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They are born healthy with the DNA of 3 people

They are born healthy with the DNA of 3 people

LONDON (AP) — Eight healthy babies have been born in Britain thanks to an experimental technique that uses DNA from three people to help mothers avoid passing rare and devastating diseases to their children.

Most DNA is found in a cell's nucleus, and it's this genetic material—some inherited from the mother, some from the father—that makes people who they are. But there's also some DNA outside the cell nucleus, in structures called mitochondria. Dangerous mutations there can cause various diseases in children, leading to muscle weakness, seizures, developmental delays, organ failure, and death.

In general, tests performed during the in vitro fertilization process can identify whether these mutations are present. But in rare cases, this remains unclear.

Researchers have developed a technique that attempts to avoid the problem by using healthy mitochondria from a donated egg.

In 2023, they reported the first babies born using this method, in which scientists take genetic material from the mother's egg or embryo, which is then transferred to a donated egg or embryo that has healthy mitochondria and whose remaining key DNA is removed. The most recent work "marks an important milestone," said Dr. Zev Williams, who directs the Columbia University Fertility Center and was not involved in the study.

“Expanding the range of reproductive options… will allow more couples to pursue safe and healthy pregnancies.”

Using this method means the embryo has DNA from three people: the mother's egg, the father's sperm, and the donor's mitochondria. Approving it required amending UK law in 2016.

It is also permitted in Australia, but not in many other countries, including the United States.

Experts from Newcastle University in the United Kingdom and Monash University in Australia reported yesterday in the New England Journal of Medicine that they applied the new technique to fertilized embryos from 22 patients, leading to the birth of eight babies who appear to be free of mitochondrial diseases. One woman is still pregnant.

One of the eight babies had slightly higher than expected levels of abnormal mitochondria, said Robin Lovell-Badge, a stem cell and developmental genetics scientist at the Francis Crick Institute, who was not involved in the research. She said it's not yet considered a level high enough to cause disease, but should be monitored as the baby develops.

Dr. Andy Greenfield, a reproductive health expert at Oxford University, called the work “a triumph of scientific innovation” and said the mitochondrial swapping method would only be used in a small number of women for whom other ways of avoiding passing on genetic diseases—such as testing embryos at an early stage—are ineffective.

Lovell-Badge indicated that the amount of donor DNA is negligible, and the resulting child would not have attributes of the woman who donated the healthy mitochondria. The genetic material from the donated egg constitutes less than 1% of the baby born after using this technique.

“If you had a bone marrow transplant from a donor… you would have a lot more DNA from someone else.”

In the United Kingdom, every couple attempting to have a baby born with donated mitochondria must apply for approval from the country's fertility regulator. As of this month, 35 patients have received authorization.

Critics have already raised concerns, warning that it is impossible to know the impact these novel techniques might have on future generations.

“Currently, pronuclear transfer is not permitted for clinical use in the United States, largely due to regulatory restrictions on techniques that result in heritable changes in the embryo,” said Columbia’s Williams. “Whether that will change remains uncertain and will depend on evolving scientific, ethical, and political discussions.”

For nearly a decade, Congress has included provisions in annual funding bills that prohibit the Food and Drug Administration (FDA) from accepting applications for clinical research involving techniques “in which a human embryo is intentionally created or modified to include a heritable genetic modification.”

But in countries where the technique is permitted, activists say it could be a promising alternative for some families. Liz Curtis, whose daughter Lily died of mitochondrial disease in 2006, now works with other families affected by these conditions. She admitted it was devastating to be told there was no treatment for her eight-month-old baby and that her death was inevitable.

He added that the diagnosis “turned our world upside down, and yet no one could tell us much about it, what it was, or how it would affect Lily.” Curtis later set up the Lily Foundation in his daughter's name to raise awareness and support research into the disease, including the most recent work at Newcastle University.

“It’s very exciting for families who don’t have much hope in their lives,” Curtis said.

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