Project description:Polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL) is an inherited brain and bone disease. It manifests as dementia and bone fractures. The PLOSL phenotype is caused by loss-of-function mutations in one of the two genes encoding the components of the DAP12/TREM2 receptor complex. The DAP12/TREM2 complex is expressed in cells of the myeloid lineage, including microglia in the central nervous system (CNS). The molecular mechanisms producing the CNS phenotype of PLOSL remain largely unknown. To gain insight into dysfunctional CNS pathways behind PLOSL, we performed genome-wide expression analysis of Dap12 (Tyrobp)-deficient mouse brain. In Dap12-deficient mice, we observed alterations in several pathways involved in synaptic function. In agreement with the myelin loss in PLOSL patients, we also saw changes in transcript levels of genes encoding myelin components. Keywords: knockout response Transcript profiles of the midbrain (diencephalon and basal ganglia) of three Dap12-knockout and three heterozygous mice were analyzed.
Project description:TDP-43 proteinopathy is a hallmark of neurodegenerative disorders such as amyotrophic lateral sclerosis and frontotemporal dementia where mislocalization of TDP-43 has been observed in neurons and glial cells. However, the role of TDP-43 in microglia and the consequences of its loss-of-function remain unexplored. Combining magnetic resonance imaging, confocal, and electron microscopy we uncovered structural changes and myelin abnormalities in the early postnatal brain of mice lacking microglial TDP-43. Spatial transcriptomics further revealed an enriched interferon-response signature associated with oligodendrocyte dysfunction. Early microglial TDP-43 depletion resulted in motor deficits in adult mice. Mechanistically, knocking out TDP-43 impaired microglial ability to engulf and degrade myelin. It also led to cryptic exon inclusion in the Tyrobp mRNA, resulting in truncated DAP12 protein, thus causing defective TREM2 signaling. Our findings reveal a novel role for TDP-43 in regulating the TREM2-DAP12 axis in mice, highlighting a previously unrecognized mechanism by which TDP-43 controls microglial function.
Project description:Polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL) is an inherited brain and bone disease. It manifests as dementia and bone fractures. The PLOSL phenotype is caused by loss-of-function mutations in one of the two genes encoding the components of the DAP12/TREM2 receptor complex. The DAP12/TREM2 complex is expressed in cells of the myeloid lineage, including microglia in the central nervous system (CNS). The molecular mechanisms producing the CNS phenotype of PLOSL remain largely unknown. To gain insight into dysfunctional CNS pathways behind PLOSL, we performed genome-wide expression analysis of Dap12 (Tyrobp)-deficient mouse microglial cells. Keywords: knock-out response Transcript profiles of three wild type and three Dap12-deficient primary microglial cultures were analyzed.
Project description:DAP12 is a transmembrane protein, expressed as a disulfide-bonded homodimer and bears an immunoreceptor tyrosine-based activation motif (ITAM). DAP12 is broadly expressed in hematopoietic cells and associates with a variety of cell surface receptors in lymphoid and myeloid cells. Macrophages express several DAP12-associated receptors including triggering receptors expressed by myeloid cells (TREM)-1,2 and 3, myeloid DAP12-associating lectin (MDL)-1, CD200R like proteins CD200R3/R4 and CD300C/D/E . Experiment Overall Design: The current experiment was designed to evaluate the effect of DAP12 knockdown on macrophage gene expression, both in basal conditions and in the response to IL-4.
Project description:Polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL) is an inherited brain and bone disease. It manifests as dementia and bone fractures. The PLOSL phenotype is caused by loss-of-function mutations in one of the two genes encoding the components of the DAP12/TREM2 receptor complex. The DAP12/TREM2 complex is expressed in cells of the myeloid lineage, including microglia in the central nervous system (CNS). The molecular mechanisms producing the CNS phenotype of PLOSL remain largely unknown. To gain insight into dysfunctional CNS pathways behind PLOSL, we performed genome-wide expression analysis of Dap12 (Tyrobp)-deficient mouse brain. In Dap12-deficient mice, we observed alterations in several pathways involved in synaptic function. In agreement with the myelin loss in PLOSL patients, we also saw changes in transcript levels of genes encoding myelin components. Keywords: knockout response
Project description:Microglia, the primary immune cell in the brain, have multiple activation phenotypes involved in broad functions within the brain, playing roles in neurotoxicity/neuroprotection, release of inflammatory and anti-inflammatory cytokines, and in cell survival, proliferation, and phagocytosis. TREM2 and TYROBP form a transmembrane complex in microglia that modulates intracellular signaling networks, and these proteins are essential regulators of the transition from homeostatic to activated microglia. Recent findings support a TREM2-independent molecular signature that is involved in the early transition of homeostatic to disease-associated microglia (DAM), with the next sequential step of DAM activation from stage 1 to stage 2 being TREM2-dependent. However, the underlying mechanisms determining how TREM2 or TYROBP regulate these downstream phenotypes are largely unknown. We isolated primary microglia from C57BL/6 wild-type (WT) controls, Trem2 knock-out (KO), and Tyrobp KO mice at post-natal day 0-3. Cells were treated with Alzheimer’s disease (AD)-relevant stimuli, such as amyloid beta (Aβ) oligomers or fibrils, or ‘neuroinflammatory-like’ stimuli, such as lipopolysaccharide (LPS). We explored protein and gene expression in the presence or absence of inhibitors of the TREM2/TYROBP downstream signaling pathway. We also performed a high-throughput Olink proteomic analysis of conditioned media from WT, Trem2 KO, and Tyrobp KO stimulated with either LPS or Aβ oligomers or fibrils. Our results show that the absence of either TREM2 or TYROBP is associated with increased basal levels of phosphorylated ERK in primary microglia compared to WT controls. In addition, Trem2 KO and Tyrobp KO cells show a less ramified cell morphology at baseline, as compared to WT microglia. Moreover, stimulating primary microglia with either Aβ oligomers or LPS leads to differential protein and gene expression in cells lacking TREM2 or TYROBP. The dysregulated downstream signal transduction and morphology in the absence of TREM2 or TYROBP suggest their essential roles not only in microglial homeostasis but also in their activation in response to different stimuli.
Project description:Polycystic lipomembranous osteodysplasia with sclerosing leukoencephalopathy (PLOSL) is an inherited brain and bone disease. It manifests as dementia and bone fractures. The PLOSL phenotype is caused by loss-of-function mutations in one of the two genes encoding the components of the DAP12/TREM2 receptor complex. The DAP12/TREM2 complex is expressed in cells of the myeloid lineage, including microglia in the central nervous system (CNS). The molecular mechanisms producing the CNS phenotype of PLOSL remain largely unknown. To gain insight into dysfunctional CNS pathways behind PLOSL, we performed genome-wide expression analysis of Dap12 (Tyrobp)-deficient mouse microglial cells. Keywords: knock-out response
Project description:We collected whole genome testis expression data from hybrid zone mice. We integrated GWAS mapping of testis expression traits and low testis weight to gain insight into the genetic basis of hybrid male sterility.