How egg cells handle their cellular rubbish: The discovery of a molecular recycling system in mouse oocytes might help scientists to understand why fertility declines with age

 

"Mouse egg cells contain specialized ‘recycling bins’ that help to keep cells tidy before fertilization1.

 

All cells must cope with misfolded and clumped proteins that can pollute the cellular interior, or cytoplasm. But this is a particular problem for immature egg cells, called oocytes, which must survive for years awaiting fertilization.

 

To see how mouse eggs deal with their rubbish, Gabriele Zaffagnini at the Centre for Genomic Regulation in Barcelona, Spain, and his colleagues looked for protein clumps in oocytes as well as in mature eggs and developing embryos.

 

In oocytes, the researchers discovered specialized structures containing protein clumps as well as cellular machinery that recycles proteins. The authors observed that this machinery kicks into gear when eggs mature, just before ovulation and fertilization. Blocking this process in oocytes led to defective eggs and, in early-stage embryos, resulted in severely disrupted development.

 

Chromosomal factors account for much of the age-related decline in fertility, but defects in protein degradation could also have a role, the researchers say." [1]

 

1. Nature 626, 931 (2024)