X-linked genes more expressed in female eight-cell embryos show female-biased enrichment for H3K4me3 and depletion of H3K9me3 and H3K27me3 in 2i embryonic stem (ES) cells. After correcting for sex differences in X chromosome dosage, X-linked genes that do not show sex-biased enrichment of post-translational histone modifications should fit the model (black line). All X-chromosome genes were used as background (grey points). Enrichment was calculated for the 3 kb surrounding the transcriptional start site from ChIP-seq data generated from 2i ES cells. Dimorphic X-linked genes identified from eight-cell embryos are more expressed in females (orange points). (A) H3K4me3 is relatively enriched in females for the dimorphic genes (FEfemale = 1.47; p-value = 0.002) (B) H3K9me3 is relatively depleted in females for the dimorphic genes (FEfemale = 0.72; p-value = 0.028) (C) H3K27me3 is relatively depleted in dimorphic genes (FEfemale = 0.63; p-value = 0.005). Significance for fold enrichment was calculated using permutation tests.