Dicty News Electronic Edition Volume 17, number 4 Sept. 1, 2001 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu. Back issues of Dicty-News, the Dicty Reference database and other useful information is available at DictyBase--http://dictybase.org. ============== Abstracts ============== Cofilin-2, a novel type of cofilin, is expressed specifically at aggregation stage of Dictyostelium discoideum development. Hiroyuki Aizawa1*, Yoshiro Kishi2, Kazuko Iida1, Masazumi Sameshima2, and Ichiro Yahara1. 1Department of Cell Biology, 2Electron Microscopy Center, The Tokyo Metropolitan Institute of Medical Science, Honkomagome 3-18-22, Bunkyo-ku, Tokyo 113-8613, Japan. *Present address: Department of Neuroscience, Johns Hopkins University School of Medicine, 725 North Wolfe Street, PCTB 1004, Baltimore, MD 21205, USA Genes to Cells in press. Abstract Background: A conventional cofilin, cofilin-1 in Dictyostelium discoideum plays significant roles in cell proliferation, phagocytosis, chemotactic movement and macropinocytosis. Results: We identified a new member of the cofilin family, named cofilin -2 in D. discoideum. Cofilin-2 shows significant homology to a conventional Dictyostelium cofilin, cofilin-1, through its entire sequence, and contains residues conserved among the cofilin family that are responsible for actin- binding. On the other hand, several residues that are conserved among the cofilin family are missing from cofilin-2. Purified cofilin-2 depolymerized actin filaments in a dose- and pH-dependent manner and reduced the apparent viscosity of an actin solution, although they did not co-sediment with actin filaments at all. Cofilin-2 was not expressed in vegetative cells, but was transiently induced during the aggregation stage of development, whereas cofilin-1 was predominantly expressed in vegetative cells. Immunocytochemistry revealed that cofilin-2 localizes at substrate adhesion sites, where cofilin-1 is almost completely excluded. Disruption of the cofilin-2 gene caused an increase in actin accumulation at the substrate adhesion sites. We also found that cofilin-2 did not rescue cof1 gene null yeast cells, whereas cofilin-1 did. Conclusions: Cofilin-2 may play a distinct role from that of cofilin-1 in destabilization of the actin cytoskeleton during Dictyostelium development. ----------------------------------------------------------------------------- Propagating chemo-attractant waves co-ordinate periodic cell movement in Dictyostelium slugs Dirk Dormann & Cornelis J. Weijer School of Life Sciences, Division of Cell and Developmental Biology, Wellcome Trust Biocentre, University of Dundee, Dundee DD1 5EH, UK ABSTRACT Migration and behaviour of Dictyostelium slugs results from co-ordinated movement of its constituent cells. It has been proposed that cell movement is controlled by propagating waves of cAMP as during aggregation and in the mound. We report here the existence of optical density waves in slugs, they are initiated in the tip and propagate backwards. The waves reflect periodic cell movement and are mediated by cAMP since injection of cAMP or cAMP phosphodiesterase disrupts wave propagation and results in effects on cell movement and therefore slug migration. Inhibiting the function of the cAMP receptor cAR1 blocks wave propagation, showing that the signal is mediated by cAR1. Wave initiation is strictly dependent on the tip, in decapitated slugs no new waves are initiated and slug movement stops until a new tip regenerates. Isolated tips continue to migrate while producing waves. We conclude from these observations that the tip acts as a pacemaker for cAMP waves that coordinate cell movement in slugs. ----------------------------------------------------------------------------- Extracting transcriptional events from temporal gene expression patterns during Dictyostelium development. R. Sasik, N. Iranfar*, T. Hwa, and W.F. Loomis* Department of Physics and *Division of Biology University of California San Diego, La Jolla, CA 92093 Bioinformatics, in press DNA microarray technology can generate a large amount of data describing time-course of gene expression. These data, when properly interpreted, can yield a great deal of information concerning differential gene expression during development. Much current effort in bioinformatics has been devoted to the analysis of gene expression data, usually via some "clustering analysis" on the raw data in some abstract high dimensional space. Here, we describe a method where we first "process" the raw time-course data using a simple biologically based kinetic model of gene expression profile e.g., the times of the onset and cessation of the expression of the developmentally regulated genes. These vital attributes can then be trivally clustered by visual inspection to reveal biologically significant effects. We have applied this approach to microarray expression data from samples isloated every two hours throughout the 24-hour developmental program of Dictyostelium discoideum. mRNA accumulation patterns for 50 developmental genes were found to fit the kinetic model with a p-value of 0.05 or better. Transcription of these genes appears to be initiated in bursts at well-defined periods during development, in a manner suggestive of a dependent sequence. This approach can be applied to analyses of other temporal expression patterns, including those of the cell cycle. Intensity ratios for all genes in this study are available at http://www.biology.ucsd.edu/loomis-cgi/microarray/ index.html ----------------------------------------------------------------------------- [End Dicty News, volume 17, number 4]