G6PD-Mediated iron dysregulation and ferroptosis in BAG3-associated myofibrillar myopathy: a study initiated from a single rare Chinese case

BAG3 p.Pro209Leu causes severe childhood-onset myofibrillar myopathy (Bag3opathy). However, due to the extreme rarity of this disease, systematic molecular profiling in human patients remains largely unexplored to date. Here, we leveraged serum proteomics and metabolomics in the first reported Chinese patient with BAG3 p.Pro209Leu versus 30 age-matched healthy controls to identify disease-specific molecular signatures, followed by functional validation in CRISPR-generated Bag3 P215L knock-in mice and CRISPR-edited C2C12 myoblasts. At 3 months of age, Bag3 P215L knock-in mice exhibited significant muscle weakness and motor dysfunction. Patient serum showed marked reductions in antioxidant enzymes (SOD1, catalase) and pronounced glucose-6-phosphate accumulation with near-absent G6PD activity. In Bag3 P215L mice and mutant cells, G6PD activity and NADPH were reduced, labile iron and lipid peroxidation increased, mitochondria displayed ferroptosis-like ultrastructural changes, and cells were more susceptible to ferroptotic triggers. G6PD deficiency correlated with lower expression of iron chaperones PCBP1/2 and increased transferrin. Pharmacological activation or genetic restoration of G6PD partially rescued PCBP1/2 levels, normalized transferrin, reduced lipid peroxidation and improved cell survival. Collectively, our findings define a patient-driven pathogenic axis linking BAG3 mutation, G6PD deficiency, iron dysregulation, and ferroptosis, and highlight G6PD activation as a promising therapeutic strategy for this rare disease. Further studies in larger patient cohorts and longitudinal animal models are warranted.