Microglial CX3CR1 deficiency delays the maturation of adult born neurons in the olfactory bulb

Over the past decade it became evident that microglia play important roles in brain development and plasticity. Specifically, previous studies showed that during brain development microglia actively participate in the proliferation and differentiation of newborn cells, as well as in synapse pruning, a crucial step in brain circuitry development. These developmental roles of microglia were found to be mediated by the fractalkine/CX3C receptor 1 (CX3CR1) signaling pathway. This pathway plays a major role in neuronal-microglial interactions, in which neuronally-derived fractalkine signals via CX3C receptors, which in the brain are exclusively expressed by microglia. Despite their importance in developmental processes, the role of microglia and CX3CR1 signaling in the maturation, dendritic and synapse growth of newly-born neurons during adult neurogenesis is still unknown.