Embryonic gene altered by Chinese researchers

Chinese scientists have reported that they had made history by editing the genome of a human embryo, confirming rumors that have been circulating since March.

MIT Technology Review reported on the rumors that someone had altered the germ line, the genetic information that comes together and forms something new when eggs and sperm collide. The report led to debate about the potential downsides of altering the DNA of human embryos.

On Wednesday, Nature News reported that a research paper on the matter had been published in a low-profile journal called Protein & Cell earlier this week.

The team didn’t implant any of the embryos, admitting in their paper that their success rate was much too low to do so.

The work, led by Junjiu Huang of Sun Yat-sen University in Guangzhou, focused on modifying the gene responsible for thalassaemia, a blood disorder that can be fatal. They used CRISPR/Cas9, a gene-editing tool that has already made waves in editing other species’ genomes. By going after genes at the earliest stage of human development — in a singlecelled embryo — one can theoretically make sure that all the subsequent copies of the gene are the modified version.

But scientists have a lot of work to do before that’s the case. In the study, the researchers attempted to use CRISPR/Cas9 to replace the dysfunctional gene in 86 embryos. Once the embryos had grown to be about eight cells, 54 of the 71 surviving embryos were tested. Of those, 28 had successfully been spliced, and even fewer had the new gene in all of their cells.

In some of the embryos, the editing caused unintended mutations in other genes.

“If you want to do it in normal embryos, you need to be close to 100 percent,” Huang told Nature News.