Novel Hexb-based tools for studying microglia in the CNS

Masuda, Takahiro; Amann, Lukas; Sankowski, Roman; Staszewski, Ori; Lenz, Maximilian; ́Errico, Paolo d; Snaidero, Nicolas; Jordão, Marta Joana Costa; Böttcher, Chotima; Kierdorf, Katrin; Jung, Steffen; Priller, Josef; Misgeld, Thomas; Vlachos, Andreas; Meyer‐Luehmann, Melanie; Knobeloch, Klaus–Peter; Prinz, Marco

doi:10.1038/s41590-020-0707-4

Cited by 195 publications

(170 citation statements)

References 58 publications

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“…For example, microglia in an environment of amyloid induced neurodegeneration form a disease-associated microglia (DAM) (64), characterized by the downregulation of canonical microglial genes (P2ry12/13, Cx3cr1, Tmem119, Cst3) and upregulation of genes mapped to lipid metabolism pathways and phagocytosis (Apoe, Lpl, Cst7, Ctsd, Tyrobp, and Trem2). Certain genes, such as Hexb are stably expressed in homoeostatic microglia, DAM, and other neurological conditions (64,110). Elements of this DAM signature were later observed in microglia activated by diverse conditions such as following white matter injury (8,53), EAE (35), MS (78,82), amyloid lateral sclerosis (ALS) (64,111), ageing (53,111), facial nerve injury (112) and cancer (81).…”

Section: Microglia Heterogeneity During Eaementioning

confidence: 99%

“…Due to difficulties distinguishing microglia from monocyte-derived macrophages within the lesion, no studies to date have been able to assign intralesional functional differences between these two cell populations with ageing. The advent of phenotypic markers and genetic fate-mapping strategies to distinguish these two populations opens up a promising new avenue of inquiry ( 110 , 154 , 155 ). Circumstantially, it has been documented that the ageing process manifests differently in microglia compared to monocyte-derived macrophages.…”

Section: Age-associated Remyelination Decline Involves Impaired Micromentioning

confidence: 99%

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Microglia Diversity in Health and Multiple Sclerosis

et al. 2020

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Multiple Sclerosis (MS) is a neurodegenerative disease characterized by multiple focal lesions, ongoing demyelination and, for most people, a lack of remyelination. MS lesions are enriched with monocyte-derived macrophages and brain-resident microglia that, together, are likely responsible for much of the immune-mediated neurotoxicity. However, microglia and macrophage also have documented neuroprotective and regenerative roles, suggesting a potential diversity in their functions. Linked with microglial functional diversity, they take on diverse phenotypes developmentally, regionally and across disease conditions. Advances in technologies such as single-cell RNA sequencing and mass cytometry of immune cells has led to dramatic developments in understanding the phenotypic changes of microglia and macrophages. This review highlights the origins of microglia, their heterogeneity throughout normal ageing and their contribution to pathology and repair, with a specific focus on autoimmunity and MS. As phenotype dictates function, the emerging heterogeneity of microglia and macrophage populations in MS offers new insights into the potential immune mechanisms that result in inflammation and regeneration.

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Section: Microglia Heterogeneity During Eaementioning

confidence: 99%

Section: Age-associated Remyelination Decline Involves Impaired Micromentioning

confidence: 99%

Microglia Diversity in Health and Multiple Sclerosis

et al. 2020

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“…To target microglia, Ruan et al (41) inserted a tdTomato reporter with a cleavable peptide linker between the coding sequence and 3'UTR of the Tmem119 locus. Masuda et al (42) inserted the same reporter into the Hexb locus. Here we took a similar approach and inserted a Fusion-Red (FRed) cassette with cleavable linker in-frame into the 3' end of the mouse Csf1r locus.…”

Section: Introductionmentioning

confidence: 99%

A transgenic line that reports CSF1R protein expression provides a definitive marker for the mouse mononuclear phagocyte system

Grabert

Sehgal

Irvine

et al. 2020

Preprint

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The proliferation, differentiation and survival of cells of the mononuclear phagocyte system (MPS, progenitors, monocytes, macrophages and classical dendritic cells) is controlled by signals from the macrophage colony-stimulating factor receptor (CSF1R). Cells of the MPS lineage have been identified using numerous surface markers and transgenic reporters but none is both universal and lineage-restricted. Here we report the development and characterization of a novel CSF1R reporter mouse. A Fusion Red (FRed) cassette was inserted in-frame with the C-terminus of CSF1R, separated by a T2A-cleavable linker. The insertion had no effect of CSF1R expression or function. CSF1R-FRed was expressed in monocytes and macrophages and absent from granulocytes and lymphocytes. In bone marrow, CSF1R-FRed was absent in lineage-negative hematopoietic stem cells (HSC), arguing against a direct role for CSF1R in myeloid lineage commitment. It was highly-expressed in marrow monocytes and common myeloid progenitors (CMP) but significantly lower in granulocyte-macrophage progenitors (GMP). In sections of bone marrow, CSF1R-FRed was also detected in osteoclasts, CD169+ resident macrophages and, consistent with previous mRNA analysis, in megakaryocytes. In lymphoid tissues, CSF1R-FRed highlighted diverse MPS populations including classical dendritic cells. Whole mount imaging of non-lymphoid tissues in mice with combined CSF1R-FRed/Csf1r-EGFP confirmed the restriction of CSF1R expression to MPS cells. The two markers highlight the remarkable abundance and regular distribution of tissue MPS cells including novel macrophage populations within tendon and skeletal muscle and underlying the mesothelial/serosal/capsular surfaces of every major organ. The CSF1R-FRed mouse provides a novel reporter with exquisite specificity for cells of the MPS.

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“…Also, we confirmed the specific expression of ReaChR in Iba1 + microglia after TM injection in the CNS. To circumvent these issues of CX3CR1 CreER mice, future studies should use the newly available microglia specific cre lines including TMEM119 CreER 47 and Hexb CreER mice 48 .…”

Section: Discussionmentioning

confidence: 99%

Optogenetic activation of spinal microglia triggers chronic pain in mice

Liu

Umpierre

et al. 2020

Preprint

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Spinal microglia are highly responsive to peripheral nerve injury and are known to be a key player in neuropathic pain. However, there has not been any direct evidence showing selective microglial activation in vivo is sufficient to induce chronic pain. Here we used optogenetic approaches in microglia to address this question employing CX3CR1creER/+: R26LSL-ReaChR/+ transgenic mice, in which red-activated channelrhodopsin (ReaChR) is inducibly and specifically expressed in microglia. We found that activation of ReaChR by red light in spinal microglia evoked reliable inward currents and membrane depolarization. In vivo optogenetic activation of microglial ReaChR in the spinal cord triggered chronic pain hypersensitivity lasting for 5-7 days. In addition, activation of microglial ReaChR upregulated neuronal c-fos expression and enhanced C-fiber responses. Mechanistically, ReaChR activation led to a reactive microglial phenotype with increased IL-1β production. IL-1 receptor antagonist was able to reverse the pain hypersensitivity and neuronal hyperactivity induced by microglial ReaChR activation. Therefore, our work demonstrates that optogenetic activation of spinal microglia is sufficient to trigger chronic pain phenotypes by increasing neuronal activity via IL-1 signaling.

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Novel Hexb-based tools for studying microglia in the CNS

Cited by 195 publications

References 58 publications

Microglia Diversity in Health and Multiple Sclerosis

Microglia Diversity in Health and Multiple Sclerosis

A transgenic line that reports CSF1R protein expression provides a definitive marker for the mouse mononuclear phagocyte system

Optogenetic activation of spinal microglia triggers chronic pain in mice

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