TY - JOUR A1 - Lüningschrör, Patrick A1 - Slotta, Carsten A1 - Heimann, Peter A1 - Briese, Michael A1 - Weikert, Ulrich M. A1 - Massih, Bita A1 - Appenzeller, Silke A1 - Sendtner, Michael A1 - Kaltschmidt, Christian A1 - Kaltschmidt, Barbara T1 - Absence of Plekhg5 Results in Myelin Infoldings Corresponding to an Impaired Schwann Cell Autophagy, and a Reduced T-Cell Infiltration Into Peripheral Nerves JF - Frontiers in Cellular Neuroscience N2 - Inflammation and dysregulation of the immune system are hallmarks of several neurodegenerative diseases. An activated immune response is considered to be the cause of myelin breakdown in demyelinating disorders. In the peripheral nervous system (PNS), myelin can be degraded in an autophagy-dependent manner directly by Schwann cells or by macrophages, which are modulated by T-lymphocytes. Here, we show that the NF-κB activator Pleckstrin homology containing family member 5 (Plekhg5) is involved in the regulation of both Schwann cell autophagy and recruitment of T-lymphocytes in peripheral nerves during motoneuron disease. Plekhg5-deficient mice show defective axon/Schwann cell units characterized by myelin infoldings in peripheral nerves. Even at late stages, Plekhg5-deficient mice do not show any signs of demyelination and inflammation. Using RNAseq, we identified a transcriptional signature for an impaired immune response in sciatic nerves, which manifested in a reduced number of CD4\(^+\) and CD8\(^+\) T-cells. These findings identify Plekhg5 as a promising target to impede myelin breakdown in demyelinating PNS disorders. KW - Schwann cells KW - autophagy KW - immune response KW - myelin KW - PLEKHG5 Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-207538 SN - 1662-5102 VL - 14 ER - TY - JOUR A1 - Thangaraj Selvaraj, Bhuvaneish A1 - Frank, Nicolas A1 - Bender, Florian L. P. A1 - Asan, Esther A1 - Sendtner, Michael T1 - Local axonal function of STAT3 rescues axon degeneration in the pmn model of motoneuron disease JF - The Journal of Cell Biology N2 - Axonal maintenance, plasticity, and regeneration are influenced by signals from neighboring cells, in particular Schwann cells of the peripheral nervous system. Schwann cells produce neurotrophic factors, but the mechanisms by which ciliary neurotrophic factor (CNTF) and other neurotrophic molecules modify the axonal cytoskeleton are not well understood. In this paper, we show that activated signal transducer and activator of transcription-3 (STAT3), an intracellular mediator of the effects of CNTF and other neurotrophic cytokines, acts locally in axons of motoneurons to modify the tubulin cytoskeleton. Specifically, we show that activated STAT3 interacted with stathmin and inhibited its microtubule-destabilizing activity. Thus, ectopic CNTF-mediated activation of STAT3 restored axon elongation and maintenance in motoneurons from progressive motor neuronopathy mutant mice, a mouse model of motoneuron disease. This mechanism could also be relevant for other neurodegenerative diseases and provide a target for new therapies for axonal degeneration. KW - Schwann cells KW - transcription-3 (STAT3) KW - ciliary neurotrophic factor (CNTF) KW - axonal degeneration Y1 - 2012 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-154675 VL - 199 IS - 3 SP - 437 EP - 451 ER - TY - THES A1 - Kohl, Bianca Dorothea T1 - PMP22-overexpressing mice as a model for Charcot-Marie-Tooth 1A neuropathy implicate a role of immune-related cells T1 - PMP22-überexprimierende Mäuse als Modell einer Charcot-Marie-Tooth 1A Neuropatie. N2 - Charcot-Marie-Tooth disease (CMT) is a cohort of human hereditary disorders of the peripheral nervous system (PNS) which exhibit symptoms like sensory dysfunction, muscle weakness and gait disturbances. Different mutations are described as causation for this neuropathy, such as a duplication of chromosome 17 comprising the gene for the peripheral myelin protein-22 (PMP22). Based on different animal models former studies identified immune cells, i.e. macrophages and T-lymphocytes, as crucial mediators of pathology in these neuropathies. In this study, PMP22-overexpressing mice (PMP22tg, C61), serving as a model for a specific type of CMT – CMT1A – were crossbred with immune-deficient mutant mice to examine the impact of the immune system on nerve pathology. Crossbreeding of PMP22tg mice with recombination activating gene-1 (RAG-1) deficient mice, lacking mature T- and B-lymphocytes, caused no striking alterations of pathogenesis in peripheral nerves of mutant mice. In contrast, crossbreeding of PMP22tg myelin mutants with mice deficient in the chemokine monocyte chemoattractant protein-1 (MCP-1, CCL2) caused an amelioration of the demyelinating phenotype of peripheral nerves when MCP-1 was either reduced or completely absent. Furthermore, functional investigations, i.e. neurographic recordings and examinations of the grip strength of the extremities, revealed an amelioration in PMP22tg/MCP-1-/- mice in regard to a symptomatic improvement in the compound action muscle potential (CMAP) and stronger grip strength of the hindlimbs. Interestingly, peripheral nerves of PMP22tg mice showed an irregular distribution of potassium channels in presence of MCP-1, whereas the absence of MCP-1 in the myelin mutants rescued the ion channel distribution and resulted in a more wild type-like phenotype. Having shown the impact of MCP-1 as an important mediator of nerve pathology in PMP22/MCP-1 double mutants, the regulation of this chemokine became an important target for potential treatment strategies. We found that the signaling cascade MEK1/2/ERK1/2 was more strongly activated in peripheral nerves of PMP22tg mice compared to nerves of wild type mice. This activation corresponded to an increase in MCP-1 mRNA expression in peripheral nerves at the same age. Furthermore, a MEK1/2-inhibitor was used in vivo to confirm the regulation of MCP-1 by the MEK1/2/ERK1/2 pathway. After a treatment period of three weeks, a clear reduction of ERK1/2-phosphorylation as well as a reduction of MCP-1 mRNA expression was observed, accompanied by a decline in macrophage number in peripheral nerves of PMP22tg mice. These observations suggest that the expression of MCP-1 is crucial for the neuropathological progression in a mouse model for CMT1A. Therefore, this chemokine could provide a basis for a putative treatment strategy of inherited neuropathies. N2 - Die Charcot-Marie-Tooth Erkrankungen (CMT) sind eine Gruppe von humanen, erblichen Erkrankungen des peripheren Nervensystems (PNS), welche Symptome wie sensible Störungen, Muskelschwäche und Gangstörungen verursachen können. Verschiedene Mutationen, z.B. eine Duplikation des Chromosoms 17, welches das Gen für das periphere Myelinprotein-22 (PMP22) enthält, sind als Ursache für diese Neuropathie beschrieben. Anhand verschiedener Tiermodelle wurde in früheren Studien gezeigt, dass Immunzellen, insbesondere Makrophagen und T-Lymphozyten, maßgeblich an der Pathogenese dieser Neuropathien beteiligt sind. In der vorliegenden Studie wurden PMP22-überexprimierende Mäuse (PMP22tg, C61) als Modell einer spezifischen CMT-Form – CMT1A – mit immun-defizienten Mutanten verkreuzt, um die modulierende Rolle des Immunsystems innerhalb der Pathogenese peripherer Nerven untersuchen zu können. Die Verkreuzung von PMP22tg Mäusen mit „recombination activating gene-1“-defizienten Mutanten (RAG-1-/-), die keine reifen T- und B-Lymphozyten besitzen, resultierte in keiner deutlich veränderten Pathologie der peripheren Nerven. Im Gegensatz hierzu führte die Verkreuzung der Myelinmutanten mit Mäusen, defizient für das Chemokin „monocyte chemoattractant protein-1“ (MCP-1), zu einer Abschwächung des demyelinisierenden Phänotyps in peripheren Nerven, wenn MCP-1 reduziert war oder völlig fehlte. Funktionelle Analysen, wie elektrophysiologische Messungen und Untersuchungen der Kraft in den Extremitäten, zeigten zudem in PMP22tg/MCP-1-/- Mäusen eine symptomatische Verbesserung, was sich in einer höheren Amplitude (compound muscle action potential, CMAP) und einer erhöhten Kraft in den Hinterpfoten der Mäuse widerspiegelte. Interessanterweise zeigten periphere Nerven der PMP22tg Mäuse eine abnorme Verteilung von Kalium-Kanälen, wohingegen das Fehlen von MCP-1 in den Myelinmutanten zu einer Verteilung dieser Ionenkanäle führte, die ähnlich zu Wildtyp-Mäusen war. Da MCP-1 in den PMP22/MCP-1 Doppelmutanten einen deutlichen Einfluss auf die Pathogenese aufwies, wurde die Regulation dieses Chemokins im Hinblick auf mögliche Therapie-Ansätze untersucht. Diese Untersuchung zeigte, dass die MEK1/2/ERK1/2-Signalkaskade in peripheren Nerven von PMP22tg Mäusen stärker aktiviert wird als in Nerven von Wildtyp-Tieren. Die Aktivierung dieser Signalkaskade ging dabei mit einer erhöhten MCP-1 mRNA Expression in peripheren Nerven von Tieren des gleichen Alters einher. Ergänzend wurde ein MEK1/2-Inhibitor in vivo verwendet, um die Regulation von MCP-1 durch die MEK1/2/ERK1/2 Kaskade zu bestätigen. Nach einer Behandlungszeit von drei Wochen wurde eine deutliche Reduktion der ERK1/2-Phosphorylierung, sowie eine Reduktion der MCP-1 mRNA Expression und eine geringere Makrophagen-Anzahl in peripheren Nerven von PMP22tg Mäusen detektiert. Diese Untersuchungen zeigen, dass die Expression von MCP-1 entscheidend für den neuropathologischen Verlauf in einem Mausmodell für CMT1A ist. Somit bietet dieses Chemokin eine Basis für die Entwicklung neuer Behandlungsstrategien peripherer Neuropathien. KW - Myelin KW - Makrophage KW - Entmarkung KW - Schwann Zellen KW - PMP22 KW - MCP-1 KW - Immunzellen KW - Periphere Nerven KW - Schwann cells KW - PMP22 KW - MCP-1 KW - immune cells KW - peripheral nerves Y1 - 2009 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-43066 ER -