Coactosin-like F-actin Binding Protein (Cotl1) Plays a Key Role in Adipocyte Differentiation and Obesity
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ABSTRACT: Actin dynamics, mediated by various actin-binding proteins, plays an important role in adipocyte differentiation. We investigated the role of coactosin-like F-actin binding protein (Cotl1) in adipocyte differentiation in vitro and in vivo. Cotl1 expression level was increased during adipocyte differentiation in mouse 3T3-L1 cells and primary cultured adipose-derived stem cells (ADSCs) and during weight gain in adipose tissues. However, Cotl1 deficient in 3T3-L1 and ADSCs inhibited adipocyte differentiation, and Cotl1-/- mice displayed resistance to high-fat diet (HFD)-induced weight gain, hepatic steatosis and adipocyte enlargement compared to HFD-fed wild type (WT) mice. Ingenuity Pathway Analysis of RNA-sequencing in adipose tissues of HFD-WT and HFD-Cotl1-/- mice predicted complicated relationships between Cotl1, differentiation of adipocytes, obesity and organization of actin cytoskeleton. Particularly, peroxisome proliferator-activated receptor gamma (Pparg) emerged as a central player, with Cotl1 influencing Pparg expression, consequently regulating adipocyte differentiation. These findings suggest Cotl1 as a pivotal regulator of terminal adipocyte differentiation by modulating adipogenic genes.
Project description:Obesity due to overnutrition causes adipose tissue dysfunction, serving as a critical pathological step on the road to Type 2 diabetes (T2D) and other metabolic disorders. Here, we performed an unbiased investigation into the fundamental molecular mechanisms by which adipocytes transition to an unhealthy state during obesity. We fed NuTRAP (Nuclear tagging and Translating Ribosome Affinity Purification) mice crossed with Adipoq-Cre with chow or high fat diet (HFD) for 10 weeks and determined adipocyte-specific transcriptomic profiles by RNA-seq, active promoter and enhancer activities by H3K27ac ChIP-seq, and the PPARg cistrome by ChIP-seq. We also assessed the impact of the PPARg agonist rosiglitazone (Rosi) on gene expression and cellular state of adipocytes from HFD-fed mice. We used bioinformatic approaches to find transcriptional pathways and performed functional studies using shRNA-mediated loss-of-function approaches in 3T3-L1 adipocytes. Adipocytes from HFD-fed mice exhibited reduced expression of adipocyte markers and metabolic genes while showing enhanced expression of myofibroblast marker genes involved in cytoskeletal organization, accompanied by the formation of actin filament structures within the cell. PPARg binding was globally reduced in adipocytes after HFD feeding, and Rosi restored the molecular and cellular phenotypes of adipocytes associated with HFD feeding. SMAD binding motifs were over-represented in HFD-induced promoters and enhancers, while TGFb1 expression was elevated in adipose tissues after HFD feeding. TGFb1 treatment of mature 3T3-L1 adipocytes induced gene expression and cellular changes similar to those seen after HFD in vivo, and knockdown of Smad3 blunted the effects of TGFb1. Our data demonstrate that adipocytes fail to maintain cellular identity after HFD, acquiring characteristics of a myofibroblast-like cell type through reduced PPARg activity and elevated TGFb-SMAD signaling. This cellular identity crisis may serve as a fundamental mechanism that drives functional decline of adipose tissues during obesity.
Project description:The LIM-domain-only protein FHL2 is a modulator of signal transduction and has been shown to direct the differentiation of mesenchymal stem cells toward osteoblasts and myocytes phenotypes. We hypothesized that FHL2 may simultaneously interfere with the induction of the adipocyte lineage. Therefore, we investigated the role of FHL2 in adipocyte differentiation using pre-adipocytes isolated from mouse adipose tissue and the 3T3-L1 (pre)adipocyte cell line. Here we report that FHL2 is expressed in pre-adipocytes and for accurate adipocyte differentiation, this protein needs to be downregulated during the early stages of adipogenesis. More specifically, constitutive overexpression of FHL2 drastically inhibits adipocyte differentiation in 3T3-L1 cells, which was demonstrated by suppressed activation of the adipogenic gene expression program as shown by extensive RNAseq analyses, and diminished lipid accumulation. To identify the protein-protein interactions mediating this repressive activity of FHL2 on adipogenesis, we performed affinity-purification mass spectrometry (AP-MS). This analysis revealed the interaction of FHL2 with the Nuclear factor of activated T-cells 5 (NFAT5), an established inhibitor of adipocyte differentiation. NFAT5 knockdown rescued the inhibitory effect of FHL2 overexpression on 3T3-L1 differentiation, indicating that these proteins act cooperatively. In conclusion, we present a new regulatory function of FHL2 in early adipocyte differentiation and revealed that FHL2-mediated inhibition of pre-adipocyte differentiation is dependent on its interaction with NFAT5.
Project description:Cebpa is a critical transcription factor gene for adipocyte differentiation and adipose tissue development. However, mechanisms controlling Cebpa expression during adipogenic differentiation remain largely unknown. Here, we generated the high-resolution chromatin interaction maps of Cebpa in 3T3-L1 preadipocytes (3T3-L1) and 3T3-L1 adipocytes (3T3-L1-AD) using circularized chromosome conformation capture coupled with next-generation sequencing (4C-seq), and characterized differences in their chromatin interactomes and chromatin status of the interaction sites during adipogenic differentiation. We performed a 4C-seq experiment on inguinal white adipose tissue (iWAT) to evaluate whether chromatin interaction between Cebpa-L1-AD-En2 and Cebpa promoters in 3T3-L1 adipocytes also exists in mouse adipose tissue.
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:This SuperSeries is composed of the following subset Series:; GSE8679: Gene expression in mouse white adipose tissue; GSE8681: Gene expression in mouse 3T3-L1 adipocyte tissue culture treated with CLA; GSE8682: Gene expression in mouse 3T3-L1 adipocyte tissue culture treated with tunicamycin; GSE8683: Gene expression in 3T3-L1 mouse tissue (preadipocytes) treated with Trans-10,Cis-12 conjugated linoleic acid(t10c12 CLA); GSE8684: Gene expression in mouse 3T3-L1 adipocyte tissue culture treated with cis-9,trans-11 conjugated linoleic acid(c9t11 CLA) Experiment Overall Design: Refer to individual Series
Project description:3T3-L1 pre-adipocyte cells were grown to confluence and induced to differentiate in adipogenic media. Examination of 6 histone modifications and CTCF at 4 time points and PPARG at 1 time point using ChIP-Seq
Project description:Genome-wide profiling of PPAR?:RXR and RNA polymerase II reveals temporal activation of distinct metabolic pathways in RXR dimer composition during adipogenesis. Chromatin immunoprecipitation combined with deep sequencing was performed to generate genome-wide maps of peroxisome prolifelator-activated receptor gamma (PPARg) and retinoid X receptor (RXR) binding sites, and RNA polymerase II (RNAPII) occupancy at high resolution throughout adipocyte differentiation of 3T3-L1 cells. The data provides the first positional and temporal map PPAR? and RXR occupancy during adipocyte differentiation at a global scale. The number of PPAR?:RXR shared binding sites is steadily increasing from D0 to D6. At Day6 there are over 5000 high confidence shared PPARy:RXR binding sites. We show that at the early days of differentiation several of these sites bind not only PPAR?:RXR but also other RXR dimers. The data also provides a comprehensive temporal map of RNAPII occupancy at genes throughout 3T3-L1 adipogenesis thereby uncovering groups of similarly regulated genes belonging to glucose and lipid metabolic pathways. The majority of the upregulated but very few downregulated genes have assigned PPAR?:RXR target sites, thereby underscoring the importance of PPAR?:RXR in gene activation during adipogenesis and indicating that a hitherto unrecognized high number of adipocyte genes are directly activated by PPAR?:RXR Examination of PPARg and RXR bindingsites during adipocyte differentiation (day 0 to 6) and association with transcription via RNAPII occupancy.
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.
Project description:Cellular differentiation is regulated through activation and repression of defined transcription factors. A hallmark of differentiation is a pronounced change in cell shape, which is determined by dynamics of the actin cytoskeleton. In de-differentiated fat (DFAT) cells and 3T3-L1 cells, we showed that treatment with the ROCK inhibitor Y-27632, by inducing remodeling of the actin cytoskelton, causes adipocyte differentiation. In addition, we found that depletion of MKL1, an actin binding transcriptional coactivator, elicits adipogenesis. To investigate whether regulation of MKL1 by actin cytoskeleton dynamics drives adipocyte differentiation, we compared the gene expression changes resulting from DFAT cells after treatment with Y-27632 and transfection of Mkl1 siRNA.