Project description:ChIP sequencing was used to generate genome-wide maps of the histone mark H3K27ac during in vitro differentiation of a murine brown preadipocyte cell line (IBA) at five different time points, in two biological replicates: Day 0 (confluence), 2h (post induction), Day 1, Day 2 and Day 4 (mature brown adipocytes). Additionally, transcription factor (TF) localisation maps of the Nuclear Factor 1 (NFI) were generated using ChIP sequencing at two time points: Day 0 and Day 4.
Project description:Much of our knowledge on adipogenesis comes from cell culture models of preadipocyte differentiation. Adipogenesis is induced by treating confluent preadipocytes with the adipogenic cocktail, which activates transcription factors (TFs) glucocorticoid receptor (GR) and CREB within minutes and increases expression of TFs C/EBPb/d, KLF4 and Krox20 within hours. All of these TFs have been shown to be capable of promoting adipogenesis in culture when they are overexpressed. However, it has remained unclear whether endogenous KLF4 and Krox20 are required for adipogenesis in culture and in vivo. Using conditional knockout mice and derived white and brown preadipocytes, we show that endogenous KLF4 and Krox20 are dispensable for adipogenesis in culture and brown adipose tissue development in mice. In contrast, the master adipogenic TF PPARg is essential. These results challenge the existing model on transcriptional regulation in the early phase of adipogenesis and highlight the need of studying adipogenesis in vivo.
Project description:Insulin and IGF-1 promote adipocyte differentiation via complex and overlapping signalling networks. Here we used microarray analysis of brown preadipocytes derived from wild-type and insulin receptor substrate (IRS) knockout (KO) animals, which exhibited progressively impaired differentiation, to define the set of genes that predict adipogenic potential in these cells. 374 genes/ESTs were identified whose expression in preadipocytes correlated with their ultimate ability to differentiate. Many of these genes were related to early adipogenic events, including genes involved in extracellular matrix, cytoskeletal organization, growth arrest, post-mitotic clonal expansion, and inhibitors of adipogenesis, including preadipocyte factor-1 and multiple members of the Wnt-signalling pathway. Reconstitution of IRS-1 KO cells with IRS-1 reversed these changes and restored the ability to differentiate. Several of these genes showed concordant changes in brown adipose tissue in vivo. Necdin was markedly increased in IRS-1 KO cells that could not differentiate, and knockdown of necdin restored brown adipogenesis with down-regulation of Pref-1 and Wnt10a expression. We demonstrated a necdin-E2F4 interaction repressing PPARg transcription. IRS proteins regulated necdin via a CREB dependent pathway, defining a signalling network involved in brown preadipocyte determination.
Project description:Insulin and IGF-1 promote adipocyte differentiation via complex and overlapping signalling networks. Here we used microarray analysis of brown preadipocytes derived from wild-type and insulin receptor substrate (IRS) knockout (KO) animals, which exhibited progressively impaired differentiation, to define the set of genes that predict adipogenic potential in these cells. 374 genes/ESTs were identified whose expression in preadipocytes correlated with their ultimate ability to differentiate. Many of these genes were related to early adipogenic events, including genes involved in extracellular matrix, cytoskeletal organization, growth arrest, post-mitotic clonal expansion, and inhibitors of adipogenesis, including preadipocyte factor-1 and multiple members of the Wnt-signalling pathway. Reconstitution of IRS-1 KO cells with IRS-1 reversed these changes and restored the ability to differentiate. Several of these genes showed concordant changes in brown adipose tissue in vivo. Necdin was markedly increased in IRS-1 KO cells that could not differentiate, and knockdown of necdin restored brown adipogenesis with down-regulation of Pref-1 and Wnt10a expression. We demonstrated a necdin-E2F4 interaction repressing PPARg transcription. IRS proteins regulated necdin via a CREB dependent pathway, defining a signalling network involved in brown preadipocyte determination. Keywords = brown fat Keywords = preadipocyte Keywords = adipogenesis Keywords = mouse Keywords: parallel sample
Project description:Brown adipose tissue (BAT) holds therapeutic potential for obesity and metabolic syndrome via increasing energy expenditure. Both inter- and intra-individual differences contribute to heterogeneity in human BAT and potentially to differential thermogenic capacity in human populations. Here, we demonstrated the generation of brown and white preadipocyte clones from human neck fat and characterized their adipogenic differentiation and thermogenic function. Combining a UCP1 reporter system and gene expression profiling, we defined novel sets of gene signatures in human preadipocytes that could predict the thermogenic potential of mature adipocytes. Knocking out the positive UCP1 regulators, PREX1 and EDNRB, in brown preadipocytes by CRISPRs markedly abolished the high level of UCP1 in mature brown adipocytes. Finally, we showed the ability to prospectively isolate adipose progenitors with great thermogenic potential. These data provide new insights into the cellular heterogeneity in human fat and offer clinically relevant gene targets that mark thermogenically competent preadipocytes. Highly adipogenic clonal white and brown cell lines
Project description:Increasing energy expenditure by promoting the thermogenic program in brown adipocytes is a promising approach to combat human obesity. To fully exploit the potential of this approach a comprehensive understanding of the gene regulatory network that controls both lineage commitment and differentiation of brown cells is necessary. Here, we systematically examine the transcriptomic and epigenomic transitions from mesenchymal stem cells to brown adipocytes (BA) and we perform a comparative analysis with differentiating white adipocytes (WA). We identify coding genes, lncRNA genes, and microRNA genes that are differentially regulated upon BA differentiation. In addition, we generate genome wide reference maps for several chromatin marks throughout brown adipogenesis. We identify putative (super-)enhancers, super-enhancers controlled genes in brown and white adipocytes, as well as target genes of the brown lineage-committing factor BMP7. Finally we show that overexpression and knockdown of four putative novel adipogenic regulators (the kinase Pim1, and the transcription factors Six1, Rreb1, and Sox13), indeed affects BA differentiation, suggesting an important role in brown adipogenesis.
Project description:Attainment of a brown adipocyte cell phenotype in white adipocytes, with their abundant mitochondria and increased energy expenditure potential, is a legitimate strategy for combating obesity. The unique transcriptional regulators of the primary brown adipocyte phenotype are unknown, limiting our ability to promote brown adipogenesis over white. In the present work, we used microarray analysis strategies to study primary preadipocytes, and we made the striking discovery that brown preadipocytes demonstrate a myogenic transcriptional signature, whereas both brown and white primary preadipocytes demonstrate signatures distinct from those found in immortalized adipogenic models. We found a plausible SIRT1-related transcriptional signature during brown adipocyte differentiation that may contribute to silencing the myogenic signature. In contrast to brown preadipocytes or skeletal muscle cells, white preadipocytes express Tcf21, a transcription factor that has been shown to suppress myogenesis and nuclear receptor activity. In addition, we identified a number of developmental genes that are differentially expressed between brown and white preadipocytes and that have recently been implicated in human obesity. The interlinkage between the myocyte and the brown preadipocyte confirms the distinct origin for brown versus white adipose tissue and also represents a plausible explanation as to why brown adipocytes ultimately specialize in lipid catabolism rather than storage, much like oxidative skeletal muscle tissue. Experiment Overall Design: Comparisons of white and brown pre- and mature-adiposytes