19 April 2010
ByAppeared in BioNews 554
A team of researchers at Newcastle University in the UK has been successful in attempts to transfer genetic material from one newly fertilised human egg to another without carrying over the egg's mitochondria (the energy-producing structures of a cell). The technique could be used to prevent the transmission of abnormal mitochondria from a woman to her children, which has been linked to many known conditions including fatal liver failure, blindness, muscular dystrophy, type-II diabetes and deafness.
The research was published last week in the scientific journal Nature and was jointly funded by the Muscular Dystrophy Campaign, the Medical Research Council and the Wellcome Trust. Professor Douglass Turnbull, who headed the study, said that the new technique could provide a solution for women at high risk of bearing children severely affected by mitochondrial disease. He added that further work is required to ensure that the method is safe and that embryos manipulated in this way can be brought to term.
The study used 80 newly fertilised eggs left over from fertility treatments and donated for research. The nuclei from the father's sperm and mother's egg were removed, leaving behind most of the egg's mitochondria. Both nuclei were inserted into another fertilised egg that had already had its own nucleus removed. These newly formed embryos were then grown for 6-8 days to demonstrate that development could continue normally. Encouragingly, subsequent tests also showed that only minimal amounts of the mother's mitochondrial DNA was carried over.
Professor Turnbull told the Daily Telegraph newspaper that a child born using this method would get all their genetic information from their father and mother but would also receive correctly functioning mitochondria. He likened the new technique to changing the battery on a laptop whilst leaving the information on the hard drive unchanged. 'This is a very exciting development with immense potential to help families at risk from mitochondrial diseases,' he added.
The researchers are optimistic that the technique could be made available to women within the next three years. Currently around one in every 6,500 children is born with a serious mitochondrial disorder, causing chronic health problems and even death. The BBC reported that Sharon Bernadi from Sunderland, inherited a mitochondrial disease from her mother, which she also transmitted to her children. Six died shortly after birth and her only surviving son, Edward, has a severely debilitating mitochondrial disease and requires constant care. Although the new technique comes too late for Sharon it could help other similarly affected women give birth to healthy children.
The Human Fertilisation and Embryology Act 2008 made it illegal to use embryos that have been manipulated in the laboratory to create babies, so a further change in the law is required before this technique can be trialled in humans. Charities and others are now putting pressure on the Government to side-step this law by using secondary legislation brought by the Health Secretary. Sir Mark Walport, director of the Wellcome Trust, said that 'this is exciting research that could lead to the major clinical advance of preventing devastating mitochondrial diseases by curing the disease in fertilised eggs.'
Some agree that the procedure, once proved safe, should be allowed. Art Caplan, director of the Center for Bioethics at the University of Pennsylvania in the US, said: 'For these diseases that are very debilitating or devastating it makes sense.' Others warn that the creation of embryos with two mothers would be meddling with nature, although the research team stressed that the DNA from the donor mother comprised less than 0.2 per cent of total DNA in the new embryo. Josephine Quintavalle, from campaign group Comment on Reproductive Ethics, said that this was the worst kind of embryo experiment, adding: 'It is completely distorting the natural process. We have no clue what the long-term consequences will be.'