Dicty News Electronic Edition Volume 23, number 1 July 09, 2004 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 Dicty-News, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. ============= Abstracts ============= A novel partner for Dictyostelium filamin is an a-helical, developmentally regulated protein Monika Knuth,*1 Nandkumar Khaire,*1 Sijie Lu,¤ Adam Kuspa,¤ Michael Schleicher,$ and Angelika A. Noegel* Journal of Cell Science, in press The filamins are a family of highly homologous actin-crosslinking proteins that stabilize three-dimensional actin networks, link them to membrane proteins and direct intracellular signaling reactions to the actin scaffold through interaction with various binding partners. Here we describe FIP, the first Dictyostelium filamin interacting protein isolated, a 229.800 Da protein with two a-helical coiled coil domains. FIP was identified in a yeast two hybrid screen using the rod domain of filamin as bait. FIP can also be coimmunoprecipitated with filamin from cellular extracts. Deletion analysis located the interaction domain of FIP to a C-terminal region, whereas in filamin rod repeats 2-4 interacted with the recombinant FIP protein. The 7 kb transcript of FIP is upregulated during early development. Monoclonal antibodies raised against a bacterially expressed FIP polypeptide recognize a 230-kDa developmentally regulated protein in western blots. Immunofluorescence analysis shows a punctate staining pattern in the cytosol and in cell fractionation experiments FIP is mainly found in the cytosolic fraction. A fusion protein composed of GFP and the C-terminal part localizes to the plasma membrane and is associated with the cytoskeleton. Expression of the fusion protein affects development and influences the size of the multicellular aggregates and the phototactic behaviour of slugs. Thus, FIP might provide a candidate link between the dynamic actin cytoskeleton and signal transduction events during the multicellular stages of Dictyostelium amoebae. Submitted by: Angelika Noegel [noegel@uni-koeln.de] ----------------------------------------------------------------------------- Control of cell-type proportioning in Dictyostelium by DIF as determined by in situ hybridization. Toshinari Maruo,1 Haruyo Sakamoto,1 Negin Iranfar,2 Danny Fuller,2 Takahiro Morio,3 Hideko Urushihara,3 Yoshimasa Tanaka3, Mineko Maeda1* and William F. Loomis,2* 1Department of Biology, Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043, 2Cell and Developmental Biology, Division of Biological Sciences, University of California San Diego, La Jolla, California 92093, USA 3Institute of Biological Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8572, Japan Eukaryotic Cell, in press We have determined the proportions of the prespore and prestalk regions in Dictyostelium slugs by in situ hybridization with a large number of prespore and prestalk specific genes. Microarrays were used to discover genes expressed in a cell type specific manner. Fifty-four prespore specific genes were verified by in situ hybridization including 18 that had been previously shown to be cell type specific. The 36 new genes more than doubles the number of available prespore markers. At the slug stage the prespore genes hybridized to cells uniformly in the posterior 80% of wild -type slugs but hybridized to the posterior 90% of slugs lacking the secreted alkylphenone DIF-1. There was a compensatory two-fold decrease in prestalk cells in DIF-less slugs. Removal of prespore cells resulted in cell type conversion in both wild-type and DIF-less anterior fragments. Thus, DIF-1 appears to act in concert with other processes to establish cell-type proportions. Submitted by: Bill Loomis [wloomis@ucsd.edu] ============================================================================== [End Dicty News, volume 23, number 1]