Project description:This study defines a molecular interaction between neurons and microglia that drives experience-dependent synapse remodeling in the hippocampus.
Project description:This study defines a molecular interaction between neurons and microglia that drives experience-dependent synapse remodeling in the hippocampus.
Project description:Here, we used conditional cell-specific gene targeting in mice with multi-omics approaches, and demonstrated that the RhoGTPase Rac1 was an essential requirement for the microglia to sense and interpret the brain microenvironment, and for crucial microglia-synapse crosstalk driving experience-dependent plasticity. Phosphoproteomics profiling detected a large modulation of RhoGTPase signaling, predominantly of Rac1, in microglia of mice exposed to an environmental enrichment protocol. Ablation of microglial Rac1 affected pathways involved in microglia-synapse communication, disrupted experience-dependent synaptic remodeling, and blocked the gains in learning, memory and sociability induced by environmental enrichment.
Project description:Neuronal synapse formation and remodeling is essential to central nervous system (CNS) development and is dysfunctional in neurodevelopmental diseases. Innate immune signals regulate tissue remodeling in the periphery, but how this impacts CNS synapses is largely unknown. Here we show that the IL-1 family cytokine Interleukin-33 (IL-33) is produced by developing astrocytes and is developmentally required for normal synapse numbers and neural circuit function in the spinal cord and thalamus. We find that IL-33 signals primarily to microglia under physiologic conditions, that it promotes microglial synapse engulfment, and that it can drive microglial-dependent synapse depletion in vivo. These data reveal a cytokine-mediated mechanism required to maintain synapse homeostasis during CNS development.
Project description:Neuronal synapse formation and remodeling is essential to central nervous system (CNS) development and is dysfunctional in neurodevelopmental diseases. Innate immune signals regulate tissue remodeling in the periphery, but how this impacts CNS synapses is largely unknown. Here we show that the IL-1 family cytokine Interleukin-33 (IL-33) is produced by developing astrocytes and is developmentally required for normal synapse numbers and neural circuit function in the spinal cord and thalamus. We find that IL-33 signals primarily to microglia under physiologic conditions, that it promotes microglial synapse engulfment, and that it can drive microglial-dependent synapse depletion in vivo. These data reveal a cytokine-mediated mechanism required to maintain synapse homeostasis during CNS development.
Project description:The functional output of the hippocampus, a brain region subserving memory processes, depends on highly orchestrated cellular and molecular processes that regulate synaptic plasticity throughout life. The structural requirements of such plasticity and molecular processes involved in this regulation are poorly understood. Specific molecules, including tissue inhibitor of metalloproteinases-2 (TIMP2) have been implicated in serving a pro-plasticity role in the hippocampus, a role that decreases with brain aging. Here, we report that TIMP2 is highly expressed by neurons within the hippocampus and its loss drives changes in cellular programs related to adult neurogenesis and dendritic spine turnover with corresponding impairments in hippocampus-dependent memory. We find that TIMP2 regulates accumulation of extracellular matrix (ECM) around synapses in the hippocampus with concomitant hindrance in migration of newborn neurons through a denser ECM network. A conditional TIMP2 KO mouse reveals that neuronal TIMP2 regulates adult neurogenesis, accumulation of ECM, and ultimately hippocampus-dependent memory. Our results define a mechanism whereby hippocampus-dependent function is regulated by TIMP2 and its interactions with the ECM to regulate diverse processes associated with synaptic plasticity.