IL-33-PU.1 Transcriptome Reprogramming Drives Functional State Transition and Clearance Activity of Microglia in Alzheimer's Disease

Summary: Impairment of microglial clearance activity contributes to beta-amyloid (Aβ) pathology in Alzheimer’s disease (AD). While the transcriptome profile of microglia directs microglial functions, how the microglial transcriptome can be regulated to alleviate AD pathology is largely unknown. Here, we show that injection of interleukin (IL)-33 in an AD transgenic mouse model ameliorates Aβ pathology by reprogramming microglial epigenetic and transcriptomic profiles to induce a microglial subpopulation with enhanced phagocytic activity. These IL-33-responsive microglia (IL-33RMs) express a distinct transcriptome signature that is highlighted by increased major histocompatibility complex class II genes and restored homeostatic signature genes. IL-33-induced remodeling of chromatin accessibility and PU.1 transcription factor binding at the signature genes of IL-33RM control their transcriptome reprogramming. Specifically, disrupting PU.1-DNA interaction abolishes the microglial state transition and Aβ clearance that is induced by IL-33. Thus, we define a PU.1-dependent transcriptional pathway that drives the IL-33-induced functional state transition of microglia, resulting in enhanced Aβ clearance. : Lau et al. show that interleukin-33 (IL-33) enhances microglial amyloid-beta clearance by inducing a subpopulation of MHC-II+ phagocytic microglia, which is, in turn, controlled by PU.1-dependent transcriptome reprogramming. Thus, the authors reveal an IL-33-PU.1 axis involved in transcriptional regulation that promotes beneficial microglial functions in Alzheimer’s disease. Keywords: chemotaxis, phagocytosis, interleukins, beta-amyloid, disease-associated microglia, MHC-II, epigenetics, PU.1, single-cell RNA-sequencing, chromatin accessibility