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Eukaryotic Cell Feb 2011Much remains to be understood about how a group of cells break symmetry and differentiate into distinct cell types. The simple eukaryote Dictyostelium discoideum is an... (Review)
Review
Much remains to be understood about how a group of cells break symmetry and differentiate into distinct cell types. The simple eukaryote Dictyostelium discoideum is an excellent model system for studying questions such as cell type differentiation. Dictyostelium cells grow as single cells. When the cells starve, they aggregate to develop into a multicellular structure with only two main cell types: spore and stalk. There has been a longstanding controversy as to how a cell makes the initial choice of becoming a spore or stalk cell. In this review, we describe how the controversy arose and how a consensus developed around a model in which initial cell type choice in Dictyostelium is dependent on the cell cycle phase that a cell happens to be in at the time that it starves.
Topics: Animals; Cell Cycle; Cell Differentiation; Dictyostelium; Gene Expression Profiling; Neutral Red; Spores, Protozoan; Staining and Labeling; Starvation
PubMed: 21148754
DOI: 10.1128/EC.00219-10 -
Current Opinion in Genetics &... Oct 1994Dictyostelium development is orchestrated by diffusible signals. Progress has been made in understanding how cAMP signaling triggers post-aggregative development and in... (Review)
Review
Dictyostelium development is orchestrated by diffusible signals. Progress has been made in understanding how cAMP signaling triggers post-aggregative development and in defining the number of cell types that eventually differentiate. Ammonia is an unusual signal that may act by alkalinizing acidic vesicles. A chlorinated signal, differentiation-inducing factor (DIF), may be universal amongst the slime moulds. The first genes have been cloned using restriction enzyme mediated integration (REMI) insertional mutagenesis; one encodes a novel cytosolic protein essential for activation of adenylyl cyclase.
Topics: Animals; Cell Differentiation; Cyclic AMP; Dictyostelium; Genes, Fungal; Genes, Protozoan; Mutagenesis; Signal Transduction
PubMed: 7849501
DOI: 10.1016/0959-437x(94)90128-p -
Development (Cambridge, England) Feb 2011Dictyostelium discoideum belongs to a group of multicellular life forms that can also exist for long periods as single cells. This ability to shift between uni- and... (Review)
Review
Dictyostelium discoideum belongs to a group of multicellular life forms that can also exist for long periods as single cells. This ability to shift between uni- and multicellularity makes the group ideal for studying the genetic changes that occurred at the crossroads between uni- and multicellular life. In this Primer, I discuss the mechanisms that control multicellular development in Dictyostelium discoideum and reconstruct how some of these mechanisms evolved from a stress response in the unicellular ancestor.
Topics: Biological Evolution; Developmental Biology; Dictyostelium; Models, Biological; Phylogeny
PubMed: 21205784
DOI: 10.1242/dev.048934 -
Autophagy Aug 2010The use of simple organisms to understand the molecular and cellular function of complex processes is instrumental for the rapid development of biomedical research. A... (Review)
Review
The use of simple organisms to understand the molecular and cellular function of complex processes is instrumental for the rapid development of biomedical research. A remarkable example has been the discovery in S. cerevisiae of a group of proteins involved in the pathways of autophagy. Orthologues of these proteins have been identified in humans and experimental model organisms. Interestingly, some mammalian autophagy proteins do not seem to have homologues in yeast but are present in Dictyostelium, a social amoeba with two distinctive life phases, a unicellular stage in nutrient-rich conditions that differentiates upon starvation into a multicellular stage that depends on autophagy. This review focuses on the identification and annotation of the putative Dictyostelium autophagy genes and on the role of autophagy in development, cell death and infection by bacterial pathogens.
Topics: Animals; Autophagy; Cell Death; Dictyostelium; Evolution, Molecular; Genes, Protozoan; Models, Biological; Signal Transduction
PubMed: 20603609
DOI: 10.4161/auto.6.6.12513 -
Advances in Experimental Medicine and... 2008For many years it has been known that developing cells of Dictyostelium discoideum show periodic surges as they aggregate. When it was discovered that the cells were... (Review)
Review
For many years it has been known that developing cells of Dictyostelium discoideum show periodic surges as they aggregate. When it was discovered that the cells were responding chemotactically to cAMP gradients produced within the populations, experiments were carried out that demonstrated similar periodic changes in the concentration of extracellular cAMP. Moreover, homogenous populations of developed cells held in suspension could be shown to respond to cAMP by changes in cell shape. Such suspensions showed spontaneous oscillations in light scattering as well as cAMP levels as the result of entrainment of the cells. The molecular components necessary for the pulsatile release of cAMP were uncovered by analyzing the behavior of a large number of strains with defined mutations isolated from saturation mutagenic screens. Subsequent genetic and biochemical studies established the connections between a dozen proteins essential for spontaneous oscillations. Computer simulations of a molecular circuit based on these results showed that it is able to account for the temporal and quantitative aspects of the oscillatory system. The circuit also appears to be coupled to the construction and dismantling of the actin/myosin cortical layer that ensures that pseudopods are restricted to the anterior of cells during chemotaxis and that the cells do not back-track when the natural wave is behind them. Since the same molecular clock controls both signal production and signal response, these behaviors are always kept strictly in phase.
Topics: Animals; Biological Clocks; Cyclic AMP; Dictyostelium; Models, Biological; Movement; Mutation
PubMed: 18783170
DOI: 10.1007/978-0-387-09794-7_3 -
Methods in Molecular Biology (Clifton,... 2009Dictyostelium slugs are able to respond to environmental stimuli in an extremely sensitive and efficient way. This enables a slug to migrate to more favourable locations...
Dictyostelium slugs are able to respond to environmental stimuli in an extremely sensitive and efficient way. This enables a slug to migrate to more favourable locations for formation of fruiting bodies and dispersal of spores. Phototaxis is a readily assayed phenotype and reflects the interactions of environmental stimuli with morphogenetic signalling systems controlling the movement of the slug. The methods for assaying phototaxis are described here. Qualitative phototaxis tests are described and can be used for rapid screening of potential mutants or effects of pharmacological agents. These tests are simple to conduct yet care must be taken in order to avoid the effects of high cell density which can be misleading when interpreting results. Quantitative phototaxis tests can be performed with known cell densities of amoebae which ensures that any effects seen are caused by the mutation or pharmacological agent and not simply due to differences in cell densities.
Topics: Animals; Dictyostelium; Light; Locomotion; Protozoan Proteins
PubMed: 19763959
DOI: 10.1007/978-1-60761-198-1_4 -
Developmental Genetics 1988Cellular slime mold amoebae have become a model system for the study of cell motility and the cytoskeleton. A basic problem which all cells face that involves the... (Review)
Review
Cellular slime mold amoebae have become a model system for the study of cell motility and the cytoskeleton. A basic problem which all cells face that involves the cytoskeleton is how to control their size. The varied ways in which cellular slime mold amoebae change their cell size--by changing the size at which division occurs, by cell fusion, and by control over cytokinesis--are reviewed. A model is presented which attempts to explain how the mechanisms affected in certain cytokinesis mutants in Dictyostelium discoideum known as phg mutants could be involved in control of cell size in the predatory slime mold Dictyostelium caveatum.
Topics: Cell Cycle; Cell Fusion; Cell Movement; Dictyostelium; Models, Biological; Mutation
PubMed: 3072136
DOI: 10.1002/dvg.1020090443 -
Basic Life Sciences 1975
Review
Topics: DNA Repair; Dictyostelium; Mutation; Myxomycetes; Radiation Effects; Ultraviolet Rays
PubMed: 1103874
DOI: 10.1007/978-1-4684-2898-8_24 -
International Review of Cytology 2005In general, growth and differentiation are mutually exclusive, but they are cooperatively regulated during the course of development. Thus, the process of a cell's... (Review)
Review
In general, growth and differentiation are mutually exclusive, but they are cooperatively regulated during the course of development. Thus, the process of a cell's transition from growth to differentiation is of general importance not only for the development of organisms but also for the initiation of malignant transformation, in which this process is reversed. The cellular slime mold Dictyostelium, a wonderful model organism, grows and multiplies as long as nutrients are supplied, and its differentiation is triggered by starvation. A strict checkpoint (growth/differentiation transition or GDT point), from which cells start differentiating in response to starvation, has been specified in the cell cycle of D. discoideum Ax-2 cells. Accordingly, integration of GDT point-specific events with starvation-induced events is needed to understand the mechanism regulating GDTs. A variety of intercellular and intracellular signals are involved positively or negatively in the initiation of differentiation, making a series of cross-talks. As was expected from the presence of GDT points, the cell's positioning in cell masses and subsequent cell-type choices occur depending on the cell's phase in the cell cycle at the onset of starvation. Since novel and somewhat unexpected multiple functions of mitochondria in cell movement, differentiation, and pattern formation have been well realized in Dictyostelium cells, they are reviewed in this article.
Topics: Animals; Cell Cycle; Cell Proliferation; Dictyostelium; Mitochondria; Models, Animal; Models, Biological; Signal Transduction
PubMed: 16157183
DOI: 10.1016/S0074-7696(05)44007-3 -
Journal of Cell Science Dec 2001The development of the non-metazoan eukaryote Dictyostelium discoideum displays many of the features of animal embryogenesis, including regulated cell-cell adhesion.... (Review)
Review
The development of the non-metazoan eukaryote Dictyostelium discoideum displays many of the features of animal embryogenesis, including regulated cell-cell adhesion. During early development, two proteins, DdCAD-1 and csA, mediate cell-cell adhesion between amoebae as they form a loosely packed multicellular mass. The mechanism governing this process is similar to epithelial sheet sealing in animals. Although cell differentiation can occur in the absence of cell contact, regulated cell-cell adhesion is an important component of Dictyostelium morphogenesis, and a third adhesion molecule, gp150, is required for multicellular development past the aggregation stage. Cell-cell junctions that appear to be adherens junctions form during the late stages of Dictyostelium development. Although they are not essential to establish the basic multicellular body plan, these junctions are required to maintain the structural integrity of the fruiting body. The Dictyostelium beta-catenin homologue Aardvark (Aar) is present in adherens junctions, which are lost in its absence. As in the case of its metazoan counterparts, Aar also has a function in cell signalling and regulates expression of the pre-spore gene psA. It is becoming clear that cell-cell adhesion is an integral part of Dictyostelium development. As in animals, cell adhesion molecules have a mechanical function and may also interact with the signal-transduction processes governing morphogenesis.
Topics: Animals; Cell Adhesion; Cell Communication; Dictyostelium; Signal Transduction
PubMed: 11792801
DOI: 10.1242/jcs.114.24.4349