Function and Molecular Mechanism of Circhomer1 in Myogenesis.

Skeletal muscle is one of the largest tissues in the body. It is of great significance to analyze the molecular mechanism of skeletal muscle development for the further study of meat quality improvement and muscle diseases. CircRNA has been reported to be involved in many biological processes, but further research is needed in skeletal muscle. In this study, we detected the authenticity, stability, and spatio-temporal expression characteristics of circHOMER1 and its effect on the proliferation, apoptosis, and differentiation of muscle cells, and analyzed its possible molecular mechanism. The results showed that circHOMER1 exists in the skeletal muscle of the Ningxiang pig, is more stable than linear RNA, and is significantly upregulated in adipose tissue and during the early growth of myoblasts. In terms of function, overexpression of circHOMER1 significantly promoted the expression levels of proliferation marker genes and proteins and significantly increased the EdU positive cell rate, optical density (OD) value (at 450 nm), and proportion of S-phase cells. Overexpression of circHOMER1 also significantly promoted the expression levels of apoptosis marker genes and proteins and significantly increased the proportions of cells in Q2 (with late apoptosis) and Q3 (with early apoptosis). Overexpression of circHOMER1 significantly inhibited the expression levels of differentiation marker genes and proteins, significantly inhibited the differentiation index, and decreased the proportion of 5-nucleus muscle fibers. Conversely, opposite results were obtained after circHOMER1 interference. In terms of molecules mechanism, subcellular localization analysis showed that circHOMER1 was mainly distributed in cytoplasm, and mechanism analysis showed that circHOMER1 participated in myoblast development by forming a 4-element interaction network with 4 miRNAs, 2 lncRNAs, and 20 mRNAs, and possibly regulated myoblast development by encoding 79 amino acids. To sum up, we verified that circHOMER1 promoted the proliferation and apoptosis of myoblasts and inhibited their differentiation. It may regulate the development of myoblasts through ceRNA or by encoding small peptides. These results provided a reference for the regulation mechanism of muscle development and the breeding of Ningxiang pigs.