Scientists have created an embryo with genetic material from a man and two women, using a technique they say could someday help prevent mothers with rare inherited diseases from passing them on to their children.
The aim of the lab dish experiments is to prevent damaged DNA in mitochondria — the batteries that power cells — from being inherited.
Mitochondrial DNA is separate from the egg's nucleus where most of a mother's DNA is found.
Around one in 6,500 children are born with serious diseases caused by malfunctioning mitochondrial DNA, which can lead to fatal heart problems, liver failure, brain disorders, blindness and muscular weakness, lead researcher Doug Turnbull, a neurologist at Newcastle University in England said in this week's issue of the journal Nature.
The experiment effectively replaced the mitochondria.
"What we've done is like changing the battery on a laptop," Turnbull said in a podcast news conference.
"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."
Cloning technique adapted
The researchers used a variation of the technique used to create Dolly the cloned sheep in 1996.
The nuclei from the father's sperm and the mother's egg, which contain the parents' DNA, were removed, leaving behind the faulty mitochondria.
Nuclear DNA is found in the nucleus of our cells. The information includes material from both parents and gives us our unique hereditary traits. Only identical twins share the same nuclear DNA. Mitochondrial DNA is found outside of the nucleus, where a cell generates energy. The vast majority of mitochondrial DNA is inherited from the mother.
The nuclei were then put into another egg that had its nucleus removed but kept its mitochondria. The resulting fused embryo contained genes from both parents as well as a small amount of mitochondrial DNA from the donor egg.
A total of 80 embryos were created and developed in the laboratory for six to eight days to reach the blastocyst stage — a ball of about 100 cells, the team reported in the study. The embryos were then destroyed as required under current British rules.
'Ray of hope'
"These findings will be a ray of hope for people affected by mitochondrial diseases who can often be left with the heart-breaking decision of whether to have children who may be born with a serious illness," said Philip Butcher, chief executive of the Muscular Dystrophy Campaign, one of the funders of the research.
"In the future this technique may give parents the choice to have a healthy child and end the tragic cycle that some families go through, passing on these conditions from generation to generation," he added on the group's website.
Turnball said he hoped the technique could be used on human volunteers within three years, but stressed more work needs to be done to determine the safety and effectiveness of the technique. He also acknowledged ethical concerns surrounding the work.
The Medical Research Council and the Wellcome Trust also funded the research.