Frameshift mutation in myostatin gene by zinc-finger nucleases results in a significant increase in muscle mass in Meishan sows

Myostatin (MSTN) is a negative regulator of skeletal muscle growth and development. A significant increase in skeletal muscle was observed in Mstn^−/− mice compared with wild-type mice. So far, there has been no report on porcine MSTN mutations leading to skeletal muscle hypertrophy. In this report a MSTN frameshift mutation missing 11 nucleotides in exon 2 was introduced into Meishan pigs by zinc finger nuclease (ZFN) technology. ZFN-edited MSTN^−/− Meishan pigs were successfully produced by a cloning method of somatic cell nucleus transfer. Results from slaughter experiments indicated that lean meat yield increased 16.53% in about 80 kg (10-months-old) MSTN^−/− Meishan sows compared with their corresponding wild-type counterparts. The lean percentage of carcass from MSTN^−/− sows was 61.20% vs 48.25% for MSTN^+/− sows and 44.67% for wild-type sows. The fat of MSTN^−/− sows was significantly lower than that of MSTN^+/− and wild-type sows. The loin eye area of MSTN^−/− Meishan sows (56.42 cm²) was greater than that of MSTN^+/− (37.39 cm²) and wild-type (26.26 cm²) sows. The muscle fibre area of longissimus muscle in wild-type Meishan sows (1 946 μm²) was significantly greater than that of MSTN^+/− (1 324 μm²) and MSTN⁻^/− (1 419 μm²) sows. Moreover the significantly increased skeletal muscle in these MSTN^−/− Meishan sows was mainly due to the increase in the number of myofibres rather than to hypertrophy. Compared with wild-type Meishan sows, it was noted that myofibres had transformed from type I to IIB in MSTN^−/− Meishan sows. Our present study demonstrated that frameshift mutation in MSTN by ZFN technology led to a significant increase in muscle mass and a significant decrease in fat content in Meishan sows.