The Effects Of MSTN Deletion On Skeletal Muscle Fiber Type Relative Factors In Newborn Piglets And The Adipogenic Differentiation In Muscle

Myostatin(MSTN)is primarily expressed in muscle and plays an important role in muscle and fat development in pigs.The lack of myostatin leads to a muscle hypertrophy and increases fast fiber(type ?)formation.Several reports suggest that myogenic differentiation factor(MyoD)is required for fast fiber(type ?)formation and myocyte enhancer factor 2(MEF2)is responsible for slow fiber(type ?)formation.In order to elucidate whether MSTN gene co?ld induce muscle fiber type change by these factors or not,myostatin-knockout pigs were analyzed.Three skeletal muscles,namely the biceps femoris(BF),diaphragm(DP)and semitendinosus(ST)were excised from newborn wild-type(WT),MSTN+/-and MSTN-/-pigs.Samples were examined by hematoxylin-eosin staining and ATPase staining for histomorphology analysis.Furthermore,expression patterns of MyoD and MEF2 were detected by quantitative RT-PCR.Hematoxylin-eosin staining revealed the muscle fiber cross-sectional area(CSA)in myostatin-knockout pigs is significantly larger than in WT pigs.ATPase staining revealed increased type ? fibers with a concomitant decrease in type ? fibers in muscles of myostatin-knockout pigs.Quantitative RT-PCR res?lts revealed that MyoD expression of muscle tissue was 1.3-2 fold greater(p<0.01)in MSTN+/-pig and 1.8-3.5 fold greater(p<0.01)in MSTN-/-pig compared with wild type.However,MEF2 mRNA levels were significantly lower in MSTN+/-pig compared with wild type pig(p<0.05).The results showed that MSTN knockout cells had better adipose differentiation ability.Real time quantitative PCR,according to the results of MSTN gene knock out of fat cells development related factor expression quantity are raised,including the expression of PPARy quantity increased 1.8 fold(p<0.05),FABP4 expression quantity increased 2.5 fold(p<0.001).The aim of this experiment is designed to detect MSTN gene absence of skeletal muscle development of newborn piglets,clarify the effect of MyoD and MEF2C on the differentiation of skeletal muscle fibers in MSTN gene knockout pig,the influence of the MSTN lack of intramuscular fat differentiation potential mechanism.In conclusion,MSTN gene knockout plays an important role in skeletal muscle development,muscle fiber type differentiation and intramusc?lar fat development in newborn piglets.