Fig. 2. Wild-type function of zpg is required for differentiation and survival of male germ cells. Apical tips of testes from (A,C,E,G) wild type and (B,D,F,H) zpg^z-5352/Df(3L)Zn47 males. (A,B) Germ cells at the testis apical tip labeled by staining with anti-Vasa. (A) Wild type. Rosette of single germline stem cells (arrowhead) surrounding the apical hub (*); cysts of spermatogonia or young spermatocytes (arrows). (B) zpg^z-5352/Df(3L)Zn47. Single germ cells (arrowheads) away from the hub (*); small cluster of germ cells resembling early spermatogonia (arrow). (C,D) Same samples as in A,B stained with anti--Spectrin to label spectrosomes in stem cells (arrowhead in C) and gonialblasts (small arrow in C, arrowhead in D), and the linear branched fusomes in wild-type spermatogonia (large arrows in C). (C) Wild type. (D) zpg^z-5352/Df(3L)Zn47. Germ cells resembling gonialblasts with spectrosomes (arrowheads); clusters of germ cells with abnormally large spectrosomes instead of fusomes (arrow). (E,F) Hub cells at the testes apical tip (arrows) labeled with anti-Drosophila E-Cadherin. (E) Wild type. (F) zpg^z-5352/Df(3L)Zn47. Note the expanded number of hub cells. Scale bar: 50 µm. (G,H) Somatic cyst progenitor and cyst cells marked by ptc-GAL4; UAS-GFP. (G) Wild type. Note ‘lacy’ network of cyst cells enclosing developing germ cell clusters. (H) zpg^z-5352/Df(3L)Zn47. Cyst cells are present but mostly either enclose single germ cells or no germ cells.