United Kingdom. "A breakthrough in medicine": eight babies born with the DNA of three people

Hope for hundreds of families. Eight healthy babies have been born in the United Kingdom following genetic manipulation using the DNA of three people to prevent them from being affected by mitochondrial diseases. British law was specially amended in 2015 to allow this experiment, the results of which were eagerly awaited by the medical community.

The mitochondria is a small structure present in our cells, responsible for converting nutrients into energy. But in one in 5,000 babies, this mitochondria malfunctions. This failure is the cause of mitochondrial diseases, which often have very serious consequences: vision problems, diabetes, deafness, muscle degeneration, etc. The outcome is often fatal. In France, approximately 200 babies are born each year with a mitochondrial disease, according to the Pasteur Institute. However, these mitochondria operate on a special DNA, distinct from the rest of the cell. The idea behind mitochondrial donation is therefore, immediately after the conception of an embryo, to replace the mother's mitochondrial DNA with that of another woman. All the remaining genetic material (99.9%) remains that of both parents.

Of the approximately twenty patients, eight gave birth to children—four boys and four girls, now aged between six months and three years. This already shows that mitochondrial donation allows for a viable pregnancy. But, importantly, these children were born with a very low level of compromised mitochondrial DNA. This illustrates that the treatment "works to reduce the transmission" of mitochondrial diseases, concludes the study, published Wednesday in the New England Journal of Medicine .

Several precautions are in order. First, two children experienced medical complications. The authors believe this is not related to the procedure, but some commentators feel they are ruling it out a bit too quickly. Above all, since birth, three of the children have already seen an increase in their defective mitochondria, which raises the question of the sustainability of the effects. Nevertheless, these are "very important results and a breakthrough in mitochondrial medicine," according to Swedish professor Nils-Göran Larsson, one of the world's leading experts in the field, in a response to the British Science Media Center.

However, scientific progress isn't the only thing receiving positive comments. This is also the case for the regulation chosen by the United Kingdom, praised by many researchers for allowing this research while closely supervising it from an ethical perspective.

This choice contrasts with many other countries. In the United States, health authorities have regularly expressed their opposition in recent years. In France, the Public Biomedicine Agency has sought to launch research, but has repeatedly run into legal challenges, even though bioethics laws only allow experiments on embryos less than two weeks old, produced through assisted reproduction and destined for destruction.

Mitochondrial donation does, in fact, raise ethical questions. Some observers fear that the procedure, which introduces a small dose of DNA from a third party, could disrupt the child's development as a person. Critics, however, point out that it is a form of genetic manipulation of the embryo, strictly prohibited by certain international conventions.

Furthermore, outside of the British experience, children have been born in recent years from mitochondrial donations under less restrictive regulatory frameworks, in Greece or Ukraine - with sometimes more vague justifications, such as treating infertility. "It's the problem of the benefit/risk ratio: for a mitochondrial disease, the benefit is obvious," says French researcher Julie Steffann, a mitochondrial disease specialist. "In the context of infertility, it hasn't been proven." But the ban on research in France "is regrettable for patients," she adds, deeming it inappropriate to equate mitochondrial donation with the creation of a "transgenic" embryo.