Scientists at Columbia University reported a new way to edit human embryos that they said was more precise than earlier methods and did not produce the chromosomal damage seen in some past experiments.
In a preprint study published June 1, Dieter Egli and colleagues said they used base editing to repair “DNA nicks and mismatches” in human embryos. The paper has not yet been peer-reviewed.
The researchers focused on the PCSK9 gene, which regulates cholesterol, and the HBG genes, which control fetal hemoglobin production. Mutations in PCSK9 can lead to high low-density lipoprotein cholesterol, and some researchers believe changes to HBG genes could help prevent sickle cell disease and thalassemia.
The team inserted base editors into early-stage embryos to alter those genes. In some cases, the edits produced mosaic embryos, meaning some cells were edited and others were not. But the targeted genes were changed without the large DNA deletions or chromosome loss seen in earlier work using CRISPR alone.
“We’re not saying this is going to be used tomorrow in the clinics,” Egli told The New York Times.
Egli and colleagues had reported in 2020 that using CRISPR alone to remove a mutation linked to blindness in human embryos often led to major unintended changes, including long DNA deletions and, in some cases, loss of an entire chromosome. Egli told the Times that the earlier method had “absolutely catastrophic consequences.”
The newer approach used base editing, a technique developed by David Liu of Harvard and the Broad Institute of MIT and Harvard. Nature described it as a way to make “precise, single-letter changes to DNA.”