dictyNews Electronic Edition Volume 40, number 26 October 24, 2014 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 ========= The thyroxine inactivating gene, type III deiodinase, suppresses multiple signaling centers in Dictyostelium discoideum Shashi Prakash Singh1, Ranjani Dhakshinamoorthy1, Pundrik Jaiswal1#, Stefanie Schmidt2, Sascha Thewes2, and Ramamurthy Baskar1* Affiliations: 1Department of Biotechnology, Bhupat and Jyoti Mehta School of Biosciences, Indian Institute of Technology-Madras, Chennai-600036, India. 2Institute for Biology-Microbiology, Department of Biology, Chemistry, Pharmacy, Freie UniversitŠt Berlin, 14195 Berlin, Germany. # Present address: National Institutes of Diabetes and Digestive and Kidney Diseases (NIDDK)-National Institutes of Health (NIH), Bethesda, Maryland 20892, USA. Journal: Developmental Biology, in press Abstract Thyroxine deiodinases, the enzymes that regulate thyroxine metabolism, are essential for vertebrate growth and development. In the model organism Dictyostelium discoideum, a single intronless gene (dio3) encodes type III thyroxine 5' deiodinase. The amino acid sequence of D. discoideum Dio3 shares 37% identity with human T4 deiodinase and is a member of the thioredoxin reductase superfamily. dio3 is expressed throughout growth and development and by generating a knockout of dio3, we have examined the role of thyroxine 5' deiodinase in D. discoideum. dio3- had multiple defects that affected growth, timing of development, aggregate size, cell streaming, and cell-type differentiation. A prominent phenotype of dio3- was the breaking of late aggregates into small signaling centers, each forming a fruiting body of its own. cAMP levels, its relay, photo- and chemotaxis were also defective in dio3-. Quantitative RT-PCR analyses suggested that expression levels of genes encoding adenylyl cyclase A (acaA), cAMP-receptor A (carA) and cAMP-phosphodiesterases were reduced. There was a significant reduction in the expression of CadA and CsaA, which are involved in cell-cell adhesion. The dio3- slugs were likely to have a prestalk identity, with the expression of the prestalk marker ecmA being more pronounced than that of the prespore marker pspA. Thus, Dio3 seems to have roles in mediating cAMP synthesis/relay, cell adhesion and slug patterning. The phenotype of dio3- suggests that Dio3 may prevent the formation of multiple signaling centers during D. discoideum development. This is the first report of a thyroxine metabolism gene that is involved in growth and development in a lower eukaryote. Submitted by Shashi Prakash Singh [shashi_prakash5@yahoo.com] ---------------------------------------------------------------------- Rectified directional sensing in long-range cell migration Akihiko Nakajima, Shuji Ishihara, Daisuke Imoto and Satoshi Sawai Department of Basic Science, Graduate School of Arts and Sciences, University of Tokyo, Tokyo 153-8902, Japan. Nature Communications, in press How spatial and temporal information are integrated to determine the direction of cell migration remains poorly understood. Here, by precise microfluidics emulation of dynamic chemoattractant waves, we demonstrate that, in Dictyostelium, directional movement as well as activation of small guanosine triphosphatase Ras at the leading edge is suppressed when the chemoattractant concentration is decreasing over time. This ÔrectificationÕ of directional sensing occurs only at an intermediate range of wave speed and does not require phosphoinositide-3-kinase or F-actin. From modelling analysis, we show that rectification arises naturally in a single-layered incoherent feedforward circuit with zero-order ultrasensitivity. The required stimulus time-window predicts ~5 s transient for directional sensing response close to Ras activation and inhibitor diffusion typical for protein in the cytosol. We suggest that the ability of Dictyostelium cells to move only in the wavefront is closely associated with rectification of adaptive response combined with local activation and global inhibition. Submitted by Satoshi Sawai [cssawai@mail.ecc.u-tokyo.ac.jp] ============================================================== [End dictyNews, volume 40, number 26]