SRC is upstream of βPS integrin subunit for polar cell engulfment, border cell migration, and cell cluster morphology. (A) Verification by polymerase chain reaction of the presence of csk inverted repeated sequence which is indicated by a band of ∼400 base pairs (see Materials and methods). “L” indicates Ladder; (1) w¹¹¹⁸, (2) cskRNAi, (3) mys¹; cskRNAi, (4) mys¹/c306-Gal4; cskRNAi/mysRNAi, (5) mysRNAi (see Table S1 to specific genotypes). (B) Quantification of border cell migration of egg chambers at stage 10 for the genotypes indicated (see Materials and methods). The total number of samples is indicated on top of each bar. (C–D’) Maximum intensity projection from seven slices (z-step: 0.6 µm) of confocal images of border cell clusters from stage 10 egg chambers expressing the genotypes indicated. Egg chambers were stained with CAD (green) and FAS3 (magenta). Yellow asterisks in C indicate internalized polar cells and white ones in (D) indicate non-internalized polar cells. Scale bar: 5 µm. (E–H’) Maximum intensity projection from six slices (z-step: 1 µm) (E–F’) or 20 slices (z-step: 0.5 µm) (G–H’) of confocal images of egg chambers at stage 10 (E–F’) or stage 9 (G–H’) expressing the genotypes indicated. (E’–H’) magnify the insets in E–H. Egg chambers were stained with pSHARK (pY927; gray) and DAPI (blue). pSHARK accumulation in centripetal cells is labeled by orange arrows in E–F. (E’’–H’’) Same images are shown in E’–H’ where pSHARK staining is shown in a Royal LUT. White represents the highest amount of protein and black the lowest one. White arrows in G’ and G’’ point to pSHARK accumulation and green arrowheads point to a ring canal enriched in pSHARK. Scale bar: 50 µm in E–H and 5 µm in E’–H’’. Polar cells in panels C–D and E’–H’ are outlined with a yellow dashed line. White or yellow asterisks indicate non-internalized or fully internalized polar cells, respectively.