Genes ‘choose only good eggs’ for IVF

By Piriya Mahendra

Researchers have identified a technique that could help them "pick the right egg" for in vitro fertilization (IVF) treatment.

Elpida Fragouli (University of Oxford, UK) and colleagues discovered two genes that are significantly downregulated in cumulus cells, which are specialized granulosa cells that surround antral follicles and regulate egg maturation. The genes could potentially serve as noninvasive markers of oocyte aneuploidy (oocytes with abnormal chromosome numbers) and increase the likelihood for IVF success, they say in Human Reproduction.

"This finding opens up the possibility of a safe, effective, and inexpensive way of identifying healthy eggs, potentially lowering the risks of miscarriage and Down syndrome," co-author Dagan Wells (University of Oxford) commented in a press statement.

The team found that patterns of gene expression were generally similar among the 77 cumulus cell samples included in the study, regardless of the chromosomal status of their corresponding oocyte.

However, two genes, SPSB2 and TP5313, were expressed at low levels in cumulus cells that were associated with chromosomally abnormal oocytes. These genes also had relatively large messenger RNA (mRNA) copy number fluctuations, the authors note.

Upon closer analysis using focused realtime polymerase chain reaction (PCR), the researchers found that genes were expressed at low levels in the cumulus cells of aneuploid oocytes, but highly expressed in the cumulus cells associated with oocytes that had normal chromosome numbers.

Furthermore, SPSB2 was expressed more highly in cumulus cells of embryos that led to live births than in those that failed to implant.

"The identification of these genes in cumulus cells can serve as a novel, noninvasive marker to identify abnormal oocytes and thus ultimately improve IVF success rates," commented another co-author, Pasquale Patrizio (Yale University, New Haven, Connecticut, USA), in a press statement.

"We can use cumulus cells surrounding the eggs to gain insight into the health of an egg. These cells are now able to inform us about the chromosomal makeup of an egg. This can help us know if it is the 'right egg' to be fertilized and produce a baby."

Wells added: "By conducting these tests before eggs are fertilized, ethical concerns about analysis of human embryos are avoided."

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