The wisdom of the egg cell: Oocyte epigenetic mark may help prevent excessive placental growth after fertilization
The genome—which contains genes encoded in DNA—acts as the fundamental blueprint of life. But what you might not know is that, in addition to this genetic information, we have something akin to an "instruction manual" for how genes should be handled. This instruction manual is known as the epigenome.
The epigenome, akin to an instruction manual, guides how genes are handled within organisms. Azusa Inoue, team director at the RIKEN Center for Integrative Medical Science, is studying this epigenome's role in egg cells, or oocytes, during fertilization and placenta development. The epigenome comprises chemical modifications to DNA or associated proteins, known as DNA methylation and histone modification, with histone modification being a focus of Inoue's research.
H3K27me3, a histone modification inhibiting gene activity, was discovered by Inoue in 2017 to be transmitted from the oocyte to the next generation. This mark influences embryonic development and placental formation. During oocyte maturation, H2Aub and H3K4me3 precede H3K27me3. The team found that H2Aub silences active genes, enabling H3K27me3 establishment.
This epigenomic mark regulates placental growth after fertilization; its absence leads to excessive placental growth, which could burden the mother. Intriguingly, the oocyte encodes information relevant later in life, even before fertilization.
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