dictyNews Electronic Edition Volume 36, number 4 Feb 4, 2011 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 ========= A simple mechanism for complex social behaviour Katie Parkinson1*, Neil J. Buttery1*, Jason B. Wolf2  and Christopher R.L. Thompson1  1 Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Rd, Manchester, M13 9PT, UK 2 Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK   Corresponding authors * These authors contributed equally to this work PLoS Biology, in press The evolution of cooperation is a paradox because natural selection should favour exploitative individuals that avoid paying their fair share of any costs. Such conflict between the self-interests of cooperating individuals often results in the evolution of complex, opponent specific, social strategies and counter strategies. However, the genetic and biological mechanisms underlying complex social strategies, and therefore the evolution of cooperative behaviour, are largely unknown. To address this dearth of empirical data, we combine mathematical modeling, molecular genetic and developmental approaches to test whether variation in the production of and response to social signals is sufficient to generate the complex partner specific social success seen in the social amoeba Dictyostelium discoideum. Firstly, we find that the simple model of production of and response to social signals can generate the sort of apparent complex changes in social behaviour seen in this system, without the need for partner recognition. Secondly, measurements of signal production and response in a mutant with a change in a single gene that leads to a shift in social behaviour provide support for this model. Finally, these simple measurements of social signalling can also explain complex patterns of variation in social behaviour generated by the natural genetic diversity found in isolates collected from the wild. Our studies therefore demonstrate a novel and elegantly simple underlying mechanistic basis for natural variation in complex social strategies in D. discoideum. More generally, they suggest that simple rules governing interactions between individuals can be sufficient to generate a diverse array of outcomes that appear complex and unpredictable when those rules are unknown. Submitted by Chris Thompson [christopher.thompson@manchester.ac.uk] -------------------------------------------------------------------------------- Cell type specific filamin complex regulation by a novel class of HECT ubiquitin ligase is required for normal cell motility and patterning Simone L. Blagg1, Suzanne Battom1, Sarah J. Annesley2, Thomas Keller1, Katie Parkinson1, Mei-FangWu1, Paul R. Fisher2 and Christopher R. L. Thompson1* 1 Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester M13 9PT, UK 2 Department of Microbiology, La Trobe University, VIC 3086, Australia * Corresponding Author Development, in press Differential cell motility plays a key role in many developmental processes. This is perhaps most evident in examples of pattern formation in which the different cell types arise intermingled before sorting out into discrete tissues. In this, heterogeneities in responsiveness to differentiation inducing signals are thought to result in the activation of cell type specific genes and Ôsalt and pepperÕ patterning. However, how differential gene expression results in cell sorting is poorly defined. Here we describe a novel gene (hfnA) that provides the first mechanistic link between cell signalling, differential gene expression and cell type specific sorting in Dictyostelium. HfnA defines a novel group of evolutionarily conserved HECT ubiquitin ligases with a Filamin domain towards the N-terminus (HFNs). HfnA expression is induced by the stalk differentiation inducing factor DIF-1 and is restricted to a subset of prestalk cells (pstO). In a HfnA- mutant, pstO cells differentiate but their sorting out is delayed. Genetic interactions suggest this is due to misregulation of filamin complex activity. Over-expression of filamin complex members phenocopies the HfnA- pstO cell sorting defect, whereas disruption of filamin complex function in a wild type background results in pstO cells sorting more strongly. Furthermore, filamin disruption in an HfnA- background effectively rescues pstO cell localization. Finally HfnA- cells also exhibit altered slug phototaxis phenotypes that are consistent with filamin complex hyperactivity. We therefore propose that HfnA regulates filamin complex activity and cell type specific motility, through the breakdown of filamin complexes. These findings provide a novel mechanism for filamin regulation, and demonstrate that filamin is a crucial mechanistic link between responses to differentiation signals and cell movement in patterning based on Ôsalt and pepperÕ differentiation and sorting out. Submitted by Chris Thompson [christopher.thompson@manchester.ac.uk] -------------------------------------------------------------------------------- Non-genetic heterogeneity and cell fate choice in D. discoideum Alex Chattwood and Christopher R.L. Thompson* Faculty of Life Sciences, University of Manchester, Michael Smith Building, Oxford Rd, Manchester, M13 9PT *Corresponding author Development, Growth and Differentiation, in press From microbes to metazoans, it is now clear that fluctuations in the abundance of mRNA transcripts and protein molecules enable genetically identical cells to oscillate between several distinct states (Kaern et al., 2005). Since this cell-cell variability does not derive from physical differences in the genetic code it is termed non-genetic heterogeneity. Non-genetic heterogeneity endows cell populations with useful capabilities they could never achieve if each cell were the same as its neighbours (Eldar and Elowitz, 2010; Raj and van Oudenaarden, 2008). One such example is seen during multicellular development and Ôsalt and pepperÕ cell type differentiation. In this review, we will firstly examine the importance of non-genetic heterogeneity in initiating Ôsalt and pepperÕ pattern formation during Dictyostelium discoideum development. Secondly, we will discuss the various ways in which non-genetic heterogeneity might be generated, as well as recent advances in understanding the molecular basis of heterogeneity in this system. Submitted by Chris Thompson [christopher.thompson@manchester.ac.uk] -------------------------------------------------------------------------------- Nucleolar localization and identification of nuclear/nucleolar localization signals of the calmodulin-binding protein nucleomorphin during growth and mitosis in Dictyostelium Andrew Catalano (1) and Danton H. OÕDay (2) (1) Department of Cell & Systems Biology, 25 Harbord Street, University of Toronto, Toronto, ON, Canada M5S 3G5 (2) Department of Biology, University of Toronto at Mississauga, 3359 Mississauga Road , Mississauga, ON, Canada L5L 1C6 Histochemistry and Cell Biology in press The calmodulin-binding protein nucleomorphin isoform NumA1 is a nuclear number regulator in Dictyostelium that localizes to intra-nuclear patches adjacent to the nuclear envelope and to a lesser extent the nucleoplasm. Earlier studies have shown similar patches to be nucleoli but only three nucleolar proteins have been identified in Dictyostelium. Here, actinomycin-D treatment caused the loss of NumA1 localization while calcium and calmodulin antagonists had no effect. In keeping with a nucleolar function, NumA1 moved out of the presumptive nucleoli during mitosis redistributing to areas within the nucleus, the spindle fibers, and centrosomal region before re-accumulating in the presumptive nucleoli at telophase. Together these data verify NumA1 as a true nucleolar protein. Prior to this study the dynamics of specific nucleolar proteins had not been determined during mitosis in Dictyostelium. FITC- conjugated peptides equivalent to presumptive nuclear localization signals within NumA1 localized to nucleoli indicating that they also act as nucleolar localization signals. To our knowledge these represent the firstprecisely-defined nucleolar localization signals as well as the first nuclear/nucleolar localization signals identified in Dictyostelium. Together, these results reveal that NumA1 is a true nucleolar protein and the only nucleolar calmodulin-binding protein identified in Dictyostelium. Possible use of nuclear/nucleolar localization signal-mediated drug targeting to nucleoli is discussed. Submitted by Danton H. OÕDay [danton.oday@utoronto.ca] -------------------------------------------------------------------------------- Efficient generation of gene knockout plasmids for Dictyostelium discoideum using one-step cloning Stephan Wiegand, Janis Kruse, Sina Gronemann & Christian Hammann Genomics, in press The amoeba Dictyostelium discoideum is a well-established model organism for studying numerous aspects of cellular and developmental functions. Its rather small (~34 Mb) chromosomal genome and the high efficiency of gene disruption by homologous recombination have enabled researchers to dissect various specific gene functions. We describe here the use of one-step cloning for the fast and efficient generation of deletion vectors that are produced in a one-step reaction by inserting two PCR products into an organism-specific, generic acceptor system. This worked efficiently for all 16 tested constructs directed against genes in the amoeba Dictyostelium discoideum. Saving cost and time, the used protocol represents a significant advancement in the generation of such plasmids compared to the conventionally applied restriction enzyme/ligation approach. Using appropriate selection markers, similar systems could also be useful in other organisms, where genes can be knocked out by homologous recombination. Submitted by Christian Hammann [hammann@bio.tu-darmstadt.de] -------------------------------------------------------------------------------- Actin Switches in Phagocytosis GŸnther Gerisch Max-Planck-Institut fŸr Biochemie, 82152 Martinsried, Germany Communicative & Integrative Biology, in press Exposure of phagocytes to non-spherical particles has provided evidence for multiple actions of the actin system in force generation. For the uptake of long cylindrical particles, a Òmotile actin clampÓ mechanism is proposed. When a phagocyte is engaged with an hourglass-shaped particle, it exerts contractile activity alternatively at the far end of the particle or at its concave region. Phagocytes can switch within seconds between these different strategies of taking up a particle. This response switching is based on reprogramming the pattern of actin polymerization and depolymerization. The choice between different strategies of interaction with a particle increases the probability of engulfing the entire particle or at least a portion of it. Finally, a switch to actin disassembly enables a phagocyte to release a particle that turns out to be too big to be enclosed. Submitted by: GŸnther Gerisch gerisch@biochem.mpg.de] ============================================================== [End dictyNews, volume 36, number 4]