In the mouse, several microglia-specific genes appear to be upregulated in brain-resident microglia through early postnatal development 10. For example, SELPLG, CST3, TXNIP, P2RY13, OLFML3 are upregulated (respectively 16, 11, 9, 5 and 5-fold) between embryonic day 17 and postnatal day 60. In our cultures, we find that SELPLG, CST3 and TXNIP are already expressed at high levels in both FMGs and pMGLs, while OLFML3 and P2RY13 are more than 4-fold higher in pMGLs compared to FMGs. We also note that pMGLs display high expression of both PU.1 and IRF8, but very low levels of MYB (Suppl. Fig 3a) consistent with microglia emerging from PU.1 and IRF8-dependent, but MYB-independent cells 34–37.
