Optineurin Shapes Basal and LPS-Induced Transcriptomes in BV2 Microglia

: The OPTN gene, which encodes the adaptor protein optineurin, is genetically linked to amyotrophic lateral sclerosis and frontotemporal dementia, diseases characterized by chronic microglial activation. Optineurin regulates inflammatory signaling, autophagy, and trafficking, but its role in microglia remains incompletely understood. Here, we used bulk RNA sequencing to profile CRISPR-Cas9-mediated optineurin knockout (KO) and wild-type BV2 microglia under basal conditions and upon LPS stimulation. At baseline, optineurin KO altered ~7% of the transcriptome, with a predominant downregulation of type I interferon and antiviral pathways, suggesting its role in maintaining basal immune readiness. LPS stimulation reprogrammed ~35% of genes in wild-type microglia, inducing immune effectors and suppressing cell cycle regulators, whereas in optineurin-deficient cells, the response was blunted with only ~16% of genes changing relative to the KO baseline. Furthermore, LPS-treated optineurin KO microglia notably diverged from LPS-treated wild-type cells, with ~26% differentially expressed genes (DEGs). This included impaired induction of inflammatory programs and persistence of cell cycle-associated transcripts. Most DEGs in LPS-treated KO cells were unique to this condition, highlighting optineurin-dependent pathways specific to inflammatory challenge. Overall, our study provides a systems-level framework for investigating optineurin in microglia and neurodegeneration, establishing it as a key regulator of the microglial transcriptome, with its loss reshaping innate immune and cell cycle programs.