Microglial ontogeny, diversity and neurodevelopmental functions

Microglia are instrumental to the development, function, homeostasis and pathologies of the central nervous system. These brain-resident macrophages arise early in embryogenesis and seed the developing brain, where they differentiate in response to cues provided by their neural niche. Throughout life, microglia regulate the neural tissue through a variety of cellular functions influenced by intrinsic and extrinsic factors. Despite their importance, we are only starting to uncover how microglia colonize the brain, adopt distinct functional states during development and the long-term impact of early alteration of their functions. This review highlights the latest knowledge on the ontogeny of microglia, their developmental trajectory and emerging roles. Characterizing these processes will be critical for our understanding of both brain physiology and pathologies.