Fig. 5. Increased dimethylation of H3_K4 on XY chromatin of Hr6b-knockout spermatocytes and spermatids. (A) Double immunostaining of wild-type and Hr6b-knockout diplotene nuclei with anti-H3_K4m2 (green) and anti-SYCP3 (red). Arrowhead indicates the XY body. (B) Quantification of H3_K4m2 immunofluorescent signal on autosomal and XY body chromatin of wild-type (wt) and Hr6b-knockout (ko) diplotene spermatocytes. Arbitrary units per µm² were calculated for the area covering the XY body and for the area covering the autosomes. Error bars represent the s.e.m. for 20 nuclei that were measured for each genotype from two different animals. (C) Immunostaining with anti-H3_K4m2 (green) combined with X chromosome FISH (red) on wild-type spermatocyte and spermatid nuclei (left panel). The right panels show immunostaining of wild-type and Hr6b-knockout spermatid nuclei with anti-H3K4m2 (green). DNA is stained with DAPI (blue). White arrows in the left panel indicate the position of the X chromosome, and the pink arrow denotes the Y chromosome. The arrowhead indicates an XY body of a pachytene spermatocyte. Bars, 10 µm.