CX3CR1 Modulates Migration of Resident Microglia Towards Cortical Laser-Induced Lesions

Microglia are innate immune cells of the central nervous system (CNS). They extend their processes and migrate toward injuries in vivo. However, how the fractalkine receptor (CX3CR1) influences microglial migration remains unknown. Label-free proteomic profiling predicted changes in Ras homology family (RHO)-signaling activity that hint at dysregulated cytoskeleton signaling in Cx3cr1-deficient murine cortex tissue. To further investigate microglial migration, we carried out two-photon in vivo imaging at 4-h intervals for 72 h after a laser lesion in the cortex. Cx3cr1-deficient microglia showed enhanced migration toward the lesion. Additionally, the length and velocity of microglial fine processes extending toward the lesion were increased in Cx3cr1-deficient microglia. Migration remained unchanged in Ccr2-deficient mice, indicating that monocyte-derived macrophages/microglia did not contribute to microglia accumulation around the lesion. These results demonstrate that CX3CR1 modulates microglia migration toward laser-induced CNS injury. Manipulating microglia migration via the CX3CR1 signaling axis is therefore a potential target for the treatment of CNS injury.