Fig. 3. H3K4 methylation is removed during the early canoe stage. (A) Hoechst staining to visualise chromatin. (B) Anti-methylated H3K4 antibody staining on squashed testes of protamine-eGFP expressing flies. A high level of H3K4 trimethylation is detectable in spermatids with young elongating nuclei (double arrow). During the early canoe stage, the signal decreases (arrowhead) and vanishes completely from the late canoe stage (not shown) onwards (arrow). (C) There is no protamine-eGFP expression in young elongating nuclei and early canoe stage spermatids, whereas high expression is observed in individualising spermatids (arrow). (D) Merged images. Bars, 20 µm.