According to a report on 6 April in the Journal of Assisted Reproduction and Genetics, Dr. Fan Yong at Guangzhou Medical University attempted to modify the CCR5 gene, which codes for a cell receptor that the HIV virus uses to enter T cells. Their paper — which used CRISPR-editing tools in non-viable embryos that were destroyed after three days — is currently only the second published claim of gene editing in human embryos.

 Dr. Fan’s team used CRISPR–Cas9 genome editing to alter some of the embryos to mutate causing a crippling effect on an immune-cell gene called CCR5. Some humans naturally carry this mutation (known as CCR5Δ32), and they are resistant to HIV. This is because the mutation changes the CCR5 protein in a way that prevents the virus from entering the T cells to try to infect. Genetic analysis showed that 4 of 26 human embryos targeted were successfully modified. However, not all the embryos’ chromosomes harbored the CCR5Δ32 mutation — some contained unmodified CCR5, whereas others had acquired different mutations.

 Dr. Fan's work serves two purposes: First, to evaluate the technological advances and to establish principles for introducing precise genetic modifications in early human embryos; Second, to raise the awareness of potential legal and ethical challenges that society will face due to increased accessibility of genome engineering technologies.

 Dr. Fan's work was reported by Nature, Science and MIT Technology Review. George Daley, a stem-cell biologist at Children’s Hospital Boston in Massachusetts, points out that Dr. Fan's main advancement is the use of CRISPR which introduces precise genetic modifications successfully.