IVF embryo culture link to genetic disorder
Dr Jess Buxton
Progress Educational Trust24 June 2006
New research on mouse embryos suggests that laboratory culture conditions can affect the activity of several genes. The findings, presented by US scientists at the annual conference of the European Society of Human Reproduction and Embryology (ESHRE) in Prague, Czech Republic, add to evidence that IVF methods might increase the risk of some rare genetic 'imprinting' disorders. However the team, based at the University of California, caution that their results are preliminary, and that further research is needed.
Genetic imprinting is the process by which certain mammalian genes are switched off during early embryo development, according to whether they were inherited from the father or mother. Previous research has suggested that the incidence of a condition called Beckwith Wiedemann syndrome (BWS) - which involves the imprinted gene IGF2 and others, including H19 - may be increased amongst children conceived using IVF techniques. The symptoms of BWS include an enlarged tongue, liver, spleen, kidneys and pancreas and an increased risk of certain tumours.
Researchers think that the increased incidence of BWS could either be down to part of the IVF procedure itself, or could be due to a genetic link between BWS and certain causes of infertility. In the latest study, the scientists wanted to try and address this question, by studying the effects of different culture conditions on mouse embryos. They looked at 38 different imprinted mouse genes, and found that the activity of most of them was no different in IVF embryos, compared to those conceived in vivo. However, five showed a difference, depending on the culture conditions.
The five mouse genes whose activity appeared to be affected by the embryo culturing process were Cd81, Slc38a4, Copg2, Gnas and H19 - one of the imprinted genes involved in some cases of BWS. The activity of H19 was consistently lower in the IVF embryos, regardless of the culture conditions used. Team leader Gnanaratnam Giritharan stressed that although the findings are important for better directing future studies in humans, they first need repeating in different strains of mice. The scientists hope that their studies will eventually lead to better culture media for IVF procedures.
Reproduced with permission from BioNews, an email and online sources of news, information and comment on assisted reproduction and genetics.