UFL1 deficiency impairs skeletal muscle development by activating PERK/eIF2α/ATF4/CHOP pathway-dependent apoptosis

Ubiquitin-like modifier 1 ligating enzyme 1 (UFL1), the essential E3 ligase in the UFMylation system, plays a crucial yet undefined role in skeletal muscle development. In this study, our primary objective was to elucidate the function and molecular mechanism of UFL1 in myoblast survival and myofiber development. UFL1 deficiency in mice exacerbated ultra structural damage in myofibers and significantly increased myoblast apoptosis both in vivo and in vitro, as evidenced by upregulation of Cleaved Poly (ADP-ribose) polymerase (cleaved PARP), Cleaved Cysteinyl aspartate specific proteinase 3 (cleaved Caspase-3), and BCL2-associated X protein (BAX), alongside downregulation of B-cell lymphoma 2 (BCL2). Mechanistically, UFL1 knockout robustly activated the ER stress response, characterized by a significant increase in mRNA levels of Glucose-regulated protein 78 (GRP78), Activating transcription factor 4 (ATF4), and C/EBP homologous protein (CHOP), as well as specific activation of the Protein kinase R (PKR)-like endoplasmic reticulum kinase (PERK)/Eukaryotic translation initiation factor 2 subunit alpha (eIF2α)/ATF4/CHOP signaling axis. Conversely, UFL1 overexpression effectively suppressed this pathway and reduced apoptosis. Notably, treatment with the PERK inhibitor GSK2606414 successfully reversed the UFL1 deficiency-induced upregulation of p-PERK, p-eIF2α, ATF4, and CHOP and rescued the apoptotic phenotype. Our study demonstrates for the first time that UFL1 is a critical regulator for maintaining myoblast survival and normal myofiber development, acting partly through suppressing the PERK-mediated ER sress. These findings provide novel insights into the pathogenesis of muscle developmental disorders and suggest UFL1 as a potential therapeutic target.