Meiotic Mechanisms in Oocyte Aneuploidy

Oocyte aneuploidy arises when the specialised cell divisions of meiosis fail to allocate the correct complement of chromosomes to the egg. In meiosis I, homologous chromosomes form bivalents through crossover recombination and remain connected by cohesin complexes until anaphase onset. Accurate kinetochore–microtubule attachments and a robust spindle assembly checkpoint ensure proper tension and alignment. Species-specific chromosome architecture, age-related depletion of cohesion, altered spindle dynamics and declining proteostasis converge to undermine these safeguards. As women age, weakening of centromeric cohesion and increased kinetochore misorientation promote sister chromatid separation or univalent formation. Actin networks within the oocyte also counteract microtubule-driven dispersion of chromatids, while long-lived proteins in the ovarian environment preserve chromosomal integrity over decades. Failure of any of these mechanisms leads to eggs with missing or extra chromosomes, the predominant cause of human miscarriage, infertility and developmental syndromes such as Down syndrome.

Research from Nature Portfolio

Recent studies have revealed that the linear configuration of chromosomes influences missegregation rates. Acrocentric chromosomes, characterised by centromeres close to one end, bind kinetochores that are partially obscured by short arms, reducing proper spindle attachment and rendering these chromosomes particularly vulnerable to age-associated cohesion loss. This architecture bias helps to explain the disproportionate incidence of trisomy for certain chromosomes. In parallel, large-scale proteome analyses have shown that oocytes and surrounding somatic cells maintain an exceptionally long-lived complement of proteins involved in chromatin structure, cohesion and antioxidant defence. Although protein longevity and enhanced chaperone activity preserve oocyte function for many years, progressive remodelling of the proteostasis network eventually compromises cohesion maintenance and contributes to the decline in female fertility.

Meiotic Mechanisms in Oocyte Aneuploidy publication trend

The graph below shows the total number of articles in meiotic mechanisms in oocyte aneuploidy across all publications each year (not limited to Nature Index journals).

Technical terms

Aneuploidy: The state of having an abnormal number of chromosomes, often leading to developmental arrest or disease.

Cohesin: A ring-shaped protein complex that holds sister chromatids or homologous chromosomes together until their timely separation in meiosis.

Kinetochore: A multiprotein assembly at the chromosome centromere that mediates attachment to spindle microtubules.

Bivalent: A pair of homologous chromosomes joined by crossover recombination during the first meiotic division.

Univalent: A single chromosome that has lost its homologue pairing, increasing the risk of missegregation.

References

1. Chromosome architecture and low cohesion bias acrocentric chromosomes towards aneuploidy during mammalian meiosis. Nature Communications (2024).
2. The maintenance of oocytes in the mammalian ovary involves extreme protein longevity. Nature Cell Biology (2024).
3. Actin limits egg aneuploidies associated with female reproductive aging. Science Advances (2023).
4. Ectopic expression of human TUBB8 leads to increased aneuploidy in mouse oocytes. Cell Discovery (2023).