A team of scientists, led by biologist Kathy Niakan of the Francis Crick Institute, used the genetically engineered CRISPR gene editing technique to create genetically modified human embryos in a laboratory in London. After deleting a gene from the human embryo in the study, they found that half of the edited embryos contained major unintentional changes.
Fyodor Urnov, an expert in gene editing and professor of molecular and cellular biology at the University of California, Berkeley, says this experiment is a warning to all genome editors to refrain from editing embryos.
Such genetic damage could lead to birth defects or medical problems such as cancer in children who would use embryo modification.
CRISPR (clustered regularly interspaced short palindromic repeats) is a family of DNA sequences found in the genomes of prokaryotic organisms such as bacteria and archaea. These sequences are derived from bacteriophage DNA fragments that previously infected the prokaryote. They are used to detect and destroy the DNA of similar bacteriophages during subsequent infections. Therefore, these sequences play a key role in the antiviral (ie anti-phage) defense system of prokaryotes. CRISPR, as a gene editing tool, allows the treatment of all kinds of diseases.
Niakan’s team used CRISPR to remove a gene known as POU5F1 in 18 of 25 embryos under study, with the other embryos being used as controls. 10 of the edited embryos looked normal, but eight had abnormalities on a particular chromosome, of which four had unintentional changes in DNA directly adjacent to the edited gene.
“What that means is that you’re not just changing the gene you want to change, but you’re affecting so much of the DNA around the gene you’re trying to edit that you could be inadvertently affecting other genes and causing problems,” says Kiran. Musunuru, a cardiologist at the University of Pennsylvania.
Previously, there have been other failures to use CRISPR to modify the DNA of human embryos in a laboratory.