A multi-scale study of bovine sperm methyloma reveals conserved elements between species, but also particularities of the bovine genome.

The BDR unit in partnership with Allice conducted a multi-scale study of DNA methylation in bovine sperm compared to other cell types and species. bmcgenomics.biomedcentral.com
Semen methyloma was compared with adult somatic cells (fibroblasts, liver, monocytes) using two pan-genomic approaches covering different regions of the genome: SBRRN and MeDIP-chip (immunoprecipitation of methylated DNA and hybridization on a bovine promoter chip). Two independent sets of differentially methylated sequences in sperm cells in relation to somatic cells could thus be identified. In both sets, a large majority of these sequences are found hypomethylated in the sperm cells. As described in other species, the specifically hypomethylated sequences in sperm are enriched with genes for meiosis and spermatogenesis, piRNA production machinery, as well as satellite repeats. More unexpectedly, the comparison with sperm from other species (rams, goats, stallions, boars, male mice and humans) showed that overall DNA methylation was particularly low in bovine sperm (45.5% versus 57.1% to 76.1% for other species), mirroring a rate of satellite sequences particularly abundant at LUMA target sites. The over-representation of these sequences in the bovine genome, as well as their hypomethylation, may explain why bovine sperm have a lower overall methylation rate than sperm from other mammalian species.
The originality of this work was to extend to the bovine genome the available knowledge on sperm of different species, and to show that satellite sequences, which are only partially demethylated during epigenetic reprogramming of the male germ line in humans and mice, have a very low level of methylation in bovine sperm. These results suggest that bovine species-specific mechanisms are at work for the reprogramming or maintenance of methylation in the male germ line.
Jean-Philippe Perrier, Eli Sellem, Audrey Prézelin, Maxime Gasselin, Luc Jouneau, François Piumi, Hala Al Adhami, Michaël Weber, Sébastien Fritz, Didier Boichard, Chrystelle Le Danvic, Laurent Schibler, Hélène Jammes and Hélène Kiefer. A multi-scale analysis of bull sperm methyloma revealed both species peculiarities and conserved tissue-specific features. BMC Genomics 2018, 19(1):404.
Financing:
ANR-13-LAB3-0008-01, Labcom "SeQuaMol" and ANR-11-INBS-0003, "CRB-Anim".