Skip to main content
. Author manuscript; available in PMC: 2016 Jun 1.
Published in final edited form as: Reproduction. 2015 Jun 1;150(3):R109–R120. doi: 10.1530/REP-15-0180

Figure 1. DNA demethylation in the zygote.

Figure 1

Distinct demethylation dynamics occur in the maternal (pink) and paternal (blue) pronuclei prior to fusion. At fertilization, the maternal haploid genome has approximately 40% methylation compared to nearly 90% methylation in the paternal haploid genome. Upon fertilization and continuing through pronuclear stage PN2, the paternal genome undergoes Tet3 dependent demethylation. PGC7, which preferentially binds to H3K9me2-rich chromatin, protects the maternal genome from Tet3 activity during PN stages. By PN5 stage, the bulk of paternal 5mC is gone and little change has occurred to maternal methylation. PPN= paternal pronucleus, MPN= maternal pronucleus.