H3K4 methylation is not involved in the H3K27me3 boundary formation at the Xic. (A) Map of Xic (see Figure 1A). (B) ChIP analysis showing the distribution of histone H3 modifications at the Xic in female embryonic stem (ES) cells (LF2) using antibodies against H3K27 trimethylation (H3K27me3, black line), H3K4 dimethylation (H3K4me2, red line) and H3K4 trimethylation (H3K4me3, blue line). (C) Extensive analysis of H3K4me2 and (D) H3K4me3 in wild-type (Ma1L, black line) and Tsix-truncated (Ma2L, red line) male ES cells. Insets focus on the percentage of immunoprecipitation observed at the Xist 5' region.