Fig. 1. Germ cells that lack zpg fail to differentiate. (A) The Drosophila germarium. In all figures, anterior is to the left and posterior to the right. Germ line stem cells (GSCs) are located at the anterior of the ovariole. Progressively more developed germ cells are located posteriorly: a putative intermediate state (or pre-cystoblasts, Pre-Cb), cystoblasts (Cb), dividing cysts and egg chambers (EC). The somatic niche is composed of terminal filament cells (TF), cap cells (CpC) and inner-sheath cells (IS). (B) zpg ovaries were stained with anti-Vasa to mark the germ line (green) and with an antibody that recognizes the spectrosome, fusome and the cell cortex (mAb 1B1; red). Only a few germ cells at the anterior tip of the ovarioles could be observed. Some of those germ cells are attached to cap cells (arrowheads). (C,D) Wild-type (C) or zpg (D) ovaries stained with anti-Vasa (green) and anti-BamC (red) to mark cystoblasts and dividing cysts. In wild type, a full complement of germ line cells, from GSCs to dividing (yellow; arrow) and budding cysts could be observed. In zpg ovaries only a few germ cells at the tip of the ovariole could be observed, mostly lacking BamC staining (panel D depicts many such ovarioles, each containing a few cells). (E) Wild-type and zpg ovaries were co-labeled with anti-Zpg (green) and with mAb 1B1 (red). Zpg is expressed on the membrane of germ cells in the germarium. In zpg ovaries, no staining with the anti-Zpg antibody was observed, attesting to the specificity of the antibody and to the fact that the alleles used in this study may be protein nulls (E, inset). Scale bars: in B, 20 µm for B,C,E; in D, 50 µm.