments, mathematical theory, and agent-based simulations, we show that individual Vibrio ordalii bacteria begin chemotaxis toward hotspots of dissolved organic matter (DOM) when the magnitude of the chemical gradient rises sufficiently far above the sensory noise that is generated by stochastic encounters with chemoattractant molecules. Each DOM hotspot is surrounded by a dynamic ring of chemotaxing cells, which congregate in regions of high DOM concentration before dispersing as DOM diffuses and gradients become too noisy for cells to respond to. We demonstrate that V. ordalii operates close to the theoretical limits on chemotactic precision. Numerical simulations of chemotactic bacteria, in which molecule counting noise is explicitly taken into account, point at a tradeoff between nutrient acquisition and the cost of chemotactic precision. More generally, our results illustrate how limits on sensory precision can be used to understand the location, spatial extent, and lifespan of bacterial behavioral responses in ecologically relevant environments.
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48
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Carballo-Pacheco M, Desponds J, Gavrilchenko T, Mayer A, Prizak R, Reddy G, Nemenman I, Mora T. Receptor crosstalk improves concentration sensing of multiple ligands. Phys Rev E 2019; 99:022423. [PMID: 30934315 DOI: 10.1103/physreve.99.022423] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2018] [Indexed: 06/09/2023]
Abstract
Cells need to reliably sense external ligand concentrations to achieve various biological functions such as chemotaxis or signaling. The molecular recognition of ligands by surface receptors is degenerate in many systems, leading to crosstalk between ligand-receptor pairs. Crosstalk is often thought of as a deviation from optimal specific recognition, as the binding of noncognate ligands can interfere with the detection of the receptor's cognate ligand, possibly leading to a false triggering of a downstream signaling pathway. Here we quantify the optimal precision of sensing the concentrations of multiple ligands by a collection of promiscuous receptors. We demonstrate that crosstalk can improve precision in concentration sensing and discrimination tasks. To achieve superior precision, the additional information about ligand concentrations contained in short binding events of the noncognate ligand should be exploited. We present a proofreading scheme to realize an approximate estimation of multiple ligand concentrations that reaches a precision close to the derived optimal bounds. Our results help rationalize the observed ubiquity of receptor crosstalk in molecular sensing.
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Affiliation(s)
- Martín Carballo-Pacheco
- School of Physics and Astronomy, University of Edinburgh, Edinburgh, EH9 3FD, United Kingdom
| | - Jonathan Desponds
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Tatyana Gavrilchenko
- Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, PA 19104, USA
| | - Andreas Mayer
- Lewis-Sigler Institute for Integrative Genomics, Princeton University, Princeton, NJ 08544, USA
| | - Roshan Prizak
- Institute of Science and Technology Austria, Am Campus 1, A-3400, Klosterneuburg, Austria
| | - Gautam Reddy
- Department of Physics, University of California San Diego, La Jolla, CA 92093, USA
| | - Ilya Nemenman
- Department of Physics, Department of Biology, and Initiative in Theory and Modeling of Living Systems, Emory University, Atlanta, GA 30322, USA
| | - Thierry Mora
- Laboratoire de physique de l'École normale supérieure (PSL university), CNRS, Sorbonne University, and University Paris-Diderot, 75005 Paris, France
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Mosayebi R, Ahmadzadeh A, Wicke W, Jamali V, Schober R, Nasiri-Kenari M. Early Cancer Detection in Blood Vessels Using Mobile Nanosensors. IEEE Trans Nanobioscience 2018; 18:103-116. [PMID: 30530333 DOI: 10.1109/tnb.2018.2885463] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
In this paper, we propose using mobile nanosensors (MNSs) for early stage anomaly detection. For concreteness, we focus on the detection of cancer cells located in a particular region of a blood vessel. These cancer cells produce and emit special molecules, so-called biomarkers, which are symptomatic for the presence of anomaly, into the cardiovascular system. Detection of cancer biomarkers with conventional blood tests is difficult in the early stages of a cancer due to the very low concentration of the biomarkers in the samples taken. However, close to the cancer cells, the concentration of the cancer biomarkers is high. Hence, detection is possible if a sensor with the ability to detect these biomarkers is placed in the vicinity of the cancer cells. Therefore, in this paper, we study the use of MNSs that are injected at a suitable injection site and can move through the blood vessels of the cardiovascular system, which potentially contain cancer cells. These MNSs can be activated by the biomarkers close to the cancer cells, where the biomarker concentration is sufficiently high. Eventually, the MNSs are collected by a fusion center (FC), where their activation levels are read and exploited to declare the presence of anomaly. We analytically derive the biomarker concentration in a network of interconnected blood vessels as well as the probability mass function of the MNSs' activation levels and validate the obtained results via particle-based simulations. Then, we derive the optimal decision rule for the FC regarding the presence of anomaly assuming that the entire network is known at the FC. Finally, for the FC, we propose a simple sum detector that does not require knowledge of the network topology. Our simulations reveal that while the optimal detector achieves a higher performance than the sum detector, both proposed detectors significantly outperform a benchmark scheme that uses fixed nanosensors at the FC.
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Camley BA. Collective gradient sensing and chemotaxis: modeling and recent developments. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2018; 30:223001. [PMID: 29644981 PMCID: PMC6252055 DOI: 10.1088/1361-648x/aabd9f] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Cells measure a vast variety of signals, from their environment's stiffness to chemical concentrations and gradients; physical principles strongly limit how accurately they can do this. However, when many cells work together, they can cooperate to exceed the accuracy of any single cell. In this topical review, I will discuss the experimental evidence showing that cells collectively sense gradients of many signal types, and the models and physical principles involved. I also propose new routes by which experiments and theory can expand our understanding of these problems.
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Affiliation(s)
- Brian A Camley
- Departments of Physics & Astronomy and Biophysics, Johns Hopkins University, Baltimore, MD, United States of America
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