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While investigating how egg cells die, researchers from Melbourne have apparently discovered a new way for protecting female fertility. The discovery offers hope to those women whose fertility may be compromised by the side-effects of cancer therapy or by premature menopause.

The researchers, from the Walter and Eliza Hall Institute, Monash University and Prince Henry's Institute of Medical Research, have found two specific proteins, called PUMA and NOXA, which are responsible for the death of egg cells in the ovaries. It may be possible to protect women's fertility by blocking the activity of these two proteins.

According to Associate Professor Clare Scott from the Walter and Eliza Hall Institute, when DNA of egg cells is exposed to radiation or chemotherapy, they get damaged. The proteins PUMA and NOXA trigger the death of the damaged eggs and this causes many a female cancer patients to become infertile.

"PUMA and NOXA can trigger cell death, and have been found to be necessary for the death of many different cell types in response to DNA damage," said Scott, who is also an oncologist at The Royal Melbourne and Royal Women's Hospitals. "This removal of damaged cells is a natural process that is essential to maintaining health but, for women undergoing cancer treatment, can be devastating when it leads to infertility."

The researchers for this study, focused on egg cells called primordial follicle oocytes, which provide each woman's lifetime supply of eggs and a lower number of these cells could cause early menopause in women.

Associate Professor Jeff Kerr from Monash University said that when the egg-producing cells were missing the PUMA protein, they did not die after being exposed to radiation therapy.

"This might ordinarily be cause for concern because you want damaged egg cells to die so as not to produce abnormal offspring," he said. "To our great surprise we found that not only did the cells survive being irradiated, they were able to repair the DNA damage they had sustained and could be ovulated and fertilized, producing healthy offspring. When the cells were also missing the NOXA protein, there was even better protection against radiation."

"We were very excited to see healthy offspring could be produced from these cells," Scott said. "It means that in the future, medications that block the function of PUMA could be used to stop the death of egg cells in patients undergoing chemotherapy or radiotherapy. Our results suggest that this could maintain the fertility of these patients."

"We know that the timing of menopause is influenced by how many egg cells a female has," said Professor Jock Findlay, joint leader of the study and head of the Female Reproductive Biology Group at Prince Henry's Institute.

"Interventions that slow the loss of egg cells from the ovaries could delay premature menopause. As well as prolonging female fertility, such a treatment could have the potential to reduce menopause-associated health conditions, such as osteoporosis and heart disease."

Their findings are published online this week in the journal Molecular Cell.