Oct4, Sox2, Klf4, and cMyc (OSKM) reprogram somatic cells to pluripotency. To gain a mechanistic understanding of their function, we mapped OSKM-binding, stage-specific transcription-factors (TFs), and chromatin-states in discrete reprogramming stages and performed loss- and gain-of-function experiments. We found that early in reprogramming OSK extensively bind somatic-enhancers and initiate their decommissioning by recruiting Hdac1. Concurrently, OSK engage other sites, including specific pluripotency-enhancers, and induce the relocation of somatic TFs to these sites and away from somatic-enhancers, extending somatic-enhancer decommissioning genome-wide. Pluripotency-enhancer selection early in reprogramming occurs predominantly at sites with high OSK-motif densities and requires collaborative binding by OSK. Most pluripotency-enhancers are selected later and occupied by OS and stage-specific-TFs like Esrrb. Overexpression of stage-specific-TFs influences reprogramming efficiency by changing OSK-occupancy, somatic-enhancer decommissioning, and pluripotency-enhancer selection. We propose that collaborative interactions among OSK and with stage-specific-TFs direct both somatic-enhancer decommissioning and pluripotency-enhancer selection, which drives the enhancer reorganization underlying reprogramming Overall design: RNA-seq
Cooperative Binding of Transcription Factors Orchestrates Reprogramming.
Specimen part, Cell line, Subject
View SamplesNaïve human embryonic stem cells (hESCs) can be derived from primed hESCs or directly from blastocysts, but their X-chromosome state has remained unresolved. We found that the inactive X-chromosome (Xi) of primed hESCs was reactivated in naïve culture conditions. Similar to cells of the blastocyst, resulting naive cells exhibited two active X-chromosomes with XIST expression and chromosome-wide transcriptional dampening, and initiated XIST-mediated X-inactivation upon differentiation. Both establishment and exit from the naïve state (differentiation) happened via an XIST-negative XaXa intermediate. Together, these findings identify a cell culture system for functionally exploring the two X-chromosome dosage compensation processes in early human development: X-dampening and X-inactivation. Furthermore, the naïve state reset Xi abnormalities of primed hESCs, providing cells better suited for downstream applications. However, naïve hESCs displayed differences to the embryo because XIST expression was predominantly mono-allelic instead of bi-allelic, and X-inactivation was non-random, indicating the need for further culture improvement. Overall design: Differentiated naïve human embryonic stem cells and naïve human embryonic stem cells at different passages (Exp1 for late passage, Exp2 for early passage) were subjected to single cell RNA sequencing by the Fluidigm C1 Single-Cell Auto Prep System.
Human Naive Pluripotent Stem Cells Model X Chromosome Dampening and X Inactivation.
Specimen part, Subject
View SamplesTransition from a partially reprogrammed pre-iPSC state to iPSC state can be achieved by modulating levels of histone modifying enzymes or proteins that can bind to histone modifications
Proteomic and genomic approaches reveal critical functions of H3K9 methylation and heterochromatin protein-1γ in reprogramming to pluripotency.
Specimen part
View SamplesFemale human ESC-lines can carry active X-chromosomes (Xa) or an XIST-RNA-coated inactive X-chromosome (XiXIST+). Additionally, many ESC lines have abnormal X-chromosomeinactivation (XCI)-states where the Xi no longer expresses XIST-RNA and has transcriptionally active regions (eroded Xi=Xe). The fate of each XCI-state upon differentiation is unclear because individual lines often contain a mixture of XCI-states. Here, we established homogeneous XiXa, XeXa, and XaXa ESC-lines. Employing RNA-FISH, RNA-sequencing and DNA methylation analyses, we found that these lines were unable to initiate XIST-expression and X-chromosome-wide silencing upon differentiation indicating that the ESC XCI-state is maintained in differentiated cells. Consequently, differentiated XeXa and XaXa cells displayed higher levels of X-linked gene-expression than XiXa cells. Although global transcriptional compensation between X-chromosomes and autosomes is not required for female ESC-differentiation, the degree of X-chromosome-silencing influences differentiation efficiencies. Our data suggest that the XiXIST+Xa state is inherent to human ESCs and that all other XCI-states, including XaXa, are abnormal and arise during ESC-derivation or maintenance. Overall design: RNA-seq was used to measure the expression state of X-linked and autosomal genes in undifferentiated human embryonic stem cells with different X-chromosome states and their differentiated cells.
Human Embryonic Stem Cells Do Not Change Their X Inactivation Status during Differentiation.
Specimen part, Subject
View SamplesWe generated de novo induced pluripotent stem cells (iPSCs) from two Parkinson’s Disease patients (PD) harboring the p.A53T mutation. iPSC-derived mutant neurons displayed disease-relevant phenotypes at basal conditions, including protein aggregation, compromised neuritic outgrowth and contorted axons with swollen varicosities containing aSyn and tau. We have performed RNA Sequencing (RNA-Seq) of neurons from PD patient and control samples. RNA sequencing has also been performed to neurons derived from HUES samples subjected to the same differentiation protocol as reference. Overall design: We have performed RNA Sequencing (RNA-Seq) in neurons PD and control samples (two clones from each individual), along with HUES-derived neurons.
Defective synaptic connectivity and axonal neuropathology in a human iPSC-based model of familial Parkinson's disease.
Specimen part, Subject
View SamplesThis SuperSeries is composed of the SubSeries listed below.
The histone methyltransferase Wbp7 controls macrophage function through GPI glycolipid anchor synthesis.
Specimen part, Treatment
View SamplesHistone methyltransferases catalyze site-specific deposition of methyl groups, enabling recruitment of transcriptional regulators. In mammals, trimethylation of lysine 4 in histone H3, a modification localized at the transcription start sites of active genes, is catalyzed by six enzymes (SET1a and SET1b, MLL1MLL4) whose specific functions are largely unknown. By using a genomic approach, we found that in macrophages, MLL4 (also known as Wbp7) was required for the expression of Pigp, an essential component of the GPI-GlcNAc transferase, the enzyme catalyzing the first step of glycosylphosphatidylinositol (GPI) anchor synthesis. Impaired Pigp expression in Wbp7-/- macrophages abolished GPI anchor-dependent loading of proteins on the cell membrane. Consistently, loss of GPI-anchored CD14, the coreceptor for lipopolysaccharide (LPS)
The histone methyltransferase Wbp7 controls macrophage function through GPI glycolipid anchor synthesis.
Specimen part, Treatment
View SamplesThe transcriptomes of FACS-sorted siglec-F+ alveolar macrophages and siglec-f- CD11b+ exudative macrophages from inducible airway GM-CSF over-expressing transgenic mice (DTGM) were compared to non-inducible littermate controls during influenza A virus infection. Overall design: Examination of effect of GM-CSF on airway macrophages during influenza A virus infection
GM-CSF overexpression after influenza a virus infection prevents mortality and moderates M1-like airway monocyte/macrophage polarization.
Sex, Specimen part, Cell line, Subject
View SamplesGLUCOCORTICOIDS are steroid hormones that strongly influence intermediary carbohydrate metabolism by increasing the transcription rate of glucose-6-phosphatase (G6Pase) a key enzyme of gluconeogenesis, and suppress the immune system which makes them one of the most important therapeutic agents in the treatment of allergic, autoimmune and inflammatory diseases. The biologic actions of circulating glucocorticoids are transmitted to the cells nucleus by the glucocorticoid receptor (GR). The nuclear liver X receptors (LXRs) bind to cholesterol metabolites, heterodimerize with the retinoid X receptor (RXR), and regulate the cholesterol turnover, the hepatic glucose metabolism by decreasing the expression of G6Pase, and repress a set of inflammatory genes in immune cells. The aim of this study is to evaluate the crosstalk between the GR- and LXR-mediated signaling systems. Transient transfection-based reporter assays and gene silencing methods using siRNAs for LXRs showed that overexpression/ligand (GW3965) activation of LXRs/RXRs repressed GR-stimulated transactivation of certain glucocorticoid response element (GRE)-driven promoters in a gene-specific fashion. Activation of LXRs by GW3965 attenuated dexamethasone-stimulated elevation of circulating glucose in rats and suppressed dexamethasone-induced mRNA expression of hepatic glucose-6-phosphatase (G6Pase) in rats, mice and human hepatoma HepG2 cells. In microarray transcriptomic analysis of rat liver, GW3965 differentially regulated glucocorticoid-induced transcriptional activity of about 15% of endogenous glucocorticoid-responsive genes. Mechanistically, and in vitro chromatin immunoprecipitation assay, we found that LXR/RXR bound GREs and inhibited GR binding to these DNA sequences in a gene-specific fashion. These novel results were further confirmed in in vivo binding assays, and in gel mobility shift assays, where recombinant LXR/RXR proteins were used to examine their interaction with classic or G6Pase GREs. We propose that administration of LXR agonists may be beneficial in glucocorticoid treatment- or stress-associated dysmetabolic states by directly attenuating the transcriptional activity of the GR on glucose and/or lipid metabolism.
Liver x receptors regulate the transcriptional activity of the glucocorticoid receptor: implications for the carbohydrate metabolism.
Specimen part
View SamplesGlucocorticoids play central roles in the regulation of energy metabolism by shifting it toward catabolism, while AMPK is the master regulator of energy homeostasis, sensing energy depletion and stimulating pathways of increasing fuel uptake and saving on peripheral supplies. We showed here that AMPK regulates glucocorticoid actions on carbohydrate metabolism by targeting the glucocorticoid receptor (GR) and modifying transcription of glucocorticoid-responsive genes in a tissue- and promoter-specific fashion. Activation of AMPK in rats reversed glucocorticoid-induced hepatic steatosis and suppressed glucocorticoid-mediated stimulation of glucose metabolism. Transcriptomic analysis in the liver suggested marked overlaps between the AMPK and glucocorticoid signaling pathways directed mostly from AMPK to glucocorticoid actions. AMPK accomplishes this by phosphorylating serine 211 of the human GR indirectly through phosphorylation and consequent activation of p38 MAPK and by altering attraction of transcriptional coregulators to DNA-bound GR. In human peripheral mononuclear cells, AMPK mRNA expression positively correlated with that of glucocorticoid-responsive GILZ, which correlated also positively with the body mass index of subjects. These results indicate that the AMPK-mediated energy control system modulates glucocorticoid action at target tissues. Since increased action of glucocorticoids is associated with development of metabolic disorders, activation of AMPK could be a promising target for developing pharmacologic interventions to these pathologies.
AMPK regulates metabolic actions of glucocorticoids by phosphorylating the glucocorticoid receptor through p38 MAPK.
Sex
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