The Effects Of PGC1? Gene On The Muscle Fiber Conversion And Their Molecular Mechanism In Transgenic Pig Model

Pig is one of the most important domestic animals and the quality of pork is the important economic trait.The quality of meat is affected by many factors,such as tenderness,IMF,color and so on.The muscle fiber-type has a direct relationship with these factors and is the important research object in pig.So discovering the mechanism of the muscle fiber-type conversion is important for improving the meat quality traits.Peroxisome proliferator-activated receptor gamma coactivator 1 alpha(PGC1?)is a co-activator of the transcription factors.It effectively induces the biosynthesis of the mitochondria and the energy metabolism and plays a central role in the regulation of muscle fiber-type conversion.In this study,we generated the transgenic pig model to verify the effect of overexpression of PGC1? gene,which driven by MCK promoter,on muscle fiber-type conversion.And also we found the possible regulation mechanism of PGC1? by transcriptome analysis of the transgenic pigs and wild-type pigs.The results are as follow:1.Founder transgenic pigs were mated with the wild-type pigs and give birth to the F1 generation of the TG pigs.The transgenic pigs were slaughtered in three and six months old,respectively.The genotype identification was carried out by PCR.By comparing the appearance of the gastrocnemius and longissimus dorsi in the transgenic pigs with the wild-type pigs,we found that the color was a little bit redder.Production traits measurement of six months old pigs showed the drip loss was decreased significantly in the transgenic pigs.And that the other high meat quality traits also changed,such as color,marble,intramuscular fat and tenderness,but it did not reach the significant level.2.From the results of histological experiment,the increase of type?muscle fiber and the decrease of type?muscle fiber were found.Moreover,the HE staining showed that the muscle fiber number and density were increased and the muscle fiber size was decreased.In conclusion,overexpression of PGC1? promoted the type?muscle fiber transform to the type?muscle fiber.Meanwhile,the muscle fiber number and density were increased and the muscle fiber size was decreased.3.By analyzing the PGC1? expression pattern in different tissues between transgenic pigs and wild-type pigs,we found that the expression of PGC1? gene was significantly up-regulated in the gastrocnemius and longissimus dorsi,showing that the MCK promoter was specific in muscle of transgenic pigs.Moreover,the expression of PGC1? in kidney and liver was also significant.The transcript and protein expression in the gastrocnemius and longissimus dorsi of the three months and six months old transgenic pigs were detected.The results demonstrated that the expression of slow muscle fiber-specific genes(MYHC?,MYHC?A,Myog,Myoglobin,TNNI1 and CS)were up-regulated and the expression of fast muscle fiber-specific genes(MYHC?B,Myod and TNNI2)were down-regulated.The changes of PGC1?-specific genes were also observed.The expression of MEF2 C,CPT-1B,NRF-1,PPAR? and FABP3 were increased and the expression of FOXO1 and Myostatin were decreased.4.371 differentially expressed(DE)genes(P-value...