Fig. 2.
Microglial identity. Microglia reside in the brain parenchyma and can be distinguished by their expression of the combination of Fcrls, Hexb, Nrros, Olfml3, P2ry12, Sall1, Tgfβ, Tgfβ receptors 1 and 2, and Tmem119. Microglial identity is maintained by signaling through Il34, NF-κB and Tgfβ. In the CNS border compartments, choroid plexus, meningeal and perivascular macrophages, otherwise known as CNS-associated macrophages (CAMs) or border-associated macrophages (BAMs), are distinct from microglia but share the expression of the transcription factors Irf8 and PU.1 in their lineage specification. Bone marrow-derived macrophages (BMDMs), which are not typically localized in the brain, share the common expression of Csf1r and Cx3cr1 with microglia and CAMs, but selectively express Batf3, Ccr2, Ly6chi, Myb and Nr4a1.