The affair of the gene-edited babies rumbles on

ON NOVEMBER 26THDNACRISPRCCRHIVHIVAIDSHIV He Jiankui, a -sequencing expert at the Southern University of Science and Technology, in Shenzhen, claimed he had orchestrated the birth of the world’s first gene-edited babies: twin girls who arrived in early October. That claim brought the fury of the world raining down upon his head and he has since disappeared from view—though he has not, apparently, been arrested as some news reports have suggested.Exactly what Dr He achieved has also been called into question. He says he used a gene-editing technique called -Cas9 to disable, in one of the twins, called Nana, both parental copies of a gene called 5. This gene encodes a protein used by to enter cells. If Dr He’s claim is true, he may have conferred on Nana immunity to infection by , thus protecting her from , which causes. Moreover, by editing the genes of a fertilised egg—from which all body tissues, including the ovaries, are derived—he has done this in a way that can be passed down the generations, a process known as germ-line editing.