Dictyostelium RasG is required for normal motility and cytokinesis, but not growth.
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.
Tuxworth
R I
RI
Medical Research Council Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom.
Cheetham
J L
JL
Machesky
L M
LM
Spiegelmann
G B
GB
Weeks
G
G
Insall
R H
RH
D000199:Actins / Q000032:analysis; D000818:Animals; D002448:Cell Adhesion; D002455:Cell Division; D016764:Cell Polarity; D002633:Chemotaxis; D003599:Cytoskeleton / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D004023:Dictyostelium / Q000166:cytology / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D009068:Movement; D009154:Mutation; D009218:Myosins / Q000502:physiology; D011554:Pseudopodia / Q000648:ultrastructure; D014162:Transfection; D018631:ras Proteins / Q000235:genetics / Q000502:physiology*
D000199:Actins; D009218:Myosins; D018631:ras Proteins