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Synj 1 modulates functional recovery after motor-incomplete spinal cord injury in male mice carriers of human ApoE4.

ABSTRACT: Apolipoprotein E epsilon 4 (ApoE4) is the second most common variant of ApoE, being present in ~14% of population. Clinical reports identify ApoE4 as a genetic risk factor for poor outcomes after traumatic SCI and the spinal cord disease (SCD) cervical myelopathy. To date, there are no interventions to mitigate the potent effects of ApoE4 to reduce recovery of function after SCI/D. Studies in human and mouse brain link ApoE4 to elevated levels of synaptojanin 1 (synj1), a lipid phosphatase that dephosphorylates phosphoinositol 4,5-bisphosphate (PIP2) to inositol 4-monophosphate (PIP1). Synj1 regulates rearrangements of the cytoskeleton and the endocytosis and trafficking of synaptic vesicles. We report here that, as compared to ApoE3 mice, levels of synj1 mRNA and protein were elevated in spinal cords from healthy ApoE4 mice associated with lower PIP2 levels. Using a moderate severity model of contusion SCI in mice, we found that genetic reduction of syn1 improved locomotor function recovery at 14 days after SCI in ApoE4 mice without altering spared white matter. Genetic reduction of synj1 did not alter locomotor recover of ApoE3 mice after SCI. Bulk RNA-sequencing revealed that at 14 days after SCI in ApoE4 mice, genetic reduction of synj1 upregulated genes involved in glutaminergic synaptic transmission just above and below the lesion. Overall, our findings provide evidence for a link between synj1 to poor outcomes after SCI in ApoE4 mice through mechanisms that remain speculative but may include greater function of excitatory glutaminergic synapses.

ORGANISM(S): Mus musculus

PROVIDER: GSE227291 | GEO | 2023/08/09

REPOSITORIES: GEO

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The human ApoE4 variant reduces functional recovery and neuronal sprouting after incomplete spinal injury in male mice

Project description:Patients carrying one or two ApoE4 alleles suffer from worse functional recovery after spinal cord injury. Using transgenic mice expression human ApoE3 or ApoE4 we investigated potential cellular mechanisms of reduced recovery after spinal cord injury. Bulk RNA sequencing of the spinal cord lesion site followed by pathway enrichment analysis predicts that ApoE4 mice have a higher inflammatory and extracellular matrix remodeling activity 7 days after spinal cord injury. Contrary, higher activities for neuronal projection and action potential patways were predicted in the ApoE3 mice at 21 days after injury.

2021-02-05 | GSE164688 | GEO

A SAGE approach to discovery of apolipoprotein E4 allele-specific genes involved in increased risk in Alzheimer disease

Project description:APOE4 allele is a major risk factor for late-onset Alzheimer disease (AD). The mechanism of action of APOE in AD remains unclear. To study the effects of APOE alleles on gene expression in AD, we have analyzed the gene transcription patterns of human hippocampus from APOE3/3, APOE3/4, APOE4/4 AD patients and normal control using Serial Analysis of Gene Expression (SAGE). Using SAGE, we found gene expression patterns in hippocampus of APOE3/4 and APOE4/4 AD patients differ substantially from those of APOE3/3 AD patients. APOE3/4 and APOE4/4 allele expression may activate similar genes or gene pools with associated functions. APOE4 AD alleles activate multiple tumor suppressors, tumor inducers and negative regulator of cell growth or repressors that may lead to increased cell arrest, senescent and apoptosis. In contrast, there is decreased expression of large clusters of genes associated with synaptic plasticity, synaptic vesicle trafficking (metabolism) and axonal/neuronal outgrowth. In addition, reduction of neurotransmitter receptors and Ca++ homeostasis, disruption of multiple signal transduction pathways, and loss of cell protection and notably mitochondrial oxidative phosphorylation/energy metabolism are associated with APOE3/4 and APOE4/4 AD alleles. These findings help define the mechanisms that APOE4 contribute increased risk for AD and identify new candidate genes conferring susceptibility to AD. Keywords: Serial Analysis of Gene Expression (SAGE); Apolipoprotein E (APOE3/3, APOE3/4, APOE4/4); Alzheimer disease; Hippocampus; apoptosis; signal pathways

2007-01-13 | GSE6677 | GEO

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2023-08-31 | GSE206314 | GEO

Differential gene expression in APOE3 and APOE4 gene targeted replacement mice

Project description:The aim of the study was to investigate hepatic gene expression profiles differentially regulated by the APOE genotype in gene targeted replacement mice. The APOE4 genotype is associated with increased mortality in the elderly and is an independent risk factor for age-dependent chronic diseases. However, little is known about the underlying mechanisms and molecular targets involved in the APOE4-risk association. As APOE is centrally involved in lipid and cholesterol metabolism and in large part is produced in the liver, we analyzed hepatic RNA profiles of APOE4- and APOE3-expressing mice. 2 groups of 5 animals with 1 liver extract per animal. Mice were homozygous for a human APOE3 or APOE4 gene targeted replacement of the endogenous mouse Apoe gene (B6.129P2-Apoetm2(APOE*3)Mae N8 or B6.129P2-Apoetm3(APOE*4)Mae N8, Taconic Transgenic ModelsM-bM-^DM-", http://www.taconic.com/wmspage.cfm?parm1=2542), purchased at the age of 6-8 weeks, strain C57BL/6, 3 months old at the performance of the microarray, 6 weeks on a high-fat diet containing 41% energy from milk fat and 2 g/kg cholesterol.

2012-12-15 | E-GEOD-42930 | biostudies-arrayexpress

Gene expression profiles in the spinal cord below the lesion level and influence of treadmill locomotor training

Project description:Traumatic spinal cord injury (SCI) often leads to loss of locomotor function. Neuroplasticity of spinal circuitry underlies some functional recovery and therefore represents a therapeutic target to improve locomotor function following SCI. However, the cellular and molecular mechanisms mediating neuroplasticity below the lesion level are not fully understood. The present study performed a gene expression profiling in the rat lumbar spinal cord at 1 and 3 weeks after contusive SCI at T9 compared to control rat that received sham injury (laminectomy). The below-level gene expression profiles were compared with those of animals that were subjected to treadmill locomotor training. Rat lumbar spinal cords were taken for the microarray analysis at 1 and 3 weeks after contusive spinal cord injury at the T9 level. Another group of rats received treadmill locomotor training for 3 weeks, and theirs spinal cords were harvested for the microarray. The changes in gene expression after spinal cord injury were analyzed at the two time points. The influence of treadmill locomotor training was evaluated by comparing gene expression profiles between animals with or without treadmill training.

2013-11-27 | E-GEOD-52763 | biostudies-arrayexpress

Peripherally-expressed apoE4 impairs brain functions and exacerbates amyloid pathogenesis by compromising cerebrovascular functions

Project description:The apolipoprotein E4 (APOE4) gene is the strongest genetic risk factor for late-onset Alzheimer’s disease (AD). ApoE is a lipid carrier abundantly expressed in both brain and periphery. As peripheral apoE is separated from brain apoE by the blood-brain barrier, it remains unclear whether peripheral apoE impacts brain functions and AD pathogenesis. To investigate this, we developed novel mouse models that conditionally express human APOE3 or APOE4 only in the liver with no detectable apoE in the brain. We found that liver-expressed apoE4 compromised synaptic plasticity and cognitive behaviors likely by impairing cerebrovascular functions. Remarkably, liver-expressed apoE4 exacerbated brain amyloid pathology, whereas apoE3 reduced it. Our findings demonstrate a pathogenic effect of peripheral apoE4, providing strong rationale for targeting peripheral apoE to treat AD.

2022-06-15 | GSE125501 | GEO

Quantitative proteomic analysis reveals apoE4-dependent phosphorylation of the actin regulating protein VASP

Project description:Apolipoprotein (apo) E4 is the major genetic risk factor for Alzheimer’s Disease (AD). While neurons generally produce a minority of the apoE in the central nervous system, neuronal expression of apoE increases dramatically in response to stress and is sufficient to drive pathology. Currently, the molecular mechanisms of how apoE4 expression may regulate pathology are not fully understood. Here we expand upon our previous studies measuring the impact of apoE4 on protein abundance to include the analysis of protein phosphorylation and ubiquitylation signaling in isogenic Neuro-2a cells expressing apoE3 or apoE4. We find that apoE4 expression results in the dramatic increase in VASP S235 phosphorylation in a PKA-dependent manner. This phosphorylation results in the loss of VASP interactions with numerous actin cytoskeletal and microtubular proteins. Reduction of VASP S235 phosphorylation via PKA inhibition results in a significant increase in filopodia formation and neurite outgrowth in apoE4-expressing cells to levels beyond that of apoE3. Our results highlight the pronounced and diverse impact of apoE4 on multiple modes of protein regulation and identify potential therapeutic targets to restore apoE4-related cytoskeletal defects.

2023-04-08 | PXD041205 | Pride

APOE4 Causes Widespread Molecular and Cellular Alterations Associated with Alzheimer's Disease Phenotypes in Human iPSC-Derived Brain Cell Types

Project description:The apolipoprotein E4 (APOE4) variant is the single greatest genetic risk factor for sporadic Alzheimer's disease (sAD). However, the cell-type-specific functions of APOE4 in relation to AD pathology remain understudied. Here, we utilize CRISPR/Cas9 and induced pluripotent stem cells (iPSCs) to examine APOE4 effects on human brain cell types. Transcriptional profiling identified hundreds of differentially expressed genes in each cell type, with the most affected involving synaptic function (neurons), lipid metabolism (astrocytes), and immune response (microglia-like cells). APOE4 neurons exhibited increased synapse number and elevated Ab42 secretion relative to isogenic APOE3 cells while APOE4 astrocytes displayed impaired Ab uptake and cholesterol accumulation. Notably, APOE4 microglia-like cells exhibited altered morphologies, which correlated with reduced Ab phagocytosis. Consistently, converting APOE4 to APOE3 in brain cell types from sAD iPSCs was sufficient to attenuate multiple AD-related pathologies. Our study establishes a reference for human cell-type-specific changes associated with the APOE4 variant.

2018-05-31 | GSE102956 | GEO

Differential gene expression following SCI in trkB.T1 null

Project description:We asked what genes are significantly differentially regulated in the spinal cord of SCI trkB.T1 WT and trkB.T1 KO mice. TrkB.T1 is upregulated shortly after SCI although the precise mechanisms underyling this upregulation are poorly understood. In the trkB.T1 null, we show less mechanical allodynia and better locomotor recovery following SCI. The microarray studies helped us to elucidate a signaling pathway that is differently regulated in the WT versus KO mice at 1 day after SCI. In this study, we did not examine gene changes within a genotype after SCI. Rather, we examined DGE by genotype at each time point. Spinal cord tissue from WT and KO mice in a sham condition (intact spinal cord) versus 1D, 3D and 7D following SCI was harvested for microarray analyses.

2015-12-07 | E-GEOD-42828 | biostudies-arrayexpress

Gene expression profiles in the spinal cord below the lesion level and influence of treadmill locomotor training

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