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Studies have found that Crispr gene editing may cause unwanted changes in human embryos



In 2017, a team of researchers led by geneticist Shoukhrat Mitalipov of Oregon Health and Science University in Portland reported that human embryos carrying mutations can be coaxed into the process without a synthetic template. The researchers created an embryo through a combination of two cells: a sperm with a mutation that makes it more difficult for the heart to draw blood, and an egg with a healthy version of the gene. Dr. Mitalipov and his team used Crispr-Cas9 to cut the broken copy of the gene to see if the full version can guide its repair. They reported that the experiment was a success and published it in the journal Nature.

Dr. Elie said: “In principle, this may be a way to correct mutations in human embryos.”

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But the new findings may cast doubt on the 2017 study.

Researchers in cell research focused on a different mutation-a mutation that causes hereditary blindness and affects different parts of the genome-but used a similar setting. They used the donated sperm containing a mutation in a gene called EYS, they fertilized an egg with a normal copy of EYS, and then sent it to Crispr-Cas9 to snip the mutation.

Dr. Egli said that some of the cells managed to sew DNA fragments cut by Chris Puss and made some small changes.

But about half of the embryos seem to be unable to cope with the trauma of fracture. The genetic damage failed to heal and eventually forced the cells to shed and discarded the bulk of the chromosomes carrying the mutant EYS. In some cells, the entire chromosome is lost.

“This is not a correction,” Dr. Egri said. “That is a completely different result.”

Maria Jashin, a geneticist at Memorial Sloan Kettering Cancer Center and another researcher, said that the Crispr mechanism does not gently induce cells to edit the targeted gene “text”, but rather excavates the inability of the cell’s DNA. Repair the gap. She added that the negative consequences of this are disastrous. Dr. Jashin said: “They are talking about trying to repair a gene, and a large part of your genome is changing.”

Dr. Egli and Dr. Jasin said that this may have occurred in Dr. Mitalipov’s 2017 paper, but it did not attract attention. After Dr. Mitalipov’s team processed Crispr-Cas9, they could no longer detect the mutation in the embryo. But Dr. Egli and Dr. Jasin pointed out that, technically speaking, dumping or destroying a large part of the chromosome will also eliminate evidence of mutation. They said that Dr. Mitalipov and his team may mistake the deletion for an editor.


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