By Richard Alleyne
Hereditary diseases could be eradicated before birth by ‘genetically modifying’ eggs
Many hereditary diseases including cancers and diabetes could eventually be eradicated before birth after scientists found a way to “fix” the DNA of unfertilised eggs.
In a new technique which will reopen the ethical debate over embryo research, researchers have for the first time found a way to safely remove and replace genetically abnormal parts of an egg. The procedure will remove the risk of diseases being passed from mother to child.
The breakthrough could immediately eradicate rare diseases of the eye, muscle and mind and could eventually lead to cures for more common disorders with a hereditary element such as cancer, diabetes and infertility.
But the technique – which has already been successfully carried out in monkeys – would need a controversial change in the law to be used on humans, as many people think it would be akin to playing God.
Under the Human Fertilisation and Embryology Act, this kind of treatment – or any that involves genetically modifying an egg – remains illegal but the government has put in place a framework to relax the rules if and when science shows it can have positive impact on health.
The technique, perfected at the Oregon National Primate Research Center and Oregon Health & Science University, centres on diseases caused by inherited defects in the “power packs” of cells, known as mitochondria.
Most DNA in an egg is contained in its nucleus but there is a tiny amount in the mitochondria, which is only passed on from the mother.
If it is defective then the defect is passed on. A number of rare “mitochondria diseases” are already known and affect roughly one person in every 4,000 or 5,000.
But it is thought these defects also play a role in much more common diseases. In all, one in 200 people could be affected by abnormalities to the mitochondria, it is thought.
The new technique involves using a microscopic syringe to remove the nucleus of an egg from an affected women and transplant it into a healthy donor egg – one that does contain defects to its mitochondria.
The egg is then fertilised in a test tube and transplanted back into the original donor.
The resultant baby remains the woman’s biological child but without her inherited defects to the mitochondria.
The US scientists, who reported their breakthrough in the journal Nature, have successfully carried out the technique in macaque monkeys with no signs of complications.
They believe it is so successful that they could begin human trials if the law allowed it.
Shoukhrat Mitalipov, co-author, said: “Assuming that regulation, funding and other logistics are cleared up, clinical trials could begin immediately.”
He said that rare conditions were already known to be caused by the defects but many others may also be effected.
“Mitochondrial DNA mutations are also increasingly implicated in a range of socially recognisable conditions, including Alzheimer’s, Parkinson’s and Huntington’s diseases, obesity, diabetes and cancer,” he said.
“It is still unclear whether these mutations were inherited or acquired during lifetime.”
The findings were welcomed as “exciting” and with great potential by the scientific world.
Professor Peter Braude, head of the Department of Women’s Health, King’s College London, said it was “remarkable”.
Douglas Wallace of the University of California, an authority on mitochondria, said the results were exciting and the technique is “potentially very interesting.”
Dr Duane Alexander, director of the Eunice Kennedy Shriver National Institute of Child Health and Human Development, which provided funding for the study, said: “Pending further research, the findings hold the potential of allowing a couple to have a child who is biologically their own, but is free of any conditions associated with defects in maternal mitochondria.”
A spokesman for the HFEA said: “If it looks like a likely candidate for an effective treatment then they could change the regulations.”
Professor Ian Wilmut, head of the Medical Research Council’s Centre for Regenerative Medicine at the University of Edinburgh, said: “It is a really exciting achievement.
“This brings us an important step nearer to being able to prevent the birth of children with a particular type of inherited disease.”
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