Researchers in China have reported creating tuberculosis-resistant cattle using CRISPR/Cas9 genome editing.

Led by senior author Yong Zhang of Northwest Agricultural & Forestry University, the team used a single Cas9 nickase - a single-strand cutting Cas9 variant - to induce genome editing using the homology-directed repair pathway, inserting a gene for natural resistance-associated macrophage protein-1 (NRAMP1) into bovine fetal fibroblasts. As the researchers reported in Genome Biology, they used somatic nuclear transfer to get the edit into an egg cell, creating 11 cows in vitro with NRAMP1 (nine using Cas9 nickase) and demonstrating that the gene provided increased resistance to tuberculosis.

Moreover, they said that while the Cas9 nickase did not completely eliminate off-target edits, it did reduce them, especially when compared to standard Cas9 which creates double-strand breaks and is much more likely to create indel mutations via the non-homologous end-joining DNA repair pathway.

While the team said that this was the first instance of gene insertion into cattle using a single nicking Cas9, it was far from the first application of genome editing to livestock, or even cows. In May 2016, researchers led by Minnesota-based gene editing firm Recombinetics reported substituting an allele in dairy cattle to eliminate horns, using transcription activator-like effector nucleases (TALENs) to induce HDR. And last fall, another team of scientists from Northwest A&F University reported editing cashmere goats using CRISPR to produce more of the fine hairs used in wool production.