Many of you will have already heard of CRISPR-Cas9, the so-called molecular scissors that serve to modify the DNA of many organisms. This technique has represented a revolution in the field of genetic engineering in recent years due to its ability to "cut and sew" a specific DNA sequence to make corrections in target genes. So much so that it has opened new avenues and new possibilities for gene therapy, that is, the possibility of treating or preventing diseases by intervening directly on the patient's genome.

But how advanced are these techniques today? And what are the risks?

The use of CRISPR which has created the most stir, but also disappointment, in the scientific community it happened in the case of the Chinese twins, girls born with modified DNA in the laboratory. So much so that it has opened new avenues and new possibilities for gene therapy, not for a real medical need, such as the presence of pathologies in treated embryos, but only to provide resistance to HIV and prevent any transmission from HIV-positive parents.

This news, already described in a previous article (, has raised many concerns because the practice of editing is currently only allowed in the laboratory, as changes in sex cells and embryos are still associated with unwanted mutations and genetic problems that may arise later in life.

If on the one hand there are those who take these bets, on the other hand, there are those who wonder if CRISPR is really safe on embryos. To answer this question, researchers from the University of Uppsala, in Sweden, they tried to modify the DNA of 1000 zebrafish larvae, , for their zebra-like striped body, and to analyze the effects on both adults and offspring.

By studying their genome, the researchers found unexpected mutations of different types in adults and children. In particular, they found the addition or deletion of base pairs not only on the sites chosen as the target but also outside, or structural changes in DNA fragments larger than the target ones. All this resulted in the disruption of the function and regulation of genes that had not been chosen as targets, a consequence that could cause serious damage at a later time depending on the affected gene.

“It is important to know that these unexpected mutations are inheritable, as they can have long-term consequences for future generations. But this can only happen if you change the genome of the embryos or germ cells, ”said Ida Holder, Ph.D from the University of Uppsala.

This does not mean that CRISPR-Cas9 cannot be used in the healthcare sector, but before clinical application, the risks must be identified and analyzed to minimize unwanted effects. To do this, security protocols are required that include the use of the latest DNA sequencing technologies to carefully validate the modified cells.