Fig. 4: JAK-STAT signaling in PFCs is necessary and sufficient for MRLC di-phosphorylation and microtubule network polarity in the oocyte.

Posterior is to the right. Yellow, orange, green, red and white stars indicate PCs, PC + 1, +2, +3 and +4 rows respectively. A,A’,A” Control follicle (w¹¹¹⁸) and follicles expressing upd-RNAi in PCs under the control of upd-Gal4 or hop^TUM in PFCs under the control of E4-Gal4 are stained for MRLC-2P (royal filter), F-Actin (gray, phalloidin), DNA (gray or cyan, DAPI). PACs (pink dotted rectangles) and adjacent PFCs (white dotted rectangles) are magnified. “Tight” and “Spaced” refer to the perivitelline space. White arrowheads point to the correlation between the end of the MRLC-2P signal and the separation of oocyte and PFC membranes. B, C Quantifications of the MRLC-2P region size in number of facing FCs around PCs in control follicles, upd knocked down or hop^TUM follicles. D,D’ Accumulation of Khc::LacZ to assess microtubule network polarity in control follicles and in follicles expressing upd-RNAi in PCs under the control of upd-Gal4, stained for β-galactosidase (βgal, royal filter), and DNA (gray, DAPI). D’ Max z-projections of 2 consecutive 1 μm confocal sections. Phenotypes are classified from “Partial” (both smaller Khc::βgal accumulation, facing <4 PFCs, blue arrowhead, and dispersed in cytoplasm, blue arrow) to “Dispersed” (absent from cortex). E Quantification of Khc::βgal accumulation size as the number of facing FCs around PCs in control. F Khc::βgal phenotype categories in Khc::LacZ;upd>upd-RNAi stage 9 and 10a follicles. Those defects were never observed in control follicles. St: stage. #: number. Scale: 30 µm except magnifications 15 µm. Statistical tests: two-sided Mann–Whitney. Information about statistics and reproducibility is provided in Supplementary Tables 14–15. Source data are provided as a Source Data file.