dictyNews Electronic Edition Volume 42, number 20 September 2, 2016 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 ========= Local Ras activation, PTEN pattern, and global actin flow in the chemotactic responses of over-sized cells Markus Lange, Jana Prassler, Mary Ecke, Annette Müller-Taubenberger, Günther Gerisch J Cell Sci, in press Chemotactic responses of eukaryotic cells require a signal processing system that translates an external gradient of attractant into directed motion. To challenge the response system to its limits, we increased the size of Dictyostelium disciodeum cells using electric-pulse induced fusion. Large cells formed multiple protrusions at different sites along the gradient of chemoattractant, which independently turned towards the gradient direction and competed with each other. Finally, these cells succeeded to re-establish polarity by coordinating front and tail activities. To analyze the responses, we combined two approaches, one aimed at local responses by visualizing the dynamics of Ras activation at the front regions of re-orientating cells, the other at global changes of polarity by monitoringfront-to-tail directed actin flow. Asymmetric Ras activation in turning protrusions underscores that gradients can be sensed locally and translated into orientation. Different to cells of normal size, the polarity of large cells is not linked to an increasing front-to-tail gradient of the PIP3-phosphatase PTEN. But even in large cells, the front communicates with the tail through an actin flow that might act as carrier of a protrusion inhibitor. submitted by: Günther Gerisch [gerisch@biochem.mpg.de] ============================================================== [End dictyNews, volume 42, number 20]