Maintenance of stem cells in the Drosophila midgut. A, B: Clone (green) derived from single ISC after three weeks; WT (A) and beta-catenin mutant (no Wg signaling). C, D: ISCs are labeled by expression of the escargot (Esg) gene (green). Number of proliferating ISCs (BrdU-positive, yellow) is enhanced in animals lacking the apc gene (D; hyperactivity of Wg signaling), compared to wild type (C). E, F: Number of ISCs expressing the Jak/Stat signal Unpaired (Upd; green) is increased following the activation of Reaper (Rpr; panel F) which induces enterocyte cell death. G, H, I: ISCs are labeled by expression of Esg (green). Loss of causes strong increase in ISC number (H). Concomitant block of Jak/Stat pathway rescues this phenotype (I). J: Schematic image of Drosophila midgut, depicting signaling interactions involved in controlling proliferation and differentiation of intestinal cells.