1
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Sundaram MV, Pujol N. The Caenorhabditis elegans cuticle and precuticle: a model for studying dynamic apical extracellular matrices in vivo. Genetics 2024; 227:iyae072. [PMID: 38995735 PMCID: PMC11304992 DOI: 10.1093/genetics/iyae072] [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: 12/14/2023] [Accepted: 03/25/2024] [Indexed: 07/14/2024] Open
Abstract
Apical extracellular matrices (aECMs) coat the exposed surfaces of animal bodies to shape tissues, influence social interactions, and protect against pathogens and other environmental challenges. In the nematode Caenorhabditis elegans, collagenous cuticle and zona pellucida protein-rich precuticle aECMs alternately coat external epithelia across the molt cycle and play many important roles in the worm's development, behavior, and physiology. Both these types of aECMs contain many matrix proteins related to those in vertebrates, as well as some that are nematode-specific. Extensive differences observed among tissues and life stages demonstrate that aECMs are a major feature of epithelial cell identity. In addition to forming discrete layers, some cuticle components assemble into complex substructures such as ridges, furrows, and nanoscale pillars. The epidermis and cuticle are mechanically linked, allowing the epidermis to sense cuticle damage and induce protective innate immune and stress responses. The C. elegans model, with its optical transparency, facilitates the study of aECM cell biology and structure/function relationships and all the myriad ways by which aECM can influence an organism.
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Affiliation(s)
- Meera V Sundaram
- Department of Genetics, University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA
| | - Nathalie Pujol
- Aix Marseille University, INSERM, CNRS, CIML, Turing Centre for Living Systems, 13009 Marseille, France
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2
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Essmann CL, Elmi M, Rekatsinas C, Chrysochoidis N, Shaw M, Pawar V, Srinivasan MA, Vavourakis V. The influence of internal pressure and neuromuscular agents on C. elegans biomechanics: an empirical and multi-compartmental in silico modelling study. Front Bioeng Biotechnol 2024; 12:1335788. [PMID: 38558792 PMCID: PMC10978802 DOI: 10.3389/fbioe.2024.1335788] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2023] [Accepted: 02/20/2024] [Indexed: 04/04/2024] Open
Abstract
The function of a specific tissue and its biomechanics are interdependent, with pathologies or ageing often being intertwined with structural decline. The biomechanics of Caenorhabditis elegans, a model organism widely used in pharmacological and ageing research, has been established as biomarker for healthy ageing. However, the properties of the constituent tissues, and their contribution to the overall mechanical characteristics of the organism, remain relatively unknown. In this study we investigated the biomechanics of healthy C. elegans cuticle, muscle tissue, and pseudocoelom using a combination of indentation experiments and in silico modelling. We performed stiffness measurements using an atomic force microscope. To approximate the nematode's cylindrical body we used a novel three-compartment nonlinear finite element model, enabling us to analyse of how changes in the elasticity of individual compartments affect the bulk stiffness. We then fine-tuned the parameters of the model to match the simulation force-indentation output to the experimental data. To test the finite element model, we modified distinct compartments experimentally. Our in silico results, in agreement with previous studies, suggest that hyperosmotic shock reduces stiffness by decreasing the internal pressure. Unexpectedly, treatment with the neuromuscular agent aldicarb, traditionally associated with muscle contraction, reduced stiffness by decreasing the internal pressure. Furthermore, our finite element model can offer insights into how drugs, mutations, or processes such as ageing target individual tissues.
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Affiliation(s)
- Clara L. Essmann
- Department of Bioinformatics and Molecular Genetics, University of Freiburg, Freiburg, Baden-Wuerttemberg, Germany
- Department of Computer Science, University College London, London, United Kingdom
| | - Muna Elmi
- Department of Computer Science, University College London, London, United Kingdom
| | | | - Nikolaos Chrysochoidis
- Department of Mechanical Engineering and Aeronautics, University of Patras, Patras, Greece
| | - Michael Shaw
- Department of Computer Science, University College London, London, United Kingdom
- National Physical Laboratory, Teddington, United Kingdom
| | - Vijay Pawar
- Department of Computer Science, University College London, London, United Kingdom
| | | | - Vasileios Vavourakis
- Department of Mechanical and Manufacturing Engineering, University of Cyprus, Nicosia, Cyprus
- Department of Medical Physics and Biomedical Engineering, University College London, London, United Kingdom
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3
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Yeh YT, Del Álamo JC, Caffrey CR. Biomechanics of parasite migration within hosts. Trends Parasitol 2024; 40:164-175. [PMID: 38172015 DOI: 10.1016/j.pt.2023.12.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 11/30/2023] [Accepted: 12/01/2023] [Indexed: 01/05/2024]
Abstract
The dissemination of protozoan and metazoan parasites through host tissues is hindered by cellular barriers, dense extracellular matrices, and fluid forces in the bloodstream. To overcome these diverse biophysical impediments, parasites implement versatile migratory strategies. Parasite-exerted mechanical forces and upregulation of the host's cellular contractile machinery are the motors for these strategies, and these are comparably better characterized for protozoa than for helminths. Using the examples of the protozoans, Toxoplasma gondii and Plasmodium, and the metazoan, Schistosoma mansoni, we highlight how quantitative tools such as traction force and reflection interference contrast microscopies have improved our understanding of how parasites alter host mechanobiology to promote their migration.
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Affiliation(s)
- Yi-Ting Yeh
- Department of Mechanical Engineering, University of Washington, Seattle, WA 98109, USA; Center for Cardiovascular Biology, University of Washington, Seattle, WA 98109, USA.
| | - Juan C Del Álamo
- Department of Mechanical Engineering, University of Washington, Seattle, WA 98109, USA; Center for Cardiovascular Biology, University of Washington, Seattle, WA 98109, USA; Division of Cardiology, University of Washington, Seattle, WA 98109, USA; Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, CA 93093, USA
| | - Conor R Caffrey
- Center for Discovery and Innovation in Parasitic Diseases, Skaggs School of Pharmacy and Pharmaceutical Sciences, 9500 Gilman Drive, MC0657, University of California San Diego, La Jolla, CA 92093, USA
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4
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Reich H, Savage-Dunn C. Signaling circuits and the apical extracellular matrix in aging: connections identified in the nematode Caenorhabditis elegans. Am J Physiol Cell Physiol 2023; 325:C1201-C1211. [PMID: 37721005 PMCID: PMC10861026 DOI: 10.1152/ajpcell.00195.2023] [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: 05/09/2023] [Revised: 08/24/2023] [Accepted: 09/11/2023] [Indexed: 09/19/2023]
Abstract
Numerous conserved signaling pathways play critical roles in aging, including insulin/IGF-1, TGF-β, and Wnt pathways. Some of these pathways also play prominent roles in the formation and maintenance of the extracellular matrix. The nematode Caenorhabditis elegans has been an enduringly productive system for the identification of conserved mechanisms of biological aging. Recent studies in C. elegans highlight the regulatory circuits between conserved signaling pathways and the extracellular matrix, revealing a bidirectional relationship between these factors and providing a platform to address how regulation of and by the extracellular matrix can impact lifespan and organismal health during aging. These discoveries provide new opportunities for clinical advances and novel therapeutic strategies.
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Affiliation(s)
- Hannah Reich
- Department of Biology, Queens College, City University of New York, Flushing, New York, United States
| | - Cathy Savage-Dunn
- Department of Biology, Queens College, City University of New York, Flushing, New York, United States
- PhD Program in Biology, The Graduate Center, City University of New York, New York, New York, United States
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5
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Weng JW, Park H, Valotteau C, Chen RT, Essmann CL, Pujol N, Sternberg PW, Chen CH. Body stiffness is a mechanical property that facilitates contact-mediated mate recognition in Caenorhabditis elegans. Curr Biol 2023; 33:3585-3596.e5. [PMID: 37541249 PMCID: PMC10530406 DOI: 10.1016/j.cub.2023.07.020] [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: 12/12/2022] [Revised: 06/01/2023] [Accepted: 07/12/2023] [Indexed: 08/06/2023]
Abstract
Physical contact is prevalent in the animal kingdom to recognize suitable mates by decoding information about sex, species, and maturity. Although chemical cues for mate recognition have been extensively studied, the role of mechanical cues remains elusive. Here, we show that C. elegans males recognize conspecific and reproductive mates through short-range cues, and that the attractiveness of potential mates depends on the sex and developmental stages of the hypodermis. We find that a particular group of cuticular collagens is required for mate attractiveness. These collagens maintain body stiffness to sustain mate attractiveness but do not affect the surface properties that evoke the initial step of mate recognition, suggesting that males utilize multiple sensory mechanisms to recognize suitable mates. Manipulations of body stiffness via physical interventions, chemical treatments, and 3D-printed bionic worms indicate that body stiffness is a mechanical property for mate recognition and increases mating efficiency. Our study thus extends the repertoire of sensory cues of mate recognition in C. elegans and provides a paradigm to study the important roles of mechanosensory cues in social behaviors.
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Affiliation(s)
- Jen-Wei Weng
- Institute of Molecular and Cellular Biology, College of Life Science, National Taiwan University. No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan
| | - Heenam Park
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E California Boulevard, Pasadena, CA 91125, USA
| | - Claire Valotteau
- Aix-Marseille Univ, INSERM, CNRS, LAI, Turing Centre for Living Systems, 163 Avenue de Luminy, 13009 Marseille, France
| | - Rui-Tsung Chen
- Institute of Molecular and Cellular Biology, College of Life Science, National Taiwan University. No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan
| | - Clara L Essmann
- Bio3/Bioinformatics and Molecular Genetics, Albert-Ludwigs-University, Schaenzlestr. 1, 79104 Freiburg, Germany
| | - Nathalie Pujol
- Aix Marseille Univ, INSERM, CNRS, CIML, Turing Centre for Living Systems, 163 Avenue de Luminy, case 906, 13009 Marseille, France
| | - Paul W Sternberg
- Division of Biology and Biological Engineering, California Institute of Technology, 1200 E California Boulevard, Pasadena, CA 91125, USA.
| | - Chun-Hao Chen
- Institute of Molecular and Cellular Biology, College of Life Science, National Taiwan University. No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan; Division of Biology and Biological Engineering, California Institute of Technology, 1200 E California Boulevard, Pasadena, CA 91125, USA.
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6
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Greiffer L, Liebau E, Herrmann FC, Spiegler V. Condensed tannins act as anthelmintics by increasing the rigidity of the nematode cuticle. Sci Rep 2022; 12:18850. [PMID: 36344622 PMCID: PMC9640668 DOI: 10.1038/s41598-022-23566-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 11/02/2022] [Indexed: 11/09/2022] Open
Abstract
Tannins and tanniferous plant extracts have been discussed as sustainable means for helminth control in the past two decades in response to a dramatic increase of resistances towards standard anthelmintics. While their bioactivities have been broadly investigated in vitro and in vivo, less is known about their mode of action in nematodes, apart from their protein binding properties. In the current study we therefore investigated the impact of a phytochemically well characterized plant extract from Combretum mucronatum, known to contain procyanidins as the active compounds, on the model organism Caenorhabditis elegans. By different microscopic techniques, the cuticle was identified as the main binding site for tannins, whereas underlying tissues did not seem to be affected. In addition to disruptions of the cuticle structure, molting defects occurred at all larval stages. Finally, an increased rigidity of the nematodes' cuticle due to binding of tannins was confirmed by force spectroscopic measurements. This could be a key finding to explain several anthelmintic activities reported for tannins, especially impairment of molting or exsheathment as well as locomotion.
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Affiliation(s)
- Luise Greiffer
- grid.5949.10000 0001 2172 9288Institute for Pharmaceutical Biology and Phytochemistry, University of Münster, Münster, Germany
| | - Eva Liebau
- grid.5949.10000 0001 2172 9288Institute of Integrative Cell Biology and Physiology, University of Münster, Münster, Germany
| | - Fabian C. Herrmann
- grid.5949.10000 0001 2172 9288Institute for Pharmaceutical Biology and Phytochemistry, University of Münster, Münster, Germany
| | - Verena Spiegler
- grid.5949.10000 0001 2172 9288Institute for Pharmaceutical Biology and Phytochemistry, University of Münster, Münster, Germany
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7
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Nyaanga J, Shirman S, Mangan NM, Andersen EC. Characterization of larval growth in C. elegans cuticle mutants. MICROPUBLICATION BIOLOGY 2022; 2022:10.17912/micropub.biology.000662. [PMID: 36411799 PMCID: PMC9674971 DOI: 10.17912/micropub.biology.000662] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/13/2022] [Revised: 10/16/2022] [Accepted: 11/01/2022] [Indexed: 11/25/2022]
Abstract
In Caenorhabditis elegans, many genes involved in the formation of the cuticle are also known to influence body size and shape. We assessed post-embryonic growth of both long and short C. elegans body size mutants from the L1 to L4 stage. We found similar developmental trajectories of N2 and lon-3 animals. By contrast, we observed overall decreases in body length and increases in body width of tested dpy mutants compared to N2, consistent with the Dpy phenotype. We further show that the dynamics of animal shape in the mutant strains are consistent with a previously proposed "Stretcher" growth model.
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Affiliation(s)
- Joy Nyaanga
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
,
Interdisciplinary Biological Sciences Program, Northwestern University, Evanston, IL 60208, USA
| | - Sasha Shirman
- Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL 60208, USA
| | - Niall M. Mangan
- Department of Engineering Sciences and Applied Mathematics, Northwestern University, Evanston, IL 60208, USA
| | - Erik C. Andersen
- Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA
,
Correspondence to: Erik C. Andersen (
)
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8
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van den Boogaart LM, Langowski JKA, Amador GJ. Studying Stickiness: Methods, Trade-Offs, and Perspectives in Measuring Reversible Biological Adhesion and Friction. Biomimetics (Basel) 2022; 7:biomimetics7030134. [PMID: 36134938 PMCID: PMC9496521 DOI: 10.3390/biomimetics7030134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 09/09/2022] [Accepted: 09/11/2022] [Indexed: 11/16/2022] Open
Abstract
Controlled, reversible attachment is widely spread throughout the animal kingdom: from ticks to tree frogs, whose weights span from 2 mg to 200 g, and from geckos to mosquitoes, who stick under vastly different situations, such as quickly climbing trees and stealthily landing on human hosts. A fascinating and complex interplay of adhesive and frictional forces forms the foundation of attachment of these highly diverse systems to various substrates. In this review, we present an overview of the techniques used to quantify the adhesion and friction of terrestrial animals, with the aim of informing future studies on the fundamentals of bioadhesion, and motivating the development and adoption of new or alternative measurement techniques. We classify existing methods with respect to the forces they measure, including magnitude and source, i.e., generated by the whole body, single limbs, or by sub-structures. Additionally, we compare their versatility, specifically what parameters can be measured, controlled, and varied. This approach reveals critical trade-offs of bioadhesion measurement techniques. Beyond stimulating future studies on evolutionary and physicochemical aspects of bioadhesion, understanding the fundamentals of biological attachment is key to the development of biomimetic technologies, from soft robotic grippers to gentle surgical tools.
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Affiliation(s)
- Luc M. van den Boogaart
- Experimental Zoology Group, Department of Animal Sciences, Wageningen University & Research, De Elst 1, 6708 WD Wageningen, The Netherlands
- Department of BioMechanical Engineering, Faculty of Mechanical, Maritime and Materials Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands
| | - Julian K. A. Langowski
- Experimental Zoology Group, Department of Animal Sciences, Wageningen University & Research, De Elst 1, 6708 WD Wageningen, The Netherlands
- Correspondence: (J.K.A.L.); (G.J.A.)
| | - Guillermo J. Amador
- Experimental Zoology Group, Department of Animal Sciences, Wageningen University & Research, De Elst 1, 6708 WD Wageningen, The Netherlands
- Correspondence: (J.K.A.L.); (G.J.A.)
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9
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Changes in body shape implicate cuticle stretch in C. elegans growth control. Cells Dev 2022; 170:203780. [DOI: 10.1016/j.cdev.2022.203780] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2022] [Revised: 03/21/2022] [Accepted: 04/12/2022] [Indexed: 11/23/2022]
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10
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Rahimi M, Sohrabi S, Murphy CT. Novel elasticity measurements reveal C. elegans cuticle stiffens with age and in a long-lived mutant. Biophys J 2022; 121:515-524. [PMID: 35065051 PMCID: PMC8874029 DOI: 10.1016/j.bpj.2022.01.013] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2021] [Revised: 01/09/2022] [Accepted: 01/18/2022] [Indexed: 11/27/2022] Open
Abstract
Changes in biomechanical properties have profound impacts on human health. C. elegans might serve as a model for studying the molecular genetics of mammalian tissue decline. Previously, we found that collagens are required for insulin signaling mutants' long lifespan and that overexpression of specific collagens extends wild-type lifespan. However, whether these effects on lifespan are due to mechanical changes during aging has not yet been established. Here, we have developed two novel methods to study the cuticle: we measure mechanical properties of live animals using osmotic shock, and we directly perform the tensile test on isolated cuticles using microfluidic technology. Using these tools, we find that the cuticle, not the muscle, is responsible for changes in the "stretchiness" of C. elegans, and that cuticle stiffness is highly nonlinear and anisotropic. We also found that collagen mutations alter the integrity of the cuticle by significantly changing the elasticity. In addition, aging stiffens the cuticle under mechanical loads beyond the cuticle's healthy stretched state. Measurements of elasticity showed that long-lived daf-2 mutants were considerably better at preventing progressive mechanical changes with age. These tests of C. elegans biophysical properties suggest that the cuticle is responsible for their resilience.
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Affiliation(s)
- Mohammad Rahimi
- Department of Molecular Biology & Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey
| | - Salman Sohrabi
- Department of Molecular Biology & Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey
| | - Coleen T. Murphy
- Department of Molecular Biology & Lewis Sigler Institute for Integrative Genomics, Princeton University, Princeton, New Jersey,Corresponding author
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11
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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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12
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Beltrán SM, Slepian MJ, Taylor RE. Extending the Capabilities of Molecular Force Sensors via DNA Nanotechnology. Crit Rev Biomed Eng 2021; 48:1-16. [PMID: 32749116 DOI: 10.1615/critrevbiomedeng.2020033450] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
At the nanoscale, pushing, pulling, and shearing forces drive biochemical processes in development and remodeling as well as in wound healing and disease progression. Research in the field of mechanobiology investigates not only how these loads affect biochemical signaling pathways but also how signaling pathways respond to local loading by triggering mechanical changes such as regional stiffening of a tissue. This feedback between mechanical and biochemical signaling is increasingly recognized as fundamental in embryonic development, tissue morphogenesis, cell signaling, and disease pathogenesis. Historically, the interdisciplinary field of mechanobiology has been driven by the development of technologies for measuring and manipulating cellular and molecular forces, with each new tool enabling vast new lines of inquiry. In this review, we discuss recent advances in the manufacturing and capabilities of molecular-scale force and strain sensors. We also demonstrate how DNA nanotechnology has been critical to the enhancement of existing techniques and to the development of unique capabilities for future mechanosensor assembly. DNA is a responsive and programmable building material for sensor fabrication. It enables the systematic interrogation of molecular biomechanics with forces at the 1- to 200-pN scale that are needed to elucidate the fundamental means by which cells and proteins transduce mechanical signals.
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Affiliation(s)
- Susana M Beltrán
- Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania
| | - Marvin J Slepian
- Department of Medicine and Sarver Heart Center, University of Arizona, Tucson; Department of Biomedical Engineering, University of Arizona, Tucson; Department of Materials Science and Engineering, University of Arizona, Tucson
| | - Rebecca E Taylor
- Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania; Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania; Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania
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13
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Lamiré LA, Milani P, Runel G, Kiss A, Arias L, Vergier B, de Bossoreille S, Das P, Cluet D, Boudaoud A, Grammont M. Gradient in cytoplasmic pressure in germline cells controls overlying epithelial cell morphogenesis. PLoS Biol 2020; 18:e3000940. [PMID: 33253165 PMCID: PMC7703951 DOI: 10.1371/journal.pbio.3000940] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2019] [Accepted: 10/13/2020] [Indexed: 12/31/2022] Open
Abstract
It is unknown how growth in one tissue impacts morphogenesis in a neighboring tissue. To address this, we used the Drosophila ovarian follicle, in which a cluster of 15 nurse cells and a posteriorly located oocyte are surrounded by a layer of epithelial cells. It is known that as the nurse cells grow, the overlying epithelial cells flatten in a wave that begins in the anterior. Here, we demonstrate that an anterior to posterior gradient of decreasing cytoplasmic pressure is present across the nurse cells and that this gradient acts through TGFβ to control both the triggering and the progression of the wave of epithelial cell flattening. Our data indicate that intrinsic nurse cell growth is important to control proper nurse cell pressure. Finally, we reveal that nurse cell pressure and subsequent TGFβ activity in the stretched cells combine to increase follicle elongation in the anterior, which is crucial for allowing nurse cell growth and pressure control. More generally, our results reveal that during development, inner cytoplasmic pressure in individual cells has an important role in shaping their neighbors.
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Affiliation(s)
- Laurie-Anne Lamiré
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Pascale Milani
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Gaël Runel
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Annamaria Kiss
- Reproduction et Développement des Plantes, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRAE, Lyon, France
| | - Leticia Arias
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Blandine Vergier
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Stève de Bossoreille
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Pradeep Das
- Reproduction et Développement des Plantes, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRAE, Lyon, France
| | - David Cluet
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
| | - Arezki Boudaoud
- Reproduction et Développement des Plantes, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, INRAE, Lyon, France
| | - Muriel Grammont
- Laboratoire de Biologie et de Modélisation de la Cellule, Univ Lyon, ENS de Lyon, UCB Lyon 1, CNRS, Lyon, France
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14
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Jung W, Li J, Chaudhuri O, Kim T. Nonlinear Elastic and Inelastic Properties of Cells. J Biomech Eng 2020; 142:100806. [PMID: 32253428 PMCID: PMC7477719 DOI: 10.1115/1.4046863] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2019] [Revised: 03/27/2020] [Indexed: 12/15/2022]
Abstract
Mechanical forces play an important role in various physiological processes, such as morphogenesis, cytokinesis, and migration. Thus, in order to illuminate mechanisms underlying these physiological processes, it is crucial to understand how cells deform and respond to external mechanical stimuli. During recent decades, the mechanical properties of cells have been studied extensively using diverse measurement techniques. A number of experimental studies have shown that cells are far from linear elastic materials. Cells exhibit a wide variety of nonlinear elastic and inelastic properties. Such complicated properties of cells are known to emerge from unique mechanical characteristics of cellular components. In this review, we introduce major cellular components that largely govern cell mechanical properties and provide brief explanations of several experimental techniques used for rheological measurements of cell mechanics. Then, we discuss the representative nonlinear elastic and inelastic properties of cells. Finally, continuum and discrete computational models of cell mechanics, which model both nonlinear elastic and inelastic properties of cells, will be described.
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Affiliation(s)
- Wonyeong Jung
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN 47907
| | - Jing Li
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN 47907
| | - Ovijit Chaudhuri
- Department of Mechanical Engineering, Stanford University, 440 Escondido Mall, Stanford, CA 94305
| | - Taeyoon Kim
- Weldon School of Biomedical Engineering, Purdue University, 206 S. Martin Jischke Drive, West Lafayette, IN 47907
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15
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Remer I, Shaashoua R, Shemesh N, Ben-Zvi A, Bilenca A. High-sensitivity and high-specificity biomechanical imaging by stimulated Brillouin scattering microscopy. Nat Methods 2020; 17:913-916. [PMID: 32747769 DOI: 10.1038/s41592-020-0882-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2019] [Accepted: 05/27/2020] [Indexed: 01/04/2023]
Abstract
Label-free, non-contact imaging with mechanical contrast and optical sectioning is a substantial challenge in microscopy. Spontaneous Brillouin scattering microscopy meets this challenge, but encounters a trade-off between acquisition speed and the specificity for biomechanical constituents with overlapping Brillouin bands. Stimulated Brillouin scattering microscopy overcomes this trade-off and enables the cross-sectional imaging of live Caenorhabditis elegans at the organ and subcellular levels, with both elasticity and viscosity contrasts at high specificity and with practical recording times.
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Affiliation(s)
- Itay Remer
- Biomedical Engineering Department, Ben-Gurion University of the Negev, Be'er-Sheva, Israel. .,Agilent Research Laboratories, Petach Tikva, Israel.
| | - Roni Shaashoua
- Biomedical Engineering Department, Ben-Gurion University of the Negev, Be'er-Sheva, Israel
| | - Netta Shemesh
- Department of Life Sciences, Ben-Gurion University of the Negev, Be'er Sheva, Israel
| | - Anat Ben-Zvi
- Department of Life Sciences, Ben-Gurion University of the Negev, Be'er Sheva, Israel
| | - Alberto Bilenca
- Biomedical Engineering Department, Ben-Gurion University of the Negev, Be'er-Sheva, Israel. .,Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Be'er-Sheva, Israel.
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16
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Krenger R, Burri JT, Lehnert T, Nelson BJ, Gijs MAM. Force microscopy of the Caenorhabditis elegans embryonic eggshell. MICROSYSTEMS & NANOENGINEERING 2020; 6:29. [PMID: 32382445 PMCID: PMC7196560 DOI: 10.1038/s41378-020-0137-3] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2019] [Revised: 12/20/2019] [Accepted: 02/13/2020] [Indexed: 05/03/2023]
Abstract
Assays focusing on emerging biological phenomena in an animal's life can be performed during embryogenesis. While the embryo of Caenorhabditis elegans has been extensively studied, its biomechanical properties are largely unknown. Here, we demonstrate that cellular force microscopy (CFM), a recently developed technique that combines micro-indentation with high resolution force sensing approaching that of atomic force microscopy, can be successfully applied to C. elegans embryos. We performed, for the first time, a quantitative study of the mechanical properties of the eggshell of living C. elegans embryos and demonstrate the capability of the system to detect alterations of its mechanical parameters and shell defects upon chemical treatments. In addition to investigating natural eggshells, we applied different eggshell treatments, i.e., exposure to sodium hypochlorite and chitinase solutions, respectively, that selectively modified the multilayer eggshell structure, in order to evaluate the impact of the different layers on the mechanical integrity of the embryo. Finite element method simulations based on a simple embryo model were used to extract characteristic eggshell parameters from the experimental micro-indentation force-displacement curves. We found a strong correlation between the severity of the chemical treatment and the rigidity of the shell. Furthermore, our results showed, in contrast to previous assumptions, that short bleach treatments not only selectively remove the outermost vitelline layer of the eggshell, but also significantly degenerate the underlying chitin layer, which is primarily responsible for the mechanical stability of the egg.
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Affiliation(s)
- Roger Krenger
- Laboratory of Microsystems, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Jan T. Burri
- Multi-Scale Robotics Laboratory, ETH Zurich, Zürich, 8092 Switzerland
| | - Thomas Lehnert
- Laboratory of Microsystems, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
| | - Bradley J. Nelson
- Multi-Scale Robotics Laboratory, ETH Zurich, Zürich, 8092 Switzerland
| | - Martin A. M. Gijs
- Laboratory of Microsystems, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
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17
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Essmann CL, Martinez-Martinez D, Pryor R, Leung KY, Krishnan KB, Lui PP, Greene NDE, Brown AEX, Pawar VM, Srinivasan MA, Cabreiro F. Mechanical properties measured by atomic force microscopy define health biomarkers in ageing C. elegans. Nat Commun 2020; 11:1043. [PMID: 32098962 PMCID: PMC7042263 DOI: 10.1038/s41467-020-14785-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 01/31/2020] [Indexed: 12/16/2022] Open
Abstract
Genetic and environmental factors are key drivers regulating organismal lifespan but how these impact healthspan is less well understood. Techniques capturing biomechanical properties of tissues on a nano-scale level are providing new insights into disease mechanisms. Here, we apply Atomic Force Microscopy (AFM) to quantitatively measure the change in biomechanical properties associated with ageing Caenorhabditis elegans in addition to capturing high-resolution topographical images of cuticle senescence. We show that distinct dietary restriction regimes and genetic pathways that increase lifespan lead to radically different healthspan outcomes. Hence, our data support the view that prolonged lifespan does not always coincide with extended healthspan. Importantly, we identify the insulin signalling pathway in C. elegans and interventions altering bacterial physiology as increasing both lifespan and healthspan. Overall, AFM provides a highly sensitive technique to measure organismal biomechanical fitness and delivers an approach to screen for health-improving conditions, an essential step towards healthy ageing.
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Affiliation(s)
- Clara L Essmann
- Department of Computer Science, University College London, Engineering Building, Malet Place, London, WC1E 7JG, UK.
- Institute of Structural and Molecular Biology, University College London and Birkbeck, London, WC1E 6BT, UK.
- MRC London Institute of Medical Sciences, Du Cane Road, London, W12 0NN, UK.
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK.
| | - Daniel Martinez-Martinez
- MRC London Institute of Medical Sciences, Du Cane Road, London, W12 0NN, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK
| | - Rosina Pryor
- Institute of Structural and Molecular Biology, University College London and Birkbeck, London, WC1E 6BT, UK
- MRC London Institute of Medical Sciences, Du Cane Road, London, W12 0NN, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK
| | - Kit-Yi Leung
- UCL Great Ormond Street Institute of Child Health, University College London, London, WC1N 1EH, UK
| | - Kalaivani Bala Krishnan
- Institute of Structural and Molecular Biology, University College London and Birkbeck, London, WC1E 6BT, UK
| | - Prudence Pokway Lui
- Institute of Structural and Molecular Biology, University College London and Birkbeck, London, WC1E 6BT, UK
| | - Nicholas D E Greene
- UCL Great Ormond Street Institute of Child Health, University College London, London, WC1N 1EH, UK
| | - André E X Brown
- MRC London Institute of Medical Sciences, Du Cane Road, London, W12 0NN, UK
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK
| | - Vijay M Pawar
- Department of Computer Science, University College London, Engineering Building, Malet Place, London, WC1E 7JG, UK
| | - Mandayam A Srinivasan
- Department of Computer Science, University College London, Engineering Building, Malet Place, London, WC1E 7JG, UK
- Department of Mechanical Engineering and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, 02139, USA
| | - Filipe Cabreiro
- Institute of Structural and Molecular Biology, University College London and Birkbeck, London, WC1E 6BT, UK.
- MRC London Institute of Medical Sciences, Du Cane Road, London, W12 0NN, UK.
- Institute of Clinical Sciences, Imperial College London, Hammersmith Hospital Campus, Du Cane Road, London, W12 0NN, UK.
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18
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How Caenorhabditis elegans Senses Mechanical Stress, Temperature, and Other Physical Stimuli. Genetics 2019; 212:25-51. [PMID: 31053616 PMCID: PMC6499529 DOI: 10.1534/genetics.118.300241] [Citation(s) in RCA: 67] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 03/04/2019] [Indexed: 12/30/2022] Open
Abstract
Caenorhabditis elegans lives in a complex habitat in which they routinely experience large fluctuations in temperature, and encounter physical obstacles that vary in size and composition. Their habitat is shared by other nematodes, by beneficial and harmful bacteria, and nematode-trapping fungi. Not surprisingly, these nematodes can detect and discriminate among diverse environmental cues, and exhibit sensory-evoked behaviors that are readily quantifiable in the laboratory at high resolution. Their ability to perform these behaviors depends on <100 sensory neurons, and this compact sensory nervous system together with powerful molecular genetic tools has allowed individual neuron types to be linked to specific sensory responses. Here, we describe the sensory neurons and molecules that enable C. elegans to sense and respond to physical stimuli. We focus primarily on the pathways that allow sensation of mechanical and thermal stimuli, and briefly consider this animal’s ability to sense magnetic and electrical fields, light, and relative humidity. As the study of sensory transduction is critically dependent upon the techniques for stimulus delivery, we also include a section on appropriate laboratory methods for such studies. This chapter summarizes current knowledge about the sensitivity and response dynamics of individual classes of C. elegans mechano- and thermosensory neurons from in vivo calcium imaging and whole-cell patch-clamp electrophysiology studies. We also describe the roles of conserved molecules and signaling pathways in mediating the remarkably sensitive responses of these nematodes to mechanical and thermal cues. These studies have shown that the protein partners that form mechanotransduction channels are drawn from multiple superfamilies of ion channel proteins, and that signal transduction pathways responsible for temperature sensing in C. elegans share many features with those responsible for phototransduction in vertebrates.
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19
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Sanzeni A, Katta S, Petzold B, Pruitt BL, Goodman MB, Vergassola M. Somatosensory neurons integrate the geometry of skin deformation and mechanotransduction channels to shape touch sensing. eLife 2019; 8:43226. [PMID: 31407662 PMCID: PMC6692131 DOI: 10.7554/elife.43226] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 07/17/2019] [Indexed: 01/08/2023] Open
Abstract
Touch sensation hinges on force transfer across the skin and activation of mechanosensitive ion channels along the somatosensory neurons that invade the skin. This skin-nerve sensory system demands a quantitative model that spans the application of mechanical loads to channel activation. Unlike prior models of the dynamic responses of touch receptor neurons in Caenorhabditis elegans (Eastwood et al., 2015), which substituted a single effective channel for the ensemble along the TRNs, this study integrates body mechanics and the spatial recruitment of the various channels. We demonstrate that this model captures mechanical properties of the worm’s body and accurately reproduces neural responses to simple stimuli. It also captures responses to complex stimuli featuring non-trivial spatial patterns, like extended or multiple contacts that could not be addressed otherwise. We illustrate the importance of these effects with new experiments revealing that skin-neuron composites respond to pre-indentation with increased currents rather than adapting to persistent stimulation.
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Affiliation(s)
- Alessandro Sanzeni
- Department of Physics, University of California, San Diego, La Jolla, United States.,National Institute of Mental Health Intramural Program, National Institutes of Health, Bethesda, United States
| | - Samata Katta
- Neuroscience Program, Stanford University School of Medicine, Stanford, United States
| | - Bryan Petzold
- Department of Mechanical Engineering, Stanford University, Stanford, United States
| | - Beth L Pruitt
- Department of Mechanical Engineering, Stanford University, Stanford, United States.,Department of Bioengineering, Stanford University, Stanford, United States
| | - Miriam B Goodman
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, United States
| | - Massimo Vergassola
- Department of Physics, University of California, San Diego, La Jolla, United States
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20
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21
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Worms on a Chip. Bioanalysis 2019. [DOI: 10.1007/978-981-13-6229-3_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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22
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Denham JE, Ranner T, Cohen N. Signatures of proprioceptive control in Caenorhabditis elegans locomotion. Philos Trans R Soc Lond B Biol Sci 2018; 373:rstb.2018.0208. [PMID: 30201846 DOI: 10.1098/rstb.2018.0208] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/13/2018] [Indexed: 12/20/2022] Open
Abstract
Animal neuromechanics describes the coordinated self-propelled movement of a body, subject to the combined effects of internal neural control and mechanical forces. Here we use a computational model to identify effects of neural and mechanical modulation on undulatory forward locomotion of Caenorhabditis elegans, with a focus on proprioceptively driven neural control. We reveal a fundamental relationship between body elasticity and environmental drag in determining the dynamics of the body and demonstrate the manifestation of this relationship in the context of proprioceptively driven control. By considering characteristics unique to proprioceptive neurons, we predict the signatures of internal gait modulation that contrast with the known signatures of externally or biomechanically modulated gait. We further show that proprioceptive feedback can suppress neuromechanical phase lags during undulatory locomotion, contrasting with well studied advancing phase lags that have long been a signature of centrally generated, feed-forward control.This article is part of a discussion meeting issue 'Connectome to behaviour: modelling C. elegans at cellular resolution'.
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Affiliation(s)
- Jack E Denham
- School of Computing, University of Leeds, Leeds LS2 9JT, UK
| | - Thomas Ranner
- School of Computing, University of Leeds, Leeds LS2 9JT, UK
| | - Netta Cohen
- School of Computing, University of Leeds, Leeds LS2 9JT, UK
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23
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Fechner S, Loizeau F, Nekimken AL, Pruitt BL, Goodman MB. The bodies of dpy-10(e128) are twice as stiff as wild type. MICROPUBLICATION BIOLOGY 2018; 2018. [PMID: 32550396 PMCID: PMC7282522 DOI: 10.17912/ecsm-mp67] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Sylvia Fechner
- Molecular and Cellular Physiology, Stanford School of Medicine, Stanford
| | - Frédéric Loizeau
- Departments of Bioengineering and Mechanical Engineering, Stanford
| | - Adam L Nekimken
- Molecular and Cellular Physiology, Stanford School of Medicine, Stanford.,Departments of Bioengineering and Mechanical Engineering, Stanford
| | - Beth L Pruitt
- Departments of Bioengineering and Mechanical Engineering, Stanford.,Departments of Mechanical Engineering and Biomolecular Science and Engineering, University of California, Santa Barbara
| | - Miriam B Goodman
- Molecular and Cellular Physiology, Stanford School of Medicine, Stanford
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24
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Mazzochette EA, Nekimken AL, Loizeau F, Whitworth J, Huynh B, Goodman MB, Pruitt BL. The tactile receptive fields of freely moving Caenorhabditis elegans nematodes. Integr Biol (Camb) 2018; 10:450-463. [PMID: 30027970 PMCID: PMC6168290 DOI: 10.1039/c8ib00045j] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Sensory neurons embedded in skin are responsible for the sense of touch. In humans and other mammals, touch sensation depends on thousands of diverse somatosensory neurons. By contrast, Caenorhabditis elegans nematodes have six gentle touch receptor neurons linked to simple behaviors. The classical touch assay uses an eyebrow hair to stimulate freely moving C. elegans, evoking evasive behavioral responses. This assay has led to the discovery of genes required for touch sensation, but does not provide control over stimulus strength or position. Here, we present an integrated system for performing automated, quantitative touch assays that circumvents these limitations and incorporates automated measurements of behavioral responses. The Highly Automated Worm Kicker (HAWK) unites a microfabricated silicon force sensor holding a glass bead forming the contact surface and video analysis with real-time force and position control. Using this system, we stimulated animals along the anterior-posterior axis and compared responses in wild-type and spc-1(dn) transgenic animals, which have a touch defect due to expression of a dominant-negative α-spectrin protein fragment. As expected from prior studies, delivering large stimuli anterior and posterior to the mid-point of the body evoked a reversal and a speed-up, respectively. The probability of evoking a response of either kind depended on stimulus strength and location; once initiated, the magnitude and quality of both reversal and speed-up behavioral responses were uncorrelated with stimulus location, strength, or the absence or presence of the spc-1(dn) transgene. Wild-type animals failed to respond when the stimulus was applied near the mid-point. These results show that stimulus strength and location govern the activation of a characteristic motor program and that the C. elegans body surface consists of two receptive fields separated by a gap.
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Affiliation(s)
- E A Mazzochette
- Department of Electrical Engineering, Stanford University, 94305, USA
| | - A L Nekimken
- Department of Mechanical Engineering, Stanford University, 94305, USA. and Department of Molecular and Cellular Physiology, Stanford University, 94305, USA
| | - F Loizeau
- Department of Mechanical Engineering, Stanford University, 94305, USA.
| | - J Whitworth
- Department of Mechanical Engineering, Stanford University, 94305, USA.
| | - B Huynh
- Department of Mechanical Engineering, Stanford University, 94305, USA.
| | - M B Goodman
- Department of Mechanical Engineering, Stanford University, 94305, USA. and Department of Molecular and Cellular Physiology, Stanford University, 94305, USA
| | - B L Pruitt
- Department of Mechanical Engineering, Stanford University, 94305, USA. and Department of Molecular and Cellular Physiology, Stanford University, 94305, USA and Department of Bioengineering, Stanford University, 94305, USA and Department of Mechanical Engineering, University of California, Santa Barbara, 93106, USA.
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25
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Kim AA, Nekimken AL, Fechner S, O'Brien LE, Pruitt BL. Microfluidics for mechanobiology of model organisms. Methods Cell Biol 2018; 146:217-259. [PMID: 30037463 PMCID: PMC6418080 DOI: 10.1016/bs.mcb.2018.05.010] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Mechanical stimuli play a critical role in organ development, tissue homeostasis, and disease. Understanding how mechanical signals are processed in multicellular model systems is critical for connecting cellular processes to tissue- and organism-level responses. However, progress in the field that studies these phenomena, mechanobiology, has been limited by lack of appropriate experimental techniques for applying repeatable mechanical stimuli to intact organs and model organisms. Microfluidic platforms, a subgroup of microsystems that use liquid flow for manipulation of objects, are a promising tool for studying mechanobiology of small model organisms due to their size scale and ease of customization. In this work, we describe design considerations involved in developing a microfluidic device for studying mechanobiology. Then, focusing on worms, fruit flies, and zebrafish, we review current microfluidic platforms for mechanobiology of multicellular model organisms and their tissues and highlight research opportunities in this developing field.
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Affiliation(s)
- Anna A Kim
- University of California, Santa Barbara, CA, United States; Uppsala University, Uppsala, Sweden; Stanford University, Stanford, CA, United States
| | | | | | | | - Beth L Pruitt
- University of California, Santa Barbara, CA, United States; Stanford University, Stanford, CA, United States.
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26
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Kamili F, Lu H. Recent Advances and Trends in Microfluidic Platforms for C. elegans Biological Assays. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2018; 11:245-264. [PMID: 29894230 DOI: 10.1146/annurev-anchem-061417-125604] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Microfluidics has proven to be a key tool in quantitative biological research. The C. elegans research community in particular has developed a variety of microfluidic platforms to investigate sensory systems, development, aging, and physiology of the nematode. Critical for the growth of this field, however, has been the implementation of concurrent advanced microscopy, hardware, and software technologies that enable the discovery of novel biology. In this review, we highlight recent innovations in microfluidic platforms used for assaying C. elegans and discuss the novel technological approaches and analytic strategies required for these systems. We conclude that platforms that provide analytical frameworks for assaying specific biological mechanisms and those that take full advantage of integrated technologies to extract high-value quantitative information from worm assays are most likely to move the field forward.
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Affiliation(s)
- Farhan Kamili
- Interdisciplinary Program in Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Hang Lu
- Interdisciplinary Program in Bioengineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, USA;
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27
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Cho Y, Oakland DN, Lee SA, Schafer WR, Lu H. On-chip functional neuroimaging with mechanical stimulation in Caenorhabditis elegans larvae for studying development and neural circuits. LAB ON A CHIP 2018; 18:601-609. [PMID: 29340386 PMCID: PMC5885276 DOI: 10.1039/c7lc01201b] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
Mechanosensation is fundamentally important for the abilities of an organism to experience touch, hear sounds, and maintain balance. Caenorhabditis elegans is a powerful system for studying mechanosensation as this worm is well suited for in vivo functional imaging of neurons. Many years of research using labor-intensive methods have generated a wealth of knowledge about mechanosensation in C. elegans, and the recent microfluidic-based platforms continue to push the boundary for this field. However, developmental aspects of sensory biology, including mechanosensation, are still not fully understood. One current bottleneck is the difficulty in assaying larvae because they are much smaller than adult worms. Microfluidic devices with features small enough for larvae, especially actuators for the delivery of mechanical stimulation, are difficult to design and fabricate. Here, we present a series of automatic microfluidic platforms that allow for in vivo functional imaging of C. elegans responding to controlled mechanical stimulation at different developmental stages. Using a novel fabrication method, we designed highly deformable pneumatically actuated on-chip structures that can deliver mechanical stimulation to larval worms. The PDMS actuator allows for quantitatively controlled mechanical stimulation of both gentle and harsh touch neurons, by simply changing the actuation pressure, which makes this device easily translatable to other labs. We validated the design and utility of our systems with studies of the functional role of mechanosensory neurons in developing worms; we showed that gentle and harsh touch neurons function similarly in early larvae as they do in the adult stage, which would not have been possible previously. Finally, we investigated the effect of a sleep-like state on neuronal responses by imaging C. elegans in the lethargus state.
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Affiliation(s)
- Yongmin Cho
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, USA.
| | - David N Oakland
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, USA.
| | - Sol Ah Lee
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, USA.
| | - William R Schafer
- Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - Hang Lu
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, USA.
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28
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McClanahan PD, Xu JH, Fang-Yen C. Comparing Caenorhabditis elegans gentle and harsh touch response behavior using a multiplexed hydraulic microfluidic device. Integr Biol (Camb) 2017; 9:800-809. [PMID: 28914311 PMCID: PMC5645015 DOI: 10.1039/c7ib00120g] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The roundworm Caenorhabditis elegans is an important model system for understanding the genetics and physiology of touch. Classical assays for C. elegans touch, which involve manually touching the animal with a probe and observing its response, are limited by their low throughput and qualitative nature. We developed a microfluidic device in which several dozen animals are subject to spatially localized mechanical stimuli with variable amplitude. The device contains 64 sinusoidal channels through which worms crawl, and hydraulic valves that deliver touch stimuli to the worms. We used this assay to characterize the behavioral responses to gentle touch stimuli and the less well studied harsh (nociceptive) touch stimuli. First, we measured the relative response thresholds of gentle and harsh touch. Next, we quantified differences in the receptive fields between wild type worms and a mutant with non-functioning posterior touch receptor neurons. We showed that under gentle touch the receptive field of the anterior touch receptor neurons extends into the posterior half of the body. Finally, we found that the behavioral response to gentle touch does not depend on the locomotion of the animal immediately prior to the stimulus, but does depend on the location of the previous touch. Responses to harsh touch, on the other hand, did not depend on either previous velocity or stimulus location. Differences in gentle and harsh touch response characteristics may reflect the different innervation of the respective mechanosensory cells. Our assay will facilitate studies of mechanosensation, sensory adaptation, and nociception.
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Affiliation(s)
- Patrick D McClanahan
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA.
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29
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Determining the biomechanics of touch sensation in C. elegans. Sci Rep 2017; 7:12329. [PMID: 28951574 PMCID: PMC5615042 DOI: 10.1038/s41598-017-12190-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Accepted: 09/05/2017] [Indexed: 11/12/2022] Open
Abstract
The sense of touch is a fundamental mechanism that nearly all organisms use to interact with their surroundings. However, the process of mechanotransduction whereby a mechanical stimulus gives rise to a neuronal response is not well understood. In this paper we present an investigation of the biomechanics of touch using the model organism C. elegans. By developing a custom micromanipulation and force sensing system around a high resolution optical microscope, we measured the spatial deformation of the organism’s cuticle and force response to controlled uniaxial indentations. We combined these experimental results with anatomical data to create a multilayer computational biomechanical model of the organism and accurately derive its material properties such as the elastic modulus and poisson’s ratio. We demonstrate the utility of this model by combining it with previously published electrophysiological data to provide quantitative insights into different biomechanical states for mechanotransduction, including the first estimate of the sensitivity of an individual mechanoreceptor to an applied stimulus (parameterised as strain energy density). We also interpret empirical behavioural data to estimate the minimum number of mechanoreceptors which must be activated to elicit a behavioural response.
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30
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Cho Y, Porto DA, Hwang H, Grundy LJ, Schafer WR, Lu H. Automated and controlled mechanical stimulation and functional imaging in vivo in C. elegans. LAB ON A CHIP 2017; 17:2609-2618. [PMID: 28660945 PMCID: PMC5575793 DOI: 10.1039/c7lc00465f] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
C. elegans is a useful genetic model system for investigating mechanisms involved in sensory behavior which are potentially relevant to human diseases. While utilities of advanced techniques such as microfluidics have accelerated some areas of C. elegans sensory biology such as chemosensation, studies of mechanosensation conventionally require immobilization by glue and manual delivery of stimuli, leading to low experimental throughput and high variability. Here we present a microfluidic platform that precisely and robustly delivers a wide range of mechanical stimuli and can also be used in conjunction with functional imaging and optical interrogation techniques. The platform is fully automated, thereby greatly enhancing the throughput and robustness of experiments. We show that the behavior of the well-known gentle and harsh touch neurons and their receptive fields can be recapitulated. Using calcium dynamics as a read-out, we demonstrate its ability to perform a drug screen in vivo. We envision that this system will be able to greatly accelerate the discovery of genes and molecules involved in mechanosensation and multimodal sensory behavior, as well as the discovery of therapeutics for related diseases.
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Affiliation(s)
- Yongmin Cho
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, USA.
| | - Daniel A Porto
- Interdisciplinary Bioengineering Program, Georgia Institute of Technology, USA
| | - Hyundoo Hwang
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, USA.
| | - Laura J Grundy
- Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - William R Schafer
- Medical Research Council Laboratory of Molecular Biology, Cambridge, UK
| | - Hang Lu
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology, USA.
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Nekimken AL, Mazzochette EA, Goodman MB, Pruitt BL. Forces applied during classical touch assays for Caenorhabditis elegans. PLoS One 2017; 12:e0178080. [PMID: 28542494 PMCID: PMC5438190 DOI: 10.1371/journal.pone.0178080] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 05/06/2017] [Indexed: 12/03/2022] Open
Abstract
For decades, Caenorhabditis elegans roundworms have been used to study the sense of touch, and this work has been facilitated by a simple behavioral assay for touch sensation. To perform this classical assay, an experimenter uses an eyebrow hair to gently touch a moving worm and observes whether or not the worm reverses direction. We used two experimental approaches to determine the manner and moment of contact between the eyebrow hair tool and freely moving animals and the forces delivered by the classical assay. Using high-speed video (2500 frames/second), we found that typical stimulus delivery events include a brief moment when the hair is contact with the worm's body and not the agar substrate. To measure the applied forces, we measured forces generated by volunteers mimicking the classical touch assay by touching a calibrated microcantilever. The mean (61 μN) and median forces (26 μN) were more than ten times higher than the 2-μN force known to saturate the probability of evoking a reversal in adult C. elegans. We also considered the eyebrow hairs as an additional source of variation. The stiffness of the sampled eyebrow hairs varied between 0.07 and 0.41 N/m and was correlated with the free length of hair. Collectively, this work establishes that the classical touch assay applies enough force to saturate the probability of evoking reversals in adult C. elegans in spite of its variability among trials and experimenters and that increasing the free length of the hair can decrease the applied force.
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Affiliation(s)
- Adam L. Nekimken
- Mechanical Engineering Department, Stanford University, Stanford, California, United States of America
| | - Eileen A. Mazzochette
- Electrical Engineering Department, Stanford University, Stanford, California, United States of America
| | - Miriam B. Goodman
- Mechanical Engineering Department, Stanford University, Stanford, California, United States of America
- Molecular and Cellular Physiology Department, Stanford University, Stanford, California, United States of America
| | - Beth L. Pruitt
- Mechanical Engineering Department, Stanford University, Stanford, California, United States of America
- Molecular and Cellular Physiology Department, Stanford University, Stanford, California, United States of America
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Nanoscale imaging and characterization of Caenorhabditis elegans epicuticle using atomic force microscopy. NANOMEDICINE-NANOTECHNOLOGY BIOLOGY AND MEDICINE 2017; 13:483-491. [DOI: 10.1016/j.nano.2016.10.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Revised: 09/14/2016] [Accepted: 10/07/2016] [Indexed: 12/21/2022]
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Shaw M, Elmi M, Pawar V, Srinivasan MA. Investigation of mechanosensation in C. elegans using light field calcium imaging. BIOMEDICAL OPTICS EXPRESS 2016; 7:2877-87. [PMID: 27446713 PMCID: PMC4948637 DOI: 10.1364/boe.7.002877] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 05/20/2016] [Accepted: 06/07/2016] [Indexed: 05/09/2023]
Abstract
We describe a new experimental approach to investigate touch sensation in the model organism C. elegans using light field deconvolution microscopy. By combining fast volumetric image acquisition with controlled indentation of the organism using a high sensitivity force transducer, we are able to simultaneously measure activity in multiple touch receptor neurons expressing the calcium ion indicator GCaMP6s. By varying the applied mechanical stimulus we show how this method can be used to quantify touch sensitivity in C. elegans. We describe some of the challenges of performing light field calcium imaging in moving samples and demonstrate that they can be overcome by simple data processing.
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Affiliation(s)
- Michael Shaw
- Analytical Science Division, National Physical Laboratory, Teddington, Middlesex, TW11 0LW, UK
- UCL Touchlab, Department of Computer Science, University College London, Gower Street, London, WC1 6BT, UK
| | - Muna Elmi
- UCL Touchlab, Department of Computer Science, University College London, Gower Street, London, WC1 6BT, UK
| | - Vijay Pawar
- UCL Touchlab, Department of Computer Science, University College London, Gower Street, London, WC1 6BT, UK
| | - Mandayam A. Srinivasan
- UCL Touchlab, Department of Computer Science, University College London, Gower Street, London, WC1 6BT, UK
- MIT Touchlab, Department of Mechanical Engineering and Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, MA, 01239, USA
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Tissue mechanics govern the rapidly adapting and symmetrical response to touch. Proc Natl Acad Sci U S A 2015; 112:E6955-63. [PMID: 26627717 DOI: 10.1073/pnas.1514138112] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Interactions with the physical world are deeply rooted in our sense of touch and depend on ensembles of somatosensory neurons that invade and innervate the skin. Somatosensory neurons convert the mechanical energy delivered in each touch into excitatory membrane currents carried by mechanoelectrical transduction (MeT) channels. Pacinian corpuscles in mammals and touch receptor neurons (TRNs) in Caenorhabditis elegans nematodes are embedded in distinctive specialized accessory structures, have low thresholds for activation, and adapt rapidly to the application and removal of mechanical loads. Recently, many of the protein partners that form native MeT channels in these and other somatosensory neurons have been identified. However, the biophysical mechanism of symmetric responses to the onset and offset of mechanical stimulation has eluded understanding for decades. Moreover, it is not known whether applied force or the resulting indentation activate MeT channels. Here, we introduce a system for simultaneously recording membrane current, applied force, and the resulting indentation in living C. elegans (Feedback-controlled Application of mechanical Loads Combined with in vivo Neurophysiology, FALCON) and use it, together with modeling, to study these questions. We show that current amplitude increases with indentation, not force, and that fast stimuli evoke larger currents than slower stimuli producing the same or smaller indentation. A model linking body indentation to MeT channel activation through an embedded viscoelastic element reproduces the experimental findings, predicts that the TRNs function as a band-pass mechanical filter, and provides a general mechanism for symmetrical and rapidly adapting MeT channel activation relevant to somatosensory neurons across phyla and submodalities.
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Allen MJ, Kanteti R, Riehm JJ, El-Hashani E, Salgia R. Whole-animal mounts of Caenorhabditis elegans for 3D imaging using atomic force microscopy. NANOMEDICINE : NANOTECHNOLOGY, BIOLOGY, AND MEDICINE 2015; 11:1971-4. [PMID: 26282382 PMCID: PMC5051269 DOI: 10.1016/j.nano.2015.07.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 07/20/2015] [Accepted: 07/24/2015] [Indexed: 11/21/2022]
Abstract
The 3D surface of Caenorhabditis elegans was imaged at nanometer resolution using atomic force microscopy (AFM). Oscillation of a medium stiffness silicon AFM cantilever at the upper second amplitude peak, typically 6 times above the fundamental frequency, vastly improved image quality on the moist, sticky, and soft worms. Whole-animal mounts of normal and double-headed mutants of the nematode worm were prepared and scanned. Well-preserved anatomical features including annuli, furrows, alae, and rows of never before seen nanometer-sized pores dotting the molted worm's outermost surface coat were resolved. Well-preserved anatomical features including annuli, furrows, alae, and rows of nanometer-sized pores or struts dotting the molted worm's outermost surface were resolved. This AFM method represents a simple and rapid new approach for nanometer-resolved 3D imaging and analysis of whole-animal specimens of C. elegans. FROM THE CLINICAL EDITOR In this interesting article the authors describe a new AFM sampling method to allow better images on whole-animal mounts such as C. elegans. This method would generate more information and in the future may be useful for differentiating even individual animals with different genetic backgrounds.
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Affiliation(s)
- Michael J Allen
- Center for Nanomedicine, Section of Pulmonary and Critical Care, Department of Medicine, University of Chicago, Chicago, IL, USA
| | - Rajani Kanteti
- Section of Hematology and Oncology, Department of Medicine, University of Chicago, Chicago, IL, USA
| | - Jacob J Riehm
- Center for Nanomedicine, Section of Pulmonary and Critical Care, Department of Medicine, University of Chicago, Chicago, IL, USA
| | - Essam El-Hashani
- Section of Hematology and Oncology, Department of Medicine, University of Chicago, Chicago, IL, USA
| | - Ravi Salgia
- Section of Hematology and Oncology, Department of Medicine, University of Chicago, Chicago, IL, USA.
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Backholm M, Ryu WS, Dalnoki-Veress K. The nematode C. elegans as a complex viscoelastic fluid. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2015; 38:118. [PMID: 25957177 DOI: 10.1140/epje/i2015-15036-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Revised: 03/13/2015] [Accepted: 03/13/2015] [Indexed: 06/04/2023]
Abstract
The viscoelastic material properties of the model organism C. elegans were probed with a micropipette deflection technique and modelled with the standard linear solid model. Dynamic relaxation measurements were performed on the millimetric nematode to investigate its viscous characteristics in detail. We show that the internal properties of C. elegans can not be fully described by a simple Newtonian fluid. Instead, a power-law fluid model was implemented and shown to be in excellent agreement with experimental results. The nematode exhibits shear thinning properties and its complex fluid characteristics were quantified. The bending-rate dependence of the internal damping coefficient of C. elegans could affect its gait modulation in different external environments.
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Affiliation(s)
- Matilda Backholm
- Department of Physics & Astronomy and the Brockhouse Institute for Materials Research, McMaster University, Hamilton, ON, Canada
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Gilpin W, Uppaluri S, Brangwynne CP. Worms under Pressure: Bulk Mechanical Properties of C. elegans Are Independent of the Cuticle. Biophys J 2015; 108:1887-98. [PMID: 25902429 PMCID: PMC4407266 DOI: 10.1016/j.bpj.2015.03.020] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2014] [Revised: 01/14/2015] [Accepted: 03/09/2015] [Indexed: 01/10/2023] Open
Abstract
The mechanical properties of cells and tissues play a well-known role in physiology and disease. The model organism Caenorhabditis elegans exhibits mechanical properties that are still poorly understood, but are thought to be dominated by its collagen-rich outer cuticle. To our knowledge, we use a novel microfluidic technique to reveal that the worm responds linearly to low applied hydrostatic stress, exhibiting a volumetric compression with a bulk modulus, κ = 140 ± 20 kPa; applying negative pressures leads to volumetric expansion of the worm, with a similar bulk modulus. Surprisingly, however, we find that a variety of collagen mutants and pharmacological perturbations targeting the cuticle do not impact the bulk modulus. Moreover, the worm exhibits dramatic stiffening at higher stresses-behavior that is also independent of the cuticle. The stress-strain curves for all conditions can be scaled onto a master equation, suggesting that C. elegans exhibits a universal elastic response dominated by the mechanics of pressurized internal organs.
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Affiliation(s)
- William Gilpin
- Department of Physics, Princeton University, Princeton, New Jersey
| | - Sravanti Uppaluri
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey
| | - Clifford P Brangwynne
- Department of Chemical and Biological Engineering, Princeton University, Princeton, New Jersey.
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Zhen M, Samuel ADT. C. elegans locomotion: small circuits, complex functions. Curr Opin Neurobiol 2015; 33:117-26. [PMID: 25845627 DOI: 10.1016/j.conb.2015.03.009] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2015] [Revised: 03/18/2015] [Accepted: 03/18/2015] [Indexed: 12/20/2022]
Abstract
With 302 neurons in the adult Caenorhabditis elegans nervous system, it should be possible to build models of complex behaviors spanning sensory input to motor output. The logic of the motor circuit is an essential component of such models. Advances in physiological, anatomical, and neurogenetic analysis are revealing a surprisingly complex signaling network in the worm's small motor circuit. We are progressing towards a systems level dissection of the network of premotor interneurons, motor neurons, and muscle cells that move the animal forward and backward in its environment.
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Affiliation(s)
- Mei Zhen
- Lunenfeld-Tanenbaum Research Institute, Mount Sinai Hospital, Toronto, ON, Canada M5G 1X5; Department of Molecular Genetics, University of Toronto, Toronto, ON, Canada M5S 1A8; Department of Physiology, University of Toronto, Toronto, ON, Canada M5S 1A8.
| | - Aravinthan D T Samuel
- Center for Brain Science, Department of Physics, Harvard University, Cambridge, MA 02138, United States.
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Abstract
The sense of touch informs us of the physical properties of our surroundings and is a critical aspect of communication. Before touches are perceived, mechanical signals are transmitted quickly and reliably from the skin's surface to mechano-electrical transduction channels embedded within specialized sensory neurons. We are just beginning to understand how soft tissues participate in force transmission and how they are deformed. Here, we review empirical and theoretical studies of single molecules and molecular ensembles thought to be involved in mechanotransmission and apply the concepts emerging from this work to the sense of touch. We focus on the nematode Caenorhabditis elegans as a well-studied model for touch sensation in which mechanics can be studied on the molecular, cellular, and systems level. Finally, we conclude that force transmission is an emergent property of macromolecular cellular structures that mutually stabilize one another.
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Affiliation(s)
- Michael Krieg
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
| | - Alex Dunn
- Department of Chemical Engineering, Stanford University School of Engineering, Stanford, CA, USA
| | - Miriam B. Goodman
- Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA, USA
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40
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Navis A, Bagnat M. Developing pressures: fluid forces driving morphogenesis. Curr Opin Genet Dev 2015; 32:24-30. [PMID: 25698116 PMCID: PMC4470832 DOI: 10.1016/j.gde.2015.01.010] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2014] [Accepted: 01/27/2015] [Indexed: 11/26/2022]
Abstract
Over several decades genetic studies have unraveled many molecular mechanisms that underlie the signaling networks guiding morphogenesis, but the mechanical forces at work remain much less well understood. Accumulation of fluid within a luminal space can generate outward hydrostatic pressure capable of shaping morphogenesis at several scales, ranging from individual organs to the entire vertebrate body-plan. Here, we focus on recent work that uncovered mechanical roles for fluid secretion during morphogenesis. Identifying the roles and regulation of fluid secretion will be instrumental for understanding the mechanics of morphogenesis as well as many human diseases of complex genetic and environmental origin including secretory diarrheas and scoliosis.
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Affiliation(s)
- Adam Navis
- Department of Cell Biology, Duke University Medical Center, 333B Nanaline Duke Bldg., Box 3709, Durham, NC, USA
| | - Michel Bagnat
- Department of Cell Biology, Duke University Medical Center, 333B Nanaline Duke Bldg., Box 3709, Durham, NC, USA.
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41
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Khare SM, Awasthi A, Venkataraman V, Koushika SP. Colored polydimethylsiloxane micropillar arrays for high throughput measurements of forces applied by genetic model organisms. BIOMICROFLUIDICS 2015; 9:014111. [PMID: 25713693 PMCID: PMC4312341 DOI: 10.1063/1.4906905] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 01/15/2015] [Indexed: 06/04/2023]
Abstract
Measuring forces applied by multi-cellular organisms is valuable in investigating biomechanics of their locomotion. Several technologies have been developed to measure such forces, for example, strain gauges, micro-machined sensors, and calibrated cantilevers. We introduce an innovative combination of techniques as a high throughput screening tool to assess forces applied by multiple genetic model organisms. First, we fabricated colored Polydimethylsiloxane (PDMS) micropillars where the color enhances contrast making it easier to detect and track pillar displacement driven by the organism. Second, we developed a semi-automated graphical user interface to analyze the images for pillar displacement, thus reducing the analysis time for each animal to minutes. The addition of color reduced the Young's modulus of PDMS. Therefore, the dye-PDMS composite was characterized using Yeoh's hyperelastic model and the pillars were calibrated using a silicon based force sensor. We used our device to measure forces exerted by wild type and mutant Caenorhabditis elegans moving on an agarose surface. Wild type C. elegans exert an average force of ∼1 μN on an individual pillar and a total average force of ∼7.68 μN. We show that the middle of C. elegans exerts more force than its extremities. We find that C. elegans mutants with defective body wall muscles apply significantly lower force on individual pillars, while mutants defective in sensing externally applied mechanical forces still apply the same average force per pillar compared to wild type animals. Average forces applied per pillar are independent of the length, diameter, or cuticle stiffness of the animal. We also used the device to measure, for the first time, forces applied by Drosophila melanogaster larvae. Peristaltic waves occurred at 0.4 Hz applying an average force of ∼1.58 μN on a single pillar. Our colored microfluidic device along with its displacement tracking software allows us to measure forces applied by multiple model organisms that crawl or slither to travel through their environment.
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Affiliation(s)
- Siddharth M Khare
- Department of Physics, Indian Institute of Science , Bangalore 560012, India
| | | | - V Venkataraman
- Department of Physics, Indian Institute of Science , Bangalore 560012, India
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Greenblum A, Sznitman R, Fua P, Arratia PE, Sznitman J. Caenorhabditis elegans segmentation using texture-based models for motility phenotyping. IEEE Trans Biomed Eng 2014; 61:2278-89. [PMID: 25051545 DOI: 10.1109/tbme.2014.2298612] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
With widening interests in using model organisms for reverse genetic approaches and biomimmetic microrobotics, motility phenotyping of the nematode Caenorhabditis elegans is expanding across a growing array of locomotive environments. One ongoing bottleneck lies in providing users with automatic nematode segmentations of C. elegans in image sequences featuring complex and dynamic visual cues, a first and necessary step prior to extracting motility phenotypes. Here, we propose to tackle such automatic segmentation challenges by introducing a novel texture factor model (TFM). Our approach revolves around the use of combined intensity- and texture-based features integrated within a probabilistic framework. This strategy first provides a coarse nematode segmentation from which a Markov random field model is used to refine the segmentation by inferring pixels belonging to the nematode using an approximate inference technique. Finally, informative priors can then be estimated and integrated in our framework to provide coherent segmentations across image sequences. We validate our TFM method across a wide range of motility environments. Not only does TFM assure comparative performances to existing segmentation methods on traditional environments featuring static backgrounds, it importantly provides state-of-the-art C. elegans segmentations for dynamic environments such as the recently introduced wet granular media. We show how such segmentations may be used to compute nematode "skeletons" from which motility phenotypes can then be extracted. Overall, our TFM method provides users with a tangible solution to tackle the growing needs of C. elegans segmentation in challenging motility environments.
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Pandya HJ, Chen W, Goodell LA, Foran DJ, Desai JP. Mechanical phenotyping of breast cancer using MEMS: a method to demarcate benign and cancerous breast tissues. LAB ON A CHIP 2014; 14:4523-32. [PMID: 25267099 PMCID: PMC4224189 DOI: 10.1039/c4lc00594e] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The mechanical properties of tissue change significantly during the progression from healthy to malignant. Quantifying the mechanical properties of breast tissue within the tumor microenvironment can help to delineate benign from cancerous stages. In this work, we study high-grade invasive ductal carcinoma in comparison with their matched tumor adjacent areas, which exhibit benign morphology. Such paired tissue cores obtained from eight patients were indented using a MEMS-based piezoresistive microcantilever, which was positioned within pre-designated epithelial and stromal areas of the specimen. Field emission scanning electron microscopy studies on breast tissue cores were performed to understand the microstructural changes from benign to malignant. The normal epithelial tissues appeared compact and organized. The appearance of cancer regions, in comparison, not only revealed increased cellularity but also showed disorganization and increased fenestration. Using this technique, reliable discrimination between epithelial and stromal regions throughout both benign and cancerous breast tissue cores was obtained. The mechanical profiling generated using this method has the potential to be an objective, reproducible, and quantitative indicator for detecting and characterizing breast cancer.
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Affiliation(s)
- Hardik J Pandya
- Department of Mechanical Engineering, Maryland Robotics Center, Institute for Systems Research, University of Maryland, College Park, Maryland 20742, USA.
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Why do sleeping nematodes adopt a hockey-stick-like posture? PLoS One 2014; 9:e101162. [PMID: 25025212 PMCID: PMC4099128 DOI: 10.1371/journal.pone.0101162] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2014] [Accepted: 05/26/2014] [Indexed: 12/31/2022] Open
Abstract
A characteristic posture is considered one of the behavioral hallmarks of sleep, and typically includes functional features such as support for the limbs and shielding of sensory organs. The nematode C. elegans exhibits a sleep-like state during a stage termed lethargus, which precedes ecdysis at the transition between larval stages. A hockey-stick-like posture is commonly observed during lethargus. What might its function be? It was previously noted that during lethargus, C. elegans nematodes abruptly rotate about their longitudinal axis. Plausibly, these “flips” facilitate ecdysis by assisting the disassociation of the old cuticle from the new one. We found that body-posture during lethargus was established using a stereotypical motor program and that body bends during lethargus quiescence were actively maintained. Moreover, flips occurred almost exclusively when the animals exhibited a single body bend, preferentially in the anterior or mid section of the body. We describe a simple biomechanical model that imposes the observed lengths of the longitudinally directed body-wall muscles on an otherwise passive elastic rod. We show that this minimal model is sufficient for generating a rotation about the anterior-posterior body axis. Our analysis suggests that posture during lethargus quiescence may serve a developmental role in facilitating flips and that the control of body wall muscles in anterior and posterior body regions are distinct.
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Lüersen K, Faust U, Gottschling DC, Döring F. Gait-specific adaptation of locomotor activity in response to dietary restriction in Caenorhabditis elegans. ACTA ACUST UNITED AC 2014; 217:2480-8. [PMID: 24803455 DOI: 10.1242/jeb.099382] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Locomotion is crucial for the survival of living organisms, as it allows foraging, flight and mating behaviour. In response to environmental cues, many organisms switch between alternative forms of locomotion, referred to as gaits. The nematode Caenorhabditis elegans exhibits two gaits: swimming in liquids and crawling on dense gels. The kinematics and patterns of muscle activity differ between the two gaits, with swimming being less efficient than crawling. We found that C. elegans when grown on dietary restriction (DR) plates and then tested immediately for swimming activity exhibit an accelerated frequency of body-bending swimming compared with ad libitum-fed worms, resulting in an increased swimming speed. This response is independent of the presence or absence of food bacteria in the assay liquid. In contrast, the crawling speed of DR worms on assay agar plates is decreased and influenced by food availability. Because DR also attenuates the disturbed swimming activity of worms that are deficient in the presynaptic dopamine transporter DAT-1, our data link DR-induced alterations of the swimming gait to synaptic processes. This strongly suggests a biochemical rather than a biomechanical response to DR provoked by changes in the worm's body structure. We conclude that the increase in locomotor activity in response to DR is specific to the swimming gait and might represent a survival strategy, allowing food-deprived nematodes to exit unfavourable environments.
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Affiliation(s)
- Kai Lüersen
- Department of Molecular Prevention, Institute of Human Nutrition and Food Science, Christian-Albrechts-University of Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany
| | - Ulla Faust
- Department of Molecular Prevention, Institute of Human Nutrition and Food Science, Christian-Albrechts-University of Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany
| | - Dieter-Christian Gottschling
- Department of Molecular Prevention, Institute of Human Nutrition and Food Science, Christian-Albrechts-University of Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany
| | - Frank Döring
- Department of Molecular Prevention, Institute of Human Nutrition and Food Science, Christian-Albrechts-University of Kiel, Heinrich-Hecht-Platz 10, 24118 Kiel, Germany
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Gjorgjieva J, Biron D, Haspel G. Neurobiology of Caenorhabditis elegans Locomotion: Where Do We Stand? Bioscience 2014; 64:476-486. [PMID: 26955070 PMCID: PMC4776678 DOI: 10.1093/biosci/biu058] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Animals use a nervous system for locomotion in some stage of their life cycle. The nematode Caenorhabditis elegans, a major animal model for almost all fields of experimental biology, has long been used for detailed studies of genetic and physiological locomotion mechanisms. Of its 959 somatic cells, 302 are neurons that are identifiable by lineage, location, morphology, and neurochemistry in every adult hermaphrodite. Of those, 75 motoneurons innervate body wall muscles that provide the thrust during locomotion. In this Overview, we concentrate on the generation of either forward- or backward-directed motion during crawling and swimming. We describe locomotion behavior, the parts constituting the locomotion system, and the relevant neuronal connectivity. Because it is not yet fully understood how these components combine to generate locomotion, we discuss competing hypotheses and models.
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Affiliation(s)
- Julijana Gjorgjieva
- Julijana Gjorgjieva is a postdoctoral research fellow at the Center for Brain Science of Harvard University, in Cambridge, Massachusetts. She uses theoretical and numerical tools to understand how developing neural circuits wire to perform a particular function, from the mammalian visual system to the motor system of small invertebrates. David Biron is a physicist at the University of Chicago, Illinois. He studies the sleep of the roundworm Caenorhabditis elegans and related problems in biological physics. Gal Haspel ( ) is a neuroethologist at the New Jersey Institute of Technology, in Newark. He studies the activity, connectivity and recovery from injury of the neuronal network that underlie locomotion in the nematode Caenorhabditis elegans
| | - David Biron
- Julijana Gjorgjieva is a postdoctoral research fellow at the Center for Brain Science of Harvard University, in Cambridge, Massachusetts. She uses theoretical and numerical tools to understand how developing neural circuits wire to perform a particular function, from the mammalian visual system to the motor system of small invertebrates. David Biron is a physicist at the University of Chicago, Illinois. He studies the sleep of the roundworm Caenorhabditis elegans and related problems in biological physics. Gal Haspel ( ) is a neuroethologist at the New Jersey Institute of Technology, in Newark. He studies the activity, connectivity and recovery from injury of the neuronal network that underlie locomotion in the nematode Caenorhabditis elegans
| | - Gal Haspel
- Julijana Gjorgjieva is a postdoctoral research fellow at the Center for Brain Science of Harvard University, in Cambridge, Massachusetts. She uses theoretical and numerical tools to understand how developing neural circuits wire to perform a particular function, from the mammalian visual system to the motor system of small invertebrates. David Biron is a physicist at the University of Chicago, Illinois. He studies the sleep of the roundworm Caenorhabditis elegans and related problems in biological physics. Gal Haspel ( ) is a neuroethologist at the New Jersey Institute of Technology, in Newark. He studies the activity, connectivity and recovery from injury of the neuronal network that underlie locomotion in the nematode Caenorhabditis elegans
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O'Reilly LP, Luke CJ, Perlmutter DH, Silverman GA, Pak SC. C. elegans in high-throughput drug discovery. Adv Drug Deliv Rev 2014; 69-70:247-53. [PMID: 24333896 DOI: 10.1016/j.addr.2013.12.001] [Citation(s) in RCA: 161] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 11/29/2013] [Accepted: 12/05/2013] [Indexed: 11/27/2022]
Abstract
Caenorhabditis elegans has been proven to be a useful model organism for investigating molecular and cellular aspects of numerous human diseases. More recently, investigators have explored the use of this organism as a tool for drug discovery. Although earlier drug screens were labor-intensive and low in throughput, recent advances in high-throughput liquid workflows, imaging platforms and data analysis software have made C. elegans a viable option for automated high-throughput drug screens. This review will outline the evolution of C. elegans-based drug screening, discuss the inherent challenges of using C. elegans, and highlight recent technological advances that have paved the way for future drug screens.
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Affiliation(s)
- Linda P O'Reilly
- Department of Pediatrics, Cell Biology and Physiology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224,USA
| | - Cliff J Luke
- Department of Pediatrics, Cell Biology and Physiology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224,USA
| | - David H Perlmutter
- Department of Pediatrics, Cell Biology and Physiology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224,USA
| | - Gary A Silverman
- Department of Pediatrics, Cell Biology and Physiology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224,USA
| | - Stephen C Pak
- Department of Pediatrics, Cell Biology and Physiology, University of Pittsburgh School of Medicine, Children's Hospital of Pittsburgh of UPMC, 4401 Penn Avenue, Pittsburgh, PA 15224,USA.
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Kuo WJ, Sie YS, Chuang HS. Characterizations of kinetic power and propulsion of the nematode Caenorhabditis elegans based on a micro-particle image velocimetry system. BIOMICROFLUIDICS 2014; 8:024116. [PMID: 24803965 PMCID: PMC4000384 DOI: 10.1063/1.4872061] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2014] [Accepted: 04/10/2014] [Indexed: 06/02/2023]
Abstract
Quantifying the motility of micro-organisms is beneficial in understanding their biomechanical properties. This paper presents a simple image-based algorithm to derive the kinetic power and propulsive force of the nematode Caenorhabditis elegans. To avoid unnecessary disturbance, each worm was confined in an aqueous droplet of 0.5 μl. The droplet was sandwiched between two glass slides and sealed with mineral oil to prevent evaporation. For motion visualization, 3-μm fluorescent particles were dispersed in the droplet. Since the droplet formed an isolated environment, the fluid drag and energy loss due to wall frictions were associated with the worm's kinetic power and propulsion. A microparticle image velocimetry system was used to acquire consecutive particle images for fluid analysis. The short-time interval (Δt < 20 ms) between images enabled quasi real-time measurements. A numerical simulation of the flow in a straight channel showed that the relative error of this algorithm was significantly mitigated as the image was divided into small interrogation windows. The time-averaged power and propulsive force of a N2 adult worm over three swimming cycles were estimated to be 5.2 ± 3.1 pW and 1.0 ± 0.8 nN, respectively. In addition, a mutant, KG532 [kin-2(ce179) X], and a wild-type (N2) worm in a viscous medium were investigated. Both cases showed an increase in the kinetic power as compared with the N2 worm in the nematode growth medium due to the hyperactive nature of the kin-2 mutant and the high viscosity medium used. Overall, the technique deals with less sophisticated calculations and is automation possible.
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Affiliation(s)
- Wan-Jung Kuo
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Yue-Syun Sie
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan
| | - Han-Sheng Chuang
- Department of Biomedical Engineering, National Cheng Kung University, Tainan, Taiwan ; Medical Device Innovation Center, National Cheng Kung University, Tainan, Taiwan
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Petzold BC, Park SJ, Mazzochette EA, Goodman MB, Pruitt BL. MEMS-based force-clamp analysis of the role of body stiffness in C. elegans touch sensation. Integr Biol (Camb) 2014; 5:853-64. [PMID: 23598612 DOI: 10.1039/c3ib20293c] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Touch is enabled by mechanoreceptor neurons in the skin and plays an essential role in our everyday lives, but is among the least understood of our five basic senses. Force applied to the skin deforms these neurons and activates ion channels within them. Despite the importance of the mechanics of the skin in determining mechanoreceptor neuron deformation and ultimately touch sensation, the role of mechanics in touch sensitivity is poorly understood. Here, we use the model organism Caenorhabditis elegans to directly test the hypothesis that body mechanics modulate touch sensitivity. We demonstrate a microelectromechanical system (MEMS)-based force clamp that can apply calibrated forces to freely crawling C. elegans worms and measure touch-evoked avoidance responses. This approach reveals that wild-type animals sense forces <1 μN and indentation depths <1 μm. We use both genetic manipulation of the skin and optogenetic modulation of body wall muscles to alter body mechanics. We find that small changes in body stiffness dramatically affect force sensitivity, while having only modest effects on indentation sensitivity. We investigate the theoretical body deformation predicted under applied force and conclude that local mechanical loads induce inward bending deformation of the skin to drive touch sensation in C. elegans.
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Affiliation(s)
- Bryan C Petzold
- Department of Mechanical Engineering, Stanford University School of Engineering, Stanford, California, USA
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Mowrey WR, Bennett JR, Portman DS. Distributed effects of biological sex define sex-typical motor behavior in Caenorhabditis elegans. J Neurosci 2014; 34:1579-91. [PMID: 24478342 PMCID: PMC3905135 DOI: 10.1523/jneurosci.4352-13.2014] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2013] [Revised: 11/05/2013] [Accepted: 11/07/2013] [Indexed: 12/24/2022] Open
Abstract
Sex differences in shared behaviors (for example, locomotion and feeding) are a nearly universal feature of animal biology. Though these behaviors may share underlying neural programs, their kinematics can exhibit robust differences between males and females. The neural underpinnings of these differences are poorly understood because of the often-untested assumption that they are determined by sex-specific body morphology. Here, we address this issue in the nematode Caenorhabditis elegans, which features two sexes with distinct body morphologies but similar locomotor circuitry and body muscle. Quantitative behavioral analysis shows that C. elegans and related nematodes exhibit significant sex differences in the dynamics and geometry of locomotor body waves, such that the male is generally faster. Using a recently proposed model of locomotor wave propagation, we show that sex differences in both body mechanics and the intrinsic dynamics of the motor system can contribute to kinematic differences in distinct mechanical contexts. By genetically sex-reversing the properties of specific tissues and cells, however, we find that sex-specific locomotor frequency in C. elegans is determined primarily by the functional modification of shared sensory neurons. Further, we find that sexual modification of body wall muscle together with the nervous system is required to alter body wave speed. Thus, rather than relying on a single focus of modification, sex differences in motor dynamics require independent modifications to multiple tissue types. Our results suggest shared motor behaviors may be sex-specifically optimized though distributed modifications to several aspects of morphology and physiology.
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Affiliation(s)
| | | | - Douglas S. Portman
- Center for Neural Development and Disease
- Department of Biomedical Genetics, and
- Department of Biology, University of Rochester, School of Medicine and Dentistry, Rochester, New York 14642
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