PAX7 is a transcription factor that functions as a master regulator of skeletal muscle stem cell (satellite cell) fate and muscle regeneration. As a DNA-binding transcription factor, PAX7 controls the balance between satellite cell self-renewal and differentiation through sequence-specific binding to homeodomain motifs 1. PAX7 expression marks both dormant (PAX7High) and activated (PAX7High/MYOD1+) myogenic progenitor states during fetal development and post-natal muscle homeostasis 2. Mechanistically, PAX7 acetylation by MYST1 (stimulated by Acetyl-CoA) promotes its transcriptional activity and asymmetric satellite cell division, while SIRT2-mediated deacetylation (activated by NAD+) modulates this activity 1. PAX7+ satellite cells support muscle fiber regeneration and form specialized niches with regenerating myofibers expressing ACTC1 3. Exercise increases PAX7+ satellite cell numbers and promotes myogenic differentiation, contributing to muscle hypertrophy and strength gains 45. Clinically, PAX7 dysfunction associates with congenital myopathy 19, while PAX3/7-FOXO1 fusion proteins in alveolar rhabdomyosarcoma drive aggressive tumor growth through altered mitochondrial metabolism and leucine dependency 6. PAX7 expression is reduced in obesity-related muscle dysfunction and restored by exercise training, improving metabolic health and regenerative capacity 78.