Astrocye and oligodendrocyte – love at first sight with myelin consequences
ABSTRACT: One way by which astrocytes modulate oligodendrocytes’ activity is by delivering neurotransmitters and leukemia inhibitory factor (Lif) in the medium that bind oligodendrocyte receptors. Most of these receptors are involved in intercellular Ca2+-signaling (ICS). However, not much is known about the interactions between myelination (MYE) and ICS genes and how astrocyte nearness modulates the oligodendrocyte genomic myelination fabric. We profiled the transcriptomes of immortalized oligodendrocyte precursor cells (Oli-neu) when cultured alone or co-cultured with cortical astrocytes. The astrocytes were plated in cell culture insert systems that did not allow formation of gap junction channels with oligodendrocytes but permitted exchange of soluble factors via the culture medium. Remarkably, astrocyte proximity induced a larger increase of the overall expression level and interlinkage of MYE genes than the differentiating 10d treatment with 1 mM dibutyryl cAMP that turns Oli-neu cells into myelin-associated glycoprotein-positive oligodendrocyte-like cells. Moreover, more MYE and ICS genes were turned on and fewer turned off by astrocyte proximity than by differentiating treatment. Lif receptor was up-regulated by astrocyte proximity but not by the differentiating treatment. We have identified the responsible transcriptomic networks by which the intercellular ICS gene web controls MYE gene web, with genes encoding the gap junction proteins (connexins, Cx) Cx29, Cx32 and Cx47 playing central roles. The novel Prominent Gene Analysis (that refines iteratively the functional webs to optimize the interconnectivity and expression stability of the associated genes) was used to select and rank the most relevant MYE and ICS genes and build the corresponding gene webs. Determine the modifications of the myelination transcriptome induced in Oli- neu control cells by differentiating treatment and proximity of cortical astrocytes. Four culture dishes of each of control, differentiated and in the astrocyte proximity Oli-neu cells were profiled using Duke mouse 30K and 36k oligonucleotide arrays in the "multiple yellow" hybrization design.
Project description:Extensive literature documented that astrocytes release neurotransmitters, cytokines and other signaling molecules that modulate migration, maturation and myelin synthesis of oligodendrocytes through mechanisms primarily converging on cytosolic [Ca2+] transients. Considering the long term effects, it is expected that astrocyte conditioned medium is a major regulator of gene expression in oligodendrocytes even in the absence of cytosol-to-cytosol communication via astrocyte-oligodendrocyte gap junction channels. Indeed, by comparing the transcriptomes of immortalized precursor oligodendrocyte (Oli-neu) cells when cultured alone and cocultured with non-touching astrocytes we found profound changes in gene expression level, control and networking. Remarkably, the astrocyte proximity was more effective in remodeling the myelination (MYE) gene fabric and its control by cytokine receptor (CYR) modulated intercellular Ca2+-signaling (ICS) transcriptomic network than the db-cAMP treatment induced transformation into myelin-associated glycoprotein-positive oligodendrocyte-like cells. Moreover, astrocyte proximity up-regulated 37 MYE genes and switched on another 14 MYE, 23 ICS and 4 CYR genes, enhancing the roles of the leukemia inhibitory factor receptor and connexins Cx29 and Cx47. The novel Prominent Gene Analysis identified enhancer of zeste homolog 2 as the most relevant MYE gene in the astrocyte proximity, notch gene homolog1 in control and B-cell leukemia/lymphoma 2 in differentiated Oli-neu cells. Overall design: Determine the modifications of the myelination transcriptome induced in Oli- neu control cells by differentiating treatment and proximity of cortical astrocytes. Four culture dishes of each of control, differentiated and in the astrocyte proximity Oli-neu cells were profiled using Duke mouse 30K and 36k oligonucleotide arrays in the "multiple yellow" hybrization design.
Project description:We profiled the transcriptomes of primary mouse cortical astrocytes cultured alone or co-cultured with immortalized precursor oligodendrocytes (Oli-neu cells). Filters between the cell types prevented formation of hetero-cellular gap junction channels but allowed for free exchange of the two culture media. We previously reported that major functional pathways in the Oli-neu cells are remodeled by the proximity of non-touching astrocytes and that astrocytes and oligodendrocytes form a panglial transcriptomic syncytium in the brain. Here, we present evidence that the astrocyte transcriptome likewise changes significantly in the proximity of non-touching Oli-neu cells. Our results indicate that the cellular environment strongly modulates the transcriptome of each cell type and that integration in a heterocellular tissue changes not only the expression profile but also the expression control and networking of the genes in each cell phenotype. The significant decrease of the overall transcription control suggests that in the co-culture astrocytes are closer to their normal conditions from the brain. The Oli-neu secretome regulates astrocyte genes known to modulate neuronal synaptic transmission and remodels calcium, chemokine, NOD-like receptor, PI3K-Akt, and thyroid hormone signaling, as well as actin-cytoskeleton, autophagy, cell cycle, and circadian rhythm pathways. Moreover, the co-culture significantly changes the gene hierarchy in the astrocytes.
Project description:In this study, we have investigated the global impact of heterogeneous nuclear Ribonuclear Protein (hnRNP) H/F-mediated regulation of splicing events and gene expression in oligodendrocytes. We have performed a genome-wide transcriptomic analysis at the gene and exon levels in Oli-neu cells treated with siRNA that targets hnRNPH/F compared to untreated cells using Affymetrix Exon Array. Gene expression levels and regulated exons were identified with the GenoSplice EASANA algorithm. Bioinformatics analyses were performed to determine the structural properties of G tracts that correlate with the function of hnRNPH/F as enhancers vs. repressors of exon inclusion. Different types of alternatively spliced events are regulated by hnRNPH/F. Intronic G tracts density, length and proximity to the 5' splice site correlate with the hnRNPH/F enhancer function. Additionally, 6% of genes are differently expressed upon knock down of hnRNPH/F. Genes that regulate the transition of oligodendrocyte progenitor cells to oligodendrocytes are differentially expressed in hnRNPH/F depleted Oli-neu cells, resulting in a decrease of negative regulators and an increase of differentiation-inducing regulators. The changes were confirmed in developing oligodendrocytes in vivo. This is the first genome wide analysis of splicing events and gene expression regulated by hnRNPH/F in oligodendrocytes and the first report that hnRNPH/F regulate genes that are involved in the transition from oligodendrocyte progenitor cells to oligodendrocytes.
Project description:Although bone marrow-derived mononuclear cells (BMNC) have been extensively used in cell therapy for cardiac diseases, little mechanistic information is available to support reports of their efficacy. To address this shortcoming, we compared structural and functional recovery and associated global gene expression profiles in post-ischaemic myocardium treated with BMNC transplantation. BMNC suspensions were injected into cardiac scar tissue 10 days after experimental myocardial infarction. Six weeks later, mice undergoing BMNC therapy were found to have normalized antibody repertoire and improved cardiac performance measured by ECG, treadmill exercise time and echocardiography. After functional testing, gene expression profiles in cardiac tissue were evaluated using high-density oligonucleotide arrays. Expression of more than 18% of the 11981 quantified unigenes was significantly altered in the infarcted hearts. BMNC therapy restored expression of 2099 (96.2%) of the genes that were altered by infarction but led to altered expression of 286 other genes, considered to be a side effect of the treatment. Transcriptional therapeutic efficacy, a metric calculated using a formula that incorporates both recovery and side effect of treatment, was 73%. In conclusion, our results confirm a beneficial role for bone marrow-derived cell therapy and provide new information on molecular mechanisms operating after BMNC transplantation on post ischemic heart failure in mice. We compared RNA samples extracted from whole hearts of infarcted mouse myocardium treated with bone marrow mononuclear cells control with untreated infarcted and control mice samples by analyzing hybridization to AECOM 32k mouse microarrays (http://microarray1k.aecom.yu.edu/) spotted with Operon version 3.0 70-mer oligonucleotides. The hybridization protocol and the slide type were uniform throughout the entire experiment to minimize the technical noise. Treated, control (sham) and infarcted red-labeled heart samples were hybridized against an in-house prepared green-labeled universal mouse reference.
Project description:After myocardial infarction (MI) activation of the immune system and inflammatory mechanisms, among others, can lead to ventricular remodeling and heart failure (HF). Interaction between these systemic alterations and corresponding changes in the heart has not been extensively examined in the setting of chronic ischemia. The main purpose of this study was to investigate alterations in cardiac gene and systemic cytokine profile in mice with post-ischemic HF. Plasma was tested for IgM and IgG anti-heart reactive repertoire and inflammatory cytokines. Heart samples were assayed for gene expression. Ischemic HF significantly increased the levels of serum IgM (by 5.2 fold) and IgG (by 3.6 fold) associated with remarkable content of anti-heart specificity. Comparable increase was observed in levels of circulating pro-inflammatory cytokines, such as IL-1β (3.8x) and TNF-α (6.0x). IFN-gamma was also increased in the MI group by 3.1x. However, IL-4 and IL-10 showed no significant difference between MI and sham groups. Chemokines such as MCP-1 and IL-8 were enhanced in the plasma of infarcted mice. We identified 2079 well annotated unigenes that were significantly regulated by the post-ischemic HF. Complement activation and immune response was among the most up-regulated processes. Interestingly, 21 out of the 101 quantified unigenes involved in inflammatory response were significantly up-regulated and none were down-regulated. These data indicate that post-ischemic heart remodeling is accompanied by immune mediated mechanisms that act both systemically and locally. We compared RNA samples extracted from whole hearts of control and infarcted mice samples by analyzing hybridization to AECOM 32k mouse microarrays (http://microarray1k.aecom.yu.edu/) spotted with Operon version 3.0 70-mer oligonucleotides. The hybridization protocol, the slide type and the scanner settings were uniform throughout the entire experiment to minimize the technical noise. Control (sham) and infarcted red-labeled heart samples were hybridized against an in-house prepared green-labeled universal mouse reference.
Project description:Chronic chagasic cardiomyopathy is a leading cause of heart failure in Latin American countries. About 30% of Trypanosoma cruzi-infected individuals develop this severe symptomatic form of the disease, characterized by intense inflammatory response accompanied by fibrosis deposition in the heart. We performed a microarray analysis of a mouse model of this disease and identified >5% alterations of gene expression in the heart. Most of the upregulations were associated with immune-inflammatory responses (chemokines, adhesion molecules, cathepsins and MHC molecules) and fibrosis deposition (extracellular matrix components, lysyl oxidase and Timp1). Our results indicate potentially relevant factors involved in the pathogenesis of the disease that may provide new therapeutic targets in chronic Chagas’ disease. The heart transcriptomes of 4 age-mached Trypanosoma cruzi-infected and 4 control C57Bl/6 mice were profiled and compared using Duke Mouse 30k Oligonucleotide Arrays (Operon V3.0.1) hybridized in the "multiple yellow" strategy described in Iacobas et al, Biochem Biophys Res Commun. 2006 349(1):329-38.
Project description:Chronic chagasic cardiomyopathy is one of the leading causes of heart failure in Latin American countries, being associated with intense inflammatory response and fibrosis. We have previously shown that bone marrow mononuclear cell (BMC) transplantation improves inflammation, fibrosis and ventricular diameter in hearts of mice with chronic Chagas’ disease. Here we investigated alterations of gene expression in the hearts of chronic chagasic mice submitted or not to BMC therapy. C57Bl/6 mice chronically infected with T. cruzi (6 months) were transplanted with BMC or saline i.v. and sacrificed 2 months later. RNA was extracted from the hearts of normal controls, chagasic and BMC transplanted mice and microarray analysis was performed using MO30k oligonucleotide arrays. Out of the 9390 unigenes quantified in all samples, 1702 had their expression altered in chronic chagasic hearts compared to those of normal mice. Major categories of significantly upregulated genes were related to inflammation, fibrosis and immune responses, while genes involved in mitochondrion function were downregulated. When BMC-treated chagasic hearts were compared to infected mice, 1631 (96%) of the alterations detected in infected hearts were not found, although an additional 109 genes were altered by treatment, indicating a remarkable 84% transcriptomic recovery. Immunofluorescence and morphometric analyses confirmed the effects of BMC therapy in the pattern of inflammatory-immune response and expression of adhesion molecules. Our results demonstrate important immunomodulatory effects of BMC therapy in chagasic cardiomyopathy and indicate potentially relevant factors involved in the pathogenesis of the disease that may provide new therapeutic targets. We compared RNA samples extracted from whole hearts of 4 control, 4 chagasic and 4 BMC-treated chagasic mice by analyzing hybridization to microarrays printed by Duke University (http://www.ncbi.nlm.nih.gove/geo/query/acc.cgi?acc=GPL8938) spotted with MO30k mouse Operon version 3.0 70-mer oligonucleotides. The hybridization protocol (see Soares et al, 2010), the slide type and the scanner settings were uniform throughout the entire experiment to minimize the technical noise. Briefly, 20 ug total RNA extracted in Trizol from each of the twelve samples (individual hearts) was reverse transcribed in the presence of fluorescent Alexa Fluor® 555- and Alexa Fluor®647-aha-dUTPs (Invitrogen, Carlsbad, CA) to obtain labeled cDNA. Red and green labeled samples of biological replicas were then co-hybridized (“multiple yellow” strategy, 22) overnight at 50° C. After washing (0.1% SDS and 1% SSC) to remove the non-hybridized cDNA, each array was scanned at 630V (635 nm) and 580V (532 nm) with GenePix 4100B scanner (Axon Instruments, Union City, CA) and images were primarily analyzed with GenePixPro 6.0 (Molecular Devices, Sunnyvale, CA). Microarray data were processed as described previously (Soares et al, 2010). A gene was considered as significantly up- or down-regulated when comparing four hearts from one condition to those from another if the absolute fold change was >1.5x and the p-vlaue of the Sutdent”s heteroscedastic t-test of equality of the means of the distributions with a Bonferroni-type adjustment for each redundancy group (set of spots probing the same gene) was <0.05.
Project description:Trypanosoma cruzi infection is a major cause of cardiomyopathy. Gene profiling studies of hearts from infected mice have revealed prominent changes in gene expression within many functional pathways. This variety of transcriptomic changes in infected mice raises the question of whether gene expression alterations in whole hearts are due to changes in infected cardiac myocytes or other cells or even to systemic effects of the infection on the heart. We employed microarrays to examine infected cardiac myocyte cultures 48 hr post-infection. Statistical comparison of gene expression levels of 2,258 well annotated unigenes in four independent cultures of infected and uninfected myocytes detected (p < 0.05) significant > 1.5 absolute fold changes in 221 (8.8%) of the sampled genes. Major categories of affected genes included those involved in immune response, extracellular matrix and cell adhesion. While changes in extracellular matrix and cell adhesion genes were anticipated, modulation of immune response genes in the infected myocytes was surprising. These findings on infected cardiac myocytes in culture reveal that altered gene expression described in the heart in Chagas disease are the consequence of both direct infection of the myocytes and resulting from presence of other cell types in the myocardium and systemic effects of infection. Transcriptomic alteration in neonatal mouse cultured cardiomyocytes induced by the parasite T.cruzi were detected by profiling and compared using AECOM mouse 32k oligonucleotide arrays hybridized in the "multiple yellow" strategy described in Iacobas et al, Biochem Biophys Res Commun. 2006 349(1):329-38.
Project description:We and other groups doumented that astrocytes modulate migration, maturation and myelin sythesis of oligodendrocytes through release of neurotransmitters, cytokins and other signaling molecules. However, much less is known about on how the oligodendrocytes affects the astrocytes. We compared the transcriptome of cortical astrocytes when cultured alone and co-cultured with non-touching immortalized precursor oligodendrocytes (Oli-neu) in insert systems. Experimental data indicate that the oligodendrocyte-conditioning medium has a substantial effect on the the gene expression in astrocytes. Moreover, oligodendendrocyte proximity remodels major astrocyte functional pathways. Overall design: we have used the multiple yellow design in which distinctly labeled samples of biological replicates are cohybridized with the microarray, the similarly labeled distinct conditions were compared and the results averaged for both channels. Thus each raw data file contains raw data for two samples (e.g. C1-2_US83300186_252665513680_S01_GE2_1105_Oct12_1_4.txt contains raw data for both C1 and C2 samples) and dye assignment is indicated in the label field in the corresponding sample records.
Project description:Overexpression of the major myelin proteolipid protein (PLP) is detrimental to brain development and function and is the most common cause of Pelizaeus-Merzbacher disease. microRNA (miRNA), small, noncoding RNAs, have been shown to play critical roles in oligodendrocyte lineage. In this study, we sought to investigate whether miRNAs control PLP abundance. To identify candidate miRNAs involved in this regulation, we have examined differentiation-induced changes in the expression of miRNAs in the oligodendroglial cell line Oli-neu and in enhanced green fluorescent protein positive oligodendrocytes ex vivo. We have identified 145 miRNAs that are expressed in oligodendrocyte cell lineage progression. Dicer1 expression decreases in differentiated oligodendrocytes, and knock down of Dicer1 results in changes in miRNAs similar to those associated with differentiation. To identify miRNAs that control the PLP expression, we have selected miRNAs whose expression is lower in differentiated vs. undifferentiated Oli-neu cells and that have one or more binding site(s) in the PLP 3'-untranslated region (3'UTR). The PLP 3'UTR fused to the luciferase gene reduces the activity of the reporter, suggesting that it negatively regulates message stability or translation. Such suppression is relieved by knock down of miR-20a. Overexpression of miR-20a decreases expression of the endogenous PLP in primary oligodendrocytes and of the reporter gene. Deletion or mutation of the putative binding site for miR-20a in the PLP 3'UTR abrogated such effects. Our data indicate that miRNA expression is regulated by Dicer1 levels in differentiated oligodendrocytes and that miR-20a, a component of the cluster that controls oligodendrocyte cell number, regulates PLP gene expression through its 3'UTR.