In a remarkable advancement in reproductive technology, researchers have successfully utilized an experimental technique involving DNA from three individuals to help mothers in Britain avoid transmitting rare, devastating diseases to their offspring. This significant achievement was reported on Wednesday, with eight healthy babies born using this innovative method.
Most of our genetic material resides in the nucleus of our cells, inherited from both parents. However, there is also a smaller portion of DNA outside the nucleus, located in structures known as mitochondria. Mutations in mitochondrial DNA can lead to severe health complications in children, including muscle weakness, seizures, developmental delays, major organ failure, and even death. While in vitro fertilization (IVF) typically includes testing for these mutations, some cases remain ambiguous.
To combat the risks posed by mitochondrial mutations, researchers have been developing a breakthrough technique that utilizes healthy mitochondria from a donor egg. This process, reported in 2023, involves transferring genetic material from the mother's egg or embryo into a donor egg or embryo that contains healthy mitochondria, with the donor's other genetic information removed. This pioneering method allows for the creation of embryos with DNA from three individuals: the mother, the father, and the mitochondrial donor.
Dr. Zev Williams, director of the Columbia University Fertility Center, stated that this research marks “an important milestone” in reproductive options. He emphasized that the expansion of these options empowers couples to pursue safe and healthy pregnancies. The use of this technique was made lawful in the UK following a 2016 law change and is also permitted in Australia, although it remains restricted in many other nations, including the U.S.
Researchers from Newcastle University in the UK and Monash University in Australia published their findings in the New England Journal of Medicine, revealing that they performed this innovative technique on fertilized embryos from 22 patients, resulting in eight babies born without detectable mitochondrial diseases. Additionally, one woman involved in the study is currently pregnant. One of the eight newborns displayed slightly elevated levels of abnormal mitochondria, yet experts believe this is not significant enough to cause health issues, warranting monitoring as the child grows.
Andy Greenfield, a reproductive health expert at the University of Oxford, described the study as “highly significant.” He noted that mitochondrial exchange techniques would primarily benefit a small subset of women who do not have effective alternatives for preventing genetic disease transmission, such as early-stage embryo testing. He remarked, “The technique was first made lawful 10 years ago, so we have all been waiting for this report. Fortunately, the children appear to be healthy.”
Follow-up studies on these children will be crucial to ensure their ongoing health. Robin Lovell-Badge, a scientist at the Francis Crick Institute, clarified that the donor's mitochondrial DNA is insignificant, comprising less than 1% of the total genetic material. “If you had a bone marrow transplant from a donor, you would have much more DNA from another person,” he explained.
In the UK, couples wishing to conceive using donated mitochondria must obtain approval from the fertility regulator. Critics have raised concerns about the long-term effects of such novel techniques on future generations. Dr. Williams noted that pronuclear transfer is currently prohibited in the U.S. due to regulatory restrictions on heritable genetic modifications. He mentioned, “Whether that will change remains uncertain and will depend on evolving scientific, ethical, and policy discussions.”
For families affected by mitochondrial diseases, like Liz Curtis, whose daughter Lily tragically passed away from such a condition in 2006, this development provides a glimmer of hope. Curtis, who now collaborates with other affected families, expressed the devastating impact of being told that there was no treatment for her infant daughter. She founded the Lily Foundation in her daughter's memory to raise awareness and advocate for research, including the recent advancements at Newcastle University. “It’s super exciting for families that don’t have much hope in their lives,” she emphasized.
The Human Fertilisation and Embryology Authority, the UK’s fertility regulator, welcomed these findings, stating that this technique will only be available to couples at very high risk of transmitting mitochondrial diseases. As of now, 35 patients have been authorized to undergo this pioneering procedure, paving the way for potential breakthroughs in the fight against hereditary diseases.
