In April of 2015, Chinese researchers announced to the world that they had used the new genome-editing technology CRISPR/Cas9 on human preimplantation embryos to modify the HBB gene, mutations of which have been implicated in the disease β-thalassemia. The news had sparked a media firestorm and eventually led scientists from across the globe to discuss intently the ethics of such studies, ultimately leading to the decision for an international moratorium on the use of CRISPR with human embryos.
Now, a group of scientists from the Guangzhou Medical University has used the CRISPR/Cas9 system to modify once again human embryos. However, the researchers stated that they used the technique on unviable embryos with extra chromosomes. Moreover, the researchers obtained 213 fertilized eggs from a fertility clinic that were classified as “unsuitable” for in vitro therapy due to the extra set of chromosomes. The Guangzhou team used every egg on the condition at they would not be permitted to develop into human beings.
The investigators sought to edit the immune cell gene CCR5, adding a mutation that damaged this gene—which has been linked to a natural HIV resistance. The scientist hoped to learn more about the possibility of producing fetuses that would be immune to HIV.
The researchers reported that only 4 out of 26 of the embryos were edited successfully—many were still carrying genes that had not been modified whereas others had resulted in off-target gene mutations. The researchers emphasized that all of the embryos were destroyed after 3 days.
The findings from this study were published recently in the Journal of Assisted Reproduction and Genetics in an article entitled “Introducing Precise Genetic Modifications into Human 3PN Embryos by CRISPR/Cas-Mediated Genome Editing.”
“This paper doesn’t look like it offers much more than anecdotal evidence that it works in human embryos,” George Daley M.D., Ph.D., director of the stem cell transplantation program at Boston Children's Hospital and Dana-Farber Cancer Institute, stated to Nature News. “It’s certainly a long way from realizing the intended potential.”
Yet, even amidst controversy perhaps there is perhaps some useful information that can be gleaned for the research community.
“The good news is that the technique worked for this group in the same way that it did for the first group,” Peter Donovan, Ph.D., professor at 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 Chinese scientists seem undeterred by the condemnation of their work from their peers—suggesting that the research they are conducting is groundbreaking and paving the way for future studies and innovations while stressing that no genetically modified embryos will be allowed to mature. Only time will tell if their research will lead to any usable results or be universally condemned from an ethical standpoint.