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

Defective cytokinesis in  rasG− cells. (a) Epifluorescent micrograph of a multinucleate rasG− cell  that has been growing in shaken culture for 5 d. F-actin is visualized with  rhodamine-conjugated phalloidin, nuclei with Hoechst 33258. (b) Phase contrast micrograph of a multinucleate  rasG− cell undergoing traction-mediated cytofission, 10 min after plating.  Bars, 20 μm.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2141629&req=5

Figure 6: Defective cytokinesis in rasG− cells. (a) Epifluorescent micrograph of a multinucleate rasG− cell that has been growing in shaken culture for 5 d. F-actin is visualized with rhodamine-conjugated phalloidin, nuclei with Hoechst 33258. (b) Phase contrast micrograph of a multinucleate rasG− cell undergoing traction-mediated cytofission, 10 min after plating. Bars, 20 μm.

Mentions: A second unusual feature of rasG− cells is the abundance of small, punctate F-actin structures within the cell body. These are conspicuously present in the majority of cells (Figs. 3, B and C, and 4; particularly clear actin structures are also visible in Fig. 6 A). Similar structures are seen in a small proportion of wild-type cells, but in lower numbers (1–2 per cell; data not shown). Three-dimensional reconstruction of confocal Z-series indicates that the structures are roughly spherical and are localized to the cortex of the base and the upper surface of the cells (data not shown; a QuickTime video showing an example of a three-dimensional reconstruction is available on the World Wide Web at http://www.ucl.ac.uk/∼dmcbrob/movies.html). The precise nature of these structures is as yet unknown. Mutant and wild-type cells contain similar quantities of F-actin per cell (data not shown); the differences appear to reflect a failure of organization, rather than an inability to polymerize actin.


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)

Defective cytokinesis in  rasG− cells. (a) Epifluorescent micrograph of a multinucleate rasG− cell  that has been growing in shaken culture for 5 d. F-actin is visualized with  rhodamine-conjugated phalloidin, nuclei with Hoechst 33258. (b) Phase contrast micrograph of a multinucleate  rasG− cell undergoing traction-mediated cytofission, 10 min after plating.  Bars, 20 μm.
© Copyright Policy
Related In: Results  -  Collection

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

Figure 6: Defective cytokinesis in rasG− cells. (a) Epifluorescent micrograph of a multinucleate rasG− cell that has been growing in shaken culture for 5 d. F-actin is visualized with rhodamine-conjugated phalloidin, nuclei with Hoechst 33258. (b) Phase contrast micrograph of a multinucleate rasG− cell undergoing traction-mediated cytofission, 10 min after plating. Bars, 20 μm.
Mentions: A second unusual feature of rasG− cells is the abundance of small, punctate F-actin structures within the cell body. These are conspicuously present in the majority of cells (Figs. 3, B and C, and 4; particularly clear actin structures are also visible in Fig. 6 A). Similar structures are seen in a small proportion of wild-type cells, but in lower numbers (1–2 per cell; data not shown). Three-dimensional reconstruction of confocal Z-series indicates that the structures are roughly spherical and are localized to the cortex of the base and the upper surface of the cells (data not shown; a QuickTime video showing an example of a three-dimensional reconstruction is available on the World Wide Web at http://www.ucl.ac.uk/∼dmcbrob/movies.html). The precise nature of these structures is as yet unknown. Mutant and wild-type cells contain similar quantities of F-actin per cell (data not shown); the differences appear to reflect a failure of organization, rather than an inability to polymerize actin.

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