CX3CL1 and Parkinson disease: Additionally, in a study using the CX3CR1 global KO mouse model, where CX3CR1 is replaced by GFP on all cells expressing CX3CR1, Cardona et al. (2006) showed that disruption in FKN signaling resulted in an increased loss of neurons in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of PD.