Generation of cloned adult muscular pigs with myostatin gene mutation by genetic engineering

Skeletal muscle is the most economically valuable tissue in meat-producing animals and enhancing muscle growth in these species may enhance the efficiency of meat production. Skeletal muscle mass is negatively regulated by myostatin (MSTN), and non-functional mutations of the MSTN gene in various animal species have led to dramatic hypermuscularity. This study was designed to assess the characteristics of male MSTN-knockout (KO) pigs. A transcription activator-like effector nuclease (TALEN) pair targeting exon 1 of the swine MSTN gene was constructed and used to transfect porcine fetal fibroblasts (PFFs). We obtained a cell line consisting of a 2-bp deletion in one allele and a 4-bp deletion in the other allele, and this was used as a donor to generate cloned pigs via SCNT, and delivered 18 live piglets. They developed and grew normally to sexual maturity. These MSTN-KO boars grew normally to adulthood and showed visually-clear hypermuscular characteristics, increased carcass dressing percentage and loin eye size, and decreased backfat thickness. These pigs may show greater meat production, as well as being used in animal models of human diseases.