Loss of Tj affects the structure of the stem cell niche.

(A,B) Adult ovaries. bab-lacZ highlights TFs and adjacent cap cells. (A) In a control (wt) ovary, a bundle of ovarioles is present, each with a TF at the tip, followed by a cap cell cluster (Cap), germarium (Gm) and series of follicles (Fl). (B) The rudimentary tj^eo2/tj^eo2 (tj^null) mutant ovary (Ov) has irregularly distributed and abnormally long TFs, and germarium and follicles are missing. Od, oviduct; Fb, fatbody. (C) Comparison of the number of TF and cap cells in control (+), tj³⁹/tj^eo2 (tj^hypo), and tj^eo2/tj^eo2 (tj^null) ovarioles. (D-F) Niches of 2-day-old pupal ovaries. (D) In the control (wt), Tj-positive (white) cap cells are round and form a cluster at the base of the TF. TC, transition cell. (E,F) In a tj^z4735/tj^eo2 (tj^null) ovary, cells expressing non-functional Tj protein are disc-shaped and either arranged in a single file, forming a stalk similar to the adjacent TF cells (E, F #1), or form a branched stalk (F #2). (G-I) Tip of an adult ovariole. Hts (red) outlines all cells, Vasa (green) marks germline cells, a yellow arrowhead marks the germarium/TF boundary, and red and blue arrows mark the posterior-and anterior-most cap cell, respectively. (G) In wild type (wt), all Tj-positive cells (white) are located inside the germarium, and the transition cell marks the boundary towards the TF. OS, ovariole sheath. (H,I) In a tj³⁹/tj^eo2 (tj^hypo) ovary, a variable number of Tj-positive cells have become part of the TF (see anterior shift of the blue and red arrows). The Tj signal is weaker in the tj^hypo mutant (H,I) than in wild type (G). (J) Location of cap cells in tj³⁹/tj^eo2 (tj^hypo) ovarioles. (K,L) Quantification of anterior niche cells, which include cap and TF cells, in tj^eo2/tj^eo2 (tj^null) (K) and tj³⁹/tj^eo2 (tj^hypo) ovarioles (L). Graphs (C,J-L) are 'box' (25–75 percentile) and 'whisker' (maxima/minima) diagrams, showing the median (bar) and mean (plus sign). n, sample size; n.s., not significant (P≥0.05). Genotypic markers: bab-lacZ (A,B), 1444-lacZ/+ (D-F), B1-lacZ or B1-lacZ/+ (C,K). Anterior is up in all images. Scale bars: 50 μm in A,B; 10 μm in D-I.