Eight babies have been born in the UK using genetic material from three people to prevent devastating and often fatal conditions, doctors say. The method, pioneered by UK scientists, combines the egg and sperm from a mum and dad with a second egg from a donor woman. This technique has been legal in the UK for a decade and has now been proven to lead to children born free of incurable mitochondrial disease.
These conditions are normally passed from mother to child, starving the body of energy, and can cause severe disability and death in babies. Couples know they are at risk if previous children, family members, or the mother has been affected. Children born through the three-person technique inherit most of their DNA from their parents but also get a tiny amount, about 0.1%, from the second woman. This is a change that is passed down the generations.
None of the families who have been through the process are speaking publicly to protect their privacy, but have issued anonymous statements through the Newcastle Fertility Centre where the procedures took place. One mother said, “After years of uncertainty this treatment gave us hope – and then it gave us our baby. We look at them now, full of life and possibility, and we’re overwhelmed with gratitude.”
The mother of a baby boy added, “Thanks to this incredible advancement and the support we received, our little family is complete. The emotional burden of mitochondrial disease has been lifted, and in its place is hope, joy, and deep gratitude.” Mitochondria are tiny structures inside nearly every one of our cells and are the reason we breathe as they use oxygen to convert food into energy.
Defective mitochondria can leave the body with insufficient energy to keep the heart beating, causing brain damage, seizures, blindness, muscle weakness, and organ failure. About one in 5,000 babies are born with mitochondrial disease. The team in Newcastle anticipate there is demand for 20 to 30 babies born through the three-person method each year. Some parents have faced the agony of having multiple children die from these diseases.
Mitochondria are passed down only from mother to child, so this pioneering fertility technique uses both parents and a woman who donates her healthy mitochondria. The eggs from both the mother and the donor are fertilized in the lab with the dad’s sperm. The embryos develop until the DNA from the sperm and egg form a pair of structures called the pro-nuclei.
These contain the blueprints for building the human body, such as hair color and height. The pro-nuclei are removed from both embryos, and the parents’ DNA is put inside the embryo packed with healthy mitochondria. The resulting child is genetically related to their parents but should be free from mitochondrial disease.
A pair of reports in the New England Journal of Medicine showed 22 families have gone through the process at the Newcastle Fertility Centre, leading to four boys and four girls, including one pair of twins, and one ongoing pregnancy. “To see the relief and joy in the faces of the parents of these babies after such a long wait and fear of consequences, it’s brilliant to be able to see these babies alive, thriving, and developing normally,” said Prof Bobby McFarland.
All of the babies were born free of mitochondrial disease and met their expected developmental milestones. There was a case of epilepsy, which cleared up by itself, and one child has an abnormal heart rhythm which is being successfully treated. These are not thought to be connected to defective mitochondria.
The results show that in five cases the diseased mitochondria were undetectable. In the other three, between 5% and 20% of mitochondria were defective in blood and urine samples. This is below the 80% level thought to cause disease. It will take further work to understand why this occurred and if it can be prevented.
Prof Mary Herbert said, “The findings give grounds for optimism. However, research to better understand the limitations of mitochondrial donation technologies will be essential to further improve treatment outcomes.” The breakthrough gives hope to families affected by mitochondrial disease, such as the Kitto family.
Kat’s youngest daughter Poppy, 14, has the disease, and her eldest Lily, 16, may pass it onto her children. Poppy is in a wheelchair, is non-verbal, and is fed through a tube. Despite decades of work, there is still no cure for mitochondrial disease, but the chance to prevent it being passed on gives hope to Lily.
“It’s the future generations like myself, or my children, or my cousins, who can have that outlook of a normal life,” she says. The UK not only developed the science of three-person babies but also became the first country in the world to introduce laws to allow their creation after a vote in Parliament in 2015.
There was controversy as mitochondria have DNA of their own, which controls how they function. It means the children have inherited DNA from their parents and around 0.1% from the donor woman. Any girls born through this technique would pass this onto their own children, so it is a permanent alteration of human genetic inheritance.
This was a step too far for some when the technology was debated, raising fears it would open the doors to genetically-modified “designer” babies. Prof Sir Doug Turnbull said, “I think this is the only place in the world this could have happened, there’s been first-class science to get us to where we are, there been legislation to allow it to move into clinical treatment, the NHS to help support it, and now we’ve got eight children that seem to be free of mitochondrial disease, what a wonderful result.”
Liz Curtis, the founder of the Lily Foundation charity, said, “After years of waiting, we now know that eight babies have been born using this technique, all showing no signs of mito. For many affected families, it’s the first real hope of breaking the cycle of this inherited condition.”
Source link
