Abstract

Microglia, the main resident immune cells of the brain, can undergo major cellular and transcriptomic changes, a remarkable feature observed during development, ageing and disease. Over the past decades, microglia were shown to have key and diverse roles in brain wiring and their dysfunction has been linked to the etiology of almost all brain disorders, from neurodevelopment to neurodegeneration. Thus, grasping how and when microglia shape circuits is important for both neurobiologists and clinicians. Our goal is to explore the contribution of microglia to early brain development, when these cells constitute a major glial population. Here, we will summarize published and unpublished work highlighting emerging roles of microglia in the developing brain, including a novel role in the maintenance of tissue integrity. We will discuss the implications for neurodevelopmental disorders and, more broadly, using normal development to decrypt the kaleidoscope of microglial activities and states.