Definition of a mouse microglial subset that regulates neuronal development and pro-inflammatory responses in the brain

Expression of Itgax (encoding the CD11c surface protein) and Spp1 (encoding OPN) have been associated with activated microglia that can develop in healthy brains and some neuroinflammatory disorders. Here, we show that OPN production in the brain is confined to a small CD11c+ microglial subset that differentiates from CD11c- precursors in perinatal life after uptake of apoptotic neurons. Our analysis suggests that co-expression of OPN and CD11c genes marks a microglial subset that is expressed at birth and persists into late adult life, independent of environmental activation stimuli. Definition of OPN-producing CD11c+ microglia as a functional microglial subset provides new insight into microglial differentiation in health and disease. Microglial mRNA profiles of CD11c+ subset versus CD11c- subset in postnatal day 5 (P5), 9-month old wild type (WT) mice.