Stage-Specific NF-κB RelA and IRF4 Programs Drive α-Synuclein–Induced Disease-Associated Microglia Differentiation

Abstract Microglial activation in response to aggregated α -synuclein ( α -syn) accumulation is a pathological hallmark of Parkinson’s disease (PD). A distinct activated microglial state, disease-associated microglia (DAM), has been identified across multiple neurodegenerative disorders, including PD. However, the transcriptional and epigenetic programs governing DAM differentiation remain unclear. Here, we show that neuronal α -syn overexpression drives progressive microglial state transitions toward DAM, accompanied by increased phagocytic activity and enhanced cytokine and chemokine production. Integrative transcriptomic and chromatin accessibility analyses reveal a hierarchical NF-κB–AP-1–IRF regulatory program underlying these state transitions. Microglial NF-κB p65 (RelA) or IRF4 deficiency impairs microglial progression toward DAM, with RelA and IRF4 governing early microglial activation and subsequent DAM differentiation, respectively. Enrichment of NF-κB, AP-1, and IRF motifs in DAM in human PD supports conservation of this regulatory program across species. Together, our findings establish RelA and IRF4 as sequential, stage-specific regulators that coordinate α -syn-induced DAM differentiation in PD.