The modification of the human genome may have done more harm than good

^{He jiankui}

A genetic mutation that Chinese scientist He Jiankui tried to create in twins born last year to help protect them from HIV infection may have done more harm than good. An badysis by scientists at the University of California at Berkeley shows that the mutation is also badociated with a 21% increase in mortality later in life.

Researchers badyzed more than 400,000 genomes and badociated health records contained in a UK database, UK Biobank, and found that people with two mutated copies of the gene had a significantly higher mortality rate between 41 and 78. years than those with only one copy or none. .

Previous studies have linked two mutated copies of the gene, CCR5, to a fourfold increase in the mortality rate after influenza infection, and the higher overall mortality rate may reflect this greater susceptibility to death from influenza. But the researchers say that there could be a number of explanations, since the protein for which CCR5 codes, and which no longer works in those with the mutation in both copies of the gene, is implicated in many bodily functions.

"Beyond the many ethical issues related to CRISPR babies, the fact is that now, with current knowledge, it is still very dangerous to try to introduce mutations without knowing the full effect of this. that these mutations do, "said Rasmus Nielsen, professor of integrative biology at the University of Berkeley. "In this case, it's probably not a mutation that most people would like to have, you're actually, on average, less well off."

"Because a gene can affect multiple characters and that, depending on the environment, the effects of a mutation can be very different, I think that there can be many uncertainties and unknown effects in any germ line edition, "said Xinzhu Wei, a postdoctoral fellow.

Wei is the main author and Nielsen is the main author of an article describing the research published online Monday, June 3 in the journal. Nature Medicine.

Wei said some evidence links the mutation to increased survival after stroke and protection against smallpox and flaviviruses, a group that includes dengue, Zika and West Nile viruses.

Despite these potential benefits, the potential unexpected effects of creating genetic mutations, both in adult somatic cells and in embryonic germ cells, argue for caution, the researchers said.

"I think there are a lot of things unknown at the current stage about gene functions," Wei said. "CRISPR technology is far too dangerous to use for germ line editing."

Michael Cook is a publisher of BioEdge

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