Chinese scientist – He Jiankui’s extraordinary claim regarding making the first babies — twin girls — with edited genomes astonished the world. Among researchers’ principal concerns are the potential effects of the genetic alterations on the health of girls.

He, a genome-editing researcher at the Southern University of Science and Technology of China in Shenzhen told that he impregnated a woman with embryos that had been edited to disable a gene that allows HIV to infect cells. Then this gene, known as CCR5, was targeted because it is well studied, and because its mutation offers protection against HIV infection. The CCR5 gene has been the topic of research since long back and has roles beyond HIV that scientists are just beginning to understand. The loss of CCR5 function increases the risk of severe or fatal reactions to some infectious diseases, for example, and has also been shown to enhance learning in mice.

Target gene

The CCR5 protein is expressed on the surface of some immune cells, and HIV takes advantage of it. The scientists identified a mutation, known as CCR5-Δ32, that makes carriers highly resistant to HIV. Although the CCR5-Δ32 mutation disables the gene and makes carriers resistant to the dominant strain of HIV, CCR5 also helps to protect the lungs, liver and brain during some other serious infections and chronic diseases.

Virus protection

The CCR5 protein also interacts with proteins called β-chemokines that help the body mount an immune response against a group of viruses called flaviviruses. These include tick-borne viruses and the viruses that cause dengue and yellow fever, as well as West Nile virus. The people with the CCR5-Δ32 are more likely to experience severe encephalitis from tick-borne diseases, and to have a severe reaction to the vaccine for yellow fever.  Influenza could also pose a greater risk to the twins. Also among people with multiple sclerosis, those with the CCR5-Δ32 deletion are twice as likely to die early than are people without the mutation.

Brain enhancement?

Although whether the twins will learn faster than they would have done without the mutation, other scientists are sceptical about the gene deletion will have a noticeable effect on the girls’ learning

Silva Alcino, a neuroscientist at the University of California Los Angeles, agrees that any effect will likely be unpredictable. The deletion of this receptor confers some advantages and very likely also results in deficits in some forms of cognitive function in neuroscience.

Despite the growing body on the mutation research, it is difficult to draw conclusions about its overall effects. Only a small number of people has the mutation, making it difficult to recruit large numbers of participants for studies. However, the potential consequences of lacking a working CCR5 gene are probably greater than have been established so far.