Production of MSTN mutated cattle using CRISPR--Cas9

Many transgenic animals have been produced using CRISPR–Cas9 technology to edit specific genes. However, there are few guidelines for the application of this technique in cattle. The goal of this study was to produce trait-improved cattle using the genome editing technology CRISPR–Cas9. Myostatin (MSTN) was selected as a target locus and synthetic mRNA of sgRNA and Cas9 was microinjected into bovine in vitro fertilized embryos. As a result, 17 healthy calves were born and 3 of these showed MSTN mutation rates of 10.5%, 45.4%, and 99.9%, respectively. Importantly, the offspring with the 99.9% MSTN mutation rate had biallelic mutation (-12bp) and a doubling muscle growth phenotype. In conclusion, we showed that the genome editing technology CRISPR–Cas9 can produce genetically modified calves with improved traits.