Overexpression of the QKI Gene Promotes Differentiation of Goat Myoblasts into Myotubes

SIMPLE SUMMARY: Meat goats are highly valued as excellent sources of lean dietary muscle-protein. However, the molecular mechanisms by which muscle cells and tissues are generated and the genes and signaling pathways regulating this process in meat goats are poorly understood. The present study applied currently conventional molecular-genetics methods and determined that the major isoform of the QKI gene drive the conversion of embryonic myoblast cells into mature muscle fiber and tissue. These genes activate other genetic factors and signaling pathways that are all implicated in the differentiation of muscle progenitor cells and the formation of mature, differentiated muscle tissue. Although future investigations will be necessary to elucidate the entire molecular mechanism involved, we believe that the discoveries reported herein will facilitate the genetic engineering of novel goat lines with enhanced musculature and, by extension, superior meat yield and quality, breeder profitability, and consumer satisfaction. ABSTRACT: The QKI genes encode RNA-binding proteins regulating cell proliferation, differentiation, and apoptosis. The Goat QKI has six isoforms, but their roles in myogenesis are unclear. In this study, the six isoforms of the QKI gene were overexpressed in goat myoblast. Immunofluorescence, qPCR and Western blot were used to evaluate the effect of QKI on the differentiation of goat myoblast. An RNA-Seq was performed on the cells with the gain of the function from the major isoforms to screen differentially expressed genes (DEGs). The results show that six isoforms had different degrees of deletion in exons 6 and 7, and caused the appearance of different types of encoded amino acids. The expression levels of the QKI-1 and QKI-5 groups were upregulated in the biceps femoris and latissimus dorsi muscle tissues compared with those of the QKI-4, QKI-7, QKI-3 and QKI-6 groups. After 6 d of myoblast differentiation, QKI-5 and the myogenic differentiators MyoG, MyoD, and MyHC were upregulated. Compared to the negative control group, QKI promoted myotube differentiation and the myoblasts overexpressing QKI-5 formed large, abundant myotubes. In summary, we identified that the overexpression of the QKI gene promotes goat-myoblast differentiation and that QKI-5 is the major isoform, with a key role. The RNA-Seq screened 76 upregulated and 123 downregulated DEGs between the negative control and the QKI-5-overexpressing goat myoblasts after d 6 of differentiation. The GO and KEGG analyses associated the downregulated DEGs with muscle-related biological functions. Only the pathways related to muscle growth and development were enriched. This study provides a theoretical basis for further exploring the regulatory mechanism of QKI in skeletal-muscle development in goats.