Publications

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6 Publications visible to you, out of a total of 6

Abstract (Expand)

Oligodendrocytes extend numerous cellular processes that wrap multiple times around axons to generate lipid-rich myelin sheaths. Myelin biogenesis requires an enormously productive biosynthetic machinery for generating and delivering these large amounts of newly synthesized lipids. Yet, a complete understanding of this process remains elusive. Utilizing volume electron microscopy, we demonstrate that the oligodendroglial endoplasmic reticulum (ER) is enriched in developing myelin, extending into and making contact with the innermost myelin layer where growth occurs. We explore the possibility of transfer of lipids from the ER to myelin, and find that the glycolipid transfer protein (GLTP), implicated in nonvesicular lipid transport, is highly enriched in the growing myelin sheath. Mice with a specific knockout of Gltp in oligodendrocytes exhibit ER pathology, hypomyelination and a decrease in myelin glycolipid content. In summary, our results demonstrate a role for nonvesicular lipid transport in CNS myelin growth, revealing a cellular pathway in developmental myelination.

Authors: Jianping Wu, Georg Kislinger, Jerome Duschek, Ayşe Damla Durmaz, Benedikt Wefers, Ruoqing Feng, Karsten Nalbach, Wolfgang Wurst, Christian Behrends, Martina Schifferer, Mikael Simons

Date Published: 11th Nov 2024

Publication Type: Journal

Abstract (Expand)

Loss-of-function mutations in the homotrimeric serine protease HTRA1 cause cerebral vasculopathy. Here, we establish independent approaches to achieve the functional correction of trimer assembly defects. Focusing on the prototypical R274Q mutation, we identify an HTRA1 variant that promotes trimer formation thus restoring enzymatic activity in vitro. Genetic experiments in Htra1<sup>R274Q</sup> mice further demonstrate that expression of this protein-based corrector in trans is sufficient to stabilize HtrA1-R274Q and restore the proteomic signature of the brain vasculature. An alternative approach employs supramolecular chemical ligands that shift the monomer-trimer equilibrium towards proteolytically active trimers. Moreover, we identify a peptidic ligand that activates HTRA1 monomers. Our findings open perspectives for tailored protein repair strategies.

Authors: Nathalie Beaufort, Linda Ingendahl, Melisa Merdanovic, Andree Schmidt, David Podlesainski, Tim Richter, Thorben Neumann, Michael Kuszner, Ingrid R Vetter, Patricia Stege, Steven G Burston, Anto Filipovic, Yasser B Ruiz-Blanco, Kenny Bravo-Rodriguez, Joel Mieres-Perez, Christine Beuck, Stephan Uebel, Monika Zobawa, Jasmin Schillinger, Rainer Malik, Katalin Todorov-Völgyi, Juliana Rey, Annabell Roberti, Birte Hagemeier, Benedikt Wefers, Stephan A Müller, Wolfgang Wurst, Elsa Sanchez-Garcia, Alexander Zimmermann, Xiao-Yu Hu, Tim Clausen, Robert Huber, Stefan F Lichtenthaler, Carsten Schmuck, Michael Giese, Markus Kaiser, Michael Ehrmann, Martin Dichgans

Date Published: 16th Jul 2024

Publication Type: Journal

Abstract (Expand)

Direct reprogramming based on genetic factors resembles a promising strategy to replace lost cells in degenerative diseases such as Parkinson's disease. For this, we developed a knock-in mouse line carrying a dual dCas9 transactivator system (dCAM) allowing the conditional in vivo activation of endogenous genes. To enable a translational application, we additionally established an AAV-based strategy carrying intein-split-dCas9 in combination with activators (AAV-dCAS). Both approaches were successful in reprogramming striatal astrocytes into induced GABAergic neurons confirmed by single-cell transcriptome analysis of reprogrammed neurons in vivo. These GABAergic neurons functionally integrate into striatal circuits, alleviating voluntary motor behavior aspects in a 6-OHDA Parkinson's disease model. Our results suggest a novel intervention strategy beyond the restoration of dopamine levels. Thus, the AAV-dCAS approach might enable an alternative route for clinical therapies of Parkinson's disease.

Authors: Jessica Giehrl-Schwab, Florian Giesert, Benedict Rauser, Chu Lan Lao, Sina Hembach, Sandrine Lefort, Ignacio L Ibarra, Christina Koupourtidou, Malte Daniel Luecken, Dong-Jiunn Jeffery Truong, Judith Fischer-Sternjak, Giacomo Masserdotti, Nilima Prakash, Jovica Ninkovic, Sabine M Hölter, Daniela M Vogt Weisenhorn, Fabian J Theis, Magdalena Götz, Wolfgang Wurst

Date Published: 9th May 2022

Publication Type: Journal

Abstract (Expand)

The oligodendrocyte progenitors (OPCs) are at the front of the glial reaction to the traumatic brain injury. However, regulatory pathways steering the OPC reaction as well as the role of reactive OPCs remain largely unknown. Here, we compared a long-lasting, exacerbated reaction of OPCs to the adult zebrafish brain injury with a timely restricted OPC activation to identify the specific molecular mechanisms regulating OPC reactivity and their contribution to regeneration. We demonstrated that the influx of the cerebrospinal fluid into the brain parenchyma after injury simultaneously activates the toll-like receptor 2 (Tlr2) and the chemokine receptor 3 (Cxcr3) innate immunity pathways, leading to increased OPC proliferation and thereby exacerbated glial reactivity. These pathways were critical for long-lasting OPC accumulation even after the ablation of microglia and infiltrating monocytes. Importantly, interference with the Tlr1/2 and Cxcr3 pathways after injury alleviated reactive gliosis, increased new neuron recruitment, and improved tissue restoration.

Authors: Rosario Sanchez-Gonzalez, Christina Koupourtidou, Tjasa Lepko, Alessandro Zambusi, Klara Tereza Novoselc, Tamara Durovic, Sven Aschenbroich, Veronika Schwarz, Christopher T Breunig, Hans Straka, Hagen B Huttner, Martin Irmler, Johannes Beckers, Wolfgang Wurst, Andreas Zwergal, Tamas Schauer, Tobias Straub, Tim Czopka, Dietrich Trümbach, Magdalena Götz, Stefan H Stricker, Jovica Ninkovic

Date Published: 2nd Feb 2022

Publication Type: Journal

Abstract (Expand)

Astrocyte-to-neuron conversion is a promising avenue for neuronal replacement therapy. Neurons are particularly dependent on mitochondrial function, but how well mitochondria adapt to the new fate is unknown. Here, we determined the comprehensive mitochondrial proteome of cortical astrocytes and neurons, identifying about 150 significantly enriched mitochondrial proteins for each cell type, including transporters, metabolic enzymes, and cell-type-specific antioxidants. Monitoring their transition during reprogramming revealed late and only partial adaptation to the neuronal identity. Early dCas9-mediated activation of genes encoding mitochondrial proteins significantly improved conversion efficiency, particularly for neuron-enriched but not astrocyte-enriched antioxidant proteins. For example, Sod1 not only improves the survival of the converted neurons but also elicits a faster conversion pace, indicating that mitochondrial proteins act as enablers and drivers in this process. Transcriptional engineering of mitochondrial proteins with other functions improved reprogramming as well, demonstrating a broader role of mitochondrial proteins during fate conversion.

Authors: Gianluca L Russo, Giovanna Sonsalla, Poornemaa Natarajan, Christopher T Breunig, Giorgia Bulli, Juliane Merl-Pham, Sabine Schmitt, Jessica Giehrl-Schwab, Florian Giesert, Martin Jastroch, Hans Zischka, Wolfgang Wurst, Stefan H Stricker, Stefanie M Hauck, Giacomo Masserdotti, Magdalena Götz

Date Published: 4th Mar 2021

Publication Type: Journal

Abstract (Expand)

Mitochondria vary in morphology and function in different tissues; however, little is known about their molecular diversity among cell types. Here we engineered MitoTag mice, which express a Cre recombinase-dependent green fluorescent protein targeted to the outer mitochondrial membrane, and developed an isolation approach to profile tagged mitochondria from defined cell types. We determined the mitochondrial proteome of the three major cerebellar cell types (Purkinje cells, granule cells and astrocytes) and identified hundreds of mitochondrial proteins that are differentially regulated. Thus, we provide markers of cell-type-specific mitochondria for the healthy and diseased mouse and human central nervous systems, including in amyotrophic lateral sclerosis and Alzheimer's disease. Based on proteomic predictions, we demonstrate that astrocytic mitochondria metabolize long-chain fatty acids more efficiently than neuronal mitochondria. We also characterize cell-type differences in mitochondrial calcium buffering via the mitochondrial calcium uniporter (Mcu) and identify regulator of microtubule dynamics protein 3 (Rmdn3) as a determinant of endoplasmic reticulum-mitochondria proximity in Purkinje cells. Our approach enables exploring mitochondrial diversity in many in vivo contexts.

Authors: C. Fecher, L. Trovo, S. A. Muller, N. Snaidero, J. Wettmarshausen, S. Heink, O. Ortiz, I. Wagner, R. Kuhn, J. Hartmann, R. M. Karl, A. Konnerth, T. Korn, W. Wurst, D. Merkler, S. F. Lichtenthaler, F. Perocchi, T. Misgeld

Date Published: 11th Sep 2019

Publication Type: Journal

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