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. The gene discussed is CX3CR1; the disease is Parkinson disease.