Project description:This datased was used to obtain a genome-wide expression signature for the early response of mouse motor neurons to mutant SOD1 astrocytes conditioned media. Neurons, far from living in isolation, are surrounded by a host of other neuronal and non-neuronal cells, such as astrocytes. The latter entertain complex functional interactions with neighboring neurons, which, under normal conditions, are important for the their well-being. In pathological situations, however, altered astrocyte behavior may contribute to the demise of neighboring neurons. Such non-cell autonomous pathogenic scenario is increasingly considered in a variety of disorders, including amyotrophic lateral sclerosis (ALS), the most frequent adult-onset paralytic disorder. Assembly and interrogation of gene regulatory models has helped elucidate causal mechanisms responsible for the presentation of several tumor-related phenotypes. To systematically elucidate the effectors of neurodegeneration in a model of ALS, we first developed techniques for the efficient purification of motor neurons (MNs), the primary target of ALS neurodegenerative process. We then generated gene expression profiles to fully characterize the critical timepoints associated with initiation and commitment of MN degenerative progression in an in vitro murine mutant SOD1 (mSOD1) model of ALS. ES cells were derived from transgenic Hlxb9-GFP1Tmj mice expressing eGFP and CD2 driven by the mouse HB9 promoter. These cells were then differentiated into motor neurons (ES-MN) as described previously [PMID 12176325] ES-MN were exposed to non-transgenic (NTg), G93A mutant SOD1 (mSOD1) or wtSOD1 over-expression astrocytes conditioned media for 0 days (time zero control), 1 day, and 3 days. Total RNA was extracted and profiled by RNAseq.
Project description:Aubert2005 - Interaction between astrocytes
and neurons on energy metabolism
Enocded non-curated model. Issues:
- Confusing equations A.41 and A.42
- Missing values for parameters Vv,0 and dHb,0
This model is described in the article:
Interaction between
astrocytes and neurons studied using a mathematical model of
compartmentalized energy metabolism.
Aubert A, Costalat R.
J. Cereb. Blood Flow Metab. 2005 Nov;
25(11): 1476-1490
Abstract:
Understanding cerebral energy metabolism in neurons and
astrocytes is necessary for the interpretation of functional
brain imaging data. It has been suggested that astrocytes can
provide lactate as an energy fuel to neurons, a process
referred to as astrocyte-neuron lactate shuttle (ANLS). Some
authors challenged this hypothesis, defending the classical
view that glucose is the major energy substrate of neurons, at
rest as well as in response to a stimulation. To test the ANLS
hypothesis from a theoretical point of view, we developed a
mathematical model of compartmentalized energy metabolism
between neurons and astrocytes, adopting hypotheses highly
unfavorable to ANLS. Simulation results can be divided between
two groups, depending on the relative neuron versus astrocyte
stimulation. If this ratio is low, ANLS is observed during all
the stimulus and poststimulus periods (continuous ANLS), but a
high ratio induces ANLS only at the beginning of the stimulus
and during the poststimulus period (triphasic behavior).
Finally, our results show that current experimental data on
lactate kinetics are compatible with the ANLS hypothesis, and
that it is essential to assess the neuronal and astrocytic
NADH/NAD+ ratio changes to test the ANLS hypothesis.
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Project description:The impact of Apolipoprotein E4 (APOE4), the strongest genetic risk factor for Alzheimer's disease (AD), on human brain cellular function remains unclear. Here we investigated the effects of APOE4 on brain cell types derived from population and isogenic human induced pluripotent stem cell models, post-mortem brain and APOE targeted replacement mice. Population and isogenic models uncover that APOE4 local haplotype rather than a single risk allele alone contributes to the risk. Global transcriptomic analyses reveal human specific, APOE4-driven lipid metabolic dysregulation in astrocytes and microglia. APOE4 leads to elevated de novo cholesterol synthesis despite the intracellular cholesterol accumulation due to lysosomal sequestration of cholesterol in astrocytes. Transcriptome analyses uncovered Matrisome dysregulation associated with upregulated chemotaxis, glial activation and lipid biosynthesis in astrocytes, co-cultured with neurons that recapitulates altered astrocyte matrisome signaling in human brain. Thus, APOE4 initiates glia-specific cell and non-cell autonomous dysregulation that may contribute to increased AD risk.
Project description:The impact of Apolipoprotein E4 (APOE4), the strongest genetic risk factor for Alzheimer's disease (AD), on human brain cellular function remains unclear. Here we investigated the effects of APOE4 on brain cell types derived from population and isogenic human induced pluripotent stem cell models, post-mortem brain and APOE targeted replacement mice. Population and isogenic models uncover that APOE4 local haplotype rather than a single risk allele alone contributes to the risk. Global transcriptomic analyses reveal human specific, APOE4-driven lipid metabolic dysregulation in astrocytes and microglia. APOE4 leads to elevated de novo cholesterol synthesis despite the intracellular cholesterol accumulation due to lysosomal sequestration of cholesterol in astrocytes. Transcriptome analyses uncovered Matrisome dysregulation associated with upregulated chemotaxis, glial activation and lipid biosynthesis in astrocytes, co-cultured with neurons that recapitulates altered astrocyte matrisome signaling in human brain. Thus, APOE4 initiates glia-specific cell and non-cell autonomous dysregulation that may contribute to increased AD risk.
Project description:The impact of Apolipoprotein E4 (APOE4), the strongest genetic risk factor for Alzheimer's disease (AD), on human brain cellular function remains unclear. Here we investigated the effects of APOE4 on brain cell types derived from population and isogenic human induced pluripotent stem cell models, post-mortem brain and APOE targeted replacement mice. Population and isogenic models uncover that APOE4 local haplotype rather than a single risk allele alone contributes to the risk. Global transcriptomic analyses reveal human specific, APOE4-driven lipid metabolic dysregulation in astrocytes and microglia. APOE4 leads to elevated de novo cholesterol synthesis despite the intracellular cholesterol accumulation due to lysosomal sequestration of cholesterol in astrocytes. Transcriptome analyses uncovered Matrisome dysregulation associated with upregulated chemotaxis, glial activation and lipid biosynthesis in astrocytes, co-cultured with neurons that recapitulates altered astrocyte matrisome signaling in human brain. Thus, APOE4 initiates glia-specific cell and non-cell autonomous dysregulation that may contribute to increased AD risk.
Project description:APOE4 genotype is the strongest risk factor for the pathogenesis of sporadic Alzheimer’s disease (AD), but the detailed molecular mechanism of APOE4-mediated synaptic impairment remains to be determined in human cellular context. In this study, we generated human astrocyte model carrying APOE3 or APOE4 genotype using human induced pluripotent stem cells (iPSCs), in which isogenic APOE4 iPSCs were genome-edited from healthy control APOE3 iPSCs. By transcriptome analysis of human astrocytes between APOE genotypes, we showed the upregulation of an extracellular matrix glycoprotein in human APOE4 astrocytes, which may cause synaptic degeneration in concert with the equivocal reactive character and lipid change. Together, these results demonstrate novel negative impact of human APOE4 astrocyte on synaptic integrity and lead to a promising therapeutic intervention into APOE4-carriers.
Project description:The APOE gene is diversified by three alleles e2, e3, and e4 encoding corresponding apolipoprotein (apo) E isoforms. The e4 allele promotes age-related cognitive decline, risk of Alzheimer’s disease (AD), and the rate of AD dementia progression. ApoE is produced by astrocytes as high-density lipoprotein-like particles and these are internalized by neurons upon binding to neuron-expressed apoE receptors. ApoE isoforms differentially engage neuronal plasticity through poorly understood mechanisms. We examined here the effects of native apoE lipoproteins produced by immortalized astrocytes homozygous for e2, e3, and e4 alleles on the maturation and the transcriptomic profile of primary hippocampal neurons. Control neurons were grown in the presence of conditioned media from Apoe-/- astrocytes. ApoE2 and apoE3 significantly increase the dendritic arbor branching, the combined neurite length, and the total arbor surface of the hippocampal neurons, while apoE4 fails to produce similar effects and even significantly reduces the combined neurite length compared to the control. ApoE lipoproteins show no systemic effect on dendritic spine density, yet apoE2 and apoE3 increase the mature spines fraction, while apoE4 increases the immature spine fraction. This is associated with opposing effects of apoE2 or apoE3 and apoE4 on the expression of NR1 NMDA receptor subunit and PSD95. There are 1,062 genes differentially expressed across neurons cultured in the presence of apoE lipoproteins compared to the control. KEGG enrichment and gene ontology analyses show common for apoE2 and apoE3 activation of genes involved in neurite branching, and synaptic signaling. In contrast, apoE4 cultured neurons show upregulation of genes related to the glycolipid metabolism, which are involved in dendritic spine turnover and those which are usually silent in neurons and are related to cell cycle and DNA repair. In conclusion our work reveals that lipoprotein particles comprised of various apoE isoforms differentially regulate neuronal development through interaction with neuronal transcriptome. ApoE4 produces a functionally distinct transcriptomic profile, which is associated with attenuated neuronal development. Differential regulation of neuronal transcriptome by apoE isoforms is a newly identified biological mechanism, which has both implication in the development and aging of the CNS.
Project description:These arrays were conducted in order to confirm the generation of astrocytes from human embryonic stem cells and to determine expression differences between astrocyte subtypes. Experiment Overall Design: Human embryonic stem cells were differentated in vitro to neuroepithelial cells (day-17), neurons (day-50), or astrocytes (day-180) after specification with the morphogens retinoic acid (RA) or FGF8 from days 10-21.
Project description:Neurons induce a dramatic transformation in developing astrocytes, causing them to develop a complex stellate morphology resembling their appearance in vivo. However, the transcriptional changes that accompany this transformation are not known, nor are the signalling mechanisms responsible. Similarly, whether synaptic activity controls astrocytic gene expression and whether this leads to altered astrocytic function is unclear. This experiment seeks to investigate this non-cell-autonomously regulated gene expression by co-culturing astrocytes and neurons derived from closely related species (mouse and rat), and separating RNA-seq reads derived from each cell type in silico, thus shedding light on the signalling mechanisms underlying neuron-to-astrocyte communication and the functional consequences for astrocytes.
Project description:Apolipoprotein 4 (APOE4), is the strongest genetic risk allele associated with the development of late onset Alzheimer’s disease (AD). Across the CNS, astrocytes are the predominant expressor of Apoe while also being critical mediators of neuroinflammation and cerebral metabolism. APOE4 has been consistently linked with dysfunctional neuro-immunometabolism, however insights into the molecular constituents driving these responses remain unclear. Utilizing complimentary approaches across humanized ApoE expressing mice and isogenic IPS astrocytes, we demonstrate that harboring ApoE4 alters astrocyte immunometabolic response to pro-inflammatory stimuli. Our findings demonstrate that ApoE4-expressing astrocytes acquire distinct transcriptional repertoires at the single-cell and spatially-resolved domains, which driven, in-part, by preferential utilization of the cRel transcription factor. Further, inhibiting cRel translocation abrogated inflammatory-induced glycolytic shift and ultimately resulted in significantly dampened glycolysis-associated metabolites in tandem with mitigating production of multiple pro-inflammatory cytokines. Altogether, our findings elucidate novel cellular underpinnings by which ApoE4 drives maladaptive immunometabolic responses of astrocytes.