dictyNews Electronic Edition Volume 39, number 16 May 31, 2013 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase ========= Abstracts ========= Aberrant spindle dynamics and cytokinesis in Dictyostelium discoideum cells that lack glycogen synthase kinase 3 Adrian J. Harwood, Josephine E. Forde-Thomas, Hazel Williams, Matthias Samereier and Annette Mueller-Taubenberger European Journal of Cell Biology, in press Eukaryotic cell division requires the co-ordinated assembly and disassembly of the mitotic spindle, accurate chromosome segregation and temporal control of cytokinesis to generate two daughter cells. While the absolute details of these processes differ between organisms, there are evolutionarily conserved core components common to all eukaryotic cells, whose identification will reveal the key processes that control cell division. Glycogen synthase kinase 3 (GSK-3) is a major protein kinase found throughout the eukaryotes and regulates many processes, including cell differentiation, growth, motility and apoptosis. In animals, GSK-3 associates with mitotic spindles and its inhibition causes mis-regulation of chromosome segregation. Two suppressor screens in yeast point to a more general effect of GSK-3 on cell division, however the direct role of GSK-3 in control of mitosis has not been explored outside the animal kingdom. Here we report that the Dictyostelium discoideum GSK-3 orthologue, GskA, associates with the mitotic spindle during cell division, as seen for its mammalian counterparts. Dictyostelium possesses only a single GSK-3 gene that can be deleted to eliminate all GSK-3 activity. We found that gskA-null mutants failed to elongate their mitotic spindle and were unable to divide in shaking culture, but have no chromosome segregation defect. These results suggest further conservation for the role of GSK-3 in the regulation of spindle dynamics during mitosis, but also reveal differences in the mechanisms ensuring accurate chromosome segregation. Submitted by Adrian Harwood [harwoodaj@cf.ac.uk] --------------------------------------------------------------------------- The use of streptavidin conjugates as immunoblot loading controls & mitochondrial markers for use with Dictyostelium discoideum Andrew J. Davidson*, Jason S. King*1 and Robert H. Insall Beatson Institute for Cancer Research, Garscube Estate, Bearsden, Glasgow, UK. G61 1BD *These authors contributed equally to this work 1Corresponding author BioTechniques, in press The loading controls used from quantitative immunoblotting in mammalian cells are not appropriate for use with Dictyostelium discoideum. Actin, for example changes greatly during development, and other antibodies are not commercially available. Here we demonstrate the use of labeled streptavidin to detect the biotinylated, mitochondrial MCCC1, providing a robust and convenient tool for the quantitative normalization of Dictyostelium western blots as well as labeling mitochondria in fixed cells. Submitted by Jason King [j.king@beatson.gla.ac.uk] --------------------------------------------------------------------------- Dictyostelids: Evolution, genomics and cell biology Editors: Maria Romeralo, Sandra Baldauf, Ricardo Escalante Soon available at: http://www.springer.com/life+sciences/evolutionary+%26+developmental+biology/book/978-3-642-38486-8 Chapter 1. Dictyostelium discoideum as a model in biomedical research Sandra Munoz-Braceras, Ana Mesquita and Ricardo Escalante The simple eukaryote Dictyostelium discoideum has been traditionally used to understand basic principles of cell and developmental biology and now has also become a useful system in biomedical research. What are the similarities and differences between D. discoideum and other simple microbial models such as Saccharomyces cerevisiae? Which aspects are more advantageous to address in D. discoideum? Are there any processes or specific proteins present in D. discoideum that are difficult or impossible to study in other systems? Does it make sense to use such a simple organism in biomedicine? These and other questions will be addressed in this chapter, together with some specific examples in which D. discoideum has proved its potential to model human disease. Chapter 2. Genome analysis of social amoebae Gernot Gloeckner Genomics is now an indispensible part of the biological sciences. Today a species description without genome information is incomplete. This chapter describes the current knowledge on the genome of the model species D. discoideum. A comparison with other social amoebae genomes covering the whole breadth of this branch of evolution carves out driving forces of speciation and the common toolkit of all social amoebae. The vast evolutionary distance within this branch makes ortholog detection difficult. While the coding capacity of all social amoebae is largely conserved, species specific gene family expansions of proteins for environmental sensing, signaling, and secondary metabolites provide for diversification. The sequences of the functional chromosomal elements (telomeres and centromeres) are not conserved, rather they seem to have underwent severe modifications. Nucleosome patterns link the social amoebae to other, more sophisti-cated multicellular systems. Comparative curated databases make this wealth of genome information accessible and play an important role for the dissemination of the knowledge on this evolutionary branch. Chapter 3. Signalling during Dictyostelium development Cornelis J Weijer Dictyostelium has become an important model system to study the molecular details of the signalling pathways controlling gradient sensing and cell polarisation that control localised activation of the actin myosin cytoskeleton responsible for evolutionary highly conserved mechanisms of chemotactic cell movement up chemo- attractant gradients. 3'-5' cyclic AMP is the chemo-attractant that controls the chemotactic cell movements that result in aggregation of up to several hundred thousand cells, slug formation, migration and fruiting body formation. The coordination of these complex cell movements require long range cAMP mediated cell-cell signalling based on periodic initiation of cAMP signals in the aggregation centre and slug tip and relay by surrounding cells, resulting in highly dynamic patterns of cAMP wave propagation. Model calculations have shown that the dynamic feedbacks between autocatalytic cell-cell cAMP signalling and cAMP mediated collective chemotactic cell movement result in emergent properties that readily explain multi cellular morphogenesis. cAMP signalling not only controls cell movement but also acts as a key morphogen to control cell differentiation, which in turn affects celltype specific cell-cell signalling and cell movement, adding an additional layer of feedback. To fully understand the multicellular morphogenesis of this organism at the level of cell behaviours it will be needed to integrate the detailed celltype proportioning mechanisms in models describing cell-cell signalling and movement. Dictyostelium is likely to be the first eukaryotic organism where it will be possible to quantitatively understand how multicellular development and morphogenesis arise as emergent properties from a few relatively simple collective cell behaviours. Chapter 4. The chemotactic compass Dawit Jowhar and Chris Janetopoulos Cells have an amazing ability to sense very shallow gradients of chemoattractants and move directionally. This fundamental process is critical for development and numerous disease states. Dictyostelium has emerged as one of the best understood model systems for elucidating the complex signaling pathways that drive chemotaxis. This review focuses on the signaling mechanisms regulating directed migration and discusses the role of polarity and development on our current understanding of this process. We highlight new findings using a second chemoattractant, folic acid and suggest that this chemical cue should be used when a developmental defect is suspected. We also speculate on recent studies, which suggest that researchers should use our new understanding of the temporal and spatial relationships of signaling and cytoskeletal proteins to guide future experiments. Chapter 5. Transcriptional Regulators - Dynamic Drivers of Multicellular Formation, Cell Differentiation and Development Rafael Rosengarten, Balaji Santhanam, and Mariko Katoh-Kurasawa In this chapter we examine what is known about the roles of individual transcription regulators in mediating development in Dictyostelium discoideum. We present a broad review of the field, covering genetic, biochemical, molecular and bioinformatic experiments that illuminate transcriptional regulation in the context of developmental events. We highlight evidence for evolutionary conservation where it exists, and have sought to underscore the power of RNA sequencing as a tool for comparative studies and global analysis. We believe that as next generation 'omics approaches are more widely applied, we may paint a more complete picture of the gene regulatory networks governing dictyostelid development, and gain insight into general evolutionary processes that shape developmental biology. Chapter 6. Non-coding RNAs in Dictyostelium discoideum and other dictyostelid social amoebae Lotta Avesson, Andrea Hinas, and Fredrik Soederbom Non-coding (nc)RNAs have recently emerged as ubiquitous and important regulators of a multitude of different processes, such as stress response, cell differentiation, infection, and cell death. The means by which ncRNAs affect these processes are numerous and diverse, ranging from protein localization to regulation of gene expression. ncRNA-mediated gene expression control has been the subject of especially intense study in recent years and shown to occur through several mechanisms. Different ncRNAs can regulate gene expression transcriptionally by inducing modification of DNA or chromatin, or post-transcriptionally by directing cleavage, degradation, or translational inhibition of messenger (m)RNAs. ncRNAs come in a broad spectrum of sizes, from ~20 nucleotides (nt) to several thousand nt, and function in complexes with various proteins that usually exert a catalytic function while the RNAs act as guides. In Dictyostelia, we have only started to understand the extent of ncRNA regulation, mostly from studies in Dictyostelium discoideum, which is the focus of this chapter. Chapter 7. Sex in Dictyostelia Gareth Bloomfield Dictyostelid social amoebae possess both sexual and parasexual cycles. In the former, diploid zygotes attract surrounding haploids and then cannibalise them, forming large immobile structures known as macrocysts. In the parasexual cycle, amoebae of the same sex fuse to form diploids that can continue to grow and multiply. Species with more than two sexes (or mating types) are not unusual among dictyostelia, and recently the genetic basis for sex determination was described in the model species Dictyostelium discodeum. Macrocysts have so far only been observed in a minority of the known species, and their ecological context and significance is still not understood. Important questions regarding altruism, genetics, and the basic cell biology of both the sexual and parasexual cycles remain to be addressed experimentally, so there remains tremendous scope for future research. Chapter 8. A global overview of Dictyostelid Ecology with special emphasis in North American forest James C. Cavender Development in 1965 of a quantitative method for dictyostelid isolation from soil samples, made possible ecological studies based on frequency and density of occurrence. Information has subsequently been obtained on a number of aspects of dictyostelid ecology. I discuss some of them along this chapter, especially those aspects studied after Raper's publication in 1984 of his famous book 'The Dictyostelids'. These include dispersal, relative abundance, optimum conditions for maximum diversity, comparison of temperate and tropical populations, ecological individuality of species (especially Dictyostelium discoideum), possible decline in species numbers and global distribution of Dictyostelia. Chapter 9. Evolution of Dictyostelid Social Amoebas inferred from the use of molecular tools Maria Romeralo and Omar Fiz. Dictyostelid social amoebas are eukaryotic microbes distributed all around the globe. As with many other protist groups, one fundamental and revolutionary event in the study of dictyostelid (Amoebozoa) systematics has been the use of molecular tools. This has radically changed our understanding of evolution across the group and has greatly expanded the potential use of dictyostelids as model organisms for a wide range of areas including biomedicine, development, evolutionary biology and molecular ecology. This is further supported by genome sequencing that has been carried out for at least one species in each of the major groups. Phylogenomic data is also essential to pinpointing the origin of diversification of dictyostelids in terrestrial ecosystems, which is basic for understanding the evolutionary history across eukaryotic amoeboid lineages. Chapter 10. The Evolution of the Cellular Slime Molds John Tyler Bonner The cellular slime molds have existed for a very long time; they have an ancient history. It is surprising that the early morphological species have not been supplanted and gone extinct, as is the case for larger organisms; a sizable number of ancient cellular slime molds still exist today - they are living fossils. This unusual phenomenon can be explained if one assumes that their morphology is only weakly affected by natural selection leading to a modest variation of morphology among the different species. I argue that the reason for their apparent relative immunity to the effects of natural selection can be explained by their small size; this is a general rule among all microorganisms. Chapter 11. Social selection in the cellular slime moulds Vidyanand Nanjundiah and Santosh Sathe Starvation triggers a complex series of intercellular interactions in the cellular slime mould amoebae. As a result the amoebae aggregate, form a coherent multicellular structure with division of labour and, eventually, differentiate into a fruiting body made up of a stalk and a spore mass. Whether an amoeba dies and forms part of the stalk or becomes a stress-resistant spore depends both on pre-existing biases and on post-starvation signalling between amoebae. Mutual communication permits one amoeba to influence the phenotype, and therefore affect the fitness, of another. The implication is that social selection has been a major factor in the evolution of cooperative behaviour in these amoebae. Chapter 12. The non-dictyostelid sorocarpic amoebae Matthew W. Brown, Jeffrey D. Silberman The social life cycle made famous through research on the dictyostelids is not an evolutionary innovation that is solely unique to the dictyostelids. Since 1873 other protistans with a similar life styles have been recognized. Historically, they have been allied under various taxonomic classifications over the last 140 years; however, the recent influx of molecular data has proven that analogous methods through a social means to form a spore dispersal structure have independently arose in seven different lineages of eukaryotic organisms. Here we provide a brief introduction to each of the amoeboid organisms that display this behavior focusing on their life histories and the history of the research on each taxon. These organisms represent one of the most striking examples of ultimate convergent evolution across the greatest possible evolutionary distances in eukaryotic evolution. Research into the molecular and developmental biology that underlies the evolution of a social life cycle and formation of a fruiting body is still in its infancy when compared to the dictyostelids. However, the genomes from several non- dictyostelid sorocarpic amoebae are soon becoming available, and a new age of research into these fascinating organisms is beginning to gain traction. Submitted by Ricardo Escalante [rescalante@iib.uam.es] ============================================================== [End dictyNews, volume 39, number 16]