Gcn2 deficiency triggers anemia and hypoxic intolerance in zebrafish

The Integrated Stress Response (ISR) is a critical signaling network that maintains intracellular homeostasis and enables cells to adapt to diverse stress conditions. While the ISR has been linked to ferroptosis, its physiological function in regulating hypoxic adaptation remains poorly understood. Here, we identify General Control Nonderepressible 2 (GCN2) is essential for maintaining redox homeostasis and suppressing ferroptosis. Gcn2-deficient zebrafish exhibit hypersensitivity to hypoxia, with increased mortality associated with excessive heme degradation and mitochondrial damage. Loss of Gcn2 leads to upregulation of hmox1a, reduced erythrocyte numbers, and elevated levels of free ionic iron, collectively contributing to the development of anemia. Mechanistically, loss of Gcn2 downregulates the amino acid transporter chaperone slc3a2b, resulting in disturbed cysteine metabolism. This defect impairs glutathione biosynthesis, triggering ferroptosis characterized by elevated oxidative stress and iron-dependent lipid peroxidation. GCN2-deficient also induces ferroptosis in HeLa cells. Our findings elucidate a critical role for GCN2 in protecting against ferroptosis and promoting hypoxic tolerance. Overall design: RNA-seq profiling of wild-type and gcn2-deficient zebrafish larvae under normoxic and hypoxic conditions, Three days post-fertilization (3 dpf) wild-type and gcn2-deficient zebrafish larvae were exposed to either normoxic or hypoxic conditions for 8 hours. Each condition included three biological replicates. Total RNA was extracted and subjected to poly(A)-selected RNA sequencing.