Limits...
Dictyostelium RasG is required for normal motility and cytokinesis, but not growth.

Tuxworth RI, Cheetham JL, Machesky LM, Spiegelmann GB, Weeks G, Insall RH - J. Cell Biol. (1997)

Bottom Line: Unexpectedly, RasG- cells are able to grow at nearly wild-type rates.Despite their lack of polarity and abnormal cytoskeleton, mutant cells perform normal chemotaxis.Taken together, these data suggest a principal role for RasG in coordination of cell movement and control of the cytoskeleton.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom.

ABSTRACT
RasG is the most abundant Ras protein in growing Dictyostelium cells and the closest relative of mammalian Ras proteins. We have generated 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.

Show MeSH

Related in: MedlinePlus

Growth of wild-type and rasG− cells. (a) Growth on  surfaces. Wild-type (▪), rasG− (•), and rasG− cells rescued by  expression of rasG (▴) were seeded in Petri plates (105 cells/ plate) with 10 ml axenic medium. At intervals the cells were detached from the surface, and the number of cells in a small aliquot was counted. (b) Growth in suspension culture. Wild-type  (▪), rasG− (•), and rasG− cells rescued by expression of rasG  (▴) were transferred from Petri plates into axenic medium at  time zero and counted at intervals thereafter.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2141629&req=5

Figure 2: Growth of wild-type and rasG− cells. (a) Growth on surfaces. Wild-type (▪), rasG− (•), and rasG− cells rescued by expression of rasG (▴) were seeded in Petri plates (105 cells/ plate) with 10 ml axenic medium. At intervals the cells were detached from the surface, and the number of cells in a small aliquot was counted. (b) Growth in suspension culture. Wild-type (▪), rasG− (•), and rasG− cells rescued by expression of rasG (▴) were transferred from Petri plates into axenic medium at time zero and counted at intervals thereafter.

Mentions: Unexpectedly, rasG appears to be dispensable for growth under most conditions. As shown in Fig. 2 A, rasG− cells in liquid medium grow only slightly more slowly than wild-type (14.5 vs 13.4 h doubling time). rasG− cells also grow somewhat more slowly than wild-type on bacteria, forming colonies that are a little smaller than AX2 (data not shown).


Dictyostelium RasG is required for normal motility and cytokinesis, but not growth.

Tuxworth RI, Cheetham JL, Machesky LM, Spiegelmann GB, Weeks G, Insall RH - J. Cell Biol. (1997)

Growth of wild-type and rasG− cells. (a) Growth on  surfaces. Wild-type (▪), rasG− (•), and rasG− cells rescued by  expression of rasG (▴) were seeded in Petri plates (105 cells/ plate) with 10 ml axenic medium. At intervals the cells were detached from the surface, and the number of cells in a small aliquot was counted. (b) Growth in suspension culture. Wild-type  (▪), rasG− (•), and rasG− cells rescued by expression of rasG  (▴) were transferred from Petri plates into axenic medium at  time zero and counted at intervals thereafter.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2141629&req=5

Figure 2: Growth of wild-type and rasG− cells. (a) Growth on surfaces. Wild-type (▪), rasG− (•), and rasG− cells rescued by expression of rasG (▴) were seeded in Petri plates (105 cells/ plate) with 10 ml axenic medium. At intervals the cells were detached from the surface, and the number of cells in a small aliquot was counted. (b) Growth in suspension culture. Wild-type (▪), rasG− (•), and rasG− cells rescued by expression of rasG (▴) were transferred from Petri plates into axenic medium at time zero and counted at intervals thereafter.
Mentions: Unexpectedly, rasG appears to be dispensable for growth under most conditions. As shown in Fig. 2 A, rasG− cells in liquid medium grow only slightly more slowly than wild-type (14.5 vs 13.4 h doubling time). rasG− cells also grow somewhat more slowly than wild-type on bacteria, forming colonies that are a little smaller than AX2 (data not shown).

Bottom Line: Unexpectedly, RasG- cells are able to grow at nearly wild-type rates.Despite their lack of polarity and abnormal cytoskeleton, mutant cells perform normal chemotaxis.Taken together, these data suggest a principal role for RasG in coordination of cell movement and control of the cytoskeleton.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council Laboratory for Molecular Cell Biology, University College London, London WC1E 6BT, United Kingdom.

ABSTRACT
RasG is the most abundant Ras protein in growing Dictyostelium cells and the closest relative of mammalian Ras proteins. We have generated 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.

Show MeSH
Related in: MedlinePlus