It is still dangerous to introduce mutations into the human germline
A genetic mutation that Chinese scientist He Jiankui attempted to create in twin babies born last year to help them fend off HIV infection may have done more harm than good. An analysis by University of California, Berkeley, scientists, shows that the mutation is also associated with a 21% increase in mortality in later life.
The researchers scanned more than 400,000 genomes and associated health records contained in a British database, UK Biobank, and found that people who had two mutated copies of the gene had a significantly higher death rate between ages 41 and 78 than those with one or no copies.
Previous studies have associated two mutated copies of the gene, CCR5, with a fourfold increase in the death rate after influenza infection, and the higher overall mortality rate may reflect this greater susceptibility to death from the flu. But the researchers say there could be any number of explanations, since the protein that CCR5 codes for, and which no longer works in those having the mutation in both copies of the gene, is involved in many body functions.
“Beyond the many ethical issues involved with the CRISPR babies, the fact is that, right now, with current knowledge, it is still very dangerous to try to introduce mutations without knowing the full effect of what those mutations do,” said Rasmus Nielsen, a UC Berkeley professor of integrative biology. “In this case, it is probably not a mutation that most people would want to have. You are actually, on average, worse off having it.”
“Because one gene could affect multiple traits, and because, depending on the environment, the effects of a mutation could be quite different, I think there can be many uncertainties and unknown effects in any germline editing,” said postdoctoral fellow Xinzhu Wei.
Wei is first author and Nielsen is senior author of a paper describing the research that appeared online on Monday, June 3, in the journal Nature Medicine.
Wei said that some evidence links the mutation to increased survival after stroke and protection against smallpox and flaviviruses, a group that includes the dengue, Zika and West Nile viruses.
Despite these possible benefits, the potential unintended effects of creating genetic mutations, in both adult somatic cells and in embryonic, germline cells, argue for caution, the researchers said.
“I think there are a lot of things that are unknown at the current stage about genes' functions,” Wei said. “The CRISPR technology is far too dangerous to use right now for germline editing.”
Michael Cook is editor of BioEdge
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