Transcriptional regulation of disease-relevant microglial activation programs.

Microglia, the brain's innate immune cells, can adopt a wide variety of activation states relevant to health and disease. Dysregulation of microglial activation occurs in numerous brain disorders, and driving or inhibiting specific states could be therapeutic. To discover regulators of microglial activation states, we conducted CRISPR interference screens in induced pluripotent stem cell (iPSC)-derived microglia for inhibitors and activators of six microglial states. We characterized 31 regulators at the single-cell transcriptomic and cell-surface proteome level in two distinct iPSC-derived microglia models, uncovering protein markers of relevant states. We functionally characterized several multi-state regulators. ZNF532 and PRDM1 knockdown drive disease-associated, lipid-rich signatures and enhance phagocytosis while showing opposing effects on antigen-presentation signatures. DNMT1 knockdown results in widespread loss of DNA methylation, activating negative regulators of interferon signaling. These findings provide a framework to direct microglial activation to selectively enrich microglial activation states, define their functional outputs, and inform future therapies.