Stage-specific gene expression and MEK-dependent ECM regulation in chicken muscle development

This study aimed to explore the conserved regulatory mechanism underlying muscle development by performing a comparative transcriptomic analysis of breast muscles at 5 and 10 weeks of age in Cornish (broiler) and Ogye (Korean indigenous) chickens. Using RNA sequencing, we identified 199 DEGs between the two time points, with 135 upregulated and 64 downregulated genes (P<0.05, (|log₂FC| ≥ 1)). Gene set enrichment analysis showed activation of pathways involved in cell multiplication and receptor signaling in 10-week-old chickens. For example, “cell differentiation,” “regulation of response to stimulus,” and “cellular developmental process” were enriched.  On the other hand, pathways related to energy metabolism, such as “ATP biosynthetic process” and “proton-transporting synthase complex,” were suppressed, indicating a metabolic shift as the birds grow. KEGG pathway analysis demonstrated significant enrichment of extracellular matrix (ECM)-receptor interaction and focal adhesion pathways. Key structural genes, including collagen (<italic>COL6A1</italic>, <italic>COL6A2</italic>, <italic>COL6A3</italic>), integrin (<italic>ITGA11</italic>), and laminin (<italic>LAMA1</italic>, <italic>LAMB2</italic>), were upregulated. We also confirmed increased expression of myogenic regulatory factors <italic>PAX7</italic> and <italic>MyoD</italic> in the 10-week-old Cornish and Ogye chickens. Functional analysis using primary chicken myoblasts treated with MAPK pathway inhibitors (p38, JNK, MEK) revealed that all three pathways regulated <italic>PAX7</italic> and <italic>MyoD</italic> expression. Notably, MEK inhibition specifically reduced the expression of <italic>collagen type VI alpha 3 chain</italic> (<italic>COL6A3</italic>) and <italic>coiled-coil domain-containing protein 80 </italic>(<italic>CCDC80</italic>) in a dose-dependent manner. These findings reveal that MEK signaling critically regulates myogenic factors and ECM-related genes during muscle development. Thus, our findings offer new insights that could contribute to the regulation of muscle growth in commercial poultry.