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In human sperm, H4K20me3 is abundantly preserved in retrotransposons, satellite repeats and olfactory genes, and maintains herewith the somatic-like pattern

ABSTRACT: In human sperm, preserved histones evading histone-to-protamine replacement were observed in certain genes and gene promoters, but also in distal intergenic and repetitive DNA regions. The substantiality of the latter and its putative biological role are still a subject of hot debate. To shed more light on this issue we analyzed H4K20me3, a histone mark regulating heterochromatic and repetitive DNA in somatic cells, which was recently detected in human sperm. Our immunohistochemical and western blot analyses revealed the presence of H4K20me3 in male germ cells at every stage of spermatogenesis and in mature sperms, respectively. By ChIP-sequencing of the motile sperm fractions from three biological replicates we found 4.56% of the sperm genome to be occupied by H4K20me3. By comparing the genome-wide binding sites of H4K20me3 in sperm cells and somatic cells (K562) we found correspondences in 77% of respective peaks. The majority of binding sites (70%) were detected in distal intergenic and intron regions. Intriguingly, H4K20me3 enrichments could be observed in both somatic and sperm cells within satellite repeats and retrotransposons, particularly in long interspersed nuclear repeats (LINEs) and retrotransposons containing long terminal repeats (LTR-retrotransposons). Broad cluster arrangements and strong enrichments in olfactory receptor genes were also characteristic for H4K20me3. This is the first time H4K20me3 is characterized at the genome-wide level in human sperm and compared to somatic cells. Our results reveal that H4K20me3 constitutes the majority of histones preserved in matured human sperm and maintains a somatic-like distribution pattern.

ORGANISM(S): Homo sapiens

PROVIDER: GSE129239 | GEO | 2019/04/03

REPOSITORIES: GEO

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Project description:Background: Global DNA methylation contributes to genomic integrity by supressing repeat associated transposition events. Several chromatin factors are required in addition to DNA methyltransferases to maintain DNA methylation at intergenic and satellite repeats. Embryos lacking Lsh, a member of the SNF2 superfamily of chromatin helicases, are hypomethylated. The interaction of Lsh with the de novo methyltransferase, Dnmt3b, facilitates the deposition of DNA methylation at stem cell genes. We wished to determine if a similar targeting mechanism operates to maintain DNA methylation at repetitive sequences. Results: We used HELP-seq to map genome wide DNA methylation patterns in Lsh-/- and Dnmt3b-/- somatic cells. DNA methylation is predominantly lost from specific genomic repeats in Lsh-/- cells: LTR-retrotransposons, LINE-1 repeats and mouse satellites. RNA-seq experiments demonstrate that specific IAP (Intracisternal A-type particle) LTRs and satellites, but not LINE-1 elements, are aberrantly transcribed inLsh-/- cells. LTR hypomethylation in Dnmt3b-/- cells is moderate and hypomethylated repetitive elements (IAP, LINE-1 and satellite) are silent. Chromatin immunoprecipitation (ChIP) indicates that repressed LINE-1 elements gain H3K4me3, but H3K9me3 levels are unaltered in Lsh-/- cells, indicating that DNA hypomethylation alone is not permissive for their transcriptional activation. Mis-expressed IAPs and satellites lose H3K9me3 and gain H3K4me3 in Lsh-/- cells. Conclusions: Our study emphasizes that regulation of repetitive elements by DNA methylation is selective and context dependent. We propose a model where Lsh is specifically required at a precise developmental window to target de novo methylation to repeat sequences, which is subsequently maintained by Dnmt1 in somatic cells to enforce repeat silencing thus contributing to genomic integrity. Two pairs of RNA samples compared: WT and Lsh-/- RNA isolations from tail-tip fibroblasts; WT and Lsh-/- RNA isolations from E13.5 mouse embryos.

Project description:Background: Global DNA methylation contributes to genomic integrity by supressing repeat associated transposition events. Several chromatin factors are required in addition to DNA methyltransferases to maintain DNA methylation at intergenic and satellite repeats. Embryos lacking Lsh, a member of the SNF2 superfamily of chromatin helicases, are hypomethylated. The interaction of Lsh with the de novo methyltransferase, Dnmt3b, facilitates the deposition of DNA methylation at stem cell genes. We wished to determine if a similar targeting mechanism operates to maintain DNA methylation at repetitive sequences. Results: We used HELP-seq to map genome wide DNA methylation patterns in Lsh-/- and Dnmt3b-/- somatic cells. DNA methylation is predominantly lost from specific genomic repeats in Lsh-/- cells: LTR-retrotransposons, LINE-1 repeats and mouse satellites. RNA-seq experiments demonstrate that specific IAP (Intracisternal A-type particle) LTRs and satellites, but not LINE-1 elements, are aberrantly transcribed inLsh-/- cells. LTR hypomethylation in Dnmt3b-/- cells is moderate and hypomethylated repetitive elements (IAP, LINE-1 and satellite) are silent. Chromatin immunoprecipitation (ChIP) indicates that repressed LINE-1 elements gain H3K4me3, but H3K9me3 levels are unaltered in Lsh-/- cells, indicating that DNA hypomethylation alone is not permissive for their transcriptional activation. Mis-expressed IAPs and satellites lose H3K9me3 and gain H3K4me3 in Lsh-/- cells. Conclusions: Our study emphasizes that regulation of repetitive elements by DNA methylation is selective and context dependent. We propose a model where Lsh is specifically required at a precise developmental window to target de novo methylation to repeat sequences, which is subsequently maintained by Dnmt1 in somatic cells to enforce repeat silencing thus contributing to genomic integrity. Two pairs of genomic samples compared: WT and Lsh-/- DNA isolations from tail-tip fibroblasts; WT and Dnmt3b knockout DNA isolations from mouse embryonic fibroblasts.

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In human sperm, H4K20me3 is abundantly preserved in retrotransposons, satellite repeats and olfactory genes, and maintains herewith the somatic-like pattern

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