Deletion of SPI1 in microglia exacerbates amyloid pathology by impairing microglial response in Alzheimer’s disease models

Recent human genetic studies have highlighted the potential role of microglial genes and their regulatory functions in the pathogenesis of Alzheimer's disease (AD). The transcription factor PU.1 (encoded by SPI1) is expressed mainly in microglia in the central nervous system and has been reported to be a genetic risk factor for AD. However, the role of microglial SPI1 in AD etiology is still poorly understood. Here, we demonstrate that the selective deletion of Spi1 in microglia exacerbates AD-related pathologies in an amyloid mouse model. Specifically, microglial Spi1 deletion increases amyloid deposition, gliosis, and dystrophic neurites while decreasing the microglial response to plaques. By combining proteomics and functional analyses, we reveal that the loss of microglial Spi1 impairs phagocytosis through Syk, Lyn, and Fcgr1. Furthermore, directly activating these genes rescues the impaired amyloid-beta (Aβ) uptake caused by Spi1 knockdown, unveiling the potential mechanism of SPI1 in amyloid pathology.