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Analyzing Eggs and their Genetic Junk Offers Clues to Fertility

Time,  Nov 1, 2010
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We know that egg + sperm = baby, but the nitty-gritty of how women get pregnant is largely a mystery. Now researchers at Brown University have discovered a new way to gather more information about egg cells: by sifting through their genetic junk. Eventually, this kind of expanded knowledge could lead to new forms of contraception and the ability to detect which eggs are prime candidates for fertilization.

How does this work? Think back to what you learned about meiosis in high school biology: eggs undergo a process of chromosome division, splitting into a small cell — the polar body — and a larger one, which is the actual egg.

Scientists aren't sure why the polar body exists, though they think it's essentially a trash can for the extra chromosomes not needed by the egg. But the Brown researchers told colleagues at last week's American Society for Reproductive Medicine annual meeting that they have identified messenger RNA (mRNA), which makes the genetic code function, in the polar bodies. But wait: if polar bodies were simply biological landfills, there would be no need for mRNA. Something didn't jibe.

Scientists are already able to remove polar bodies and look at their DNA to see if the genes look normal. But DNA doesn't reveal anything about the function of the genes; mRNA does. The researchers eventually hope to be able to analyze eggs' mRNA to determine if it's normal or abnormal. If something's askew in a particular egg's polar body, it could be a biologic clue indicating that egg isn't likely to successfully fertilize. When it comes to pricey assisted reproduction techniques such as in vitro fertilization, knowing which eggs have a better chance of uniting with sperm to yield a baby would be welcome news for would-be parents and fertility docs.

“We are excited because this provides a window into egg development,” says Sandra Carson, one of the lead researchers and a Brown professor of obstetrics and gynecology who is also director of the Division of Reproductive Endocrinology and Infertility at Women and Infants Hospital of Rhode Island. “If we can fully understand egg development, we can learn how to control it.”

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