Fig. 5. fu function is required in prefollicular cells for centripetal migration and stalk formation. All ovarioles are oriented with the anterior-most region towards the top or top right-hand corner. (A,A') Mosaic ovariole in which fu^mH63 mutant follicle cell clones lacking an arm-lacZ reporter construct have been induced. Ovariole is triple-stained with DAPI (A), anti-ß-galactosidase (A', green) and anti-Fas III (A', red) antibodies. fu⁺ somatic cells are found only in the most anterior part of the ovariole (prefollicular cells, bracket). Follicular cells exhibit weak Fas III, but no ß-galactosidase staining. White arrowheads point to pairs of polar cells belonging to the second egg chamber, whereas the open arrowhead indicates anterior polar cells belonging to the more posterior egg chamber (as determined after superposition of DAPI and ß-galactosidase images, data not shown). Polar cells presented in insert are not in the same focal plane as follicular and germline cells shown in A and A'. (B-E') Mosaic ovarioles in which fu mutant follicle cell clones lacking a tub-lacZ reporter construct have been induced. Ovarioles are double-stained with DAPI (B-E) and anti-ß-galactosidase antibodies (B'-E'). (B,B',E,E') fu^G3 mosaic ovarioles. (C-D') fu^JB3 mosaic ovarioles. (B) Arrows indicate the two small oocyte nuclei present in the multicyst egg chamber. (C,C') Arrows indicate lateral accumulation of fu⁺ cells in stalk-like structures. (D-E') Arrows indicate fu mutant somatic cells and asterisks indicate fu⁺ cells.