DNA methylation reprogramming in medaka fish, a promising animal model for environmental epigenetics research

DNA methylation is a major epigenetic modification that undergoes dramatic changes in two epigenetic reprogramming windows during development: first in preimplantation embryos and second in primordial germcell (PGC) specification. In both windows, DNA methylation patterns are reprogrammed genome-wide, and the majority of inherited methylation marks are erased, generating cells with broad developmental potential. Recent studies reported that the reprogramming of genome methylation in medaka is similar to human and mouse, suggesting that medaka may serve as a suitable biomedical model for comparative studies focused on the epigenetic and transgenerational inheritance of phenotypic traits. In this mini review, we will discuss how somatic and germcells in post-fertilization stage embryos are epigenetically reprogrammed in mammals and fishes with a particular focus on DNA methylation dynamics.