Protein inside egg cells protects chromosome cohesion throughout reproductive life in mice
Female fertility has an expiry date that starts ticking at birth. But how egg cells survive intact for decades has been unclear until now. Researchers identified a protein that plays a key role in mice.
Human egg cells are formed during fetal development. They then lie dormant for decades until ovulation activates them. During that dormancy, chromosomes must stay intact. This is managed through a system that holds chromosomes together (cohesin complexes containing the protein REC8). But REC8 is not replenished. How egg cells protect this system was unknown.
An oocyte-specific protective protein
The researchers identified a previously unknown protein called OMC1, found exclusively in egg cells. OMC1 binds to REC8-cohesin complexes on the chromosome axis from fetal stages onward. In mice with the OMC1 gene knocked out, chromosome cohesion deteriorated faster. This led to more errors during egg cell division, in particular a higher rate of incorrect chromosome distribution (aneuploidy).
Such chromosome errors increase naturally as women age. They are a leading cause of infertility, miscarriage, and congenital conditions such as Down syndrome. The study, published in Nature Aging, shows that OMC1 suppresses this aging process in egg cells.
From mouse to human
Whether OMC1 plays the same role in humans was not investigated in this study. The protein is present in human tissue, but whether its function is identical remains to be established. The researchers describe their findings as evidence of the molecular basis that helps determine the duration of female fertility.
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