Developmental Characteristics of Skeletal Muscle during the Embryonic Stage in Chinese Yellow Quail (Coturnix japonica)

Simple Summary The current work revealed the developmental characteristics of skeletal muscle and the expression patterns of related regulatory genes in the embryonic stage of quails. During the embryonic stage, the weight and fiber size of the leg muscle was larger than the breast muscle. The MyoD and Pax7 genes were critical myogenic regulatory factors and were highly expressed in the middle stage of the embryonic period in breast and leg muscles. Overall, these results imply that day 12 of quail embryos may be a crucial point for muscle development. The quail is an important research model, and the demand for quail meat has been increasing in recent years; therefore, it is worthwhile investigating the development of embryonic skeletal muscle and the expression patterns of regulatory genes. In this study, the expression of MyoD and Pax7 in the breast muscle (m. pectoralis major) and leg muscle (m. biceps femoris) of quail embryos on days 10 through 17 were determined using qRT-PCR. Paraffin sections of embryonic muscle were analyzed to characterize changes over time. Results showed that MyoD and Pax7 were expressed in both breast and leg muscles and played a significant role in embryonic muscle development. Compared to breast muscle, leg muscle grew faster and had greater weight and myofiber size. The findings suggested that embryonic day 12 (E12) may be a key point for muscle development. Correlation analysis showed that MyoD expression was significantly negatively correlated with muscle and embryo weight, whereas Pax7 gene expression had no significant correlation with these characteristics. These fundamental results provide a theoretical basis for understanding the characteristics and transition points of skeletal muscle development in quail embryos and an important reference for farmers raising quail from eggs.