Overexpression of Syndecan-4 inhibits myogenesis by regulating the expression of myogenic regulatory factors

Syndecan-4, a type of heparin sulfate proteoglycan, plays an important role in muscle development, regeneration, and maintenance. Although, the important effects of <italic>syndecan-4</italic> on the regulation of myogenesis in mice, turkeys, and bovines have been consistently reported, the molecular mechanisms of <italic>syndecan-4</italic> in myogenesis are not well understood. In this study, the role of <italic>syndecan-4</italic> in regulating myogenesis was investigated in QM7 cells, which constitute a quail myogenic cell line. Overexpression of <italic>syndecan-4</italic> inhibited myogenesis, resulting in reduced myoblast fusion and shorter myotubes than in the control group. Therefore, the cells overexpressing <italic>syndecan-4</italic> showed a smaller total myotube area than did the control cells. Furthermore, these cells had lesser myosin heavy chain proteins, suggesting that muscle differentiation is inhibited by <italic>syndecan-4</italic>. To investigate the inhibitory effect of <italic>syndecan-4</italic> on myogenic differentiation, the mRNA expression levels in several genes known to regulate myoblast proliferation and differentiation were compared. Myogenic regulatory factors, including <italic>myogenic factor 5</italic>, <italic>myogenic differentiation 1</italic>, and <italic>myogenin</italic>, showed significantly different expressions between the groups during myogenesis. <italic>Myostatin</italic>, a negative regulator of muscle growth, showed significantly higher expression on day 4 in cells overexpressing <italic>syndecan-4</italic>. In conclusion, <italic>syndecan-4</italic> could delay and inhibit muscle differentiation by regulating the expression levels of myogenic factors and muscle growth regulator in quail myocytes. This study provides valuable information regarding the role of <italic>syndecan-4</italic> in myogenesis, which may aid in improving the production of poultry meat.