Biopsy of egg DNA to aid IVF
Dr Lux Fatimathas
Progress Educational Trust16 October 2011
US researchers have developed a way to analyse the viability of human eggs at a genetic level without causing them harm. This technology will help improve the chances of successful IVF for couples with fertility problems.
'There's a lot of work that needs to be done, but it's a small step in hopefully being able to improve IVF medicine in the long term', said Mr Adrian Reich, lead author of the study at Brown University, Providence Rhode Island.
'Currently, the most widely-used metrics for evaluating an egg for IVF are based on how the egg looks', continued Reich. Based on this assessment, the eggs deemed to look best and therefore have the most potential for successful fertilisation, are chosen. Maximising on the quality of eggs used in IVF improves the chances of a viable pregnancy. This has led to the current investigation into a more accurate and quantifiable method to judge egg quality.
In this study researchers determined the health of the eggs by analysing their polar bodies. During the production of eggs asymmetric cell divisions occur, which result in the production of an egg and one or two accompanying polar bodies. Polar bodies contain an extra copy of chromosomes that the egg has discarded, as well as a small amount of the egg's mRNA (messenger RNA) – a blueprint of the egg's DNA. By taking a biopsy of the polar body, the researchers were able to obtain an indication of the genetic quality of the egg, without perturbing the egg itself.
'This was the first step in determining whether or not it might be possible to determine the quality of individual oocytes [eggs] in a cohort of oocytes', said Reich. Researchers were for the first time able to isolate mRNA from polar bodies and determine its sequence, using single-cell sequencing. This was also carried out in the eggs themselves for comparison, and revealed that the mRNA from the polar body was a good representation of the genetic quality of the egg itself.
'It seems that the polar body does reflect what is in the egg. Because the egg is the major driver of the first three days of human embryo development, what we find in the polar body may give us a clue into what is happening during that time', said Professor Sandra Carson, director of the Centre for Reproduction and Infertility at Women and Infants Hospital, Providence Rhode Island, who co-authored the study.
Future work will involve further validation of the technique and determining which genes are particularly important in governing egg quality.
'If this technology is validated, we will be able to tell if this egg is a good egg or an egg incapable of making a human being. It's a very exciting piece of information for people doing IVF, but it's preliminary', said Dr Edmond Confino, an infertility expert at Northwestern Memorial Hospital, who was not involved in the study.
This study was published in the Journal of Biological Chemistry.
Reproduced with permission from BioNews, an email and online sources of news, information and comment on assisted reproduction and genetics.