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Published on: November 11, 2022
Behavior of Assembled Promyelocytic Leukemia Nuclear Bodies upon Asymmetric Division in Mouse Oocytes
Osamu Udagawa1, Ayaka Kato-Udagawa1, Seishiro Hirano1
1Environmental Risk and Health Research Division, National Institute for Environmental Studies, Tsukuba 305-8506, Japan.
Abstract:
Promyelocytic leukemia (PML) nuclear bodies (PML-NBs) are core-shell-type membrane-less organelles typically found in the nucleus of mammalian somatic cells but are absent in mouse oocytes. Here, we deliberately induced the assembly of PML-NBs by injecting mRNA encoding human PML protein (hPML VI -sfGFP) into oocytes and investigated their impact on fertilization in which oocyte/embryos undergo multiple types of stresses. Following nuclear membrane breakdown, preassembled hPML VI -sfGFP mRNA-derived PML-NBs (hmdPML-NBs) persisted in the cytoplasm of oocytes, forming less-soluble debris, particularly under stress. Parthenogenetic embryos that successfully formed pronuclei were capable of removing preassembled hmdPML-NBs from the cytoplasm while forming new hmdPML-NBs in the pronucleus. These observations highlight the beneficial aspect of the PML-NB-free nucleoplasmic environment and suggest that the ability to eliminate unnecessary materials in the cytoplasm of metaphase oocytes serves as a potential indicator of the oocyte quality.
Insights
Promyelocytic leukemia nuclear bodies (PML-NBs) induced in mouse oocytes persisted in cytoplasm under stress. Embryos cleared these bodies, indicating cytoplasmic clearance is key for oocyte quality and successful fertilization.
Area of Science:
- Cell Biology
- Reproductive Biology
Background:
- Promyelocytic leukemia nuclear bodies (PML-NBs) are nuclear organelles absent in mouse oocytes.
- Oocytes face significant stress during fertilization and early development.
Purpose of the Study:
- To investigate the impact of induced PML-NBs on mouse oocyte fertilization under stress.
- To assess the behavior and clearance of PML-NBs during early embryonic development.
Main Methods:
- Injected mRNA encoding human PML protein (hPML VI -sfGFP) into mouse oocytes to induce PML-NB formation.
- Observed PML-NB behavior in oocytes and early embryos, particularly under stress conditions.
- Utilized parthenogenetic activation to study early embryonic development and PML-NB clearance.
Main Results:
- Induced PML-NBs (hmdPML-NBs) persisted in the oocyte cytoplasm, forming debris, especially under stress.
- Parthenogenetic embryos cleared preassembled hmdPML-NBs from the cytoplasm.
- New hmdPML-NBs were formed within the pronucleus of developing embryos.
Conclusions:
- A PML-NB-free nucleoplasmic environment is beneficial for oocyte function.
- The ability of oocytes to clear cytoplasmic material is a potential indicator of oocyte quality.
- PML-NB dynamics offer insights into oocyte resilience and developmental competence.
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