Difference in nuclear grouping during cyst polarization between the control and Merlin mutant spermatids. Dissected testes from the control FM6 (A), Mer3 (B-E), and Mer4 (F-H) males were stained with DAPI and examined as described before. Note that while the spermatid nuclei were grouped in one area (arrow) of the control cyst (A), the spermatid nuclei in the Mer3 (B-E) and Mer4 (F-G) cysts were seen as two diffuse groups (arrows). In some cases, the spermatid nuclei were scattered in the mutant cyst (H). Panel C shows a phase-contrast image of a Mer3 cyst, panel D displays the same cyst stained with DAPI, and panel E represents a merged image. The cyst shown in panels F and G was obtained from a male carrying the Mer4 mutation and a GFP marker as described in Materials and Methods.