In wild type egg chambers Fasciclin III is expressed in all follicle cells up to stage 3 of oogenesis and then becomes restricted to the polar follicle cells at the anterior and pos terior poles of the follicular epithelium. Reduction of Notch activity arrests follicle cells in an undifferentiated state and up regulates FasIII expression. Follicle cell clones mu tant for awd show strong expression sellekchem of FasIII after stage 6, indicating that they are defective in terminal differentiation. Down regulation of cut Inhibitors,Modulators,Libraries in wild type follicle cells is medi ated by Hindsight, an up regulation target of Notch. To examine loss of Notch target gene expression, we used the MARCM method of clonal analysis, which results in GFP expression in mutant cells, so as to ensure that lack of gene expression is not the result of cell death.

In contrast to wild type follicle cells, the MARCM clone of awd mutant cells does not express Hnt after stage 6. To further con firm that Notch signaling is attenuated in awd mutant follicle cells, the Inhibitors,Modulators,Libraries expression of GbeSu m8 lacZ transcrip tional reporter for Notch activity was examined. In MARCM awd clones, B galactosidase staining is absent or strongly reduced. The Notch signaling defect in awd mutant cells sug gested a potential mechanism Inhibitors,Modulators,Libraries for the original defining phenotype of awd abnormal wing discs, because during development Notch specifies the dorsal ventral margin of the wing discs and the vein intervein boundary, and is important for disc cell proliferation. Loss of Notch function causes wing margin defects and widening of wing veins.

As shown in Figure 3, 72% of adult mosaic flies show typical Notch phenotypes in wings with notched wing margins and wing vein thick ening. In wild type wing discs, activation Inhibitors,Modulators,Libraries of the Notch pathway at the dorsal ventral boundary leads to the expression of target gene prod ucts, such as the signaling molecule Wingless. Loss of Inhibitors,Modulators,Libraries awd function abolished the Wg staining in third instar wing disc clones at the dorsal ventral boundary. To further verify the Notch signaling defect, we examined GbeSu m8 lacZ reporter expression using a different mosaic fly gener ated by the MARCM system. Similar to our results in follicular epithelium, B galactosidase expression in awd mutant clones in the dorsal ventral boundary is lost. awd function is required for signaling after the S2 cleavage of Notch In the egg chamber, Notch Gefitinib buy functions in the follicle cells while the ligand Delta is expressed in the abutting germ line cells. Since the awdj2A4 clones were induced specifically in follicle cells, the defective Notch signaling in mutant follicle cells is not likely to be the result of a defect in Delta expression or endocytosis in the abutting germline cells.