Girls are born with all the eggs they will ever need, over a million, stored in the ovaries as tiny follicles. Their complete development is suspended until reproductive age when, one by one, they develop to maturity and are released. Sometimes the control mechanisms fail, and the entire batch of eggs mature at once, leading to premature ovarian failure and infertility. Scientists don’t know exactly what triggers this, or how to stop it, but they have identified a protein in mice, called pten, that may be important. This ovary is from a mouse that has been genetically engineered to lack pten. The pale blobs are the developing eggs which all appear to have been activated prematurely. A fifth of these eggs can be saved when the mouse is injected with another protein called rapamycin. Studies like this are helping to find new approaches to preserving fertility.
Written by Emma Stoye
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