Transcriptome and Metabolomics Profiling of Muscle Sites in Minxian Black Fur Sheep: Unraveling the Molecular Basis of Muscle Fiber Metabolism (PRJCA021733)

Mammalian skeletal muscle is comprised of different muscle fibers characterized by patterns of gene expression that determine the different physiological and metabolic characteristics of muscle fibers. In this study, we compared the differences in muscle fiber structure and chemical composition of biceps femoris (BF), longissimus dorsi (LD), and infraspinatus (IS) muscles in Minxian black fur sheep. We comprehensively analyzed the whole transcriptome and metabolomics profiles of different muscle sites to identify genes, metabolites, and enrichment pathways related to meat quality in sheep. BF and IS muscles were characterized by significantly higher mitochondria-rich oxidative myofiber genes, which are related to mitochondrial function and lipid metabolism (e.g., matrix side of the mitochondrial inner membrane, negative regulation of fatty acid beta-oxidation, and the PPAR signaling pathway). Conversely, LD muscles mainly expressed glycolytic muscle fiber genes, which are related to amino acid metabolism and skeletal muscle growth and development (e.g., amino acid metabolism as well as skeletal muscle growth and development). This reflects the different metabolic properties among different muscle sites; that is, BF and IS muscles were comprised of oxidized muscle fibers rich in mitochondria, while LD was comprised of glycolytic muscle fibers. Furthermore, a weighted gene co-expression network analysis (WGCNA) related to amino acids was constructed to further explore the close relationship between amino acids, fatty acids, and muscle fibers. These results have contributed to establishing a theoretical foundation for our understanding of the molecular regulation mechanism of muscle metabolic patterns in different sites of Minxian black fur sheep.