Fig. 2: Opposite actions of EGFR and JAK-STAT signaling pathways restrict E-Cadherin levels to a subpopulation of PFCs.
Posterior is to the right. A–D Max z-projections of E-Cadherin (Ecad, magenta hot filter) immunostaining on stage 8 follicles. The white dotted lines indicate the nurse-oocyte frontier. A–C Yellow and blue dotted rectangles indicate magnified FCs in contact with the oocyte and further from it, respectively. A Control follicle (shg-LacZ). B Follicle expressing shg-RNAi in germ cells under the control of nos-Gal4 resulting in a mispositioned oocyte. C grk mutant follicle showing high levels of E-Cadherin in FCs around the oocyte. D Mosaic clones (GFP positive, green) expressing EGFR-RNAi (#JF01084 line, similar phenotypes were obtained with #KK100051 line). White dotted square indicates the magnified zone, green dotted line outlines a PFC clone presenting high E-Cadherin levels. B–D 100% of stage 7-10 follicles analyzed presented similar phenotypes. E-F’ Posterior-most PFCs are magnified (white dotted rectangles). Yellow, orange, green, red and white stars indicate PCs, PC + 1, +2, +3 and +4 rows respectively. E,E’ shg-LacZ reporter (hemizygous) in control follicle and in follicle expressing upd-RNAi in PCs under the control of upd-Gal4 stained for F-Actin (gray, phalloidin), DNA (cyan, DAPI) and beta-galactosidase (βgal, red hot filter). See Supplementary Fig. 3 for quantification. F,F’ Max z-projections of 4 consecutive 1 μm confocal sections. Control follicle and follicle expressing hopTUM in PFCs under the control of E4-Gal4 stained for E-Cadherin (magenta hot filter). G Schematic representation of the crosstalk between Grk/EGFR and E-Cadherin to restrict JAK-STAT activity to a subpopulation of 20 PFCs highlighted in the pole view. Subsequently, shg expression is induced in those cells, creating a positive feedback loop. St: stage. Scale: 30 µm except magnifications 10 µm for (A–D) and 15 µm for (E-F’). Information about reproducibility is provided in Supplementary Table 7.
