Eight healthy babies who were born in Britain with the DNA of three people in a “scientific tour-de-force” are doing well and reaching their milestones, reports The Telegraph.
Particularly thrilling for the scientists involved in the technique is that none of the children shows any sign of mitochondrial DNA disease.
Dubbed “three parent babies”, the infants carry the genetic material of a “second mother” to repair damage in their mitochondrial DNA, which powers the cells.
Scientists in the county have spent decades perfecting the technique, which involves transplanting nuclear DNA – containing all of the characteristics of a person – into a donor egg with healthy mitochondria.
They hope the breakthrough can help women whose children would be at risk of mitochondrial disease.
Full updates of the studies were recently published in The New England Journal of Medicine.
Disorder
Every year around one in 5 000 children are born with mitochondrial mutations in Britain, while 12 000 have a mitochondrial disorder.
These can lead to serious problems like heart and liver failure, blindness, deafness, diabetes, respiratory problems and even death.
After following the infants for up to two years, scientists announced last week that the technique works and the babies are all healthy.
Professor Sir Doug Turnbull, Emeritus Professor of Neurology, at Newcastle University, who led the team said: “I think everybody knows I’m a natural pessimist, so it’s a relief.
“Mitochondrial disease can have a devastating impact on families. The news offers fresh hope to many more women at risk of passing on this condition and who now have the chance to have children growing up without this terrible disease.”
The disease is passed down solely from the mother, and there is no cure, but in the late 1990s, scientists began to question whether the defective mitochondria could be replaced with healthy donor DNA.
While nuclear DNA is the blueprint for the entire cell, comprising around 3.3bn base pairs, mitochondrial DNA only codes for energy production and is built from around 16 000 base pairs.
Nevertheless, the idea proved controversial, with both the Church of England and the Catholic Church in England and Wales questioning whether the technique was safe or ethical.
Experts from the Zoological Society of London warned that in 50% of animal studies, faulty mitochondrial DNA had been transferred over during the procedure, while the US Food and Drug Administration deemed the process unsafe.
In spite of the objections, Parliament approved new legislation to allow the procedure in 2015, and the first licence was granted in 2017 to Newcastle Fertility Centre, which pioneered the technique.
The procedure involves transplanting the nuclear DNA, which contains all of the genes making up individual characteristics, from a fertilised egg to an egg donated by an unaffected woman which has had its nuclear DNA removed.
The resulting embryo inherits its parents’ nuclear DNA, but the mitochondrial DNA is inherited predominantly from the donated egg.
Early attempts failed and it was not until 2023 that Freedom of Information requests showed the first baby had been born in Newcastle by these methods.
At the time, researchers were reluctant to discuss the case, leading to fears the child had not survived.
Nature journal reports that the latest studies are the first detailed reports of the Newcastle team’s efforts.
In 2023, The Guardian revealed that up to five UK children had been born using mitochondrial donation. But there were few details about the children’s health and other questions surrounding the technique’s effectiveness.
In total, 22 women carrying disease-causing mitochondria went through thr mitochondrial donation procedure (pronuclear transfer), leading to eight births (including a pair of twins) and one ongoing pregnancy, report reproductive biologist Mary Herbert, now at Monash University in Melbourne, Australia, and her team.
The children, four girls and four boys, were all born healthy and are developing normally. The oldest child is now more than two years old, the youngest under five months. Five children have had no health problems at all, one experienced muscle jerks that went away on their own, another child was successfully treated for high level of fat in their blood and a heart-rhythm disturbance, a third had fever due to a urinary tract infection.
The scientists said none of the eight babies shows no signs of having mitochondrial DNA disease.
Professor Bobby McFarlane, Professor of Paediatric Mitochondrial Medicine at Newcastle University said: “We are cautiously optimist about the results. The children are all well and continuing to meet their developmental milestones.
“While longer term follow-up of children born after mitochondrial donation is of paramount importance, these early results are very encouraging.”
Life and possibility
Scientists hope the breakthrough can help around 150 women a year.
Unlike with egg or sperm donors, children are not entitled to know the details of their mitochondrial donor unless they have agreed to share the information. However, in some cases friends or family have donated their DNA.
Dusko Ilic, Professor of Stem Cell Science, King’s College London, told The Telegraph the healthy births were “a remarkable accomplishment”.
Dr Andy Greenfield, Honorary Fellow at the Nuffield Department of Women’s & Reproductive Health at the University of Oxford, added: “It is a triumph of scientific innovation in the IVF clinic – a world-first that shows that the UK is an excellent environment in which to push boundaries in IVF.”
A baby was born in 2016 in Mexico using a similar technique developed by British researchers, but it is not known if the child survived.
NEJM article – Mitochondrial Donation in a Reproductive Care Pathway for mtDNA Disease (Open access)
The Telegraph article – First ‘three-parent’ babies found healthy in scientific breakthrough
See more from MedicalBrief archives:
UK first as baby born from three people’s DNA
UK gives three-parent fertility treatments the green light