Project description:The role of microglia in the formation of brain capillary calcification was investigated in a platelet-derived-growth factor B (PDGFB) hypomorph - Pdgfb ret/ret mouse model of human primary familial brain calcification.
Project description:We examined the role of TREM2 on microglia responses to demyelination Microglia were FACS-purified from WT or Trem2-/- mice fed with 0.2% cuprizone diet.
Project description:We examined the role of TREM2 on microglia responses to amyloid-beta deposition in a mouse model of Alzheimer's disease Microglia were FACS-purified from 8.5 month old WT, Trem2-/-, 5XFAD, and Trem2-/- 5XFAD mice
Project description:Microglia are phagocytic cells that survey the brain and perform neuroprotective functions in response to tissue damage, but their activating receptors are largely unknown. Triggering receptor expressed on myeloid cells 2 (TREM2) is a microglial immunoreceptor whose loss-of-function mutations in humans cause presenile dementia, while genetic variants are associated with increased risk of neurodegenerative diseases. In myeloid cells, TREM2 has been involved in the regulation of phagocytosis, cell proliferation and inflammatory responses in vitro. However, it is unknown how TREM2 contributes to microglia function in vivo. Here, we identify a critical role for TREM2 in the activation and function of microglia during cuprizone (CPZ)-induced demyelination. TREM2-deficient (TREM2(-/-)) mice had defective clearance of myelin debris and more axonal pathology, resulting in impaired clinical performances compared to wild-type (WT) mice. TREM2(-/-) microglia proliferated less in areas of demyelination and were less activated, displaying a more resting morphology and decreased expression of the activation markers MHC II and inducible nitric oxide synthase as compared to WT. Mechanistically, gene expression and ultrastructural analysis of microglia suggested a defect in myelin degradation and phagosome processing during CPZ intoxication in TREM2(-/-) microglia. These findings place TREM2 as a key regulator of microglia activation in vivo in response to tissue damage. Two STAGE (6weeks 12 weeks),
Project description:Loss-of-function variants of triggering receptor expressed on myeloid cells 2 (TREM2) increase the risk of developing Alzheimer's disease (AD). The mechanism through which TREM2 contributes to the disease (TREM2 activation vs inactivation) is largely unknown. Here, we analyzed changes in a gene set downstream of TREM2 to determine whether TREM2 signaling is modified by AD progression. We generated an anti-human TREM2 agonistic antibody and defined TREM2 activation in terms of the downstream expression changes induced by this antibody in microglia developed from human induced pluripotent stem cells (iPSC). Differentially expressed genes (DEGs) following TREM2 activation were compared with the gene set extracted from microglial single nuclear RNA sequencing data of patients with AD, using gene set enrichment analysis. We isolated an anti-TREM2-specific agonistic antibody, Hyb87, from anti-human TREM2 antibodies generated using binding and agonism assays, which helped us identify 300 upregulated and 251 downregulated DEGs. Pathway enrichment analysis suggested that TREM2 activation may be associated with Th2-related pathways. TREM2 activation was lower in AD microglia than in microglia from healthy subjects or patients with mild cognitive impairment. TREM2 activation also showed a significant negative correlation with disease progression. Pathway enrichment analysis of DEGs controlled by TREM2 activity indicated that TREM2 activation in AD may lead to anti-apoptotic signaling, immune response, and cytoskeletal changes in the microglia. We showed that TREM2 activation decreases with AD progression, in support of a protective role of TREM2 activation in AD. In addition, the agonistic anti-TREM2 antibody can be used to identify TREM2 activation state in AD microglia.
Project description:Genetic studies have highlighted microglia as pivotal in orchestrating Alzheimer’s disease (AD). Microglia that adhere to Aβ plaques acquire a transcriptional signature, “diseaseassociated microglia” (DAM), which largely emanates from the TREM2-DAP12 receptor complex that transmits intracellular signals through the protein tyrosine kinase SYK. The human TREM2R47H variant associated with high AD risk fails to activate microglia via SYK. We found that SYK-deficient microglia cannot encase Aβ plaques, accelerating brain pathology and behavioral deficits. SYK deficiency impaired the PI3K-AKT-GSK3β-mTOR pathway, incapacitating anabolic support required for attaining the DAM profile. However, SYK-deficient microglia proliferated and advanced to an Apoe-expressing prodromal stage of DAM; this pathway relied on the adaptor DAP10, which also binds TREM2. Thus, microglial responses to Aβ involve non-redundant SYK- and DAP10-pathways. Systemic administration of an antibody against CLEC7A, a receptor that directly activates SYK, rescued microglia activation in mice expressing the TREM2R47H allele, unveiling new options for AD immunotherapy.
Project description:We performed brain bulk RNA-seq aiming to study how microglia TREM2-WT or TREM2-R47H expression affect the overall brain transcriptomic profiles. Using WGCNA gene network analysis, we found the presynaptic transmission pathway was dysregulated after TREM2-R47H expression, not TREM2-WT. This finding was consistent with the impaired presynaptic transmission detected by electrophysiological recording in TREM2-R47H expressing mice. In addition, dysregulated circadian pathways were also identified in TREM2-R47H mice, not in TREM2-WT mice. Altogether, our bulk RNA-seq results provide additional evidence at transcriptomics level that TREM2-R47H expression in microglia affects neuronal functions and brain networks.
Project description:The derivation of microglia from human pluripotent stem cells provides systems for understanding microglial biology and enables functional studies of neurological disease-causing mutations. We describe a robust method for the derivation and maintenance of microglia from human stem cells, which are phenotypically and functionally comparable to primary human microglia. We used stem cell-derived microglia to study the consequences of missense mutations in the microglial-expressed protein Triggering Receptor Expressed on Myeloid cells 2 (TREM2), which are causal for a frontotemporal dementia-like (FTD-like) syndrome and Nasu-Hakola disease (NHD). While many ligands and functions for TREM2 have been described, it is not known how TREM2 signalling dysregulation affects specific elements of microglial biology to influence disease pathogenesis. We find that mutant TREM2 accumulates in its immature form, does not undergo typical proteolysis, and is not properly trafficked to the plasma membrane of patient-derived microglia. However, in the absence of plasma membrane TREM2, microglia differentiate normally, respond to stimulation with lipopolysaccharide, and are phagocytically competent. These data indicate that dementia-associated TREM2 mutations have subtle effects on microglia biology, consistent with the late adult-onset of disease in individuals with these mutations.
Project description:Triggering receptor expressed on myeloid cell 2 (TREM2) is linked to neurodegenerative disease risk. However, the function of TREM in neurodegeneration is still unclear. Here we investigated the role of microglial TREM2 in TAR-DNA binding protein 43 kDa (TDP-43)-related neurodegeneration using viral-mediated and transgenic mouse models. We found that TREM2 deficiency impaired phagocytic clearance of pathological TDP-43 by microglia, and enhanced neuronal damage and motor impairments. Mass cytometry analysis revealed that hTDP-43 induced a TREM2-dependent subpopulation of microglia with high CD11c expression and phagocytic ability. Using mass spectrometry and surface plasmon resonance analysis, we further demonstrated an interaction between TDP-43 and TREM2 in vitro and in vivo as well as in ALS patient tissues. We computationally identified the region within hTDP-43 that interacts with TREM2. Our data highlights that TDP-43 is a possible ligand for microglial TREM2 and that this interaction mediates neuroprotection effects of microglia in TDP-43-related neurodegeneration.
Project description:The purpose of this project was to investigate whole genome expression in primary microglia cultured from homozygous Trem2 R47H knock-in mice versus wild type littermates under basal conditions and in response to IL-4 treatment. The primary phenotype of microglia from Trem2 R47H knock-in mice was decreased expression levels of Trem2. IL-4 induced the expression of an anti-inflammatory programme of genes in microglia, which was attenuated when Trem2 expression was decreased.