Fig. 3. GSCs and gonialblasts but not other differentiated germ cells are responsive to Bmp signaling in the testis. The hub cells and the GSCs in A, B and D-F are highlighted by circles and broken lines, respectively. (A) The tip of a Dad-lacZ/+ testis labeled for nuclear lacZ (red), Hts (green) and DNA (blue), showing that all five GSCs and all gonialblasts (arrowhead) express Dad. Arrows indicate that somatic cyst cells also express Dad. (B) The tip of a gbb⁴/gbb^D20; Dad-lacZ/+ testis labeled for nuclear lacZ (red), Hts (green) and DNA (blue), showing that three remaining GSCs and all the gonialblasts do not have detectable Dad expression. (C) The tip of a testis overexpressing Dad specifically in the germ cells labeled for Hts (green) and DAPI (blue), showing no germ cells in the testis. (D) The tip of a wild-type testis labeled for pMad (red), Hts (green) and DAPI (blue), showing pMad accumulation predominantly in GSCs. (E) The tip of a gbb⁴/gbb^D4 mutant testis labeled for pMad (red), Hts (green) and DAPI (blue), showing no detectable pMad accumulation in GSCs. (F) The tip of a punt¹⁰⁴⁶⁰/punt¹³⁵ mutant testis labeled for pMad (red), Hts (green) and DAPI (blue), showing no detectable pMad accumulation in the remaining GSC. All the images are shown at the same magnification. Scale bar: 10 µm.