Moreover, whereas in most species microglia showed a single dominant transcriptional state, human microglia displayed substantial heterogeneity [61] and, for example, responded to neurodegeneration and Alzheimer’s disease pathology by upregulation of TMEM119, P2RY12 and CX3CR1 genes, contrary to their downregulation in mouse models of the disease [62, 63]. Here, CX3CR1 is linked to Alzheimer disease.