Single‐nucleus RNA sequencing reveals RUNX1 regulation of muscle hypertrophy through PI3K/AKT/mTOR pathway

We used snRNA-seq to construct a high-resolution atlas of pectoral muscle development in broiler chickens from neonatal to adult stages. This analysis revealed pronounced molecular heterogeneity among satellite cells across developmental phases and uncovered a previously uncharacterized <i>Runx1</i> ⁺ satellite cell subpopulation. By integrating pseudotime trajectory reconstruction, gene set enrichment analysis, dynamic expression profiling and loss-of-function assays, we established a critical regulatory role for RUNX1 in muscle hypertrophy. Mechanistically, RUNX1 promotes myotube hypertrophy by transcriptionally repressing <i>Pik3r1</i>, thereby reducing PI3K p85α levels, destabilizing PTEN, and activating the PI3K/AKT/mTOR signaling cascade, which enhances protein synthesis and drives myotube growth.