Histone H3 lysine 4 dimethylation is enriched on the inactive sex chromosomes in male meiosis but absent on the inactive X in female somatic cells.
Inactivation of the X chromosome occurs in female somatic cells and in male meiosis. In both cases, the inactive X chromosome undergoes changes in histone modifications including deacetylation of core histone proteins and enrichment with histone H3 lysine 9 (H3-K9) dimethylation. In this study we show that while the inactive X in female somatic cells is largely devoid of H3-K4 dimethylation, the inactive X in male meiosis is enriched with this modification. However, the inactive X chromosome in female somatic cells and the inactive X and Y in male meiosis are devoid of H3-K4 trimethylation. Further, trimethylation of H3-K4 is present at discrete regions along most of the autosomes, while H3-K4 dimethylation shows a more homogenous staining. Also, the Y chromosome is largely devoid of H3-K4 di- and trimethylation in somatic cells of both humans and mice, however, the Y chromosome is enriched with H3-K4 di- but not trimethylation throughout spermatogenesis. Our results provide insights into the differences between female somatic cells and male germ cells in inactivating the X chromosome, and suggest that trimethylation, and not dimethylation, of H3-K4 is a more robust indicator of the active regions of the genome.
Khalil
A M
AM
Division of Pediatrics Genetics, Center for Mammalian Genetics, University of Florida College of Medicine, Gainesville, FL 32610-0296, USA.
Driscoll
D J
DJ
D000818:Animals; D005260:Female; D006657:Histones / Q000378:metabolism*; D008214:Lymphocytes / Q000502:physiology; D008297:Male; D008540:Meiosis / Q000502:physiology*; D008745:Methylation; D051379:Mice; D014960:X Chromosome / Q000502:physiology / Q000648:ultrastructure*; D014998:Y Chromosome / Q000502:physiology / Q000648:ultrastructure*
D006657:Histones