UFL1, expressed in fast-twitch fibers, correlates with lipid metabolism in bovine muscles.

Although UFMylation is implicated in skeletal muscle development, the role of its E3 ligase, ubiquitin-fold modifier 1 ligase 1 (UFL1), in bovine muscle and myofiber type determination is unclear. We profiled UFL1 expression in four muscles (biceps femoris (BF), longissimus dorsi (LD), trapezius (TR), psoas major (PM)) from 18-month-old Simmental and Angus bulls via histology, RT-qPCR, western blotting, and immunofluorescence. UFL1 mRNA and protein were significantly higher in fast-twitch muscles (LD, BF) than in slow-twitch PM. UFL1 localized to sarcolemma and sarcoplasmic reticulum, co-localized with MYHC-Fast in LD, and correlated positively with MYHC-Fast. Oxidative PM showed higher SDH/MDH activities, lower LDH activity, and greater lipid deposition than glycolytic LD. UFL1 correlated negatively with PLIN2. LD exhibited lower ACC1, FASN, PPARα, and CPT1A levels than PM. Collectively, UFL1 is specifically expressed in fast-twitch fibers, associates with lipid metabolic reprogramming, suggesting a role in muscle development and meat quality. This study identifies UFL1 as a novel candidate regulator of myofiber type determination in beef cattle.