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15 Publications matching the given criteria: (Clear all filters)
Published year: 202115
Molecular diversity of diencephalic astrocytes reveals adult astrogenesis regulated by Smad4.

Abstract (Expand)

Astrocytes regulate brain-wide functions and also show region-specific differences, but little is known about how general and region-specific functions are aligned at the single-cell level. To explore … this, we isolated adult mouse diencephalic astrocytes by ACSA-2-mediated magnetic-activated cell sorting (MACS). Single-cell RNA-seq revealed 7 gene expression clusters of astrocytes, with 4 forming a supercluster. Within the supercluster, cells differed by gene expression related to ion homeostasis or metabolism, with the former sharing gene expression with other regions and the latter being restricted to specific regions. All clusters showed expression of proliferation-related genes, and proliferation of diencephalic astrocytes was confirmed by immunostaining. Clonal analysis demonstrated low level of astrogenesis in the adult diencephalon, but not in cerebral cortex grey matter. This led to the identification of Smad4 as a key regulator of diencephalic astrocyte in vivo proliferation and in vitro neurosphere formation. Thus, astrocytes show diverse gene expression states related to distinct functions with some subsets being more widespread while others are more regionally restricted. However, all share low-level proliferation revealing the novel concept of adult astrogenesis in the diencephalon.

Authors: Stefanie Ohlig, Solène Clavreul, Manja Thorwirth, Tatiana Simon-Ebert, Riccardo Bocchi, Sabine Ulbricht, Nirmal Kannayian, Moritz Rossner, Swetlana Sirko, Pawel Smialowski, Judith Fischer-Sternjak, Magdalena Götz

Date Published: 2nd Nov 2021

Publication Type: Journal

Proteomic and lipidomic profiling of demyelinating lesions identifies fatty acids as modulators in lesion recovery.

Abstract (Expand)

After demyelinating injury of the central nervous system, resolution of the mounting acute inflammation is crucial for the initiation of a regenerative response. Here, we aim to identify fatty acids … and lipid mediators that govern the balance of inflammatory reactions within demyelinating lesions. Using lipidomics, we identify bioactive lipids in the resolution phase of inflammation with markedly elevated levels of n-3 polyunsaturated fatty acids. Using fat-1 transgenic mice, which convert n-6 fatty acids to n-3 fatty acids, we find that reduction of the n-6/n-3 ratio decreases the phagocytic infiltrate. In addition, we observe accelerated decline of microglia/macrophages and enhanced generation of oligodendrocytes in aged mice when n-3 fatty acids are shuttled to the brain. Thus, n-3 fatty acids enhance lesion recovery and may, therefore, provide the basis for pro-regenerative medicines of demyelinating diseases in the central nervous system.

Authors: H. Penkert, A. Bertrand, V. Tiwari, S. Breimann, S. A. Muller, P. M. Jordan, M. J. Gerl, C. Klose, L. Cantuti-Castelvetri, M. Bosch-Queralt, I. Levental, S. F. Lichtenthaler, O. Werz, M. Simons

Date Published: 26th Oct 2021

Publication Type: Journal

The pseudoprotease iRhom1 controls ectodomain shedding of membrane proteins in the nervous system.

Abstract (Expand)

Proteolytic ectodomain shedding of membrane proteins is a fundamental mechanism to control the communication between cells and their environment. A key protease for membrane protein shedding is ADAM17, … which requires a non-proteolytic subunit, either inactive Rhomboid 1 (iRhom1) or iRhom2 for its activity. While iRhom1 and iRhom2 are co-expressed in most tissues and appear to have largely redundant functions, the brain is an organ with predominant expression of iRhom1. Yet, little is known about the spatio-temporal expression of iRhom1 in mammalian brain and about its function in controlling membrane protein shedding in the nervous system. Here, we demonstrate that iRhom1 is expressed in mouse brain from the prenatal stage to adulthood with a peak in early postnatal development. In the adult mouse brain iRhom1 was widely expressed, including in cortex, hippocampus, olfactory bulb, and cerebellum. Proteomic analysis of the secretome of primary neurons using the hiSPECS method and of cerebrospinal fluid, obtained from iRhom1-deficient and control mice, identified several membrane proteins that require iRhom1 for their shedding in vitro or in vivo. One of these proteins was 'multiple-EGF-like-domains protein 10' (MEGF10), a phagocytic receptor in the brain that is linked to the removal of amyloid beta and apoptotic neurons. MEGF10 was further validated as an ADAM17 substrate using ADAM17-deficient mouse embryonic fibroblasts. Taken together, this study discovers a role for iRhom1 in controlling membrane protein shedding in the mouse brain, establishes MEGF10 as an iRhom1-dependent ADAM17 substrate and demonstrates that iRhom1 is widely expressed in murine brain.

Authors: J. Tushaus, S. A. Muller, J. Shrouder, M. Arends, M. Simons, N. Plesnila, C. P. Blobel, S. F. Lichtenthaler

Date Published: 6th Oct 2021

Publication Type: Journal

Heterogeneity of neurons reprogrammed from spinal cord astrocytes by the proneural factors Ascl1 and Neurogenin2.

Abstract (Expand)

Astrocytes are a viable source for generating new neurons via direct conversion. However, little is known about the neurogenic cascades triggered in astrocytes from different regions of the CNS. Here, … we examine the transcriptome induced by the proneural factors Ascl1 and Neurog2 in spinal cord-derived astrocytes in vitro. Each factor initially elicits different neurogenic programs that later converge to a V2 interneuron-like state. Intriguingly, patch sequencing (patch-seq) shows no overall correlation between functional properties and the transcriptome of the heterogenous induced neurons, except for K-channels. For example, some neurons with fully mature electrophysiological properties still express astrocyte genes, thus calling for careful molecular and functional analysis. Comparing the transcriptomes of spinal cord- and cerebral-cortex-derived astrocytes reveals profound differences, including developmental patterning cues maintained in vitro. These relate to the distinct neuronal identity elicited by Ascl1 and Neurog2 reflecting their developmental functions in subtype specification of the respective CNS region.

Authors: J Kempf, K Knelles, B A Hersbach, D Petrik, T Riedemann, V Bednarova, A Janjic, T Simon-Ebert, W Enard, P Smialowski, M Götz, G Masserdotti

Date Published: 20th Jul 2021

Publication Type: Journal

Autophagosome content profiling using proximity biotinylation proteomics coupled to protease digestion in mammalian cells.

Abstract (Expand)

The ascorbate peroxidase APEX2 is commonly used to study the neighborhood of a protein of interest by proximity-dependent biotinylation. Here, we describe a protocol for sample processing compatible … with immunoblotting and mass spectrometry, suitable to specifically map the content of autophagosomes and potentially other short-lived endomembrane transport vesicles without the need of subcellular fractionation. By combining live-cell biotinylation with proteinase K digestion of cell homogenates, proteins enriched in membrane-protected compartments can be readily enriched and identified. For complete details on the use and execution of this protocol, please refer to Zellner et al. (2021).

Authors: S. Zellner, K. Nalbach, C. Behrends

Date Published: 18th Jun 2021

Publication Type: Journal

Skin and gut imprinted helper T cell subsets exhibit distinct functional phenotypes in central nervous system autoimmunity.

Abstract (Expand)

Multidimensional single-cell analyses of T cells have fueled the debate about whether there is extensive plasticity or 'mixed' priming of helper T cell subsets in vivo. Here, we developed an … experimental framework to probe the idea that the site of priming in the systemic immune compartment is a determinant of helper T cell-induced immunopathology in remote organs. By site-specific in vivo labeling of antigen-specific T cells in inguinal (i) or gut draining mesenteric (m) lymph nodes, we show that i-T cells and m-T cells isolated from the inflamed central nervous system (CNS) in a model of multiple sclerosis (MS) are distinct. i-T cells were Cxcr6(+), and m-T cells expressed P2rx7. Notably, m-T cells infiltrated white matter, while i-T cells were also recruited to gray matter. Therefore, we propose that the definition of helper T cell subsets by their site of priming may guide an advanced understanding of helper T cell biology in health and disease.

Authors: M. Hiltensperger, E. Beltran, R. Kant, S. Tyystjarvi, G. Lepennetier, H. Dominguez Moreno, I. J. Bauer, S. Grassmann, S. Jarosch, K. Schober, V. R. Buchholz, S. Kenet, C. Gasperi, R. Ollinger, R. Rad, A. Muschaweckh, C. Sie, L. Aly, B. Knier, G. Garg, A. M. Afzali, L. A. Gerdes, T. Kumpfel, S. Franzenburg, N. Kawakami, B. Hemmer, D. H. Busch, T. Misgeld, K. Dornmair, T. Korn

Date Published: 9th Jun 2021

Publication Type: Journal

ADAM10-Mediated Ectodomain Shedding Is an Essential Driver of Podocyte Damage.

Abstract (Expand)

BACKGROUND: Podocytes embrace the glomerular capillaries with foot processes, which are interconnected by a specialized adherens junction to ultimately form the filtration barrier. Altered adhesion and … loss are common features of podocyte injury, which could be mediated by shedding of cell-adhesion molecules through the regulated activity of cell surface-expressed proteases. A Disintegrin and Metalloproteinase 10 (ADAM10) is such a protease known to mediate ectodomain shedding of adhesion molecules, among others. Here we evaluate the involvement of ADAM10 in the process of antibody-induced podocyte injury. METHODS: Membrane proteomics, immunoblotting, high-resolution microscopy, and immunogold electron microscopy were used to analyze human and murine podocyte ADAM10 expression in health and kidney injury. The functionality of ADAM10 ectodomain shedding for podocyte development and injury was analyzed, in vitro and in vivo, in the anti-podocyte nephritis (APN) model in podocyte-specific, ADAM10-deficient mice. RESULTS: ADAM10 is selectively localized at foot processes of murine podocytes and its expression is dispensable for podocyte development. Podocyte ADAM10 expression is induced in the setting of antibody-mediated injury in humans and mice. Podocyte ADAM10 deficiency attenuates the clinical course of APN and preserves the morphologic integrity of podocytes, despite subepithelial immune-deposit formation. Functionally, ADAM10-related ectodomain shedding results in cleavage of the cell-adhesion proteins N- and P-cadherin, thus decreasing their injury-related surface levels. This favors podocyte loss and the activation of downstream signaling events through the Wnt signaling pathway in an ADAM10-dependent manner. CONCLUSIONS: ADAM10-mediated ectodomain shedding of injury-related cadherins drives podocyte injury.

Authors: M. Sachs, S. Wetzel, J. Reichelt, W. Sachs, L. Schebsdat, S. Zielinski, L. Seipold, L. Heintz, S. A. Muller, O. Kretz, M. Lindenmeyer, T. Wiech, T. B. Huber, R. Lullmann-Rauch, S. F. Lichtenthaler, P. Saftig, C. Meyer-Schwesinger

Date Published: 1st Jun 2021

Publication Type: Journal

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