While using CRISPR gene editing technology to repair a gene in human embryos that causes hereditary blindness, scientists at Columbia University found it made additional unintended changes, eliminating an entire chromosome or large sections of it.
The study, published in Cell, used sperm from a single human donor with hereditary blindness caused by a mutation on the EYS gene to create 40 embryos. The investigators used CRISPR on 37 of the embryos, with the remaining three serving as controls. About half of the modified embryos lost large segments of chromosome 6, on which the mutation is located.
“This study is not going to stop the field. But we have to ask what to do with these powerful tools, and in which context they are safe and efficacious,” said study author Dieter Egli, PhD, who is Assistant Professor of Developmental Cell Biology at Columbia University.
As the U.S. government does not permit using federal funding to conduct research on human embryos, the study was funded by private donations from the New York Stem Cell Foundation and The Russell Berrie Foundation. Scientists know more about the cell and molecular biology of mouse embryos than human embryos, Dr. Egli said, and “[these results indicate that] the human embryo seems unique in its poor ability to fix a DNA break.”
An international commission sponsored by the U.S. National Academy of Medicine, U.S. National Academy of Sciences, and the U.K.’s Royal Society stated in September that because scientists don’t yet understand how to use gene editing technology without unintended and potentially dangerous consequences, it is not ready to be used to modify DNA in human embryos.
Jennifer Doudna, PhD, who was recently awarded the Nobel Prize in Chemistry for the discovery of CRISPR alongside Emmanuelle Charpentier, PhD, told The Wall Street Journal that “the commission’s recommendations reflect consensus in the field that the technology shouldn’t be used for embryo editing in the clinic at this time.”