Regulation of paternal 5mC oxidation and H3K9me2 asymmetry by ERK1/2 in mouse zygotes.

Background: Extracellular-signal-regulated kinase (ERK) direct cell fate determination during the early development. The intricate interaction between the deposition of H3K9me2, de novo 5mC, and its oxides affects the remodeling of zygotic epigenetic modification. However, the role of fertilization-dependent ERK in the first cell cycle during zygotic reprogramming remains elusive.

Methods: In the present study, we used the small molecule inhibitor to construct the rapid ERK1/2 inactivation system in early zygotes in mice. The pronuclear H3K9me2 deposition assay and the pre-implantation embryonic development ability were assessed to investigate the effect of fertilization-dependent ERK1/2 on zygotic reprogramming and developmental potential. Immunofluorescence and RT-PCR were performed to measure the 5mC or its oxides and H3K9me2 deposition, and the expression of related genes.

Results: We reported that zygotic ERK1/2 inhibition impaired the development competence of pre-implantation embryos. Following the ERK1/2 inhibition, H3K9me2, as well as 5mC and its oxides, were all accumulated abnormally, and the excess accumulation of paternal H3K9me2 and 5mC resulted in reduced asymmetry between parental pronuclei. Furthermore, ERK1/2 inhibition triggered paternal pronuclear localization of the H3K9 methyltransferase G9a and Tet methylcytosine dioxygenase 3 (Tet3). Moreover, the excess localization of G9a antagonized the tight binding of Tet3 to paternal chromatin when ERK1/2 was inhibited.

Conclusions: In conclusion, we propose that zygotic H3K9me2 and 5mC are regulated by fertilization-dependent ERK1/2, which contributes to the development competence of pre-implantation embryos in mice.