RNAi profiling of mouse 3T3-L1 adipocytes knocked down for PPAR gamma returned the expression of most adipocyte genes towards preadipocyte levels
ABSTRACT: The nuclear receptor PPAR gamma is required for adipocyte differentiation, but its role in mature adipocytes is less clear. Here we report that knockdown of PPAR gamma expression in 3T3-L1 adipocytes returned the expression of most adipocyte genes towards preadipocyte levels. Consistently, down regulated but not up regulated genes showed strong enrichment of PPAR gamma binding. Surprisingly, not all adipocyte genes were reversed and the adipocyte morphology was maintained for an extended period after PPAR gamma depletion. To explain this, we focused on transcriptional regulators whose adipogenic regulation was not reversed upon PPAR gamma depletion. We identified GATA2, a transcription factor whose down-regulation early in adipogenesis is required for preadipocyte differentiation, remaining low after PPAR gamma knockdown. Forced expression of GATA2 in mature adipocytes complemented PPAR gamma depletion and impaired adipocyte functionality with a more preadipocyte- like gene expression profile. Ectopic expression of GATA2 in adipose tissue in vivo had similar effect on adipogenic gene expression. These results suggest that PPAR gamma-independent down regulation of GATA2 prevents reversion of mature adipocytes after PPAR gamma depletion. Experiment Overall Design: This dataset consists of three sample groups: preadipocytes, control siRNA treated adipocytes, and PPAR gamma siRNA treated adipocytes. Each sample group consists of three replicates samples. Each sample was hybridized to a separate array for a total of nine arrays. Experiment Overall Design: Technical replicates: Pread 1, Pread 2, Pread 3 Experiment Overall Design: Technical replicates: Cont siRNA 1, Cont siRNA 2, Cont siRNA 3 Experiment Overall Design: Technical replicates: PPAR gamma siRNA 1, PPAR gamma siRNA 2, PPAR gamma siRNA 3
Project description:The nuclear receptor PPAR gamma is required for adipocyte differentiation, but its role in mature adipocytes is less clear. Here we report that knockdown of PPAR gamma expression in 3T3-L1 adipocytes returned the expression of most adipocyte genes towards preadipocyte levels. Consistently, down regulated but not up regulated genes showed strong enrichment of PPAR gamma binding. Surprisingly, not all adipocyte genes were reversed and the adipocyte morphology was maintained for an extended period after PPAR gamma depletion. To explain this, we focused on transcriptional regulators whose adipogenic regulation was not reversed upon PPAR gamma depletion. We identified GATA2, a transcription factor whose down-regulation early in adipogenesis is required for preadipocyte differentiation, remaining low after PPAR gamma knockdown. Forced expression of GATA2 in mature adipocytes complemented PPAR gamma depletion and impaired adipocyte functionality with a more preadipocyte- like gene expression profile. Ectopic expression of GATA2 in adipose tissue in vivo had similar effect on adipogenic gene expression. These results suggest that PPAR gamma-independent down regulation of GATA2 prevents reversion of mature adipocytes after PPAR gamma depletion. Keywords: cell type comparison, Gata2, PPAR gamma, adipocyte, preadipocytes, differentiation Overall design: This dataset consists of three sample groups: preadipocytes, control siRNA treated adipocytes, and PPAR gamma siRNA treated adipocytes. Each sample group consists of three replicates samples. Each sample was hybridized to a separate array for a total of nine arrays. Technical replicates: Pread 1, Pread 2, Pread 3 Technical replicates: Cont siRNA 1, Cont siRNA 2, Cont siRNA 3 Technical replicates: PPAR gamma siRNA 1, PPAR gamma siRNA 2, PPAR gamma siRNA 3
Project description:Adipogenesis is tightly controlled by a complex network of transcription factors acting at different stages of differentiation. Peroxisome proliferator-activated receptor gamma (PPAR gamma) and CCAAT/enhancer binding protein (C/EBP) family members are key regulators of this process. We have employed DNase I hypersensitive site analysis to investigate the genome-wide changes in chromatin structure that accompany the binding of adipogenic transcription factors. These analyses revealed a dramatic and dynamic modulation of the chromatin landscape during the first hours of adipocyte differentiation that coincides with cooperative binding of multiple early transcription factors (including glucocorticoid receptor, retinoid X receptor, Stat5a, C/EBPbeta and -delta) to transcription factor 'hotspots'. Our results demonstrate that C/EBPbeta marks a large number of these transcription factor 'hotspots' prior to induction of differentiation and chromatin remodeling and is required for their establishment. Furthermore, a subset of early remodeled C/EBP binding sites persists throughout differentiation and is later occupied by PPAR gamma , indicating that early C/EBP family members, in addition to their well established role in activation of PPAR gamma transcription, may act as pioneering factors for PPAR gamma binding. DNase I hypersensitive chromatin regions and transcription factor binding sites were identified at various time points of 3T3-L1 differentiation using DHS-seq and ChIP-seq, respectively.
Project description:The nuclear receptor Peroxisome Proliferator Activator Receptor (PPAR ) is the target of antidiabetic thiazolidinedione drugs, which improve insulin resistance but have side-effects that limit widespread use. PPAR is required for adipocyte differentiation, but is also expressed in other cell types, notably macrophages, where it influences atherosclerosis, insulin resistance, and inflammation. A central question is whether PPAR binding in macrophages occurs at the same or different genomic locations compared to adipocytes. Here, utilizing chromatin immunoprecipitation and high throughput sequencing (ChIP-seq), we demonstrate that PPAR cistromes in adipocytes and macrophages are predominantly cell type specific. In macrophages, PPAR colocalizes with the hematopoietic transcription factor PU.1 in areas of open chromatin and histone acetylation, near a distinct set of immune genes in addition to a number of metabolic genes shared with adipocytes. In adipocytes, the macrophage-unique binding regions are marked with repressive histone modifications, typically associated with local chromatin compaction and gene silencing. PPAR , when introduced into cells that are neither macrophages nor adipocytes, bound only to regions depleted of repressive histone modifications, where it increased DNA accessibility, enhanced histone acetylation, and induced gene expression. Thus, the cell-specificity of PPAR function is regulated by cell-specific chromatin accessibility, histone marks, and transcription factors. Genomic occupancy profiled by high throughput sequencing (ChIP-seq) from mouse macrophages for PPARgamma, PU.1, C/EBPbeta, H3K9Ace; and from 3T3-L1 adipocytes for PPARgamma and H3K9Ace Masking file used to subtract input bias areas prior to generating final peak lists is linked below.
Project description:PPARγ is a master transcriptional regulator of adipogenesis. Hence, the identification of PPARγ coactivators should help reveal mechanisms controlling gene expression in adipose tissue development and physiology. We show that the non-coding RNA Steroid receptor RNA Activator, SRA, associates with PPARγ and coactivates PPARγ-dependent reporter gene expression. Overexpression of SRA in ST2 adipocyte precursor cells promotes their differentiation into adipocytes. Conversely, knockdown of endogenous SRA inhibits 3T3-L1 preadipocyte differentiation. Microarray analysis reveals hundreds of SRA-responsive genes in adipocytes, including genes in cell cycle, insulin and TNFα signaling pathways. Some functions of SRA may involve mechanisms other than coactivation of PPARγ. SRA increases insulin-stimulated glucose uptake in adipocytes. SRA promotes S-phase entry during mitotic clonal expansion, decreases expression of cyclin-dependent kinase inhibiters p21Cip1 and p27Kip1, and increases phosphorylation of Cdk1/Cdc2. SRA also inhibits the TNFα-induced phosphorylation of c-Jun NH2-terminal kinase. In conclusion, SRA enhances adipogenesis and adipocyte function through multiple pathways. Total RNA was isolated from fully differentiated (MDIT day 4) SRA overexpressing (pMSCV-SRA) and control (pMSCV empty vector) ST2 adipocytes, or fully differentiated (MDIT day 8) shSRA knockdown (pSuperior-shSRA) or shControl (pSuperior-shcontrol) 3T3-L1 adipocytes. Genome wide gene expression analysis was performed using Affymetrix mouse genome 430 2.0 arrays. Triplicate samples were analyzed.
Project description:The transcriptional mechanisms by which temporary exposure to developmental signals instigates adipocyte differentiation are unknown. During early adipogenesis, we find transient enrichment of the glucocorticoid receptor (GR), CCAAT/enhancer binding protein b (CEBPb), p300, mediator subunit 1, and histone H3 acetylation near genes involved in cell proliferation, development and differentiation, including the gene encoding the master regulator of adipocyte differentiation, peroxisome proliferator activated receptor g2 (PPARg2). Occupancy and enhancer function are triggered by adipogenic signals, and diminish upon their removal. GR, which is required for adipogenesis but need not be active in the mature adipocyte, transiently functions with other enhancer proteins to propagate a new program of gene expression that includes induction of PPARg2, thereby providing a memory of the earlier adipogenic signal. Thus, the conversion of preadipocyte to adipocytes involves the formation of an epigenomic transition state that is not observed in cells at the beginning or end of the differentiation process. Genomic occupancy profiled by high throughput sequencing (ChIP-seq) from 3T3-L1 cells during differentiation for H3K9Ac, CEBPb and GR.
Project description:We profiled PPARg dependent gene expression changes during differntiation of 3T3L1 cell using PPARg siRNA 3T3-L1 (Pre-adipocyte) cell line was induced to differentiate using standard adipocyte differentiation media (IBMX, Dex and Insulin) 48hrs post-confluency. RNA was harvested at day -2 (confluent fibroblasts), 48hrs post-induction with IBMX, DEX and Insulin (day=0) and for each subsequent day after rosiglitazone treatment. Illumina beadchip microarrays were used to determine expression profiles of genes differentially regulated in cells transfected with either siRNA targeting PPARgamma or a non-targeting control siRNA. 3T3L1 cell were induced to differentiate into adipocytes using IBMX, DEX and Insulin. RNA from cell treated with PPARg-specific siRNA and non-specific siRNA was isolated at different timepoints. Illumina MouseRef-8 v1.1 Bead chips were used for expression profiling
Project description:Obesity is a major risk factor for the development of insulin resistance and type II diabetes. The nuclear receptors PPAR delta and PPAR gamma play a central role in regulating metabolism in adipose tissue, as well as being targets for the treatment of insulin resistance. The metabolic effects of PPAR delta and PPAR gamma activation have been examined both in vivo in white adipose tissue from ob/ob mice and in vitro in cultured 3T3-L1 adipocytes using a combined 1H NMR spectroscopy and mass spectrometry metabolomic methodology to understand the contrasting roles of these receptors. These steady state measurements were supplemented with 13C-stable isotope substrate labeling to assess fluxes, respirometry and transcriptomic microarray analysis. The metabolic effects of the two receptors were readily distinguished, with PPAR gamma activation characterised by increased fat storage and fat synthesis/elongation, while activation of PPAR delta caused increased fatty acid beta-oxidation, TCA cycle rate and oxidation of extracellular branch chain amino acids. Stimulated glycolysis and increased desaturation of fatty acids were the only common pathways. PPAR delta has a role as an anti-obesity target as well as an anti-diabetic. Total RNA obtained from cultured 3T3-L1 cells treated for 48 hours with either DMSO control, GW610742 PPARd agonist or GW347845 PPARg agonist and compared.
Project description:Visceral fat (VF) and subcutaneous fat (SF) are developmentally different tissues with different gene expression. Islet-1 (ISL1), a LIM-homeobox transcription factor with important developmental and regulatory function in islet, neural, and cardiac tissue, is virtually absent in SF but substantially expressed in the stromovascular [preadipocyte containing] fraction of VF; expression correlates negatively with adiposity in rodents and man. ISL1 expression is transiently increased in 3T3-L1 preadipocytes during early differentiation, suggesting a functional role. To examine the role of ISL1 in adipogenesis, we tested whether retroviral overexpression of ISL1 in 3T3-L1 preadipocytes affected their ability to differentiate into mature adipocytes. Terminal differentiation was assessed by Oil Red O [lipid droplet] staining and by immunoblot detection of adipocyte marker proteins, including aP2 and GLUT4. ISL1 significantly inhibited lipid droplet formation, reduced lipid accumulation (about 80% inhibition, p<0.05), and substantially inhibited aP2 and GLUT4 expression. ISL1 did not inhibit expression of C/EBPb and C/EBPd after induction of differentiation, but reduced PPARg and C/EBPa by >50% at both mRNA and protein level. In addition, the PPARg agonist, rosiglitazone, substantially rescued ISL1 inhibited adipogenesis in the absence of exogenous PPARg, and fully rescued in the presence of exogenous PPARg. In summary, ISL1 overexpression inhibited fat droplet formation, lipid accumulation, and adipocyte-specific gene expression; there was accompanying inhibition of C/EBPa, PPARg and downstream gene expression. We conclude that ISL1 overexpression inhibited adipocyte differentiation by inhibition of PPARg regulated gene expression. As abdominal obesity strongly correlates with insulin resistance, and cardiovascular risk, ISL1 up-regulation may impact abdominal obesity and its concomitant metabolic derangements. Total cellular RNA was isolated from 3T3-L1 cells expressing Flag-ISL1 or not at 48 h following treatment with differentiation cocktail. Individual RNA from biological triplicates was used for microarray analysis.
Project description:To examine the role of retinol binding protein 7 (RBP7) in PPAR gamma mediated regulation of target gene expression in the carotid artery, RNA-Seq was used to quantitate gene expression in carotid artery from both wild-type and RBP7 knockout mice after ligand-mediated activation of PPAR gamma with Rosiglitazone. Overall design: Carotid artery were removed from wild-type (WT) and RBP7 knockout (KO) mice and treated with either Rosliglitazone (ROSI, 10 uM) or vehicle DMSO (CONT) for 24 hrs.
Project description:Objective: To quantify changes in adipogenic gene expression in the presence of ritonavir (RTV) or tenofovir (TDF), and determine whether conjugated linoleic acid (CLA) isomers (cis9,trans11 or trans10,cis12) can mitigate detrimental effects of antiretoviral drugs. Methods: Affymetrix Mouse Genome 430 2.0 microarray was used to investigate gene expression in 3T3-L1 adipocytes treated with (1) RTV, TDF or ethanol control, or (2) ritonavir +c9,t11-CLA, ritonavir+t10,c12-CLA or ritonavir+DMSO control. RT-PCR validation of Pparg, Adipoq and Retn was carried out. ELISA and DNA binding ELISA were used to investigate secreted proteins and Pparg binding to its gene response element. Oil Red O staining was used to investigate triglyceride accumulation. Results: No effect was observed for TDF. Expression of 389 genes was altered more than 5-fold in the presence of RTV. Down-regulated genes included Pparg, Adipoq, Retn, Cfd and Cidec. Pparg and Adipoq down-regulation were confirmed by RT-PCR. PPAR-γ binding to its gene response element, adiponectin protein secretion and triglyceride accumulation were decreased by RTV. t10,c12-CLA in the presence of RTV decreased the expression of Ppargand Adipoq in microarray and RT-PCR. c9,t11-CLA increased PPAR-γ binding to its gene response element. Both isomers increased triglyceride storage in the presence of RTV. Conclusion: Ritonavir altered genes involved in adipocyte differentiation, lipid accumulation and glucose metabolism. Down-regulation of Pparg may be mediated by changes in Cepba and regulatory genes Pparg1c and Nr1h3. 3T3-L1 adipocytes were treated with ritonavir (20μM; n=4), tenofovir (1μM; n=4) or vehicle control (ethanol 0.1%; n=4) for 5 days and in a second experiment with ritonavir (20 µM) +c9,t11-CLA (100μM; n=4), ritonavir (20 µM) +t10,c12-CLA (100μM; n=4) or ritonavir+fatty acid vehicle control (DMSO 0.1%; n=4) for 5 days.