Biology subjects

Lichtenthaler, S. F.

Publications and source records attributed to Lichtenthaler, S. F..

At least 19 recordsLinked to original sources

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↗

bioRxiv2025

Loss of the Parkinson's disease-associated protein DJ-1 impacts dopamine metabolism in astrocytes

The selective loss of dopaminergic neurons in the substantia nigra is a hallmark of Parkinsons disease (PD), yet the contribution of glial cells to this vulnerability is not fully understood. Studies in rodent models suggest that astrocytes can take up and metabolize dopamine (DA), potentially protecting neurons by detoxifying reactive DA metabolites via glutathione S-transferase mu 2 (GSTM2) release. However, these mechanisms remain underexplored in human systems, particularly in the context of PD. Here, we used CRISPR-engineered iPSC-derived human astrocytes with a PD-linked DJ-1 mutation and isogenic controls to investigate astrocytic DA metabolism. Upon DA exposure, control astrocytes upregulated quinone-reducing enzymes NAD(P)H quinone dehydrogenase 1 (NQO1) and GSTM2, whereas DJ-1 mutant astrocytes failed to adaptively respond. In addition, only control astrocytes presented with increased DA quinone products upon DA exposure, not DJ-1 mutants. These results demonstrate astrocytic DA handling being disrupted in DJ-1-linked PD, implicating astroglial dysfunction as an important contributor to PD pathogenesis and potential target for therapeutic intervention.

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↗

bioRxiv2025

VMAT2 dysfunction impairs vesicular dopamine uptake, driving its oxidation and α-synuclein pathology in DJ-1-linked Parkinson's disease neurons

Parkinsons disease (PD) is characterized by -synuclein accumulation and dopaminergic neuron degeneration, with dopamine (DA) oxidation emerging as a key pathological driver. However, the mechanisms underlying this neurotoxic process remain unclear. Using PD patient-derived and CRISPR-engineered iPSC midbrain dopaminergic neurons lacking DJ-1, we identified defective sequestration of cytosolic DA into synaptic vesicles, which culminated in DA oxidation and -synuclein accumulation. In-depth proteomics, state-of-the-art imaging, and ultrasensitive DA probes uncovered that decreased VMAT2 protein and function impaired vesicular DA uptake, resulting in reduced vesicle availability and abnormal vesicle morphology. Furthermore, VMAT2 activity and vesicle endocytosis are processes dependent on ATP, which is notably reduced in DJ-1-deficient dopaminergic neurons. ATP supplementation restored vesicular function and alleviated DA-related pathologies in mutant dopaminergic neurons. This study reveals an ATP-sensitive mechanism that regulates DA homeostasis through VMAT2 and vesicle dynamics in midbrain dopaminergic neurons, highlighting enhanced DA sequestration as a promising therapeutic strategy for PD. TeaserLoss of DJ-1 interferes with VMAT2 function and vesicle dynamics, leading to DA oxidation and -synuclein pathology in PD neurons.

neuroscience↗

bioRxiv2025

Multiomic profiling reveals aberrant immunomodulatory signature in β-propeller protein-associated neurodegeneration patient iPSC-derived microglia

Microglia are the primary immune cells of the central nervous system and play a crucial role in maintaining brain homeostasis. In common neurodegenerative diseases such as Alzheimers disease and Parkinsons disease (PD), early and sustained microglial activation has been shown to precede neuronal loss, with elevated levels of microglia-derived inflammatory mediators detected in affected brain regions. In contrast, little is known about the role of microglia in rare neurodegenerative disorders. One such disorder is {beta}-propeller protein-associated neurodegeneration (BPAN), a common subtype of neurodegeneration with brain iron accumulation (NBIA). BPAN shares pathological features with PD, including iron accumulation and selective loss of dopaminergic neurons in the substantia nigra, and is caused by mutations in the WD repeat domain 45 (WDR45) gene encoding an autophagy protein also called WIPI4. However, the pathological role of mutant WDR45 in BPAN and the possible contribution of microglia remain unresolved. We generated the first BPAN patient microglia model system using induced pluripotent stem cells (iPSCs) to identify immune-related alterations and immunomodulatory signaling changes in a disease-relevant context. Integrated transcriptomic and proteomic profiling of iPSC-derived microglia from BPAN patients revealed a consistent shift from a homeostatic to a reactive, disease-associated state. Transcriptomic analysis showed disruption of core microglial pathways, including immune activation, stress response, and autophagy, consistent with a chronic pro-inflammatory phenotype. Complementary secretome analysis identified impaired lysosomal function and increased antigen presentation pathways, further supporting persistent microglial activation. Together this suggests that dysfunctional microglial states may contribute to BPAN pathogenesis. Our findings lay the groundwork for advancing immunomodulatory research in BPAN and may open new avenues for therapeutic development targeting microglial dysfunction.

neuroscience↗

bioRxiv2025

BACE1 regulates sleep-wake cycle through both enzymatic and non-enzymatic actions.

The {beta}-secretase BACE1 has become a prime target in Alzheimers disease (AD) therapy, because it drives the production of pathogenic amyloid {beta} peptides. However, clinical trials with BACE1-targeting drugs were halted due to adverse effects on cognitive performance. We propose here that cognitive impairment by BACE1 inhibitors may be a corollary of a higher function of BACE1 related to proper sleep regulation. To address non-enzymatic effects of BACE1 on ion channels likely involved in the sleep-wake cycle, we analyzed sleep patterns in both BACE1-KO mice and a newly generated transgenic line expressing a proteolysis-deficient BACE1 variant (BACE1-KI). We found that BACE1-KI and BACE1-KO mice displayed common and distinct sleep-wake disturbances. Compared to their respective wild-type littermates, both mutant lines slept less during the light phase (when they preferentially rest). Furthermore, transition rates between wake and sleep states were altered, as were sleep spindles and EEG power spectra mainly in the gamma range. Thus, a better understanding of how BACE1 interferes with sleep-modulated behaviors is needed if clinical trials with BACE1-targeted inhibitors are to resume.

animal behavior and cognition↗

bioRxiv2025

Anti-Aβ immunotherapy-mediated amyloid clearance attenuates microglial activation without inducing exhaustion at residual plaques

Anti-amyloid {beta}-peptide (A{beta}) immunotherapy was developed to reduce amyloid plaque pathology and slow cognitive decline during progression of Alzheimers disease. Efficient amyloid plaque clearance has been proven in clinical trials testing anti-A{beta} antibodies, with the impact on cognitive endpoints correlating with the extent of plaque removal. However, treatment is associated with adverse side-effects, such as oedema and haemorrhages, which are potentially linked to the induced immune response. To improve the safety profile of these molecules, it is imperative to understand the consequences of anti-A{beta} antibody treatment on immune cell function. Here, we investigated the effects of long-term chronic anti-A{beta} treatment on amyloid plaque pathology and microglial response in the APP-SAA triple knock-in mouse model. Mice were treated weekly with anti-A{beta} antibody from 4-8 months of age. Long-term treatment with anti-A{beta} results in a robust and dose-dependent removal of amyloid plaque pathology, with a higher efficiency for removing diffuse over dense-core plaques. Analysis of the CSF proteome indicates a reduction of markers for neurodegeneration including Tau and -Synuclein, as well as immune cell related proteins. Bulk RNA-seq revealed a dose-dependent decrease in brain-wide disease-associated microglial (DAM) and glycolytic gene expression, which is supported by a parallel decrease of glucose uptake and protein levels of Triggering receptor of myeloid cells 2 (Trem2) protein, a major immune receptor involved in DAM activation of microglia. In contrast, DAM activation around remaining plaques remains high regardless of treatment dose. In addition, microglia surrounding remaining plaques display a dose-dependent increase in microglial clustering and a selective increase in antigen presenting and immune signalling proteins. These findings demonstrate that long-term chronic anti-A{beta} mediated removal of A{beta} leads to a dose dependent decrease in brain-wide microglial DAM activation and neurodegeneration, while microglia at residual plaques display a combined DAM and antigen presenting phenotype that suggests a continued treatment response. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=161 SRC="FIGDIR/small/645950v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@6d1a49org.highwire.dtl.DTLVardef@d8c14dorg.highwire.dtl.DTLVardef@7ae330org.highwire.dtl.DTLVardef@1d96cc3_HPS_FORMAT_FIGEXP M_FIG Graphical abstract: Schematic overview of the effects of chronic long-term anti-A treatment in APP-SAA mice Schematic was created with BioRender.com C_FIG

neuroscience↗

bioRxiv2024

The late onset Alzheimer's disease risk factor iRhom2/RHBDF2 is a modifier of microglial TREM2 proteolysis

The cell surface receptor TREM2 is a key genetic risk factor and drug target in Alzheimers disease (AD). In the brain, TREM2 is expressed in microglia, where it undergoes proteolytic cleavage, linked to AD risk, but the responsible protease in microglia is still unknown. Another microglia-expressed AD risk factor is catalytically inactive rhomboid 2 (iRhom2, RHBDF2), which binds to and acts as a non-catalytic subunit of the metalloprotease ADAM17. A potential role in TREM2 proteolysis is not yet known. Using microglial-like BV2 cells, bone marrow-derived macrophages and primary murine microglia, we identify iRhom2 as a modifier of ADAM17-mediated TREM2 shedding. Loss of iRhom2 increased TREM2 in cell lysates and at the cell surface and enhanced TREM2 signaling and microglial phagocytosis of the amyloid {beta}-peptide (A{beta}). This study establishes ADAM17 as a physiological TREM2 protease in microglia, and suggests iRhom2 as a potential drug target for modulating TREM2 proteolysis in AD.

biochemistry↗

bioRxiv2024

Protective variant in PLCgamma2 mitigates Alzheimer's disease associated pathology via enhancing beneficial microglia functions

BackgroundPLC{gamma}2-P522R (phospholipase C gamma 2, proline 522 to arginine) is a protective variant that reduces the risk for late onset Alzheimers disease. Recently, it was shown to decrease {beta}-amyloid pathology in 5XFAD mouse model of AD. In this study, our goal was to investigate the protective functions of PLC{gamma}2-P522R variant in a less aggressive mouse model of AD as well as to assess the underlying mechanisms at the molecular and cellular level using mouse and human microglia models. MethodsThe effects of the protective PLC{gamma}2-P522R variant on microglia activation, AD-related {beta}-amyloid and neuronal pathologies, as well as behavioral changes were investigated in PLC{gamma}2-P522R knock-in mice crossbred with APP/PS1 AD model mice. Transcriptomic, proteomic, and functional studies were carried out in cultured and acutely isolated adult PLC{gamma}2-P522R mouse microglia to study molecular mechanisms. Finally, microglia-like cell models generated from blood and skin biopsy samples of the PLC{gamma}2-P522R variant carriers were employed to translate the key findings to human cells. ResultsOur results demonstrate that the PLC{gamma}2-P522R variant reduced brain {beta}-amyloid plaque burden of APP/PS1 mice. Simultaneously, PLC{gamma}2-P522R variant increased non-proinflammatory microglia activation and microglia clustering around {beta}-amyloid plaques, leading to reduced {beta}-amyloid plaque-associated neuronal dystrophy. In cultured mouse primary microglia, PLC{gamma}2-P522R variant decreased accumulation of large lipid droplets, reduced cell stress, and increased acute response to strong inflammatory stimuli. Transcriptomic and proteomic analyses in acutely isolated adult mouse microglia as well as in human monocyte-derived microglial cells showed that PLC{gamma}2-P522R upregulates mitochondrial fatty acid oxidation and downregulates inflammatory/interferon signaling pathways. Accordingly, PLC{gamma}2-P522R increased mitochondrial respiration in iPSC-derived microglial cells. ConclusionsTogether, these findings suggest that PLC{gamma}2-P522R variant exerts protection against AD-associated {beta}-amyloid and neuronal pathologies via enhancing microglial barrier formation around {beta}-amyloid plaques and suppressing pro-inflammatory activation. Observed changes in fatty acid metabolism and mitochondrial flexibility as well as the downregulation of genes involved in inflammatory signaling pathways suggest that these protective effects of the PLC{gamma}2-P522R variant are mediated through an anti-ageing mechanism.

neuroscience↗

bioRxiv2024

An improved method for sampling and quantitative protein analytics of cerebrospinal fluid of single mice

Mice are the most commonly used preclinical animal model, but protein analytics of murine cerebrospinal fluid (CSF) remains challenging because of low CSF volume (often <10 {micro}l) and frequent blood contaminations. We developed an improved CSF sampling method that allows routine collection of increased volumes (20-30 {micro}l) of pure CSF from individual mice, enabling multiple protein analytical assays from a single sample. Based on cell counts and hemoglobin ELISAs, we provide an easy quality control workflow for obtaining cell- and blood-free murine CSF. Through mass spectrometry-based proteomics using an absolutely quantified external standard, we estimated concentrations for hundreds of mouse CSF proteins. While repeated CSF sampling from the same mouse was possible, it induced CSF proteome changes. Applying the improved method, we found that the mouse CSF proteome remains largely stable over time in wild-type mice, but that amyloid pathology in the 5xFAD mouse model of Alzheimers disease massively changes the CSF proteome. Neurofilament light chain and TREM2, markers of neurodegeneration and activated microglia, respectively, were strongly upregulated and validated using immunoassays. In conclusion, our refined murine CSF collection method overcomes previous limitations, allowing multiple quantitative protein analyses for applications in biomedicine.

neuroscience↗

bioRxiv2024

Loss of CLN3 in microglia leads to impaired lipid metabolism and myelin turnover

BackgroundMicroglia are the primary brain cell type regulating neuroinflammation and they are important for healthy aging. Genes regulating microglial function are associated with an increased risk of neurodegenerative disease. Loss-of-function mutations in CLN3, which encodes an endolysosomal membrane protein, lead to the most common childhood-onset form of neurodegeneration, featuring early-stage neuroinflammation that long precedes neuronal cell loss. How loss of CLN3 function leads to this early neuroinflammation is not yet understood. MethodsHere, we have comprehensively studied microglia from Cln3{Delta}ex7/8 mice, a genetically accurate CLN3 disease model. Microglia were isolated from young and old Cln3{Delta}ex7/8 mice for downstream molecular and functional studies. ResultsWe show that loss of CLN3 function in microglia leads to classic age-dependent CLN3-disease lysosomal storage as well as an altered morphology of the lysosome, mitochonodria and Golgi compartments. Consistent with these morphological alterations, we also discovered pathological proteomic signatures implicating defects in lysosomal function and lipid metabolism processes at an early disease stage. CLN3-deficient microglia were unable to efficiently turnover myelin and metabolize its associated lipids, showing severe defects in lipid droplet formation and significant accumulation of cholesterol, phenotypes that were corrected by treatment with autophagy inducers and cholesterol lowering drugs. Finally, we observed reduced myelination in aging homozygous Cln3{Delta}ex7/8 mice suggesting altered myelin turnover by microglia impacts myelination in the CLN3-deficient brain. ConclusionOur results implicate a cell autonomous defect in CLN3-deficient microglia that impacts the ability of these cells to support neuronal cell health. These results strongly suggest microglial targeted therapies should be considered for CLN3 disease.

neuroscience↗

bioRxiv2023

Cleavage site-directed antibodies reveal the prion protein in humans is shed by ADAM10 at Y226 and associates with misfolded protein deposits in neurodegenerative diseases

Proteolytic cell surface release ( shedding) of the prion protein (PrP), a broadly expressed GPI-anchored glycoprotein, by the metalloprotease ADAM10 impacts on neurodegenerative and other diseases in animal and in vitro models. Recent studies employing the latter also suggest shed PrP (sPrP) to be a ligand in intercellular communication and critically involved in PrP-associated physiological tasks. Although expectedly an evolutionary conserved event, and while soluble forms of PrP are present in human tissues and body fluids, neither proteolytic PrP shedding and its cleavage site nor involvement of ADAM10 or the biological relevance of this process have been demonstrated for the human body thus far. In this study, cleavage site prediction and generation (plus detailed characterization) of sPrP-specific antibodies enabled us to identify PrP cleaved at tyrosin 226 as the physiological and strictly ADAM10-dependent shed form in humans. Using cell lines, neural stem cells and brain organoids, we show that shedding of human PrP can be stimulated by PrP-binding ligands without targeting the protease, which may open novel therapeutic perspectives. Site-specific antibodies directed against human sPrP also detect the shed form in brains of cattle, sheep and deer, hence in all most relevant species naturally affected by fatal and transmissible prion diseases. In human and animal prion diseases, but also in patients with Alzheimers disease, sPrP relocalizes from a physiological diffuse tissue pattern to intimately associate with extracellular aggregates of misfolded proteins characteristic for the respective pathological condition. Findings and research tools presented here will accelerate novel insight into the roles of PrP shedding (as a process) and sPrP (as a released factor) in neurodegeneration and beyond.

neuroscience↗

bioRxiv2023

A MICROGLIAL ACTIVITY STATE BIOMARKER PANEL DIFFERENTIATES FTD-GRANULIN AND AD FROM CONTROL CASES

SummaryO_ST_ABSBackgroundC_ST_ABSWith the emergence of microglia-modulating therapies there is an urgent need for reliable biomarkers to evaluate microglial activation states. MethodsUsing mouse models and human induced pluripotent stem cell-derived microglia (hiMGL), which were genetically modified to yield the most opposite homeostatic (TREM2- knockout) and disease-associated (GRN-knockout) states, we identified microglia activity-dependent markers. Non-targeted mass spectrometry was used to identify changes in microglial and cerebrospinal (CSF) proteome of Grn- and Trem2-knockout mice. Additionally, we analyzed the proteome of GRN- and TREM2-knockout hiMGL and their conditioned media. Candidate marker proteins were tested in two independent patient cohorts, the ALLFTD cohort with 11 GRN mutation carriers and 12 non-carriers, as well as the proteomic data set available from the European Medical Information Framework Alzheimers Disease Multimodal Biomarker Discovery (EMIF-AD MBD). FindingsWe identified proteomic changes between the opposite activation states in mouse microglia and cerebrospinal fluid (CSF), as well as in hiMGL cell lysates and conditioned media. For further verification, we analyzed the CSF proteome of heterozygous GRN mutation carriers suffering from frontotemporal dementia (FTD). We identified a panel of six proteins (FABP3, MDH1, GDI1, CAPG, CD44, GPNMB) as potential indicators for microglial activation. Moreover, we confirmed three of these proteins (FABP3, GDI1, MDH1) to be significantly elevated in the CSF of AD patients. In AD, these markers differentiated amyloid-positive cases with mild cognitive impairment (MCI) from amyloid-negative individuals. InterpretationThe identified candidate proteins reflect microglia activity and may be relevant for monitoring the microglial response in clinical practice and clinical trials modulating microglial activity and amyloid deposition. Moreover, the finding that three of these markers differentiate amyloid-positive from amyloid-negative MCI cases in the AD cohort suggests that these marker proteins associate with a very early immune response to seeded amyloid. This is consistent with our previous findings in the DIAN (Dominantly Inherited Alzheimers Disease Network) cohort, where soluble TREM2 increases as early as 21 years before symptom onset. Moreover, in mouse models for amyloidogenesis, seeding of amyloid is limited by physiologically active microglia further supporting their early protective role. The biological functions of some of our main candidates (FABP3, CD44, GPNMB) also further emphasize that lipid dysmetabolism may be a common feature of neurodegenerative disorders. FundingThis work was supported by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germanys Excellence Strategy within the framework of the Munich Cluster for Systems Neurology (EXC 2145 SyNergy - ID 390857198 to CH, SFL and DP) and a Koselleck Project HA1737/16-1 (to CH).

neuroscience↗

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↗

bioRxiv2023

Deciphering sources of PET signals in the tumor microenvironment of glioblastoma at cellular resolution

Various cellular sources hamper interpretation of positron-emission-tomography (PET) biomarkers in the tumor microenvironment (TME). We developed immunomagnetic cell sorting after in vivo radiotracer injection (scRadiotracing) in combination with 3D-histology via tissue clearing to dissect the cellular allocation of PET signals in the TME. In SB28 glioblastoma mice, translocator protein (TSPO) radiotracer uptake per tumor cell was higher compared to tumor-associated microglia/macrophages (TAMs). Cellular radiotracer uptake was validated by proteomics and confirmed for in vitro samples of patients with glioblastoma. Regional agreement between PET signals and single cell tracer uptake predicted the individual cell distribution in 3D-histology. In consideration of cellular tracer uptake and cell type abundance, tumor cells were the main contributor to TSPO enrichment in glioblastoma, however proteomics identified potential PET targets highly specific for TAMs. Combining cellular tracer uptake measures with 3D-histology facilitates precise allocation of complex PET signal sources and will serve to validate novel TAM-specific radioligands.

neuroscience↗

bioRxiv2022

Semaphorin 4B is an ADAM17-cleaved inhibitor of adipocyte thermogenesis

ObjectiveThe metalloprotease ADAM17 (also called TACE) plays fundamental roles in homeostasis by shedding key signaling molecules from the cell surface. Although its importance for the immune system and epithelial tissues is well-documented, little is known about the role of ADAM17 in metabolic homeostasis. The purpose of this study was to determine the impact of ADAM17 expression, specifically in adipose tissues, on metabolic homeostasis. MethodsWe used histopathology, molecular, proteomic, transcriptomic, in vivo integrative physiological and ex vivo biochemical approaches to determine the impact of adipose tissue-specific deletion of ADAM17 upon adipocyte and whole organism metabolic physiology. ResultsADAM17adipoq-cre{Delta}/{Delta} mice exhibited a hypermetabolic phenotype characterized by elevated energy consumption and increased levels of adipocyte thermogenic gene expression. On a high fat diet, these mice were more thermogenic, while exhibiting elevated expression levels of genes associated with lipid oxidation and lipolysis. This hypermetabolic phenotype protected mutant mice from obesogenic challenge, limiting weight gain, hepatosteatosis and insulin resistance. Activation of beta-adrenoceptors by the neurotransmitter norepinephrine, a key regulator of adipocyte physiology, triggered the shedding of ADAM17 substrates, and regulated ADAM17 expression at the mRNA and protein levels, hence identifying a functional connection between thermogenic licensing and the regulation of ADAM17. Proteomic studies identified Semaphorin 4B (SEMA4B), as a novel ADAM17-shed adipokine, whose expression is regulated by physiological thermogenic cues that acts to dampen thermogenic responses in adipocytes. Transcriptomic data showed that cleaved SEMA4B acts in an autocrine manner in brown adipocytes to dampen the expression of genes involved in thermogenesis, adipogenesis, lipid uptake, storage and catabolism. ConclusionOur findings identify a novel ADAM17-dependent axis, regulated by beta-adrenoceptors and mediated by the ADAM17-cleaved form of SEMA4B, that may act to limit uncontrolled energy depletion during thermogenesis.

physiology↗

bioRxiv2022

Endogenous retroviruses promote prion-like spreading of proteopathic seeds

Endogenous retroviruses, remnants of viral germline infections, make up a substantial proportion of the mammalian genome. While usually epigenetically silenced, retroelements can become upregulated in neurodegenerative diseases associated with protein aggregation, such as amyotrophic lateral sclerosis and tauopathies. Here we demonstrate that spontaneous upregulation of endogenous retrovirus gene expression drastically affects the dissemination of protein aggregates between murine cells in culture. Viral glycoprotein Env mediates membrane association between donor and recipient cells and promotes the intercellular transfer of protein aggregates packaged into extracellular vesicles. Proteopathic seed spreading can be inhibited by neutralizing antibodies targeting Env as well as drugs inhibiting viral protein processing. Importantly, we show that also overexpression of a human endogenous retrovirus Env elevates intercellular spreading of pathological Tau. Our data highlight the potential influence of endogenous retroviral proteins on protein misfolding diseases and suggest that antiviral drugs could represent promising candidates for inhibiting protein aggregate spreading.

neuroscience↗

bioRxiv2022

LncRNA RUS shapes the gene expression program towards neurogenesis

The evolution of brain complexity correlates with an increased expression of long, non- coding (lnc) RNAs in neural tissues. Although prominent examples illustrate the potential of lncRNAs to scaffold and target epigenetic regulators to chromatin loci, only few cases have been described to function during brain development. We present a first functional characterization of the lncRNA LINC01322, which we term RUS for RNA upstream of Slitrk3. The RUS gene is well conserved in mammals by sequence and synteny next to the neurodevelopmental gene Slitrk3. RUS is exclusively expressed in neural cells and its expression increases along with neuronal markers during neuronal differentiation of mouse embryonic cortical neural stem cells. Depletion of RUS locks neuronal precursors in an intermediate state towards neuronal differentiation resulting in arrested cell cycle and increased apoptosis. RUS associates with chromatin in the vicinity of genes involved in neurogenesis, most of which change their expression upon RUS depletion. The identification of a range of epigenetic regulators as specific RUS interactors suggests that the lncRNA may mediate gene activation and repression in a highly context-dependent manner.

molecular biology↗