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Ras controls growth, survival and differentiation in the Drosophila eye by different thresholds of MAP kinase
K Halfar1, C Rommel, H Stocker
1Zoologisches Institut, Universität Zürich, Winterthurerstrasse 190, Switzerland.
Abstract:
Ras mediates a plethora of cellular functions during development. In the developing eye of Drosophila, Ras performs three temporally separate functions. In dividing cells, it is required for growth but is not essential for cell cycle progression. In postmitotic cells, it promotes survival and subsequent differentiation of ommatidial cells. In the present paper, we have analyzed the different roles of Ras during eye development by using molecularly defined complete and partial loss-of-function mutations of Ras. We show that the three different functions of Ras are mediated by distinct thresholds of MAPK activity. Low MAPK activity prolongs cell survival and permits differentiation of R8 photoreceptor cells while high or persistent MAPK activity is sufficient to precociously induce R1-R7 photoreceptor differentiation in dividing cells.
Insights
Ras signaling in Drosophila eye development controls cell growth, survival, and differentiation. Distinct MAPK activity thresholds regulate these temporally distinct Ras functions, impacting photoreceptor cell development.
Area of Science:
- Developmental Biology
- Cell Signaling
- Genetics
Background:
- Ras proteins are crucial regulators of numerous cellular processes.
- In Drosophila eye development, Ras plays distinct roles in dividing and postmitotic cells.
Purpose of the Study:
- To investigate the specific functions of Ras during Drosophila eye development.
- To elucidate how different thresholds of MAPK activity mediate Ras functions.
Main Methods:
- Utilized molecularly defined complete and partial loss-of-function mutations of Ras.
- Analyzed the impact of these mutations on cell behavior and differentiation in the developing eye.
Main Results:
- Ras is required for growth in dividing cells but not essential for cell cycle progression.
- In postmitotic cells, Ras promotes survival and differentiation of ommatidial cells.
- Distinct MAPK activity levels correlate with specific Ras functions: low MAPK for R8 survival/differentiation, high MAPK for precocious R1-R7 differentiation.
Conclusions:
- Ras-mediated functions in Drosophila eye development are dose-dependent on MAPK activity.
- Specific MAPK thresholds precisely control cell survival, differentiation timing, and cell fate decisions.