London – Eight healthy babies were born in Great Britain with the help of an experimental technique which uses the DNA of three people to help mothers avoid spending rare diseases devastating to their children, researchers reported on Wednesday.
Most of DNA is in the nucleus of our cells, and it is this genetic material – some inherited from mom, some of dad – who makes us who are. But there is also DNA outside the nucleus of the cell, in structures called mitochondria. Dangerous mutations can cause a range of diseases in children who can cause muscle weakness, convulsions, development delays, major organ failure and death.
Tests during the in vitro fertilization process can generally identify if the mutations are present. But in rare cases, it’s not clear.
The researchers have developed a technique that tries to avoid the problem using the healthy mitochondria of a donor egg. They reported in 2023 that the first babies were born using this method, in which scientists take genetic material from the mother’s egg or embryo, which is then transferred to a donor or an embryo which has healthy mitochondria but the rest of its key DNA.
The latest research “marks an important step,” said Dr. Zev Williams, who heads the Columbia University Fertility Center and was not involved in the work. “The widening of the range of reproduction options … will allow more couples to pursue safe and healthy pregnancies.”
The use of the method means that the embryo has DNA of three people – the mother’s egg, the father’s sperm and the donor’s mitochondria – and it took a change of British law of 2016 to approve it. It is also authorized in Australia but not in many other countries, including the United States.
Experts from the British University of Newcastle and Monash University in Australia reported on Wednesday in the New England Journal of Medicine, which they had carried out the new fertilized embryo technique of 22 patients, which made eight babies who seem to be free from mitochondrial diseases. A woman is always pregnant.
One of the eight babies had slightly higher than expected levels of abnormal mitochondria, said Robin Lovell-Badge, a scientist in the stem cell genetics and development of the Francis Crick Institute who was not involved in research. He said he was still not considered a high enough level to cause a disease but that he should be monitored as the baby develops.
Andy Greenfield, a genesic health expert at the University of Oxford who was not involved in the study, called him “very significant”, adding that the Mitochondria exchange method would only be used for a small number of women for which other ways to avoid transmitting genetic diseases, such as testing embryos at an early stage, were not effective.
“The technique was made legal 10 years ago, so we are waiting for this report,” he told NBC News by e-mail. “Fortunately, children seem to be healthy.”
Child monitoring – potentially for many years – would be important to make sure they remain healthy, he said.
Lovell-Badge said that the donor’s quantity of DNA is insignificant, saying that any resulting child would have no lines of the woman who donated healthy mitochondria. The genetic material of the given egg represents less than 1% of a born baby using the technique.
“If you had a bone marrow transplant from a donor … You will have much more DNA from another person,” he said.
In the United Kingdom, each couple looking for a baby born by given mitochondria must be approved by the country’s fertility regulator.
Critics have previously raised concerns, warning that it is impossible to know the impact that new techniques may have on future generations.
“Currently, pronuclear transfer is not authorized for clinical use in the United States, largely due to regulatory restrictions on techniques that cause hereditary changes to the embryo,” said Williams, Columbia, in an email. “The question of whether it will change remains uncertain and will depend on the evolution of scientific, ethical and political discussions.”
For about a decade, the Congress included provisions in annual financing invoices prohibiting the Food and Drug Administration from accepting clinical research requests involving techniques “in which a human embryo is intentionally created or modified to include hereditary genetic modification”.
But in countries where the technique is authorized, the defenders say that it could provide a promising alternative to certain families.
Liz Curtis, whose daughter Lily died of a mitochondrial disease in 2006, is now working with other families affected by them. She said it was devastating to say that there was no treatment for her 8 month old baby and that death was inevitable.
She said that the diagnosis “overturned our world, and yet no one could tell us a lot, what it was or how it was going to affect Lily”. Curtis then founded the Lily Foundation on behalf of her daughter to raise awareness and support research on the disease, including the latest work at Newcastle University.
“It’s super exciting for families who don’t have much hope in their lives,” she said.
The authority of fertilization and human embryology, the Fertility regulator of the United Kingdom, praised the results, adding that the technique would be legally available only for people at very high risk of transmitting the disease on their children.
Since this month, 35 patients have been authorized to undergo the procedure.
