235: Maternal H3K9 methyltransferases control aRMAE in C. elegans

Sands et al., Nature Communications - Using dual-color reporters in C. elegans, the study shows maternal H3K9 methyltransferases MET-2 and SET-25 antagonistically regulate autosomal random monoallelic expression initiated in the early embryo. Key terms: histone-methyltransferase, aRMAE, MET-2, SET-25, c-elegans.

Study Highlights:
Dual-color fluorescent reporter alleles in C. elegans intestine cells enabled single-cell quantification of allele expression and a targeted screen for aRMAE regulators. MET-2/SETDB1, with LIN-65 and ARLE-14, acts maternally in the 8-cell E-cell to prevent monoallelic expression, while SET-25/SUV39 with HPL-2 and LIN-61 promotes allele silencing. Catalytic SET domains of both MET-2 and SET-25 are required for their opposing activities, and loss of MET-2 increases persistent but non-heritable monoallelic expression whereas loss of SET-25 causes biallelic expression. Reciprocal crosses and genetic interactions indicate these maternal H3K9 HMTs set early embryonic histone states that are propagated through somatic divisions to shape tissue-wide allele expression.

Conclusion:
Maternal MET-2 and SET-25 establish competing H3K9-related chromatin states in the early embryo that bias autosomal alleles toward persistent somatic monoallelic or biallelic expression

Music:
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Article title:
Maternal histone methyltransferases antagonistically regulate autosomal random monoallelic expression (aRMAE) in C. elegans

First author:
Sands

Journal:
Nature Communications

DOI:
10.1038/s41467-025-66501-5

Reference:
Sands, B., Yun, S.R., Oshima, J. et al. Maternal histone methyltransferases antagonistically regulate autosomal random monoallelic expression (aRMAE) in C. elegans. Nat Commun (2025). https://doi.org/10.1038/s41467-025-66501-5

License:
CC BY 4.0 International License

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QC:
This episode was checked against the original article PDF and publication metadata for the episode release published on 2025-12-21.

QC Scope:
- article metadata and core scientific claims from the narration
- excludes analogies, intro/outro, and music
- transcript coverage: Audited transcript sections describing MAE basics, the C. elegans reporter MAE assay, intrinsic noise as a MAE metric, the MET-2/SET-25 antagonism and cofactors, maternal deposition in the E-cell, catalytic SET-domain requirements, cross experiments, gene specificity, and translational implications.
- transcript topics: Introduction to autosomal random monoallelic expression (aRMAE); C. elegans MAE reporter system with dual-color alleles (hsp-90); Intrinsic noise as a quantitative MAE measure; RNAi screen identifying H3K9 methyltransferases MET-2 and SET-25; Antagonistic roles of MET-2 (negative regulator) and SET-25 (positive regulator) of MAE; Cofactors LIN-65, ARLE-14, HPL-2, LIN-61

QC Summary:
- factual score: 10/10
- metadata score: 10/10
- supported core claims: 8
- claims flagged for review: 0
- metadata checks passed: 4
- metadata issues found: 0

Metadata Audited:
- article_doi
- article_title
- article_journal
- license

Factual Items Audited:
- Autosomal random monoallelic expression (aRMAE) is probabilistic, persistent within a tissue, but not heritable across generations.
- In C. elegans intestine, maternal MET-2 antagonizes SET-25 to regulate MAE; MET-2 promotes biallelic expression while SET-25 promotes monoallelic expression.
- Catalytic SET domains of MET-2 and SET-25 are required for their regulatory effects on MAE.
- Maternal MET-2 and SET-25 act in the E-cell of the 8-cell embryo to regulate MAE; the decision is propagated through somatic divisions but is not heritable.
- Cofactors LIN-65 and ARLE-14 support MET-2; HPL-2 and LIN-61 support SET-25 function.
- MAE regulation is gene-specific; not all MAE-prone genes respond similarly to MET-2 perturbation (e.g., hsp-90 vs vit-2).

QC result: Pass.