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Abstract
Most experiments observing cell migration use planar plastic or glass surfaces despite these conditions being considerably different from physiological ones. On such planar surfaces, cells take a dorsal-ventral polarity to move two-dimensionally. Cells in tissues, however, interact with surrounding cells and the extracellular matrix such that they transverse three-dimensionally. For this reason, three-dimensional matrices have become more and more popular for cell migration experiments. In addition, recent developments in imaging techniques have enabled high resolution observations of in vivo cell migration. The combination of three-dimensional matrices and such imaging techniques has revealed motile mechanisms in tissues not observable in studies using planar surfaces. Regarding models for such cell migration studies, the cellular slime mould Dictyostelium discoideum is ideal. Single amoeboid cells aggregate into hemispherical mound structures upon starvation to begin a multicellular morphogenesis. These tiny and simple multicellular bodies are suitable for observing the behaviors of individual cells in multicellular structures. Furthermore, the unique life cycle can be exploited to identify which genes are involved in cell migration in multicellular environments. Since mutants lacking such genes are expected to fail to undergo morphogenesis, easy and systematic gene screening is possible by isolating mutants whose developments arrest around the mound stage, which is the case for several mutants lacking specific cytoskeletal proteins. In this article, I discuss the basic elements required for cell migration in multicellular environments and how Dictyostelium can be used to elucidate them.
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Affiliation(s)
- Masatsune Tsujioka
- Special Research Promotion Group, Graduate School of Frontier Bioscience, Osaka University, 1-3 Yamadaoka, Suita, Japan.
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52
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Social interaction in synthetic and natural microbial communities. Mol Syst Biol 2011; 7:483. [PMID: 21487402 PMCID: PMC3101950 DOI: 10.1038/msb.2011.16] [Citation(s) in RCA: 128] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Accepted: 03/08/2011] [Indexed: 12/13/2022] Open
Abstract
How do molecular networks at the single-cell level define collective cell behavior? This Review discusses recent studies on synthetic and natural microbial communities that dissect the molecular and dynamical mechanisms underlying microbial social evolution. Social interaction among cells is essential for multicellular complexity. But how do molecular networks within individual cells confer the ability to interact? And how do those same networks evolve from the evolutionary conflict between individual- and population-level interests? Recent studies have dissected social interaction at the molecular level by analyzing both synthetic and natural microbial populations. These studies shed new light on the role of population structure for the evolution of cooperative interactions and revealed novel molecular mechanisms that stabilize cooperation among cells. New understanding of populations is changing our view of microbial processes, such as pathogenesis and antibiotic resistance, and suggests new ways to fight infection by exploiting social interaction. The study of social interaction is also challenging established paradigms in cancer evolution and immune system dynamics. Finding similar patterns in such diverse systems suggests that the same ‘social interaction motifs' may be general to many cell populations.
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53
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A discrete model to study reaction-diffusion-mechanics systems. PLoS One 2011; 6:e21934. [PMID: 21804911 PMCID: PMC3133613 DOI: 10.1371/journal.pone.0021934] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2011] [Accepted: 06/10/2011] [Indexed: 11/28/2022] Open
Abstract
This article introduces a discrete reaction-diffusion-mechanics (dRDM) model to study the effects of deformation on reaction-diffusion (RD) processes. The dRDM framework employs a FitzHugh-Nagumo type RD model coupled to a mass-lattice model, that undergoes finite deformations. The dRDM model describes a material whose elastic properties are described by a generalized Hooke's law for finite deformations (Seth material). Numerically, the dRDM approach combines a finite difference approach for the RD equations with a Verlet integration scheme for the equations of the mass-lattice system. Using this framework results were reproduced on self-organized pacemaking activity that have been previously found with a continuous RD mechanics model. Mechanisms that determine the period of pacemakers and its dependency on the medium size are identified. Finally it is shown how the drift direction of pacemakers in RDM systems is related to the spatial distribution of deformation and curvature effects.
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54
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Marmaras A, Berge U, Ferrari A, Kurtcuoglu V, Poulikakos D, Kroschewski R. A mathematical method for the 3D analysis of rotating deformable systems applied on lumen-forming MDCK cell aggregates. Cytoskeleton (Hoboken) 2010; 67:224-40. [PMID: 20183868 DOI: 10.1002/cm.20438] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Cell motility contributes to the formation of organs and tissues, into which multiple cells self-organize. However such mammalian cellular motilities are not characterized in a quantitative manner and the systemic consequences are thus unknown. A mathematical tool to decipher cell motility, accounting for changes in cell shape, within a three-dimensional (3D) cell system was missing. We report here such a tool, usable on segmented images reporting the outline of clusters (cells) and allowing the time-resolved 3D analysis of circular motility of these as parts of a system (cell aggregate). Our method can analyze circular motility in sub-cellular, cellular, multi-cellular, and also non-cellular systems for which time-resolved segmented cluster outlines are available. To exemplify, we characterized the circular motility of lumen-initiating MDCK cell aggregates, embedded in extracellular matrix. We show that the organization of the major surrounding matrix fibers was not significantly affected during this cohort rotation. Using our developed tool, we discovered two classes of circular motion, rotation and random walk, organized in three behavior patterns during lumen initiation. As rotational movements were more rapid than random walk and as both could continue during lumen initiation, we conclude that neither the class nor the rate of motion regulates lumen initiation. We thus reveal a high degree of plasticity during a developmentally critical cell polarization step, indicating that lumen initiation is a robust process. However, motility rates decreased with increasing cell number, previously shown to correlate with epithelial polarization, suggesting that migratory polarization is converted into epithelial polarization during aggregate development.
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Affiliation(s)
- Anastasios Marmaras
- Laboratory of Thermodynamics in Emerging Technologies, Department of Mechanical and Process Engineering, ETH Zurich, Zurich, Switzerland
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55
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Galardi-Castilla M, Garciandía A, Suarez T, Sastre L. The Dictyostelium discoideum acaA gene is transcribed from alternative promoters during aggregation and multicellular development. PLoS One 2010; 5:e13286. [PMID: 20949015 PMCID: PMC2952602 DOI: 10.1371/journal.pone.0013286] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Accepted: 09/15/2010] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Extracellular cAMP is a key extracellular signaling molecule that regulates aggregation, cell differentiation and morphogenesis during multi-cellular development of the social amoeba Dictyostelium discoideum. This molecule is produced by three different adenylyl cyclases, encoded by the genes acaA, acrA and acgA, expressed at different stages of development and in different structures. METHODOLOGY/PRINCIPAL FINDINGS This article describes the characterization of the promoter region of the acaA gene, showing that it is transcribed from three different alternative promoters. The distal promoter, promoter 1, is active during the aggregation process while the more proximal promoters are active in tip-organiser and posterior regions of the structures. A DNA fragment containing the three promoters drove expression to these same regions and similar results were obtained by in situ hybridization. Analyses of mRNA expression by quantitative RT-PCR with specific primers for each of the three transcripts also demonstrated their different temporal patterns of expression. CONCLUSIONS/SIGNIFICANCE The existence of an aggregation-specific promoter can be associated with the use of cAMP as chemo-attractant molecule, which is specific for some Dictyostelium species. Expression at late developmental stages indicates that adenylyl cyclase A might play a more important role in post-aggregative development than previously considered.
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Affiliation(s)
- Maria Galardi-Castilla
- Instituto de Investigaciones Biomédicas, Consejo Superior de Investigaciones Cientificas/Universidad Autónoma de Madrid, Madrid, Spain
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56
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McCann CP, Kriebel PW, Parent CA, Losert W. Cell speed, persistence and information transmission during signal relay and collective migration. J Cell Sci 2010; 123:1724-31. [PMID: 20427323 DOI: 10.1242/jcs.060137] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Collective migration is a key feature of the social amoebae Dictyostelium discoideum, where the binding of chemoattractants leads to the production and secretion of additional chemoattractant and the relay of the signal to neighboring cells. This then guides cells to migrate collectively in a head-to-tail fashion. We used mutants that were defective in signal relay to elucidate which quantitative metrics of cell migration are most strongly affected by signal relay and collective motion. We show that neither signal relay nor collective motion markedly impact the speed of cell migration. Cells maintained a preferred overall direction of motion for several minutes with similar persistence, regardless of whether or not they were attracted to moving neighbors, moving collectively in contact with their neighbors, or simply following a fixed exogenous signal. We quantitatively establish that signal relay not only increases the number of cells that respond to a chemotactic signal, but most remarkably, also transmits information about the location of the source accurately over large distances, independently of the strength of the exogenous signal. We envision that signal relay has a similar key role in the migration of a variety of chemotaxing mammalian cells that can relay chemoattractant signals.
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Affiliation(s)
- Colin P McCann
- Department of Physics, University of Maryland College Park, College Park, MD 20742-4111, USA
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57
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Binamé F, Pawlak G, Roux P, Hibner U. What makes cells move: requirements and obstacles for spontaneous cell motility. MOLECULAR BIOSYSTEMS 2010; 6:648-61. [PMID: 20237642 DOI: 10.1039/b915591k] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Movement of individual cells and of cellular cohorts, chains or sheets requires physical forces that are established through interactions of cells with their environment. In vivo, migration occurs extensively during embryonic development and in adults during wound healing and tumorigenesis. In order to identify the molecular events involved in cell movement, in vitro systems have been developed. These have contributed to the definition of a number of molecular pathways put into play in the course of migratory behaviours, such as mesenchymal and amoeboid movement. More recently, our knowledge of migratory modes has been enriched by analyses of cells exploring and moving through three-dimensional (3D) matrices. While the cells' morphologies differ in 2D and 3D environments, the basic mechanisms that put a cellular body into motion are remarkably similar. Thus, in both 2D and 3D, the polarity of the migrating cell is initially defined by a specific subcellular localization of signalling molecules and components of molecular machines required for motion. While the polarization can be initiated either in response to extracellular signalling or be a chance occurrence, it is reinforced and sustained by positive feedback loops of signalling molecules. Second, adhesion to a substratum is necessary to generate forces that will propel the cell engaged in either mesenchymal or ameboid migration. For collective cell movement, intercellular coordination constitutes an additional requirement: a cell cohort remains stationary if individual cells pull in opposite directions. Finally, the availability of space to move into is a general requirement to set cells into motion. Lack of free space is probably the main obstacle for migration of most healthy cells in an adult multicellular organism. Thus, the requirements for cell movement are both intrinsic to the cell, involving coordinated signalling and interactions with molecular machines, and extrinsic, imposed by the physicochemical nature of the environment. In particular, the geometry and stiffness of the support act on a range of signalling pathways that induce specific cell migratory responses. These issues are discussed in the present review in the context of published work and our own data on collective migration of hepatocyte cohorts.
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Affiliation(s)
- Fabien Binamé
- CNRS, UMR 5535, IGMM, 1919 route de Mende, 34293 Montpellier, France
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58
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Chen PW, Randazzo PA, Parent CA. ACAP-A/B are ArfGAP homologs in dictyostelium involved in sporulation but not in chemotaxis. PLoS One 2010; 5:e8624. [PMID: 20062541 PMCID: PMC2797641 DOI: 10.1371/journal.pone.0008624] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2009] [Accepted: 12/14/2009] [Indexed: 11/29/2022] Open
Abstract
Arfs and Arf GTPase-activating proteins (ArfGAPs) are regulators of membrane trafficking and actin dynamics in mammalian cells. In this study, we identified a primordial Arf, ArfA, and two ArfGAPs (ACAP-A/B) containing BAR, PH, ArfGAP and Ankyrin repeat domains in the eukaryote Dictyostelium discoideum. In vitro, ArfA has similar nucleotide binding properties as mammalian Arfs and, with GTP bound, is a substrate for ACAP-A and B. We also investigated the physiological functions of ACAP-A/B by characterizing cells lacking both ACAP-A and B. Although ACAP-A/B knockout cells showed no defects in cell growth, migration or chemotaxis, they exhibited abnormal actin protrusions and ∼50% reduction in spore yield. We conclude that while ACAP-A/B have a conserved biochemical mechanism and effect on actin organization, their role in migration is not conserved. The absence of an effect on Dictyostelium migration may be due to a specific requirement for ACAPs in mesenchymal migration, which is observed in epithelial cancer cells where most studies of mammalian ArfGAPs were performed.
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Affiliation(s)
- Pei-Wen Chen
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, Maryland, United States of America
| | - Paul A. Randazzo
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, Maryland, United States of America
- * E-mail:
| | - Carole A. Parent
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, Bethesda, Maryland, United States of America
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59
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Abstract
For all animals, cell migration is an essential and highly regulated process. Cells migrate to shape tissues, to vascularize tissues, in wound healing, and as part of the immune response. Unfortunately, tumor cells can also become migratory and invade surrounding tissues. Some cells migrate as individuals, but many cell types will, under physiological conditions, migrate collectively in tightly or loosely associated groups. This includes invasive tumor cells. This review discusses different types of collective cell migration, including sheet movement, sprouting and branching, streams, and free groups, and highlights recent findings that provide insight into cells' organization and behavior. Cells performing collective migration share many cell biological characteristics with independently migrating cells but, by affecting one another mechanically and via signaling, these cell groups are subject to additional regulation and constraints. New properties that emerge from this connectivity can contribute to shaping, guiding, and ultimately ensuring tissue function.
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Affiliation(s)
- Pernille Rørth
- Temasek Life Sciences Laboratory and Department of Biological Sciences, The National University of Singapore, Singapore.
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60
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Abstract
Collective cell migration is a key process during the development of most organisms. It can involve either the migration of closely packed mesenchymal cells that make dynamic contacts with frequently changing neighbour cells, or the migration of epithelial sheets that typically display more stable cell-cell interactions and less frequent changes in neighbours. These collective movements can be controlled by short- or long-range dynamic gradients of extracellular signalling molecules, depending on the number of cells involved and their distance of migration. These gradients are sensed by some or all of the migrating cells and translated into directed migration, which in many settings is further modulated by cell-contact-mediated attractive or repulsive interactions that result in contact-following or contact-inhibition of locomotion, respectively. Studies of collective migration of groups of epithelial cells during development indicate that, in some cases, only leader cells sense and migrate up an external signal gradient, and that adjacent cells follow through strong cell-cell contacts. In this Commentary, I review studies of collective cell migration of differently sized cell populations during the development of several model organisms, and discuss our current understanding of the molecular mechanisms that coordinate this migration.
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Affiliation(s)
- Cornelis J Weijer
- Division of Cell and Developmental Biology, Wellcome Trust Biocentre, College of Life Sciences, University of Dundee, Dundee DD1 5EH, UK.
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61
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Chuai M, Dormann D, Weijer CJ. Imaging cell signalling and movement in development. Semin Cell Dev Biol 2009; 20:947-55. [DOI: 10.1016/j.semcdb.2009.09.001] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2009] [Revised: 09/01/2009] [Accepted: 09/03/2009] [Indexed: 10/20/2022]
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62
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Friedl P, Gilmour D. Collective cell migration in morphogenesis, regeneration and cancer. Nat Rev Mol Cell Biol 2009; 10:445-57. [DOI: 10.1038/nrm2720] [Citation(s) in RCA: 1832] [Impact Index Per Article: 122.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
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63
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Ostrowski EA, Katoh M, Shaulsky G, Queller DC, Strassmann JE. Kin discrimination increases with genetic distance in a social amoeba. PLoS Biol 2009; 6:e287. [PMID: 19067487 PMCID: PMC2586364 DOI: 10.1371/journal.pbio.0060287] [Citation(s) in RCA: 106] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2008] [Accepted: 10/10/2008] [Indexed: 12/04/2022] Open
Abstract
In the social amoeba Dictyostelium discoideum, thousands of cells aggregate upon starvation to form a multicellular fruiting body, and approximately 20% of them die to form a stalk that benefits the others. The aggregative nature of multicellular development makes the cells vulnerable to exploitation by cheaters, and the potential for cheating is indeed high. Cells might avoid being victimized if they can discriminate among individuals and avoid those that are genetically different. We tested how widely social amoebae cooperate by mixing isolates from different localities that cover most of their natural range. We show here that different isolates partially exclude one another during aggregation, and there is a positive relationship between the extent of this exclusion and the genetic distance between strains. Our findings demonstrate that D. discoideum cells co-aggregate more with genetically similar than dissimilar individuals, suggesting the existence of a mechanism that discerns the degree of genetic similarity between individuals in this social microorganism. In social amoebae such as Dictyostelium discoideum, cells aggregate to form a multicellular slug that migrates and then forms a fruiting body, which contains live spores (which go on to make new amoebae) and dead stalk cells. Unlike animals where all the cells descend from one fertilized egg, social amoeba fruiting bodies can contain cells with different genotypes. This potential for chimerism creates a conceptual problem in that “cheater” cells could arise that preferentially become reproductive spores and force the victims to become stalk cells and die. One way that amoebae could avoid being cheated is if they recognize and preferentially aggregate with genetically similar cells while avoiding genetically distant cells—a process called kin discrimination. We tested whether cells of D. discoideum could discriminate in this way. We mixed cells from genetically distinct strains and found that they segregate during multicellular development. The degree of segregation increases in a graded fashion with the genetic distance between strains. Our results demonstrate the existence of kin discrimination in D. discoideum, an ability that is likely to reduce the potential for cheating and ensure that the death of the stalk cells provides a fitness advantage to related individuals. Genetically based discrimination in social amoebae may help these cells to avoid cheaters that take advantage of their altruistic behavior.
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Affiliation(s)
- Elizabeth A Ostrowski
- Department of Ecology and Evolutionary Biology, Rice University, Houston, Texas, USA.
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64
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Sultana H, Neelakanta G, Eichinger L, Rivero F, Noegel AA. Microarray phenotyping places cyclase associated protein CAP at the crossroad of signaling pathways reorganizing the actin cytoskeleton in Dictyostelium. Exp Cell Res 2009; 315:127-40. [DOI: 10.1016/j.yexcr.2008.10.023] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2008] [Revised: 08/29/2008] [Accepted: 10/14/2008] [Indexed: 01/31/2023]
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65
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Abstract
The ability of cells to migrate in response to external cues, a process known as chemotaxis, is a fundamental phenomenon in biology. It is exhibited by a wide variety of cell types in the context of embryogenesis, angiogenesis, inflammation, wound healing and many other complex physiological processes. Here, we discuss the signals that control the directed migration of the social amoebae Dictyostelium discoideum both as single cells and in the context of group migration. This multi-cellular organism has served as an excellent model system to decipher amoeboid-like leukocyte migration and has played a key role in establishing signalling paradigms in the chemotaxis field. We envision that Dictyostelium will continue to bring forward basic knowledge as we seek to understand the mechanisms regulating group cell migration.
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Affiliation(s)
- G L Garcia
- Laboratory of Cellular and Molecular Biology, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4255, USA
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66
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Li HL, Song LS, Qian PY. Cyclic AMP concentration and protein kinase A (PKA) gene expression at different developmental stages of the polychaete Hydroides elegans. JOURNAL OF EXPERIMENTAL ZOOLOGY PART B-MOLECULAR AND DEVELOPMENTAL EVOLUTION 2008; 310:417-27. [PMID: 18335538 DOI: 10.1002/jez.b.21214] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) showed inductive effect on larval settlement of the polychaete Hydroides elegans. It has been suggested that IBMX triggers larval settlement by elevating the cellular adenosine 3',5'-cyclic monophosphate (cAMP) level in this species. To test this hypothesis, we first examined cAMP-level changes in both the competent (CL) and attached larvae (AL) and then characterized the cAMP-dependent protein kinase in H. elegans, which is the major mediator of cAMP action. Tissue extracts of the larvae were assayed for cAMP by enzyme immunoassay; the results showed that IBMX increased cAMP production up to approximately two-folds in the CL. However, there was no significant difference in the cAMP concentration between the CL and AL that were not treated with IBMX. The catalytic subunit of protein kinase A gene from H. elegans (designated HePKAc) was cloned, and its expression in different developmental stages of H. elegans was examined using quantitative real-time polymerase chain reaction. The gene expression level in the pre-competent trochophore larvae was the lowest, increased in the CL, reached the highest in the larvae undergoing normal and IBMX-induced metamorphosis, and then decreased in the adult stage. In situ hybridization results showed that HePKAc expressed mainly around eye regions and along body fragments of the CL and AL. Our results indicated that the IBMX-induced cAMP changes and the cAMP-dependent protein kinase gene may mediate larval development and settlement of H. elegans.
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Affiliation(s)
- Hong-Lei Li
- Atmospheric, Marine, and Coastal Environment Program and Coastal Marine Laboratory, Department of Biology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, People's Republic of China
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67
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Ghosh R, Chhabra A, Phatale PA, Samrat SK, Sharma J, Gosain A, Mohanty D, Saran S, Gokhale RS. Dissecting the functional role of polyketide synthases in Dictyostelium discoideum: biosynthesis of the differentiation regulating factor 4-methyl-5-pentylbenzene-1,3-diol. J Biol Chem 2008; 283:11348-54. [PMID: 18252726 DOI: 10.1074/jbc.m709588200] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dictyostelium discoideum exhibits the largest repository of polyketide synthase (PKS) proteins of all known genomes. However, the functional relevance of these proteins in the biology of this organism remains largely obscure. On the basis of computational, biochemical, and gene expression studies, we propose that the multifunctional Dictyostelium PKS (DiPKS) protein DiPKS1 could be involved in the biosynthesis of the differentiation regulating factor 4-methyl-5-pentylbenzene-1,3-diol (MPBD). Our cell-free reconstitution studies of a novel acyl carrier protein Type III PKS didomain from DiPKS1 revealed a crucial role of protein-protein interactions in determining the final biosynthetic product. Whereas the Type III PKS domain by itself primarily produces acyl pyrones, the presence of the interacting acyl carrier protein domain modulates the catalytic activity to produce the alkyl resorcinol scaffold of MPBD. Furthermore, we have characterized an O-methyltransferase (OMT12) from Dictyostelium with the capability to modify this resorcinol ring to synthesize a variant of MPBD. We propose that such a modification in vivo could in fact provide subtle variations in biological function and specificity. In addition, we have performed systematic computational analysis of 45 multidomain PKSs, which revealed several unique features in DiPKS proteins. Our studies provide a new perspective in understanding mechanisms by which metabolic diversity could be generated by combining existing functional scaffolds.
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Affiliation(s)
- Ratna Ghosh
- National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi, India
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68
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Egel R, Penny D. On the Origin of Meiosis in Eukaryotic Evolution: Coevolution of Meiosis and Mitosis from Feeble Beginnings. RECOMBINATION AND MEIOSIS 2007. [DOI: 10.1007/7050_2007_036] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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69
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A GPCR involved in post aggregation events in Dictyostelium discoideum. Dev Biol 2007; 312:29-43. [PMID: 17950724 DOI: 10.1016/j.ydbio.2007.08.055] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Revised: 08/27/2007] [Accepted: 08/28/2007] [Indexed: 02/07/2023]
Abstract
Dictyostelium has 55 genes encoding seven-transmembrane G-protein-coupled receptors (GPCR) that belong to five of the six GPCR families. GrlA is one of the 17 family 3 GPCRs in Dictyostelium all of which resemble GABA(B) receptors from higher eukaryotes. GrlA is a 90-kDa protein present on the plasma membrane and on membranes of the ER. It has a large extracellular domain with homology to bacterial periplasmic proteins. The GrlA message is present throughout development and shows increased levels during the post aggregation stages. Inactivation of the grlA gene does not severely affect the growth phase, however, it leads to a delay in the development at the post aggregation stage. GrlA deficient strains show an altered DIF-1 response specific to the prestalk-specific ecmA and ecmB gene, reduced car2 and pkaC transcript levels and form a reduced number of spores. Germination of the spores was as in wild type. Transcriptional profiling supported the defect in the sporulation pathway as a large number of genes involved in the biogenesis and organization of the extracellular matrix and the sporulation process were significantly downregulated in the mutant.
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70
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Panfilov AV, Keldermann RH, Nash MP. Drift and breakup of spiral waves in reaction-diffusion-mechanics systems. Proc Natl Acad Sci U S A 2007; 104:7922-6. [PMID: 17468396 PMCID: PMC1876548 DOI: 10.1073/pnas.0701895104] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Rotating spiral waves organize excitation in various biological, physical, and chemical systems. They underpin a variety of important phenomena, such as cardiac arrhythmias, morphogenesis processes, and spatial patterns in chemical reactions. Important insights into spiral wave dynamics have been obtained from theoretical studies of the reaction-diffusion (RD) partial differential equations. However, most of these studies have ignored the fact that spiral wave rotation is often accompanied by substantial deformations of the medium. Here, we show that joint consideration of the RD equations with the equations of continuum mechanics for tissue deformations (RD-mechanics systems), yield important effects on spiral wave dynamics. We show that deformation can induce the breakup of spiral waves into complex spatiotemporal patterns. We also show that mechanics leads to spiral wave drift throughout the medium approaching dynamical attractors, which are determined by the parameters of the model and the size of the medium. We study mechanisms of these effects and discuss their applicability to the theory of cardiac arrhythmias. Overall, we demonstrate the importance of RD-mechanics systems for mathematics applied to life sciences.
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Affiliation(s)
- A V Panfilov
- Department of Theoretical Biology, Utrecht University, Padualaan 8, Utrecht 3584 CH, The Netherlands.
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71
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Wilhelm C, Rivière C, Biais N. Magnetic control of Dictyostelium aggregation. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 75:041906. [PMID: 17500920 DOI: 10.1103/physreve.75.041906] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/27/2006] [Revised: 01/22/2007] [Indexed: 05/15/2023]
Abstract
We report the control of cell migration by external magnetic forces during the early stage of Dictysostelium discoideum morphogenesis. Magnetically labeled aggregating cells respond to the presence of a magnetic field created by a thin magnetic tip: forces as low as 30 pN are sufficient to elicit the aggregation of the cells at the extremity of the tip. This induced magnetotaxis is competitive to classical chemotaxis. We therefore underline the interplay between external mechanical forces and morphogenesis. This magnetic assay will open new possibilities in the study of morphogenesis in Dictyostelium.
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Affiliation(s)
- C Wilhelm
- Laboratoire Matière et Systèmes Complexes, CNRS UMR 7057-Université Paris 7, Paris, France.
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72
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Arasada R, Gloss A, Tunggal B, Joseph JM, Rieger D, Mondal S, Faix J, Schleicher M, Noegel AA. Profilin isoforms in Dictyostelium discoideum. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2007; 1773:631-41. [PMID: 17467078 DOI: 10.1016/j.bbamcr.2007.03.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2006] [Revised: 03/13/2007] [Accepted: 03/14/2007] [Indexed: 11/21/2022]
Abstract
Eukaryotic cells contain a large number of actin binding proteins of different functions, locations and concentrations. They bind either to monomeric actin (G-actin) or to actin filaments (F-actin) and thus regulate the dynamic rearrangement of the actin cytoskeleton. The Dictyostelium discoideum genome harbors representatives of all G-actin binding proteins including actobindin, twinfilin, and profilin. A phylogenetic analysis of all profilins suggests that two distinguishable groups emerged very early in evolution and comprise either vertebrate and viral profilins or profilins from all other organisms. The newly discovered profilin III isoform in D. discoideum shows all functions that are typical for a profilin. However, the concentration of the third isoform in wild type cells reaches only about 0.5% of total profilin. In a yeast-2-hybrid assay profilin III was found to bind specifically to the proline-rich region of the cytoskeleton-associated vasodilator-stimulated phosphoprotein (VASP). Immunolocalization studies showed similar to VASP the profilin III isoform in filopodia and an enrichment at their tips. Cells lacking the profilin III isoform show defects in cell motility during chemotaxis. The low abundance and the specific interaction with VASP argue against a significant actin sequestering function of the profilin III isoform.
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Affiliation(s)
- Rajesh Arasada
- Adolf-Butenandt-Inst.-Zellbiologie, Ludwig-Maximilians-Universität, Schillerstrasse 42, 80336 München, Germany
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73
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Khaire N, Müller R, Blau-Wasser R, Eichinger L, Schleicher M, Rief M, Holak TA, Noegel AA. Filamin-regulated F-actin Assembly Is Essential for Morphogenesis and Controls Phototaxis in Dictyostelium. J Biol Chem 2007; 282:1948-55. [PMID: 17121815 DOI: 10.1074/jbc.m610262200] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Dictyostelium strains lacking the F-actin cross-linking protein filamin (ddFLN) have a severe phototaxis defect at the multicellular slug stage. Filamins are rod-shaped homodimers that cross-link the actin cytoskeleton into highly viscous, orthogonal networks. Each monomer chain of filamin is comprised of an F-actin-binding domain and a rod domain. In rescue experiments only intact filamin re-established correct phototaxis in filamin minus mutants, whereas C-terminally truncated filamin proteins that had lost the dimerization domain and molecules lacking internal repeats but retaining the dimerization domain did not rescue the phototaxis defect. Deletion of individual rod repeats also changed their subcellular localization, and mutant filamins in general were less enriched at the cell cortex as compared with the full-length protein and were increasingly present in the cytoplasm. For correct phototaxis ddFLN is only required at the tip of the slug because expression under control of the cell type-specific extracellular-matrix protein A (ecmA) promoter and mixing experiments with wild type cells supported phototactic orientation. Likewise, in chimeric slugs wild type cells were primarily found at the tip of the slug, which acts as an organizer in Dictyostelium morphogenesis.
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Affiliation(s)
- Nandkumar Khaire
- Institut für Biochemie I, Zentrum Molekulare Medizin Köln, Medizinische Fakultät, Universität zu Köln, 50931 Köln, Germany
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74
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Singleton CK, Kirsten JH, Dinsmore CJ. Function of ammonium transporter A in the initiation of culmination of development in Dictyostelium discoideum. EUKARYOTIC CELL 2006; 5:991-6. [PMID: 16835443 PMCID: PMC1489295 DOI: 10.1128/ec.00058-06] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The histidine kinase DhkC controls a phosphorelay involved in regulating the slug versus culmination choice during the multicellular developmental program of Dictyostelium discoideum. When the relay is active, slug migration is favored due to the activation of a cyclic AMP (cAMP) phosphodiesterase and the resultant lowering of the intracellular and extracellular levels of cAMP. Ammonia signaling represents one input into the DhkC phosphorelay, and previous studies indicated that the ammonium transporter C inhibits the relay in response to low ammonia levels. Evidence is presented that another member of the family of ammonium transporters, AmtA, also regulates the slug/culmination choice. Under standard conditions of development, the wild-type strain requires a transitional period of 2 to 3 h to go from fingers to culminants, with some slugs forming and migrating briefly prior to culmination. In contrast, amtA null cells, like cells that lack DhkC, possessed a transitional period of only 1 to 2 h and rarely formed slugs. Disruption of amtA in an amtC null strain overcame the slugger phenotype of that strain and restored its ability to culminate. Strains lacking AmtA were insensitive to the ability of ammonia to promote and prolong slug migration. These findings lead to the proposal that AmtA functions in ammonia sensing as an activator of the DhkC phosphorelay in response to perceived high ammonia levels.
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Affiliation(s)
- Charles K Singleton
- Department of Biological Sciences, Vanderbilt University, VU Station B 351634, Nashville, Tennessee 37235-1634, USA.
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75
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Abstract
Traditionally, living organisms have often been classified into two main categories: unicellular and multicellular. In recent years, however, the boundary between these two groups has become less strict and clear than was previously presumed. Studies on the communities formed by unicellular microorganisms have revealed that various properties and processes so far mainly associated with metazoa are also important for the proper development, survival and behaviour of muticellular microbial populations. In this review, we present various examples of this, using a yeast colony as representative of a structured organized microbial community. Among other things, we will show how the differentiation of yeast cells within a colony can be important for the long-term survival of a community under conditions of nutrient shortage, how colony development and physiology can be influenced by the environment, and how a group of colonies can synchronize their developmental changes. In the last section, we introduce examples of molecular mechanisms that can participate in some aspects of the behaviour of yeast populations.
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Affiliation(s)
- Zdena Palková
- Department of Genetics and Microbiology, Charles University, Prague, Czech Republic.
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76
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Jeong SY, Choi CH, Kim JS, Park SJ, Kang SO. Thioredoxin reductase is required for growth and regulates entry into culmination of Dictyostelium discoideum. Mol Microbiol 2006; 61:1443-56. [PMID: 16899077 DOI: 10.1111/j.1365-2958.2006.05329.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The thioredoxin system, consisting of thioredoxin, thioredoxin reductase and NADPH, has been well established to be critical for the redox regulation of protein function and signalling. To investigate the role of thioredoxin reductase (Trr) in Dictyostelium discoideum, we generated mutant cells that underexpress or overexpress Trr. Trr-underexpressing cells exhibited severe defects in axenic growth and development. Trr-overexpressing (TrrOE) cells formed very tiny plaques on a bacterial lawn and had a lower rate of bacterial uptake. When developed in the dark, TrrOE cells exhibited a slugger phenotype, defined by a prolonged migrating slug stage. Like other slugger mutants, they were hypersensitive to ammonia, which has been known to inhibit culmination by raising the pH of intracellular acidic compartments. Interestingly, TrrOE cells showed defective acidification of intracellular compartments and decreased activity of vacuolar H+-ATPase which functions in the acidification of intracellular compartments. Moreover, biochemical studies revealed that the thioredoxin system can directly reduce the catalytic subunit of vacuolar H+-ATPase whose activity is regulated by reversible disulphide bond formation. Taken together, these results suggest that Dictyostelium Trr may be essential for growth and play a role in regulation of phagocytosis and culmination, possibly through the modulation of vacuolar H+-ATPase activity.
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Affiliation(s)
- Sun-Young Jeong
- Laboratory of Biophysics, School of Biological Sciences, and Institute of Microbiology, Seoul National University, Seoul 151-742, Korea
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77
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Abstract
Cell migration is an essential process during many phases of development and adult life. Cells can either migrate as individuals or move in the context of tissues. Movement is controlled by internal and external signals, which activate complex signal transduction cascades resulting in highly dynamic and localised remodelling of the cytoskeleton, cell-cell and cell-substrate interactions. To understand these processes, it will be necessary to identify the critical structural cytoskeletal components, their spatio-temporal dynamics as well as those of the signalling pathways that control them. Imaging plays an increasingly important and powerful role in the analysis of these spatio-temporal dynamics. We will highlight a variety of imaging techniques and their use in the investigation of various aspects of cell motility, and illustrate their role in the characterisation of chemotaxis in Dictyostelium and cell movement during gastrulation in chick embryos in more detail.
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Affiliation(s)
- Dirk Dormann
- Division of Cell and Developmental Biology, School of Life sciences, University of Dundee, Dundee, UK
| | - Cornelis J Weijer
- Division of Cell and Developmental Biology, School of Life sciences, University of Dundee, Dundee, UK
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78
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Peter R, Zimmermann W. Traveling ion channel density waves affected by a conservation law. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 74:016206. [PMID: 16907176 DOI: 10.1103/physreve.74.016206] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/13/2006] [Indexed: 05/11/2023]
Abstract
A model of mobile, charged ion channels embedded in a biomembrane is investigated. The ion channels fluctuate between an opened and a closed state according to a simple two-state reaction scheme whereas the total number of ion channels is a conserved quantity. Local transport mechanisms suggest that the ion channel densities are governed by electrodiffusionlike equations that have to be supplemented by a cable-type equation describing the dynamics of the transmembrane voltage. It is shown that the homogeneous distribution of ion channels may become unstable to either a stationary or an oscillatory instability. The nonlinear behavior immediately above threshold of an oscillatory bifurcation occurring at finite wave number is analyzed in terms of amplitude equations. Due to the conservation law imposed on ion channels, large-scale modes couple to the finite-wave-number instability and have thus to be included in the asymptotic analysis near the onset of pattern formation. A modified Ginzburg-Landau equation extended by long-wavelength stationary excitations is established, and it is highlighted how the global conservation law affects the stability of traveling ion channel density waves.
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Affiliation(s)
- Ronny Peter
- Theoretische Physik, Universität Bayreuth, D-95440 Bayreuth, Germany
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79
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Dormann D, Weijer CJ. Chemotactic cell movement during Dictyostelium development and gastrulation. Curr Opin Genet Dev 2006; 16:367-73. [PMID: 16782325 DOI: 10.1016/j.gde.2006.06.003] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2006] [Accepted: 06/08/2006] [Indexed: 11/26/2022]
Abstract
Many developmental processes involve chemotactic cell movement up or down dynamic chemical gradients. Studies of the molecular mechanisms of chemotactic movement of Dictyostelium amoebae up cAMP gradients highlight the importance of PIP3 signaling in the control of cAMP-dependent actin polymerization, which drives the protrusion of lamellipodia and filopodia at the leading edge of the cell, but also emphasize the need for myosin thick filament assembly and motor activation for the contraction of the back of the cell. These process become even more important during the multicellular stages of development, when propagating waves of cAMP coordinate the chemotactic movement of tens of thousands of cells, resulting in multicellular morphogenesis. Recent experiments show that chemotaxis, especially in response to members of the FGF, PDGF and VEGF families of growth factors, plays a key role in the guidance of mesoderm cells during gastrulation in chick, mouse and frog embryos. The molecular mechanisms of signal detection and signaling to the actin-myosin cytoskeleton remain to be elucidated.
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Affiliation(s)
- Dirk Dormann
- Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dundee, DD1 5EH, UK
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80
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Goldbeter A. Oscillations and waves of cyclic AMP in Dictyostelium: a prototype for spatio-temporal organization and pulsatile intercellular communication. Bull Math Biol 2006; 68:1095-109. [PMID: 16832740 DOI: 10.1007/s11538-006-9090-z] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2005] [Accepted: 02/03/2006] [Indexed: 10/24/2022]
Abstract
The amoebae Dictyostelium discoideum aggregate after starvation in a wavelike manner in response to periodic pulses of cyclic AMP (cAMP) secreted by cells which behave as aggregation centers. In addition to autonomous oscillations, the cAMP signaling system that controls aggregation is also capable of excitable behavior, which consists in the transient amplification of suprathreshold pulses of extracellular cAMP. Since the first theoretical model for slime mold aggregation proposed by Keller and Segel in 1970, many theoretical studies have addressed various aspects of the mechanism and function of cAMP signaling in Dictyostelium. This paper presents a brief overview of these developments as well as some reminiscences of the author's collaboration with Lee Segel in modeling the dynamics of cAMP relay and oscillations. Considered in turn are models for cAMP signaling in Dictyostelium, the developmental path followed by the cAMP signaling system after starvation, the frequency encoding of cAMP signals, and the origin of concentric or spiral waves of cAMP.
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Affiliation(s)
- Albert Goldbeter
- Unité de Chronobiologie théorique, Faculté des Sciences, Université Libre de Bruxelles, Campus Plaine, C.P. 231, B-1050, Brussels, Belgium.
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81
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Keller L, Surette MG. Communication in bacteria: an ecological and evolutionary perspective. Nat Rev Microbiol 2006; 4:249-58. [PMID: 16501584 DOI: 10.1038/nrmicro1383] [Citation(s) in RCA: 482] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Individual bacteria can alter their behaviour through chemical interactions between organisms in microbial communities - this is generally referred to as quorum sensing. Frequently, these interactions are interpreted in terms of communication to mediate coordinated, multicellular behaviour. We show that the nature of interactions through quorum-sensing chemicals does not simply involve cooperative signals, but entails other interactions such as cues and chemical manipulations. These signals might have a role in conflicts within and between species. The nature of the chemical interaction is important to take into account when studying why and how bacteria react to the chemical substances that are produced by other bacteria.
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Affiliation(s)
- Laurent Keller
- Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland.
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82
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Matsuoka S, Iijima M, Watanabe TM, Kuwayama H, Yanagida T, Devreotes PN, Ueda M. Single-molecule analysis of chemoattractant-stimulated membrane recruitment of a PH-domain-containing protein. J Cell Sci 2006; 119:1071-9. [PMID: 16507590 DOI: 10.1242/jcs.02824] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Molecular mechanisms of chemotactic response are highly conserved among many eukaryotic cells including human leukocytes and Dictyostelium discoideum cells. The cells can sense the differences in chemoattractant concentration across the cell body and respond by extending pseudopods from the cell side facing to a higher concentration. Pseudopod formation is regulated by binding of pleckstrin homology (PH)-domain-containing proteins to phosphatidylinositol 3,4,5-trisphosphates [PtdIns(3,4,5)P3] localized at the leading edge of chemotaxing cells. However, molecular mechanisms underlying dynamic features of a pseudopod have not been fully explained by the known properties of PH-domain-containing proteins. To investigate the mechanisms, we visualized single molecules of green fluorescent protein tagged to Crac (Crac-GFP), a PH-domain-containing protein in D. discoideum cells. Whereas populations of Crac molecules exhibited a stable steady-state localization at pseudopods, individual molecules bound transiently to PtdIns(3,4,5)P3 for approximately 120 milliseconds, indicating dynamic properties of the PH-domain-containing protein. Receptor stimulation did not alter the binding stability but regulated the number of bound PH-domain molecules by metabolism of PtdIns(3,4,5)P3. These results demonstrate that the steady-state localization of PH-domain-containing proteins at the leading edge of chemotaxing cells is dynamically maintained by rapid recycling of individual PH-domain-containing proteins. The short interaction between PH domains and PtdIns(3,4,5)P3 contributes to accurate and sensitive chemotactic movements through the dynamic redistributions. These dynamic properties might be a common feature of signaling components involved in chemotaxis.
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Affiliation(s)
- Satomi Matsuoka
- Laboratories for Nanobiology, Graduate School of Frontier Biosciences, Osaka University, 1-3 Yamadaoka, Suita, Osaka, 565-0871, Japan
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83
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Strmecki L, Greene DM, Pears CJ. Developmental decisions in Dictyostelium discoideum. Dev Biol 2005; 284:25-36. [PMID: 15964562 DOI: 10.1016/j.ydbio.2005.05.011] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2005] [Revised: 04/14/2005] [Accepted: 05/06/2005] [Indexed: 11/28/2022]
Abstract
Dictyostelium discoideum is an excellent system in which to study developmental decisions. Synchronous development is triggered by starvation and rapidly generates a limited number of cell types. Genetic and image analyses have revealed the elegant intricacies associated with this simple development system. Key signaling pathways identified as regulating cell fate decisions are likely to be conserved with metazoa and are providing insight into differentiation decisions under circumstances where considerable cell movement takes place during development.
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Affiliation(s)
- Lana Strmecki
- Department of Biochemistry, University of Oxford, South Parks Road, Oxford OX1 3QU, UK
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84
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Panfilov AV, Keldermann RH, Nash MP. Self-organized pacemakers in a coupled reaction-diffusion-mechanics system. PHYSICAL REVIEW LETTERS 2005; 95:258104. [PMID: 16384515 DOI: 10.1103/physrevlett.95.258104] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2005] [Indexed: 05/05/2023]
Abstract
Using a computational model of a coupled reaction-diffusion-mechanics system, we find that mechanical deformation can induce automatic pacemaking activity. Pacemaking is shown to occur after a single electrical or mechanical stimulus in an otherwise nonoscillatory medium. We study the mechanisms underpinning this effect and conditions for its existence. We show that self-organized pacemakers drift throughout the medium to approach attractors with locations that depend on the size of the medium, and on the location of the initial stimulus.
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Affiliation(s)
- A V Panfilov
- Theoretical Biology, Utrecht University, Padualaan 8, Utrecht, 3584 CH, The Netherlands
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85
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Yamada Y, Sakamoto H, Ogihara S, Maeda M. Novel patterns of the gene expression regulation in the prestalk region along the antero-posterior axis during multicellular development of Dictyostelium. Gene Expr Patterns 2005; 6:63-8. [PMID: 16024295 DOI: 10.1016/j.modgep.2005.04.017] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2005] [Revised: 04/27/2005] [Accepted: 04/27/2005] [Indexed: 10/25/2022]
Abstract
Simultaneous hybridization with differentially labeled fluorescent probes for in situ hybridization analysis revealed several novel expression patterns of prestalk genes during multicellular development of Dictyostelium. Seven prestalk genes and one prespore gene (pspA) were analyzed in this study. The patterns identified here indicate that prestalk cells are more heterogeneous than previously thought. Heterogeneity was observed in peripheral prestalk tissues such as the pstAO domain of a slug and the prestalk region surrounding a stalk tube of a culminant. Heterogeneity was also observed in the core pstAB cells of the slug and immature stalk cells within the stalk tube. The upper- and lower-cups of a late culminant were also composed of several subdomains.
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Affiliation(s)
- Yoko Yamada
- Biological Science, Graduate School of Science, Osaka University, Machikaneyama 1-1, Toyonaka, Osaka 560-0043, Japan
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86
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Cadieux B, Chitramuthu BP, Baranowski D, Bennett HPJ. The zebrafish progranulin gene family and antisense transcripts. BMC Genomics 2005; 6:156. [PMID: 16277664 PMCID: PMC1310530 DOI: 10.1186/1471-2164-6-156] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2005] [Accepted: 11/08/2005] [Indexed: 11/10/2022] Open
Abstract
Background Progranulin is an epithelial tissue growth factor (also known as proepithelin, acrogranin and PC-cell-derived growth factor) that has been implicated in development, wound healing and in the progression of many cancers. The single mammalian progranulin gene encodes a glycoprotein precursor consisting of seven and one half tandemly repeated non-identical copies of the cystine-rich granulin motif. A genome-wide duplication event hypothesized to have occurred at the base of the teleost radiation predicts that mammalian progranulin may be represented by two co-orthologues in zebrafish. Results The cDNAs encoding two zebrafish granulin precursors, progranulins-A and -B, were characterized and found to contain 10 and 9 copies of the granulin motif respectively. The cDNAs and genes encoding the two forms of granulin, progranulins-1 and -2, were also cloned and sequenced. Both latter peptides were found to be encoded by precursors with a simplified architecture consisting of one and one half copies of the granulin motif. A cDNA encoding a chimeric progranulin which likely arises through the mechanism of trans-splicing between grn1 and grn2 was also characterized. A non-coding RNA gene with antisense complementarity to both grn1 and grn2 was identified which may have functional implications with respect to gene dosage, as well as in restricting the formation of the chimeric form of progranulin. Chromosomal localization of the four progranulin (grn) genes reveals syntenic conservation for grna only, suggesting that it is the true orthologue of mammalian grn. RT-PCR and whole-mount in situ hybridization analysis of zebrafish grns during development reveals that combined expression of grna and grnb, but not grn1 and grn2, recapitulate many of the expression patterns observed for the murine counterpart. This includes maternal deposition, widespread central nervous system distribution and specific localization within the epithelial compartments of various organs. Conclusion In support of the duplication-degeneration-complementation model of duplicate gene retention, partitioning of expression between grna and grnb was observed in the intermediate cell mass and yolk syncytial layer, respectively. Taken together these expression patterns suggest that the function of an ancestral grn gene has been devolved upon four paralogues in zebrafish.
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MESH Headings
- Amino Acid Motifs
- Amino Acid Sequence
- Animals
- Blotting, Northern
- Chromatography, High Pressure Liquid
- Chromosome Mapping
- Cloning, Molecular
- DNA, Complementary/metabolism
- Gene Dosage
- Gene Expression Regulation, Developmental
- Gene Library
- Humans
- In Situ Hybridization
- Intercellular Signaling Peptides and Proteins/biosynthesis
- Intercellular Signaling Peptides and Proteins/genetics
- Models, Genetic
- Molecular Sequence Data
- Multigene Family
- Oligonucleotides, Antisense/chemistry
- Oligonucleotides, Antisense/genetics
- Phylogeny
- RNA/metabolism
- RNA, Messenger/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Homology, Amino Acid
- Tissue Distribution
- Transcription, Genetic
- Zebrafish
- Zebrafish Proteins/biosynthesis
- Zebrafish Proteins/chemistry
- Zebrafish Proteins/genetics
- Zebrafish Proteins/metabolism
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Affiliation(s)
- Benoît Cadieux
- Endocrine Laboratory, Royal Victoria Hospital, McGill University Health Centre, Montreal, Quebec, Canada
- Cancer Research Institute, UCSF, 2340 Sutter Street, N-231 San Francisco, CA 94143, USA
| | - Babykumari P Chitramuthu
- Endocrine Laboratory, Royal Victoria Hospital, McGill University Health Centre, Montreal, Quebec, Canada
| | - David Baranowski
- Endocrine Laboratory, Royal Victoria Hospital, McGill University Health Centre, Montreal, Quebec, Canada
| | - Hugh PJ Bennett
- Endocrine Laboratory, Royal Victoria Hospital, McGill University Health Centre, Montreal, Quebec, Canada
- Room L2.05, Royal Victoria Hospital, 687 Pine Avenue West, Montreal, Quebec, H3A 1A1, Canada
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87
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Maier SA, Galellis JR, McDermid HE. Phylogenetic analysis reveals a novel protein family closely related to adenosine deaminase. J Mol Evol 2005; 61:776-94. [PMID: 16245011 DOI: 10.1007/s00239-005-0046-y] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2005] [Accepted: 06/16/2005] [Indexed: 11/30/2022]
Abstract
Adenosine deaminase (ADA) is a well-characterized enzyme involved in the depletion of adenosine levels. A group of proteins with similarity to ADA, the adenosine deaminase-related growth factors (ADGF; known as CECR1 in vertebrates), has been described recently in various organisms. We have determined the phylogenetic relationships of various gene products with significant amino acid similarity to ADA using parsimony and Bayesian methods, and discovered a novel paralogue, termed ADA-like (ADAL). The ADGF proteins share a novel amino acid motif, "MPKG," within which the proline and lysine residues are also conserved in the ADAL and ADA subfamilies. The significance of this new domain is unknown, but it is located just upstream of two ADA catalytic residues, of which all eight are conserved among the ADGF and ADAL proteins. This conservation suggests that ADGF and ADAL may share the same catalytic function as ADA, which has been proven for some ADGF members. These analyses also revealed that some genes previously thought to be classic ADAs are instead ADAL or ADGFs. We here define the ADGF, ADAL, ADA, adenine deaminase (ADE), and AMP deaminase (AMPD) groups as subfamilies of the adenyl-deaminase family. The availability of genomic data for the members of this family allowed us to reconstruct the intron evolution within the phylogeny and strengthen the introns-late hypothesis of the synthetic introns theory. This study shows that ADA activity is clearly more complex than once thought, perhaps involving a delicately balanced pattern of temporal and spatial expression of a number of paralogous proteins.
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Affiliation(s)
- Stephanie A Maier
- Department of Biological Sciences, University of Alberta, G508 Biological Sciences Building,, Edmonton, Alberta, T6G 2E9, Canada
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88
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Abstract
We review insights in signaling pathways controlling cell polarization and cytoskeletal organization during chemotactic movement in Dictyostelium amoebae and neutrophils. We compare and contrast these insights with our current understanding of pathways controlling chemotactic movements in more-complex multicellular developmental contexts.
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Affiliation(s)
- Markus Affolter
- Department of Cell Biology, Biozentrum University of Basel, Klingelbergstr. 70, CH-4056 Basel, Switzerland
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