CX3CL1 and Alzheimer disease: Beside the two last popular AD hallmark genes, recent data suggests that the fractalkine ligand and its microglial receptor (CX3CL1/CX3CR1) can influence pathologies related to tau by controlling microglial migration and attracting monocytes to the brain (Lyons et al., 2009; Joaquín Merino et al., 2016).