The prophase oocyte nucleus is a homeostatic G-actin buffer.

Kathleen Scheffler, Federica Giannini, Tom Lemonnier, Binyam Mogessie

Journal of cell science 2022 Mar 15

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Formation of healthy mammalian eggs from oocytes requires specialised F-actin structures. F-actin disruption produces aneuploid eggs, which are a leading cause of human embryo deaths, genetic disorders and infertility. We found that oocytes contain prominent nuclear F-actin structures that are correlated with meiotic developmental capacity. We demonstrate that nuclear F-actin is a conserved feature of healthy mammalian oocytes and declines significantly with female reproductive ageing. Actin monomers used for nuclear F-actin assembly are sourced from an excess pool in the oocyte cytoplasm. Increasing monomeric G-actin transfer from the cytoplasm to the nucleus or directly enriching the nucleus with monomers led to assembly of stable nuclear F-actin bundles that significantly restrict chromatin mobility. By contrast, reducing G-actin monomer transfer by blocking nuclear import triggered assembly of a dense cytoplasmic F-actin network that is incompatible with healthy oocyte development. Overall, our data suggest that the large oocyte nucleus helps to maintain cytoplasmic F-actin organisation and that defects in this function are linked with reproductive age-related female infertility. This article has an associated First Person interview with Federica Giannini, joint first author of the paper. © 2022. Published by The Company of Biologists Ltd.

Citation

Kathleen Scheffler, Federica Giannini, Tom Lemonnier, Binyam Mogessie. The prophase oocyte nucleus is a homeostatic G-actin buffer. Journal of cell science. 2022 Mar 15;135(6)