Gene Expression Studies Of Pig Postnatal Skeletal Muscle Hypertrophy And Myofiber Transformation Pathway

IGF-I-mediated mTOR/PKB signaling pathway played an important role in the regulation of postnatal skeletal muscle hypertrophy,as well as CaN/NFATcl signaling pathway mediated the fast-to-slow transformation of muscle fiber type,increased the proportion of oxidative muscle fibers and contributed to good meat quality.However,the specific mechanism was uncleared.In previous study of our lab,hundreds of differentially expressed genes had been detected using DNA microarray and Suppression Subtractive Hybridization in 120d LD muscle between Yorkshire and Meishan pigs.Based on the physiological function of these differentially expressed genes in signaling pathway,eight and six functional genes were selected from IGF-I-mediated mTOR/PKB signaling pathway and CaN/NFATcl signaling pathway respectively.Isolation of sequence and analysis of temporal and spatial expression were researched.Furthmore,the 5’ flanking sequence of MYH1,MYH2,MYH4 genes which was the target of CaN/NFATcl signaling pathway was isolated and analyzed.The main findings are as follows:1.The complete CDS sequence of the GRB2 gene（GenBank:FJ196595） and partial coding region of PDK1（GenBank:FJ196594）,MEF2D（GenBank:EU878304）,FKBP5 genes were isolated and identified.Bioinformatics method was used to predict amino acid sequences of GRB2 gene.The results indicated that the conservative Sh2 and Sh3 domain existed in GRB2 protein.2.Real-time PCR was used to detect expression profile of the fourteen genes implicated in IGF-I and CaN/NFATcl pathway in six different development stages（after birth 3d,21d,35d,60d,90d,120d）.The results showed that relative expression level of the genes between Yorkshire and Tongcheng is different significantly at 60d,90d and 120d.3.The tissue distribution profile of heart,liver,spleen,lung,kidney,uterus,ovary, fat,semitendinosus muscle,biceps femoris,masseter muscle and LD muscle in adult Yorkshire were detected using semi-quantitative RT-PCR.The results indicated that GLUT4 was cardiac and skeletal muscle-specific expressed,the expression of IRS1 gene was relatively higher in skeletal muscle and the other genes were expressed in all twelve detected tissues. 4.The 5’ flanking sequence and the AT2 component of MYH1,MYH2,MYH4 genes in both Yorkshire and Tongcheng pigs were isolated.The results indicated that the sequence of AT2 component is non-breed-specific.5.PCR-AclI-RFLP was developed to detect a mutation of Tâ†'C in 5’ flanking sequence of MYH4 gene.Association between PCR-AclI-RFLP genotypes and ecnomic traits were analyzed in Large White and Meishan resource family F₂ population.The results showed:the mutation is significant associated with meat marbling（LD muscle） （p＜0.05）,and it is also significant associated with IMF（Intramuscular fat） and WM （Water moisture）（p＜0.01）.