The technique involves the transfer of DNA between two fertilised eggs to help prevent the transmission of mitochondrial diseases.
Speaking on BBC Radio 4’s Today programme Professor Alison Murdoch, professor of reproductive medicine at Newcastle University said: “Doctors would really like to be able to cure diseases as they arise but the ideal role is that we prevent them…unfortunately there is no cure once this problem has arisen in a child.
“For the first time there is potentially the option that we can actually prevent this being passed on not only to a child or children but to their children as well.”
Every cell in our body needs energy to function. This energy is provided by mitochondria, often referred to as the cells’ ‘batteries’. Mitochondria are found in every cell, along with the cell nucleus, which contains the genes that determine our individual characteristics. The information required to create these ‘batteries’ – the mitochondrial DNA – is passed down the maternal line, from mother to child.
A mother’s egg contains a copy of her own DNA – twenty-three chromosomes – as well as DNA for her mitochondria. The amount of genetic material contained in mitochondrial DNA is very small – 13 protein-producing genes, compared to an estimated 23,000 genes that we inherit from our parents – and this information is used solely to generate the energy produced by the ‘batteries’.
Like all DNA, the DNA in mitochondria can mutate and mothers can pass these mutations onto their children. Around one in 200 children are born each year with mutations which in most cases cause only mild or asymptomatic forms of mitochondrial disease. However, around one in 6,500 children are born with severe mitochondrial diseases, which include muscular weakness, blindness, fatal heart failure, liver failure, learning disability and diabetes and can lead to death in early infancy.
There are no treatments available to cure these conditions and mothers face the agonising choice of whether to risk having a child who may be affected by such a disease or not to have children at all.
In research published in Nature last year, researchers at Newcastle University demonstrated a technique which allows them to replace these ‘batteries’. This was the first time such a technique had been used with fertilised human eggs.
A fertilised egg usually contains two pronuclei – genetic material from the egg and sperm – as well as mitochondria. The technique developed by the Newcastle team involves extracting the pronuclei but leaving behind the mitochondria. The researchers then take a fertilised egg from a donor, remove its pronuclei and replace them with the extracted pronuclei. This new fertilised egg contains the DNA of the father and mother, and the mitochondria from the donor.
Currently the technique is not permitted under the The Human Fertility and Embryology (HFE) Act as amended in 2009, however, the Act includes the provision for the Secretary of State to permit this in the future which has led to the review by the Human Fertilisation and Embryology authority (HFEA).
“Changing the battery”
Professor Doug Turnbull who led the research which was funded by the Muscular Dystrophy Campaign, the Medical Research Council and the Wellcome Trust said: “What we’ve done is like changing the battery on a laptop. The energy supply now works properly, but none of the information on the hard drive has been changed. A child born using this method would have correctly functioning mitochondria, but in every other respect would get all their genetic information from their father and mother.”
Welcoming the Health Secretary, Andrew Lansley’s announcement of the review, Professor Murdoch added: “We are not ready to do this in patients now but the science is progressing very rapidly and we need to get Parliament to discuss this again now. We anticipate that the process of review could take about a year so we are asking for this process to start now. Of course there is no guarantee that we will have all the evidence we need to secure a license in a year but we need to anticipate that we may have and prepare accordingly.”
Details can be seen here of the HFEA review of scientific methods to avoid mitochondria disease. The HFEA panel is set to submit its report to the government next month.
‘We lost our child – and our future’
Beth Wilkes’ son Casper died from mitochondrial disease in July last year, aged three months old. She told BBC Radio 4’s Today programme: “He was born on time. It was a normal pregnancy, a straightforward labour.
“Casper passed his initial tests, and it was six weeks before we realised there was something wrong.
“He was floppy and he wasn’t as responsive. He stopped crying. He just wasn’t the baby we brought home from hospital.
“He endured five weeks of vigorous, invasive tests while the hospital tried to identify what was wrong.”
The family eventually found out Casper had a condition called Leigh’s disease. They are now being treated by experts in Newcastle as they seek to have another baby unaffected by mitochondrial disease.
The Wilkes are not receiving the technique being examined by the HFEA, but another called pre-implantation genetic diagnosis. Mrs Wilkes says the new technique could have helped Casper.
“His eyes, face, hair would have been 100% the same. The ultimate difference it would have made is that he would have survived.
“But we not only lost our child, we lost our future.”