Developmental pattern of gene-specific DNA methylation in the mouse embryo and germ line.

TLDR

Gene‑specific methylation patterns change dynamically during germ line development and early embryogenesis. The mature germ cell methylation profile is established through a multistep, site‑specific demethylation sequence. CpG sites exhibit parental‑specific methylation that is erased and re‑established during early embryogenesis and gametogenesis, with remodification completed by 18.5 dpc, illuminating DNA methylation’s role in development.

Abstract

Methylation patterns of specific genes have been studied by polymerase chain reaction and found to undergo dynamic changes in the germ line and early embryo. Some CpG sites are methylated in sperm DNA and unmodified in mature oocytes, indicating that the parental genomes have differential methylation profiles. These differences, however, are erased by a series of early embryonic demethylation and postblastula remodification events, which serve to reestablish the basic adult methylation pattern prior to organogenesis. During gametogenesis, all of these sites are unmethylated in primordial germ cells but eventually become remodified by 18.5 days postcoitum in both males and females. The final methylation profile of the mature germ cells is then formed by a multistep process of site-specific demethylation events. These results form a basis for the understanding of the biochemical mechanisms and role of DNA methylation in embryonic development.