The key facts
- Cambridge edited the NANOG gene; Columbia University edited three genes linked to cholesterol and hemoglobin
- Expert at the Francis Crick Institute: the methods are safer, but mosaicism is 'low but not zero'
- No country permits editing of cells that can be passed on to offspring
Two studies bring the topic back onto the agenda
In the summer of 2026, two studies on editing the genome of human embryos were published, reigniting public debate. One was led by Kathy Niakan at the University of Cambridge (UK), the other by Dieter Egli at Columbia University (USA). Both teams used base editing — a technique from 2016 that allows genetic material to be altered more precisely than previous methods — and both worked with human embryos rather than mice.
What exactly was studied
The Cambridge team used base editing to target the NANOG gene, which, as it turned out, is necessary for the future organism to form from the embryo. 'Base editing is a significant step forward compared with conventional CRISPR-Cas9, because the risk of unintended chromosomal errors is much lower,' Niakan said in a press release. Egli's group applied the method to three genes: one linked to high cholesterol and cardiovascular disease, and two linked to hemoglobin production. 'By introducing such damage with editors, we are beginning to understand how embryos cope with genome damage. In the long term, we hope to learn how to prevent genetic and developmental disorders in IVF, in order to make infertility treatment more effective, safer and more accessible,' Egli noted.
Scientific limitations
Embryo editing is not yet a medical reality: modifying the genes of an embryo is scientifically extremely difficult, and no country permits altering cells that could be passed on to offspring. Robin Lovell-Badge, head of the Laboratory of Stem Cell Biology and Developmental Genetics at the Francis Crick Institute in London, assessed both studies as a move in the right direction, but with room for improvement. 'The methods look much safer. But there is still a lot of work to be done. It seems the levels of mosaicism are low but not zero, so there is still much work to be done here,' he told Euronews Next. Mosaicism is one of the main obstacles: it arises when base editor molecules fail to find and alter some cells, which could potentially lead to the development of diseases.
Ethical questions
Pascal Borry, professor of bioethics at KU Leuven (Belgium), pointed to a key dilemma: 'Very often the question arises of the tension between therapy and enhancement. Where do we draw the line? What is therapeutic? What is enhancement?' He also noted the problems of consent and the risk of stigmatizing communities of people living with certain conditions, and emphasized that the technology may be superfluous: alternatives exist, in particular preimplantation genetic testing — analysis of embryos during IVF to detect abnormalities. Björn Heindryckx, a professor at Ghent University coordinating research in the infertility department, agrees that editing is not necessary to prevent genetic conditions, but sees value in the method for science: a better understanding of embryo development will yield more knowledge about some forms of infertility.
The position for regulation, not a ban
Lovell-Badge is less concerned about the ethical side: 'I have no problem with it if it is safe and there is a good ethical reason. I think it is unethical to allow people to have children with a genetic disorder if it could be avoided.' In his view, countries should regulate the practice but not impose a complete ban. As an example, he cited a hypothetical mission to Mars: prolonged exposure to an environment with high levels of radiation could create a desire to modify the body to protect against it.
