CX3CR1 and Parkinson disease: Cardona et al.[81], using CX3CR1+/- and CX3CR1-/- mice, demonstrated an inverse relationship between CX3CR1 expression and neurotoxic activation of microglia in three different models of neurodegeneration, including the MPTP model of PD, a transgenic model of amyotrophic lateral sclerosis, and systemic LPS injections.