In a neurodegenerative mouse model of PD [144], Cx3cr1−/− mice showed increased cell death in the pars compacta of substantia nigra compared to Cx3cr1+/+ PD mice, and the same results were obtained in Cx3cl1−/− mice, suggesting that the CX3CL1-CX3CR1 axis modulates microglia activity and that alterations of this axis result in microglia perturbation, regardless of which one of them is altered. This evidence concerns the gene CX3CL1 and Parkinson disease.