In a study that could change the prospects for the 1 in 15 infertile couples worldwide, researchers in China and the US show how their way of finding genetic defects in egg cells could double the success rate of the reproductive treatment in vitro fertilization.
The new method, based on whole-genome sequencing of individual egg cells, could lead to an accurate, safe and cheap way to select genetically normal embryos for in vitro fertilization (IVF), thus increasing the chances of producing a healthy baby.
As well as looking for DNA sequence variations associated with known genetic disorders, the new approach detects chromosome abnormalities.
Study author Jie Qiao, department director and professor of Gynecology and Obstetrics, Peking University, 3rd Hospital, says:
"In this way, we kill two birds with one stone: one set of deep sequencing analysis to avoid two types of genetic problems."
"Theoretically, if this works perfectly, we will be able to double the success rate of test tube baby technology from 30% to 60% or even more."
The researchers write about their work in a recent online issue of the journal Cell.
New approach sequences whole genome of 'polar bodies'
In IVF, an egg from the woman is fertilized with sperm from the man in a "test tube," and the embryos are then implanted in the woman's uterus.
There are several ways to screen the embryos for genetic defects before implantation, but these carry risks because they involve removing cells from the embryo. Also, they do not detect chromosome abnormalities and genetic disorders based on DNA sequence variations at the same time.
Although whole-genome sequencing has recently been developed for screening sperm cells, until now there was not an equivalent way to apply it egg cells, despite the fact they are more likely to contain chromosome abnormalities.
In their study, the researchers developed a way of sequencing the whole of the genetic code of "polar bodies" - cells that emerge when egg cells divide but then die off, so they can be safely removed without harming the embryo.
Co-author Sunney Xie, Mallinckrodt Professor of Chemistry and Chemical Biology at Harvard University in the US, and also of Peking University, says they are now starting to test their new approach in clinical trials, and:
"If the clinical trial works, this technique could enormously increase the success rate of IVF, especially for older women or women who have had recurrent miscarriages."
In another study published earlier this year, researchers showed an IVF technique that increased pregnancy rates by 20%. The procedure, known as endometrial scratching, improved both pregnancy and birth rates when performed once in women undergoing reproductive treatment.
Written by Catharine Paddock PhD
