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Unexpected Loss

A new study finds that using CRISPR to edit human embryonic DNA can lead to unexpected changes, including the loss of whole chromosomes, the Associated Press reports.

Back in 2017, MIT's Technology Review reported that Oregon Health and Science University's Shoukhrat Mitalipov and his colleagues used the gene-editing tool to alter a number of human embryos. After the work was published in Nature, a number of researchers were skeptical of the findings, and the journal added a note to the paper. In particular, critics suspected that, rather than correcting the paternal allele based on the maternal allele as reported — and suggesting a novel repair mechanism — the researchers may have actually deleted the paternal allele.

As Wired writes, this disagreement spurred Columbia University's Dieter Egli to investigate. He and his team now report in Cell that they edited 40 embryos resulting from healthy eggs that had been fertilized using sperm from a man with a frameshift EYS mutation that causes blindness. The researchers then applied CRISPR-Cas9 to try to fix that mutation, though without supplying a repair template to see how the cells would fix it themselves, Wired notes. In about half the cases, the repair process instead led to partial or even whole chromosome loss, the AP adds.

"Our results point to the extraordinary caution necessary before progressing this kind of research to the clinic," Egli tells Wired.