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Ras1-dependent signaling by ectopically-expressed Drosophila src gene product in the embryo and developing eye
S J Kussick1, K Basler, J A Cooper
1Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
Abstract:
The cellular functions of the Drosophila src 64B (Dsrc) gene product, Dsrc, and of most vertebrate Src-family kinases, are unknown. We have examined the effects of over-expression of wild type and mutated forms of Dsrc in transgenic Drosophila. Expression of both wild type Dsrc and a C-terminally truncated mutant at high levels during embryonic development induced extensive tyrosine phosphorylation of cellular proteins and caused considerable lethality, correlating with a block to germ-band retraction. Over-expression in the eye imaginal disc led to excess production of photoreceptor cells in the adult ommatidia. In contrast, expression of a kinase-inactive form of Dsrc caused distinct nervous system abnormalities in embryos and decreased the numbers of photoreceptor cells in the adult eye ommatidia. This suggests that active forms of Dsrc alter development by phosphorylation. Both the lethality and the eye roughening caused by activated Dsrc were partially suppressed by mutations in the Drosophila Ras1 gene. These results suggest that over-expressed Dsrc may function through Ras1 to stimulate differentiation in the embryonic nervous system and eye imaginal disc, and that kinase-active Dsrc interferes with these processes.
Insights
The Drosophila src 64B (Dsrc) gene product
Area of Science:
- Cellular biology
- Developmental biology
- Genetics
Background:
- The cellular functions of Drosophila src 64B (Dsrc) and most vertebrate Src-family kinases remain largely unknown.
- Investigating Dsrc's role can elucidate fundamental mechanisms of cell signaling and development.
- Src-family kinases are implicated in various cellular processes, including proliferation, differentiation, and survival.
Purpose of the Study:
- To investigate the cellular functions of the Drosophila src 64B (Dsrc) gene product.
- To determine the effects of over-expressing wild-type and mutated forms of Dsrc in transgenic Drosophila.
- To explore the downstream signaling pathways affected by Dsrc activity.
Main Methods:
- Generation of transgenic Drosophila expressing wild-type, C-terminally truncated, and kinase-inactive forms of Dsrc.
- Analysis of developmental phenotypes, including embryonic lethality, germ-band retraction, and eye development.
- Assessment of tyrosine phosphorylation levels in cellular proteins.
- Genetic interaction studies using mutations in the Drosophila Ras1 gene.
Main Results:
- Over-expression of active Dsrc (wild-type and truncated mutant) induced tyrosine phosphorylation, embryonic lethality, and blocked germ-band retraction.
- Active Dsrc over-expression in eye imaginal discs led to excess photoreceptor cell production.
- Expression of kinase-inactive Dsrc resulted in nervous system abnormalities and reduced photoreceptor cell numbers.
- Drosophila Ras1 mutations partially suppressed lethality and eye defects caused by activated Dsrc.
Conclusions:
- Active Dsrc modulates Drosophila development through phosphorylation events.
- Over-expressed Dsrc appears to signal through Ras1 to influence differentiation in the nervous system and eye imaginal disc.
- Kinase-active Dsrc can interfere with normal developmental processes, highlighting the importance of precise kinase activity regulation.