Global Chromatin Reprogramming in Fetal Germ Cells Figure 5. Global changes of H3K9me3 in fetal germ cells. Gonad preparations were stained with anti-H3K9me3 antibody. DAPI was used to visualize nuclei (blue). Other details are as in legend to Figure 1. doi:10.1371/journal.pone.0023848.g005 Histone globular domain marks in fetal germ cells Di-and trimethylation of residue K79 in the globular domain of histone H3 are interesting chromatin components, with somewhat debated and perhaps diverse functions between species [37]. H3K79me2 and H3K79me3 are associated with the DNA- unmethylated and methylated alleles of DMRs, respectively [38]. H3K79me2 and also H3K79me3 levels were very similar between germ cells and somatic cells in the female throughout fetal development and in the male at 11.5–13.5 dpc (Figure 7 and 8). Levels of both H3K79me2 and H3K79me3 sharply increased in male germ cells at 15.5 and remained high at 17.5 dpc. These two marks, however, showed complementary nuclear staining patterns (Figure 9) similarly to what was found in fibroblasts and oocytes [39]. Female germ cells and somatic cells have several large DAPI- positive compartments (Figure 9) and H3K79me2 excluded these DAPI-rich regions whereas H3K79me3 co-localized with DAPI PLoS ONE | www.plosone.org 6 August 2011 | Volume 6 | Issue 8 | e23848