Fig. 4. Bmp downstream components are required in GSCs for their maintenance in the Drosophila testis. All the testes are labeled for lacZ (red), Hts (green) and DNA (blue). Marked wild-type or mutant GSCs (highlighted by broken lines) are identified as the cells that contain a spectrosome, directly contact hub cells and lack lacZ expression, whereas unmarked GSCs are lacZ positive (red). (A) The tip of a testis carrying a marked 2-day-old wild-type GSC. (B) The tip of a testis carrying two marked two-week old GSCs. (C) The tip of a testis carrying a marked 2-day-old tkv mutant GSC. (D) A testis that has lost a marked tkv GSC clone two weeks after clone induction. (E) The tip of the testis carrying a marked 2-day-old mad mutant GSC. (F) The tip of a testis that has lost a marked mad GSC clone 2 weeks after clone induction. All the images are shown at the same magnification. Scale bar: 10 µm.