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Pio-Lopez L, Levin M. Morphoceuticals: perspectives for discovery of drugs targeting anatomical control mechanisms in regenerative medicine, cancer and aging. Drug Discov Today 2023; 28:103585. [PMID: 37059328 DOI: 10.1016/j.drudis.2023.103585] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2022] [Revised: 03/18/2023] [Accepted: 04/06/2023] [Indexed: 04/16/2023]
Abstract
Morphoceuticals are a new class of interventions that target the setpoints of anatomical homeostasis for efficient, modular control of growth and form. Here, we focus on a subclass: electroceuticals, which specifically target the cellular bioelectrical interface. Cellular collectives in all tissues form bioelectrical networks via ion channels and gap junctions that process morphogenetic information, controlling gene expression and allowing cell networks to adaptively and dynamically control growth and pattern formation. Recent progress in understanding this physiological control system, including predictive computational models, suggests that targeting bioelectrical interfaces can control embryogenesis and maintain shape against injury, senescence and tumorigenesis. We propose a roadmap for drug discovery focused on manipulating endogenous bioelectric signaling for regenerative medicine, cancer suppression and antiaging therapeutics. Teaser: By taking advantage of the native problem-solving competencies of cells and tissues, a new kind of top-down approach to biomedicine becomes possible. Bioelectricity offers an especially tractable interface for interventions targeting the software of life for regenerative medicine applications.
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Affiliation(s)
- Léo Pio-Lopez
- Allen Discovery Center, Tufts University, Medford, MA, USA
| | - Michael Levin
- Allen Discovery Center, Tufts University, Medford, MA, USA; Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston, MA, 02115, USA.
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2
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Silver BB, Zhang SX, Rabie EM, Nelson CM. Substratum stiffness tunes membrane voltage in mammary epithelial cells. J Cell Sci 2021; 134:jcs256313. [PMID: 34313313 PMCID: PMC8310660 DOI: 10.1242/jcs.256313] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 06/02/2021] [Indexed: 11/20/2022] Open
Abstract
Membrane voltage (Vm) plays a critical role in the regulation of several cellular behaviors, including proliferation, apoptosis and phenotypic plasticity. Many of these behaviors are affected by the stiffness of the underlying extracellular matrix, but the connections between Vm and the mechanical properties of the microenvironment are unclear. Here, we investigated the relationship between matrix stiffness and Vm by culturing mammary epithelial cells on synthetic substrata, the stiffnesses of which mimicked those of the normal mammary gland and breast tumors. Although proliferation is associated with depolarization, we surprisingly observed that cells are hyperpolarized when cultured on stiff substrata, a microenvironmental condition that enhances proliferation. Accordingly, we found that Vm becomes depolarized as stiffness decreases, in a manner dependent on intracellular Ca2+. Furthermore, inhibiting Ca2+-gated Cl- currents attenuates the effects of substratum stiffness on Vm. Specifically, we uncovered a role for cystic fibrosis transmembrane conductance regulator (CFTR) in the regulation of Vm by substratum stiffness. Taken together, these results suggest a novel role for CFTR and membrane voltage in the response of mammary epithelial cells to their mechanical microenvironment.
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Affiliation(s)
- Brian B. Silver
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
| | - Sherry X. Zhang
- Department of Chemical & Biological Engineering, Princeton University, Princeton, NJ 08544, USA
| | - Emann M. Rabie
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
- Graduate School of Biomedical Sciences, Rutgers Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA
| | - Celeste M. Nelson
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
- Department of Chemical & Biological Engineering, Princeton University, Princeton, NJ 08544, USA
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3
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Abstract
Embryogenesis, as well as regeneration, is increasingly recognized to be orchestrated by an interplay of transcriptional and bioelectric networks. Spatiotemporal patterns of resting potentials direct the size, shape, and locations of numerous organ primordia during patterning. These bioelectrical properties are established by the function of ion channels and pumps that set voltage potentials of individual cells, and gap junctions (electrical synapses) that enable physiological states to propagate across tissue networks. Functional experiments to probe the roles of bioelectrical states can be carried out by targeting endogenous ion channels during development. Here, we describe protocols, optimized for the highly tractable Xenopus laevis embryo, for molecular genetic targeting of ion channels and connexins based on CRISPR, and monitoring of resting potential states using voltage-sensing fluorescent dye. Similar strategies can be adapted to other model species.
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Affiliation(s)
- Vasilios Nanos
- Department of Biology, and Allen Discovery Center, Tufts University, Medford, MA, USA
| | - Michael Levin
- Department of Biology, and Allen Discovery Center, Tufts University, Medford, MA, USA.
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4
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Abstract
Modern stem cell research has mainly focused on protein expression and transcriptional networks. However, transmembrane voltage gradients generated by ion channels and transporters have demonstrated to be powerful regulators of cellular processes. These physiological cues exert influence on cell behaviors ranging from differentiation and proliferation to migration and polarity. Bioelectric signaling is a fundamental element of living systems and an untapped reservoir for new discoveries. Dissecting these mechanisms will allow for novel methods of controlling cell fate and open up new opportunities in biomedicine. This review focuses on the role of ion channels and the resting membrane potential in the proliferation and differentiation of skeletal muscle progenitor cells. In addition, findings relevant to this topic are presented and potential implications for tissue engineering and regenerative medicine are discussed.
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Affiliation(s)
- Colin Fennelly
- Department of Neuroscience, Novartis Institutes for BioMedical Research, Inc., Cambridge, Massachusetts
| | - Shay Soker
- Wake Forest Institute for Regenerative Medicine, Winston-Salem, North Carolina.,Wake Forest School of Medicine, Winston-Salem, North Carolina
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5
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Mahmoudinezhad MH, Karkhaneh A, Jadidi K. Effect of PEDOT:PSS in tissue engineering composite scaffold on improvement and maintenance of endothelial cell function. J Biosci 2018; 43:307-319. [PMID: 29872019] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
According to recent research, smart polymers can affect different kind of mammalian cells such as endothelial cells. It is known that conductive polymers have great features, e.g. electrical conductivity, and can help increase electrical cell communication. To clarify the effect of one of these smart materials on endothelial cells, which are not inherently electrically dependent, poly(3, 4-ethylene dioxythiophene) polystyrene sulfonate (PEDOT:PSS) was chosen. Scaffolds were composed of gelatin, alginate, and PEDOT:PSS and made through solvent casting. Human umbilical vein endothelial cells (HUVECs) were cultured on the scaffold with different PEDOT:PSS concentrations. SEM, MTT assay, cell attachment, nitric oxide measurement, real-time PCR and immunohistochemistry analysis were employed to assess endothelial cell responses. Although there was no significant difference in swelling ratio, mass loss, and cell attachment when PEDOT:PSS concentration increased in scaffold construction, cell proliferation noticeably increased after seven days. The cells showed a significant increase in proliferation and NO release to the scaffold with 1% PEDOT:PSS concentration. The results indicated increases in the amount of expression of platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31), kinase insert domain receptor (KDR), vascular-endothelial Cadherin (VE. Cadherin), and von Will brand factor (vWf) in the group which contained a conductive polymer in comparison with the non-conductive scaffold. Therefore, as a conductive polymer, PEDOT:PSS can affect the endothelial cell behaviours.
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Hesam Mahmoudinezhad M, Karkhaneh A, Jadidi K. Effect of PEDOT:PSS in tissue engineering composite scaffold on improvement and maintenance of endothelial cell function. J Biosci 2018. [DOI: 10.1007/s12038-018-9748-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
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7
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Silver BB, Nelson CM. The Bioelectric Code: Reprogramming Cancer and Aging From the Interface of Mechanical and Chemical Microenvironments. Front Cell Dev Biol 2018; 6:21. [PMID: 29560350 PMCID: PMC5845671 DOI: 10.3389/fcell.2018.00021] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2017] [Accepted: 02/15/2018] [Indexed: 12/12/2022] Open
Abstract
Cancer is a complex, heterogeneous group of diseases that can develop through many routes. Broad treatments such as chemotherapy destroy healthy cells in addition to cancerous ones, but more refined strategies that target specific pathways are usually only effective for a limited number of cancer types. This is largely due to the multitude of physiological variables that differ between cells and their surroundings. It is therefore important to understand how nature coordinates these variables into concerted regulation of growth at the tissue scale. The cellular microenvironment might then be manipulated to drive cells toward a desired outcome at the tissue level. One unexpected parameter, cellular membrane voltage (Vm), has been documented to exert control over cellular behavior both in culture and in vivo. Manipulating this fundamental cellular property influences a remarkable array of organism-wide patterning events, producing striking outcomes in both tumorigenesis as well as regeneration. These studies suggest that Vm is not only a key intrinsic cellular property, but also an integral part of the microenvironment that acts in both space and time to guide cellular behavior. As a result, there is considerable interest in manipulating Vm both to treat cancer as well as to regenerate organs damaged or deteriorated during aging. However, such manipulations have produced conflicting outcomes experimentally, which poses a substantial barrier to understanding the fundamentals of bioelectrical reprogramming. Here, we summarize these inconsistencies and discuss how the mechanical microenvironment may impact bioelectric regulation.
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Affiliation(s)
- Brian B Silver
- Department of Molecular Biology, Princeton University, Princeton, NJ, United States
| | - Celeste M Nelson
- Department of Molecular Biology, Princeton University, Princeton, NJ, United States.,Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, United States
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Sullivan KG, Levin M. Inverse Drug Screening of Bioelectric Signaling and Neurotransmitter Roles: Illustrated Using a Xenopus Tail Regeneration Assay. Cold Spring Harb Protoc 2018; 2018:pdb.prot099937. [PMID: 29437995 DOI: 10.1101/pdb.prot099937] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Xenopus embryos and larvae are an ideal model system in which to study the interplay between genetics, physiology, and anatomy in the control of structure and function. An important emerging field is the study of bioelectric signaling, the exchange of ion- and neurotransmitter-mediated messages among all types of cells (not just nerve and muscle cells), in the regulation of growth and form during embryogenesis, regeneration, and cancer. To facilitate the mechanistic investigation of bioelectric events in vivo, it is necessary to identify the endogenous signaling machinery involved in any patterning process of interest. This protocol uses the tail regeneration assay in Xenopus to perform an inverse drug screen; tiers of known compounds are used to probe the involvement of increasingly specific classes of bioelectric and neurotransmitter machinery. By using a hierarchical approach, large classes of targets are ruled out in early rounds, focusing attention on progressively narrower sets of proteins. Such a screen avoids many of the limitations of a molecular-genetic targeting approach and provides a rapid and efficient way to focus on specific targets. Usually, <10 experiments are needed to determine whether bioelectrics and/or neurotransmitter signaling are involved in the process of interest. This protocol describes the strategy in the context of a semiquantitative analysis of tail regeneration but can be applied to any assay in Xenopus or other small aquatic model system (e.g., zebrafish). Given the ever-increasing toolkit of chemical genetics, such screens represent a powerful and versatile methodology for probing the physiological circuits underlying pattern regulation.
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Affiliation(s)
- Kelly G Sullivan
- Biology Department, and Allen Discovery Center at Tufts University, Medford, Massachusetts 02155
| | - Michael Levin
- Biology Department, and Allen Discovery Center at Tufts University, Medford, Massachusetts 02155
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9
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Pietak A, Levin M. Bioelectric gene and reaction networks: computational modelling of genetic, biochemical and bioelectrical dynamics in pattern regulation. J R Soc Interface 2017; 14:20170425. [PMID: 28954851 PMCID: PMC5636277 DOI: 10.1098/rsif.2017.0425] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2017] [Accepted: 08/31/2017] [Indexed: 12/17/2022] Open
Abstract
Gene regulatory networks (GRNs) describe interactions between gene products and transcription factors that control gene expression. In combination with reaction-diffusion models, GRNs have enhanced comprehension of biological pattern formation. However, although it is well known that biological systems exploit an interplay of genetic and physical mechanisms, instructive factors such as transmembrane potential (Vmem) have not been integrated into full GRN models. Here we extend regulatory networks to include bioelectric signalling, developing a novel synthesis: the bioelectricity-integrated gene and reaction (BIGR) network. Using in silico simulations, we highlight the capacity for Vmem to alter steady-state concentrations of key signalling molecules inside and out of cells. We characterize fundamental feedbacks where Vmem both controls, and is in turn regulated by, biochemical signals and thereby demonstrate Vmem homeostatic control, Vmem memory and Vmem controlled state switching. BIGR networks demonstrating hysteresis are identified as a mechanisms through which more complex patterns of stable Vmem spots and stripes, along with correlated concentration patterns, can spontaneously emerge. As further proof of principle, we present and analyse a BIGR network model that mechanistically explains key aspects of the remarkable regenerative powers of creatures such as planarian flatworms. The functional properties of BIGR networks generate the first testable, quantitative hypotheses for biophysical mechanisms underlying the stability and adaptive regulation of anatomical bioelectric pattern.
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Affiliation(s)
- Alexis Pietak
- Allen Discovery Center, Tufts University, Medford, MA, USA
| | - Michael Levin
- Allen Discovery Center, Tufts University, Medford, MA, USA
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10
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Franklin BM, Voss SR, Osborn JL. Ion channel signaling influences cellular proliferation and phagocyte activity during axolotl tail regeneration. Mech Dev 2017; 146:42-54. [PMID: 28603004 PMCID: PMC6386162 DOI: 10.1016/j.mod.2017.06.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 05/24/2017] [Accepted: 06/01/2017] [Indexed: 01/30/2023]
Abstract
Little is known about the potential for ion channels to regulate cellular behaviors during tissue regeneration. Here, we utilized an amphibian tail regeneration assay coupled with a chemical genetic screen to identify ion channel antagonists that altered critical cellular processes during regeneration. Inhibition of multiple ion channels either partially (anoctamin1/Tmem16a, anoctamin2/Tmem16b, KV2.1, KV2.2, L-type CaV channels and H/K ATPases) or completely (GlyR, GABAAR, KV1.5 and SERCA pumps) inhibited tail regeneration. Partial inhibition of tail regeneration by blocking the calcium activated chloride channels, anoctamin1&2, was associated with a reduction of cellular proliferation in tail muscle and mesenchymal regions. Inhibition of anoctamin 1/2 also altered the post-amputation transcriptional response of p44/42 MAPK signaling pathway genes, including decreased expression of erk1/erk2. We also found that complete inhibition via voltage gated K+ channel blockade was associated with diminished phagocyte recruitment to the amputation site. The identification of H+ pumps as required for axolotl tail regeneration supports findings in Xenopus and Planaria models, and more generally, the conservation of ion channels as regulators of tissue regeneration. This study provides a preliminary framework for an in-depth investigation of the mechanistic role of ion channels and their potential involvement in regulating cellular proliferation and other processes essential to wound healing, appendage regeneration, and tissue repair.
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Affiliation(s)
- Brandon M Franklin
- Department of Biology, University of Kentucky, Lexington, KY 40506, United States
| | - S Randal Voss
- Department of Biology, University of Kentucky, Lexington, KY 40506, United States
| | - Jeffrey L Osborn
- Department of Biology, University of Kentucky, Lexington, KY 40506, United States.
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11
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Levin M, Pezzulo G, Finkelstein JM. Endogenous Bioelectric Signaling Networks: Exploiting Voltage Gradients for Control of Growth and Form. Annu Rev Biomed Eng 2017; 19:353-387. [PMID: 28633567 PMCID: PMC10478168 DOI: 10.1146/annurev-bioeng-071114-040647] [Citation(s) in RCA: 143] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Living systems exhibit remarkable abilities to self-assemble, regenerate, and remodel complex shapes. How cellular networks construct and repair specific anatomical outcomes is an open question at the heart of the next-generation science of bioengineering. Developmental bioelectricity is an exciting emerging discipline that exploits endogenous bioelectric signaling among many cell types to regulate pattern formation. We provide a brief overview of this field, review recent data in which bioelectricity is used to control patterning in a range of model systems, and describe the molecular tools being used to probe the role of bioelectrics in the dynamic control of complex anatomy. We suggest that quantitative strategies recently developed to infer semantic content and information processing from ionic activity in the brain might provide important clues to cracking the bioelectric code. Gaining control of the mechanisms by which large-scale shape is regulated in vivo will drive transformative advances in bioengineering, regenerative medicine, and synthetic morphology, and could be used to therapeutically address birth defects, traumatic injury, and cancer.
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Affiliation(s)
- Michael Levin
- Biology Department, Tufts University, Medford, Massachusetts 02155-4243;
- Allen Discovery Center, Tufts University, Medford, Massachusetts 02155;
| | - Giovanni Pezzulo
- Institute of Cognitive Sciences and Technologies, National Research Council, Rome 00185, Italy;
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12
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Sullivan KG, Levin M. Neurotransmitter signaling pathways required for normal development in Xenopus laevis embryos: a pharmacological survey screen. J Anat 2016; 229:483-502. [PMID: 27060969 DOI: 10.1111/joa.12467] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/17/2016] [Indexed: 01/08/2023] Open
Abstract
Neurotransmitters are not only involved in brain function but are also important signaling molecules for many diverse cell types. Neurotransmitters are widely conserved, from evolutionarily ancient organisms lacking nervous systems through man. Here, results are reported from a loss- and gain-of-function survey, using pharmacological modulators of several neurotransmitter pathways to examine possible roles for these pathways in normal embryogenesis. Applying reagents targeting the glutamatergic, adrenergic and dopaminergic pathways to embryos of Xenopus laevis from gastrulation to organogenesis stages, we observed and quantified numerous malformations, including craniofacial defects, hyperpigmentation, muscle mispatterning and miscoiling of the gut. These data implicate several key neurotransmitters in new embryonic patterning roles, reveal novel earlier stages for processes involved in eye development, suggest new targets for subsequent molecular-genetic investigation, and highlight the necessity for in-depth toxicology studies of psychoactive compounds to which human embryos might be exposed during pregnancy.
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Affiliation(s)
- Kelly G Sullivan
- Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, MA, USA
| | - Michael Levin
- Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, MA, USA
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13
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Kryukova NA, Chertkova EA, Semenova AD, Glazachev YI, Slepneva IA, Glupov VV. VENOM FROM THE ECTOPARASITIC WASP Habrobracon hebetor ACTIVATES CALCIUM-DEPENDENT DEGRADATION OF Galleria mellonella LARVAL HEMOCYTES. ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY 2015; 90:117-130. [PMID: 26089096 DOI: 10.1002/arch.21247] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Ectoparasitoids inject venom into hemolymph during oviposition. We determined the influence of envenomation by the parasitoid, Habrobracon hebetor, on the hemocytes of its larval host, Galleria mellonella. An increase in both intracellular Са(2+) content and phospholipase C activity of the host hemocytes was recorded during 2 days following envenomation by the parasitoid. The decreased hemocyte viability was detected 1, 2, and 24 h after the envenomation. Injecting of the crude venom (final protein concentration 3 μg/ml) into the G. mellonella larvae led to the reduced hemocyte adhesion. The larval envenomation caused a decrease in transmembrane potential of the hemocytes. These findings document the suppression of hemocytic immune effectors in the parasitized host larvae.
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Affiliation(s)
- Natalia A Kryukova
- Institute of Systematics and Ecology of Animals, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Ekaterina A Chertkova
- Institute of Systematics and Ecology of Animals, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Alexandra D Semenova
- Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Yuri I Glazachev
- Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Irina A Slepneva
- Voevodsky Institute of Chemical Kinetics and Combustion, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Victor V Glupov
- Institute of Systematics and Ecology of Animals, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
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14
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Levin M. Molecular bioelectricity: how endogenous voltage potentials control cell behavior and instruct pattern regulation in vivo. Mol Biol Cell 2015; 25:3835-50. [PMID: 25425556 PMCID: PMC4244194 DOI: 10.1091/mbc.e13-12-0708] [Citation(s) in RCA: 221] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
In addition to biochemical gradients and transcriptional networks, cell behavior is regulated by endogenous bioelectrical cues originating in the activity of ion channels and pumps, operating in a wide variety of cell types. Instructive signals mediated by changes in resting potential control proliferation, differentiation, cell shape, and apoptosis of stem, progenitor, and somatic cells. Of importance, however, cells are regulated not only by their own Vmem but also by the Vmem of their neighbors, forming networks via electrical synapses known as gap junctions. Spatiotemporal changes in Vmem distribution among nonneural somatic tissues regulate pattern formation and serve as signals that trigger limb regeneration, induce eye formation, set polarity of whole-body anatomical axes, and orchestrate craniofacial patterning. New tools for tracking and functionally altering Vmem gradients in vivo have identified novel roles for bioelectrical signaling and revealed the molecular pathways by which Vmem changes are transduced into cascades of downstream gene expression. Because channels and gap junctions are gated posttranslationally, bioelectrical networks have their own characteristic dynamics that do not reduce to molecular profiling of channel expression (although they couple functionally to transcriptional networks). The recent data provide an exciting opportunity to crack the bioelectric code, and learn to program cellular activity at the level of organs, not only cell types. The understanding of how patterning information is encoded in bioelectrical networks, which may require concepts from computational neuroscience, will have transformative implications for embryogenesis, regeneration, cancer, and synthetic bioengineering.
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Affiliation(s)
- Michael Levin
- Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, MA 02155-4243
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15
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Chernet BT, Levin M. Transmembrane voltage potential of somatic cells controls oncogene-mediated tumorigenesis at long-range. Oncotarget 2015; 5:3287-306. [PMID: 24830454 PMCID: PMC4102810 DOI: 10.18632/oncotarget.1935] [Citation(s) in RCA: 83] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The microenvironment is increasingly recognized as a crucial aspect of cancer. In contrast and complement to the field's focus on biochemical factors and extracellular matrix, we characterize a novel aspect of host:tumor interaction - endogenous bioelectric signals among non-excitable somatic cells. Extending prior work focused on the bioelectric state of cancer cells themselves, we show for the first time that the resting potentials of distant cells are critical for oncogene-dependent tumorigenesis. In the Xenopus laevis tadpole model, we used human oncogenes such as mutant KRAS to drive formation of tumor-like structures that exhibited overproliferation, increased nuclear size, hypoxia, acidity, and leukocyte attraction. Remarkably, misexpression of hyperpolarizing ion channels at distant sites within the tadpole significantly reduced the incidence of these tumors. The suppression of tumorigenesis could also be achieved by hyperpolarization using native CLIC1 chloride channels, suggesting a treatment modality not requiring gene therapy. Using a dominant negative approach, we implicate HDAC1 as the mechanism by which resting potential changes affect downstream cell behaviors. Based on published data on the voltage-mediated changes of butyrate flux through the SLC5A8 transporter, we present a model linking resting potentials of host cells to the ability of oncogenes to initiate tumorigenesis. Antibiotic data suggest that the relevant butyrate is generated by a native bacterial species, identifying a novel link between the microbiome and cancer that is mediated by alterations in bioelectric signaling.
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Affiliation(s)
- Brook T Chernet
- Center for Regenerative and Developmental Biology and Department of Biology Tufts University 200 Boston Avenue,Suite 4600 Medford, MA 02155 U.S.A
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16
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Charalambous A, Koyioni M, Antoniades I, Pegeioti D, Eleftheriou I, Michaelidou SS, Amelichev SA, Konstantinova LS, Rakitin OA, Koutentis PA, Skourides PA. 1,2,3-Dithiazoles – new reversible melanin synthesis inhibitors: a chemical genomics study. MEDCHEMCOMM 2015. [DOI: 10.1039/c5md00052a] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
1,2,3-Dithiazolimines show potent and reversible inhibition of melanin synthesis in Xenopus laevis embryos.
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Affiliation(s)
| | - Maria Koyioni
- Department of Chemistry
- University of Cyprus
- 1678 Nicosia
- Cyprus
| | | | | | | | | | | | | | - Oleg A. Rakitin
- N.D. Zelinsky Institute of Organic Chemistry
- RAS
- Moscow 119991
- Russia
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17
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Burnette M, Brito-Robinson T, Li J, Zartman J. An inverse small molecule screen to design a chemically defined medium supporting long-term growth of Drosophila cell lines. MOLECULAR BIOSYSTEMS 2014; 10:2713-23. [PMID: 25096480 PMCID: PMC4890965 DOI: 10.1039/c4mb00155a] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Drosophila cell culture is used as a model system with multiple applications including the identification of new therapeutic targets in screens, the study of conserved signal transduction pathway mechanisms, and as an expression system for recombinant proteins. However, in vitro methods for Drosophila cell and organ cultures are relatively undeveloped. To characterize the minimal requirements for long-term maintenance of Drosophila cell lines, we developed an inverse screening strategy to identify small molecules and synergies stimulating proliferation in a chemically defined medium. In this chemical-genetics approach, a compound-protein interaction database is used to systematically score genetic targets on a screen-wide scale to extract further information about cell growth. In the pilot screen, we focused on two well-characterized cell lines, Clone 8 (Cl.8) and Schneider 2 (S2). Validated factors were investigated for their ability to maintain cell growth over multiple passages in the chemically defined medium (CDM). The polyamine spermidine proved to be the critical component that enables the CDM to support long-term maintenance of Cl.8 cells. Spermidine supplementation upregulates DNA synthesis for Cl.8 and S2 cells and increases MAPK signaling for Cl.8 cells. The CDM also supports the long-term growth of Kc167 cells. Our target scoring approach validated the importance of polyamines, with enrichment for multiple polyamine ontologies found for both cell lines. Future iterations of the screen will enable the identification of compound combinations optimized for specific applications-maintenance and generation of new cell lines or the production and purification of recombinant proteins-thus increasing the versatility of Drosophila cell culture as both a genetic and biochemical model system. Our cumulative target scoring approach improves on traditional chemical-genetics methods and is extensible to biological processes in other species.
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Affiliation(s)
- M Burnette
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA.
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18
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Mustard J, Levin M. Bioelectrical Mechanisms for Programming Growth and Form: Taming Physiological Networks for Soft Body Robotics. Soft Robot 2014. [DOI: 10.1089/soro.2014.0011] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Affiliation(s)
- Jessica Mustard
- Department of Biology and Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts
| | - Michael Levin
- Department of Biology and Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts
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Cerqueira DM, Tran U, Romaker D, Abreu JG, Wessely O. Sterol carrier protein 2 regulates proximal tubule size in the Xenopus pronephric kidney by modulating lipid rafts. Dev Biol 2014; 394:54-64. [PMID: 25127994 DOI: 10.1016/j.ydbio.2014.07.025] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2013] [Revised: 05/29/2014] [Accepted: 07/30/2014] [Indexed: 11/29/2022]
Abstract
The kidney is a homeostatic organ required for waste excretion and reabsorption of water, salts and other macromolecules. To this end, a complex series of developmental steps ensures the formation of a correctly patterned and properly proportioned organ. While previous studies have mainly focused on the individual signaling pathways, the formation of higher order receptor complexes in lipid rafts is an equally important aspect. These membrane platforms are characterized by differences in local lipid and protein compositions. Indeed, the cells in the Xenopus pronephric kidney were positive for the lipid raft markers ganglioside GM1 and Caveolin-1. To specifically interfere with lipid raft function in vivo, we focused on the Sterol Carrier Protein 2 (scp2), a multifunctional protein that is an important player in remodeling lipid raft composition. In Xenopus, scp2 mRNA was strongly expressed in differentiated epithelial structures of the pronephric kidney. Knockdown of scp2 did not interfere with the patterning of the kidney along its proximo-distal axis, but dramatically decreased the size of the kidney, in particular the proximal tubules. This phenotype was accompanied by a reduction of lipid rafts, but was independent of the peroxisomal or transcriptional activities of scp2. Finally, disrupting lipid micro-domains by inhibiting cholesterol synthesis using Mevinolin phenocopied the defects seen in scp2 morphants. Together these data underscore the importance for localized signaling platforms in the proper formation of the Xenopus kidney.
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Affiliation(s)
- Débora M Cerqueira
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA; Universidade Federal do Rio de Janeiro, Instituto de Ciências Biomédicas-CCS, Av. Carlos Chagas Filho, 373 bloco F2 sala 15, Rio de Janeiro 21949-590, Brazil
| | - Uyen Tran
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA
| | - Daniel Romaker
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA
| | - José G Abreu
- Universidade Federal do Rio de Janeiro, Instituto de Ciências Biomédicas-CCS, Av. Carlos Chagas Filho, 373 bloco F2 sala 15, Rio de Janeiro 21949-590, Brazil
| | - Oliver Wessely
- Cleveland Clinic Foundation, Lerner Research Institute, Department Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10 Cleveland, OH 44195, USA.
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20
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Tahmasbi Rad A, Ali N, Kotturi HSR, Yazdimamaghani M, Smay J, Vashaee D, Tayebi L. Conducting scaffolds for liver tissue engineering. J Biomed Mater Res A 2014; 102:4169-81. [DOI: 10.1002/jbm.a.35080] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2013] [Revised: 12/13/2013] [Accepted: 01/15/2014] [Indexed: 12/24/2022]
Affiliation(s)
- Armin Tahmasbi Rad
- School of Materials Science and Engineering; Helmerich Advanced Technology Research Center; Oklahoma State University; Tulsa Oklahoma 74105
| | - Naushad Ali
- Department of Internal Medicine; Section of Digestive Diseases and Nutrition, University of Oklahoma Health Sciences Center; 975 NE 10th Street Oklahoma City Oklahoma 73104
| | - Hari Shankar R. Kotturi
- Department of Biology; University of Central Oklahoma; 100 North University Drive; Edmond Oklahoma 73034
| | | | - Jim Smay
- School of Chemical Engineering; Oklahoma State University; Stillwater Oklahoma 74078
| | - Daryoosh Vashaee
- School of Electrical and Computer Engineering; Helmerich Advanced Technology Research Center; Oklahoma State University; Tulsa Oklahoma 74105
| | - Lobat Tayebi
- School of Materials Science and Engineering; Helmerich Advanced Technology Research Center; Oklahoma State University; Tulsa Oklahoma 74105
- School of Chemical Engineering; Oklahoma State University; Stillwater Oklahoma 74078
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21
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VANDENBERG LAURAN, BLACKISTON DOUGLASJ, REA ADAMC, DORE TIMOTHYM, LEVIN MICHAEL. Left-right patterning in Xenopus conjoined twin embryos requires serotonin signaling and gap junctions. THE INTERNATIONAL JOURNAL OF DEVELOPMENTAL BIOLOGY 2014; 58:799-809. [PMID: 25896280 PMCID: PMC10471180 DOI: 10.1387/ijdb.140215ml] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
A number of processes operating during the first cell cleavages enable the left-right (LR) axis to be consistently oriented during Xenopus laevis development. Prior work showed that secondary organizers induced in frog embryos after cleavage stages (i.e. conjoined twins arising from ectopic induced primary axes) correctly pattern their own LR axis only when a primary (early) organizer is also present. This instructive effect confirms the unique LR patterning functions that occur during early embryogenesis, but leaves open the question: which mechanisms that operate during early stages are also involved in the orientation of later-induced organizers? We sought to distinguish the two phases of LR patterning in secondary organizers (LR patterning of the primary twin and the later transfer of this information to the secondary twin) by perturbing only the latter process. Here, we used reagents that do not affect primary LR patterning at the time secondary organizers form to inhibit each of 4 mechanisms in the induced twin. Using pharmacological, molecular-genetic, and photo-chemical tools, we show that serotonergic and gap-junctional signaling, but not proton or potassium flows, are required for the secondary organizer to appropriately pattern its LR axis in a multicellular context. We also show that consistently-asymmetric gene expression begins prior to ciliary flow. Together, our data highlight the importance of physiological signaling in the propagation of cleavage-derived LR orientation to multicellular cell fields.
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Affiliation(s)
- LAURA N. VANDENBERG
- Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, MA, USA
- Department of Public Health, Division of Environmental Health Sciences, University of Massachusetts – Amherst, Amherst, MA, USA
| | - DOUGLAS J. BLACKISTON
- Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, MA, USA
| | - ADAM C. REA
- Department of Chemistry, University of Georgia, Athens, GA, USA and
| | - TIMOTHY M. DORE
- Department of Chemistry, University of Georgia, Athens, GA, USA and
- New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - MICHAEL LEVIN
- Biology Department, Center for Regenerative and Developmental Biology, Tufts University, Medford, MA, USA
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Vandenberg LN, Lemire JM, Levin M. It's never too early to get it Right: A conserved role for the cytoskeleton in left-right asymmetry. Commun Integr Biol 2013; 6:e27155. [PMID: 24505508 PMCID: PMC3912007 DOI: 10.4161/cib.27155] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 11/08/2013] [Accepted: 11/11/2013] [Indexed: 01/08/2023] Open
Abstract
For centuries, scientists and physicians have been captivated by the consistent left-right (LR) asymmetry of the heart, viscera, and brain. A recent study implicated tubulin proteins in establishing laterality in several experimental models, including asymmetric chemosensory receptor expression in C. elegans neurons, polarization of HL-60 human neutrophil-like cells in culture, and asymmetric organ placement in Xenopus. The same mutations that randomized asymmetry in these diverse systems also affect chirality in Arabidopsis, revealing a remarkable conservation of symmetry-breaking mechanisms among kingdoms. In Xenopus, tubulin mutants only affected LR patterning very early, suggesting that this axis is established shortly after fertilization. This addendum summarizes and extends the knowledge of the cytoskeleton's role in the patterning of the LR axis. Results from many species suggest a conserved role for the cytoskeleton as the initiator of asymmetry, and indicate that symmetry is first broken during early embryogenesis by an intracellular process.
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Affiliation(s)
- Laura N Vandenberg
- Biology Department; Center for Regenerative and Developmental Biology; Tufts University; Medford, MA USA ; Current affiliation: Department of Public Health; Division of Environmental Health Sciences; University of Massachusetts, Amherst; Amherst, MA USA
| | - Joan M Lemire
- Biology Department; Center for Regenerative and Developmental Biology; Tufts University; Medford, MA USA
| | - Michael Levin
- Biology Department; Center for Regenerative and Developmental Biology; Tufts University; Medford, MA USA
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23
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Levin M. Reprogramming cells and tissue patterning via bioelectrical pathways: molecular mechanisms and biomedical opportunities. WILEY INTERDISCIPLINARY REVIEWS. SYSTEMS BIOLOGY AND MEDICINE 2013; 5:657-76. [PMID: 23897652 PMCID: PMC3841289 DOI: 10.1002/wsbm.1236] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/02/2013] [Revised: 05/16/2013] [Accepted: 06/21/2013] [Indexed: 12/17/2022]
Abstract
Transformative impact in regenerative medicine requires more than the reprogramming of individual cells: advances in repair strategies for birth defects or injuries, tumor normalization, and the construction of bioengineered organs and tissues all require the ability to control large-scale anatomical shape. Much recent work has focused on the transcriptional and biochemical regulation of cell behavior and morphogenesis. However, exciting new data reveal that bioelectrical properties of cells and their microenvironment exert a profound influence on cell differentiation, proliferation, and migration. Ion channels and pumps expressed in all cells, not just excitable nerve and muscle, establish resting potentials that vary across tissues and change with significant developmental events. Most importantly, the spatiotemporal gradients of these endogenous transmembrane voltage potentials (Vmem ) serve as instructive patterning cues for large-scale anatomy, providing organ identity, positional information, and prepattern template cues for morphogenesis. New genetic and pharmacological techniques for molecular modulation of bioelectric gradients in vivo have revealed the ability to initiate complex organogenesis, change tissue identity, and trigger regeneration of whole vertebrate appendages. A large segment of the spatial information processing that orchestrates individual cells' programs toward the anatomical needs of the host organism is electrical; this blurs the line between memory and decision-making in neural networks and morphogenesis in nonneural tissues. Advances in cracking this bioelectric code will enable the rational reprogramming of shape in whole tissues and organs, revolutionizing regenerative medicine, developmental biology, and synthetic bioengineering.
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Affiliation(s)
- Michael Levin
- Tufts University, Department of Biology and Tufts Center for Regenerative and Developmental Biology, 200 Boston Ave., Suite 4600, Medford, MA 02155
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24
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Adams DS, Levin M. Endogenous voltage gradients as mediators of cell-cell communication: strategies for investigating bioelectrical signals during pattern formation. Cell Tissue Res 2013; 352:95-122. [PMID: 22350846 PMCID: PMC3869965 DOI: 10.1007/s00441-012-1329-4] [Citation(s) in RCA: 116] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2011] [Accepted: 01/12/2012] [Indexed: 01/07/2023]
Abstract
Alongside the well-known chemical modes of cell-cell communication, we find an important and powerful system of bioelectrical signaling: changes in the resting voltage potential (Vmem) of the plasma membrane driven by ion channels, pumps and gap junctions. Slow Vmem changes in all cells serve as a highly conserved, information-bearing pathway that regulates cell proliferation, migration and differentiation. In embryonic and regenerative pattern formation and in the disorganization of neoplasia, bioelectrical cues serve as mediators of large-scale anatomical polarity, organ identity and positional information. Recent developments have resulted in tools that enable a high-resolution analysis of these biophysical signals and their linkage with upstream and downstream canonical genetic pathways. Here, we provide an overview for the study of bioelectric signaling, focusing on state-of-the-art approaches that use molecular physiology and developmental genetics to probe the roles of bioelectric events functionally. We highlight the logic, strategies and well-developed technologies that any group of researchers can employ to identify and dissect ionic signaling components in their own work and thus to help crack the bioelectric code. The dissection of bioelectric events as instructive signals enabling the orchestration of cell behaviors into large-scale coherent patterning programs will enrich on-going work in diverse areas of biology, as biophysical factors become incorporated into our systems-level understanding of cell interactions.
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Affiliation(s)
- Dany S Adams
- Department of Biology, and Center for Regenerative and Developmental Biology, Tufts University, 200 Boston Ave, Medford, MA 02155, USA
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25
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Zhang B, Romaker D, Ferrell N, Wessely O. Regulation of G-protein signaling via Gnas is required to regulate proximal tubular growth in the Xenopus pronephros. Dev Biol 2013; 376:31-42. [PMID: 23352791 DOI: 10.1016/j.ydbio.2013.01.017] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2012] [Revised: 01/10/2013] [Accepted: 01/14/2013] [Indexed: 11/17/2022]
Abstract
In the kidney, proximal tubules are very important for the reabsorption of water, ions and organic solutes from the primary urine. They are composed of highly specialized epithelial cells that are characterized by an elaborate apical brush border to increase transport efficiency. Using the pronephric kidney of Xenopus laevis we discovered that the G-protein modulator cholera toxin resulted in a dramatic reduction of the proximal tubular size. This phenotype was accompanied by changes in the cytoarchitecture characterized by ectopic expression of the distal tubular marker 4A6 and an impairment of yolk platelet degradation. In addition, cholera toxin caused edema formation. However, this phenotype was not due to kidney defects, but rather due to impaired vasculature development. Based on experiments with antisense morpholino oligomers as well as pharmacological agonists and antagonists, we could show that the complex phenotype of cholera toxin in the pronephric kidney was caused by the hyperactivation of a single G-protein alpha subunit, Gnas. This-in turn-caused elevated cAMP levels, triggered a Rapgef4-dependent signaling cassette and perturbed exo- and endocytosis. This perturbation of the secretory pathway by Ctx was not only observed in Xenopus embryos. Also, in a human proximal tubular cell line, cholera toxin or a Rapgef4-specific agonist increased uptake and decreased secretion of FITC-labeled Albumin. Based on these data we propose that the Gnas/cAMP/Rapgef4 pathway regulates the signals inducing the proliferation of proximal tubules to acquire their final organ size.
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Affiliation(s)
- Bo Zhang
- Cleveland Clinic Foundation, Lerner Research Institute, Department of Cellular and Molecular Medicine, 9500 Euclid Avenue/NC10, Cleveland, OH 44195, USA
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26
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Lobikin M, Chernet B, Lobo D, Levin M. Resting potential, oncogene-induced tumorigenesis, and metastasis: the bioelectric basis of cancer in vivo. Phys Biol 2012. [PMID: 23196890 DOI: 10.1088/1478-3975/9/6/065002] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Cancer may result from localized failure of instructive cues that normally orchestrate cell behaviors toward the patterning needs of the organism. Steady-state gradients of transmembrane voltage (V(mem)) in non-neural cells are instructive, epigenetic signals that regulate pattern formation during embryogenesis and morphostatic repair. Here, we review molecular data on the role of bioelectric cues in cancer and present new findings in the Xenopus laevis model on how the microenvironment's biophysical properties contribute to cancer in vivo. First, we investigated the melanoma-like phenotype arising from serotonergic signaling by 'instructor' cells-a cell population that is able to induce a metastatic phenotype in normal melanocytes. We show that when these instructor cells are depolarized, blood vessel patterning is disrupted in addition to the metastatic phenotype induced in melanocytes. Surprisingly, very few instructor cells need to be depolarized for the hyperpigmentation phenotype to occur; we present a model of antagonistic signaling by serotonin receptors that explains the unusual all-or-none nature of this effect. In addition to the body-wide depolarization-induced metastatic phenotype, we investigated the bioelectrical properties of tumor-like structures induced by canonical oncogenes and cancer-causing compounds. Exposure to carcinogen 4-nitroquinoline 1-oxide (4NQO) induces localized tumors, but has a broad (and variable) effect on the bioelectric properties of the whole body. Tumors induced by oncogenes show aberrantly high sodium content, representing a non-invasive diagnostic modality. Importantly, depolarized transmembrane potential is not only a marker of cancer but is functionally instructive: susceptibility to oncogene-induced tumorigenesis is significantly reduced by forced prior expression of hyperpolarizing ion channels. Importantly, the same effect can be achieved by pharmacological manipulation of endogenous chloride channels, suggesting a strategy for cancer suppression that does not require gene therapy. Together, these data extend our understanding of the recently demonstrated role of transmembrane potential in tumor formation and metastatic cell behavior. V(mem) is an important non-genetic biophysical aspect of the microenvironment that regulates the balance between normally patterned growth and carcinogenesis.
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Affiliation(s)
- Maria Lobikin
- Biology Department and Tufts Center for Regenerative and Developmental Biology, Tufts University, 200 Boston Avenue, Medford, MA 02155, USA
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27
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Vandenberg LN, Adams DS, Levin M. Normalized shape and location of perturbed craniofacial structures in the Xenopus tadpole reveal an innate ability to achieve correct morphology. Dev Dyn 2012; 241:863-78. [PMID: 22411736 DOI: 10.1002/dvdy.23770] [Citation(s) in RCA: 75] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/27/2012] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Embryonic development can often adjust its morphogenetic processes to counteract external perturbation. The existence of self-monitoring responses during pattern formation is of considerable importance to the biomedicine of birth defects, but has not been quantitatively addressed. To understand the computational capabilities of biological tissues in a molecularly tractable model system, we induced craniofacial defects in Xenopus embryos, then tracked tadpoles with craniofacial deformities and used geometric morphometric techniques to characterize changes in the shape and position of the craniofacial structures. RESULTS Canonical variate analysis revealed that the shapes and relative positions of perturbed jaws and branchial arches were corrected during the first few months of tadpole development. Analysis of the relative movements of the anterior-most structures indicates that misplaced structures move along the anterior-posterior and left-right axes in ways that are significantly different from their normal movements. CONCLUSIONS Our data suggest a model in which craniofacial structures use a measuring mechanism to assess and adjust their location relative to other local organs. Understanding the correction mechanisms at work in this system could lead to the better understanding of the adaptive decision-making capabilities of living tissues and suggest new approaches to correct birth defects in humans.
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Affiliation(s)
- Laura N Vandenberg
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University, Medford, MA 02155, USA
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28
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Wheeler GN, Liu KJ. Xenopus: An ideal system for chemical genetics. Genesis 2012; 50:207-18. [DOI: 10.1002/dvg.22009] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2011] [Revised: 12/21/2011] [Accepted: 12/23/2011] [Indexed: 02/05/2023]
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29
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Levin M. Molecular bioelectricity in developmental biology: new tools and recent discoveries: control of cell behavior and pattern formation by transmembrane potential gradients. Bioessays 2012; 34:205-17. [PMID: 22237730 DOI: 10.1002/bies.201100136] [Citation(s) in RCA: 171] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Significant progress in the molecular investigation of endogenous bioelectric signals during pattern formation in growing tissues has been enabled by recently developed techniques. Ion flows and voltage gradients produced by ion channels and pumps are key regulators of cell proliferation, migration, and differentiation. Now, instructive roles for bioelectrical gradients in embryogenesis, regeneration, and neoplasm are being revealed through the use of fluorescent voltage reporters and functional experiments using well-characterized channel mutants. Transmembrane voltage gradients (V(mem) ) determine anatomical polarity and function as master regulators during appendage regeneration and embryonic left-right patterning. A state-of-the-art recent study reveals that they can also serve as prepatterns for gene expression domains during craniofacial patterning. Continued development of novel tools and better ways to think about physical controls of cell-cell interactions will lead to mastery of the morphogenetic information stored in physiological networks. This will enable fundamental advances in basic understanding of growth and form, as well as transformative biomedical applications in regenerative medicine.
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Affiliation(s)
- Michael Levin
- Center for Regenerative and Developmental Biology, Department of Biology, Tufts University, Medford, MA, USA.
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30
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Levin M, Stevenson CG. Regulation of cell behavior and tissue patterning by bioelectrical signals: challenges and opportunities for biomedical engineering. Annu Rev Biomed Eng 2012; 14:295-323. [PMID: 22809139 PMCID: PMC10472538 DOI: 10.1146/annurev-bioeng-071811-150114] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Achieving control over cell behavior and pattern formation requires molecular-level understanding of regulatory mechanisms. Alongside transcriptional networks and biochemical gradients, there functions an important system of cellular communication and control: transmembrane voltage gradients (V(mem)). Bioelectrical signals encoded in spatiotemporal changes of V(mem) control cell proliferation, migration, and differentiation. Moreover, endogenous bioelectrical gradients serve as instructive cues mediating anatomical polarity and other organ-level aspects of morphogenesis. In the past decade, significant advances in molecular physiology have enabled the development of new genetic and biophysical tools for the investigation and functional manipulation of bioelectric cues. Recent data implicate V(mem) as a crucial epigenetic regulator of patterning events in embryogenesis, regeneration, and cancer. We review new conceptual and methodological developments in this fascinating field. Bioelectricity offers a novel way of quantitatively understanding regulation of growth and form in vivo, and it reveals tractable, powerful control points that will enable truly transformative applications in bioengineering, regenerative medicine, and synthetic biology.
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Affiliation(s)
- Michael Levin
- Department of Biology, Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts 02155, USA.
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31
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A chemical genetics approach reveals H,K-ATPase-mediated membrane voltage is required for planarian head regeneration. ACTA ACUST UNITED AC 2011; 18:77-89. [PMID: 21276941 DOI: 10.1016/j.chembiol.2010.11.012] [Citation(s) in RCA: 144] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Revised: 10/22/2010] [Accepted: 11/09/2010] [Indexed: 12/12/2022]
Abstract
Biophysical signaling is required for both embryonic polarity and regenerative outgrowth. Exploiting endogenous ion transport for regenerative therapies will require direct regulation of membrane voltage. Here, we develop a pharmacological method to target ion transporters, uncovering a role for membrane voltage as a key regulator of anterior polarity in regenerating planaria. Utilizing the highly specific inhibitor, SCH-28080, our data reveal that H(+),K(+)-ATPase-mediated membrane depolarization is essential for anterior gene expression and brain induction. H(+),K(+)-ATPase-independent manipulation of membrane potential with ivermectin confirms that depolarization drives head formation, even at posterior-facing wounds. Using this chemical genetics approach, we demonstrate that membrane voltage controls head-versus-tail identity during planarian regeneration. Our data suggest well-characterized drugs (already approved for human use) might be exploited to control adult stem cell-driven pattern formation during the regeneration of complex structures.
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32
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Blackiston D, Adams DS, Lemire JM, Lobikin M, Levin M. Transmembrane potential of GlyCl-expressing instructor cells induces a neoplastic-like conversion of melanocytes via a serotonergic pathway. Dis Model Mech 2011; 4:67-85. [PMID: 20959630 PMCID: PMC3008964 DOI: 10.1242/dmm.005561] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2010] [Accepted: 08/23/2010] [Indexed: 12/14/2022] Open
Abstract
Understanding the mechanisms that coordinate stem cell behavior within the host is a high priority for developmental biology, regenerative medicine and oncology. Endogenous ion currents and voltage gradients function alongside biochemical cues during pattern formation and tumor suppression, but it is not known whether bioelectrical signals are involved in the control of stem cell progeny in vivo. We studied Xenopus laevis neural crest, an embryonic stem cell population that gives rise to many cell types, including melanocytes, and contributes to the morphogenesis of the face, heart and other complex structures. To investigate how depolarization of transmembrane potential of cells in the neural crest's environment influences its function in vivo, we manipulated the activity of the native glycine receptor chloride channel (GlyCl). Molecular-genetic depolarization of a sparse, widely distributed set of GlyCl-expressing cells non-cell-autonomously induces a neoplastic-like phenotype in melanocytes: they overproliferate, acquire an arborized cell shape and migrate inappropriately, colonizing numerous tissues in a metalloprotease-dependent fashion. A similar effect was observed in human melanocytes in culture. Depolarization of GlyCl-expressing cells induces these drastic changes in melanocyte behavior via a serotonin-transporter-dependent increase of extracellular serotonin (5-HT). These data reveal GlyCl as a molecular marker of a sparse and heretofore unknown cell population with the ability to specifically instruct neural crest derivatives, suggest transmembrane potential as a tractable signaling modality by which somatic cells can control stem cell behavior at considerable distance, identify a new biophysical aspect of the environment that confers a neoplastic-like phenotype upon stem cell progeny, reveal a pre-neural role for serotonin and its transporter, and suggest a novel strategy for manipulating stem cell behavior.
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Affiliation(s)
- Douglas Blackiston
- Center for Regenerative and Developmental Biology, and Biology Department, 200 Boston Avenue, Suite 4600, Tufts University, Medford, MA 02155, USA
- Department of Regenerative and Developmental Biology, Forsyth Institute, Boston, MA 02115, USA
| | - Dany S. Adams
- Center for Regenerative and Developmental Biology, and Biology Department, 200 Boston Avenue, Suite 4600, Tufts University, Medford, MA 02155, USA
| | - Joan M. Lemire
- Center for Regenerative and Developmental Biology, and Biology Department, 200 Boston Avenue, Suite 4600, Tufts University, Medford, MA 02155, USA
| | - Maria Lobikin
- Center for Regenerative and Developmental Biology, and Biology Department, 200 Boston Avenue, Suite 4600, Tufts University, Medford, MA 02155, USA
| | - Michael Levin
- Center for Regenerative and Developmental Biology, and Biology Department, 200 Boston Avenue, Suite 4600, Tufts University, Medford, MA 02155, USA
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33
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Vandenberg LN, Levin M. Far from solved: a perspective on what we know about early mechanisms of left-right asymmetry. Dev Dyn 2010; 239:3131-46. [PMID: 21031419 PMCID: PMC10468760 DOI: 10.1002/dvdy.22450] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/31/2023] Open
Abstract
Consistent laterality is a crucial aspect of embryonic development, physiology, and behavior. While strides have been made in understanding unilaterally expressed genes and the asymmetries of organogenesis, early mechanisms are still poorly understood. One popular model centers on the structure and function of motile cilia and subsequent chiral extracellular fluid flow during gastrulation. Alternative models focus on intracellular roles of the cytoskeleton in driving asymmetries of physiological signals or asymmetric chromatid segregation, at much earlier stages. All three models trace the origin of asymmetry back to the chirality of cytoskeletal organizing centers, but significant controversy exists about how this intracellular chirality is amplified onto cell fields. Analysis of specific predictions of each model and crucial recent data on new mutants suggest that ciliary function may not be a broadly conserved, initiating event in left-right patterning. Many questions about embryonic left-right asymmetry remain open, offering fascinating avenues for further research in cell, developmental, and evolutionary biology.
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Affiliation(s)
- Laura N. Vandenberg
- Biology Department, and Tufts Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts
| | - Michael Levin
- Biology Department, and Tufts Center for Regenerative and Developmental Biology, Tufts University, Medford, Massachusetts
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34
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Aw S, Koster J, Pearson W, Nichols C, Shi NQ, Carneiro K, Levin M. The ATP-sensitive K(+)-channel (K(ATP)) controls early left-right patterning in Xenopus and chick embryos. Dev Biol 2010; 346:39-53. [PMID: 20643119 PMCID: PMC2937067 DOI: 10.1016/j.ydbio.2010.07.011] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Revised: 06/21/2010] [Accepted: 07/08/2010] [Indexed: 11/17/2022]
Abstract
Consistent left-right asymmetry requires specific ion currents. We characterize a novel laterality determinant in Xenopus laevis: the ATP-sensitive K(+)-channel (K(ATP)). Expression of specific dominant-negative mutants of the Xenopus Kir6.1 pore subunit of the K(ATP) channel induced randomization of asymmetric organ positioning. Spatio-temporally controlled loss-of-function experiments revealed that the K(ATP) channel functions asymmetrically in LR patterning during very early cleavage stages, and also symmetrically during the early blastula stages, a period when heretofore largely unknown events transmit LR patterning cues. Blocking K(ATP) channel activity randomizes the expression of the left-sided transcription of Nodal. Immunofluorescence analysis revealed that XKir6.1 is localized to basal membranes on the blastocoel roof and cell-cell junctions. A tight junction integrity assay showed that K(ATP) channels are required for proper tight junction function in early Xenopus embryos. We also present evidence that this function may be conserved to the chick, as inhibition of K(ATP) in the primitive streak of chick embryos randomizes the expression of the left-sided gene Sonic hedgehog. We propose a model by which K(ATP) channels control LR patterning via regulation of tight junctions.
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Affiliation(s)
- Sherry Aw
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University, Medford, MA 02155, USA
- Program in Biological and Biomedical Sciences, Harvard Medical School, Boston, Massachusetts 02115, USA
| | - Joseph Koster
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Wade Pearson
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Colin Nichols
- Department of Cell Biology and Physiology, and Center for the Investigation of Membrane Excitability Diseases, Washington University School of Medicine, St. Louis, MO 63110, USA
| | - Nian-Qing Shi
- Department of Medicine, University of Wisconsin, Madison, WI 53706, USA
| | - Katia Carneiro
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University, Medford, MA 02155, USA
| | - Michael Levin
- Center for Regenerative and Developmental Biology, and Biology Department, Tufts University, Medford, MA 02155, USA
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Beck CW, Izpisúa Belmonte JC, Christen B. Beyond early development: Xenopus as an emerging model for the study of regenerative mechanisms. Dev Dyn 2009; 238:1226-48. [PMID: 19280606 DOI: 10.1002/dvdy.21890] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
While Xenopus is a well-known model system for early vertebrate development, in recent years, it has also emerged as a leading model for regeneration research. As an anuran amphibian, Xenopus laevis can regenerate the larval tail and limb by means of the formation of a proliferating blastema, the lens of the eye by transdifferentiation of nearby tissues, and also exhibits a partial regeneration of the postmetamorphic froglet forelimb. With the availability of inducible transgenic techniques for Xenopus, recent experiments are beginning to address the functional role of genes in the process of regeneration. The use of soluble inhibitors has also been very successful in this model. Using the more traditional advantages of Xenopus, others are providing important lineage data on the origin of the cells that make up the tissues of the regenerate. Finally, transcriptome analyses of regenerating tissues seek to identify the genes and cellular processes that enable successful regeneration. Developmental Dynamics 238:1226-1248, 2009. (c) 2009 Wiley-Liss, Inc.
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Affiliation(s)
- Caroline W Beck
- Department of Zoology and Genetics Otago, University of Otago, New Zealand.
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Wheeler GN, Brändli AW. Simple vertebrate models for chemical genetics and drug discovery screens: Lessons from zebrafish andXenopus. Dev Dyn 2009; 238:1287-308. [DOI: 10.1002/dvdy.21967] [Citation(s) in RCA: 135] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
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Levin M. Bioelectric mechanisms in regeneration: Unique aspects and future perspectives. Semin Cell Dev Biol 2009; 20:543-56. [PMID: 19406249 DOI: 10.1016/j.semcdb.2009.04.013] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2009] [Accepted: 04/22/2009] [Indexed: 01/14/2023]
Abstract
Regenerative biology has focused largely on chemical factors and transcriptional networks. However, endogenous ion flows serve as key epigenetic regulators of cell behavior. Bioelectric signaling involves feedback loops, long-range communication, polarity, and information transfer over multiple size scales. Understanding the roles of endogenous voltage gradients, ion flows, and electric fields will contribute to the basic understanding of numerous morphogenetic processes and the means by which they can robustly restore pattern after perturbation. By learning to modulate the bioelectrical signals that control cell proliferation, migration, and differentiation, we gain a powerful set of new techniques with which to manipulate growth and patterning in biomedical contexts. This chapter reviews the unique properties of bioelectric signaling, surveys molecular strategies and reagents for its investigation, and discusses the opportunities made available for regenerative medicine.
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Affiliation(s)
- Michael Levin
- Tufts Center for Regenerative and Developmental Biology, Biology Department, Tufts University, Medford, MA 02155, USA.
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Tomlinson ML, Guan P, Morris RJ, Fidock MD, Rejzek M, Garcia-Morales C, Field RA, Wheeler GN. A chemical genomic approach identifies matrix metalloproteinases as playing an essential and specific role in Xenopus melanophore migration. ACTA ACUST UNITED AC 2009; 16:93-104. [PMID: 19171309 DOI: 10.1016/j.chembiol.2008.12.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2008] [Revised: 12/10/2008] [Accepted: 12/12/2008] [Indexed: 01/27/2023]
Abstract
To dissect the function of matrix metalloproteinases (MMPs) involved in cellular migration in vivo, we undertook both a forward chemical genomic screen and a functional approach to discover modulators of melanophore (pigment cell) migration in Xenopus laevis. We identified the 8-quinolinol derivative NSC 84093 as affecting melanophore migration in the developing embryo and have shown it to act as a MMP inhibitor. Potential targets of NSC 84093 investigated include MMP-14 and MMP-2. MMP-14 is expressed in migrating neural crest cells from which melanophores are derived. MMP-2 is expressed at the relevant time of development and in a pattern that suggests it contributes to melanophore migration. Morpholino-mediated knockdown of both MMPs demonstrates they play a key role in melanophore migration and partially phenocopy the effect of NSC 84093.
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Adams DS. A new tool for tissue engineers: ions as regulators of morphogenesis during development and regeneration. Tissue Eng Part A 2009; 14:1461-8. [PMID: 18601591 DOI: 10.1089/ten.tea.2008.0080] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Currently, most of the research on how to encourage stem cells to replace missing tissues focuses on biochemical control, such as signaling by growth factors. In addition to basic questions, such as how are stem cells induced to differentiate into particular cell types, also inherent in those studies are practical questions about how to identify, grow, induce, and safely deliver stems cells to the proper target. At the Forsyth Center for Regenerative and Developmental Biology, we are examining a different set of signals, specifically bioelectric signals (the regulated movement of ions across membranes), including membrane voltage, pH, and gap junction activity and gating. We have found strong evidence that bioelectrical signals function at many critical, early points, both up- and downstream of transcriptional regulation, during the processes of normal morphogenesis and adult stem cell-based regeneration. Examples described include gap-junction-dependent regulation of stem cell identity in a flatworm, proton-flux-regulated establishment of left-right asymmetry in vertebrates, and proton-flux-initiated regeneration of a complex structure that includes spinal cord--the tadpole tail--in frogs.
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Affiliation(s)
- Dany Spencer Adams
- Forsyth Center for Regenerative and Developmental Biology, The Forsyth Institute, and Department of Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115, USA.
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Abstract
Augmentation of regenerative ability is a powerful strategy being pursued for the biomedical management of traumatic injury, cancer, and degeneration. While considerable attention has been focused on embryonic stem cells, it is clear that much remains to be learned about how somatic cells may be controlled in the adult organism. The tadpole of the frog Xenopus laevis is a powerful model system within which fundamental mechanisms of regeneration are being addressed. The tadpole tail contains spinal cord, muscle, vasculature, and other terminally differentiated cell types and can fully regenerate itself through tissue renewal--a process that is most relevant to mammalian healing. Recent insight into this process has uncovered fascinating molecular details of how a complex appendage senses injury and rapidly repairs the necessary morphology. Here, we review what is known about the chemical and bioelectric signals underlying this process and draw analogies to evolutionarily conserved pathways in other patterning systems. The understanding of this process is not only of fundamental interest for the evolutionary and cell biology of morphogenesis, but will also generate information that is crucial to the development of regenerative therapies for human tissues and organs.
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Affiliation(s)
- A.-S. Tseng
- Center for Regenerative and Developmental Biology, Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine, 140 The Fenway, Boston, MA 02115, USA
| | - M. Levin
- Center for Regenerative and Developmental Biology, Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine, 140 The Fenway, Boston, MA 02115, USA
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Suppression of the endoplasmic reticulum calcium pump during zebrafish gastrulation affects left–right asymmetry of the heart and brain. Mech Dev 2008; 125:396-410. [DOI: 10.1016/j.mod.2008.02.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2006] [Revised: 02/11/2008] [Accepted: 02/13/2008] [Indexed: 12/11/2022]
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Morokuma J, Blackiston D, Levin M. KCNQ1 and KCNE1 K+ channel components are involved in early left-right patterning in Xenopus laevis embryos. Cell Physiol Biochem 2008; 21:357-72. [PMID: 18453744 PMCID: PMC3632048 DOI: 10.1159/000129628] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/03/2008] [Indexed: 01/12/2023] Open
Abstract
Several ion transporters have been implicated in left-right (LR) patterning. Here, we characterize a new component of the early bioelectrical circuit: the potassium channel KCNQ1 and its accessory subunit KCNE1. Having cloned the native Xenopus versions of both genes, we show that both are asymmetrically localized as maternal proteins during the first few cleavages of frog embryo development in a process dependent on microtubule and actin organization. Molecular loss-of-function using dominant negative constructs demonstrates that both gene products are required for normal LR asymmetry. We propose a model whereby these channels provide an exit path for K(+) ions brought in by the H(+),K(+)-ATPase. This physiological module thus allows the obligate but electroneutral H(+),K(+)-ATPase to generate an asymmetric voltage gradient on the left and right sides. Our data reveal a new, bioelectrical component of the mechanisms patterning a large-scale axis in vertebrate embryogenesis.
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Affiliation(s)
- Junji Morokuma
- Center for Regenerative and Developmental Biology, Forsyth Institute, Developmental Biology Department, Harvard School of Dental Medicine, Boston, MA 02115, USA
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Aw S, Adams DS, Qiu D, Levin M. H,K-ATPase protein localization and Kir4.1 function reveal concordance of three axes during early determination of left-right asymmetry. Mech Dev 2008; 125:353-72. [PMID: 18160269 PMCID: PMC2346612 DOI: 10.1016/j.mod.2007.10.011] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 10/05/2007] [Accepted: 10/24/2007] [Indexed: 12/23/2022]
Abstract
Consistent laterality is a fascinating problem, and study of the Xenopus embryo has led to molecular characterization of extremely early steps in left-right patterning: bioelectrical signals produced by ion pumps functioning upstream of asymmetric gene expression. Here, we reveal a number of novel aspects of the H+/K+-ATPase module in chick and frog embryos. Maternal H+/K+-ATPase subunits are asymmetrically localized along the left-right, dorso-ventral, and animal-vegetal axes during the first cleavage stages, in a process dependent on cytoskeletal organization. Using a reporter domain fused to molecular motors, we show that the cytoskeleton of the early frog embryo can provide asymmetric, directional information for subcellular transport along all three axes. Moreover, we show that the Kir4.1 potassium channel, while symmetrically expressed in a dynamic fashion during early cleavages, is required for normal LR asymmetry of frog embryos. Thus, Kir4.1 is an ideal candidate for the K+ ion exit path needed to allow the electroneutral H+/K+-ATPase to generate voltage gradients. In the chick embryo, we show that H+/K+-ATPase and Kir4.1 are expressed in the primitive streak, and that the known requirement for H+/K+-ATPase function in chick asymmetry does not function through effects on the circumferential expression pattern of Connexin43. These data provide details crucial for the mechanistic modeling of the physiological events linking subcellular processes to large-scale patterning and suggest a model where the early cytoskeleton sets up asymmetric ion flux along the left-right axis as a system of planar polarity functioning orthogonal to the apical-basal polarity of the early blastomeres.
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Affiliation(s)
- Sherry Aw
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Dany S. Adams
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Dayong Qiu
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
| | - Michael Levin
- Center for Regenerative and Developmental Biology Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine 140 The Fenway Boston, MA 02115, U.S.A. Tel. (617) 892−8403 Fax: (617) 892−8597
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Large-scale biophysics: ion flows and regeneration. Trends Cell Biol 2007; 17:261-70. [PMID: 17498955 DOI: 10.1016/j.tcb.2007.04.007] [Citation(s) in RCA: 178] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 03/23/2007] [Accepted: 04/25/2007] [Indexed: 11/18/2022]
Abstract
Regeneration requires exquisite orchestration of growth and morphogenesis. A powerful but still largely mysterious system of biophysical signals functions during regeneration, embryonic development and neoplasm. Ion transporters generate pH and voltage gradients, as well as ion fluxes, regulating proliferation, differentiation and migration. Endogenous bioelectrical signals are implicated in the control of wound healing, limb development, left-right patterning and spinal cord regeneration. Recent advances in molecular biology and imaging technology have allowed unprecedented insight into the sources and downstream consequences of ion flows. In complement to the current focus on molecular genetics and stem cell biology, artificial modulation of bioelectrical signals in somatic tissues is a powerful modality that might result in profound advances in understanding and augmentation of regenerative capacity.
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Adams DS, Masi A, Levin M. H+ pump-dependent changes in membrane voltage are an early mechanism necessary and sufficient to induce Xenopus tail regeneration. Development 2007; 134:1323-35. [PMID: 17329365 DOI: 10.1242/dev.02812] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In many systems, ion flows and long-term endogenous voltage gradients regulate patterning events, but molecular details remain mysterious. To establish a mechanistic link between biophysical events and regeneration, we investigated the role of ion transport during Xenopus tail regeneration. We show that activity of the V-ATPase H(+) pump is required for regeneration but not wound healing or tail development. The V-ATPase is specifically upregulated in existing wound cells by 6 hours post-amputation. Pharmacological or molecular genetic loss of V-ATPase function and the consequent strong depolarization abrogates regeneration without inducing apoptosis. Uncut tails are normally mostly polarized, with discrete populations of depolarized cells throughout. After amputation, the normal regeneration bud is depolarized, but by 24 hours post-amputation becomes rapidly repolarized by the activity of the V-ATPase, and an island of depolarized cells appears just anterior to the regeneration bud. Tail buds in a non-regenerative ;refractory' state instead remain highly depolarized relative to uncut or regenerating tails. Depolarization caused by V-ATPase loss-of-function results in a drastic reduction of cell proliferation in the bud, a profound mispatterning of neural components, and a failure to regenerate. Crucially, induction of H(+) flux is sufficient to rescue axonal patterning and tail outgrowth in otherwise non-regenerative conditions. These data provide the first detailed mechanistic synthesis of bioelectrical, molecular and cell-biological events underlying the regeneration of a complex vertebrate structure that includes spinal cord, and suggest a model of the biophysical and molecular steps underlying tail regeneration. Control of H(+) flows represents a very important new modality that, together with traditional biochemical approaches, may eventually allow augmentation of regeneration for therapeutic applications.
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Affiliation(s)
- Dany S Adams
- Center for Regenerative and Developmental Biology, Forsyth Institute, and Developmental Biology Department, Harvard School of Dental Medicine, 140 The Fenway, Boston, MA 02115, USA
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