The genome-editing enzyme known as CAS9 at work on a strand of DNA. Nishimasu et al, 2014 A group of Chinese scientists just reported that they modified the genome of human embryos, something that has never been done in the history of the world, according to a report in Nature News.

A recent biotech discovery — one that has been called the biggest biotech discovery of the century — showed how scientists might be able to modify a human genome when that genome was still just in an embryo.

This could change not only the genetic material of a person, but could also change the DNA they pass on, removing "bad" genetic codes (and potentially adding "good" ones) and taking an active hand in evolution.

Concerned scientists published an argument that no one should edit the human genome in this way until we better understood the consequences after a report uncovered rumors that Chinese scientists were already working on using this technology.

But this new paper, published April 18 in the journal Protein and Cell by a Chinese group led by gene-function researcher Junjiu Huang of Sun Yat-sen University, shows that work has already been done, and Nature News spoke to a Chinese source that said at least four different groups are "pursuing gene editing in human embryos."

Specifically, the team tried to modify a gene in a non-viable embryo that would have been responsible for a deadly blood disorder. But they noted in the study that they encountered serious challenges, suggesting there are still significant hurdles before clinical use becomes a reality.

CRISPR, the technology that makes all this possible, can find bad sections of DNA and cut them and even replace them with DNA that doesn't code for deadly diseases, but it can also make unwanted substitutions. Its level of accuracy is still very low.

Huang's group successfully introduced the DNA they wanted in only "a fraction" of the 28 embryos that had been "successfully spliced" (they tried 86 embryos at the start and tested 54 of the 71 that survived the procedure). They also found a "surprising number of ‘off-target’ mutations," according to Nature News.

Huang told Nature News that they stopped then because they knew that if they were do this work medically, that success rate would need to be closer to 100%.

Our understanding of CRISPR needs to significantly develop before we get there, but this is a new technology that's changing rapidly.

Even though the Chinese team worked with non-viable embryos, embryos that cannot result in a live birth, some say that editing the human genome and changing the DNA of an embryo is ethically questionable, because it could lead to more uses of this technology in humans. Changing the DNA of viable embryos could have unpredictable results for future generations, and some researchers want us to understand this better before putting it into practice.

Still, many researchers think this technology (most don't think it's ready to be used yet) could be invaluable. It could eliminate genetic diseases like sickle cell anemia, Huntington's disease, and cystic fibrosis, all devastating illnesses caused by genes that could theoretically be removed.



Others fear that once we can do this accurately, it will inevitably be used to create designer humans with specific desired traits. After all, even though this research is considered questionable now, it is still actively being experimented with.

Huang told Nature News that both Nature and Science journals rejected his paper on embryo editing, "in part because of ethical objections." Neither journal commented to Nature News on that statement.

Huang plans on trying to improve the accuracy of CRISPR in animal models for now.

But CRISPR is reportedly quite easy to use, according to scientists who previously argued against doing this research in embryos now, meaning that it's incredibly likely these experiments will continue.