Biology subjects

Misgeld, T.

Publications and source records attributed to Misgeld, T..

At least 19 recordsLinked to original sources

bioRxiv2026

Early demyelination by off-target complement injury in a mouse model of neuromyelitis optica

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune CNS disease characterized by serum antibodies targeting astrocytes for complement-mediated lysis. NMOSD lesions show not only astrocyte loss but also early demyelination and oligodendrocyte injury - histological hallmarks that converge with those of other primary demyelinating conditions. How pathology spreads to cause demyelination, particularly in early lesions, remains unclear. Using spinal cord imaging in an acute mouse NMOSD model, we directly observe the spread of pathology from astrocytes to oligodendrocytes in evolving lesions. This spread is characterized by initial calcium dyshomeostasis in oligodendrocytes followed by delayed, non-lytic cell death. Oligodendrocyte death is driven not by astrocyte loss per se but by spill-over of soluble complement proteins, as oligodendrocytes can be cell-autonomously preserved by the cell-type-specific expression of the complement inhibitor CD59. Our findings explain the convergence of glial pathology in antibody-mediated CNS autoimmunity and point towards new approaches to prevent secondary glial injury.

neuroscience↗

bioRxiv2026

Selective Cortical Myelination Reflects Axon-Driven Progression of the BCAS1-positive Oligodendrocyte Lineage

Myelination in the cerebral cortex is sparse, discontinuous, showing marked heterogeneity across cortical areas and along individual axons, yet the mechanisms that establish this complex and selective architecture remain unclear. Using histological mapping of oligodendrocyte lineage cells across cortical areas combined with longitudinal in vivo imaging, we find that initial myelination is highly targeted: up to 80 percent of the earliest segments arise consecutively along the same subset of axons. We observed that oligodendrocyte precursor cells enter a premyelinating BCAS1-positive state even within cortical regions that remain poorly myelinated or unmyelinated. However, the progression beyond early premyelinating morphologies correlates with local myelin levels and with interactions with specific neuronal partners. BCAS1-positive ensheathments show a preferential stabilisation and elongation along parvalbumin interneurons compared with somatostatin interneurons, linking regional neuronal composition to differential myelin levels. These findings indicate that cortical myelination emerges from intrinsic lineage programs that are refined through selective interactions with axons, thereby linking neuronal diversity to cortical myelin distribution and providing a framework to understand why remyelination may fail in regions where myelination supportive neuronal populations are reduced.

neuroscience↗

bioRxiv2026

Local demyelination rekindles oligodendrocyte precursor dynamics and remyelination in old age

Cortical myelination is critical for circuit function, plasticity, and long-term stability in the adult brain. With age and disease, the capacity to restore myelin after oligodendrocyte (OL) loss declines, and this failure is thought to reflect intrinsic limitations of OL precursor cells (OPCs) and a loss of permissive cues within the cortical environment. Here, using single-OL ablations and intravital imaging in mice, we show that as cortical remyelination efficiency declines, OPC motility declines, a phenomenon that can be mimicked by blocking CXCL12/CXCR4 signaling. Counter to prevailing notions, however, we find that even in aging, OPCs retain the capacity to generate new OLs and sheath axons, which can be rekindled by a graded demyelinating stimulus, inducing a more juvenile OPC motile state. This reveals an unrecognized remyelination potential in aging and identifies OPC dynamics as a key determinant of cortical remyelination, a property that could be targeted to improve myelin repair.

neuroscience↗

bioRxiv2026

A reproducible human brain tissue model to study physiological and disease-associated microglia phenotypes

Stem-cell-based in vitro models offer promising potential to elucidate human brain cell functions and interactions under physiological and pathological conditions. However, harnessing this potential is impaired by low reproducibility, maturity, or cell-type diversity of existing models. Especially, prolonged incorporation of mature microglia and studies of neuroinflammation have proven challenging. Here, we developed a 3D cortical brain tissue model (3BTM) containing neurons, astrocytes, and microglia with high reproducibility, maturity, and viability. 3BTMs show morphological, functional, and proteomic maturation of all cell types, leading to high similarity to their in vivo counterparts. Incorporated microglia survive for over 6 months and display mature morphology, functions, and gene expression. Importantly, when engineered to model Alzheimers disease pathology, 3BTMs recapitulate key disease hallmarks including amyloid deposition, increased phospho-Tau levels, and neuroinflammation, with microglia shifting their transcriptional landscape to disease-relevant signatures. Together, our model offers unprecedented possibilities for studying physiological and pathological states of human brain tissue and translational applications.

neuroscience↗

bioRxiv2026

Mitochondrial hitch-hiking of Mapt mRNA maintains Tau levels in axons

Hitch-hiking of transcripts on organelles, including mitochondria, has emerged as a common pathway to transport mRNAs into the axon to enable their local translation. However, the extent of mitochondrial mRNA association in vivo has not been established. Here we report the landscape of mitochondrial mRNA association in two nerve tissues, the retinal ganglion cell derived optic nerve and the motor neuron derived part of the sciatic nerve. This revealed astonishing tissue diversity between mitochondria associated mRNAs that can partly be explained by the lack of expression of the mitochondrially anchored RNA-binding protein SYNJ2a in motor neurons. This diversity led us to discover that also MAPT mRNA, encoding the axon-enriched microtubule associated protein Tau, is transported via the mitochondrial RNA anchoring complex SYNJ2a/SYNJ2BP into axons of glutamatergic neurons. Loss of SYNJ2BP prevents axonal localization of MAPT and miss-sorting of Tau, consequently stunting axonal growth in cultured hippocampal neurons. This connects mitochondrial transport to the maintenance of the local cytoskeleton and axonal growth in glutamatergic neurons.

neuroscience↗

bioRxiv2025

Neuronal compartmentalization results in impoverished axonal mitochondria

Mitochondria differ depending on their location within a neuron. Morphological heterogeneity between somatic, dendritic, and axonal mitochondria is well established. Emerging evidence suggests that further specialization is needed to meet the unique demands of different neuronal compartments. However, the molecular and functional diversity of mitochondria within a neuron remains poorly understood. Here, we utilized proteomics in MitoTag mice to profile somatodendritic and axonal mitochondria across four distinct neuron types, thereby generating a compendium of intracellular mitochondrial diversity. Combining proteomics, functional, and immunofluorescence analyses, we demonstrated that axonal mitochondria are not defined by the presence of unique proteins, but rather by the selective loss or preservation of specific pathways compared to their somatodendritic counterparts. This results in "impoverished" axonal mitochondria, which are characterized by diminished mtDNA expression and impaired oxidative phosphorylation yet retain other pathways, such as fatty acid metabolism. Bioinformatic analyses of multiomic data identified local translation as one mechanism underlying compartment-specific diversity. Together, these findings provide a comprehensive in vivo framework for understanding mitochondrial specialization across neuronal compartments.

neuroscience↗

bioRxiv2024

Axon-specific microtubule regulation drives asymmetric regeneration of sensory neuron axons

Sensory dorsal root ganglion (DRG) neurons have a unique pseudo-unipolar morphology in which a stem axon bifurcates into a peripheral and a central axon, with different regenerative abilities. Whereas peripheral DRG axons regenerate, central axons are unable to regrow. Central axon regeneration can however be elicited by a prior conditioning lesion to the peripheral axon. How DRG axon asymmetry is established, remains unknown. Here we developed a rodent in vitro system replicating DRG pseudo-unipolarization and asymmetric axon regeneration. Using this model, we observed that from early development, central DRG axons have a higher density of growing microtubules. This asymmetry was also present in vivo and was abolished by a conditioning lesion that decreased microtubule polymerization of central DRG axons. An axon-specific microtubule-associated protein (MAP) signature, including the severases spastin and katanin and the microtubule regulators CRMP5 and tau, was found and shown to adapt upon conditioning lesion. Supporting its significance, interfering with the DRG MAP signature either in vitro or in vivo, readily abolished central-peripheral asymmetries in microtubule dynamics and regenerative ability. In summary, our data unveil that axon-specific microtubule regulation drives asymmetric regeneration of sensory neuron axons. Impact statementSensory neurons have a stem axon that bifurcates originating two axons with different properties. This work shows that DRG axons have a specific protein signature underlying microtubule and regeneration asymmetries. It also provides an in vitro system replicating DRG biology.

neuroscience↗

bioRxiv2024

A retrograde transit filter mediated by optineurin controls mitostasis in distal axons

The mechanisms of mitochondrial homeostasis in neurons-- mitostasis--are enigmatic and disease-prone, given a neurons large synaptic pool of mitochondria. To better understand mitostasis in mature mouse motor axons, we used ex vivo optical pulse-chase measurements of mitochondrial volume flux and identified a reiterative degradation system near presynaptic terminals and distal paranodes, which accounts for 75% of mitochondrial turnover in synapses. This distal filter system captures dysfunctional mitochondria from the retrograde stream and redirects them for lysosomal degradation. It depends on optineurin, a motor neuron disease-related mitophagy adaptor, but not on PINK1 and parkin, implicating a non-canonical mitophagy pathway. In presymptomatic motor neuron disease models, where retrograde transport is disrupted, the fraction of removed mitochondria is increased. Thus, we identify a new mitostasis system in distal axons with a cascade of checkpoints for local mitophagy, which normally maintains mitochondrial mass balance but is disrupted early in degenerative axonopathies.

cell biology↗

bioRxiv2024

ER-associated biogenesis of PINK1 preprotein for neuronal mitophagy

A central role in mitochondrial quality control is played by the Parkinson-related mitochondrial kinase PINK1, whose mRNA is transported in neurons by mitochondrial hitch- hiking. Using a live-cell imaging assay for the translation of the PINK1 precursor, we show that local translation of PINK1 requires a concerted interplay between mitochondria and the ER in neurons. For efficient translation, the Pink1 mRNA needs to relocate to ribosomes located near endolysosomes and the ER. The ER membrane-tethered chaperone DNAJB6 then shields the PINK1 precursor on transit to mitochondria following the ER-SURF pathway. Loss of DNAJB6 hence leads to persistence of ER/endolysosome-associated PINK1 precursor stores and failure of mitophagy upon mitochondrial damage.

neuroscience↗

bioRxiv2024

Astrocytes adopt a progenitor-like migratory strategy for regeneration in adult brain

Mature astrocytes become activated upon non-specific tissue damage and contribute to glial scar formation. Proliferation and migration of adult reactive astrocytes after injury is considered very limited. However, the regenerative behavior of individual astrocytes following selective astroglial loss, as seen in astrocytopathies, such as neuromyelitis optica spectrum disorder, remains unexplored. Here, we performed longitudinal in vivo imaging of cortical astrocytes after focal astrocyte ablation in mice. We discovered that perilesional astrocytes develop a remarkable plasticity for efficient lesion repopulation. A subset of mature astrocytes transforms into reactive progenitor-like (REPL) astrocytes that not only undergo multiple asymmetric divisions but also remain in a multinucleated interstage. This regenerative response facilitates efficient migration of newly formed daughter cell nuclei towards unoccupied astrocyte territories. Our findings define the cellular principles of astrocyte plasticity upon focal lesion, unravelling the REPL phenotype as a fundamental regenerative strategy of mature astrocytes to restore astrocytic networks in the adult mammalian brain. Promoting this regenerative phenotype bears therapeutic potential for neurological conditions involving glial dysfunction.

neuroscience↗

bioRxiv2024

Polyglutamylation of microtubules drives neuronal remodeling

Developmental remodeling shapes neural circuits via activity-dependent pruning of synapses and axons. The cytoskeleton is critical for this process, as microtubule loss via enzymatic severing is an early step of pruning across many circuits and species. However, how microtubule-severing enzymes, such as spastin, are activated in specific neuronal compartments remains unknown. Here, we reveal that polyglutamylation, a posttranslational tubulin modification that is enriched in neurons, plays an instructive role in developmental remodeling by tagging microtubules for severing. Motor neuron-specific gene deletion of enzymes that add or remove tubulin polyglutamylation--TTLL glutamylases vs. CCP deglutamylases--accelerates or delays neuromuscular synapse remodeling in a neurotransmission-dependent manner. This mechanism is not specific to peripheral synapses but also operates in central circuits, e.g., the hippocampus. Thus, tubulin polyglutamylation acts as an activity-dependent rheostat of remodeling and shapes neuronal morphology and connectivity.

cell biology↗

bioRxiv2023

Multimodally trackable and clinically translatable platform for modelling human demyelinating brain diseases by temporally dispersed chemically induced lesions in thepig brain

BackgroundDespite advances in therapy, inflammatory demyelinating diseases of the central nervous system, such as multiple sclerosis, remain important causes of morbidity among young adults. Translation of remyelinating paradigms from current murine models is encumbered by the small size and low white matter content of the brains, limiting the spatial resolution of diagnostic imaging. Large animal models might be more suited for this purpose but pose significant technological, ethical and logistical challenges. MethodWe induced reversible and targeted cerebral demyelinating lesions by controlled injection of lysophosphatidylcholine in the minipig brain. One strength of the approach is the serial induction, allowing parallel imaging of successive stages of de-/remyelination. FindingsWe demonstrate controlled, clinically unapparent, reversible and multimodally trackable brain white matter demyelination in a large animal model. Lesions were amenable to follow-up using the same clinical imaging modalities (3T magnetic resonance imaging, 11C-PIB positron emission tomography) and standard histopathology protocols as for human diagnostics, as well as electron microscopy to compare against biopsy data from two patients with cerebral demyelination. InterpretationBy employing human diagnostic tools and validating the model against data from related human diseases, our platform overcomes one important translational barrier of current animal brain demyelination models while having the potential for developing diagnostic procedures and imaging biomarkers. Remyelination and axon preservation dynamics diverge from classical rodent models. FundingThis work was supported by the DFG under Germanys Excellence Strategy within the framework of the Munich Cluster for Systems Neurology (EXC 2145 SyNergy, ID 390857198) and TRR 274/1 2020, 408885537 (projects B03 and Z01). Research in contextO_ST_ABSEvidence before this studyC_ST_ABSInflammatory demyelinating diseases of the central nervous system (CNS), targeting primarily the white matter (WM) of the brain and spinal cord, such as multiple sclerosis (MS), still represent some of the most important non-traumatic causes of disability in young adults. Current animal models based on murine species, for example, experimental autoimmune encephalomyelitis, have been demonstrated to reliably depict pathophysiological facets of human disease. However, they are nevertheless encumbered by the low WM content and the small size of murine brains, which still pose a translational barrier to diagnostic imaging tools used in a clinical context in human patients. Minipigs are increasingly being used to model human neurological diseases, as yet primarily in the context of neurodegenerative disorders. Added value of this studyHere, we establish a platform for Minipig Stereotactic White-matter Injection using Navigation by Electromagnetism (MiniSWINE) and validate such a tool in a clinical multimodal imaging and microscopy setting against biopsy and imaging data from human demyelinating disorders across different disease stages, as well as against existing and potentially emerging human diagnostic imaging. Moreover, in order to overcome the neuroanatomical challenges of stereotactic injection in the pig brain, we designed a new electromagnetic-guided tracking system whose key advantage is the direct measurement of the injection cannula tip position in situ. Another strength of our study lies in its setup, characterized by the serial induction of successive stages of de- and remyelination, allowing for multimodal assessment via imaging and histopathology or electron microscopy of multiple stages in parallel. The remyelination dynamics inferred in this context diverge from the classical rodent studies, by exhibiting incomplete remyelination at the subacute stage, persistent astroglial and microglial activation as well as a minor degree of secondary axonal degeneration. Thus, they more closely resemble human inflammatory demyelinating brain plaques. Implications of all the available evidenceWe believe that MiniSWINE links evidence from well-established demyelination-induction methods from rodent models of CNS demyelinating disorders, as well as from human imaging and biopsy data, while at the same time providing a novel platform for the potential development of diagnostic procedures, discovery of imaging biomarkers and testing of remyelinating agents in diseases such as MS. Thus, it can have particular relevance to human health in the context of future translational animal model-based research in inflammatory demyelinating disorders of the CNS. Additionally, our electromagnetic-guided injection technique may enhance stereotactic substance delivery in human neurosurgery.

neuroscience↗

bioRxiv2023

ATUM-Tomo: A multi-scale approach to cellular ultrastructure by combined volume scanning electron microscopy and electron tomography

Like other volume electron microscopy approaches, Automated Tape Collecting Ultramicrotomy (ATUM) enables imaging of serial sections deposited on thick plastic tapes by scanning electron microscopy (SEM). ATUM is unique in enabling hierarchical imaging and thus efficient screening for target structures, as needed for correlative light and electron microscopy. However, SEM of sections on tape can only access the section surface, thereby limiting the axial resolution to the typical size of cellular vesicles with an order of magnitude lower than the acquired xy resolution. In contrast, serial-section electron tomography (ET), a transmission electron microscopy-based approach, yields isotropic voxels at full EM resolution, but requires deposition of sections on electron-stable thin and fragile films, thus making screening of large section libraries difficult and prone to section loss. To combine the strength of both approaches, we developed ATUM-Tomo, a hybrid method, where sections are first reversibly attached to plastic tape via a dissolvable coating, and after screening detached and transferred to the ET-compatible thin films. ATUM-SEM of serial semi-thick sections and consecutive ET of selected re-mounted sections combines SEMs fast target recognition and coarse rendering capability with high-resolution volume visualizations, respectively, thus enabling multi-scale interrogation of cellular ultrastructure. As a proof-of-principle, we applied correlative ATUM-Tomo to study ultrastructural features of blood brain barrier (BBB) leakiness around microthrombi in a mouse model of traumatic brain injury. Microthrombi and associated sites of BBB leakiness were identified by confocal imaging of injected fluorescent and electron-dense nanoparticles, then relocalized by ATUM-SEM, and finally interrogated by correlative ATUM-Tomo. This workflow is a seamless zoom-in on structural BBB pathology from the micro- to the nanometer scale. Overall, our new ATUM-Tomo approach will substantially advance ultrastructural analysis of biological phenomena that require cell- and tissue-level contextualization of the finest subcellular textures.

neuroscience↗

bioRxiv2023

Imaging membrane damage in ferroptosis and necrosis by wash-free fluorogenic chemical probes

Selectively labelling cells with damaged membranes is needed in contexts as simple as identifying dead cells in culture, or as complex as imaging membrane barrier functionality in vivo. The commonly used dyes are permanently coloured/fluorescent dyes that are simply excluded by intact membranes, but to achieve good image contrast therefore requires removing their extracellular signal by washing or background subtraction, which are not possible in vivo. Here, we develop fluorogenic probes which sensitively and selectively reveal damaged cells, without needing washing steps since their fluorescence turns on from near-zero background. From a set of novel fluorogenic probes impermeabilised by sulfonations along different vectors, we identify a specific disulfonated fluorogenic scaffold that enters cells only upon membrane damage, where it is enzymatically activated to mark them. The esterase probe iPS-FS2 is a reliable tool to reveal live cells that have been permeabilised by biological, biochemical, or physical membrane damage; and it can be used in multicolour microscopy. We confirm the modularity of this approach by also adapting it for redox-unmasked cell-excluded probes with improved hydrolytic stability. This scaffold-based design thus provides tools for wash-free in vivo imaging of membrane damage, which is relevant across many pathologies. The insightss gained from these probes should also be translatable to damage-targeted prodrugs, for selective therapy of membrane-compromised cells. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=145 SRC="FIGDIR/small/543437v1_ufig1.gif" ALT="Figure 1"> View larger version (53K): org.highwire.dtl.DTLVardef@1594016org.highwire.dtl.DTLVardef@7e7053org.highwire.dtl.DTLVardef@1008cb0org.highwire.dtl.DTLVardef@1148bd7_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2023

Targeting the TCA cycle can ameliorate widespread axonal energy deficiency in neuroinflammatory lesions

Inflammation in the central nervous system (CNS) can impair the function of neuronal mitochondria and contributes to axon degeneration in the common neuroinflammatory disease multiple sclerosis (MS). Here we combine cell type-specific mitochondrial proteomics with in vivo biosensor imaging to dissect how inflammation alters the molecular composition and functional capacity of neuronal mitochondria. We show that neuroinflammatory lesions in the mouse spinal cord cause widespread and persisting axonal ATP deficiency, which precedes mitochondrial oxidation and calcium overload. This axonal energy deficiency is associated with impaired electron transport chain function, but also an upstream imbalance of tricarboxylic acid (TCA) cycle enzymes, with several, including key rate-limiting, enzymes being depleted in neuronal mitochondria in experimental models and in MS lesions. Notably, viral overexpression of individual TCA enzymes can ameliorate the axonal energy deficits in neuroinflammatory lesions, suggesting that TCA cycle dysfunction in MS may be amendable to therapy.

neuroscience↗

bioRxiv2021

Transthyretin promotes axon growth via regulation of microtubule dynamics and tubulin acetylation

Transthyretin (TTR), a plasma and cerebrospinal fluid protein, increases axon growth and organelle transport in sensory neurons. These TTR functions were suggested to underlie its activity in promoting nerve regeneration. While neurons extend their axons, the microtubule (MT) cytoskeleton is crucial for the segregation of functional compartments and axonal outgrowth. Herein, we investigated the hypothesis that TTR promotes axon elongation and regeneration by modulating MT dynamics. Indeed, we found that TTR KO mice have an intrinsic increase in dynamic MTs and reduced levels of acetylated -tubulin in uninjured peripheral axons, and fail to modulate microtubule dynamics in response to sciatic nerve injury. Importantly, restoring acetylated -tubulin levels of TTR KO DRG neurons using an HDAC6 inhibitor was sufficient to completely revert defective MT dynamics and neurite outgrowth. In summary, our results revealed a new role for TTR in the modulation of MT dynamics by regulating -tubulin acetylation and support that this activity underlies TTR neuritogenic function.

neuroscience↗

bioRxiv2020

Multiscale ATUM-FIB microscopy enables targeted ultrastructural analysis at isotropic resolution

Volume electron microscopy enables the ultrastructural analysis of biological tissues and is essential for dense reconstructions e.g. of neuronal circuits. So far, three-dimensional analysis is based on either serial sectioning followed by sequential imaging (ATUM, ssTEM/SEM) or serial block-face imaging (SB-SEM, FIB-SEM), where imaging is intercalated with sectioning. Currently, the techniques involving ultramicrotomy allow scanning large fields of view, but afford only limited z-resolution determined by section thickness, while ion beam-milling approaches yield isotropic voxels, but are restricted in volume size. Now we present a hybrid method, named ATUM-FIB, which combines the advantages of both approaches: ATUM-FIB is based on serial sectioning of tissue into semithick (2-10 {micro}m) resin sections that are collected onto transparent tape. 3D information obtained by serial light and electron microscopy allows identifying regions of interest that are then directly accessible for targeted FIB-SEM. The set of serial semithin sections thus represent a tissue library, which provides information about microscopic tissue context that can then be probed on demand by local high resolution analysis. We demonstrate the potential of this technique to reveal the ultrastructure of rare but pathologically important events by identifying microglia contact sites with amyloid plaques in a mouse model for familial Alzheimers disease.

neuroscience↗

bioRxiv2019

Precision in a sea of profusion: Myelin replacement triggered by single-cell cortical demyelination

Myelin--rather than being a static insulator of axons--is emerging as an active participant in circuit plasticity. This requires precise regulation of oligodendrocyte numbers and myelination patterns. Here, by devising a laser ablation approach of single oligodendrocytes, followed by in vivo imaging and correlated ultrastructural reconstruction, we show that in mouse cortex demyelination as subtle as loss of a single oligodendrocyte can trigger robust cell replacement and remyelination timed by myelin breakdown. This results in reliable reestablishment of the original myelin pattern along continuously myelinated axons, while in parallel profuse isolated internodes emerge on previously unmyelinated axons. Thus, in mammalian cortex, internodes along partially myelinated cortical axons are typically not re-established, suggesting that the cues that guide patchy myelination are not preserved through cycles of de- and remyelination. In contrast, continuous obligatory myelin shows remarkable homeostatic resilience with single axon precision.

neuroscience↗