Monya Baker, Ewen Callaway, Davide Castelvecchi, Lauren Morello, Sara Reardon, Quirin Schiermeier and Alexandra Witze in Nature:
Rarely has a method roared onto the scene as quickly as the accurate, easy-to-use yet controversial CRISPR–Cas9 genome-editing system. In April, scientists in China reported use of the technique to edit non-viable human embryos, which spurred researchers and bioethicists to debate in editorials and meetings whether the technology should ever be used in human embryos, even for basic research. The debate culminated in the International Summit on Human Gene Editing in early December in Washington DC, which brought together nearly 500 ethicists, scientists and legal experts from more than 20 countries. The organizers wrapped up the event with a statement: the tools are not yet ready to be used to edit the genomes of human embryos intended for pregnancy. But they did not call for an outright ban of this work for basic research.
Over the past three years, CRISPR has become the tool of choice for scientists seeking to enhance animals and crops, and to cure human disease (see ‘CRISPR craze’). In October, researchers set a record by editing the genomes of pig embryos in 62 places at once — a move that could help to revitalize the field of xenotransplantation. The genetic tinkering could lower the risk of exposure to potentially dangerous pig viruses when people receive human-like organs grown in swine. Dogs, goats and sheep have also had their DNA modified with the low-cost technology.
CRISPR could target human diseases as well. With that aim in mind, in August, Google and other investors pumped US$120 million into the genome-editing start-up Editas Medicine in Cambridge, Massachusetts. The firm plans to use CRISPR in clinical trials in 2017 to correct a genetic mutation in some people who are visually impaired.
Other, more mature genome-editing technologies are already entering the clinic. In November, researchers in the United Kingdom announced that they had used a different system — enzymes called TALENs — to edit human immune cells and transplant them into a one-year-old with leukaemia, possibly saving her life.