On 6 April a Chinese team has reported editing non-viable embryos in the attempt to make them HIV-resistant. It is the second case of human gene editing that has been published. Apart from ethical concerns, is this study truly important and how is the issue currently dealt with in other parts of the world?

It happened for the firs time less than a year ago when a Chinese team published the first attempt to perform gene editing on non-viable human embryos (which I talked about here). It quickly became a major ethical issue among the international scientific community, especially in western countries.

This time as well, the study comes from a Chinese university, the Guangzhou Medical University and was published in the Journal of Assisted Reproduction and Genetics on 6 April. The team led by the stem­ cell scientist Yong Fan collected 213 fertilised human eggs donated by 87 patients. As it was for the last year study, they used non-viable eggs. It means that they can’t be implanted after fertilisation, as part of an IVF (in vitro fertilisation) procedure, because they contain an extra set of chromosomes that makes them incompatible with life.

Tom Ellenberger, Washington University School of Medicine in St. Louis, and Dave Gohara, Saint Louis University School of Medicine via NIH

What this Chinese team attempted is to make these human embryonic stem cells resistant to HIV infection. Using CRISPR-Cas9, the super star of gene editing techniques, they inserted a mutation known as CCR5Δ32, which turns the T cells targeted by the HIV virus invisible to its attack. This mutation is naturally carried by a very particular set of HIV patients called elite controllers. However, only 4 of 26 human embryos targeted were successfully modified. Further analysis showed that only some embryos’ chromosomes gained the CCR5Δ32 mutation, whereas others contained unmodified CCR5 or had acquired different mutations.

Thus, just as Huang’s study did last year, this new attempt confirms that CRISPR-Cas9 is still not enough efficient for a safe use on humans. “We believe that any attempt to generate genetically modified humans through the modification of early embryos needs to be strictly prohibited until we can resolve both ethical and scientific issues”, wrote the authors in the paper.

It is interesting to notice that there was a considerably lesser media coverage on this study compared to the first case just one year ago. Basically, it was Nature News who published the most detailed article. “This paper doesn’t look like it offers much more than anecdotal evidence that it works in human embryos, which we already knew”, said George Daley, biologist at Children’s Hospital Boston in Massachusetts.

Does it mean that we are no longer frightened by these Chinese studies? Again Nature News reported that there are other similar studies going on in China that will presumably be published sooner or later. Will they have an even lower impact on the western news media?

DNA Double Helix
National Human Genome Research Institute, National Institutes of Health.  www.genome.gov

It is true to say that these studies are not scientifically ground breaking, and surely this second study didn’t add anything relevant on an ethical point of view. Tetsuya Ishii, a bioethicist at Hokkaido University in Sapporo, Japan, said that there are no issues on how the experiments were conducted, but he questions their necessity.

In February, the UK fertility regulators approved a research using CRISPR to genetically editing human embryos. The biologist Kathy Niakan at the Francis Crick Institute in London, will use it to inactivate genes involved in very early stages embryo development, in hopes of understanding why some pregnancies terminate. Viable embryos will be used, but the experiment must be stopped within 14 days.

“I think this will be a good example to countries who are considering their approach to regulating this technology. We can have a well­ regulated system that is able to make that distinction between research and reproduction”, said Sarah Chan, a bioethicist at the University of Edinburgh, UK.

Meanwhile, at the Broad Institute of MIT, Feng Zhang created a rationally engineered Cas9 nucleases with improved specificity in order to make the applications of CRISPR-Cas9 (among which the studies on human embryos) more plausible and effective.

The field is moving on incredibly fast, and it’s probably time to look at how the use of these techniques on human embryos can be allowed conscientiously instead of worrying too much about these Chinese studies.

Header image: Embryonic stem cells. Wikimedia commons