NPAS4 is a neuronal activity-dependent transcription factor that serves as a critical molecular link between neuronal activity and memory formation. It functions as one of the most rapidly induced immediate-early genes, being expressed exclusively in neurons and selectively activated by neuronal activity 1. NPAS4 operates through heterodimerization with bHLH-PAS family members including ARNT, ARNT2, or BMAL1 to enable efficient DNA binding 2. The protein exhibits a unique structural architecture with ordered bHLH and PAS domains while maintaining intrinsically disordered regions, and contains multiple phosphorylation sites in its PAS domains 3. NPAS4 orchestrates distinct activity-dependent gene programs in different neuronal populations, affecting synaptic connections in both excitatory and inhibitory neurons, thereby regulating neural circuit plasticity and memory formation 1. Beyond its role in learning and memory, NPAS4 demonstrates neuroprotective properties in cerebral ischemia by modulating cell death pathways and inflammatory responses 4. The transcription factor has emerged as a potential autoantigen in some cases of autoimmune limbic encephalitis, highlighting its clinical relevance in neurological disorders 5. NPAS4's broad involvement in activity-driven transcriptional programs positions it as a key regulator of neuronal plasticity and homeostasis 6.