bims-mazytr 2025-06-22 papers

Issue of 2025–06–22
four papers selected by
川一刀

Nat Struct Mol Biol. 2025 Jun 13.

H2A.Z is essential for oocyte maturation and fertility in female mouse.

Qianhua Xu, Chunyi Huang, Jia Ming, Xukun Lu, Ling Liu, Zhenhai Du, Zhen Chen, Jie Na, Guohong Li, Yunlong Xiang, Yu Zhang, Wei Xie.

Oocyte maturation is essential for both gametogenesis and early development, when large amounts of transcripts are produced without DNA replication. Histone variants, which can be incorporated at cis-regulatory elements in a replication-independent manner, are naturally suited for such regulation. However, their roles during mammalian oocyte maturation remain elusive. Here we show that oocyte-specific depletion of H2A.Z, an evolutionarily conserved histone variant, in female mice results in profound epigenetic and transcriptional alterations, impedes resumption of oocyte meiosis II and causes infertility. Mechanistically, H2A.Z in mouse oocytes is incorporated into chromatin at active promoters and putative enhancers. Interestingly, H2A.Z is depleted from CG-rich silenced promoters, including poised Polycomb target genes, in fully grown oocytes (FGOs), unlike what occurs in growing oocytes, early embryos and mouse embryonic stem cells. In FGOs, the presence of H2A.Z correlates with histone acetylation, except in regions marked by DNA methylation and H3K36me3. Depletion of H2A.Z leads to impaired activities of a subset of promoters and enhancers, correlated with defective gene expression. Consistent with a role in gene activation, H2A.Z in FGOs is widely acetylated at the promoters and enhancers. Together, our findings uncover an essential role of H2A.Z in mammalian oocyte maturation and female fertility.

DOI: https://doi.org/10.1038/s41594-025-01580-y

Nat Struct Mol Biol. 2025 Jun 13.

H2A.Z reinforces maternal H3K4me3 formation and is essential for meiotic progression in mouse oocytes.

Hailiang Mei, Ryoya Hayashi, Chisayo Kozuka, Mami Kumon, Haruhiko Koseki, Azusa Inoue.

Mammalian oocytes establish a unique landscape of histone modifications, some of which are inherited by early embryos. How histone variants shape the maternal histone landscape remains unknown. Here we map histone H2A variants in mouse fully grown oocytes (FGOs) and find that H2A.Z forms broad domains across intergenic regions, along non-canonical H3K4me3 (ncH3K4me3). During oocyte growth, H2A.Z progressively transitions from an active promoter-rich, canonical distribution to a non-canonical broad distribution (ncH2A.Z). Depletion of H2A.Z in oocytes partially impairs ncH3K4me3 formation and causes severe defects in meiotic progression, which resemble Mll2-knockout oocytes. Conversely, depletion of ncH3K4me3 by Mll2 knockout also causes a reduction of ncH2A.Z in FGOs. Thus, our study suggests that ncH2A.Z and ncH3K4me3 reinforce each other to form functional oocytes.

DOI: https://doi.org/10.1038/s41594-025-01573-x

Nat Cell Biol. 2025 Jun;27(6): 959-971

Cell state-specific cytoplasmic density controls spindle architecture and scaling.

Tobias Kletter, Omar Muñoz, Sebastian Reusch, Abin Biswas, Aliaksandr Halavatyi, Beate Neumann, Benno Kuropka, Vasily Zaburdaev, Simone Reber.

Mitotic spindles are dynamically intertwined with the cytoplasm they assemble in. How the physicochemical properties of the cytoplasm affect spindle architecture and size remains largely unknown. Using quantitative biochemistry in combination with adaptive feedback microscopy, we investigated mitotic cell and spindle morphology during neural differentiation of embryonic stem cells. While tubulin biochemistry and microtubule dynamics remained unchanged, spindles changed their scaling behaviour; in differentiating cells, spindles were considerably smaller than those in equally sized undifferentiated stem cells. Integrating quantitative phase imaging, biophysical perturbations and theory, we found that as cells differentiated, their cytoplasm became more dilute. The concomitant decrease in free tubulin activated CPAP (centrosomal P4.1-associated protein) to enhance the centrosomal nucleation capacity. As a consequence, in differentiating cells, microtubule mass shifted towards spindle poles at the expense of the spindle bulk, explaining the differentiation-associated switch in spindle architecture. This study shows that cell state-specific cytoplasmic density tunes mitotic spindle architecture. Thus, we reveal physical properties of the cytoplasm as a major determinant in organelle size control.

DOI: https://doi.org/10.1038/s41556-025-01678-x