Alzheimer's disease and progressive multiple sclerosis are intractable diseases of the central nervous system, and there is no effective treatments currently available to significantly improve the disease course. It has been indicated that microglia, a cell type in the brain, play a crucial role in these conditions. Microglia have both beneficial and detrimental effects on the pathology. This study aims to identify a key factor that independently regulates the beneficial and detrimental aspects of microglia, which can become a novel therapeutic target in these devastating diseases.