Targeted mutations in myostatin by zinc-finger nucleases result in double-muscled phenotype in Meishan pigs

<jats:title>Abstract</jats:title><jats:p>Myostatin (MSTN) is a dominant inhibitor of skeletal muscle development and growth. Mutations in <jats:italic>MSTN</jats:italic> gene can lead to muscle hypertrophy or double-muscled (DM) phenotype in cattle, sheep, dog and human. However, there has not been reported significant muscle phenotypes in pigs in association with <jats:italic>MSTN</jats:italic> mutations. Pigs are an important source of meat production, as well as serve as a preferred animal model for the studies of human disease. To study the impacts of <jats:italic>MSTN</jats:italic> mutations on skeletal muscle growth in pigs, we generated <jats:italic>MSTN</jats:italic>-mutant Meishan pigs with no marker gene via zinc finger nucleases (ZFN) technology. The <jats:italic>MSTN-</jats:italic>mutant pigs developed and grew normally, had increased muscle mass with decreased fat accumulation compared with wild type pigs and homozygote <jats:italic>MSTN</jats:italic> mutant (<jats:italic>MSTN</jats:italic><jats:sup>−/−</jats:sup>) pigs had apparent DM phenotype and individual muscle mass increased by 100% over their wild-type controls (<jats:italic>MSTN</jats:italic><jats:sup>+/+</jats:sup>) at eight months of age as a result of myofiber hyperplasia. Interestingly, 20% <jats:italic>MSTN-</jats:italic>mutant pigs had one extra thoracic vertebra. The <jats:italic>MSTN-</jats:italic>mutant pigs will not only offer a way of fast genetic improvement of lean meat for local fat-type indigenous pig breeds, but also serve as an important large animal model for biomedical studies of musculoskeletal formation, development and diseases.</jats:p>