|By Lliane Hunter | 3 years ago|
For the first time, researchers have used CRISPR to speed the inheritance of specific genes in mammals, reports Jon Cohen for Science Magazine. The controversial “gene-drive” was first demonstrated in insects several years ago, promising the ability to quickly spread a gene throughout an entire species. The fresh research shows that gene drives work less efficiently in rodents than in insects, but it has been modestly successful.
The study was conducted by a team at the University of California, San Diego (UCSD), led by geneticist Kimberly Cooper. Plenty of scientific discussion followed submission of the study to bioRxiv. Gaetan Burgio, a mouse geneticist at the John Curtin School of Medical Research in Canberra, Australia tweeted, “nothing is really known about gene drives in rodents. We all assumed the efficiency would be the same as in flies, but it turns out to be very different.” The UCSD team engineered female mice to carry the gene for the DNA-cutting enzyme Cas9. They then engineered males to carry a gene for the other component, the guide RNA (gRNA) that carries Cas9 to a specific target on a genome, along with a gene that modifies coat color.
After Cas9 makes its cut, a cell repairs the damage. A process called homology directed repair (HDR) then inserts a new gene to repair the cut—the team’s gene drive harnesses HDR to insert a new gene. The experiment did not work in males, Cohen reports, but in females, the gene drive succeeded. In one mouse, 79% of her eggs ended up with the color modifying gene on both chromosomes. If she mated with a male without the gene, about 90% of her pups would inherit the gene. Cooper and her colleagues write that this system of “active genetic elements” could speed the creation of mice that have several introduced or crippled genes.