Abstract: 【Objective】 It has been well documented that myofiber type composition can profoundly influence postnatal muscle growth and meat quality, a higher content of red (oxidative) fibers in muscles exhibits excellent meat quality than muscles contain a high content of white (glycolic) fibers. However, the molecular processes that govern the expression of specific fiber type and the phenotypic characteristics of skeletal muscle remains unclear. In the present study, the transcriptional differential analysis between red and white myofiber types was firstly studied in Qingyuan partridge chickens in order to identify key factors that regulates chicken myofiber composition and transition. 【Method】A global gene expression profiling investigation was conducted to identify differentially expressed genes between red (soleus) and white (extensor digitorum longus) muscle of Qingyuan partridge chickens using the Agilent Chicken Gene Expression Chip. qRT-PCR assays were used to validate the microarray hybridization results, and lentivirural plasmids pack-aging system was used to establish a lentiviral vector for RNA interference of specific targeting chicken PPARGC1A gene to study the function of the target gene. 【Result】 A total of 1224 genes with at least 2-fold differences were identified at the P <0.05 significance level (P <0.05, FC ≥ 2). Compared with the expression of transcripts in EDL, a set of 654 transcripts belonged to the up-regulated group, and another set of 570 transcripts belonged to the down-regulated group in SOL. Although fold changes of the selected genes were not exactly the same between real-time PCR assay and microarray assay, the expression tendencies were highly consistent, suggesting that the data from microarray assay in this study was reliable. A total of 74 significantly different GO terms (P value＜0.05) were obtained. These terms were categorized into one of three categories: biological process, molecular function and cellular component. KEGG pathway analysis revealed that some well known pathways affecting muscle fiber transition, muscle development and lipid metabolism were enriched in both types of muscles. The results of the GO, KEGG pathway and gene coexpression network analysis indicated that PRKAG3, ATP2A2 and PPARGC1A might be the key genes related to chicken muscle fiber characteristics, and PPARGC1A was selected for the further functional analysis. Genes involved in the calcium signaling such as PPP3CA and MEF2C as well as MyHC SM isoform were significantly down-regulated, while MyHC FRM isoform was significantly up-regulated by PPARGC1A knockdown after shRNA interference. 【Conclusion】The analysis presented the gene expression profiles and identified DEGs that may be related to the phenotypic differences between red (SOL) and white (EDL) muscles in chickens. Further shRNA analysis demonstrated that PPARGC1A might play an important role in chicken myofiber composition and can co-activate the transcriptional activity of calcium signaling genes. Results of this study will provide new clues to understand the molecular basis of chicken myofiber composition and transition, and also will provide a theoretical basis for improving and controlling meat quality of chickens.

Key words: microarray, differential transcriptional analysis, myofiber types, PPARGC1A, chicken