Human Embryos Genetically Edited Again

For the second time, researchers use CRISPR to modify the genomes of nonviable embryos.

Apr 11, 2016
Kerry Grens

WIKIMEDIA, ERNESTO DEL AGULA III, NHGRIUpon the one year anniversary of the first report of CRISPR being used to alter human embryo genomes, a second group has now done the same. Whereas last time, the gene-editing technique was used to fix a gene that causes β-thalassaemia, this latest attempt focused on altering an immune gene to make cells resistant to HIV infection.

“The good news is that the technique worked for this group in the same way that it did for the first group,” Peter Donovan of the University of California, Irvine, who was not involved in either study, told The Verge. “This indicates the reproducibility of the science. . . . However, this group of researchers also reproduced another finding described by the first group, namely that this type of gene editing also causes off-target effects.”

The researchers, based at Guangzhou Medical University in China, collected fertilized embryos that were not implanted because of an abnormal number of chromosomes. Publishing their results in the Journal of Assisted Reproduction and Genetics April 6, the team found limited success. As stem cell biologist Paul Knoepfler pointed out in his blog The Niche, the group succeeded in editing the gene 5 percent to 15 percent of the time, but created unwanted mutations in the gene—called indels—much more often. “The paper does not in my opinion strengthen the case that CRISPR’ing of human embryos with reproductive intent is ever something that could work well enough to be done clinically,” Knoepfler wrote.

“It just emphasizes that there are still a lot of technical difficulties to doing precision editing in human embryo cells,” Emory University’s Xiao-Jiang Li who was not involved in the work told Nature News.