Meiotic Spindle Dynamics in Mammalian Oocytes

Meiotic spindle dynamics in mammalian oocytes underpin the accurate segregation of homologous chromosomes during the specialised division that produces eggs. Unlike mitotic cells, oocytes assemble a bipolar spindle without canonical centrosomes, instead relying on acentriolar microtubule organising centres (MTOCs) that fragment, sort and coalesce to form two functional poles. Actin filaments further interact with microtubules to guide spindle positioning and maintain stability. Precise coordination of motor proteins, kinases and structural cross-linkers ensures polar body extrusion and reductional division. Failures in these processes lead to aneuploidy, with profound implications for fertility and developmental competence. Recent advances reveal the interplay between organelle dynamics, post-translational modifications and checkpoint controls that guard meiotic fidelity, highlighting both conserved mechanisms and oocyte-specific adaptations.

Research from Nature Portfolio

Studies of human oocytes have demonstrated that actin filaments are integral to spindle morphogenesis, forming a dynamic scaffold that liaises with microtubules throughout assembly, migration and polar body extrusion. Disruption of actin–microtubule interplay leads to spindle instability and chromosome alignment errors, underscoring its essential role in safeguarding genomic integrity.

Investigations in mouse oocytes have revealed an oocyte-specific function of kinetochores in driving acentrosomal spindle bipolarisation during meiosis I. Enrichment of the antiparallel microtubule cross-linker Prc1 at kinetochores promotes pole formation and prevents segregation errors, a mechanism that appears attenuated in human oocytes and may underlie their higher susceptibility to aneuploidy.

A foundational study delineated a three-step fragmentation of multiple acentriolar MTOCs in mouse oocytes: PLK1-mediated decondensation, dynein-driven stretching and KIF11-facilitated splitting. This orchestrated process generates numerous microtubule-nucleating foci that subsequently cluster into two poles, providing a blueprint for bipolar spindle assembly in the absence of centrosomes.

Meiotic Spindle Dynamics in Mammalian Oocytes publication trend

The graph below shows the total number of articles in meiotic spindle dynamics in mammalian oocytes across all publications each year (not limited to Nature Index journals).

Technical terms

Acentriolar MTOC: Microtubule-organising centre lacking centrioles, nucleates microtubules in oocytes.

Spindle assembly checkpoint (SAC): Surveillance mechanism that delays anaphase until all chromosomes are correctly attached to spindle microtubules.

Kinetochore: Protein complex on centromeric DNA that mediates chromosome–microtubule attachment.

Polar body extrusion: Asymmetric cytokinesis in oocytes that expels excess chromosomes into a small cell (polar body).

Microtubule nucleation: Initiation of microtubule polymerisation from γ-tubulin-rich sites in MTOCs.

Chromosomal congression: Alignment of chromosomes at the spindle equator prior to segregation.

References

1. Actin-microtubule interplay coordinates spindle assembly in human oocytes. Nature Communications (2019).
2. Prc1-rich kinetochores are required for error-free acentrosomal spindle bipolarization during meiosis I in mouse oocytes. Nature Communications (2020).
3. A three-step MTOC fragmentation mechanism facilitates bipolar spindle assembly in mouse oocytes. Nature Communications (2015).
4. Arf1 GTPase Regulates Golgi‐Dependent G2/M Transition and Spindle Organization in Oocyte Meiosis. Advanced Science (2023).
5. Kinesin KIFC3 is essential for microtubule stability and cytokinesis in oocyte meiosis. Cell Communication and Signaling (2024).
6. Kinesin KIF3A regulates meiotic progression and spindle assembly in oocyte meiosis. Cellular and Molecular Life Sciences (2024).