CRISPR Cas9 is a revolutionary tool for editing the human genome. Used for therapy, it promises cures for serious genetic diseases. But the same technology can modify reproductive cells and embryos—a moral horizon so uncertain that it demands our attention now.
What therapeutic possibilities does this technology offer?
This is genuinely revolutionary at the level of the human genome. CRISPR-Cas9 is simple to use and inexpensive. It revives gene therapy, which raised enormous hopes years ago but failed to deliver. CRISPR-Cas9 works on every genome: human, plant, animal.
Researchers have already used it experimentally on cystic fibrosis and Duchenne muscular dystrophy. For cystic fibrosis, scientists took intestinal cells from two patients, converted them into induced pluripotent stem cells, and grew them together into what's called an "organoid"—a structure that mimics how an organ works. In this case, the intestine. They used CRISPR-Cas9 to eliminate the mutation causing cystic fibrosis and achieved complete repair of those cells.
It's extraordinary. But so far this works at the cellular level, not yet in an entire organ. It's an important first step that may one day allow us to repair all the diseased cells in an organ and move to human trials. Much more research is needed.
Similar work is underway with Duchenne cells. Other applications are being pursued in certain cancers with viral causes and in HIV-infected cells. The clinical possibilities are vast.
What ethical questions does this raise?
Somatic therapies—treating body cells—pose no ethical problem. The real issue is germline therapy: modifying reproductive cells or embryos. With CRISPR-Cas9, you can easily alter human DNA in every cell, including sperm and egg cells. These changes would be passed to all future generations.
Recent attempts in China failed, and major scientific journals refused to publish the results for ethical reasons. The question was raised at an international summit in Washington in December 2015: Should we be allowed to work freely on embryos and reproductive cells? We should ask ourselves this. The trouble is we have no idea where it leads. If you correct one gene, what gets passed to the next generation? You take on responsibility toward a child who might end up with far graver diseases. Not to mention: you might kill the embryo in the process.
The next step would be repairing genes in an egg or sperm cell. We know nothing about what happens at fertilization. This technology puts us on the path to controlling humanity's future. Americans and the French say no for now. The British and Chinese do not. This is a global ethical crisis. By what right do we govern tomorrow's humanity?
Can we set limits?
We need a true worldwide moratorium: a complete halt to all germline genetic therapies. But not everyone accepts this.
Alliance Vita warns of a possible "human ecological catastrophe." What do you think?
Humans are and will remain fragile. We shouldn't imagine that one day we'll cure humanity with a "perfect" genome, as transhumanism suggests.
A perfect genome means nothing because it cannot exist. To speak of a perfect genome, you'd need a reference genome. For the human genome, there is none and never will be. It would mean rejecting human diversity. A genome with selected, "improved" genes would lead to total individualism: humans who think they'll never be sick, who believe they no longer need each other. With this technology comes the old illusion that humans are only genetics. But that's completely false. We know context and environment shape our genes. Even scientists studying genetic disease need real contact with sick people and their families—because fragility and vulnerability demand solidarity.
Interview by Cyril Douillet (O&L no. 213)
Translated by Rita Massi
CRISPR-Cas9: What's Behind the Name?
CRISPR is English for Clustered Regularly Interspaced Short Palindromic Repeats. Cas9 is the enzyme that works with it. Briefly: it's a mechanism borrowed from certain bacteria, where it serves as an immune defense. These bacterial sequences can recognize foreign DNA from viruses. The Cas9 enzyme—like scissors—cuts and removes this foreign DNA precisely, without damaging the bacterium's own DNA. The bacterial cell then rebuilds itself using its natural repair mechanisms. Bacteria developed this trick; now we can use it to edit human DNA. Cas9 can be guided to human sequences and remove them. For now, we're not yet at 100 percent success with human genome editing.