Dynamics of DOT1L localization and H3K79 methylation during meiotic prophase I in mouse spermatocytes

Abstract

During meiotic prophase I, interactions between maternal and paternal chromosomes, under checkpoint surveillance, establish connections between homologs that promote their accurate distribution to meiotic progeny. In human, faulty meiosis causes aneuploidy resulting in miscarriages and genetic diseases. Meiotic processes occur in the context of chromatin, therefore histone post-translational modifications are expected to play important roles. Here, we report the cytological distribution of the evolutionarily conserved DOT1L methyltransferase and the different H3K79 methylation states resulting from its activity (mono-, di- and tri-methylation; H3K79me1, me2 and me3, respectively) during meiotic prophase I in mouse spermatocytes. In the wild type, whereas low amounts of H3K79me1 are rather uniformly present throughout prophase I, levels of DOT1L, H3K79me2 and H3K79me3 exhibit a notable increase from pachynema onwards, but with differential subnuclear distribution patterns. The heterochromatic centromeric regions and the sex body are enriched for H3K79me3. In contrast, H3K79me2 is present all over the chromatin, but is largely excluded from the sex body despite the accumulation of DOT1L. In meiosis-defective mouse mutants, the increase of DOT1L and H3K79me is blocked at the same stage where meiosis is arrested. H3K79me patterns, combined with the cytological analysis of the H3.3, γH2AX, macroH2A and H2A.Z histone variants, are consistent with a differential role for these epigenetic marks in male mouse meiotic prophase I. We propose that H3K79me2 is related to transcriptional reactivation on autosomes during pachynema, whereas H3K79me3 may contribute to the maintenance of repressive chromatin at centromeric regions and the sex body.

A Chromatin-Dependent Role of the Fragile X Mental Retardation Protein FMRP in the DNA Damage Response

“…However, it remains unclear whether FMRP binds methyl histones with some specificity in vivo and which methyltransferases are necessary for FMRP chromatin recruitment. Dot1, the H3K79 methyltransferase, has been shown to play a role in yeast meiosis (Ontoso et al, 2013a; San-Segundo and Roeder, 2000). In addition, recent reports demonstrated an increase in H3K79me2 and H3K79me3 levels in mouse spermatocytes in pachytene with H3K79me3 specifically enriched at the sex chromosomes and centromeres (Ontoso et al, 2013b).…”

The emerging roles of DOT1L in leukemia and normal development

“…Despite the similar dynamics of DOT1L, H3K79me2 and H3K79me3, the sub-nuclear localization of these marks differs. 34 DOT1L and H3K79me3 levels significantly increase in the heterochromatic sex body during diplonema and diakinesis, with H3K79me3 also increasing at the centromeres. Conversely, H3K79me2 is present throughout the chromatin, except for at the sex body, despite the increase in DOT1L levels here.…”

“…A recent study used immunofluorescence to examine H3K79 methylation throughout meiotic prophase I in mouse spermatocytes. 34 In wild-type mice, DOT1L, H3K79me2 and H3K79me3 levels increase steadily from pachynema through prophase I, whereas H3K79 mono-methylation is present at low levels. Despite the similar dynamics of DOT1L, H3K79me2 and H3K79me3, the sub-nuclear localization of these marks differs.…”

“…Interestingly, patterns of the histone variants gH2AX, macroH2A, H2A.Z and H3.3 correlated with certain aspects of DOT1L and H3K79 methylation accumulation. 34 The distribution of the H3K79 methylation marks suggests that H3K79me2 may be involved in transcriptional re-activation of autosomes during pachynema, whereas H3K79me3 may contribute to maintenance of silencing at the sex body and the centromeres. 34 An evolutionarily conserved role of DOT1L in embryonic development The results described above suggest that DOT1L is important in early development in mammals, and this function seems to be evolutionarily conserved in Drosophila.…”

“…34 The distribution of the H3K79 methylation marks suggests that H3K79me2 may be involved in transcriptional re-activation of autosomes during pachynema, whereas H3K79me3 may contribute to maintenance of silencing at the sex body and the centromeres. 34 An evolutionarily conserved role of DOT1L in embryonic development The results described above suggest that DOT1L is important in early development in mammals, and this function seems to be evolutionarily conserved in Drosophila. Indeed, grappa (gpp), the Drosophila ortholog of Dot1L, is involved in fly development, where it is required for polycomb group (Pc-G)-mediated homeotic gene silencing.…”