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Miller WB, Torday JS, Baluška F. The N-space Episenome unifies cellular information space-time within cognition-based evolution. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2019; 150:112-139. [PMID: 31415772 DOI: 10.1016/j.pbiomolbio.2019.08.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Revised: 07/26/2019] [Accepted: 08/09/2019] [Indexed: 02/08/2023]
Abstract
Self-referential cellular homeostasis is maintained by the measured assessment of both internal status and external conditions based within an integrated cellular information field. This cellular field attachment to biologic information space-time coordinates environmental inputs by connecting the cellular senome, as the sum of the sensory experiences of the cell, with its genome and epigenome. In multicellular organisms, individual cellular information fields aggregate into a collective information architectural matrix, termed a N-space Episenome, that enables mutualized organism-wide information management. It is hypothesized that biological organization represents a dual heritable system constituted by both its biological materiality and a conjoining N-space Episenome. It is further proposed that morphogenesis derives from reciprocations between these inter-related facets to yield coordinated multicellular growth and development. The N-space Episenome is conceived as a whole cell informational projection that is heritable, transferable via cell division and essential for the synchronous integration of the diverse self-referential cells that constitute holobionts.
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Affiliation(s)
| | - John S Torday
- Department of Pediatrics, Harbor-UCLA Medical Center, USA.
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102
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Cervera J, Pai VP, Levin M, Mafe S. From non-excitable single-cell to multicellular bioelectrical states supported by ion channels and gap junction proteins: Electrical potentials as distributed controllers. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2019; 149:39-53. [PMID: 31255702 DOI: 10.1016/j.pbiomolbio.2019.06.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Accepted: 06/26/2019] [Indexed: 12/18/2022]
Abstract
Endogenous bioelectric patterns within tissues are an important driver of morphogenesis and a tractable component of a number of disease states. Developing system-level understanding of the dynamics by which non-neural bioelectric circuits regulate complex downstream cascades is a key step towards both, an evolutionary understanding of ion channel genes, and novel strategies in regenerative medicine. An important capability gap is deriving rational modulation strategies targeting individual cells' bioelectric states to achieve global (tissue- or organ-level) outcomes. Here, we develop an ion channel-based model that describes multicellular states on the basis of spatio-temporal patterns of electrical potentials in aggregates of non-excitable cells. The model is of biological interest because modern techniques allow to associate bioelectrical signals with specific ion channel proteins in the cell membrane that are central to embryogenesis, regeneration, and tumorigenesis. As a complementary approach to the usual biochemical description, we have studied four biophysical questions: (i) how can single-cell bioelectrical states be established; (ii) how can a change in the cell potential caused by a transient perturbation of the cell state be maintained after the stimulus is gone (bioelectrical memory); (iii) how can a single-cell contribute to the control of multicellular ensembles based on the spatio-temporal pattern of electrical potentials; and (iv) how can oscillatory patterns arise from the single-cell bioelectrical dynamics. Experimentally, endogenous bioelectric gradients have emerged as instructive agents for morphogenetic processes. In this context, the simulations can guide new procedures that may allow a distributed control of the multicellular ensemble.
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Affiliation(s)
- Javier Cervera
- Dept. Termodinàmica, Universitat de València, E-46100, Burjassot, Spain.
| | - Vaibhav P Pai
- Dept. of Biology and Allen Discovery Center at Tufts University, Medford, MA, 02155-4243, USA
| | - Michael Levin
- Dept. of Biology and Allen Discovery Center at Tufts University, Medford, MA, 02155-4243, USA
| | - Salvador Mafe
- Dept. Termodinàmica, Universitat de València, E-46100, Burjassot, Spain
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103
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Electrochemical patterns during Drosophila oogenesis: ion-transport mechanisms generate stage-specific gradients of pH and membrane potential in the follicle-cell epithelium. BMC DEVELOPMENTAL BIOLOGY 2019; 19:12. [PMID: 31226923 PMCID: PMC6588877 DOI: 10.1186/s12861-019-0192-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 06/06/2019] [Indexed: 12/14/2022]
Abstract
Background Alterations of bioelectrical properties of cells and tissues are known to function as wide-ranging signals during development, regeneration and wound-healing in several species. The Drosophila follicle-cell epithelium provides an appropriate model system for studying the potential role of electrochemical signals, like intracellular pH (pHi) and membrane potential (Vmem), during development. Therefore, we analysed stage-specific gradients of pHi and Vmem as well as their dependence on specific ion-transport mechanisms. Results Using fluorescent indicators, we found distinct alterations of pHi- and Vmem-patterns during stages 8 to 12 of oogenesis. To determine the roles of relevant ion-transport mechanisms in regulating pHi and Vmem and in establishing stage-specific antero-posterior and dorso-ventral gradients, we used inhibitors of Na+/H+-exchangers and Na+-channels (amiloride), V-ATPases (bafilomycin), ATP-sensitive K+-channels (glibenclamide), voltage-dependent L-type Ca2+-channels (verapamil), Cl−-channels (9-anthroic acid) and Na+/K+/2Cl−-cotransporters (furosemide). Either pHi or Vmem or both parameters were affected by each tested inhibitor. While the inhibition of Na+/H+-exchangers (NHE) and amiloride-sensitive Na+-channels or of V-ATPases resulted in relative acidification, inhibiting the other ion-transport mechanisms led to relative alkalisation. The most prominent effects on pHi were obtained by inhibiting Na+/K+/2Cl−-cotransporters or ATP-sensitive K+-channels. Vmem was most efficiently hyperpolarised by inhibiting voltage-dependent L-type Ca2+-channels or ATP-sensitive K+-channels, whereas the impact of the other ion-transport mechanisms was smaller. In case of very prominent effects of inhibitors on pHi and/or Vmem, we also found strong influences on the antero-posterior and dorso-ventral pHi- and/or Vmem-gradients. For example, inhibiting ATP-sensitive K+-channels strongly enhanced both pHi-gradients (increasing alkalisation) and reduced both Vmem-gradients (increasing hyperpolarisation). Similarly, inhibiting Na+/K+/2Cl−-cotransporters strongly enhanced both pHi-gradients and reduced the antero-posterior Vmem-gradient. To minor extents, both pHi-gradients were enhanced and both Vmem-gradients were reduced by inhibiting voltage-dependent L-type Ca2+-channels, whereas only both pHi-gradients were reduced (increasing acidification) by inhibiting V-ATPases or NHE and Na+-channels. Conclusions Our data show that in the Drosophila follicle-cell epithelium stage-specific pHi- and Vmem-gradients develop which result from the activity of several ion-transport mechanisms. These gradients are supposed to represent important bioelectrical cues during oogenesis, e.g., by serving as electrochemical prepatterns in modifying cell polarity and cytoskeletal organisation. Electronic supplementary material The online version of this article (10.1186/s12861-019-0192-x) contains supplementary material, which is available to authorized users.
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104
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Martinez-Corral R, Liu J, Prindle A, Süel GM, Garcia-Ojalvo J. Metabolic basis of brain-like electrical signalling in bacterial communities. Philos Trans R Soc Lond B Biol Sci 2019; 374:20180382. [PMID: 31006362 PMCID: PMC6553584 DOI: 10.1098/rstb.2018.0382] [Citation(s) in RCA: 30] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/04/2019] [Indexed: 12/20/2022] Open
Abstract
Information processing in the mammalian brain relies on a careful regulation of the membrane potential dynamics of its constituent neurons, which propagates across the neuronal tissue via electrical signalling. We recently reported the existence of electrical signalling in a much simpler organism, the bacterium Bacillus subtilis. In dense bacterial communities known as biofilms, nutrient-deprived B. subtilis cells in the interior of the colony use electrical communication to transmit stress signals to the periphery, which interfere with the growth of peripheral cells and reduce nutrient consumption, thereby relieving stress from the interior. Here, we explicitly address the interplay between metabolism and electrophysiology in bacterial biofilms, by introducing a spatially extended mathematical model that combines the metabolic and electrical components of the phenomenon in a discretized reaction-diffusion scheme. The model is experimentally validated by environmental and genetic perturbations, and confirms that metabolic stress is transmitted through the bacterial population via a potassium wave. Interestingly, this behaviour is reminiscent of cortical spreading depression in the brain, characterized by a wave of electrical activity mediated by potassium diffusion that has been linked to various neurological disorders, calling for future studies on the evolutionary link between the two phenomena. This article is part of the theme issue 'Liquid brains, solid brains: How distributed cognitive architectures process information'.
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Affiliation(s)
- Rosa Martinez-Corral
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona Biomedical Research Park, Barcelona 08003, Spain
| | - Jintao Liu
- Center for Infectious Diseases Research and Tsinghua-Peking Center for Life Sciences, School of Medicine, Tsinghua University, Beijing 100084, People's Republic of China
| | - Arthur Prindle
- Department of Biochemistry and Molecular Genetics, Feinberg School of Medicine, Northwestern University, Chicago, IL 60611, USA
- Center for Synthetic Biology, Northwestern University, Evanston, IL 60208, USA
| | - Gürol M. Süel
- Division of Biological Sciences, San Diego Center for Systems Biology and Center for Microbiome Innovation, University of California San Diego, La Jolla, CA 92093, USA
| | - Jordi Garcia-Ojalvo
- Department of Experimental and Health Sciences, Universitat Pompeu Fabra, Barcelona Biomedical Research Park, Barcelona 08003, Spain
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105
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Stratford JP, Edwards CLA, Ghanshyam MJ, Malyshev D, Delise MA, Hayashi Y, Asally M. Electrically induced bacterial membrane-potential dynamics correspond to cellular proliferation capacity. Proc Natl Acad Sci U S A 2019; 116:9552-9557. [PMID: 31000597 PMCID: PMC6511025 DOI: 10.1073/pnas.1901788116] [Citation(s) in RCA: 85] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Membrane-potential dynamics mediate bacterial electrical signaling at both intra- and intercellular levels. Membrane potential is also central to cellular proliferation. It is unclear whether the cellular response to external electrical stimuli is influenced by the cellular proliferative capacity. A new strategy enabling electrical stimulation of bacteria with simultaneous monitoring of single-cell membrane-potential dynamics would allow bridging this knowledge gap and further extend electrophysiological studies into the field of microbiology. Here we report that an identical electrical stimulus can cause opposite polarization dynamics depending on cellular proliferation capacity. This was demonstrated using two model organisms, namely Bacillus subtilis and Escherichia coli, and by developing an apparatus enabling exogenous electrical stimulation and single-cell time-lapse microscopy. Using this bespoke apparatus, we show that a 2.5-second electrical stimulation causes hyperpolarization in unperturbed cells. Measurements of intracellular K+ and the deletion of the K+ channel suggested that the hyperpolarization response is caused by the K+ efflux through the channel. When cells are preexposed to 400 ± 8 nm wavelength light, the same electrical stimulation depolarizes cells instead of causing hyperpolarization. A mathematical model extended from the FitzHugh-Nagumo neuron model suggested that the opposite response dynamics are due to the shift in resting membrane potential. As predicted by the model, electrical stimulation only induced depolarization when cells are treated with antibiotics, protonophore, or alcohol. Therefore, electrically induced membrane-potential dynamics offer a reliable approach for rapid detection of proliferative bacteria and determination of their sensitivity to antimicrobial agents at the single-cell level.
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Affiliation(s)
- James P Stratford
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
- Warwick Integrative Synthetic Biology Centre, University of Warwick, Coventry, West Midlands, CV4 7AL,United Kingdom
| | - Conor L A Edwards
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
| | - Manjari J Ghanshyam
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
| | - Dmitry Malyshev
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
| | - Marco A Delise
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
| | - Yoshikatsu Hayashi
- Department of Biomedical Engineering, School of Biological Sciences, University of Reading, Reading, Berkshire, RG6 6AH, United Kingdom
| | - Munehiro Asally
- School of Life Sciences, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom;
- Warwick Integrative Synthetic Biology Centre, University of Warwick, Coventry, West Midlands, CV4 7AL,United Kingdom
- Bio-Electrical Engineering Innovation Hub, University of Warwick, Coventry, West Midlands, CV4 7AL, United Kingdom
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106
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Cervera J, Manzanares JA, Mafe S, Levin M. Synchronization of Bioelectric Oscillations in Networks of Nonexcitable Cells: From Single-Cell to Multicellular States. J Phys Chem B 2019; 123:3924-3934. [PMID: 31003574 DOI: 10.1021/acs.jpcb.9b01717] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Biological networks use collective oscillations for information processing tasks. In particular, oscillatory membrane potentials have been observed in nonexcitable cells and bacterial communities where specific ion channel proteins contribute to the bioelectric coordination of large populations. We aim at describing theoretically the oscillatory spatiotemporal patterns that emerge at the multicellular level from the single-cell bioelectric dynamics. To this end, we focus on two key questions: (i) What single-cell properties are relevant to multicellular behavior? (ii) What properties defined at the multicellular level can allow an external control of the bioelectric dynamics? In particular, we explore the interplay between transcriptional and translational dynamics and membrane potential dynamics in a model multicellular ensemble, describe the spatiotemporal patterns that arise when the average electric potential allows groups of cells to act as a coordinated multicellular patch, and characterize the resulting synchronization phenomena. The simulations concern bioelectric networks and collective communication across different scales based on oscillatory and synchronization phenomena, thus shedding light on the physiological dynamics of a wide range of endogenous contexts across embryogenesis and regeneration.
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Affiliation(s)
- Javier Cervera
- Departament de Termodinàmica, Facultat de Física , Universitat de València , E-46100 Burjassot , Spain
| | - José Antonio Manzanares
- Departament de Termodinàmica, Facultat de Física , Universitat de València , E-46100 Burjassot , Spain
| | - Salvador Mafe
- Departament de Termodinàmica, Facultat de Física , Universitat de València , E-46100 Burjassot , Spain
| | - Michael Levin
- Allen Discovery Center at Tufts University, Department of Biology , Tufts University Medford , Massachusetts 02155-4243 , United States
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107
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Abstract
During morphogenesis, cells communicate with each other to shape tissues and organs. Several lines of recent evidence indicate that ion channels play a key role in cellular signaling and tissue morphogenesis. However, little is known about the scope of specific ion-channel types that impinge upon developmental pathways. The Drosophila melanogaster wing is an excellent model in which to address this problem as wing vein patterning is acutely sensitive to changes in developmental pathways. We conducted a screen of 180 ion channels expressed in the wing using loss-of-function mutant and RNAi lines. Here we identify 44 candidates that significantly impacted development of the Drosophila melanogaster wing. Calcium, sodium, potassium, chloride, and ligand-gated cation channels were all identified in our screen, suggesting that a wide variety of ion channel types are important for development. Ion channels belonging to the pickpocket family, the ionotropic receptor family, and the bestrophin family were highly represented among the candidates of our screen. Seven new ion channels with human orthologs that have been implicated in human channelopathies were also identified. Many of the human orthologs of the channels identified in our screen are targets of common general anesthetics, anti-seizure and anti-hypertension drugs, as well as alcohol and nicotine. Our results confirm the importance of ion channels in morphogenesis and identify a number of ion channels that will provide the basis for future studies to understand the role of ion channels in development.
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108
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109
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Sun Y, Reid B, Ferreira F, Luxardi G, Ma L, Lokken KL, Zhu K, Xu G, Sun Y, Ryzhuk V, Guo BP, Lebrilla CB, Maverakis E, Mogilner A, Zhao M. Infection-generated electric field in gut epithelium drives bidirectional migration of macrophages. PLoS Biol 2019; 17:e3000044. [PMID: 30964858 PMCID: PMC6456179 DOI: 10.1371/journal.pbio.3000044] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2018] [Accepted: 03/05/2019] [Indexed: 12/13/2022] Open
Abstract
Many bacterial pathogens hijack macrophages to egress from the port of entry to the lymphatic drainage and/or bloodstream, causing dissemination of life-threatening infections. However, the underlying mechanisms are not well understood. Here, we report that Salmonella infection generates directional electric fields (EFs) in the follicle-associated epithelium of mouse cecum. In vitro application of an EF, mimicking the infection-generated electric field (IGEF), induces directional migration of primary mouse macrophages to the anode, which is reversed to the cathode upon Salmonella infection. This infection-dependent directional switch is independent of the Salmonella pathogenicity island 1 (SPI-1) type III secretion system. The switch is accompanied by a reduction of sialic acids on glycosylated surface components during phagocytosis of bacteria, which is absent in macrophages challenged by microspheres. Moreover, enzymatic cleavage of terminally exposed sialic acids reduces macrophage surface negativity and severely impairs directional migration of macrophages in response to an EF. Based on these findings, we propose that macrophages are attracted to the site of infection by a combination of chemotaxis and galvanotaxis; after phagocytosis of bacteria, surface electrical properties of the macrophage change, and galvanotaxis directs the cells away from the site of infection.
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Affiliation(s)
- Yaohui Sun
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, United States of America
- Courant Institute and Department of Biology, New York University, New York, New York, United States of America
| | - Brian Reid
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, United States of America
| | - Fernando Ferreira
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, United States of America
- Departamento de Biologia, Centro de Biologia Molecular e Ambiental (CBMA), Universidade do Minho, Braga, Portugal
| | - Guillaume Luxardi
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, United States of America
| | - Li Ma
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, United States of America
- Skin and Cosmetic Research Department, Shanghai Skin Disease Hospital, Shanghai, China
| | - Kristen L. Lokken
- Department of Microbiology and Immunology, School of Medicine, University of California, Davis, Davis, California, United States of America
| | - Kan Zhu
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, United States of America
| | - Gege Xu
- Department of Chemistry, University of California, Davis, Davis, California, United States of America
| | - Yuxin Sun
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, United States of America
| | - Volodymyr Ryzhuk
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, United States of America
| | - Betty P. Guo
- Office of Research, School of Medicine, University of California, Davis, Davis, California, United States of America
| | - Carlito B. Lebrilla
- Department of Chemistry, University of California, Davis, Davis, California, United States of America
| | - Emanual Maverakis
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, United States of America
| | - Alex Mogilner
- Courant Institute and Department of Biology, New York University, New York, New York, United States of America
| | - Min Zhao
- Department of Dermatology, School of Medicine, University of California, Davis, Sacramento, California, United States of America
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110
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Electrotaxis of Glioblastoma and Medulloblastoma Spheroidal Aggregates. Sci Rep 2019; 9:5309. [PMID: 30926929 PMCID: PMC6441013 DOI: 10.1038/s41598-019-41505-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Accepted: 02/26/2019] [Indexed: 11/08/2022] Open
Abstract
Treatment of neuroepithelial cancers remains a daunting clinical challenge, particularly due to an inability to address rampant invasion deep into eloquent regions of the brain. Given the lack of access, and the dispersed nature of brain tumor cells, we explore the possibility of electric fields inducing directed tumor cell migration. In this study we investigate the properties of populations of brain cancer undergoing electrotaxis, a phenomenon whereby cells are directed to migrate under control of an electrical field. We investigate two cell lines for glioblastoma and medulloblastoma (U87mg & DAOY, respectively), plated as spheroidal aggregates in Matrigel-filled electrotaxis channels, and report opposing electrotactic responses. To further understand electrotactic migration of tumor cells, we performed RNA-sequencing for pathway discovery to identify signaling that is differentially affected by the exposure of direct-current electrical fields. Further, using selective pharmacological inhibition assays, focused on the PI3K/mTOR/AKT signaling axis, we validate whether there is a causal relationship to electrotaxis and these mechanisms of action. We find that U87 mg electrotaxis is abolished under pharmacological inhibition of PI3Kγ, mTOR, AKT and ErbB2 signaling, whereas DAOY cell electrotaxis was not attenuated by these or other pathways evaluated.
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111
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Levin M, Pietak AM, Bischof J. Planarian regeneration as a model of anatomical homeostasis: Recent progress in biophysical and computational approaches. Semin Cell Dev Biol 2019; 87:125-144. [PMID: 29635019 PMCID: PMC6234102 DOI: 10.1016/j.semcdb.2018.04.003] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 04/03/2018] [Accepted: 04/06/2018] [Indexed: 12/22/2022]
Abstract
Planarian behavior, physiology, and pattern control offer profound lessons for regenerative medicine, evolutionary biology, morphogenetic engineering, robotics, and unconventional computation. Despite recent advances in the molecular genetics of stem cell differentiation, this model organism's remarkable anatomical homeostasis provokes us with truly fundamental puzzles about the origin of large-scale shape and its relationship to the genome. In this review article, we first highlight several deep mysteries about planarian regeneration in the context of the current paradigm in this field. We then review recent progress in understanding of the physiological control of an endogenous, bioelectric pattern memory that guides regeneration, and how modulating this memory can permanently alter the flatworm's target morphology. Finally, we focus on computational approaches that complement reductive pathway analysis with synthetic, systems-level understanding of morphological decision-making. We analyze existing models of planarian pattern control and highlight recent successes and remaining knowledge gaps in this interdisciplinary frontier field.
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Affiliation(s)
- Michael Levin
- Allen Discovery Center at Tufts University, Medford, MA 02155, United States; Biology Department, Tufts University, Medford, MA 02155, United States.
| | - Alexis M Pietak
- Allen Discovery Center at Tufts University, Medford, MA 02155, United States
| | - Johanna Bischof
- Allen Discovery Center at Tufts University, Medford, MA 02155, United States; Biology Department, Tufts University, Medford, MA 02155, United States
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112
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Abstract
How a single fertilized egg develops into a complex multicellular organism is one of the great mysteries of life. Developmental biology textbooks describe cascades of ligands, receptors, kinases, and transcription factors that designate proliferation, migration, and ultimately fate of cells organized into a multicellular organism. Recently, it has become apparent that ion channels are integral to the process of developmental signaling. Ion channels provide bioelectric signals that must intersect with the known developmental signaling pathways. We review some evidence that bioelectric signaling contributes to bone morphogenetic protein signaling.
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Affiliation(s)
- Laura Faith George
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado
| | - Trevor Isner
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado
| | - Emily Anne Bates
- Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado
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113
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Baluška F, Reber A. Sentience and Consciousness in Single Cells: How the First Minds Emerged in Unicellular Species. Bioessays 2019; 41:e1800229. [PMID: 30714631 DOI: 10.1002/bies.201800229] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2018] [Revised: 12/06/2018] [Indexed: 12/13/2022]
Abstract
A reductionistic, bottom-up, cellular-based concept of the origins of sentience and consciousness has been put forward. Because all life is based on cells, any evolutionary theory of the emergence of sentience and consciousness must be grounded in mechanisms that take place in prokaryotes, the simplest unicellular species. It has been posited that subjective awareness is a fundamental property of cellular life. It emerges as an inherent feature of, and contemporaneously with, the very first life-forms. All other varieties of mentation are the result of evolutionary mechanisms based on this singular event. Therefore, all forms of sentience and consciousness evolve from this original instantiation in prokaryotes. It has also been identified that three cellular structures and mechanisms that likely play critical roles here are excitable membranes, oscillating cytoskeletal polymers, and structurally flexible proteins. Finally, basic biophysical principles are proposed to guide those processes that underly the emergence of supracellular sentience from cellular sentience in multicellular organisms.
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Affiliation(s)
- František Baluška
- Institute of Cellular and Molecular Botany, University of Bonn, 53115 Bonn, Germany
| | - Arthur Reber
- Department of Psychology, University of British Columbia, Vancouver, Canada
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114
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Durant F, Bischof J, Fields C, Morokuma J, LaPalme J, Hoi A, Levin M. The Role of Early Bioelectric Signals in the Regeneration of Planarian Anterior/Posterior Polarity. Biophys J 2019; 116:948-961. [PMID: 30799071 DOI: 10.1016/j.bpj.2019.01.029] [Citation(s) in RCA: 55] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 01/11/2019] [Accepted: 01/16/2019] [Indexed: 01/14/2023] Open
Abstract
Axial patterning during planarian regeneration relies on a transcriptional circuit that confers distinct positional information on the two ends of an amputated fragment. The earliest known elements of this system begin demarcating differences between anterior and posterior wounds by 6 h postamputation. However, it is still unknown what upstream events break the axial symmetry, allowing a mutual repressor system to establish invariant, distinct biochemical states at the anterior and posterior ends. Here, we show that bioelectric signaling at 3 h is crucial for the formation of proper anterior-posterior polarity in planaria. Briefly manipulating the endogenous bioelectric state by depolarizing the injured tissue during the first 3 h of regeneration alters gene expression by 6 h postamputation and leads to a double-headed phenotype upon regeneration despite confirmed washout of ionophores from tissue. These data reveal a primary functional role for resting membrane potential taking place within the first 3 h after injury and kick-starting the downstream pattern of events that elaborate anatomy over the following 10 days. We propose a simple model of molecular-genetic mechanisms to explain how physiological events taking place immediately after injury regulate the spatial distribution of downstream gene expression and anatomy of regenerating planaria.
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Affiliation(s)
- Fallon Durant
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Johanna Bischof
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Chris Fields
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Junji Morokuma
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Joshua LaPalme
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Alison Hoi
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts
| | - Michael Levin
- Allen Discovery Center at Tufts University, Department of Biology, Tufts University, Medford, Massachusetts.
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115
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Churchill CDM, Winter P, Tuszynski JA, Levin M. EDEn-Electroceutical Design Environment: Ion Channel Tissue Expression Database with Small Molecule Modulators. iScience 2019; 11:42-56. [PMID: 30590250 PMCID: PMC6308252 DOI: 10.1016/j.isci.2018.12.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2018] [Revised: 10/22/2018] [Accepted: 12/06/2018] [Indexed: 02/06/2023] Open
Abstract
The emerging field of bioelectricity has revealed numerous new roles for ion channels beyond the nervous system, which can be exploited for applications in regenerative medicine. Developing such biomedical interventions for birth defects, cancer, traumatic injury, and bioengineering first requires knowledge of ion channel targets expressed in tissues of interest. This information can then be used to select combinations of small molecule inhibitors and/or activators that manipulate the bioelectric state. Here, we provide an overview of electroceutical design environment (EDEn), the first bioinformatic platform that facilitates the design of such therapeutic strategies. This database includes information on ion channels and ion pumps, linked to known chemical modulators and their properties. The database also provides information about the expression levels of the ion channels in over 100 tissue types. The graphical interface allows the user to readily identify chemical entities that can alter the electrical properties of target cells and tissues.
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Affiliation(s)
| | - Philip Winter
- Department of Oncology, University of Alberta, Edmonton, AB T6G 1Z2, Canada
| | - Jack A Tuszynski
- Department of Physics, University of Alberta, Edmonton, AB T6G 2E1, Canada; Department of Oncology, University of Alberta, Edmonton, AB T6G 1Z2, Canada
| | - Michael Levin
- Allen Discovery Center, Tufts University, 200 Boston Avenue, Suite 4600, Medford, MA 02155, USA.
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116
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Cervera J, Manzanares JA, Mafe S. Cell-cell bioelectrical interactions and local heterogeneities in genetic networks: a model for the stabilization of single-cell states and multicellular oscillations. Phys Chem Chem Phys 2019; 20:9343-9354. [PMID: 29564429 DOI: 10.1039/c8cp00648b] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Genetic networks operate in the presence of local heterogeneities in single-cell transcription and translation rates. Bioelectrical networks and spatio-temporal maps of cell electric potentials can influence multicellular ensembles. Could cell-cell bioelectrical interactions mediated by intercellular gap junctions contribute to the stabilization of multicellular states against local genetic heterogeneities? We theoretically analyze this question on the basis of two well-established experimental facts: (i) the membrane potential is a reliable read-out of the single-cell electrical state and (ii) when the cells are coupled together, their individual cell potentials can be influenced by ensemble-averaged electrical potentials. We propose a minimal biophysical model for the coupling between genetic and bioelectrical networks that associates the local changes occurring in the transcription and translation rates of an ion channel protein with abnormally low (depolarized) cell potentials. We then analyze the conditions under which the depolarization of a small region (patch) in a multicellular ensemble can be reverted by its bioelectrical coupling with the (normally polarized) neighboring cells. We show also that the coupling between genetic and bioelectric networks of non-excitable cells, modulated by average electric potentials at the multicellular ensemble level, can produce oscillatory phenomena. The simulations show the importance of single-cell potentials characteristic of polarized and depolarized states, the relative sizes of the abnormally polarized patch and the rest of the normally polarized ensemble, and intercellular coupling.
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Affiliation(s)
- Javier Cervera
- Dept. Termodinàmica, Fac. Física, Universitat de València, 46100 Burjassot, Spain.
| | - José A Manzanares
- Dept. Termodinàmica, Fac. Física, Universitat de València, 46100 Burjassot, Spain.
| | - Salvador Mafe
- Dept. Termodinàmica, Fac. Física, Universitat de València, 46100 Burjassot, Spain.
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117
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Becchetti A, Petroni G, Arcangeli A. Ion Channel Conformations Regulate Integrin-Dependent Signaling. Trends Cell Biol 2019; 29:298-307. [PMID: 30635161 DOI: 10.1016/j.tcb.2018.12.005] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2018] [Revised: 12/16/2018] [Accepted: 12/18/2018] [Indexed: 01/12/2023]
Abstract
Cell-matrix adhesion determines the choice between different cell fates and is accompanied by substantial changes in ion transport. The greatest evidence is the bidirectional interplay occurring between integrin receptors and K+ channels. These proteins can form signaling hubs that regulate cell proliferation, differentiation, and migration in normal and neoplastic tissue. Recent results show that the physical interaction with integrins determines the balance of the open and closed K+ channel states, and individual channel conformations regulate distinct downstream pathways. We propose a model of how these mechanisms regulate proliferation and metastasis in cancer cells. In particular, we suggest that the neoplastic progression could be modulated by targeting specific ion channel conformations.
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Affiliation(s)
- Andrea Becchetti
- Department of Biotechnology and Biosciences, University of Milano-Bicocca, 20126 Milano, Italy.
| | - Giulia Petroni
- Department of Experimental and Clinical Medicine, University of Florence, 50134 Firenze, Italy
| | - Annarosa Arcangeli
- Department of Experimental and Clinical Medicine, University of Florence, 50134 Firenze, Italy
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118
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Kamm RD, Bashir R, Arora N, Dar RD, Gillette MU, Griffith LG, Kemp ML, Kinlaw K, Levin M, Martin AC, McDevitt TC, Nerem RM, Powers MJ, Saif TA, Sharpe J, Takayama S, Takeuchi S, Weiss R, Ye K, Yevick HG, Zaman MH. Perspective: The promise of multi-cellular engineered living systems. APL Bioeng 2018; 2:040901. [PMID: 31069321 PMCID: PMC6481725 DOI: 10.1063/1.5038337] [Citation(s) in RCA: 84] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 09/18/2018] [Indexed: 12/31/2022] Open
Abstract
Recent technological breakthroughs in our ability to derive and differentiate induced pluripotent stem cells, organoid biology, organ-on-chip assays, and 3-D bioprinting have all contributed to a heightened interest in the design, assembly, and manufacture of living systems with a broad range of potential uses. This white paper summarizes the state of the emerging field of "multi-cellular engineered living systems," which are composed of interacting cell populations. Recent accomplishments are described, focusing on current and potential applications, as well as barriers to future advances, and the outlook for longer term benefits and potential ethical issues that need to be considered.
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Affiliation(s)
- Roger D. Kamm
- Massachusetts Institute of Technology, Boston, Massachusetts 02139, USA
| | - Rashid Bashir
- University of Illinois at Urbana-Champaign, Urbana, Illinois 61820, USA
| | - Natasha Arora
- Massachusetts Institute of Technology, Boston, Massachusetts 02139, USA
| | - Roy D. Dar
- University of Illinois at Urbana-Champaign, Urbana, Illinois 61820, USA
| | | | - Linda G. Griffith
- Massachusetts Institute of Technology, Boston, Massachusetts 02139, USA
| | - Melissa L. Kemp
- Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | | | | | - Adam C. Martin
- Massachusetts Institute of Technology, Boston, Massachusetts 02139, USA
| | | | - Robert M. Nerem
- Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - Mark J. Powers
- Thermo Fisher Scientific, Frederick, Maryland 21704, USA
| | - Taher A. Saif
- University of Illinois at Urbana-Champaign, Urbana, Illinois 61820, USA
| | - James Sharpe
- EMBL Barcelona, European Molecular Biology Laboratory, Barcelona 08003, Spain
| | | | | | - Ron Weiss
- Massachusetts Institute of Technology, Boston, Massachusetts 02139, USA
| | - Kaiming Ye
- Binghamton University, Binghamton, New York 13902, USA
| | - Hannah G. Yevick
- Massachusetts Institute of Technology, Boston, Massachusetts 02139, USA
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119
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Ferenc NN, Levin M. Effects of Ivermectin Exposure on Regeneration of D. dorotocephala Planaria: Exploiting Human-Approved Ion Channel Drugs as Morphoceuticals. Macromol Biosci 2018; 19:e1800237. [PMID: 30485697 DOI: 10.1002/mabi.201800237] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2018] [Revised: 10/22/2018] [Indexed: 01/19/2023]
Abstract
Transformative applications in regenerative medicine await increased control of processes implementing repair and remodeling of complex living structures. Recent work reveals ion channel drugs as a powerful toolkit for modulating endogenous bioelectric circuits that control growth and form in vivo and in vitro. It is therefore especially important to develop assays in model systems that will enable the testing of these "morphoceuticals"-compounds with predictable effects on anatomical structure. The regenerative planaria are an ideal model system for this purpose. Several studies have shown a role for bioelectric signaling in planarian regeneration, but these have focused on Dugesia japonica and Schmidtea mediterranea. It is not known how the alterations of ion channel activity would affect regeneration in other species of planaria-an important aspect of building robust computational models of bioelectric circuits. Here, the effect of ivermectin (IVM), a chloride channel opener drug commonly used to combat heartworm is tested, on regeneration in a new species of planaria: Dugesia dorotocephala. Exposure to IVM during regeneration results in patterning abnormalities, such as bifurcated tails with partial heads, as well as delayed regeneration. These data extend our understanding of the effects of human-approved ion channel drugs on regenerative processes.
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Affiliation(s)
- Nina N Ferenc
- Chemistry Department, Westfield High School, Chantilly, VA, 20151, USA
| | - Michael Levin
- Allen Discovery Center at Tufts University, 200 Boston Ave., Medford, MA, 02155, USA
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120
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Hardwick LJA, Philpott A. Xenopus Models of Cancer: Expanding the Oncologist's Toolbox. Front Physiol 2018; 9:1660. [PMID: 30538639 PMCID: PMC6277521 DOI: 10.3389/fphys.2018.01660] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2018] [Accepted: 11/02/2018] [Indexed: 01/06/2023] Open
Abstract
The use of the Xenopus model system has provided diverse contributions to cancer research, not least because of the striking parallels between tumour pathogenesis and early embryo development. Cell cycle regulation, signalling pathways, and cell behaviours such as migration are frequently perturbed in cancers; all have been investigated using Xenopus, and these developmental events can additionally act as an assay for drug development studies. In this mini-review, we focus our discussion primarily on whole embryo Xenopus models informing cancer biology; the contributions to date and future potential. Insights into tumour immunity, oncogene function, and visualisation of vascular responses during tumour formation have all been achieved with naturally occurring tumours and induced-tumour-like-structures in Xenopus. Finally, as we are now entering the era of genetically modified Xenopus models, we can harness genome editing techniques to recapitulate human disease through creating embryos with analogous genetic abnormalities. With the speed, versatility and accessibility that epitomise the Xenopus system, this new range of pre-clinical Xenopus models has great potential to advance our mechanistic understanding of oncogenesis and provide an early in vivo model for chemotherapeutic development.
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Affiliation(s)
- Laura J A Hardwick
- Philpott Lab, Hutchison/MRC Research Centre, Department of Oncology, University of Cambridge, Cambridge, United Kingdom.,Wellcome MRC Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom.,Peterhouse, University of Cambridge, Cambridge, United Kingdom
| | - Anna Philpott
- Philpott Lab, Hutchison/MRC Research Centre, Department of Oncology, University of Cambridge, Cambridge, United Kingdom.,Wellcome MRC Stem Cell Institute, University of Cambridge, Cambridge, United Kingdom
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121
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Cervera J, Meseguer S, Mafe S. Intercellular Connectivity and Multicellular Bioelectric Oscillations in Nonexcitable Cells: A Biophysical Model. ACS OMEGA 2018; 3:13567-13575. [PMID: 30411043 PMCID: PMC6217649 DOI: 10.1021/acsomega.8b01514] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 10/08/2018] [Indexed: 05/28/2023]
Abstract
Bioelectricity is emerging as a crucial mechanism for signal transmission and processing from the single-cell level to multicellular domains. We explore theoretically the oscillatory dynamics that result from the coupling between the genetic and bioelectric descriptions of nonexcitable cells in multicellular ensembles, connecting the genetic prepatterns defined over the ensemble with the resulting spatio-temporal map of cell potentials. These prepatterns assume the existence of a small patch in the ensemble with locally low values of the genetic rate constants that produce a specific ion channel protein whose conductance promotes the cell-polarized state (inward-rectifying channel). In this way, the short-range interactions of the cells within the patch favor the depolarized membrane potential state, whereas the long-range interaction of the patch with the rest of the ensemble promotes the polarized state. The coupling between the local and long-range bioelectric signals allows a binary control of the patch membrane potentials, and alternating cell polarization and depolarization states can be maintained for optimal windows of the number of cells and the intercellular connectivity in the patch. The oscillatory phenomena emerge when the feedback between the single-cell bioelectric and genetic dynamics is coupled at the multicellular level. In this way, the intercellular connectivity acts as a regulatory mechanism for the bioelectrical oscillations. The simulation results are qualitatively discussed in the context of recent experimental studies.
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Affiliation(s)
- Javier Cervera
- Departamento
de Termodinàmica, Facultat de Física,
Universitat de València, E-46100 Burjassot, Spain
| | - Salvador Meseguer
- Laboratory
of RNA Modification and Mitochondrial Diseases, Centro de Investigación Príncipe Felipe, 46012 Valencia, Spain
| | - Salvador Mafe
- Departamento
de Termodinàmica, Facultat de Física,
Universitat de València, E-46100 Burjassot, Spain
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122
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Bioelectrical coupling in multicellular domains regulated by gap junctions: A conceptual approach. Bioelectrochemistry 2018; 123:45-61. [DOI: 10.1016/j.bioelechem.2018.04.013] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 04/13/2018] [Accepted: 04/17/2018] [Indexed: 12/16/2022]
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123
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Zhang P, Turnbull MW. Virus innexin expression in insect cells disrupts cell membrane potential and pH. J Gen Virol 2018; 99:1444-1452. [PMID: 30091698 DOI: 10.1099/jgv.0.001132] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Certain parasitoid wasps are associated with Polydnaviruses, symbiotic viruses that encode virulence factors which are essential to successful parasitization by the wasp of a caterpillar host. Members of one group of Polydnaviruses, the Ichnoviruses, encode a multi-gene family known as Vinnexins. Vinnexins are homologues of insect gap junction genes, and form functional gap junctions that may affect host cell physiology. However, the role of Vinnexins in host pathology and the mechanism by which these affect their caterpillar host are largely unknown. In this article, we generated recombinant baculoviruses to express vinnexins in Spodoptera frugiperda (Sf9) cells. To measure cell physiological changes caused by Vinnexins, cells were probed with a membrane potential-sensitive probe, DiBac4(3), and a pH indicator, carboxyfluorescein diacetate (CFDA). In addition, we utilized carbenoxolone and ouabain, respectively, to probe the role of gap junctions and hemi-channels, and Na+/K+-ATPase in establishing membrane potential in studied cells. Our results indicate that Vinnexins induce cell membrane depolarization and cytoplasmic alkalization to a degree specific to each tested Vinnexin, and that neither Vinnexin hemi-channels nor Na+/K+-ATPase appear to underlie these effects directly. These results hint that members of the Vinnexin protein family may affect host bio-electrical phenomena to disrupt host cell physiology, and that the individual proteins of the family may differentially affect host physiology.
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Affiliation(s)
- Peng Zhang
- 1Department of Plant and Environmental Science, Clemson University, Clemson, SC, USA
| | - Matthew W Turnbull
- 1Department of Plant and Environmental Science, Clemson University, Clemson, SC, USA
- 2Department of Biological Sciences, Clemson University, Clemson, SC, USA
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124
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Baluška F, Miller, Jr WB. Senomic view of the cell: Senome versus Genome. Commun Integr Biol 2018; 11:1-9. [PMID: 30214674 PMCID: PMC6132427 DOI: 10.1080/19420889.2018.1489184] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2018] [Accepted: 06/11/2018] [Indexed: 12/25/2022] Open
Abstract
In the legacy of Thomas Henry Huxley, and his 'epigenetic' philosophy of biology, cells are proposed to represent a trinity of three memory-storing media: Senome, Epigenome, and Genome that together comprise a cell-wide informational architecture. Our current preferential focus on the Genome needs to be complemented by a similar focus on the Epigenome and a here proposed Senome, representing the sum of all the sensory experiences of the cognitive cell and its sensing apparatus. Only then will biology be in a position to embrace the whole complexity of the eukaryotic cell, understanding its true nature which allows the communicative assembly of cells in the form of sentient multicellular organisms.
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125
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Electric Pulses Can Influence Galvanotaxis of Dictyostelium discoideum. BIOMED RESEARCH INTERNATIONAL 2018; 2018:2534625. [PMID: 30186854 PMCID: PMC6112078 DOI: 10.1155/2018/2534625] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Revised: 07/02/2018] [Accepted: 07/31/2018] [Indexed: 01/14/2023]
Abstract
Galvanotaxis, or electrotaxis, plays an essential role in wound healing, embryogenesis, and nerve regeneration. Up until now great efforts have been made to identify the underlying mechanism related to galvanotaxis in various cells under direct current electric field (DCEF) in laboratory studies. However, abundant clinical research shows that non-DCEFs including monopolar or bipolar electric field may also contribute to wound healing and regeneration, although the mechanism remains elusive. Here, we designed a novel electric stimulator and applied DCEF, pulsed DCEF (pDCEF), and bipolar pulse electric field (bpEF) to the cells of Dictyostelium discoideum. The cells had better directional performance under asymmetric 90% duty cycle pDCEF and 80% duty cycle bpEF compared to DCEF, with 10 Hz frequency electric fields eliciting a better cell response than 5 Hz. Interestingly, electrically neutral 50% duty cycle bpEF triggered the highest migration speed, albeit in random directions. The results suggest that electric pulses are vital to galvanotaxis and non-DCEF is promising in both basic and clinical researches.
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126
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Mathews J, Levin M. The body electric 2.0: recent advances in developmental bioelectricity for regenerative and synthetic bioengineering. Curr Opin Biotechnol 2018; 52:134-144. [PMID: 29684787 PMCID: PMC10464502 DOI: 10.1016/j.copbio.2018.03.008] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2017] [Accepted: 03/23/2018] [Indexed: 12/18/2022]
Abstract
Breakthroughs in biomedicine and synthetic bioengineering require predictive, rational control over anatomical structure and function. Recent successes in manipulating cellular and molecular hardware have not been matched by progress in understanding the patterning software implemented during embryogenesis and regeneration. A fundamental capability gap is driving desired changes in growth and form to address birth defects and traumatic injury. Here we review new tools, results, and conceptual advances in an exciting emerging field: endogenous non-neural bioelectric signaling, which enables cellular collectives to make global decisions and implement large-scale pattern homeostasis. Spatially distributed electric circuits regulate gene expression, organ morphogenesis, and body-wide axial patterning. Developmental bioelectricity facilitates the interface to organ-level modular control points that direct patterning in vivo. Cracking the bioelectric code will enable transformative progress in bioengineering and regenerative medicine.
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Affiliation(s)
- Juanita Mathews
- Biology Department, and Allen Discovery Center at Tufts University, Medford, MA 02155, United States
| | - Michael Levin
- Biology Department, and Allen Discovery Center at Tufts University, Medford, MA 02155, United States.
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127
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Birkholz TR, Van Huizen AV, Beane WS. Staying in shape: Planarians as a model for understanding regenerative morphology. Semin Cell Dev Biol 2018; 87:105-115. [PMID: 29738883 DOI: 10.1016/j.semcdb.2018.04.014] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Revised: 04/23/2018] [Accepted: 04/30/2018] [Indexed: 01/18/2023]
Abstract
A key requirement of tissue/organ regeneration is the ability to induce appropriate shape in situ. Regenerated structures need to be integrated with pre-existing ones, through the combined regulation of new tissue growth and the scaling of surrounding tissues. This requires a tightly coordinated control of individual cell functions such as proliferation and stem cell differentiation. While great strides have been made in elucidating cell growth and differentiation mechanisms, how overall shape is generated during regeneration remains unknown. This is because a significant gap remains in our understanding of how cell behaviors are coordinated at the level of tissues and organs. The highly regenerative planarian flatworm has emerged as an important model for defining and understanding regenerative shape mechanisms. This review provides an overview of the main processes known to regulate tissue and animal shape during planarian regeneration: adult stem cell regulation, the reestablishment of body axes, tissue remodeling in pre-existing structures, organ scaling and the maintenance of body proportion, and the bioelectrical regulation of animal morphology. In order for the field to move forward, it will be necessary to identify shape mutants as a means to uncover the molecular mechanisms that synchronize all these separate processes to produce the worm's final regenerative shape. This knowledge will also aid efforts to define the mechanisms that control the termination of regenerative processes.
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Affiliation(s)
- Taylor R Birkholz
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Avenue, Kalamazoo, MI, 49008, USA
| | - Alanna V Van Huizen
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Avenue, Kalamazoo, MI, 49008, USA
| | - Wendy S Beane
- Department of Biological Sciences, Western Michigan University, 1903 W. Michigan Avenue, Kalamazoo, MI, 49008, USA.
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128
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Iwasa SN, Popovic MR, Morshead CM. Skin-derived precursor cells undergo substrate-dependent galvanotaxis that can be modified by neighbouring cells. Stem Cell Res 2018; 31:95-101. [PMID: 30059907 DOI: 10.1016/j.scr.2018.07.019] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2018] [Revised: 06/13/2018] [Accepted: 07/18/2018] [Indexed: 12/28/2022] Open
Abstract
Many cell types respond to electric fields (EFs) through cell migration, a process termed galvanotaxis. The galvanotactic response is critical for development and wound healing. Here we investigate whether skin-derived precursor cells (SKPs), which have the potential to differentiate into mesodermal and peripheral neural cell types, undergo directed migration in the presence of an EF. We found that EF application promotes SKP migration towards the anode. The migratory response is substrate-dependent as SKPs undergo directed migration on laminin and Matrigel, but not collagen. The majority of SKPs express the undifferentiated cell markers nestin, fibronectin and Sox2, after both EF application and in sister cultures with no EF application, suggesting that EFs do not promote cell differentiation. Co-cultures of SKPs and brain-derived neural precursor cells (NPCs), a population of cells that undergo rapid, cathode-directed migration, reveal that in the presence of NPCs an increased percentage of SKPs undergo galvanotaxis, providing evidence that cells can provide cues to modify the galvanotactic response. We propose that a better understanding of SKP migration in the presence of EFs may provide insight into improved strategies for wound repair.
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Affiliation(s)
- Stephanie N Iwasa
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3E1, Canada; Toronto Rehabilitation Institute - University Health Network, Toronto, Ontario M4G 3V9, Canada.
| | - Milos R Popovic
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3E1, Canada; Toronto Rehabilitation Institute - University Health Network, Toronto, Ontario M4G 3V9, Canada.
| | - Cindi M Morshead
- Institute of Biomaterials and Biomedical Engineering, University of Toronto, Toronto, Ontario M5S 3E1, Canada; Toronto Rehabilitation Institute - University Health Network, Toronto, Ontario M4G 3V9, Canada; Department of Surgery, University of Toronto, Toronto, Ontario M5S 3E1, Canada.
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129
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Braun E, Keren K. HydraRegeneration: Closing the Loop with Mechanical Processes in Morphogenesis. Bioessays 2018; 40:e1700204. [DOI: 10.1002/bies.201700204] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2017] [Revised: 04/29/2018] [Indexed: 12/17/2022]
Affiliation(s)
- Erez Braun
- Department of Physics & Network Biology Research LaboratoriesTechnion – Israel Institute of TechnologyHaifaIsrael
| | - Kinneret Keren
- Department of Physics & Network Biology Research LaboratoriesTechnion – Israel Institute of TechnologyHaifaIsrael
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130
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The Double-Aspect of Life. BIOLOGY 2018; 7:biology7020028. [PMID: 29735890 PMCID: PMC6023002 DOI: 10.3390/biology7020028] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 05/02/2018] [Accepted: 05/04/2018] [Indexed: 12/13/2022]
Abstract
Life is based on two aspects: matter and a non-material, electrical component. In a dynamic system of reciprocal causality, matter and the so-called bioelectricity interact with one another, forming a functional unity. The aim of this essay is to summarize evidence for bioelectricity, for the sensitivity of biosystems to external physical factors and for the interactions of internal bioelectricity with internal biochemical structures. I propose non-material information of bioelectrical states to be just as inheritable from generation to generation as is the material genetic code.
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131
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On possible role of DNA electrodynamics in chromatin regulation. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2018; 134:50-54. [DOI: 10.1016/j.pbiomolbio.2017.12.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Revised: 12/22/2017] [Accepted: 12/27/2017] [Indexed: 12/23/2022]
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132
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Involvement of AMP-activated Protein Kinase (AMPK) in Regulation of Cell Membrane Potential in a Gastric Cancer Cell Line. Sci Rep 2018; 8:6028. [PMID: 29662080 PMCID: PMC5902619 DOI: 10.1038/s41598-018-24460-6] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 03/12/2018] [Indexed: 12/26/2022] Open
Abstract
Membrane potential (Vmem) is a key bioelectric property of non-excitable cells that plays important roles in regulating cell proliferation. However, the regulation of Vmem itself remains largely unexplored. We found that, under nutrient starvation, during which cell division is inhibited, MKN45 gastric cancer cells were in a hyperpolarized state associated with a high intracellular chloride concentration. AMP-activated protein kinase (AMPK) activity increased, and expression of cystic fibrosis transmembrane conductance regulator (CFTR) decreased, in nutrient-starved cells. Furthermore, the increase in intracellular chloride concentration level and Vmem hyperpolarization in nutrient-starved cells was suppressed by inhibition of AMPK activity. Intracellular chloride concentrations and hyperpolarization increased after over-activation of AMPK using the specific activator AICAR or suppression of CFTR activity using specific inhibitor GlyH-101. Under these conditions, proliferation of MKN45 cells was inhibited. These results reveal that AMPK controls the dynamic change in Vmem by regulating CFTR and influencing the intracellular chloride concentration, which in turn influences cell-cycle progression. These findings offer new insights into the mechanisms underlying cell-cycle arrest regulated by AMPK and CFTR.
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133
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Fields C, Levin M. Are Planaria Individuals? What Regenerative Biology is Telling Us About the Nature of Multicellularity. Evol Biol 2018. [DOI: 10.1007/s11692-018-9448-9] [Citation(s) in RCA: 33] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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134
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Pai VP, Pietak A, Willocq V, Ye B, Shi NQ, Levin M. HCN2 Rescues brain defects by enforcing endogenous voltage pre-patterns. Nat Commun 2018. [PMID: 29519998 PMCID: PMC5843655 DOI: 10.1038/s41467-018-03334-5] [Citation(s) in RCA: 53] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
Endogenous bioelectrical signaling coordinates cell behaviors toward correct anatomical outcomes. Lack of a model explaining spatialized dynamics of bioelectric states has hindered the understanding of the etiology of some birth defects and the development of predictive interventions. Nicotine, a known neuroteratogen, induces serious defects in brain patterning and learning. Our bio-realistic computational model explains nicotine’s effects via the disruption of endogenous bioelectrical gradients and predicts that exogenous HCN2 ion channels would restore the endogenous bioelectric prepatterns necessary for brain patterning. Voltage mapping in vivo confirms these predictions, and exogenous expression of the HCN2 ion channel rescues nicotine-exposed embryos, resulting in normal brain morphology and molecular marker expression, with near-normal learning capacity. By combining molecular embryology, electrophysiology, and computational modeling, we delineate a biophysical mechanism of developmental brain damage and its functional rescue. The authors have previously shown that membrane voltage can influence embryonic patterning during development. Here, the authors computationally model how nicotine disrupts Xenopus embryogenesis by perturbing voltage gradients, and rescue nicotine-inducted defects with HCN2 channel expression.
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Affiliation(s)
- Vaibhav P Pai
- Allen Discovery Center at Tufts University, Medford, MA, 02155, USA
| | - Alexis Pietak
- Allen Discovery Center at Tufts University, Medford, MA, 02155, USA
| | - Valerie Willocq
- Allen Discovery Center at Tufts University, Medford, MA, 02155, USA
| | - Bin Ye
- Veridian Biotechnology Limited, Biotech Center 2, Hong Kong, China
| | - Nian-Qing Shi
- Department of Developmental, Molecular, and Chemical Biology, Tufts University, Boston, MA, 02111, USA
| | - Michael Levin
- Allen Discovery Center at Tufts University, Medford, MA, 02155, USA.
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135
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Herrera-Rincon C, Levin M. Booting up the organism during development: Pre-behavioral functions of the vertebrate brain in guiding body morphogenesis. Commun Integr Biol 2018; 11:e1433440. [PMID: 29497473 PMCID: PMC5824965 DOI: 10.1080/19420889.2018.1433440] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2017] [Accepted: 01/19/2018] [Indexed: 01/24/2023] Open
Abstract
A recent study in Xenopus laevis embryos showed that the very early brain has important functions long before behavior. While the nascent brain is being constructed, it is required for normal patterning of the muscle and peripheral nerve networks, including those far away from the head. In addition to providing important developmental signals to remote tissues in normal embryogenesis, its presence is also able to render harmless exposure to specific chemicals that normally act as teratogens. These activities of the early brain can be partially compensated for in a brainless embryo by experimental modulation of neurotransmitter and ion channel signaling. Here, we discuss the major findings of this paper in the broader context of developmental physiology, neuroscience, and biomedicine. This novel function of the embryonic brain has significant implications, especially for understanding developmental toxicology and teratogenesis in the context of pharmaceutical and environmental reagents.
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Affiliation(s)
- Celia Herrera-Rincon
- Allen Discovery Center, and Department of Biology, Tufts University, Medford, MA, USA
| | - Michael Levin
- Allen Discovery Center, and Department of Biology, Tufts University, Medford, MA, USA
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136
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Levin M, Martyniuk CJ. The bioelectric code: An ancient computational medium for dynamic control of growth and form. Biosystems 2018; 164:76-93. [PMID: 28855098 PMCID: PMC10464596 DOI: 10.1016/j.biosystems.2017.08.009] [Citation(s) in RCA: 108] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2017] [Revised: 08/20/2017] [Accepted: 08/22/2017] [Indexed: 12/19/2022]
Abstract
What determines large-scale anatomy? DNA does not directly specify geometrical arrangements of tissues and organs, and a process of encoding and decoding for morphogenesis is required. Moreover, many species can regenerate and remodel their structure despite drastic injury. The ability to obtain the correct target morphology from a diversity of initial conditions reveals that the morphogenetic code implements a rich system of pattern-homeostatic processes. Here, we describe an important mechanism by which cellular networks implement pattern regulation and plasticity: bioelectricity. All cells, not only nerves and muscles, produce and sense electrical signals; in vivo, these processes form bioelectric circuits that harness individual cell behaviors toward specific anatomical endpoints. We review emerging progress in reading and re-writing anatomical information encoded in bioelectrical states, and discuss the approaches to this problem from the perspectives of information theory, dynamical systems, and computational neuroscience. Cracking the bioelectric code will enable much-improved control over biological patterning, advancing basic evolutionary developmental biology as well as enabling numerous applications in regenerative medicine and synthetic bioengineering.
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Affiliation(s)
- Michael Levin
- Allen Discovery Center at Tufts University, Biology Department, Tufts University, 200 Boston Avenue, Suite 4600 Medford, MA 02155, USA.
| | - Christopher J Martyniuk
- Department of Physiological Sciences and Center for Environmental and Human Toxicology, University of Florida Genetics Institute, Interdisciplinary Program in Biomedical Sciences Neuroscience, College of Veterinary Medicine, University of Florida, Gainesville, FL, 32611, USA
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137
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McLaughlin KA, Levin M. Bioelectric signaling in regeneration: Mechanisms of ionic controls of growth and form. Dev Biol 2018; 433:177-189. [PMID: 29291972 PMCID: PMC5753428 DOI: 10.1016/j.ydbio.2017.08.032] [Citation(s) in RCA: 132] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2017] [Revised: 08/23/2017] [Accepted: 08/28/2017] [Indexed: 12/11/2022]
Abstract
The ability to control pattern formation is critical for the both the embryonic development of complex structures as well as for the regeneration/repair of damaged or missing tissues and organs. In addition to chemical gradients and gene regulatory networks, endogenous ion flows are key regulators of cell behavior. Not only do bioelectric cues provide information needed for the initial development of structures, they also enable the robust restoration of normal pattern after injury. In order to expand our basic understanding of morphogenetic processes responsible for the repair of complex anatomy, we need to identify the roles of endogenous voltage gradients, ion flows, and electric fields. In complement to the current focus on molecular genetics, decoding the information transduced by bioelectric cues enhances our knowledge of the dynamic control of growth and pattern formation. Recent advances in science and technology place us in an exciting time to elucidate the interplay between molecular-genetic inputs and important biophysical cues that direct the creation of tissues and organs. Moving forward, these new insights enable additional approaches to direct cell behavior and may result in profound advances in augmentation of regenerative capacity.
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Affiliation(s)
- Kelly A McLaughlin
- Allen Discovery Center, Department of Biology, Tufts University, 200 Boston Ave., Suite 4700, Medford, MA 02155, United States.
| | - Michael Levin
- Allen Discovery Center, Department of Biology, Tufts University, 200 Boston Ave., Suite 4700, Medford, MA 02155, United States
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138
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Busse SM, McMillen PT, Levin M. Cross-limb communication during Xenopus hind-limb regenerative response: non-local bioelectric injury signals. Development 2018; 145:dev.164210. [DOI: 10.1242/dev.164210] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Accepted: 07/31/2018] [Indexed: 12/29/2022]
Abstract
Regeneration of damaged body-parts requires coordination of size, shape, location, and orientation of tissue with the rest of the body. It is not currently known how far injury sites communicate with the remaining soma during repair, or what information may emanate from the injury site to other regions. We examined the bioelectric properties (resting potential gradients in the epidermis) of Xenopus froglets undergoing hind-limb amputation and observed that the contralateral (un-damaged) limb exhibits apparent depolarization signals immediately after the opposite hind-limb is amputated. The pattern of depolarization matches that of the amputated limb and is correlated to the position and type of injury, revealing that information about damage is available to remote body tissues and is detectable non-invasively in vivo by monitoring of the bioelectric state. These data extend knowledge about the electrophysiology of regenerative response, identify a novel communication process via long-range spread of injury signaling, a phenomenon which we call bioelectric injury mirroring (BIM), and suggests revisions to regenerative medicine and diagnostic strategies focused entirely on the wound site and to the use of contralateral limbs as controls.
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Affiliation(s)
- Sera M. Busse
- Biology Department and Allen Discovery Center, Tufts University, Medford, MA 02155, USA
| | - Patrick T. McMillen
- Biology Department and Allen Discovery Center, Tufts University, Medford, MA 02155, USA
| | - Michael Levin
- Biology Department and Allen Discovery Center, Tufts University, Medford, MA 02155, USA
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139
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Pezzulo G, Levin M. Embodying Markov blankets: Comment on "Answering Schrödinger's question: A free-energy formulation" by Maxwell James Désormeau Ramstead et al. Phys Life Rev 2017; 24:32-36. [PMID: 29191410 DOI: 10.1016/j.plrev.2017.11.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Accepted: 11/23/2017] [Indexed: 01/03/2023]
Affiliation(s)
- Giovanni Pezzulo
- Institute of Cognitive Sciences and Technologies, National Research Council, Rome, Italy.
| | - Michael Levin
- Allen Discovery Center at Tufts University, Medford, MA, United States
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140
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Fields C, Levin M. Multiscale memory and bioelectric error correction in the cytoplasm-cytoskeleton-membrane system. WILEY INTERDISCIPLINARY REVIEWS-SYSTEMS BIOLOGY AND MEDICINE 2017; 10. [DOI: 10.1002/wsbm.1410] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2017] [Revised: 08/19/2017] [Accepted: 10/04/2017] [Indexed: 12/12/2022]
Affiliation(s)
- Chris Fields
- 21 Rue des Lavandiéres, 11160 Caunes Minervois; France
| | - Michael Levin
- Allen Discovery Center at Tufts University; Medford MA USA
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141
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Pezzulo G, Levin M. Top-down models in biology: explanation and control of complex living systems above the molecular level. J R Soc Interface 2017; 13:rsif.2016.0555. [PMID: 27807271 DOI: 10.1098/rsif.2016.0555] [Citation(s) in RCA: 94] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2016] [Accepted: 10/11/2016] [Indexed: 12/23/2022] Open
Abstract
It is widely assumed in developmental biology and bioengineering that optimal understanding and control of complex living systems follows from models of molecular events. The success of reductionism has overshadowed attempts at top-down models and control policies in biological systems. However, other fields, including physics, engineering and neuroscience, have successfully used the explanations and models at higher levels of organization, including least-action principles in physics and control-theoretic models in computational neuroscience. Exploiting the dynamic regulation of pattern formation in embryogenesis and regeneration requires new approaches to understand how cells cooperate towards large-scale anatomical goal states. Here, we argue that top-down models of pattern homeostasis serve as proof of principle for extending the current paradigm beyond emergence and molecule-level rules. We define top-down control in a biological context, discuss the examples of how cognitive neuroscience and physics exploit these strategies, and illustrate areas in which they may offer significant advantages as complements to the mainstream paradigm. By targeting system controls at multiple levels of organization and demystifying goal-directed (cybernetic) processes, top-down strategies represent a roadmap for using the deep insights of other fields for transformative advances in regenerative medicine and systems bioengineering.
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Affiliation(s)
- Giovanni Pezzulo
- Institute of Cognitive Sciences and Technologies, National Research Council, Rome, Italy
| | - Michael Levin
- Biology Department, Allen Discovery Center at Tufts, Tufts University, Medford, MA 02155, USA
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142
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Abstract
Networks of protoplasmic tubes of organism Physarum polycehpalum are macro-scale structures which optimally span multiple food sources to avoid repellents yet maximize coverage of attractants. When data are presented by configurations of attractants and behaviour of the slime mould is tuned by a range of repellents, the organism preforms computation. It maps given data configuration into a protoplasmic network. To discover physical means of programming the slime mould computers we explore conductivity of the protoplasmic tubes; proposing that the network connectivity of protoplasmic tubes shows pathway-dependent plasticity. To demonstrate this we encourage the slime mould to span a grid of electrodes and apply AC stimuli to the network. Learning and weighted connections within a grid of electrodes is produced using negative and positive voltage stimulation of the network at desired nodes; low frequency (10 Hz) sinusoidal (0.5 V peak-to-peak) voltage increases connectivity between stimulated electrodes while decreasing connectivity elsewhere, high frequency (1000 Hz) sinusoidal (2.5 V peak-to-peak) voltage stimulation decreases network connectivity between stimulated electrodes. We corroborate in a particle model. This phenomenon may be used for computation in the same way that neural networks process information and has the potential to shed light on the dynamics of learning and information processing in non-neural metazoan somatic cell networks.
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