A novel role of CDK2 inhibition in restraining microglial overactivation

Intrinsic immune checkpoints in microglia are vital for maintaining homeostatic immune response and preventing overactivation. Neuroinflammation, frequently driven by microglial overactivation, significantly influences a wide range of neurological disorders. While MEF2C has been associated with a syndromic form of autism spectrum disorder (ASD) and various other neurological disorders in humans, its specific role as an immune checkpoint remains poorly defined. By harnessing MEF2C-knockout (KO) induced microglia-like cells (iMGLs) through differentiation from human pluripotent stem cells (hPSCs), here we observed that these cells, following LPS stimulation, exhibited overactivation similar to patterns seen in various neurological disorders. High-throughput screening identified BMS265246, a CDK2 inhibitor, as effective in specifically suppressing the overactivated phenotypes of MEF2C-KO iMGLs, and in restoring inflammatory response closer to normal levels. Mechanistically, we uncovered that MEF2C regulates p21 transcription, a critical step in preventing CDK2 activation in microglia. Loss of MEF2C results in CDK2-induced RB phosphorylation and degradation, leading to enhanced NF-κB p65 subunit nuclear translocation and exacerbated inflammatory responses. Remarkably, BMS265246 treatment rectified microglial overactivation and ASD-like behaviors in both global and microglia-specific Mef2C heterozygous knockout mice. Overall, our findings elucidated a previously unknown immune checkpoint mechanism governed by MEF2C, and highlighted CDK2 as a potential key factor driving neuroinflammation through microglial overactivation. These insights positions CDK2 as a promising therapeutic target for treating various neurological diseases influenced by overactivated microglia.