A modified version of CRISPR has been used to reverse genetic obesity in two different mouse models without editing any genes, scientists from the University of California San Francisco have announced. The technique, CRISPRa, uses the guidance system in CRISPR to target certain genetic sequences and amplifies existing gene activity to ramp up protein production.

The mice used in the study lacked a copy of a gene involved in hunger and satiety, with resulting protein levels unable to be maintained by the other gene copy. The CRISPRa therapy raised the remaining gene copy’s activity, allowing it to create enough protein to stop the animals from overeating for months after the first treatment.

The authors said that more than 660 genes are subject to this flaw, and can create a number of problems including obesity and cancer if one of the copies produces insufficient levels of a protein. The CRISPRa therapy, they theorised, could be used in future to cure this. It could also be used to prevent diseases caused by micro-deletions too big for CRISPR to repair.

Co-author of the study Dr Christian Vaisse theorised that CRISPRa could have advantages over current CRISPR editing processes: “For therapeutic purposes, CRISPRa may be preferable to conventional CRISPR.

“It solves many of the problems associated with making permanent modifications to the genome, and it has the potential to treat a variety of genetic diseases for which gene editing isn’t an option.”