Notch signaling through tramtrack bypasses the mitosis promoting activity of the JNK pathway in the mitotic-to-endocycle transition of Drosophila follicle cells.
BACKGROUND
The follicle cells of the Drosophila egg chamber provide an excellent model in which to study modulation of the cell cycle. During mid-oogenesis, the follicle cells undergo a variation of the cell cycle, endocycle, in which the cells replicate their DNA, but do not go through mitosis. Previously, we showed that Notch signaling is required for the mitotic-to-endocycle transition, through downregulating String/Cdc25, and Dacapo/p21 and upregulating Fizzy-related/Cdh1.


RESULTS
In this paper, we show that Notch signaling is modulated by Shaggy and temporally induced by the ligand Delta, at the mitotic-to-endocycle transition. In addition, a downstream target of Notch, tramtrack, acts at the mitotic-to-endocycle transition. We also demonstrate that the JNK pathway is required to promote mitosis prior to the transition, independent of the cell cycle components acted on by the Notch pathway.


CONCLUSIONS
This work reveals new insights into the regulation of Notch-dependent mitotic-to-endocycle switch.
Jordan
Katherine C
KC
Department of Biochemistry, University of Washington, Box 357350, Seattle, WA 98195, USA. kjordan@u.washington.edu
Schaeffer
Valerie
V
Fischer
Karin A
KA
Gray
Elizabeth E
EE
Ruohola-Baker
Hannele
H
D000818:Animals; D002454:Cell Differentiation; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000201:enzymology / Q000502:physiology*; D004847:Epithelial Cells / Q000378:metabolism; D005260:Female; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008938:Mitosis / Q000502:physiology*; D008954:Models, Biological; D018716:Molecular Mimicry; D006080:Ovarian Follicle / Q000166:cytology* / Q000378:metabolism; D051880:Receptors, Notch / Q000378:metabolism*; D012097:Repressor Proteins / Q000378:metabolism*; D015398:Signal Transduction
D029721:Drosophila Proteins; C497759:N protein, Drosophila; D051880:Receptors, Notch; D012097:Repressor Proteins; C075878:ttk protein, Drosophila; D048031:JNK Mitogen-Activated Protein Kinases