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© The Rockefeller University Press, 0021-9525/1997//605 $5.00
The Journal of Cell Biology, Volume 138, Number 3, , 1997 605-614

Article

Dictyostelium RasG Is Required for Normal Motility and Cytokinesis, But Not Growth



Richard I. Tuxworth*,{ddagger}, Janet L. Cheetham*,{ddagger}, Laura M. Machesky*,§, George B. Spiegelmann||, Gerald Weeks||, and Robert H. Insall*,{ddagger}

* Medical Research Council Laboratory for Molecular Cell Biology, {ddagger} Department of Physiology, and § Department of Molecular Medicine, University College London, London WC1E 6BT, United Kingdom; and || Department of Microbiology and Immunology and Department of Medical Genetics, University of British Columbia, Vancouver V6T 1Z3, Canada

RasG is the most abundant Ras protein in growing Dictyostelium cells and the closest relative of mammalian Ras proteins. We have generated null mutants in which expression of RasG is completely abolished. Unexpectedly, RasG– cells are able to grow at nearly wild-type rates. However, they exhibit defective cell movement and a wide range of defects in the control of the actin cytoskeleton, including a loss of cell polarity, absence of normal lamellipodia, formation of unusual small, punctate polymerized actin structures, and a large number of abnormally long filopodia. Despite their lack of polarity and abnormal cytoskeleton, mutant cells perform normal chemotaxis. However, rasG– cells are unable to perform normal cytokinesis, becoming multinucleate when grown in suspension culture. Taken together, these data suggest a principal role for RasG in coordination of cell movement and control of the cytoskeleton.

1. Abbreviations used in this paper: GAP, GTPase-activating protein; GEF, guanine nucleotide exchange factors.

The work described in this paper was supported by a Wellcome Trust Career Development Fellowship 043754 to R.H. Insall, by a Medical Research Council Career Development Fellowship to L.M. Machesky, and by a grant from the Medical Research Council of Canada to G. Weeks. R.I. Tuxworth is supported by the Medical Research Council graduate program from the Institute of Molecular Cell Biology, University College London.

Please address all correspondence to Robert Insall, MRC Laboratory for Molecular Cell Biology, University College London, Gower Street, London WC1E 6BT, UK. Tel.: (44) 171 380 7270; Fax: (44) 171 380 7805; E-mail: dmcbrob{at}ucl.ac.uk


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