Astrocytic EphA4 signaling is important for the elimination of excitatory synapses in Alzheimer’s disease
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PROVIDER: PRJNA1203656 | ENA |
REPOSITORIES: ENA
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Project description:Cell surface receptors, including erythropoietin-producing hepatocellular A4 (EphA4), are important in regulating hippocampal synapse loss, which is the key driver of memory decline in Alzheimer’s disease (AD). However, the cellular-specific roles and mechanisms of EphA4 are unclear. Here, we show that EphA4 expression is elevated in hippocampal CA1 astrocytes in AD conditions. Specific knockout of astrocytic EphA4 ameliorates excitatory synapse loss in the hippocampus in AD transgenic mouse models. Single-nucleus RNA sequencing analysis revealed that EphA4 inhibition specifically decreases a reactive astrocyte subpopulation with enriched complement signaling, which are characteristics associated with synapse elimination by astrocytes in AD. Importantly, astrocytic EphA4 knockout in an AD transgenic mouse model decreases complement tagging on excitatory synapses and excitatory synapses within astrocytes. These findings suggest an important role of EphA4 in the astrocyte-mediated elimination of excitatory synapses in AD and highlight the crucial role of astrocytes in hippocampal synapse maintenance in AD.
2024-12-29 | GSE284797 | GEO
Project description:Excitatory synapses occur mainly on dendritic spines, and spine density is usually correlated with the strength of excitatory synaptic transmission. We report that Nr4a1, an activity-inducible gene encoding a nuclear receptor, regulates the density and distribution of dendritic spines in CA1 pyramidal neurons. Nr4a1 overexpression resulted in elimination of the majority of spines; however, postsynaptic densities were preserved on dendritic shafts, and the strength of excitatory synaptic transmission was unaffected, showing that excitatory synapses can be dissociated from spines. mRNA expression profiling studies suggest that Nr4a1-mediated transcriptional regulation of the actin cytoskeleton contributes to this effect. Under conditions of chronically elevated activity, when Nr4a1 was induced, Nr4a1 knockdown increased the density of spines and PSDs specifically at the distal ends of dendrites. Thus, Nr4a1 is a key component of an activity-induced transcriptional program that regulates the density and distribution of spines and synapses. After 10 days in culture, dissociated mouse hippocampal neurons in 6-well plates were infected with lentivirus expressing either Flag-Nr4a1 or GFP and incubated for 6 days to allow for transgene expression. Total RNA was then isolated using RNeasy Plus kit (QIAGEN). Samples passing an mRNA quality check proceeded to quantitative analysis on Agilent-026655 4x44 Mouse Microarrays.
2016-01-13 | E-GEOD-76805 | biostudies-arrayexpress
Project description:Excitatory synapses occur mainly on dendritic spines, and spine density is usually correlated with the strength of excitatory synaptic transmission. We report that Nr4a1, an activity-inducible gene encoding a nuclear receptor, regulates the density and distribution of dendritic spines in CA1 pyramidal neurons. Nr4a1 overexpression resulted in elimination of the majority of spines; however, postsynaptic densities were preserved on dendritic shafts, and the strength of excitatory synaptic transmission was unaffected, showing that excitatory synapses can be dissociated from spines. mRNA expression profiling studies suggest that Nr4a1-mediated transcriptional regulation of the actin cytoskeleton contributes to this effect. Under conditions of chronically elevated activity, when Nr4a1 was induced, Nr4a1 knockdown increased the density of spines and PSDs specifically at the distal ends of dendrites. Thus, Nr4a1 is a key component of an activity-induced transcriptional program that regulates the density and distribution of spines and synapses.
2016-01-13 | GSE76805 | GEO
Project description:Synapse loss and glial activation are hallmarks of Alzheimer's disease (AD). In Tau P301S transgenic mice, the complement pathway contributes to neuronal damage through microglial elimination of synapses. Here, we used unbiased proteomic profiling of postsynaptic density (PSD) fractions from Tau P301S mice in C1q-WT versus C1q knockout backgrounds to identify C1q-dependent changes at synapses. Integrative multi-omics analysis revealed that astrocyte- and microglia- specific proteins are increased in Tau P301S synapse fractions with age and in a C1q-dependent manner. The same set of glial proteins (including C1q, C4, Gpnmb, and S100a4) is elevated in human AD synaptic fractions, and C4 levels are raised in cerebrospinal fluid (CSF) from AD patients. Besides microglia, we show that astrocytes contribute substantially to excitatory and inhibitory synapse engulfment in Tau P301S hippocampus. Based on staining of synapse markers within lysosomes, astrocytes showed preference for excitatory synapses whereas microglia preferred to engulf inhibitory synapse markers. Genetic deletion of C1q reduced astrocytic eating of excitatory and inhibitory synapses in Tau P301S mice, and rescued synapse density. Together, our data indicate that astrocytes contact and phagocytose synapses in a C1q- dependent manner and thereby contribute to synapse loss and neurodegeneration in AD.
2021-11-03 | MSV000088313 | MassIVE
Project description:ADGRB1 contributes to astrocyte-mediated phagocytosis of excitatory synapses
| PRJNA1073438 | ENA
Project description:The phagocytic activity of astrocytes plays an important role in synapse refinement through the elimination of excess synapses during brain development. The adhesion G protein-coupled receptor BAI1/ADGRB1 contributes to phagocytosis in various tissues, including the clearance of apoptotic myoblasts in skeletal muscle and epithelial cells in the intestine. However, the phagocytic function of ADGRB1 in the brain has not been thoroughly investigated. Given that Adgrb1 is highly expressed in astrocytes but not in microglia, we examined changes in astrocyte gene expression resulting from the loss of ADGRB1. RNA-seq analysis revealed that astrocytes lacking ADGRB1 exhibit altered expression of genes associated with cytoskeleton organization and chemotaxis, processes that are required for phagocytosis. Using cultured astrocytes from mice lacking full-length ADGRB1 (Adgrb1exon2-/-) and wildtype (WT) littermates, we found that Adgrb1exon2-/- astrocytes exhibit significantly reduced phagocytic capacity when compared to similarly prepared astrocytes from WT littermates. Immunostaining of astrocytes and pre-synaptic markers showed less engulfed pre-synaptic elements in astrocytes from Adgrb1exon2-/- mutants. Finally, immunostaining of pre-synaptic and post synaptic markers revealed a significantly higher density of excitatory synapses in Adgrb1exon2-/- mutants. These findings highlight the importance of ADGRB1 in synaptic remodeling and raise the possibility that reduced astrocyte-mediated phagocytosis might underlie the behavioral alterations previously observed in Adgrb1exon2-/- mutants, including increased seizure susceptibility and deficits in social memory.
2024-03-19 | GSE255050 | GEO
Project description:CRISPR-TRAPSeq identifies the QKI RNA binding protein as important for astrocytic maturation and control of thalamocortical synapses
| PRJNA613058 | ENA
Project description:The autism-associated synaptic-adhesion gene Neuroligin-4 (NLGN4) is poorly conserved evolutionarily, limiting conclusions from Nlgn4 mouse models for human cells. Here, we show that the cellular and subcellular expression of human and murine Neuroligin-4 differ, with human Neuroligin-4 primarily expressed in cerebral cortex and localized to excitatory synapses. Overexpression of NLGN4 in human neurons resulted in an increase in excitatory synapse numbers but a remarkable decrease in synaptic strength. Human neurons carrying the syndromic autism mutation NLGN4-R704C also formed more excitatory synapses but with increased functional synaptic transmission due to a postsynaptic mechanism, while genetic loss of NLGN4 did not significantly affect synapses in the human neurons analyzed. Thus, the NLGN4-R704C mutation represents a change of function mutation. Our work reveals contrasting roles of NLGN4 in human and mouse neurons, suggesting human evolution has impacted even fundamental cell biological processes generally assumed to be highly conserved.
2019-06-27 | GSE131428 | GEO
Project description:Homeostatic scaling is a global form of synaptic plasticity used by neurons to adjust overall synaptic weight and maintain neuronal firing rates while protecting information coding. While homeostatic scaling has been demonstrated in vitro, a clear physiological function of this plasticity type has not been defined. Sleep is an essential process that modifies synapses to support cognitive functions such as learning and memory. Evidence suggests that information coding during wake drives synapse strengthening which is offset by weakening of synapses during sleep .Here we use biochemical fractionation, proteomics and in vivo two-photon imaging to characterize wide-spread changes in synapse composition in mice through the wake/sleep cycle. We find that during the sleep phase, synapses are weakened through dephosphorylation and removal of synaptic AMPA-type glutamate receptors (AMPARs) driven by the immediate early gene Homer1a and signaling from group I metabotropic glutamate receptors (mGluR1/5), consistent with known mechanisms of homeostatic scaling-down in vitro. Further, we find that these changes are important in the consolidation of contextual memories. While Homer1a gene expression is driven by neuronal activity during wake, Homer1a protein targeting to synapses serves as an integrator of arousal and sleep need through signaling by the wake-promoting neuromodulator noradrenaline (NA) and sleep-promoting modulator adenosine. During sleep or periods of increased sleep need Homer1a enters synapses where it remodels mGluR1/5 signaling complexes to promote AMPAR removal. Thus, we have characterized widespread changes occurring at synapses through the wake/sleep cycle and demonstrated that known mechanisms of homeostatic scaling-down previously demonstrated only in vitro are active in the brain during sleep to remodel synapses, contributing to memory consolidation.
2017-02-13 | PXD004537 | Pride
Project description:CRISPR-TRAPSeq identifies the QKI RNA binding protein as important for astrocytic maturation and control of thalamocortical synapses (CLIP-Seq dataset)
| PRJNA613063 | ENA