1
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Chadha Y, Khurana A, Schmoller KM. Eukaryotic cell size regulation and its implications for cellular function and dysfunction. Physiol Rev 2024; 104:1679-1717. [PMID: 38900644 DOI: 10.1152/physrev.00046.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2023] [Revised: 05/24/2024] [Accepted: 06/19/2024] [Indexed: 06/22/2024] Open
Abstract
Depending on cell type, environmental inputs, and disease, the cells in the human body can have widely different sizes. In recent years, it has become clear that cell size is a major regulator of cell function. However, we are only beginning to understand how the optimization of cell function determines a given cell's optimal size. Here, we review currently known size control strategies of eukaryotic cells and the intricate link of cell size to intracellular biomolecular scaling, organelle homeostasis, and cell cycle progression. We detail the cell size-dependent regulation of early development and the impact of cell size on cell differentiation. Given the importance of cell size for normal cellular physiology, cell size control must account for changing environmental conditions. We describe how cells sense environmental stimuli, such as nutrient availability, and accordingly adapt their size by regulating cell growth and cell cycle progression. Moreover, we discuss the correlation of pathological states with misregulation of cell size and how for a long time this was considered a downstream consequence of cellular dysfunction. We review newer studies that reveal a reversed causality, with misregulated cell size leading to pathophysiological phenotypes such as senescence and aging. In summary, we highlight the important roles of cell size in cellular function and dysfunction, which could have major implications for both diagnostics and treatment in the clinic.
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Affiliation(s)
- Yagya Chadha
- Institute of Functional Epigenetics, Molecular Targets and Therapeutics Center, Helmholtz Zentrum München, Neuherberg, Germany
| | - Arohi Khurana
- Institute of Functional Epigenetics, Molecular Targets and Therapeutics Center, Helmholtz Zentrum München, Neuherberg, Germany
| | - Kurt M Schmoller
- Institute of Functional Epigenetics, Molecular Targets and Therapeutics Center, Helmholtz Zentrum München, Neuherberg, Germany
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2
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Lanz MC, Zhang S, Swaffer MP, Ziv I, Götz LH, Kim J, McCarthy F, Jarosz DF, Elias JE, Skotheim JM. Genome dilution by cell growth drives starvation-like proteome remodeling in mammalian and yeast cells. Nat Struct Mol Biol 2024:10.1038/s41594-024-01353-z. [PMID: 39048803 DOI: 10.1038/s41594-024-01353-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 06/12/2024] [Indexed: 07/27/2024]
Abstract
Cell size is tightly controlled in healthy tissues and single-celled organisms, but it remains unclear how cell size influences physiology. Increasing cell size was recently shown to remodel the proteomes of cultured human cells, demonstrating that large and small cells of the same type can be compositionally different. In the present study, we utilize the natural heterogeneity of hepatocyte ploidy and yeast genetics to establish that the ploidy-to-cell size ratio is a highly conserved determinant of proteome composition. In both mammalian and yeast cells, genome dilution by cell growth elicits a starvation-like phenotype, suggesting that growth in large cells is restricted by genome concentration in a manner that mimics a limiting nutrient. Moreover, genome dilution explains some proteomic changes ascribed to yeast aging. Overall, our data indicate that genome concentration drives changes in cell composition independently of external environmental cues.
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Affiliation(s)
- Michael C Lanz
- Department of Biology, Stanford University, Stanford, CA, USA.
- Chan Zuckerberg Biohub San Francisco, Stanford University, Stanford, CA, USA.
| | - Shuyuan Zhang
- Department of Biology, Stanford University, Stanford, CA, USA
| | | | - Inbal Ziv
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, USA
| | | | - Jacob Kim
- Department of Biology, Stanford University, Stanford, CA, USA
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, USA
| | - Frank McCarthy
- Chan Zuckerberg Biohub San Francisco, Stanford University, Stanford, CA, USA
| | - Daniel F Jarosz
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, USA
- Department of Developmental Biology, Stanford University, Stanford, CA, USA
| | - Joshua E Elias
- Chan Zuckerberg Biohub San Francisco, Stanford University, Stanford, CA, USA
| | - Jan M Skotheim
- Department of Biology, Stanford University, Stanford, CA, USA.
- Chan Zuckerberg Biohub San Francisco, Stanford University, Stanford, CA, USA.
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3
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Xie J, Huck WTS, Bao M. Unveiling the Intricate Connection: Cell Volume as a Key Regulator of Mechanotransduction. Annu Rev Biophys 2024; 53:299-317. [PMID: 38424091 DOI: 10.1146/annurev-biophys-030822-035656] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/02/2024]
Abstract
The volumes of living cells undergo dynamic changes to maintain the cells' structural and functional integrity in many physiological processes. Minor fluctuations in cell volume can serve as intrinsic signals that play a crucial role in cell fate determination during mechanotransduction. In this review, we discuss the variability of cell volume and its role in vivo, along with an overview of the mechanisms governing cell volume regulation. Additionally, we provide insights into the current approaches used to control cell volume in vitro. Furthermore, we summarize the biological implications of cell volume regulation and discuss recent advances in understanding the fundamental relationship between cell volume and mechanotransduction. Finally, we delve into the potential underlying mechanisms, including intracellular macromolecular crowding and cellular mechanics, that govern the global regulation of cell fate in response to changes in cell volume. By exploring the intricate interplay between cell volume and mechanotransduction, we underscore the importance of considering cell volume as a fundamental signaling cue to unravel the basic principles of mechanotransduction. Additionally, we propose future research directions that can extend our current understanding of cell volume in mechanotransduction. Overall, this review highlights the significance of considering cell volume as a fundamental signal in understanding the basic principles in mechanotransduction and points out the possibility of controlling cell volume to control cell fate, mitigate disease-related damage, and facilitate the healing of damaged tissues.
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Affiliation(s)
- Jing Xie
- Institute of Biomedical Engineering, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu, China
| | - Wilhelm T S Huck
- Institute for Molecules and Materials, Radboud University, Nijmegen, The Netherlands;
| | - Min Bao
- Oujiang Laboratory (Zhejiang Lab for Regenerative Medicine, Vision and Brain Health), First Affiliated Hospital of Wenzhou Medical University, Wenzhou, Zhejiang, China;
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4
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Dixon JC, Frick CL, Leveille CL, Garrison P, Lee PA, Mogre SS, Morris B, Nivedita N, Vasan R, Chen J, Fraser CL, Gamlin CR, Harris LK, Hendershott MC, Johnson GT, Klein KN, Oluoch SA, Thirstrup DJ, Sluzewski MF, Wilhelm L, Yang R, Toloudis DM, Viana MP, Theriot JA, Rafelski SM. Colony context and size-dependent compensation mechanisms give rise to variations in nuclear growth trajectories. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.06.28.601071. [PMID: 38979140 PMCID: PMC11230432 DOI: 10.1101/2024.06.28.601071] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
To investigate the fundamental question of how cellular variations arise across spatiotemporal scales in a population of identical healthy cells, we focused on nuclear growth in hiPS cell colonies as a model system. We generated a 3D timelapse dataset of thousands of nuclei over multiple days, and developed open-source tools for image and data analysis and an interactive timelapse viewer for exploring quantitative features of nuclear size and shape. We performed a data-driven analysis of nuclear growth variations across timescales. We found that individual nuclear volume growth trajectories arise from short timescale variations attributable to their spatiotemporal context within the colony. We identified a strikingly time-invariant volume compensation relationship between nuclear growth duration and starting volume across the population. Notably, we discovered that inheritance plays a crucial role in determining these two key nuclear growth features while other growth features are determined by their spatiotemporal context and are not inherited.
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Affiliation(s)
- Julie C. Dixon
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
- These authors contributed equally to this work
| | - Christopher L. Frick
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
- These authors contributed equally to this work
| | - Chantelle L. Leveille
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
- These authors contributed equally to this work
| | - Philip Garrison
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
- These authors contributed equally to this work
| | - Peyton A. Lee
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
- These authors contributed equally to this work
| | - Saurabh S. Mogre
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
- These authors contributed equally to this work
| | - Benjamin Morris
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
- These authors contributed equally to this work
| | - Nivedita Nivedita
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
- These authors contributed equally to this work
| | - Ritvik Vasan
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
- These authors contributed equally to this work
| | - Jianxu Chen
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
- Present address: Leibniz-Institut fur Analytische Wissenschaften – ISAS – e.V., Dortmund, 44139, Germany
| | - Cameron L. Fraser
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | - Clare R. Gamlin
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | - Leigh K. Harris
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | | | - Graham T. Johnson
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | - Kyle N. Klein
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | - Sandra A. Oluoch
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | - Derek J. Thirstrup
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | - M. Filip Sluzewski
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | - Lyndsay Wilhelm
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | - Ruian Yang
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | - Daniel M. Toloudis
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | - Matheus P. Viana
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
| | - Julie A. Theriot
- Department of Biology and Howard Hughes Medical Institute, University of Washington, Seattle, WA 98195, USA
| | - Susanne M. Rafelski
- Allen Institute for Cell Science, 615 Westlake Ave N, Seattle, WA, 98109, USA
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5
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Xie S, Zhang S, de Medeiros G, Liberali P, Skotheim JM. The G1/S transition in mammalian stem cells in vivo is autonomously regulated by cell size. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.04.09.588781. [PMID: 38645246 PMCID: PMC11030448 DOI: 10.1101/2024.04.09.588781] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/23/2024]
Abstract
Cell growth and division must be coordinated to maintain a stable cell size, but how this coordination is implemented in multicellular tissues remains unclear. In unicellular eukaryotes, autonomous cell size control mechanisms couple cell growth and division with little extracellular input. However, in multicellular tissues we do not know if autonomous cell size control mechanisms operate the same way or whether cell growth and cell cycle progression are separately controlled by cell-extrinsic signals. Here, we address this question by tracking single epidermal stem cells growing in adult mice. We find that a cell-autonomous size control mechanism, dependent on the RB pathway, sets the timing of S phase entry based on the cell's current size. Cell-extrinsic variations in the cellular microenvironment affect cell growth rates but not this autonomous coupling. Our work reassesses long-standing models of cell cycle regulation within complex metazoan tissues and identifies cell-autonomous size control as a critical mechanism regulating cell divisions in vivo and thereby a major contributor to stem cell heterogeneity.
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6
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Carpenter LC, Pérez-Verdugo F, Banerjee S. Mechanical control of cell proliferation patterns in growing epithelial monolayers. Biophys J 2024; 123:909-919. [PMID: 38449309 PMCID: PMC10995431 DOI: 10.1016/j.bpj.2024.03.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2023] [Revised: 01/13/2024] [Accepted: 03/01/2024] [Indexed: 03/08/2024] Open
Abstract
Cell proliferation plays a crucial role in regulating tissue homeostasis and development. However, our understanding of how cell proliferation is controlled in densely packed tissues is limited. Here we develop a computational framework to predict the patterns of cell proliferation in growing epithelial tissues, connecting single-cell behaviors and cell-cell interactions to tissue-level growth. Our model incorporates probabilistic rules governing cell growth, division, and elimination, also taking into account their feedback with tissue mechanics. In particular, cell growth is suppressed and apoptosis is enhanced in regions of high cell density. With these rules and model parameters calibrated using experimental data for epithelial monolayers, we predict how tissue confinement influences cell size and proliferation dynamics and how single-cell physical properties influence the spatiotemporal patterns of tissue growth. In this model, mechanical feedback between tissue confinement and cell growth leads to enhanced cell proliferation at tissue boundaries, whereas cell growth in the bulk is arrested, recapitulating experimental observations in epithelial tissues. By tuning cellular elasticity and contact inhibition of proliferation we can regulate the emergent patterns of cell proliferation, ranging from uniform growth at low contact inhibition to localized growth at higher contact inhibition. We show that the cell size threshold at G1/S transition governs the homeostatic cell density and tissue turnover rate, whereas the mechanical state of the tissue governs the dynamics of tissue growth. In particular, we find that the cellular parameters affecting tissue pressure play a significant role in determining the overall growth rate. Our computational study thus underscores the impact of cell mechanical properties on the spatiotemporal patterns of cell proliferation in growing epithelial tissues.
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Affiliation(s)
- Logan C Carpenter
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | | | - Shiladitya Banerjee
- Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania.
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7
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Li C, Xie SS, Wang J, Sharvia S, Chan KY. SC-Track: a robust cell-tracking algorithm for generating accurate single-cell lineages from diverse cell segmentations. Brief Bioinform 2024; 25:bbae192. [PMID: 38704671 PMCID: PMC11070058 DOI: 10.1093/bib/bbae192] [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: 01/12/2024] [Revised: 03/18/2024] [Accepted: 04/10/2024] [Indexed: 05/06/2024] Open
Abstract
Computational analysis of fluorescent timelapse microscopy images at the single-cell level is a powerful approach to study cellular changes that dictate important cell fate decisions. Core to this approach is the need to generate reliable cell segmentations and classifications necessary for accurate quantitative analysis. Deep learning-based convolutional neural networks (CNNs) have emerged as a promising solution to these challenges. However, current CNNs are prone to produce noisy cell segmentations and classifications, which is a significant barrier to constructing accurate single-cell lineages. To address this, we developed a novel algorithm called Single Cell Track (SC-Track), which employs a hierarchical probabilistic cache cascade model based on biological observations of cell division and movement dynamics. Our results show that SC-Track performs better than a panel of publicly available cell trackers on a diverse set of cell segmentation types. This cell-tracking performance was achieved without any parameter adjustments, making SC-Track an excellent generalized algorithm that can maintain robust cell-tracking performance in varying cell segmentation qualities, cell morphological appearances and imaging conditions. Furthermore, SC-Track is equipped with a cell class correction function to improve the accuracy of cell classifications in multiclass cell segmentation time series. These features together make SC-Track a robust cell-tracking algorithm that works well with noisy cell instance segmentation and classification predictions from CNNs to generate accurate single-cell lineages and classifications.
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Affiliation(s)
- Chengxin Li
- Department of Cardiovascular Medicine, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, P. R. China
- Centre for Cellular Biology and Signalling, Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Zhejiang University, Haining, 314400, P. R. China
| | - Shuang Shuang Xie
- Centre for Cellular Biology and Signalling, Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Zhejiang University, Haining, 314400, P. R. China
| | - Jiaqi Wang
- Centre for Cellular Biology and Signalling, Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Zhejiang University, Haining, 314400, P. R. China
| | - Septavera Sharvia
- Department of Computer Science, University of Hull, Hull, HU6 7RX, UK
| | - Kuan Yoow Chan
- Department of Cardiovascular Medicine, The Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, 310058, P. R. China
- Centre for Cellular Biology and Signalling, Zhejiang University-University of Edinburgh Institute, Zhejiang University School of Medicine, Zhejiang University, Haining, 314400, P. R. China
- College of Medicine and Veterinary Medicine, The University of Edinburgh, Edinburgh, EH4 2XR, UK
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8
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Lessenger AT, Swaffer MP, Skotheim JM, Feldman JL. Somatic polyploidy supports biosynthesis and tissue function by increasing transcriptional output. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.03.25.586714. [PMID: 38585999 PMCID: PMC10996643 DOI: 10.1101/2024.03.25.586714] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/09/2024]
Abstract
Cell size and biosynthetic capacity generally increase with increased DNA content. Polyploidy has therefore been proposed to be an adaptive strategy to increase cell size in specialized tissues with high biosynthetic demands. However, if and how DNA concentration limits cellular biosynthesis in vivo is not well understood, and the impacts of polyploidy in non-disease states is not well studied. Here, we show that polyploidy in the C. elegans intestine is critical for cell growth and yolk biosynthesis, a central role of this organ. Artificially lowering the DNA/cytoplasm ratio by reducing polyploidization in the intestine gave rise to smaller cells with more dilute mRNA. Highly-expressed transcripts were more sensitive to this mRNA dilution, whereas lowly-expressed genes were partially compensated - in part by loading more RNA Polymerase II on the remaining genomes. DNA-dilute cells had normal total protein concentration, which we propose is achieved by increasing production of translational machinery at the expense of specialized, cell-type specific proteins.
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9
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Diehl FF, Sapp KM, Vander Heiden MG. The bidirectional relationship between metabolism and cell cycle control. Trends Cell Biol 2024; 34:136-149. [PMID: 37385879 DOI: 10.1016/j.tcb.2023.05.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2023] [Revised: 05/30/2023] [Accepted: 05/31/2023] [Indexed: 07/01/2023]
Abstract
The relationship between metabolism and cell cycle progression is complex and bidirectional. Cells must rewire metabolism to meet changing biosynthetic demands across cell cycle phases. In turn, metabolism can influence cell cycle progression through direct regulation of cell cycle proteins, through nutrient-sensing signaling pathways, and through its impact on cell growth, which is linked to cell division. Furthermore, metabolism is a key player in mediating quiescence-proliferation transitions in physiologically important cell types, such as stem cells. How metabolism impacts cell cycle progression, exit, and re-entry, as well as how these processes impact metabolism, is not fully understood. Recent advances uncovering mechanistic links between cell cycle regulators and metabolic processes demonstrate a complex relationship between metabolism and cell cycle control, with many questions remaining.
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Affiliation(s)
- Frances F Diehl
- Department of Molecular Biology and Genetics, Howard Hughes Medical Institute, Johns Hopkins University School of Medicine, Baltimore, MD, USA; Koch Institute for Integrative Cancer Research and the Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Kiera M Sapp
- Koch Institute for Integrative Cancer Research and the Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Matthew G Vander Heiden
- Koch Institute for Integrative Cancer Research and the Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA; Dana-Farber Cancer Institute, Boston, MA, USA.
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10
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Liu X, Yan J, Kirschner MW. Cell size homeostasis is tightly controlled throughout the cell cycle. PLoS Biol 2024; 22:e3002453. [PMID: 38180950 PMCID: PMC10769027 DOI: 10.1371/journal.pbio.3002453] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Accepted: 11/28/2023] [Indexed: 01/07/2024] Open
Abstract
To achieve a stable size distribution over multiple generations, proliferating cells require a means of counteracting stochastic noise in the rate of growth, the time spent in various phases of the cell cycle, and the imprecision in the placement of the plane of cell division. In the most widely accepted model, cell size is thought to be regulated at the G1/S transition, such that cells smaller than a critical size pause at the end of G1 phase until they have accumulated mass to a predetermined size threshold, at which point the cells proceed through the rest of the cell cycle. However, a model, based solely on a specific size checkpoint at G1/S, cannot readily explain why cells with deficient G1/S control mechanisms are still able to maintain a very stable cell size distribution. Furthermore, such a model would not easily account for stochastic variation in cell size during the subsequent phases of the cell cycle, which cannot be anticipated at G1/S. To address such questions, we applied computationally enhanced quantitative phase microscopy (ceQPM) to populations of cultured human cell lines, which enables highly accurate measurement of cell dry mass of individual cells throughout the cell cycle. From these measurements, we have evaluated the factors that contribute to maintaining cell mass homeostasis at any point in the cell cycle. Our findings reveal that cell mass homeostasis is accurately maintained, despite disruptions to the normal G1/S machinery or perturbations in the rate of cell growth. Control of cell mass is generally not confined to regulation of the G1 length. Instead mass homeostasis is imposed throughout the cell cycle. In the cell lines examined, we find that the coefficient of variation (CV) in dry mass of cells in the population begins to decline well before the G1/S transition and continues to decline throughout S and G2 phases. Among the different cell types tested, the detailed response of cell growth rate to cell mass differs. However, in general, when it falls below that for exponential growth, the natural increase in the CV of cell mass is effectively constrained. We find that both mass-dependent cell cycle regulation and mass-dependent growth rate modulation contribute to reducing cell mass variation within the population. Through the interplay and coordination of these 2 processes, accurate cell mass homeostasis emerges. Such findings reveal previously unappreciated and very general principles of cell size control in proliferating cells. These same regulatory processes might also be operative in terminally differentiated cells. Further quantitative dynamical studies should lead to a better understanding of the underlying molecular mechanisms of cell size control.
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Affiliation(s)
- Xili Liu
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
| | - Jiawei Yan
- Department of Chemistry, Stanford University, Stanford, California, United States of America
| | - Marc W. Kirschner
- Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America
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11
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Stojanovski K, Gheorghe I, Lenart P, Lanjuin A, Mair WB, Towbin BD. Maintenance of appropriate size scaling of the C. elegans pharynx by YAP-1. Nat Commun 2023; 14:7564. [PMID: 37985670 PMCID: PMC10661912 DOI: 10.1038/s41467-023-43230-1] [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: 05/11/2023] [Accepted: 11/02/2023] [Indexed: 11/22/2023] Open
Abstract
Even slight imbalance between the growth rate of different organs can accumulate to a large deviation from their appropriate size during development. Here, we use live imaging of the pharynx of C. elegans to ask if and how organ size scaling nevertheless remains uniform among individuals. Growth trajectories of hundreds of individuals reveal that pharynxes grow by a near constant volume per larval stage that is independent of their initial size, such that undersized pharynxes catch-up in size during development. Tissue-specific depletion of RAGA-1, an activator of mTOR and growth, shows that maintaining correct pharynx-to-body size proportions involves a bi-directional coupling between pharynx size and body growth. In simulations, this coupling cannot be explained by limitation of food uptake alone, and genetic experiments reveal an involvement of the mechanotransducing transcriptional co-regulator yap-1. Our data suggests that mechanotransduction coordinates pharynx growth with other tissues, ensuring body plan uniformity among individuals.
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Affiliation(s)
| | - Ioana Gheorghe
- Institute of Cell Biology, University of Bern, Bern, Switzerland
- Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland
| | - Peter Lenart
- Institute of Cell Biology, University of Bern, Bern, Switzerland
| | - Anne Lanjuin
- Department Molecular Metabolism, Harvard TH Chan School of Public Health, Boston, MA, USA
| | - William B Mair
- Department Molecular Metabolism, Harvard TH Chan School of Public Health, Boston, MA, USA
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12
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Lanz MC, Zhang S, Swaffer MP, Hernández Götz L, McCarty F, Ziv I, Jarosz DF, Elias JE, Skotheim JM. Genome dilution by cell growth drives starvation-like proteome remodeling in mammalian and yeast cells. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.16.562558. [PMID: 37905015 PMCID: PMC10614910 DOI: 10.1101/2023.10.16.562558] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/02/2023]
Abstract
Cell size is tightly controlled in healthy tissues and single-celled organisms, but it remains unclear how size influences cell physiology. Increasing cell size was recently shown to remodel the proteomes of cultured human cells, demonstrating that large and small cells of the same type can be biochemically different. Here, we corroborate these results in mouse hepatocytes and extend our analysis using yeast. We find that size-dependent proteome changes are highly conserved and mostly independent of metabolic state. As eukaryotic cells grow larger, the dilution of the genome elicits a starvation-like proteome phenotype, suggesting that growth in large cells is limited by the genome in a manner analogous to a limiting nutrient. We also demonstrate that the proteomes of replicatively-aged yeast are primarily determined by their large size. Overall, our data suggest that genome concentration is a universal determinant of proteome content in growing cells.
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13
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Williamson D, Tasker-Brown W, Murray JAH, Jones AR, Band LR. Modelling how plant cell-cycle progression leads to cell size regulation. PLoS Comput Biol 2023; 19:e1011503. [PMID: 37862377 PMCID: PMC10653611 DOI: 10.1371/journal.pcbi.1011503] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2023] [Revised: 11/16/2023] [Accepted: 09/07/2023] [Indexed: 10/22/2023] Open
Abstract
Populations of cells typically maintain a consistent size, despite cell division rarely being precisely symmetrical. Therefore, cells must possess a mechanism of "size control", whereby the cell volume at birth affects cell-cycle progression. While size control mechanisms have been elucidated in a number of other organisms, it is not yet clear how this mechanism functions in plants. Here, we present a mathematical model of the key interactions in the plant cell cycle. Model simulations reveal that the network of interactions exhibits limit-cycle solutions, with biological switches underpinning both the G1/S and G2/M cell-cycle transitions. Embedding this network model within growing cells, we test hypotheses as to how cell-cycle progression can depend on cell size. We investigate two different mechanisms at both the G1/S and G2/M transitions: (i) differential expression of cell-cycle activator and inhibitor proteins (with synthesis of inhibitor proteins being independent of cell size), and (ii) equal inheritance of inhibitor proteins after cell division. The model demonstrates that both these mechanisms can lead to larger daughter cells progressing through the cell cycle more rapidly, and can thus contribute to cell-size control. To test how these features enable size homeostasis over multiple generations, we then simulated these mechanisms in a cell-population model with multiple rounds of cell division. These simulations suggested that integration of size-control mechanisms at both G1/S and G2/M provides long-term cell-size homeostasis. We concluded that while both size independence and equal inheritance of inhibitor proteins can reduce variations in cell size across individual cell-cycle phases, combining size-control mechanisms at both G1/S and G2/M is essential to maintain size homeostasis over multiple generations. Thus, our study reveals how features of the cell-cycle network enable cell-cycle progression to depend on cell size, and provides a mechanistic understanding of how plant cell populations maintain consistent size over generations.
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Affiliation(s)
- Daniel Williamson
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom
| | - William Tasker-Brown
- Cardiff School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff, United Kingdom
| | - James A. H. Murray
- Cardiff School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff, United Kingdom
| | - Angharad R. Jones
- Cardiff School of Biosciences, Cardiff University, Sir Martin Evans Building, Museum Avenue, Cardiff, United Kingdom
| | - Leah R. Band
- Centre for Mathematical Medicine and Biology, School of Mathematical Sciences, University of Nottingham, Nottingham, United Kingdom
- Division of Plant and Crop Sciences, School of Biosciences, University of Nottingham, Sutton Bonington Campus, Loughborough, United Kingdom
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14
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Gong Y, Dale R, Fung HF, Amador GO, Smit ME, Bergmann DC. A cell size threshold triggers commitment to stomatal fate in Arabidopsis. SCIENCE ADVANCES 2023; 9:eadf3497. [PMID: 37729402 PMCID: PMC10881030 DOI: 10.1126/sciadv.adf3497] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Accepted: 08/15/2023] [Indexed: 09/22/2023]
Abstract
How flexible developmental programs integrate information from internal and external factors to modulate stem cell behavior is a fundamental question in developmental biology. Cells of the Arabidopsis stomatal lineage modify the balance of stem cell proliferation and differentiation to adjust the size and cell type composition of mature leaves. Here, we report that meristemoids, one type of stomatal lineage stem cell, trigger the transition from asymmetric self-renewing divisions to commitment and terminal differentiation by crossing a critical cell size threshold. Through computational simulation, we demonstrate that this cell size-mediated transition allows robust, yet flexible termination of stem cell proliferation, and we observe adjustments in the number of divisions before the differentiation threshold under several genetic manipulations. We experimentally evaluate several mechanisms for cell size sensing, and our data suggest that this stomatal lineage transition is dependent on a nuclear factor that is sensitive to DNA content.
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Affiliation(s)
- Yan Gong
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Renee Dale
- Donald Danforth Plant Science Center, St. Louis, MO 63132 USA
| | - Hannah F. Fung
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | - Gabriel O. Amador
- Department of Developmental Biology, Stanford University, Stanford, CA 94305, USA
| | - Margot E. Smit
- Department of Biology, Stanford University, Stanford, CA 94305, USA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
| | - Dominique C. Bergmann
- Department of Biology, Stanford University, Stanford, CA 94305, USA
- Howard Hughes Medical Institute, Stanford University, Stanford, CA 94305, USA
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15
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Devany J, Falk MJ, Holt LJ, Murugan A, Gardel ML. Epithelial tissue confinement inhibits cell growth and leads to volume-reducing divisions. Dev Cell 2023; 58:1462-1476.e8. [PMID: 37339629 PMCID: PMC10528006 DOI: 10.1016/j.devcel.2023.05.018] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 05/12/2023] [Accepted: 05/26/2023] [Indexed: 06/22/2023]
Abstract
Cell proliferation is a central process in tissue development, homeostasis, and disease, yet how proliferation is regulated in the tissue context remains poorly understood. Here, we introduce a quantitative framework to elucidate how tissue growth dynamics regulate cell proliferation. Using MDCK epithelial monolayers, we show that a limiting rate of tissue expansion creates confinement that suppresses cell growth; however, this confinement does not directly affect the cell cycle. This leads to uncoupling between rates of cell growth and division in epithelia and, thereby, reduces cell volume. Division becomes arrested at a minimal cell volume, which is consistent across diverse epithelia in vivo. Here, the nucleus approaches the minimum volume capable of packaging the genome. Loss of cyclin D1-dependent cell-volume regulation results in an abnormally high nuclear-to-cytoplasmic volume ratio and DNA damage. Overall, we demonstrate how epithelial proliferation is regulated by the interplay between tissue confinement and cell-volume regulation.
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Affiliation(s)
- John Devany
- Department of Physics, The University of Chicago, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, Chicago, IL 60637, USA; Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA
| | - Martin J Falk
- Department of Physics, The University of Chicago, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, Chicago, IL 60637, USA
| | - Liam J Holt
- Institute for Systems Genetics, New York University, Grossman School of Medicine, New York, NY 10016, USA
| | - Arvind Murugan
- Department of Physics, The University of Chicago, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, Chicago, IL 60637, USA
| | - Margaret L Gardel
- Department of Physics, The University of Chicago, Chicago, IL 60637, USA; James Franck Institute, The University of Chicago, Chicago, IL 60637, USA; Institute for Biophysical Dynamics, The University of Chicago, Chicago, IL 60637, USA; Pritzker School of Molecular Engineering, The University of Chicago, Chicago, IL 60637, USA.
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16
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Miller KE, Vargas-Garcia C, Singh A, Moseley JB. The fission yeast cell size control system integrates pathways measuring cell surface area, volume, and time. Curr Biol 2023; 33:3312-3324.e7. [PMID: 37463585 PMCID: PMC10529673 DOI: 10.1016/j.cub.2023.06.054] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 06/01/2023] [Accepted: 06/20/2023] [Indexed: 07/20/2023]
Abstract
Eukaryotic cells tightly control their size, but the relevant aspect of size is unknown in most cases. Fission yeast divide at a threshold cell surface area (SA) due, in part, to the protein kinase Cdr2. We find that fission yeast cells only divide by SA under a size threshold. Mutants that divide at a larger size shift to volume-based divisions. Diploid cells divide at a larger size than haploid cells do, but they maintain SA-based divisions, and this indicates that the size threshold for changing from surface-area-based to volume-based control is set by ploidy. Within this size control system, we found that the mitotic activator Cdc25 accumulates like a volume-based sizer molecule, whereas the mitotic cyclin Cdc13 accumulates in the nucleus as a timer. We propose an integrated model for cell size control based on multiple signaling pathways that report on distinct aspects of cell size and growth, including cell SA (Cdr2), cell volume (Cdc25), and time (Cdc13). Combined modeling and experiments show how this system can generate both sizer- and adder-like properties.
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Affiliation(s)
- Kristi E Miller
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA
| | - Cesar Vargas-Garcia
- Grupo de Investigación en Sistemas Agropecuarios Sostenibles, Corporación Colombiana de Investigación Agropecuaria - AGROSAVIA, Bogotá 250047, Colombia
| | - Abhyudai Singh
- Department of Electrical and Computer Engineering, University of Delaware, Newark, DE 19716, USA
| | - James B Moseley
- Department of Biochemistry and Cell Biology, The Geisel School of Medicine at Dartmouth, Hanover, NH 03755, USA.
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17
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Carpenter LC, Pérez-Verdugo F, Banerjee S. Mechanical control of cell proliferation patterns in growing tissues. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.07.25.550581. [PMID: 37546964 PMCID: PMC10402015 DOI: 10.1101/2023.07.25.550581] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/08/2023]
Abstract
Cell proliferation plays a crucial role in regulating tissue homeostasis and development. However, our understanding of how cell proliferation is controlled in densely packed tissues is limited. Here we develop a computational framework to predict the patterns of cell proliferation in growing tissues, connecting single-cell behaviors and cell-cell interactions to tissue-level growth. Our model incorporates probabilistic rules governing cell growth, division, and elimination, while also taking into account their feedback with tissue mechanics. In particular, cell growth is suppressed and apoptosis is enhanced in regions of high cell density. With these rules and model parameters calibrated using experimental data, we predict how tissue confinement influences cell size and proliferation dynamics, and how single-cell physical properties influence the spatiotemporal patterns of tissue growth. Our findings indicate that mechanical feedback between tissue confinement and cell growth leads to enhanced cell proliferation at tissue boundaries, whereas cell growth in the bulk is arrested. By tuning cellular elasticity and contact inhibition of proliferation we can regulate the emergent patterns of cell proliferation, ranging from uniform growth at low contact inhibition to localized growth at higher contact inhibition. Furthermore, mechanical state of the tissue governs the dynamics of tissue growth, with cellular parameters affecting tissue pressure playing a significant role in determining the overall growth rate. Our computational study thus underscores the impact of cell mechanical properties on the spatiotemporal patterns of cell proliferation in growing tissues.
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Affiliation(s)
- Logan C Carpenter
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
| | | | - Shiladitya Banerjee
- Department of Physics, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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18
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Hammond T, Sage J. Monitoring the Cell Cycle of Tumor Cells in Mouse Models of Human Cancer. Cold Spring Harb Perspect Med 2023; 13:a041383. [PMID: 37460156 PMCID: PMC10691483 DOI: 10.1101/cshperspect.a041383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/27/2023]
Abstract
Cell division is obligatory to tumor growth. However, both cancer cells and noncancer cells in tumors can be found in distinct stages of the cell cycle, which may inform the growth potential of these tumors, their propensity to metastasize, and their response to therapy. Hence, it is of utmost importance to monitor the cell cycle of tumor cells. Here we discuss well-established methods and new genetic advances to track the cell cycle of tumor cells in mouse models of human cancer. We also review recent genetic studies investigating the role of the cell-cycle machinery in the growth of tumors in vivo, with a focus on the machinery regulating the G1/S transition of the cell cycle.
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Affiliation(s)
- Taylar Hammond
- Department of Pediatrics, Stanford University, Stanford, California 94305, USA
- Department of Biology, and Stanford University, Stanford, California 94305, USA
| | - Julien Sage
- Department of Pediatrics, Stanford University, Stanford, California 94305, USA
- Department of Genetics, Stanford University, Stanford, California 94305, USA
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19
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Ji X, Lin J. Implications of differential size-scaling of cell-cycle regulators on cell size homeostasis. PLoS Comput Biol 2023; 19:e1011336. [PMID: 37506170 PMCID: PMC10411824 DOI: 10.1371/journal.pcbi.1011336] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2022] [Revised: 08/09/2023] [Accepted: 07/07/2023] [Indexed: 07/30/2023] Open
Abstract
Accurate timing of division and size homeostasis is crucial for cells. A potential mechanism for cells to decide the timing of division is the differential scaling of regulatory protein copy numbers with cell size. However, it remains unclear whether such a mechanism can lead to robust growth and division, and how the scaling behaviors of regulatory proteins influence the cell size distribution. Here we study a mathematical model combining gene expression and cell growth, in which the cell-cycle activators scale superlinearly with cell size while the inhibitors scale sublinearly. The cell divides once the ratio of their concentrations reaches a threshold value. We find that the cell can robustly grow and divide within a finite range of the threshold value with the cell size proportional to the ploidy. In a stochastic version of the model, the cell size at division is uncorrelated with that at birth. Also, the more differential the cell-size scaling of the cell-cycle regulators is, the narrower the cell-size distribution is. Intriguingly, our model with multiple regulators rationalizes the observation that after the deletion of a single regulator, the coefficient of variation of cell size remains roughly the same though the average cell size changes significantly. Our work reveals that the differential scaling of cell-cycle regulators provides a robust mechanism of cell size control.
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Affiliation(s)
- Xiangrui Ji
- Yuanpei College, Peking University, Beijing, China
| | - Jie Lin
- Center for Quantitative Biology, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
- Peking-Tsinghua Center for Life Sciences, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing, China
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20
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Wang J, Fu Y, Huang W, Biswas R, Banerjee A, Broussard JA, Zhao Z, Wang D, Bjerke G, Raghavan S, Yan J, Green KJ, Yi R. MicroRNA-205 promotes hair regeneration by modulating mechanical properties of hair follicle stem cells. Proc Natl Acad Sci U S A 2023; 120:e2220635120. [PMID: 37216502 PMCID: PMC10235966 DOI: 10.1073/pnas.2220635120] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Accepted: 04/21/2023] [Indexed: 05/24/2023] Open
Abstract
Stiffness and actomyosin contractility are intrinsic mechanical properties of animal cells required for the shaping of tissues. However, whether tissue stem cells (SCs) and progenitors located within SC niche have different mechanical properties that modulate their size and function remains unclear. Here, we show that hair follicle SCs in the bulge are stiff with high actomyosin contractility and resistant to size change, whereas hair germ (HG) progenitors are soft and periodically enlarge and contract during quiescence. During activation of hair follicle growth, HGs reduce contraction and more frequently enlarge, a process that is associated with weakening of the actomyosin network, nuclear YAP accumulation, and cell cycle reentry. Induction of miR-205, a novel regulator of the actomyosin cytoskeleton, reduces actomyosin contractility and activates hair regeneration in young and old mice. This study reveals the control of tissue SC size and activities by spatiotemporally compartmentalized mechanical properties and demonstrates the possibility to stimulate tissue regeneration by fine-tuning cell mechanics.
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Affiliation(s)
- Jingjing Wang
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
| | - Yuheng Fu
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
| | - Wenmao Huang
- Mechanobiology Institute, National University of Singapore117411, Singapore
| | - Ritusree Biswas
- Institute for Stem Cell Science and Regenerative Medicine, GKVK Campus, Bangalore560065, India
| | - Avinanda Banerjee
- A*Star Skin Research Institute of Singapore, Singapore138648, Singapore
| | - Joshua A. Broussard
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Robert H. Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, IL60611
| | - Zhihai Zhao
- Mechanobiology Institute, National University of Singapore117411, Singapore
| | - Dongmei Wang
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Robert H. Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, IL60611
| | - Glen Bjerke
- Department of Molecular, Cellular and Developmental Biology, University of Colorado Boulder, Boulder, CO80309
| | - Srikala Raghavan
- Institute for Stem Cell Science and Regenerative Medicine, GKVK Campus, Bangalore560065, India
- A*Star Skin Research Institute of Singapore, Singapore138648, Singapore
| | - Jie Yan
- Mechanobiology Institute, National University of Singapore117411, Singapore
| | - Kathleen J. Green
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Robert H. Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, IL60611
| | - Rui Yi
- Department of Pathology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Department of Dermatology, Northwestern University Feinberg School of Medicine, Chicago, IL60611
- Robert H. Lurie Comprehensive Cancer Center, Northwestern University Feinberg School of Medicine, Chicago, IL60611
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21
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Lengefeld J, Zatulovskiy E. Editorial: Cell size regulation: molecular mechanisms and physiological importance. Front Cell Dev Biol 2023; 11:1219294. [PMID: 37274748 PMCID: PMC10233121 DOI: 10.3389/fcell.2023.1219294] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2023] [Accepted: 05/10/2023] [Indexed: 06/06/2023] Open
Affiliation(s)
- Jette Lengefeld
- Helsinki Institute of Life Science, HiLIFE, Institute of Biotechnology, Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
- Department of Medicine Huddinge, Center for Hematology and Regenerative Medicine, Karolinska Institutet, Stockholm, Sweden
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22
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Williams KS, Secomb TW, El-Kareh AW. An autonomous mathematical model for the mammalian cell cycle. J Theor Biol 2023; 569:111533. [PMID: 37196820 DOI: 10.1016/j.jtbi.2023.111533] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2022] [Revised: 04/04/2023] [Accepted: 05/10/2023] [Indexed: 05/19/2023]
Abstract
A mathematical model for the mammalian cell cycle is developed as a system of 13 coupled nonlinear ordinary differential equations. The variables and interactions included in the model are based on detailed consideration of available experimental data. A novel feature of the model is inclusion of cycle tasks such as origin licensing and initiation, nuclear envelope breakdown and kinetochore attachment, and their interactions with controllers (molecular complexes involved in cycle control). Other key features are that the model is autonomous, except for a dependence on external growth factors; the variables are continuous in time, without instantaneous resets at phase boundaries; mechanisms to prevent rereplication are included; and cycle progression is independent of cell size. Eight variables represent cell cycle controllers: the Cyclin D1-Cdk4/6 complex, APCCdh1, SCFβTrCP, Cdc25A, MPF, NuMA, the securin-separase complex, and separase. Five variables represent task completion, with four for the status of origins and one for kinetochore attachment. The model predicts distinct behaviors corresponding to the main phases of the cell cycle, showing that the principal features of the mammalian cell cycle, including restriction point behavior, can be accounted for in a quantitative mechanistic way based on known interactions among cycle controllers and their coupling to tasks. The model is robust to parameter changes, in that cycling is maintained over at least a five-fold range of each parameter when varied individually. The model is suitable for exploring how extracellular factors affect cell cycle progression, including responses to metabolic conditions and to anti-cancer therapies.
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Affiliation(s)
| | - Timothy W Secomb
- BIO5 Institute, University of Arizona, Tucson, AZ, USA; Department of Physiology, University of Arizona, Tucson, AZ, USA
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23
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Yokoyama Y, Kameo Y, Adachi T. Development of continuum-based particle models of cell growth and proliferation for simulating tissue morphogenesis. J Mech Behav Biomed Mater 2023; 142:105828. [PMID: 37104898 DOI: 10.1016/j.jmbbm.2023.105828] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2022] [Revised: 03/28/2023] [Accepted: 04/02/2023] [Indexed: 04/29/2023]
Abstract
Biological tissues acquire various characteristic shapes through morphogenesis. Tissue shapes result from the spatiotemporally heterogeneous cellular activities influenced by mechanical and biochemical environments. To investigate multicellular tissue morphogenesis, this study aimed to develop a novel multiscale method that can connect each cellular activity to the mechanical behaviors of the whole tissue by constructing continuum-based particle models of cellular activities. This study proposed mechanical models of cell growth and proliferation that are expressed as volume expansion and cell division by extending the material point method. By simulating cell hypertrophy and proliferation under both free and constraint conditions, the proposed models demonstrated potential for evaluating the mechanical state and tracing cells throughout tissue morphogenesis. Moreover, the effect of a cell size checkpoint was incorporated into the cell proliferation model to investigate the mechanical behaviors of the whole tissue depending on the condition of cellular activities. Consequently, the accumulation of strain energy density was suppressed because of the influence of the checkpoint. In addition, the whole tissues acquired different shapes depending on the influence of the checkpoint. Thus, the models constructed herein enabled us to investigate the change in the mechanical behaviors of the whole tissue according to each cellular activity depending on the mechanical state of the cells during morphogenesis.
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Affiliation(s)
- Yuka Yokoyama
- Department of Micro Engineering, Graduate School of Engineering, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo, Kyoto, 606-8507, Japan
| | - Yoshitaka Kameo
- Department of Micro Engineering, Graduate School of Engineering, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo, Kyoto, 606-8507, Japan; Department of Biosystems Science, Institute for Life and Medical Sciences, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo, Kyoto, 606-8507, Japan; Department of Mammalian Regulatory Network, Graduate School of Biostudies, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo, Kyoto, 606-8507, Japan
| | - Taiji Adachi
- Department of Micro Engineering, Graduate School of Engineering, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo, Kyoto, 606-8507, Japan; Department of Biosystems Science, Institute for Life and Medical Sciences, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo, Kyoto, 606-8507, Japan; Department of Mammalian Regulatory Network, Graduate School of Biostudies, Kyoto University, 53 Shogoin-Kawahara-cho, Sakyo, Kyoto, 606-8507, Japan.
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24
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Balachandra S, Sarkar S, Amodeo AA. The Nuclear-to-Cytoplasmic Ratio: Coupling DNA Content to Cell Size, Cell Cycle, and Biosynthetic Capacity. Annu Rev Genet 2022; 56:165-185. [PMID: 35977407 PMCID: PMC10165727 DOI: 10.1146/annurev-genet-080320-030537] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Though cell size varies between different cells and across species, the nuclear-to-cytoplasmic (N/C) ratio is largely maintained across species and within cell types. A cell maintains a relatively constant N/C ratio by coupling DNA content, nuclear size, and cell size. We explore how cells couple cell division and growth to DNA content. In some cases, cells use DNA as a molecular yardstick to control the availability of cell cycle regulators. In other cases, DNA sets a limit for biosynthetic capacity. Developmentally programmed variations in the N/C ratio for a given cell type suggest that a specific N/C ratio is required to respond to given physiological demands. Recent observations connecting decreased N/C ratios with cellular senescence indicate that maintaining the proper N/C ratio is essential for proper cellular functioning. Together, these findings suggest a causative, not simply correlative, role for the N/C ratio in regulating cell growth and cell cycle progression.
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Affiliation(s)
- Shruthi Balachandra
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA; ,
| | - Sharanya Sarkar
- Department of Microbiology and Immunology, Dartmouth College, Hanover, New Hampshire, USA;
| | - Amanda A Amodeo
- Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA; ,
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25
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Davies DM, van den Handel K, Bharadwaj S, Lengefeld J. Cellular enlargement - A new hallmark of aging? Front Cell Dev Biol 2022; 10:1036602. [PMID: 36438561 PMCID: PMC9688412 DOI: 10.3389/fcell.2022.1036602] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2022] [Accepted: 10/17/2022] [Indexed: 12/03/2023] Open
Abstract
Years of important research has revealed that cells heavily invest in regulating their size. Nevertheless, it has remained unclear why accurate size control is so important. Our recent study using hematopoietic stem cells (HSCs) in vivo indicates that cellular enlargement is causally associated with aging. Here, we present an overview of these findings and their implications. Furthermore, we performed a broad literature analysis to evaluate the potential of cellular enlargement as a new aging hallmark and to examine its connection to previously described aging hallmarks. Finally, we highlight interesting work presenting a correlation between cell size and age-related diseases. Taken together, we found mounting evidence linking cellular enlargement to aging and age-related diseases. Therefore, we encourage researchers from seemingly unrelated areas to take a fresh look at their data from the perspective of cell size.
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Affiliation(s)
- Daniel M. Davies
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Kim van den Handel
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Soham Bharadwaj
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Jette Lengefeld
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
- Center for Hematology and Regenerative Medicine, Department of Medicine Huddinge, Karolinska Institutet, Stockholm, Sweden
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26
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Liu S, Tan C, Tyers M, Zetterberg A, Kafri R. What programs the size of animal cells? Front Cell Dev Biol 2022; 10:949382. [PMID: 36393871 PMCID: PMC9665425 DOI: 10.3389/fcell.2022.949382] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2022] [Accepted: 09/07/2022] [Indexed: 01/19/2023] Open
Abstract
The human body is programmed with definite quantities, magnitudes, and proportions. At the microscopic level, such definite sizes manifest in individual cells - different cell types are characterized by distinct cell sizes whereas cells of the same type are highly uniform in size. How do cells in a population maintain uniformity in cell size, and how are changes in target size programmed? A convergence of recent and historical studies suggest - just as a thermostat maintains room temperature - the size of proliferating animal cells is similarly maintained by homeostatic mechanisms. In this review, we first summarize old and new literature on the existence of cell size checkpoints, then discuss additional advances in the study of size homeostasis that involve feedback regulation of cellular growth rate. We further discuss recent progress on the molecules that underlie cell size checkpoints and mechanisms that specify target size setpoints. Lastly, we discuss a less-well explored teleological question: why does cell size matter and what is the functional importance of cell size control?
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Affiliation(s)
- Shixuan Liu
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
- Program in Cell Biology, The Hospital for Sick Children, Toronto, ON, Canada
- Department of Chemical and Systems Biology, Stanford University, Stanford, CA, United States
| | - Ceryl Tan
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
- Program in Cell Biology, The Hospital for Sick Children, Toronto, ON, Canada
| | - Mike Tyers
- Institute for Research in Immunology and Cancer, University of Montréal, Montréal, QC, Canada
| | - Anders Zetterberg
- Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden
| | - Ran Kafri
- Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada
- Program in Cell Biology, The Hospital for Sick Children, Toronto, ON, Canada
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27
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Øvrebø JI, Ma Y, Edgar BA. Cell growth and the cell cycle: New insights about persistent questions. Bioessays 2022; 44:e2200150. [PMID: 36222263 DOI: 10.1002/bies.202200150] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Revised: 09/12/2022] [Accepted: 09/13/2022] [Indexed: 11/08/2022]
Abstract
Before a cell divides into two daughter cells, it typically doubles not only its DNA, but also its mass. Numerous studies in cells ranging from yeast to mammals have shown that cellular growth, stimulated by nutrients and/or growth factor signaling, is a prerequisite for cell cycle progression in most types of cells. The textbook view of growth-regulated cell cycles is that growth signaling activates the transcription of G1 Cyclin genes to induce cell proliferation, and also stimulates anabolic metabolism and cell growth in parallel. However, genetic knockout tests in model organisms indicate that this is not the whole story, and new studies show that additional, "smarter" mechanisms help to coordinate the cell cycle with growth itself. Here we summarize recent advances in this field, and discuss current models in which growth signaling regulates cell proliferation by targeting core cell cycle regulators via non-transcriptional mechanisms.
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Affiliation(s)
- Jan Inge Øvrebø
- Computational Biology Unit, Department of Informatics, University of Bergen, Bergen, Norway
| | - Yiqin Ma
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah, USA
| | - Bruce A Edgar
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah, USA
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28
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Abstract
The most fundamental feature of cellular form is size, which sets the scale of all cell biological processes. Growth, form, and function are all necessarily linked in cell biology, but we often do not understand the underlying molecular mechanisms nor their specific functions. Here, we review progress toward determining the molecular mechanisms that regulate cell size in yeast, animals, and plants, as well as progress toward understanding the function of cell size regulation. It has become increasingly clear that the mechanism of cell size regulation is deeply intertwined with basic mechanisms of biosynthesis, and how biosynthesis can be scaled (or not) in proportion to cell size. Finally, we highlight recent findings causally linking aberrant cell size regulation to cellular senescence and their implications for cancer therapies.
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Affiliation(s)
- Shicong Xie
- Department of Biology, Stanford University, Stanford, California, USA;
| | - Matthew Swaffer
- Department of Biology, Stanford University, Stanford, California, USA;
| | - Jan M Skotheim
- Department of Biology, Stanford University, Stanford, California, USA;
- Chan Zuckerberg Biohub, San Francisco, California, USA
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29
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Yamamoto T, Cockburn K, Greco V, Kawaguchi K. Probing the rules of cell coordination in live tissues by interpretable machine learning based on graph neural networks. PLoS Comput Biol 2022; 18:e1010477. [PMID: 36067226 PMCID: PMC9481156 DOI: 10.1371/journal.pcbi.1010477] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2022] [Revised: 09/16/2022] [Accepted: 08/09/2022] [Indexed: 11/18/2022] Open
Abstract
Robustness in developing and homeostatic tissues is supported by various types of spatiotemporal cell-to-cell interactions. Although live imaging and cell tracking are powerful in providing direct evidence of cell coordination rules, extracting and comparing these rules across many tissues with potentially different length and timescales of coordination requires a versatile framework of analysis. Here we demonstrate that graph neural network (GNN) models are suited for this purpose, by showing how they can be applied to predict cell fate in tissues and utilized to infer the cell interactions governing the multicellular dynamics. Analyzing the live mammalian epidermis data, where spatiotemporal graphs constructed from cell tracks and cell contacts are given as inputs, GNN discovers distinct neighbor cell fate coordination rules that depend on the region of the body. This approach demonstrates how the GNN framework is powerful in inferring general cell interaction rules from live data without prior knowledge of the signaling involved.
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Affiliation(s)
- Takaki Yamamoto
- Nonequilibrium Physics of Living Matter RIKEN Hakubi Research Team, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
| | - Katie Cockburn
- Department of Genetics, Yale School of Medicine, New Haven, Connecticut, United States of America
- Department of Biochemistry and Rosalind & Morris Goodman Cancer Institute, McGill University, Montreal, Quebec, Canada
| | - Valentina Greco
- Department of Genetics, Yale School of Medicine, New Haven, Connecticut, United States of America
- Departments of Cell Biology and Dermatology, Yale Stem Cell Center, Yale Cancer Center, Yale School of Medicine, New Haven, Connecticut, United States of America
| | - Kyogo Kawaguchi
- Nonequilibrium Physics of Living Matter RIKEN Hakubi Research Team, RIKEN Center for Biosystems Dynamics Research, Kobe, Japan
- RIKEN Cluster for Pioneering Research, Kobe, Japan
- Universal Biology Institute, The University of Tokyo, Tokyo, Japan
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30
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Cadart C, Heald R. Scaling of biosynthesis and metabolism with cell size. Mol Biol Cell 2022; 33:pe5. [PMID: 35862496 PMCID: PMC9582640 DOI: 10.1091/mbc.e21-12-0627] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Revised: 05/24/2022] [Accepted: 05/25/2022] [Indexed: 11/17/2022] Open
Abstract
Cells adopt a size that is optimal for their function, and pushing them beyond this limit can cause cell aging and death by senescence or reduce proliferative potential. However, by increasing their genome copy number (ploidy), cells can increase their size dramatically and homeostatically maintain physiological properties such as biosynthesis rate. Recent studies investigating the relationship between cell size and rates of biosynthesis and metabolism under normal, polyploid, and pathological conditions are revealing new insights into how cells attain the best function or fitness for their size by tuning processes including transcription, translation, and mitochondrial respiration. A new frontier is to connect single-cell scaling relationships with tissue and whole-organism physiology, which promises to reveal molecular and evolutionary principles underlying the astonishing diversity of size observed across the tree of life.
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Affiliation(s)
- Clotilde Cadart
- Molecular and Cell Biology Department, University of California, Berkeley, Berkeley, CA 94720-3200
| | - Rebecca Heald
- Molecular and Cell Biology Department, University of California, Berkeley, Berkeley, CA 94720-3200
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31
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Stojanovski K, Großhans H, Towbin BD. Coupling of growth rate and developmental tempo reduces body size heterogeneity in C. elegans. Nat Commun 2022; 13:3132. [PMID: 35668054 PMCID: PMC9170734 DOI: 10.1038/s41467-022-29720-8] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2021] [Accepted: 03/24/2022] [Indexed: 11/15/2022] Open
Abstract
Animals increase by orders of magnitude in volume during development. Therefore, small variations in growth rates among individuals could amplify to a large heterogeneity in size. By live imaging of C. elegans, we show that amplification of size heterogeneity is prevented by an inverse coupling of the volume growth rate to the duration of larval stages and does not involve strict size thresholds for larval moulting. We perturb this coupling by changing the developmental tempo through manipulation of a transcriptional oscillator that controls the duration of larval development. As predicted by a mathematical model, this perturbation alters the body volume. Model analysis shows that an inverse relation between the period length and the growth rate is an intrinsic property of genetic oscillators and can occur independently of additional complex regulation. This property of genetic oscillators suggests a parsimonious mechanism that counteracts the amplification of size differences among individuals during development. Animals must reach the correct size during development, despite stochastic differences in their growth rate. Here, Stojanovski et al. show that a coupling of growth and development by an oscillatory timer buffers fluctuations in the growth of the nematode C. elegans to ensure its correct size.
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Affiliation(s)
| | - Helge Großhans
- Friedrich Miescher Institute for Biomedical Research (FMI), Basel, Switzerland. .,University of Basel, Basel, Switzerland.
| | - Benjamin D Towbin
- University of Bern, Bern, Switzerland. .,Friedrich Miescher Institute for Biomedical Research (FMI), Basel, Switzerland.
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32
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Molina A, Bonnet F, Pignolet J, Lobjois V, Bel-Vialar S, Gautrais J, Pituello F, Agius E. Single-cell imaging of the cell cycle reveals CDC25B-induced heterogeneity of G1 phase length in neural progenitor cells. Development 2022; 149:275468. [DOI: 10.1242/dev.199660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2021] [Accepted: 04/27/2022] [Indexed: 11/20/2022]
Abstract
ABSTRACT
Although lengthening of the cell cycle and G1 phase is a generic feature of tissue maturation during development, the underlying mechanism remains poorly understood. Here, we develop a time-lapse imaging strategy to measure the four cell cycle phases in single chick neural progenitor cells in their endogenous environment. We show that neural progenitors are widely heterogeneous with respect to cell cycle length. This variability in duration is distributed over all phases of the cell cycle, with the G1 phase contributing the most. Within one cell cycle, each phase duration appears stochastic and independent except for a correlation between S and M phase duration. Lineage analysis indicates that the majority of daughter cells may have a longer G1 phase than mother cells, suggesting that, at each cell cycle, a mechanism lengthens the G1 phase. We identify that the CDC25B phosphatase known to regulate the G2/M transition indirectly increases the duration of the G1 phase, partly through delaying passage through the restriction point. We propose that CDC25B increases the heterogeneity of G1 phase length, revealing a previously undescribed mechanism of G1 lengthening that is associated with tissue development.
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Affiliation(s)
- Angie Molina
- Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III – Paul Sabatier 1 Unité de Biologie Moléculaire, Cellulaire et du Développement (MCD) , , Toulouse 31062 CEDEX 9 , France
| | - Frédéric Bonnet
- Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III – Paul Sabatier 1 Unité de Biologie Moléculaire, Cellulaire et du Développement (MCD) , , Toulouse 31062 CEDEX 9 , France
| | - Julie Pignolet
- Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III – Paul Sabatier 1 Unité de Biologie Moléculaire, Cellulaire et du Développement (MCD) , , Toulouse 31062 CEDEX 9 , France
| | - Valerie Lobjois
- Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III – Paul Sabatier 1 Unité de Biologie Moléculaire, Cellulaire et du Développement (MCD) , , Toulouse 31062 CEDEX 9 , France
| | - Sophie Bel-Vialar
- Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III – Paul Sabatier 1 Unité de Biologie Moléculaire, Cellulaire et du Développement (MCD) , , Toulouse 31062 CEDEX 9 , France
| | - Jacques Gautrais
- Centre de Recherches sur la Cognition Animale (CRCA), Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III – Paul Sabatier 2 , Toulouse 31062 CEDEX 9 , France
| | - Fabienne Pituello
- Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III – Paul Sabatier 1 Unité de Biologie Moléculaire, Cellulaire et du Développement (MCD) , , Toulouse 31062 CEDEX 9 , France
| | - Eric Agius
- Centre de Biologie Intégrative (CBI), Université de Toulouse, CNRS, Université Toulouse III – Paul Sabatier 1 Unité de Biologie Moléculaire, Cellulaire et du Développement (MCD) , , Toulouse 31062 CEDEX 9 , France
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33
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Pérez AP, Artés MH, Moreno DF, Clotet J, Aldea M. Mad3 modulates the G 1 Cdk and acts as a timer in the Start network. SCIENCE ADVANCES 2022; 8:eabm4086. [PMID: 35522754 PMCID: PMC9075807 DOI: 10.1126/sciadv.abm4086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/25/2021] [Accepted: 03/23/2022] [Indexed: 06/14/2023]
Abstract
Cells maintain their size within limits over successive generations to maximize fitness and survival. Sizer, timer, and adder behaviors have been proposed as possible alternatives to coordinate growth and cell cycle progression. Regarding budding yeast cells, a sizer mechanism is thought to rule cell cycle entry at Start. However, while many proteins controlling the size of these cells have been identified, the mechanistic framework in which they participate to achieve cell size homeostasis is not understood. We show here that intertwined APC and SCF degradation machineries with specific adaptor proteins drive cyclic accumulation of the G1 Cdk in the nucleus, reaching maximal levels at Start. The mechanism incorporates Mad3, a centromeric-signaling protein that subordinates G1 progression to the previous mitosis as a memory factor. This alternating-degradation device displays the properties of a timer and, together with the sizer device, would constitute a key determinant of cell cycle entry.
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Affiliation(s)
- Alexis P. Pérez
- Molecular Biology Institute of Barcelona (IBMB), CSIC, 08028 Barcelona, Catalonia, Spain
- Department of Basic Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Spain
| | - Marta H. Artés
- Molecular Biology Institute of Barcelona (IBMB), CSIC, 08028 Barcelona, Catalonia, Spain
| | - David F. Moreno
- Molecular Biology Institute of Barcelona (IBMB), CSIC, 08028 Barcelona, Catalonia, Spain
| | - Josep Clotet
- Department of Basic Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Spain
| | - Martí Aldea
- Molecular Biology Institute of Barcelona (IBMB), CSIC, 08028 Barcelona, Catalonia, Spain
- Department of Basic Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Spain
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34
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Oh S, Lee C, Yang W, Li A, Mukherjee A, Basan M, Ran C, Yin W, Tabin CJ, Fu D, Xie XS, Kirschner MW. Protein and lipid mass concentration measurement in tissues by stimulated Raman scattering microscopy. Proc Natl Acad Sci U S A 2022; 119:e2117938119. [PMID: 35452314 PMCID: PMC9169924 DOI: 10.1073/pnas.2117938119] [Citation(s) in RCA: 41] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Accepted: 02/21/2022] [Indexed: 01/10/2023] Open
Abstract
Cell mass and chemical composition are important aggregate cellular properties that are especially relevant to physiological processes, such as growth control and tissue homeostasis. Despite their importance, it has been difficult to measure these features quantitatively at the individual cell level in intact tissue. Here, we introduce normalized Raman imaging (NoRI), a stimulated Raman scattering (SRS) microscopy method that provides the local concentrations of protein, lipid, and water from live or fixed tissue samples with high spatial resolution. Using NoRI, we demonstrate that protein, lipid, and water concentrations at the single cell are maintained in a tight range in cells under the same physiological conditions and are altered in different physiological states, such as cell cycle stages, attachment to substrates of different stiffness, or by entering senescence. In animal tissues, protein and lipid concentration varies with cell types, yet an unexpected cell-to-cell heterogeneity was found in cerebellar Purkinje cells. The protein and lipid concentration profile provides means to quantitatively compare disease-related pathology, as demonstrated using models of Alzheimer’s disease. This demonstration shows that NoRI is a broadly applicable technique for probing the biological regulation of protein mass, lipid mass, and water mass for studies of cellular and tissue growth, homeostasis, and disease.
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Affiliation(s)
- Seungeun Oh
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - ChangHee Lee
- Department of Genetics, Harvard Medical School, Boston, MA 02115
| | - Wenlong Yang
- Center for Advanced Imaging, Harvard University, Cambridge, MA 20138
| | - Ang Li
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Avik Mukherjee
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Markus Basan
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
| | - Chongzhao Ran
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02129
| | - Wei Yin
- Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Boston, MA 02129
| | | | - Dan Fu
- Department of Chemistry, University of Washington, Seattle, WA 98195
| | - X. Sunney Xie
- Biomedical Pioneering Innovation Center, Peking University, Beijing 100871; China
| | - Marc W. Kirschner
- Department of Systems Biology, Harvard Medical School, Boston, MA 02115
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35
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Goodman MB, Savage-Dunn C. Reciprocal interactions between transforming growth factor beta signaling and collagens: Insights from Caenorhabditis elegans. Dev Dyn 2022; 251:47-60. [PMID: 34537996 PMCID: PMC8982858 DOI: 10.1002/dvdy.423] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2021] [Revised: 09/13/2021] [Accepted: 09/13/2021] [Indexed: 01/03/2023] Open
Abstract
Studies in genetically tractable organisms such as the nematode Caenorhabditis elegans have led to pioneering insights into conserved developmental regulatory mechanisms. For example, Smad signal transducers for the transforming growth factor beta (TGF-β) superfamily were first identified in C. elegans and in the fruit fly Drosophila. Recent studies of TGF-β signaling and the extracellular matrix (ECM) in C. elegans have forged unexpected links between signaling and the ECM, yielding novel insights into the reciprocal interactions that occur across tissues and spatial scales, and potentially providing new opportunities for the study of biomechanical regulation of gene expression.
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Affiliation(s)
- Miriam B. Goodman
- Department of Molecular and Cellular Physiology, Stanford University, CA 94304
| | - Cathy Savage-Dunn
- Department of Biology, Queens College at the City University of New York, 11367,Correspondence to: >
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36
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Lengefeld J, Cheng CW, Maretich P, Blair M, Hagen H, McReynolds MR, Sullivan E, Majors K, Roberts C, Kang JH, Steiner JD, Miettinen TP, Manalis SR, Antebi A, Morrison SJ, Lees JA, Boyer LA, Yilmaz ÖH, Amon A. Cell size is a determinant of stem cell potential during aging. SCIENCE ADVANCES 2021; 7:eabk0271. [PMID: 34767451 PMCID: PMC8589318 DOI: 10.1126/sciadv.abk0271] [Citation(s) in RCA: 58] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2021] [Accepted: 09/24/2021] [Indexed: 05/05/2023]
Abstract
Stem cells are remarkably small. Whether small size is important for stem cell function is unknown. We find that hematopoietic stem cells (HSCs) enlarge under conditions known to decrease stem cell function. This decreased fitness of large HSCs is due to reduced proliferation and was accompanied by altered metabolism. Preventing HSC enlargement or reducing large HSCs in size averts the loss of stem cell potential under conditions causing stem cell exhaustion. Last, we show that murine and human HSCs enlarge during aging. Preventing this age-dependent enlargement improves HSC function. We conclude that small cell size is important for stem cell function in vivo and propose that stem cell enlargement contributes to their functional decline during aging.
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Affiliation(s)
- Jette Lengefeld
- David H. Koch Institute for Integrative Cancer Research, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
- Institute of Biotechnology, HiLIFE, University of Helsinki, Helsinki, Finland
| | - Chia-Wei Cheng
- David H Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Pema Maretich
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Marguerite Blair
- David H Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Hannah Hagen
- David H Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Melanie R. McReynolds
- Department of Chemistry, Princeton University, Princeton, NJ, USA
- Lewis-Sigler Institute for Integrative Genomics, Princeton, NJ, USA
| | - Emily Sullivan
- David H Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Kyra Majors
- David H Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Christina Roberts
- Max Planck Institute for Biology of Ageing and CECAD, University of Cologne, Cologne, Germany
| | - Joon Ho Kang
- David H Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Joachim D. Steiner
- Max Planck Institute for Biology of Ageing and CECAD, University of Cologne, Cologne, Germany
- Department II of Internal Medicine, University of Cologne, Faculty of Medicine and University Hospital Cologne, Cologne, Germany
| | - Teemu P. Miettinen
- David H Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
- MRC Laboratory for Molecular Cell Biology, University College London, London, UK
| | - Scott R. Manalis
- David H Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Adam Antebi
- Max Planck Institute for Biology of Ageing and CECAD, University of Cologne, Cologne, Germany
| | - Sean J. Morrison
- Children’s Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Jacqueline A. Lees
- David H Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Laurie A. Boyer
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Ömer H. Yilmaz
- David H Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Angelika Amon
- David H. Koch Institute for Integrative Cancer Research, Howard Hughes Medical Institute, Massachusetts Institute of Technology, Cambridge, MA, USA
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, USA
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37
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Abstract
A fundamental and still mysterious question in cell biology is "How do cells know how big they are?". The fact that they do is evident from the strict maintenance of size homeostasis within populations of cells and has been verified by a variety of creative experiments over the past 100 years. An increasingly sophisticated understanding of cell-cycle-control mechanisms and innovations in cell imaging and analysis tools have allowed recent progress in proposing and testing models of cell-size control. Nonetheless, a biochemical understanding of how proposed cell-size mechanisms might work is only beginning to be developed. This primer introduces the field of cell-size control and discusses some of the questions that are yet to be answered.
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Affiliation(s)
- Nicholas Rhind
- Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, 364 Plantation Street, Worcester, MA 01605, USA.
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38
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Tanaka M, Kitanishi-Yumura T, Yumura S. A 'dynamic adder model' for cell size homeostasis in Dictyostelium cells. Sci Rep 2021; 11:13742. [PMID: 34215778 PMCID: PMC8253765 DOI: 10.1038/s41598-021-92700-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2021] [Accepted: 06/15/2021] [Indexed: 02/06/2023] Open
Abstract
After a cell divides into two daughter cells, the total cell surface area of the daughter cells should increase to the original size to maintain cell size homeostasis in a single cell cycle. Previously, three models have been proposed to explain the regulation of cell size homeostasis: sizer, timer, and adder models. Here, we precisely measured the total cell surface area of Dictyostelium cells in a whole cell cycle by using the agar-overlay method, which eliminated the influence of surface membrane reservoirs, such as microvilli and membrane wrinkles. The total cell surface area exponentially increased during interphase, slightly decreased at metaphase, and then increased by approximately 20% during cytokinesis. From the analysis of the added surface area, we concluded that the cell size was regulated by the adder or near-adder model in interphase. This adder model is not caused by a simple cell membrane addition, but is more dynamic due to the rapid cell membrane turnover. We propose a 'dynamic adder model' to explain cell size homeostasis in interphase.
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Affiliation(s)
- Masahito Tanaka
- grid.268397.10000 0001 0660 7960Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, 753-8512 Japan ,grid.288127.60000 0004 0466 9350Present Address: Laboratory of Physics and Cell Biology, Department of Chromosome Science, National Institute of Genetics, 1111 Yata, Mishima, Shizuoka 411-8540 Japan
| | - Toshiko Kitanishi-Yumura
- grid.268397.10000 0001 0660 7960Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, 753-8512 Japan
| | - Shigehiko Yumura
- grid.268397.10000 0001 0660 7960Graduate School of Sciences and Technology for Innovation, Yamaguchi University, Yamaguchi, 753-8512 Japan
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39
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Tan C, Ginzberg MB, Webster R, Iyengar S, Liu S, Papadopoli D, Concannon J, Wang Y, Auld DS, Jenkins JL, Rost H, Topisirovic I, Hilfinger A, Derry WB, Patel N, Kafri R. Cell size homeostasis is maintained by CDK4-dependent activation of p38 MAPK. Dev Cell 2021; 56:1756-1769.e7. [PMID: 34022133 DOI: 10.1016/j.devcel.2021.04.030] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Revised: 02/08/2021] [Accepted: 04/28/2021] [Indexed: 02/07/2023]
Abstract
While molecules that promote the growth of animal cells have been identified, it remains unclear how such signals are orchestrated to determine a characteristic target size for different cell types. It is increasingly clear that cell size is determined by size checkpoints-mechanisms that restrict the cell cycle progression of cells that are smaller than their target size. Previously, we described a p38 MAPK-dependent cell size checkpoint mechanism whereby p38 is selectively activated and prevents cell cycle progression in cells that are smaller than a given target size. In this study, we show that the specific target size required for inactivation of p38 and transition through the cell cycle is determined by CDK4 activity. Our data suggest a model whereby p38 and CDK4 cooperate analogously to the function of a thermostat: while p38 senses irregularities in size, CDK4 corresponds to the thermostat dial that sets the target size.
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Affiliation(s)
- Ceryl Tan
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1A8, Canada; Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Miriam B Ginzberg
- Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Rachel Webster
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1A8, Canada; Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Seshu Iyengar
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, ON L5L 1C6, Canada
| | - Shixuan Liu
- Chemical and Systems Biology, Stanford University, Stanford, CA 94305, USA
| | - David Papadopoli
- Gerald Bronfman Department of Oncology and Lady Davis Institute, McGill University Montreal, QC H4A 3T2, Canada
| | - John Concannon
- Novartis Institutes for BioMedical Research, Cambridge, MA 02139, USA
| | - Yuan Wang
- Novartis Institutes for BioMedical Research, Cambridge, MA 02139, USA
| | - Douglas S Auld
- Novartis Institutes for BioMedical Research, Cambridge, MA 02139, USA
| | - Jeremy L Jenkins
- Novartis Institutes for BioMedical Research, Cambridge, MA 02139, USA
| | - Hannes Rost
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1A8, Canada
| | - Ivan Topisirovic
- Gerald Bronfman Department of Oncology and Lady Davis Institute, McGill University Montreal, QC H4A 3T2, Canada
| | - Andreas Hilfinger
- Department of Chemical and Physical Sciences, University of Toronto Mississauga, ON L5L 1C6, Canada
| | - W Brent Derry
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1A8, Canada; Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Nish Patel
- Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada
| | - Ran Kafri
- Department of Molecular Genetics, University of Toronto, Toronto, ON M5G 1A8, Canada; Cell Biology, The Hospital for Sick Children, Toronto, ON M5G 0A4, Canada.
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Rice G, Rompolas P. Advances in resolving the heterogeneity and dynamics of keratinocyte differentiation. Curr Opin Cell Biol 2020; 67:92-98. [PMID: 33091828 PMCID: PMC7736530 DOI: 10.1016/j.ceb.2020.09.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 09/15/2020] [Accepted: 09/16/2020] [Indexed: 02/07/2023]
Abstract
The mammalian skin is equipped with a highly dynamic stratified epithelium. The maintenance and regeneration of this epithelium is supported by basally located keratinocytes, which display stem cell properties, including lifelong proliferative potential and the ability to undergo diverse differentiation trajectories. Keratinocytes support not just the surface of the skin, called the epidermis, but also a range of ectodermal structures including hair follicles, sebaceous glands, and sweat glands. Recent studies have shed light on the hitherto underappreciated heterogeneity of keratinocytes by employing state-of-the-art imaging technologies and single-cell genomic approaches. In this mini review, we highlight major recent discoveries that illuminate the dynamics and cellular mechanisms that govern keratinocyte differentiation in the live mammalian skin and discuss the broader implications of these findings for our understanding of epithelial and stem cell biology in general.
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Affiliation(s)
- Gabriella Rice
- Department of Dermatology, Institute for Regenerative Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA
| | - Panteleimon Rompolas
- Department of Dermatology, Institute for Regenerative Medicine, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA, 19104, USA.
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Nagy Z, Medgyes-Horváth A, Vörös E, Sveiczer Á. Strongly oversized fission yeast cells lack any size control and tend to grow linearly rather than bilinearly. Yeast 2020; 38:206-221. [PMID: 33244789 DOI: 10.1002/yea.3535] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2020] [Revised: 10/26/2020] [Accepted: 11/02/2020] [Indexed: 12/28/2022] Open
Abstract
During the mitotic cycle, the rod-shaped fission yeast cells grow only at their tips. The newly born cells grow first unipolarly at their old end, but later in the cycle, the 'new end take-off' event occurs, resulting in bipolar growth. Photographs were taken of several steady-state and induction synchronous cultures of different cell cycle mutants of fission yeast, generally larger than wild type. Length measurements of many individual cells were performed from birth to division. For all the measured growth patterns, three different functions (linear, bilinear and exponential) were fitted, and the most adequate one was chosen by using specific statistical criteria, considering the altering parameter numbers. Although the growth patterns were heterogeneous in all the cultures studied, we could find some tendencies. In cultures with sufficiently wide size distribution, cells large enough at birth tend to grow linearly, whereas the other cells generally tend to grow bilinearly. We have found that among bilinearly growing cells, the larger they are at birth, the rate change point during their bilinear pattern occurs earlier in the cycle. This shifting near to the beginning of the cycle might finally cause a linear pattern, if the cells are even larger. In all of the steady-state cultures studied, a size control mechanism operates to maintain homeostasis. By contrast, strongly oversized cells of induction synchronous cultures lack any sizer, and their cycle rather behaves like an adder. We could determine the critical cell size for both the G1 and G2 size controls, where these mechanisms become cryptic. TAKE AWAY: Most individual fission yeast cells in steady-state cultures grow bilinearly. In strongly oversized fission yeast cells, linear growth dominates over bilinear. Above birth length thresholds, both the G1 and G2 size controls become cryptic.
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Affiliation(s)
- Zsófia Nagy
- Department of Applied Biotechnology and Food Science, Budapest University of Technology and Economics, Budapest, Hungary
| | - Anna Medgyes-Horváth
- Department of Applied Biotechnology and Food Science, Budapest University of Technology and Economics, Budapest, Hungary
| | - Eszter Vörös
- Department of Applied Biotechnology and Food Science, Budapest University of Technology and Economics, Budapest, Hungary
| | - Ákos Sveiczer
- Department of Applied Biotechnology and Food Science, Budapest University of Technology and Economics, Budapest, Hungary
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Integrating Old and New Paradigms of G1/S Control. Mol Cell 2020; 80:183-192. [PMID: 32946743 DOI: 10.1016/j.molcel.2020.08.020] [Citation(s) in RCA: 142] [Impact Index Per Article: 35.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 08/17/2020] [Accepted: 08/26/2020] [Indexed: 12/13/2022]
Abstract
The Cdk-Rb-E2F pathway integrates external and internal signals to control progression at the G1/S transition of the mammalian cell cycle. Alterations in this pathway are found in most human cancers, and specific cyclin-dependent kinase Cdk4/6 inhibitors are approved or in clinical trials for the treatment of diverse cancers. In the long-standing paradigm for G1/S control, Cdks inactivate the retinoblastoma tumor suppressor protein (Rb) through phosphorylation, which releases E2F transcription factors to drive cell-cycle progression from G1 to S. However, recent observations in the laboratory and clinic challenge central tenets of the current paradigm and demonstrate that our understanding of the Rb pathway and G1/S control is still incomplete. Here, we integrate these new findings with the previous paradigm to synthesize a current molecular and cellular view of the mammalian G1/S transition. A more complete and accurate understanding of G1/S control will lead to improved therapeutic strategies targeting the cell cycle in cancer.
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Zatulovskiy E, Zhang S, Berenson DF, Topacio BR, Skotheim JM. Cell growth dilutes the cell cycle inhibitor Rb to trigger cell division. Science 2020; 369:466-471. [PMID: 32703881 PMCID: PMC7489475 DOI: 10.1126/science.aaz6213] [Citation(s) in RCA: 74] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2019] [Accepted: 05/19/2020] [Indexed: 12/21/2022]
Abstract
Cell size is fundamental to cell physiology. For example, cell size determines the spatial scale of organelles and intracellular transport and thereby affects biosynthesis. Although some genes that affect mammalian cell size have been identified, the molecular mechanisms through which cell growth drives cell division have remained elusive. We show that cell growth during the G1 phase of the cell division cycle dilutes the cell cycle inhibitor Retinoblastoma protein (Rb) to trigger division in human cells. RB overexpression increased cell size and G1 duration, whereas RB deletion decreased cell size and removed the inverse correlation between cell size at birth and the duration of the G1 phase. Thus, Rb dilution through cell growth in G1 provides one of the long-sought molecular mechanisms that promotes cell size homeostasis.
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Affiliation(s)
| | - Shuyuan Zhang
- Department of Biology, Stanford University, Stanford, CA 94305, USA
| | | | | | - Jan M Skotheim
- Department of Biology, Stanford University, Stanford, CA 94305, USA.
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Abstract
In the study of bacterial growth, the prevailing conclusion is that cells grow exponentially at a constant rate throughout the cell cycle. Using a new approach, Nordholt et al. reveal that bacterial growth is biphasic; immediately after division, the cell grows linearly, transitioning to exponential growth towards the end of the cell cycle.
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