Dataset Information

The regional mouse microglial transcriptome during aging

ABSTRACT: Microglia are the specialised macrophages of the central nervous system parenchyma. Diversity in macrophages is increasingly apparent in tissues outside the brain however understanding is negligible for microglia. In the present study, we present the first genome-wide analysis of microglia from discrete brain regions that reveals their multiple region-dependent transcriptional identities. Differences in bioenergetic and immunoregulatory pathways are the major sources of transcriptional heterogeneity. Region-specific differences in immunophenotype suggest cerebellar and hippocampal microglia exist in a more immune vigilant state, but distinct from the conventional M1/M2 paradigm of activation. Functional responses correlate with regional transcriptional immunophenotypes. We also show that region-dependent differences in microglial immunophenotype are superimposed upon a core profile distinguishing all microglia from systemic macrophages. We suggest microglial diversity may enable microglia to accomplish their wide-ranging homeostatic functions but could also underlie region-specific sensitivity to neuroinflammatory-mediated degeneration. During ageing key findings were made regarding the reinforcement of a specific cerebellar immunophenotype and a contrasting loss in the distinction of the phenotype of the hippocampus. The present dataset provide an extensive underpinning resource for future studies to further define how microglial diversity influences the healthy, ageing and diseased brain.

ORGANISM(S): Mus musculus

PROVIDER: GSE62420 | GEO | 2015/10/01

SECONDARY ACCESSION(S): PRJNA264067

REPOSITORIES: GEO

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Project description:Microglia colonize the brain parenchyma at early stages of development and accumulate in specific regions where they actively participate in cell death, angiogenesis, neurogenesis and synapse elimination. A recurring feature of embryonic microglial distribution is their association with developing axon tracts which, together with in vitro data, supports the idea of a physiological role for microglia in neurite development. Yet the demonstration of this role of microglia is still lacking. Here, we have studied the consequences of microglial dysfunction on the formation of the corpus callosum, the largest connective structure in the mammalian brain, which shows consistent microglial accumulation during development. We studied two models of microglial dysfunction: the loss-of-function of DAP12, a key microglial-specific signaling molecule, and a model of maternal inflammation by peritoneal injection of LPS at E15.5. We performed transcriptional profiling of maternally inflamed and Dap12-mutant microglia at E17.5. We found that both treatments principally down-regulated genes involved in nervous system development and function, particularly in neurite formation. We then analyzed the functional consequences of these microglial dysfunctions on the formation of the corpus callosum. We also took advantage of the Pu.1-/- mouse line, which is devoid of microglia. We now show that all three models of altered microglial activity resulted in the same defasciculation phenotype. Our study demonstrates that microglia are actively involved in the fasciculation of corpus callosum axons. To investigate possible roles for microglial during brain development, we challenged microglial function by two complementary approaches. First, we induced maternal inflammation by peritoneal injection of LPS into pregnant dams. Next, we analyzed the consequences of a loss of function of DAP12, a signaling molecule specifically expressed in microglia that is crucial for several aspects of microglia biology (references in Wakselman et al., 2008). We compared the gene expression profiles of microglia from control, maternally-inflamed by LPS (MI), and Dap12-mutated embryos. We isolated RNA from FACS sorted maternally inflamed (by LPS) and Dap12-mutant microglia at E17.5 pooled per pregnant dam; as a control we included PBS treated and untreated (UT) microglia. We compared gene expression between maternally inflamed microlgia (PBSvsLPS) and DAP12-mutant microglia (UTvsDAP12KO).

Dataset Information

The regional mouse microglial transcriptome during aging

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