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Updated: Jan 24, 2026
10:08
Determining the Role of Maternally-Expressed Genes in Early Development with Maternal Crispants
Published on: December 21, 2021
2.6K
EHMT2 and SETDB1 protect the maternal pronucleus from 5mC oxidation
Tie-Bo Zeng1, Li Han1, Nicholas Pierce1
1Center for Epigenetics, Van Andel Research Institute, Grand Rapids, MI 49503.
Summary
Oocyte enzymes EHMT2 and SETDB1 regulate DNA demethylation asymmetry in zygotes. Maternal mutations in these genes disrupt 5-methylcytosine oxidation and affect zygote development.
Area of Science:
- Epigenetics
- Developmental Biology
- Genetics
Background:
- Genome-wide DNA demethylation in zygotes involves TET3-mediated oxidation of 5-methylcytosine (5mC).
- Asymmetric histone H3K9 methylation in the maternal pronucleus is proposed to protect DNA from 5mC conversion.
Purpose of the Study:
- To investigate the role of oocyte-expressed H3K9 methyltransferases (EHMT2 or SETDB1) in specifying the asymmetry of 5mC oxidation.
- To determine the impact of EHMT2 and SETDB1 on DNA demethylation and zygote structural development.
Main Methods:
- Genetic deletion of the catalytic domain of EHMT2 or SETDB1 in growing oocytes.
- Analysis of global H3K9 methylation levels (H3K9me2, H3K9me3) in maternal pronuclei.
- Quantification of 5mC and its oxidation products (5hmC, 5fC, 5caC) in zygotes.
- Assessment of maternal pronuclei size and nucleolar-like body number.
Main Results:
- Maternal mutations in Ehmt2 or Setdb1 significantly reduced H3K9me2 or H3K9me3 levels and the asymmetry of global 5mC oxidation.
- Mutant maternal pronuclei showed increased 5hmC, 5fC, and 5caC levels, and decreased 5mC.
- H3K9me3-rich regions retained 5mC, indicating independent protection of pericentromeric heterochromatin.
- Maternal pronuclei expanded and contained more nucleolar-like bodies in mutant zygotes.
Conclusions:
- Oocyte-derived EHMT2 and SETDB1 are crucial for regulating the asymmetry of 5mC oxidation in the zygote.
- These enzymes also play a role in the structural organization of the zygote, including maternal pronuclei expansion and nucleolar-like body formation.
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