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The genetically edited babies would have been born in China. What can go wrong?

A scientist in China may have used a powerful gene-editing tool to extract unwanted genes from human embryos, creating the first genetically modified humans and bringing a dystopian future feared by many, one step closer.

The scientist, He Jiankui, said in a video that he published online Yesterday (November 25) I had used CRISPR-Cas9, a gene editing tool that has revolutionized the field of genetics in the last decade, to eliminate a gene in human embryos in order to make babies resistant to HIV . He said in the video that those embryos have become two healthy babies: a group of twins named Lulu and Nana. The twins "came to the world crying as healthy as any other baby a few weeks ago," he said in the video.

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The scientist's claim has not been verified (in fact, the hospital named in the ethical approval documents of He has denied any participation in the procedure, CNN reported), but the scientific community has still responded to the claim with indignation and concern, According to press reports. In fact, even leaving aside the very real ethical concerns of using this technology to manipulate human genes, many scientists believe that such alterations could have far-reaching and unforeseen health problems.

It is true that the modification he made to the embryos "will prevent HIV infection," said Mazhar Adli, a geneticist at the University of Virginia School of Medicine. However, the problem is that the deleted gene, called CCR5, "has many more functions that only help HIV infection," Adli told Live Science, including helping white blood cells to function properly.

The gene may also play a role in helping to prevent infection by West Nile virus, so removing it from the genome probably makes a person more susceptible to the disease, said Feng Zhang of the Broad Institute in a statement issued. in response to the news. . Zhang was one of the scientists who promoted the use of CRISPR gene editing technology.

In addition, genes do not exist in isolation, they are constantly interacting with other genes, which can have important effects on the body. "Removing a single gene can not only alter the way other genes will work, but it can also alter the overall behavior of the cell and the phenotype of [the] Organism, "said Adli. (A phenotype is an observable characteristic, such as brown eyes, that someone has based on the genotype, or the genes, which code it).

And these concerns are caused by problems that can arise when it is badumed that the CRISPR technology will work perfectly and accurately. Unfortunately, that is unlikely to be the case: in July, scientists published a report in the journal Nature Biotechnology that discovered that the use of CRISPR-Cas9 technology may be causing more damage than previously thought, by unwittingly changing large pieces of DNA.

"One has to use this technique very prudently, because it is badociated with many problems," said Dr. Avner Hershlag, chief of Northwell Health Fertility in Manhbadet, New York. Therefore, reaching and eliminating that gene could have unwanted effects, "off target" in other parts of the genome. In other words, the Cas9 protein that you program to remove a site could travel to another site in the genome and make changes you do not want, Hershlag told Live Science. But it is very unlikely that the scientist will realize that these changes occurred outside the target; they may not become apparent until the baby is born, or even later in life, he said.

There are "important genetic conditions that only express themselves later in life," Hershlag said. And those genetic changes can be pbaded on to future generations, he said.

There is also the risk of something called mosaicism, said Hershlag. Normally, cells in the body have the same identical set of genes, but mosaicism refers to a scenario in which some, but not all, cells have a genetic change due to gene editing, Hershlag said. This is something that, in itself, can lead to illness, he added.

Both Adli and Hershlag also pointed to the fact that when it comes to preventing HIV, there are safer (and easier) ways to do it. For example, the PrEP treatment method, which is taken as a daily pill, has been shown to be successful in preventing infections in the main trials. And other treatments may be on the horizon.

Then, Adli added, "who will take responsibility for those future babies when their partners are treated with a simple pill and survive happily, but the edited gene is experiencing all that remains to be identified" [side] effects? "

Originally published in Living science.

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