Swine PPAR-gamma 2 expression upregulated in skeletal muscle of transgenic mice via the swine Myozenin-1 gene promoter

摘要

Myozenin-1 (Myoz1) gene-encoded calsarcin-2 protein was expressed exclusively in fast-twitch muscles. Peroxisome proliferator-activated receptor gamma 2 (PPAR-gamma 2) is a key regulator of adipocyte differentiation, fatty acid uptake and storage in mammals. In this study, transgenic (TG) mice were generated by injecting linearized DNA that contained mouse creatine kinase M-type enhancer, Myoz1 core promoter, swine PPAR-gamma 2 (sPPAR-gamma 2) and SV40 polyadenylation sequences into pronuclei of fertilized FVB/NJ mouse embryos using microinjection technology. Then, the TG mice were used to identify whether swine Myoz1 (sMyoz1) promoter could upregulate sPPAR-gamma 2 expression in skeletal muscle in a TG mouse model. The results showed that the sMyoz1 promoter indeed upregulated sPPAR-gamma 2 expression on both the RNA and protein levels. The target genes of PPAR-gamma in fat formation pathways, such as fatty acid-binding protein 4 (FABP4) and lipoprotein lipase (LPL), were also overexpressed on the RNA level. Meanwhile, the level of skeletal muscle triacylglycerol in TG mice was increased (P 0.05), and the result of Oil Red-O staining in the skeletal muscle sections also showed that the number of lipid droplets was significantly increased in TG mice compared to wild-type mice, which might improve the intramuscular fat (IMF) content. For pork, the quality was mostly influenced by the IMF; the identification of swine muscle-specific promoter, sMyoz1, could further serve to develop transgenic pigs with higher intramuscular fat contents and improve pork quality.