For women to be fertile during most of their lives it is important that the great majority of their primary follicles lie ‘dormant’ or inactive in the ovaries. Menopause occurs when all of the primary follicles have reached maturity and no more eggs are available for ovulation. The mechanisms that control the early activation of these dormant follicles, that is, when they are stimulate to begin to grow and mature, have been unknown until now.
Kui Liu’s research team at the Department of Medical Chemistry and Biophysics, Umeå University, can now show that the activation of follicles is governed by the signaling path PTEN-PI3K. In a mouse model where the gene that codes for the PTEN protein is inactivated specifically in egg cells, all follicles are activated prematurely and the ovary is emptied of all eggs at a young age. In a possibly similar manner the ovaries are emptied of their eggs in women who suffer from the disease premature ovarian failure (POF), which leads to the onset of menopause much earlier than normal.
This discovery is believed to be of broad physiological, clinical, and practical significance. Previously it has not been possible to use inactive primary follicles for in vitro fertilization, since it has not been possible to get them to mature when they are cultured in a laboratory. Besides the fact that these findings enhance our knowledge of what governs the length of a woman’s period of fertility, the results may also make it possible in the future to activate the maturation and grown of primary follicles in test tubes. This means that the supply of follicles for in vitro fertilization would be greater.
This would be the case not only for humans but also for pets, cattle, and threatened animal species. The discoveries are therefore important not only for the health of women but also for enhancing the fertility of animals in agriculture and for the possibility of saving animal species that are threatened with extinction and having trouble reproducing.
High resolution portrait pictures of Kui Liu are available from
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The editors of Science have also written a news article about the discovery here: