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Dictyostelium RasD is required for normal phototaxis, but not differentiation.
A Wilkins1, M Khosla, D J Fraser
1MRC Laboratory for Molecular Cell Biology and Departments of Physiology, University College London, London WC1E 6BT, UK.
Genes & Development
|June 3, 2000
Summary
Disrupting the rasD gene in Dictyostelium discoideum eliminates phototaxis and thermotaxis, revealing a key role for RasD in stimulus-guided cell movement during development.
Area of Science:
- Cellular and Molecular Biology
- Developmental Biology
- Biochemistry
Background:
- RasD is a Dictyostelium homolog of mammalian Ras, highly expressed during multicellular development.
- Dictyostelium aggregates exhibit sensitive phototaxis and thermotaxis, moving towards light and heat sources.
- Prior research suggested RasD involvement in Dictyostelium development and cell-type determination.
Purpose of the Study:
- To investigate the role of the rasD gene in Dictyostelium phototaxis and thermotaxis.
- To determine if rasD disruption affects other developmental processes.
- To characterize a novel class of phototaxis mutant.
Main Methods:
- Gene disruption of rasD in Dictyostelium discoideum.
- Assay of phototactic and thermotactic behaviors in mutant aggregates.
- Observation of undirected movement and developmental processes in rasD-null cells.
Main Results:
- rasD gene disruption resulted in a near-complete loss of phototaxis and thermotaxis in Dictyostelium aggregates.
- Mutant cells showed no significant alterations in undirected movement.
- No obvious changes in development or cell-type determination were observed in rasD-null cells, contrary to previous hypotheses.
Conclusions:
- RasD plays a critical role in mediating phototaxis and thermotaxis in Dictyostelium.
- The RasD pathway is involved in linking environmental stimuli to coordinated cell migration.
- rasD-null cells represent a new category of phototaxis mutants, expanding our understanding of sensory pathways in cellular slime molds.