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

Abstract

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.

Keywords: embryo; mRNA expression; myofiber; myogenesis; quail.

Figure 1

Embryo weight, breast weight (BW), and leg weight (LW) at each embryonic age. (A) embryo weight, (B) breast weight and leg weight.

Figure 2

The photomicrographs of paraffin sections of breast and leg muscles of quails on embryonic day 10 (E10), 11 (E11), 12 (E12), 13 (E13), 14 (E14), 15 (E15), 16 (E16), and 17 (E17). The slices were all made under the same conditions (H&E, 400×).

Figure 3

The diameter, cross-sectional area, and density of muscle fibers in breast and leg muscles of quails. (A) diameter, (B) cross-sectional area, (C) density. Different lowercase letters denoted that the difference was significant among different embryonic ages for the same tissue (p < 0.05). A superscript asterisk (*) indicates that the difference was significant between different tissue on the same embryonic day (p < 0.05), and no asterisk indicates no significant difference.

Figure 4

The expression levels of MyoD and Pax7 in the breast and leg muscles of quail embryos. (A) MyoD mRNA, (B) Pax7 mRNA. Different lowercase letters denoted that the difference was significant among different embryonic ages for the same tissue (p < 0.05).