Evidence for conserved DNA and histone H3 methylation reprogramming in mouse, bovine and rabbit zygotes

Background: In mammals the parental genomes are epigenetically
reprogrammed after fertilization. This reprogramming includes a
rapid demethylation of the paternal (sperm-derived) chromosomes
prior to DNA replication in zygotes. Such active DNA demethylation
in the zygote has been documented for several mammalian species,
including mouse, rat, pig, human and cow, but questioned to occur
in rabbit. Results: When comparing immunohistochemical patterns of
antibodies against 5-methyl-cytosine, H3K4me3 and H3K9me2
modifications we observe similar pronuclear distribution and
dynamics in mouse, bovine and rabbit zygotes. In rabbit DNA
demethylation of the paternal chromosomes occurs at slightly
advanced pronuclear stages. We also show that the rabbit oocyte
rapidly demethylates DNA of donor fibroblast after nuclear
transfer. Conclusion: Our data reveal that major events of
epigenetic reprogramming during pronuclear maturation, including
mechanisms of active DNA demethylation, are apparently conserved
among mammalian species.