Publications by authors named "Amparo Acker-Palmer"

52 Publications

The angiopoietin-Tie2 pathway regulates Purkinje cell dendritic morphogenesis in a cell-autonomous manner.

Cell Rep 2021 Aug;36(7):109522

European Center of Angioscience (ECAS), Medical Faculty Mannheim, University of Heidelberg, 68167 Mannheim, Germany. Electronic address:

Neuro-vascular communication is essential to synchronize central nervous system development. Here, we identify angiopoietin/Tie2 as a neuro-vascular signaling axis involved in regulating dendritic morphogenesis of Purkinje cells (PCs). We show that in the developing cerebellum Tie2 expression is not restricted to blood vessels, but it is also present in PCs. Its ligands angiopoietin-1 (Ang1) and angiopoietin-2 (Ang2) are expressed in neural cells and endothelial cells (ECs), respectively. PC-specific deletion of Tie2 results in reduced dendritic arborization, which is recapitulated in neural-specific Ang1-knockout and Ang2 full-knockout mice. Mechanistically, RNA sequencing reveals that Tie2-deficient PCs present alterations in gene expression of multiple genes involved in cytoskeleton organization, dendritic formation, growth, and branching. Functionally, mice with deletion of Tie2 in PCs present alterations in PC network functionality. Altogether, our data propose Ang/Tie2 signaling as a mediator of intercellular communication between neural cells, ECs, and PCs, required for proper PC dendritic morphogenesis and function.
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http://dx.doi.org/10.1016/j.celrep.2021.109522DOI Listing
August 2021

Neurovascular crosstalk coordinates the central nervous system development.

Curr Opin Neurobiol 2021 08 30;69:202-213. Epub 2021 May 30.

Neuro and Vascular Guidance, Buchmann Institute for Molecular Life Sciences (BMLS) and Institute of Cell Biology and Neuroscience, Max-von-Laue-Str. 15, D-60438, Frankfurt am Main, Germany; Cardio-Pulmonary Institute (CPI), Max-von-Laue-Str. 15, Frankfurt am Main, D-60438, Germany; Max Planck Institute for Brain Research, Max-von-Laue-Str. 4 Frankfurt am Main, 60438, Germany. Electronic address:

Purpose Of The Review: The synchronic development of vascular and nervous systems is orchestrated by common molecules that regulate the communication between both systems. The identification of these common guiding cues and the developmental processes regulated by neurovascular communication are slowly emerging. In this review, we describe the molecules modulating the neurovascular development and their impact in processes such as angiogenesis, neurogenesis, neuronal migration, and brain homeostasis.

Recent Findings: Blood vessels not only are involved in nutrient and oxygen supply of the central nervous system (CNS) but also exert instrumental functions controlling developmental neurogenesis, CNS cytoarchitecture, and neuronal plasticity. Conversely, neurons modulate CNS vascularization and brain endothelial properties such as blood-brain barrier and vascular hyperemia.

Summary: The integration of the active role of endothelial cells in the development and maintenance of neuronal function is important to obtain a more holistic view of the CNS complexity and also to understand how the vasculature is involved in neuropathological conditions.
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http://dx.doi.org/10.1016/j.conb.2021.04.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8411665PMC
August 2021

EphrinB2 and GRIP1 stabilize mushroom spines during denervation-induced homeostatic plasticity.

Cell Rep 2021 03;34(13):108923

Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences (BMLS), University of Frankfurt, Max-von-Laue-Str. 15, 60438 Frankfurt am Main, Germany; Max Planck Institute for Brain Research, Max von Laue Str. 4, 60438 Frankfurt am Main, Germany; Cardio-Pulmonary Institute (CPI), Max-von-Laue-Str. 15, 60438 Frankfurt am Main, Germany. Electronic address:

Despite decades of work, much remains elusive about molecular events at the interplay between physiological and structural changes underlying neuronal plasticity. Here, we combined repetitive live imaging and expansion microscopy in organotypic brain slice cultures to quantitatively characterize the dynamic changes of the intracellular versus surface pools of GluA2-containing α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors (AMPARs) across the different dendritic spine types and the shaft during hippocampal homeostatic plasticity. Mechanistically, we identify ephrinB2 and glutamate receptor interacting protein (GRIP) 1 as mediating AMPAR relocation to the mushroom spine surface following lesion-induced denervation. Moreover, stimulation with the ephrinB2 specific receptor EphB4 not only prevents the lesion-induced disappearance of mushroom spines but is also sufficient to shift AMPARs to the surface and rescue spine recovery in a GRIP1 dominant-negative background. Thus, our results unravel a crucial role for ephrinB2 during homeostatic plasticity and identify a potential pharmacological target to improve dendritic spine plasticity upon injury.
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http://dx.doi.org/10.1016/j.celrep.2021.108923DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8028307PMC
March 2021

EVL regulates VEGF receptor-2 internalization and signaling in developmental angiogenesis.

EMBO Rep 2021 02 29;22(2):e48961. Epub 2021 Jan 29.

Centre for Molecular Medicine, Institute for Vascular Signalling, Goethe University, Frankfurt am Main, Germany.

Endothelial tip cells are essential for VEGF-induced angiogenesis, but underlying mechanisms are elusive. The Ena/VASP protein family, consisting of EVL, VASP, and Mena, plays a pivotal role in axon guidance. Given that axonal growth cones and endothelial tip cells share many common features, from the morphological to the molecular level, we investigated the role of Ena/VASP proteins in angiogenesis. EVL and VASP, but not Mena, are expressed in endothelial cells of the postnatal mouse retina. Global deletion of EVL (but not VASP) compromises the radial sprouting of the vascular plexus in mice. Similarly, endothelial-specific EVL deletion compromises the radial sprouting of the vascular plexus and reduces the endothelial tip cell density and filopodia formation. Gene sets involved in blood vessel development and angiogenesis are down-regulated in EVL-deficient P5-retinal endothelial cells. Consistently, EVL deletion impairs VEGF-induced endothelial cell proliferation and sprouting, and reduces the internalization and phosphorylation of VEGF receptor 2 and its downstream signaling via the MAPK/ERK pathway. Together, we show that endothelial EVL regulates sprouting angiogenesis via VEGF receptor-2 internalization and signaling.
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http://dx.doi.org/10.15252/embr.201948961DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7857432PMC
February 2021

Blood-Brain Barrier Dynamics to Maintain Brain Homeostasis.

Trends Neurosci 2021 05 7;44(5):393-405. Epub 2021 Jan 7.

Neuro and Vascular Guidance, Buchmann Institute for Molecular Life Sciences (BMLS) and Institute of Cell Biology and Neuroscience, Max-von-Laue-Strasse 15, D-60438, Frankfurt am Main, Germany; Cardio-Pulmonary Institute (CPI), Max-von-Laue-Strasse 15, D-60438, Frankfurt am Main, Germany; Max Planck Institute for Brain Research, Max-von-Laue-Strasse 4, 60438 Frankfurt am Main, Germany. Electronic address:

The blood-brain barrier (BBB) is a dynamic platform for exchange of substances between the blood and the brain parenchyma, and it is an essential functional gatekeeper for the central nervous system (CNS). While it is widely recognized that BBB disruption is a hallmark of several neurovascular pathologies, an aspect of the BBB that has received somewhat less attention is the dynamic modulation of BBB tightness to maintain brain homeostasis in response to extrinsic environmental factors and physiological changes. In this review, we summarize how BBB integrity adjusts in critical stages along the life span, as well as how BBB permeability can be altered by common stressors derived from nutritional habits, environmental factors and psychological stress.
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http://dx.doi.org/10.1016/j.tins.2020.12.002DOI Listing
May 2021

Inhibition of Tumor VEGFR2 Induces Serine 897 EphA2-Dependent Tumor Cell Invasion and Metastasis in NSCLC.

Cell Rep 2020 04;31(4):107568

Department I of Internal Medicine, Center for Integrated Oncology Aachen Bonn Cologne Duesseldorf, University of Cologne, Cologne, Germany; Center for Molecular Medicine, Cologne, Germany. Electronic address:

Anti-angiogenic treatment targeting vascular endothelial growth factor (VEGF)-VEGFR2 signaling has shown limited efficacy in lung cancer patients. Here, we demonstrate that inhibition of VEGFR2 in tumor cells, expressed in ∼20% of non-squamous non-small cell lung cancer (NSCLC) patients, leads to a pro-invasive phenotype. Drug-induced inhibition of tumor VEGFR2 interferes with the formation of the EphA2/VEGFR2 heterocomplex, thereby allowing RSK to interact with Serine 897 of EphA2. Inhibition of RSK decreases phosphorylation of Serine 897 EphA2. Selective genetic modeling of Serine 897 of EphA2 or inhibition of EphA2 abrogates the formation of metastases in vivo upon VEGFR2 inhibition. In summary, these findings demonstrate that VEGFR2-targeted therapy conditions VEGFR2-positive NSCLC to Serine 897 EphA2-dependent aggressive tumor growth and metastasis. These data shed light on the molecular mechanisms explaining the limited efficacy of VEGFR2-targeted anti-angiogenic treatment in lung cancer patients.
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http://dx.doi.org/10.1016/j.celrep.2020.107568DOI Listing
April 2020

Carotid body type I cells engage flavoprotein and Pin1 for oxygen sensing.

Am J Physiol Cell Physiol 2020 04 22;318(4):C719-C731. Epub 2020 Jan 22.

Institute of Physiology, University of Duisburg-Essen, Essen, Germany.

Carotid body (CB) type I cells sense the blood Po and generate a nervous signal for stimulating ventilation and circulation when blood oxygen levels decline. Three oxygen-sensing enzyme complexes may be used for this purpose: ) mitochondrial electron transport chain metabolism, ) heme oxygenase 2 (HO-2)-generating CO, and/or ) an NAD(P)H oxidase (NOX). We hypothesize that intracellular redox changes are the link between the sensor and nervous signals. To test this hypothesis type I cell autofluorescence of flavoproteins (Fp) and NAD(P)H within the mouse CB ex vivo was recorded as Fp/(Fp+NAD(P)H) redox ratio. CB type I cell redox ratio transiently declined with the onset of hypoxia. Upon reoxygenation, CB type I cells showed a significantly increased redox ratio. As a control organ, the non-oxygen-sensing sympathetic superior cervical ganglion (SCG) showed a continuously reduced redox ratio upon hypoxia. CN, diphenyleneiodonium, or reactive oxygen species influenced chemoreceptor discharge (CND) with subsequent loss of O sensitivity and inhibited hypoxic Fp reduction only in the CB but not in SCG Fp, indicating a specific role of Fp in the oxygen-sensing process. Hypoxia-induced changes in CB type I cell redox ratio affected peptidyl prolyl isomerase Pin1, which is believed to colocalize with the NADPH oxidase subunit p47 in the cell membrane to trigger the opening of potassium channels. We postulate that hypoxia-induced changes in the Fp-mediated redox ratio of the CB regulate the Pin1/p47 tandem to alter type I cell potassium channels and therewith CND.
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http://dx.doi.org/10.1152/ajpcell.00320.2019DOI Listing
April 2020

p120-catenin-dependent collective brain infiltration by glioma cell networks.

Nat Cell Biol 2020 01 6;22(1):97-107. Epub 2020 Jan 6.

Department of Cell Biology, Radboud University Medical Center, Nijmegen, The Netherlands.

Diffuse brain infiltration by glioma cells causes detrimental disease progression, but its multicellular coordination is poorly understood. We show here that glioma cells infiltrate the brain collectively as multicellular networks. Contacts between moving glioma cells are adaptive epithelial-like or filamentous junctions stabilized by N-cadherin, β-catenin and p120-catenin, which undergo kinetic turnover, transmit intercellular calcium transients and mediate directional persistence. Downregulation of p120-catenin compromises cell-cell interaction and communication, disrupts collective networks, and both the cadherin and RhoA binding domains of p120-catenin are required for network formation and migration. Deregulating p120-catenin further prevents diffuse glioma cell infiltration of the mouse brain with marginalized microlesions as the outcome. Transcriptomics analysis has identified p120-catenin as an upstream regulator of neurogenesis and cell cycle pathways and a predictor of poor clinical outcome in glioma patients. Collective glioma networks infiltrating the brain thus depend on adherens junctions dynamics, the targeting of which may offer an unanticipated strategy to halt glioma progression.
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http://dx.doi.org/10.1038/s41556-019-0443-xDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6952556PMC
January 2020

EphrinB2 regulates VEGFR2 during dendritogenesis and hippocampal circuitry development.

Elife 2019 12 23;8. Epub 2019 Dec 23.

Institute of Cell Biology and Neuroscience, University of Frankfurt, Frankfurt, Germany.

Vascular endothelial growth factor (VEGF) is an angiogenic factor that play important roles in the nervous system, although it is still unclear which receptors transduce those signals in neurons. Here, we show that in the developing hippocampus VEGFR2 (also known as KDR or FLK1) is expressed specifically in the CA3 region and it is required for dendritic arborization and spine morphogenesis in hippocampal neurons. Mice lacking VEGFR2 in neurons () show decreased dendritic arbors and spines as well as a reduction in long-term potentiation (LTP) at the associational-commissural - CA3 synapses. Mechanistically, VEGFR2 internalization is required for VEGF-induced spine maturation. In analogy to endothelial cells, ephrinB2 controls VEGFR2 internalization in neurons. VEGFR2-ephrinB2 compound mice () show reduced dendritic branching, reduced spine head size and impaired LTP. Our results demonstrate the functional crosstalk of VEGFR2 and ephrinB2 in vivo to control dendritic arborization, spine morphogenesis and hippocampal circuitry development.
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http://dx.doi.org/10.7554/eLife.49819DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6927743PMC
December 2019

VEGF/VEGFR2 signaling regulates hippocampal axon branching during development.

Elife 2019 12 23;8. Epub 2019 Dec 23.

Biochemistry Center (BZH), University of Heidelberg, Heidelberg, Germany.

Axon branching is crucial for proper formation of neuronal networks. Although originally identified as an angiogenic factor, VEGF also signals directly to neurons to regulate their development and function. Here we show that VEGF and its receptor VEGFR2 (also known as KDR or FLK1) are expressed in mouse hippocampal neurons during development, with VEGFR2 locally expressed in the CA3 region. Activation of VEGF/VEGFR2 signaling in isolated hippocampal neurons results in increased axon branching. Remarkably, inactivation of VEGFR2 also results in increased axon branching in vitro and in vivo. The increased CA3 axon branching is not productive as these axons are less mature and form less functional synapses with CA1 neurons. Mechanistically, while VEGF promotes the growth of formed branches without affecting filopodia formation, loss of VEGFR2 increases the number of filopodia and enhances the growth rate of new branches. Thus, a controlled VEGF/VEGFR2 signaling is required for proper CA3 hippocampal axon branching during mouse hippocampus development.
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http://dx.doi.org/10.7554/eLife.49818DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6927742PMC
December 2019

Deep Learning Reveals Cancer Metastasis and Therapeutic Antibody Targeting in the Entire Body.

Cell 2019 Dec;179(7):1661-1676.e19

Institute for Tissue Engineering and Regenerative Medicine (iTERM), Helmholtz Zentrum München, 85764 Neuherberg, Germany; Institute for Stroke and Dementia Research, Klinikum der Universität München, Ludwig Maximilian University of Munich (LMU), 81377 Munich, Germany; Munich Cluster for Systems Neurology (SyNergy), 81377 Munich, Germany. Electronic address:

Reliable detection of disseminated tumor cells and of the biodistribution of tumor-targeting therapeutic antibodies within the entire body has long been needed to better understand and treat cancer metastasis. Here, we developed an integrated pipeline for automated quantification of cancer metastases and therapeutic antibody targeting, named DeepMACT. First, we enhanced the fluorescent signal of cancer cells more than 100-fold by applying the vDISCO method to image metastasis in transparent mice. Second, we developed deep learning algorithms for automated quantification of metastases with an accuracy matching human expert manual annotation. Deep learning-based quantification in 5 different metastatic cancer models including breast, lung, and pancreatic cancer with distinct organotropisms allowed us to systematically analyze features such as size, shape, spatial distribution, and the degree to which metastases are targeted by a therapeutic monoclonal antibody in entire mice. DeepMACT can thus considerably improve the discovery of effective antibody-based therapeutics at the pre-clinical stage. VIDEO ABSTRACT.
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http://dx.doi.org/10.1016/j.cell.2019.11.013DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7591821PMC
December 2019

Neurovascular Interactions in the Nervous System.

Annu Rev Cell Dev Biol 2019 10;35:615-635

Neuro and Vascular Guidance, Buchmann Institute for Molecular Life Sciences, University of Frankfurt, D-60438 Frankfurt am Main, Germany; email:

Molecular cross talk between the nervous and vascular systems is necessary to maintain the correct coupling of organ structure and function. Molecular pathways shared by both systems are emerging as major players in the communication of the neuronal compartment with the endothelium. Here we review different aspects of this cross talk and how vessels influence the development and homeostasis of the nervous system. Beyond the classical role of the vasculature as a conduit to deliver oxygen and metabolites needed for the energy-demanding neuronal compartment, vessels emerge as powerful signaling systems that control and instruct a variety of cellular processes during the development of neurons and glia, such as migration, differentiation, and structural connectivity. Moreover, a broad spectrum of mild to severe vascular dysfunctions occur in various pathologies of the nervous system, suggesting that mild structural and functional changes at the neurovascular interface may underlie cognitive decline in many of these pathological conditions.
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http://dx.doi.org/10.1146/annurev-cellbio-100818-125142DOI Listing
October 2019

AMPA receptors and their minions: auxiliary proteins in AMPA receptor trafficking.

Cell Mol Life Sci 2019 Jun 1;76(11):2133-2169. Epub 2019 Apr 1.

Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences (BMLS), University of Frankfurt, Max-von-Laue-Str. 15, 60438, Frankfurt am Main, Germany.

To correctly transfer information, neuronal networks need to continuously adjust their synaptic strength to extrinsic stimuli. This ability, termed synaptic plasticity, is at the heart of their function and is, thus, tightly regulated. In glutamatergic neurons, synaptic strength is controlled by the number and function of AMPA receptors at the postsynapse, which mediate most of the fast excitatory transmission in the central nervous system. Their trafficking to, at, and from the synapse, is, therefore, a key mechanism underlying synaptic plasticity. Intensive research over the last 20 years has revealed the increasing importance of interacting proteins, which accompany AMPA receptors throughout their lifetime and help to refine the temporal and spatial modulation of their trafficking and function. In this review, we discuss the current knowledge about the roles of key partners in regulating AMPA receptor trafficking and focus especially on the movement between the intracellular, extrasynaptic, and synaptic pools. We examine their involvement not only in basal synaptic function, but also in Hebbian and homeostatic plasticity. Included in our review are well-established AMPA receptor interactants such as GRIP1 and PICK1, the classical auxiliary subunits TARP and CNIH, and the newest additions to AMPA receptor native complexes.
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http://dx.doi.org/10.1007/s00018-019-03068-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6502786PMC
June 2019

Loss of the Chr16p11.2 ASD candidate gene leads to aberrant neuronal differentiation in the SH-SY5Y neuronal cell model.

Mol Autism 2018 6;9:56. Epub 2018 Nov 6.

1Department of Child and Adolescent Psychiatry, Psychosomatics and Psychotherapy, University Hospital Frankfurt, JW Goethe University Frankfurt, Frankfurt am Main, Germany.

Background: Altered neuronal development is discussed as the underlying pathogenic mechanism of autism spectrum disorders (ASD). Copy number variations of 16p11.2 have recurrently been identified in individuals with ASD. Of the 29 genes within this region, () showed the strongest regulation during neuronal differentiation of SH-SY5Y neuroblastoma cells. We hypothesized a causal relation between this tryptophan metabolism-related enzyme and neuronal differentiation. We thus analyzed the effect of on the differentiation of SH-SY5Y and specifically focused on neuronal morphology, metabolites of the tryptophan pathway, and the neurodevelopmental transcriptome.

Methods: The gene dosage-dependent change of expression following Chr16p11.2 deletion was investigated in a lymphoblastoid cell line (LCL) of a deletion carrier and compared to his non-carrier parents. Expression of was tested for correlation with neuromorphology in SH-SY5Y cells. QPRT function was inhibited in SH-SY5Y neuroblastoma cells using (i) siRNA knockdown (KD), (ii) chemical mimicking of loss of QPRT, and (iii) complete CRISPR/Cas9-mediated knock out (KO). - cells underwent morphological analysis. Chemically inhibited and cells were characterized using viability assays. Additionally, cells underwent metabolite and whole transcriptome analyses. Genes differentially expressed upon KO of were tested for enrichment in biological processes and co-regulated gene-networks of the human brain.

Results: expression was reduced in the LCL of the deletion carrier and significantly correlated with the neuritic complexity of SH-SY5Y. The reduction of altered neuronal morphology of differentiated SH-SY5Y cells. Chemical inhibition as well as complete KO of the gene were lethal upon induction of neuronal differentiation, but not proliferation. The QPRT-associated tryptophan pathway was not affected by KO. At the transcriptome level, genes linked to neurodevelopmental processes and synaptic structures were affected. Differentially regulated genes were enriched for ASD candidates, and co-regulated gene networks were implicated in the development of the dorsolateral prefrontal cortex, the hippocampus, and the amygdala.

Conclusions: In this study, was causally related to in vitro neuronal differentiation of SH-SY5Y cells and affected the regulation of genes and gene networks previously implicated in ASD. Thus, our data suggest that may play an important role in the pathogenesis of ASD in Chr16p11.2 deletion carriers.
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http://dx.doi.org/10.1186/s13229-018-0239-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6220561PMC
December 2018

Endothelial Dab1 signaling orchestrates neuro-glia-vessel communication in the central nervous system.

Science 2018 08;361(6404)

Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences, University of Frankfurt, D-60438 Frankfurt am Main, Germany.

The architecture of the neurovascular unit (NVU) is controlled by the communication of neurons, glia, and vascular cells. We found that the neuronal guidance cue reelin possesses proangiogenic activities that ensure the communication of endothelial cells (ECs) with the glia to control neuronal migration and the establishment of the blood-brain barrier in the mouse brain. Apolipoprotein E receptor 2 (ApoER2) and Disabled1 (Dab1) expressed in ECs are required for vascularization of the retina and the cerebral cortex. Deletion of Dab1 in ECs leads to a reduced secretion of laminin-α4 and decreased activation of integrin-β1 in glial cells, which in turn control neuronal migration and barrier properties of the NVU. Thus, reelin signaling in the endothelium is an instructive and integrative cue essential for neuro-glia-vascular communication.
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http://dx.doi.org/10.1126/science.aao2861DOI Listing
August 2018

Disruption of the Microglial ADP Receptor P2Y Enhances Adult Hippocampal Neurogenesis.

Front Cell Neurosci 2018 17;12:134. Epub 2018 May 17.

Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences, Goethe-University, Frankfurt am Main, Germany.

In mammalian species, including humans, the hippocampal dentate gyrus (DG) is a primary region of adult neurogenesis. Aberrant adult hippocampal neurogenesis is associated with neurological pathologies. Understanding the cellular mechanisms controlling adult hippocampal neurogenesis is expected to open new therapeutic strategies for mental disorders. Microglia is intimately associated with neural progenitor cells in the hippocampal DG and has been implicated, under varying experimental conditions, in the control of the proliferation, differentiation and survival of neural precursor cells. But the underlying mechanisms remain poorly defined. Using fluorescent hybridization we show that microglia in brain express the ADP-activated P2Y receptor under basal conditions and that mRNA is absent from neurons, astrocytes, and neural progenitor cells. Disrupting decreases structural complexity of microglia in the hippocampal subgranular zone (SGZ). But it increases progenitor cell proliferation and new neuron formation. Our data suggest that P2Y receptor-activated microglia constitutively attenuate hippocampal neurogenesis. This identifies a signaling pathway whereby microglia, via a nucleotide-mediated mechanism, contribute to the homeostatic control of adult hippocampal neurogenesis. Selective P2YR antagonists could boost neurogenesis in pathological conditions associated with impaired hippocampal neurogenesis.
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http://dx.doi.org/10.3389/fncel.2018.00134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5966569PMC
May 2018

PHD3 Controls Lung Cancer Metastasis and Resistance to EGFR Inhibitors through TGFα.

Cancer Res 2018 04 16;78(7):1805-1819. Epub 2018 Jan 16.

Institute of Neuropathology, University of Giessen, Giessen, Germany.

Lung cancer is the leading cause of cancer-related death worldwide, in large part due to its high propensity to metastasize and to develop therapy resistance. Adaptive responses to hypoxia and epithelial-mesenchymal transition (EMT) are linked to tumor metastasis and drug resistance, but little is known about how oxygen sensing and EMT intersect to control these hallmarks of cancer. Here, we show that the oxygen sensor PHD3 links hypoxic signaling and EMT regulation in the lung tumor microenvironment. PHD3 was repressed by signals that induce EMT and acted as a negative regulator of EMT, metastasis, and therapeutic resistance. PHD3 depletion in tumors, which can be caused by the EMT inducer TGFβ or by promoter methylation, enhanced EMT and spontaneous metastasis via HIF-dependent upregulation of the EGFR ligand TGFα. In turn, TGFα stimulated EGFR, which potentiated SMAD signaling, reinforcing EMT and metastasis. In clinical specimens of lung cancer, reduced PHD3 expression was linked to poor prognosis and to therapeutic resistance against EGFR inhibitors such as erlotinib. Reexpression of PHD3 in lung cancer cells suppressed EMT and metastasis and restored sensitivity to erlotinib. Taken together, our results establish a key function for PHD3 in metastasis and drug resistance and suggest opportunities to improve patient treatment by interfering with the feedforward signaling mechanisms activated by PHD3 silencing. This study links the oxygen sensor PHD3 to metastasis and drug resistance in cancer, with implications for therapeutic improvement by targeting this system. .
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http://dx.doi.org/10.1158/0008-5472.CAN-17-1346DOI Listing
April 2018

Aβ42 oligomers impair the bioenergetic activity in hippocampal synaptosomes derived from APP-KO mice.

Biol Chem 2018 04;399(5):453-465

Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences (BMLS), University of Frankfurt, Max-von-Laue-Str. 15, D-60438, Frankfurt/Main, Germany.

Employing hippocampal synaptosomes from amyloid precursor protein (APP)-deleted mice we analyzed the immediate effects of amyloid beta peptide 42 (Aβ42) peptide in its oligomeric or fibrillar assembly or of soluble amyloid precursor protein alpha (sAPPα) protein on their bioenergetic activity. Upon administration of oligomeric Aβ42 peptide for 30 min we observed a robust decrease both in mitochondrial activity and in mitochondrial membrane potential (MMP). In contrast the respective fibrillary or scrambled peptides showed no effect, indicating that inhibition strictly depends on the oligomerization status of the peptide. Hippocampal synaptosomes from old APP-KO mice revealed a further reduction of their already impaired bioenergetic activity upon incubation with 10 μm Aβ42 peptide. In addition we evaluated the influence of the sAPPα protein on mitochondrial activity of hippocampal synaptosomes derived from young or old APP-KO animals. In neither case 20 nm nor 200 nm sAPPα protein had an effect on mitochondrial metabolic activity. Our findings demonstrate that hippocampal synaptosomes derived from APP-KO mice are a most suitable model system to evaluate the impact of Aβ42 peptide on its bioenergetic activity and to further elucidate the molecular mechanisms underlying the impairments by oligomeric Aβ42 on mitochondrial function. Our data demonstrate that extracellular Aβ42 peptide is taken up into synaptosomes where it immediately attenuates mitochondrial activity.
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http://dx.doi.org/10.1515/hsz-2017-0238DOI Listing
April 2018

GRIP1 Binds to ApoER2 and EphrinB2 to Induce Activity-Dependent AMPA Receptor Insertion at the Synapse.

Cell Rep 2017 Oct;21(1):84-96

Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences (BMLS), University of Frankfurt, Max-von-Laue-Str. 15, 60438 Frankfurt am Main, Germany; Focus Program Translational Neurosciences (FTN), University of Mainz, Langenbeckstr. 1, 55131 Mainz, Germany; Max Planck Institute for Brain Research, Max von Laue Str. 4, 60438 Frankfurt am Main, Germany. Electronic address:

Regulation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor trafficking in response to neuronal activity is critical for synaptic function and plasticity. Here, we show that neuronal activity induces the binding of ephrinB2 and ApoER2 receptors at the postsynapse to regulate de novo insertion of AMPA receptors. Mechanistically, the multi-PDZ adaptor glutamate-receptor-interacting protein 1 (GRIP1) binds ApoER2 and bridges a complex including ApoER2, ephrinB2, and AMPA receptors. Phosphorylation of ephrinB2 in a serine residue (Ser-9) is essential for the stability of such a complex. In vivo, a mutation on ephrinB2 Ser-9 in mice results in a complete disruption of the complex, absence of ApoER2 downstream signaling, and impaired activity-induced and ApoER2-mediated AMPA receptor insertion. Using compound genetics, we show the requirement of this complex for long-term potentiation (LTP). Together, our findings uncover a cooperative ephrinB2 and ApoER2 signaling at the synapse, which serves to modulate activity-dependent AMPA receptor dynamic changes during synaptic plasticity.
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http://dx.doi.org/10.1016/j.celrep.2017.09.019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5640806PMC
October 2017

Erratum to: Antibody-mediated neutralization of myelin-associated EphrinB3 accelerates CNS remyelination.

Acta Neuropathol 2017 07;134(1):167-168

Wellcome Trust and MRC Cambridge Stem Cell Institute, Department of Clinical Neurosciences, Anne McLaren Laboratory, University of Cambridge, Cambridge, CB2 0SZ, UK.

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http://dx.doi.org/10.1007/s00401-017-1712-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6828333PMC
July 2017

APP Deletion Accounts for Age-Dependent Changes in the Bioenergetic Metabolism and in Hyperphosphorylated CaMKII at Stimulated Hippocampal Presynaptic Active Zones.

Front Synaptic Neurosci 2017 20;9. Epub 2017 Jan 20.

Institute for Cell Biology and Neuroscience, Biologicum and BMLS, Johann Wolfgang Goethe-Universität Frankfurt, Germany.

Synaptic release sites are characterized by exocytosis-competent synaptic vesicles tightly anchored to the presynaptic active zone (PAZ) whose proteome orchestrates the fast signaling events involved in synaptic vesicle cycle and plasticity. Allocation of the amyloid precursor protein (APP) to the PAZ proteome implicated a functional impact of APP in neuronal communication. In this study, we combined state-of-the-art proteomics, electrophysiology and bioinformatics to address protein abundance and functional changes at the native hippocampal PAZ in young and old APP-KO mice. We evaluated if APP deletion has an impact on the metabolic activity of presynaptic mitochondria. Furthermore, we quantified differences in the phosphorylation status after long-term-potentiation (LTP) induction at the purified native PAZ. We observed an increase in the phosphorylation of the signaling enzyme calmodulin-dependent kinase II (CaMKII) only in old APP-KO mice. During aging APP deletion is accompanied by a severe decrease in metabolic activity and hyperphosphorylation of CaMKII. This attributes an essential functional role to APP at hippocampal PAZ and putative molecular mechanisms underlying the age-dependent impairments in learning and memory in APP-KO mice.
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http://dx.doi.org/10.3389/fnsyn.2017.00001DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5247443PMC
January 2017

FAM222B Is Not a Likely Novel Candidate Gene for Cerebral Cavernous Malformations.

Mol Syndromol 2016 Jul 18;7(3):144-52. Epub 2016 Jun 18.

Department of Human Genetics, University Medicine Greifswald and Interfaculty Institute of Genetics and Functional Genomics, University of Greifswald, Greifswald, Germany.

Cerebral cavernous malformations (CCMs) are prevalent slow-flow vascular lesions which harbour the risk to develop intracranial haemorrhages, focal neurological deficits, and epileptic seizures. Autosomal dominantly inherited CCMs were found to be associated with heterozygous inactivating mutations in 3 genes, CCM1 (KRIT1), CCM2 (MGC4607), and CCM3 (PDCD10) in 1999, 2003 and 2005, respectively. Despite the availability of high-throughput sequencing techniques, no further CCM gene has been published since. Here, we report on the identification of an autosomal dominantly inherited frameshift mutation in a gene of thus far unknown function, FAM222B (C17orf63), through exome sequencing of CCM patients mutation-negative for CCM1-3. A yeast 2-hybrid screen revealed interactions of FAM222B with the tubulin cytoskeleton and STAMBP which is known to be associated with microcephaly-capillary malformation syndrome. However, a phenotype similar to existing models was not found, neither in fam222bb/fam222ba double mutant zebrafish generated by transcription activator-like effector nucleases nor in an in vitro sprouting assay using human umbilical vein endothelial cells transfected with siRNA against FAM222B. These observations led to the assumption that aberrant FAM222B is not involved in the formation of CCMs.
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http://dx.doi.org/10.1159/000446884DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4988258PMC
July 2016

APP Is a Context-Sensitive Regulator of the Hippocampal Presynaptic Active Zone.

PLoS Comput Biol 2016 Apr 19;12(4):e1004832. Epub 2016 Apr 19.

Institute for Cell Biology and Neuroscience, Biologicum, Johann Wolfgang Goethe-University, Frankfurt am Main, Germany.

The hallmarks of Alzheimer's disease (AD) are characterized by cognitive decline and behavioral changes. The most prominent brain region affected by the progression of AD is the hippocampal formation. The pathogenesis involves a successive loss of hippocampal neurons accompanied by a decline in learning and memory consolidation mainly attributed to an accumulation of senile plaques. The amyloid precursor protein (APP) has been identified as precursor of Aβ-peptides, the main constituents of senile plaques. Until now, little is known about the physiological function of APP within the central nervous system. The allocation of APP to the proteome of the highly dynamic presynaptic active zone (PAZ) highlights APP as a yet unknown player in neuronal communication and signaling. In this study, we analyze the impact of APP deletion on the hippocampal PAZ proteome. The native hippocampal PAZ derived from APP mouse mutants (APP-KOs and NexCreAPP/APLP2-cDKOs) was isolated by subcellular fractionation and immunopurification. Subsequently, an isobaric labeling was performed using TMT6 for protein identification and quantification by high-resolution mass spectrometry. We combine bioinformatics tools and biochemical approaches to address the proteomics dataset and to understand the role of individual proteins. The impact of APP deletion on the hippocampal PAZ proteome was visualized by creating protein-protein interaction (PPI) networks that incorporated APP into the synaptic vesicle cycle, cytoskeletal organization, and calcium-homeostasis. The combination of subcellular fractionation, immunopurification, proteomic analysis, and bioinformatics allowed us to identify APP as structural and functional regulator in a context-sensitive manner within the hippocampal active zone network.
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http://dx.doi.org/10.1371/journal.pcbi.1004832DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4836664PMC
April 2016

Antibody-mediated neutralization of myelin-associated EphrinB3 accelerates CNS remyelination.

Acta Neuropathol 2016 02 19;131(2):281-298. Epub 2015 Dec 19.

Wellcome Trust and MRC Cambridge Stem Cell Institute, Department of Clinical Neurosciences, Anne McLaren Laboratory, University of Cambridge, Cambridge, CB2 0SZ, UK.

Remyelination in multiple sclerosis (MS) lesions often remains incomplete despite the presence of oligodendrocyte progenitor cells (OPCs). Amongst other factors, successful remyelination depends on the phagocytic clearance of myelin debris. However, the proteins in myelin debris that act as potent and selective inhibitors on OPC differentiation and inhibit CNS remyelination remain unknown. Here, we identify the transmembrane signalling protein EphrinB3 as important mediator of this inhibition, using a protein analytical approach in combination with a primary rodent OPC assay. In the presence of EphrinB3, OPCs fail to differentiate. In a rat model of remyelination, infusion of EphrinB3 inhibits remyelination. In contrast, masking EphrinB3 epitopes using antibodies promotes remyelination. Finally, we identify EphrinB3 in MS lesions and demonstrate that MS lesion extracts inhibit OPC differentiation while antibody-mediated masking of EphrinB3 epitopes promotes it. Our findings suggest that EphrinB3 could be a target for therapies aiming at promoting remyelination in demyelinating disease.
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http://dx.doi.org/10.1007/s00401-015-1521-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4713754PMC
February 2016

Measurement of ROS Levels and Membrane Potential Dynamics in the Intact Carotid Body Ex Vivo.

Adv Exp Med Biol 2015 ;860:55-9

Institute of Physiology, University of Duisburg-Essen, Hufelandstr. 55, 45122, Essen, Germany,

Reactive oxygen species (ROS) generated by the NADPH oxidase have been proposed to play an important role in the carotid body (CB) oxygen sensing process (Cross et al. 1990). Up to now it remains unclear whether hypoxia causes an increase or decrease of CB ROS levels. We transfected CBs with the ROS sensitive HSP-FRET construct and subsequently measured the intracellular redox state by means of Förster resonance energy transfer (FRET) microscopy. In a previous study we found both increasing and decreasing ROS levels under hypoxic conditions. The transition from decreasing to increasing ROS levels coincided with the change of the caging system from ambient environment caging (AEC) to individually ventilated caging (IVC) (Bernardini A, Brockmeier U, Metzen E, Berchner-Pfannschmidt U, Harde E, Acker-Palmer A, Papkovsky D, Acker H, Fandrey J, Type I cell ROS kinetics under hypoxia in the intact mouse carotid body ex vivo: a FRET based study. Am J Physiol Cell Physiol. doi: 10.1152/ajpcell.00370.2013 , 2014). In this work we analyze hypoxia induced ROS reaction of animals from an IVC system that had been exposed to AEC conditions for 5 days. The results further support the hypothesis of an important impact of the caging system on CB ROS reaction.
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http://dx.doi.org/10.1007/978-3-319-18440-1_7DOI Listing
January 2016

14-3-3ζ coordinates adipogenesis of visceral fat.

Nat Commun 2015 Jul 29;6:7671. Epub 2015 Jul 29.

Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3.

The proteins that coordinate complex adipogenic transcriptional networks are poorly understood. 14-3-3ζ is a molecular adaptor protein that regulates insulin signalling and transcription factor networks. Here we report that 14-3-3ζ-knockout mice are strikingly lean from birth with specific reductions in visceral fat depots. Conversely, transgenic 14-3-3ζ overexpression potentiates obesity, without exacerbating metabolic complications. Only the 14-3-3ζ isoform is essential for adipogenesis based on isoform-specific RNAi. Mechanistic studies show that 14-3-3ζ depletion promotes autophagy-dependent degradation of C/EBP-δ, preventing induction of the master adipogenic factors, Pparγ and C/EBP-α. Transcriptomic data indicate that 14-3-3ζ acts upstream of hedgehog signalling-dependent upregulation of Cdkn1b/p27(Kip1). Indeed, concomitant knockdown of p27(Kip1) or Gli3 rescues the early block in adipogenesis induced by 14-3-3ζ knockdown in vitro. Adipocyte precursors in 14-3-3ζKO embryos also appear to have greater Gli3 and p27(Kip1) abundance. Together, our in vivo and in vitro findings demonstrate that 14-3-3ζ is a critical upstream driver of adipogenesis.
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http://dx.doi.org/10.1038/ncomms8671DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4532800PMC
July 2015

A vascular perspective on neuronal migration.

Mech Dev 2015 Nov 17;138 Pt 1:17-25. Epub 2015 Jul 17.

Institute of Cell Biology and Neuroscience and Buchmann Institute for Molecular Life Sciences (BMLS), University of Frankfurt, Germany; Focus Program Translational Neurosciences (FTN), University of Mainz, Germany; Max Planck Institute for Brain Research, Frankfurt, Germany. Electronic address:

During CNS development and adult neurogenesis, immature neurons travel from the germinal zones towards their final destination using cellular substrates for their migration. Classically, radial glia and neuronal axons have been shown to act as physical scaffolds to support neuroblast locomotion in processes known as gliophilic and neurophilic migration, respectively (Hatten, 1999; Marin and Rubenstein, 2003; Rakic, 2003). In adulthood, long distance neuronal migration occurs in a glial-independent manner since radial glia cells differentiate into astrocytes after birth. A series of studies highlight a novel mode of neuronal migration that uses blood vessels as scaffolds, the so-called vasophilic migration. This migration mode allows neuroblast navigation in physiological and also pathological conditions, such as neuronal precursor migration after ischemic stroke or cerebral invasion of glioma tumor cells. Here we review the current knowledge about how vessels pave the path for migrating neurons and how trophic factors derived by glio-vascular structures guide neuronal migration both during physiological as well as pathological processes.
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http://dx.doi.org/10.1016/j.mod.2015.07.004DOI Listing
November 2015

Regional Specializations of the PAZ Proteomes Derived from Mouse Hippocampus, Olfactory Bulb and Cerebellum.

Proteomes 2015 May 13;3(2):74-88. Epub 2015 May 13.

These authors contributed equally to this work..

Neurotransmitter release as well as structural and functional dynamics at the presynaptic active zone (PAZ) comprising synaptic vesicles attached to the presynaptic plasma membrane are mediated and controlled by its proteinaceous components. Here we describe a novel experimental design to immunopurify the native PAZ-complex from individual mouse brain regions such as olfactory bulb, hippocampus, and cerebellum with high purity that is essential for comparing their proteome composition. Interestingly, quantitative immunodetection demonstrates significant differences in the abundance of prominent calcium-dependent PAZ constituents. Furthermore, we characterized the proteomes of the immunoisolated PAZ derived from the three brain regions by mass spectrometry. The proteomes of the release sites from the respective regions exhibited remarkable differences in the abundance of a large variety of PAZ constituents involved in various functional aspects of the release sites such as calcium homeostasis, synaptic plasticity and neurogenesis. On the one hand, our data support an identical core architecture of the PAZ for all brain regions and, on the other hand, demonstrate that the proteinaceous composition of their presynaptic active zones vary, suggesting that changes in abundance of individual proteins strengthen the ability of the release sites to adapt to specific functional requirements.
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http://dx.doi.org/10.3390/proteomes3020074DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5217373PMC
May 2015

EphrinB2 controls vessel pruning through STAT1-JNK3 signalling.

Nat Commun 2015 Mar 26;6:6576. Epub 2015 Mar 26.

Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda Maryland 20892, USA.

Angiogenesis produces primitive vascular networks that need pruning to yield hierarchically organized and functional vessels. Despite the critical importance of vessel pruning to vessel patterning and function, the mechanisms regulating this process are not clear. Here we show that EphrinB2, a well-known player in angiogenesis, is an essential regulator of endothelial cell death and vessel pruning. This regulation depends upon phosphotyrosine-EphrinB2 signalling repressing c-jun N-terminal kinase 3 activity via STAT1. JNK3 activation causes endothelial cell death. In the absence of JNK3, hyaloid vessel physiological pruning is impaired, associated with abnormal persistence of hyaloid vessels, defective retinal vasculature and microphthalmia. This syndrome closely resembles human persistent hyperplastic primary vitreus (PHPV), attributed to failed involution of hyaloid vessels. Our results provide evidence that EphrinB2/STAT1/JNK3 signalling is essential for vessel pruning, and that defects in this pathway may contribute to PHPV.
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http://dx.doi.org/10.1038/ncomms7576DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4377839PMC
March 2015
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