Sister kinetochore splitting and precocious disintegration of bivalents could explain the maternal age effect
- Medical Research Council, United Kingdom
- Bourn Hall Clinic, United Kingdom
Abstract
Aneuploidy in human eggs is the leading cause of pregnancy loss and Down's syndrome. Aneuploid eggs result from chromosome segregation errors when an egg develops from a progenitor cell, called an oocyte. The mechanisms that lead to an increase in aneuploidy with advanced maternal age are largely unclear. Here, we show that many sister kinetochores in human oocytes are separated and do not behave as a single functional unit during the first meiotic division. Having separated sister kinetochores allowed bivalents to rotate by 90 degrees on the spindle and increased the risk of merotelic kinetochore-microtubule attachments. Advanced maternal age led to an increase in sister kinetochore separation, rotated bivalents and merotelic attachments. Chromosome arm cohesion was weakened, and the fraction of bivalents that precociously dissociated into univalents was increased. Together, our data reveal multiple age-related changes in chromosome architecture that could explain why oocyte aneuploidy increases with advanced maternal age.
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Ethics
Human subjects: The use of immature unfertilized human oocytes in this study has been approved by the UK's National Research Ethics Service under the REC reference 11/EE/0346; IRAS Project ID 84952. Immature unfertilized oocytes were donated by women receiving assisted reproduction treatment at Bourn Hall Clinic (Cambridge, UK).
Copyright
© 2015, Zielinska et al.
This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.
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Sister kinetochore splitting and precocious disintegration of bivalents could explain the maternal age effect
eLife 4:e11389.
https://doi.org/10.7554/eLife.11389
