Crispr-Cas9 Genetic Scissors Cause Frequent and Unexpected Mutations

Uncertainties are reinforced around the Crispr-Cas9 experimental technique. A study
published on Monday in the journal Nature shows that it has unintended consequences: these "genetic scissors" have caused significant and frequent mutations in experiments on mice and human cells.

This work has shown that unintended changes in DNA by this technique "have been largely underestimated until now," Allan Bradley, of the Wellcome Sanger Institute in England, said in a statement. conducted. "To consider using this technique in gene therapy must be accompanied by many precautions, monitoring the possible negative effects," he continued.

Correcting a typo

Crispr-Cas9 is a major discovery unveiled in 2012. Emmanuelle Charpentier and Jennifer Doudna, a French and an American, are at the origin of this discovery, frequently cited for the award of the Nobel Prize.

It is based on an enzyme that acts as molecular scissors. They can remove unwanted parts of the genome very precisely to replace them with new pieces of DNA, much like when you correct a typo in a word processor. This technique is only at the research stage and is not used on humans.

In previous work, researchers have succeeded in correcting a genetic defect in human embryos. This potentially opens the way to great advances in the treatment of genetic diseases, but also raises serious ethical questions.

Influence the expression of defective genes

Because theoretically, this technique could be used to produce genetically engineered babies modified to choose for example the color of their hair or to increase their physical strength. The work revealed on Monday revealed changes in the DNA of certain cells that could activate or deactivate important genes, with potentially heavy consequences.

"This study highlights that in terms of genome editing, it is essential to check that the changes that occur are those and only those that we wanted to cause. This has always been obvious, "said a researcher who did not participate in the study, Robin Lovell-Badge, Francis Crick Institute of London.

However," these results do not justify panic or lose faith in these techniques, "he continued. All researchers insist that it is necessary to continue research on Crispr-Cas9 before any clinical application

>> To read also: Genetic manipulation. Josiah Zayner, the biohacker who goes too far?

>> See also: Crispr-Cas9. A hope to cure genetic diseases but ethical concerns

>> To read also: Gene therapies. "Medicine will never overcome death," says Arnold Munnich