Figure 7. Rbp6 and Msi do not function co-operatively to regulate GSC identity, but mis-expression of Rbp6 causes loss of germ cells through apoptosis.

(A) Msi expression (red) in a w¹¹¹⁸ third instar larval testis is nuclear and found in germ cells of all stages. (*) denotes the hub. (B) Rbp6 antibody expression (red) is cytoplasmically localised to the cyst cells of the w¹¹¹⁸ third instar larval testis. (C) A representative confocal micrograph of a Rbp6¹,msi¹/Rbp6²,msi² 2 day old adult double mutant testis containing germ cells (red) of varying stages, from GSCs (*) to spermatocytes. CPCs (Zfh1, green) abut the hub (FasIII, blue) and take over positions where GSC’s have been lost (arrows) as a result of the msi mutation. No enhancement of the msi mutant phenotype was observed. (D–E) nos^Gal4;UAS-Rbp6 mutant testes vary from containing no germ cells (red, D) to containing only large spermatocytes in close proximity to the hub (white arrow, E). Acridine Orange labelling of w¹¹¹⁸ testes (green, F) and nosGal4;UAS-Rbp6 mutant testes (green, G) reveal more cell death in mutant tissue. Scale bars: 20 µm.