Characterization of muscle development and gene expression in early embryos of chicken, quail, and their hybrids.

Myogenesis is a complex, regulated process that involves myoblast proliferation, migration, adhesion, and fusion into myotubes. To investigate early development of embryonic muscles and the expression of regulatory genes during myogenesis in chicken, quail and their hybrids, meat-breeding cocks and egg-breeding cocks were selected as male parents, quails were used as female parents. Their offspring were meat and egg hybrids via Artificial insemination. We measured expression of MUSTN1, IGF-1, and PDK4 using qRT-PCR. We examined muscle fiber diameter using scanning electron microscopy. The results showed that muscle development was two days slower in chicken, egg hybrid, and meat hybrid than in quail. Muscle fiber spacing was the largest in chicken, followed by meat hybrid, egg hybrid, and quail. A similar trend was obtained for muscle fiber diameter. Additionally, muscle fiber diameter increased with embryogenesis. The sarcomere was present on day 17 of incubation in quail, but not in the other species. MUSTN1 could up-regulated IGF-1 by activating PI3K/Akt. IGF-1 expression was consistent with myoblast proliferation and myotube fusion. PDK4 was expressed from E7 to E17. The first peak was reached on E10, egg hybrid and meat hybrid reached their peak at E15. PDK4 is involved in the early proliferation and differentiation of muscle, thereby affecting muscle growth and development. Our findings demonstrated that MUSTN1, IGF-1 and PDK4 genes are expressed to varying levels in breast muscle of chicken, quail, egg hybrid and meat hybrid during the embryonic period. Interestingly, with increasing embryonic age, muscle development was approximately 48 h faster in quail than in other species. We speculated that MUSTN1, IGF-1 and PDK4 genes may be the main candidate genes that cause differences in poultry muscle traits, but the molecular regulation mechanisms need to be further studied. Our findings shed some light on the avian embryo muscle formation and molecular breeding of poultry muscle traits, which provide theoretical basis for poultry breeding.