The role of ATF4 in neurons under mitochondrial stress.

Mitochondrial dysfunction and fragmentation are observed in various circumstances, such as neurodegeneration and aging. Studies have shown that altered mitochondrial function activates the integrated stress response (ISR), with ATF4 serving as a major mediator of adaptation to stress. Presently, little is known about the role of ATF4 in neurons under mitochondrial stress. Using primary cortical neurons, we demonstrate that inhibiting ATF4 under OPA1-mediated mitochondrial stress accelerates the impairment of neuronal differentiation, as evidenced by smaller dendrites and lower dendritic spine density. To better understand the role of ATF4 in this context, we investigated the global binding sites of ATF4 using chromatin immunoprecipitation sequencing (ChIP-seq) and examined the chromatin accessibility changes that occur following the loss of ATF4 in neurons under conditions of mitochondrial stress. We found that ATF4 binds to a wide range of targets and alters the chromatin accessibility of genes involved in metabolism, neuronal fate, and neuron maturation. The downstream targets of ATF4 identified in this study can reveal novel and direct targets of ATF4 in neuronal survival and maturation. These adaptations are the hallmarks of stress response in mitochondrial dysfunction-mediated neurodegeneration.