Opposite roles for astrocytes in developmental myelination and early myelin repair
Ontology highlight
ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE60276 | GEO | 2017/08/01
SECONDARY ACCESSION(S): PRJNA257923
REPOSITORIES: GEO
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Project description:Myelination by oligodendrocytes in the central nervous system (CNS) is essential for proper brain function, yet the molecular determinants that control this process remain poorly understood. The basic helix-loop-helix transcription factors Olig1 and Olig2 promote myelination, whereas bone morphogenetic protein (BMP) and Wnt/β-catenin signaling inhibit myelination. Here we show that these opposing regulators of myelination are functionally linked by the Olig1/2 common target Smad-interacting protein-1 (Sip1). We demonstrate that Sip1 is an essential modulator of CNS myelination. Sip1 represses differentiation inhibitory signals by antagonizing BMP receptor-activated Smad activity while activating crucial oligodendrocyte-promoting factors. Importantly, a key Sip1-activated target, Smad7, is required for oligodendrocyte differentiation and partially rescues differentiation defects caused by Sip1 loss. Smad7 promotes myelination by blocking the BMP- and β-catenin-negative regulatory pathways. Thus, our findings reveal that Sip1-mediated antagonism of inhibitory signaling is critical for promoting CNS myelination and point to new mediators for myelin repair. We carried out microarray profiling analysis in the Sip1 conditional KO (cKO) mouse spinal cord to detail the change of global gene expression. Sip1 c/c;Olig1-Cre mouse spinal cord was collected at P14 for RNA extraction and Affymetrix microarray analysis. Sip1 c/+;Olig1-Cre littermate spinal cord was used as the control.
2012-08-31 | E-GEOD-40510 | biostudies-arrayexpress
Project description:The transcriptional control of CNS myelin gene expression is poorly understood. Here we identify gene model 98, which we have named Myelin-gene Regulatory Factor (MRF), as a transcriptional regulator required for CNS myelination. Within the CNS, MRF is specifically expressed by postmitotic oligodendrocytes. MRF is a nuclear protein containing an evolutionarily conserved DNA binding domain homologous to a yeast transcription factor. Knockdown of MRF in oligodendrocytes by RNA interference prevents expression of most CNS myelin genes; conversely, overexpression of MRF within cultured oligodendrocyte progenitors or the chick spinal cord promotes expression of myelin genes. In mice lacking MRF within the oligodendrocyte lineage, pre-myelinating oligodendrocytes are generated but display severe deficits in myelin gene expression and fail to myelinate. These mice display severe neurological abnormalities, and die due to seizures during the third postnatal week. These findings establish MRF as a critical transcriptional regulator essential for oligodendrocyte maturation and CNS myelination. We used microarrays to compare cultured oligodendrocytes (differentiated in vitro for 4 days) from MRF conditional knockouts and control litteramates to look at the effects of MRF deficiency on myelin gene expression. Mouse OPCs grown in vitro in the presence of PDGF serve as a baseline for gene expression prior to differentiation.
2009-05-31 | GSE15303 | GEO
Project description:microRNAs (miRNAs) have been implicated in oligodendrogenesis and demyelinating diseases; however, identification of individual miRNAs responsible has remained elusive. Through targeted mutagenesis, we find that miR-219 is required for proper oligodendrocyte differentiation and myelination in vivo. Deletion of miR-338 together with miR-219 further exacerbates hypomyelination phenotypes. Temporally specific ablation reveals a critical role for miR-219 in oligodendrocyte remyelination after demyelination, while overexpression of miR-219 promotes precocious oligodendrocyte maturation and myelin regeneration. Accordingly, administration of miR-219 mimics to lysolecithin-induced demyelinating lesions in the murine spinal cord and brain enhances myelin restoration. Through integrating analyses of transcriptome profiling and biotin-affinity miRNA pull-down, we identify a set of stage-specific targets of miR-219, including Etv5 and Lingo1, as oligodendrocyte differentiation inhibitors. Inhibiting Etv5 and Lingo1 leads to a partial rescue of differentiation defects observed in miR-219-mutant OLs in vitro. Together, our findings identify context-specific miRNA-regulated checkpoints that control CNS myelinogenesis and myelin repair.
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Project description:Remyelination can occur naturally in demyelinating lesions, but often fails in human demyelinating diseases such as multiple sclerosis (MS). The function of the innate immune system is essential for the regenerative response, but how exactly microglia and macrophages clear myelin debris after injury and tailor a specific regenerative response is unclear. Here, we asked whether pro-inflammatory microglial/macrophage activation is required for this process. We established a novel toxin-based spinal cord model of de- and remyelination in zebrafish and showed that pro-inflammatory nuclear factor κB (NF-κB) dependent activation occurs in phagocytes rapidly after myelin injury. We found that the pro-inflammatory response depends on myeloid differentiation primary response 88 (MyD88), the canonical adaptor for inflammatory signaling pathways downstream of toll-like receptors (TLRs). MyD88-deficient mice and zebrafish were impaired not only in the degradation of myelin debris, but also in initiating the generation of new oligodendrocytes for myelin repair. We identified reduced generation of tumor necrosis factor-α (TNF-α) in lesions of MyD88-deficient animals, a pro-inflammatory molecule that was able to induce the generation of new oligodendrocytes. Our study shows that pro-inflammatory phagocytic signaling is an evolutionary conserved mechanism necessary for degrading myelin debris, essential for inflammation resolution, and for initiating the secretion of pro-inflammatory myelin repair molecules.
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Project description:Myelination by oligodendrocytes in the central nervous system (CNS) is essential for proper brain function, yet the molecular determinants that control this process remain poorly understood. The basic helix-loop-helix transcription factors Olig1 and Olig2 promote myelination, whereas bone morphogenetic protein (BMP) and Wnt/?-catenin signaling inhibit myelination. Here we show that these opposing regulators of myelination are functionally linked by the Olig1/2 common target Smad-interacting protein-1 (Sip1). We demonstrate that Sip1 is an essential modulator of CNS myelination. Sip1 represses differentiation inhibitory signals by antagonizing BMP receptor-activated Smad activity while activating crucial oligodendrocyte-promoting factors. Importantly, a key Sip1-activated target, Smad7, is required for oligodendrocyte differentiation and partially rescues differentiation defects caused by Sip1 loss. Smad7 promotes myelination by blocking the BMP- and ?-catenin-negative regulatory pathways. Thus, our findings reveal that Sip1-mediated antagonism of inhibitory signaling is critical for promoting CNS myelination and point to new mediators for myelin repair. ChIP-seq was performed to identify Olig2 direct target genes in oligodendrocytes during oligodendrocyte differentiation.
2012-08-31 | E-GEOD-40506 | biostudies-arrayexpress
Project description:Spinal cord injury (SCI) results in loss of neurons, oligodendrocytes and myelin sheaths, all of which are not efficiently restored. The scarcity of oligodendrocytes in the lesion site impairs remyelination of spared fibres, which leaves axons denuded, impedes signal transduction and contributes to permanent functional deficits. In contrast to mammals, zebrafish can functionally regenerate the spinal cord. Yet, little is known about oligodendroglial lineage biology and remyelination capacity after SCI in a regeneration-permissive context. Here, we report that in adult zebrafish, SCI results in axonal, oligodendrocyte and myelin sheath loss. We find that OPCs, the oligodendorocyte progenitor cells, survive the injury, enter a reactive state, proliferate and differentiate into oligodendrocytes. Concomitantly, the oligodendrocyte population is re-established to pre-injury levels within two weeks.Transcriptional profiling revealed that reactive OPCs upregulate the expression of several myelination-related genes. Interestingly, global reduction of axonal tracts and partial re-myelination, relative to pre-injury levels, persist at later stages of regeneration, yet suffices for functional recovery. Taken together, these findings imply that in the zebrafish spinal cord, OPCs replace lost oligodendrocytes and, thus, re-establish myelination during regeneration.
2020-12-04 | GSE161686 | GEO
Project description:Spinal cord injury (SCI) results in loss of neurons, oligodendrocytes and myelin sheaths, all of which are not efficiently restored. The scarcity of oligodendrocytes in the lesion site impairs remyelination of spared fibres, which leaves axons denuded, impedes signal transduction and contributes to permanent functional deficits. In contrast to mammals, zebrafish can functionally regenerate the spinal cord. Yet, little is known about oligodendroglial lineage biology and remyelination capacity after SCI in a regeneration-permissive context. Here, we report that in adult zebrafish, SCI results in axonal, oligodendrocyte and myelin sheath loss. We find that OPCs, the oligodendorocyte progenitor cells, survive the injury, enter a reactive state, proliferate and differentiate into oligodendrocytes. Concomitantly, the oligodendrocyte population is re-established to pre-injury levels within two weeks.Transcriptional profiling revealed that reactive OPCs upregulate the expression of several myelination-related genes. Interestingly, global reduction of axonal tracts and partial re-myelination, relative to pre-injury levels, persist at later stages of regeneration, yet suffices for functional recovery. Taken together, these findings imply that in the zebrafish spinal cord, OPCs replace lost oligodendrocytes and, thus, re-establish myelination during regeneration.
2020-12-04 | GSE161642 | GEO
Project description:Oligodendrocytes are key to normal developmental myelination after birth, and for myelin repair. We used scRNA seq to evaluate gene expresison changes in oligodendrocytes in a mouse model of full term neoanatl arterial ischemic stroke.
2022-07-14 | GSE208222 | GEO
Project description:The progressive loss of CNS myelin in patients with multiple sclerosis (MS) has been proposed to result from the combined effects of damage to oligodendrocytes and failure of remyelination. A common feature of demyelinated lesions is the presence of oligodendrocyte precursors (OLPs) blocked at a premyelinating stage. However, the mechanistic basis for inhibition of myelin repair is incompletely understood. To identify novel regulators of OLP differentiation, potentially dysregulated during repair, we performed a genome-wide screen of 1040 transcription factor-encoding genes expressed in remyelinating rodent lesions. We report that M-bM-^HM-<50 transcription factor-encoding genes show dynamic expression during repair and that expression of the Wnt pathway mediator Tcf4 (aka Tcf7l2) within OLPs is specific to lesionedM-bM-^@M-^Tbut not normalM-bM-^@M-^Tadult white matter. We report that M-NM-2-catenin signaling is active during oligodendrocyte development and remyelination in vivo. Moreover, we observed similar regulation of Tcf4 in the developing human CNS and lesions of MS. Data mining revealed elevated levels of Wnt pathway mRNA transcripts and proteins within MS lesions, indicating activation of the pathway in this pathological context. We show that dysregulation of WntM-bM-^@M-^SM-NM-2-catenin signaling in OLPs results in profound delay of both developmental myelination and remyelination, based on (1) conditional activation of M-NM-2-catenin in the oligodendrocyte lineage in vivo and (2) findings from APCMin mice, which lack one functional copy of the endogenous Wnt pathway inhibitor APC. Together, our findings indicate that dysregulated WntM-bM-^@M-^SM-NM-2-catenin signaling inhibits myelination/remyelination in the mammalian CNS. Evidence of Wnt pathway activity in human MS lesions suggests that its dysregulation might contribute to inefficient myelin repair in human neurological disorders. 12 samples total. Two variables in the experiment: genotype (wild type or Olig2cre/DA-Cat) and Developmental stage (Day 4 or Day 15). 4 phenotypes in total with 3 biological replicates for each phenotype.
2009-12-10 | E-GEOD-19403 | biostudies-arrayexpress
Project description:The transcriptional control of CNS myelin gene expression is poorly understood. Here we identify gene model 98, which we have named Myelin-gene Regulatory Factor (MRF), as a transcriptional regulator required for CNS myelination. Within the CNS, MRF is specifically expressed by postmitotic oligodendrocytes. MRF is a nuclear protein containing an evolutionarily conserved DNA binding domain homologous to a yeast transcription factor. Knockdown of MRF in oligodendrocytes by RNA interference prevents expression of most CNS myelin genes; conversely, overexpression of MRF within cultured oligodendrocyte progenitors or the chick spinal cord promotes expression of myelin genes. In mice lacking MRF within the oligodendrocyte lineage, pre-myelinating oligodendrocytes are generated but display severe deficits in myelin gene expression and fail to myelinate. These mice display severe neurological abnormalities, and die due to seizures during the third postnatal week. These findings establish MRF as a critical transcriptional regulator essential for oligodendrocyte maturation and CNS myelination. We used microarrays to compare cultured oligodendrocytes (differentiated in vitro for 4 days) from MRF conditional knockouts and control litteramates to look at the effects of MRF deficiency on myelin gene expression. Mouse OPCs grown in vitro in the presence of PDGF serve as a baseline for gene expression prior to differentiation. Mouse OPCs from MRF conditional knockout (MRF fl/fl, Olig2 wt/cre) mice and control littermates (MRF wt/fl; Olig2 wt/cre) were isolated from enzymatically dissociated P7 mouse brains as previously described (Cahoy et al., 2008), positively immunopanning for PDGFR-alpha following a depletion of microglia with BSL1. Cells were grown in defined serum-free media as previously described (Dugas et al., 2006), but with the addition of 2% B-27 (Invitrogen). Cells were proliferated for several days in the presence of PDGF-AA (10 ng/ml, PeproTech) and then differentiation induced by withdrawal of PDGF-AA and addition of triiodothyronine (T3) (40 ng/ml; Sigma). RNA was isolated from cells 4 days after induction of differentiation; OPCs maintained in PDGF-AA serve as a baseline of OPC gene expression. Total RNA was isolated from cells with the RNeasy micro kit (Qiagen, Valencia, CA) using Qiagen on-column DNase treatment to remove any contaminating genomic DNA. The integrity of RNA was assessed using an Agilent 2100 Bioanalyzer (Agilent Technologies) and RNA concentration was determined using a NanoDrop ND-1000 spectrophotometer (NanoDrop, Rockland, DE). Biotinylated cRNAs for hybridization to Affymetrix 3'-arrays were prepared from 1ug total RNA using the Affymetrix two-cycle target labeling assay with spike in controls (Affymetrix Inc., Santa Clara, CA, 900494). Labeled-cRNA was fragmented and hybridized to Mouse Genome 430 2.0 Arrays (3'-arrays, Affymetrix, 900495) following the manufacturer's protocols. Raw image files were processed using Affymetrix GCOS 1.3 software to calculate individual probe cell intensity data and generate CEL data files. Using GCOS and the MAS 5.0 algorithm, intensity data was normalized per chip to a target intensity TGT value of 500 and expression data and present/absent calls for individual probe sets calculated. Gene symbols and names for data analyzed with the MAS 5.0 algorithm were from the Affymetrix Netaffx Mouse430_2 annotations file (http://www.affymetrix.com/support/technical/byproduct.affx?product=moe430-20). Quality control was performed by examining raw DAT image files for anomalies, confirming each GeneChip array had a background value less than 100, monitoring that the percencelle present calls was appropriate for the cell type, and inspecting the poly(A) spike in controls, housekeeping genes, and hybridization controls to confirm labeling and hybridization consistency.
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