Menopausal estrogen (E2) replacement therapy increases the risk of estrogen receptor (ER)-positive epithelial ovarian cancers (EOC). Whether E2 is tumorigenic or promotes expansion of undiagnosed pre-existing disease is unknown. To determine E2 effects on tumor promotion, we developed an intraperitoneal mouse xenograft model using ZsGreen fluorescent ER- 2008 and ER+ PEO4 human EOC cells. Tumor growth was quantified by in vivo fluorescent imaging. In ER+ tumors, E2 significantly increased size, induced progesterone receptors, and promoted lymph node metastasis, confirming that ER are functional and foster aggressiveness. Laser captured human EOC cells from ER- and ER+ xenografted tumors were profiled for expression of E2-regulated genes. Three classes of E-regulated EOC genes were defined, but less than 10% were shared with E-regulated breast cancer genes. Since breast cancer selective ER modulators (SERM) are therapeutically ineffective in EOC, we suggest that our EOC-specific E-regulated genes can assist pharmacologic discovery of ovarian targeted SERM.
Tissue-specific pathways for estrogen regulation of ovarian cancer growth and metastasis.
Specimen part
View SamplesThe transcription factor MyoD can coax na?e fibroblasts or otherwise committed cells to adopt the skeletal muscle phenotype by activating the muscle gene expression program. Activation of muscle gene expression occurs in quantal steps with not all the target genes of MyoD being activated at the same time. Some genes are induced in the initial phases, others at later stages despite the fact that MyoD is present throughout the differentiation process. MyoD is post-translationally modified by phosphorylation, ubiquitination, and acetylation. Here, we have employed a model system in which MyoD and its non-acetylatable version were inducibly expressed in mouse embryonic fibroblasts derived from mice to investigate how MyoD acetylation may contribute to differential gene activation.
MyoD acetylation influences temporal patterns of skeletal muscle gene expression.
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View SamplesTemporal expression profiling was utilized to define transcriptional regulatory pathways in vivo in a mouse muscle regeneration model. Potential downstream targets of MyoD were identified by temporal expression, promoter data base mining, and gel shift assays; Slug and calpain 6 were identified as novel MyoD targets. Slug, a member of the snail/slug family of zinc finger transcriptional repressors critical for mesoderm/ectoderm development, was further shown to be a downstream target by using promoter/reporter constructs and demonstration of defective muscle regeneration in Slug null mice.
Slug is a novel downstream target of MyoD. Temporal profiling in muscle regeneration.
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View SamplesThe integration of positive and negative intra- and extra-cellular signals dictates whether a cell will proliferate or differentiate. While it is intuitive to speculate that nutrients availability may influence this alternative, a comprehensive complement of the molecular determinants involved in this process has not been elucidated yet. In this study, we will investigate how nutrients (glucose) affect skeletal myogenesis. C2C12 cells will be cultured in high glucose and low glucose conditions, and their differenciation will be studied.
Glucose restriction inhibits skeletal myoblast differentiation by activating SIRT1 through AMPK-mediated regulation of Nampt.
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View SamplesLoss of muscle mass occurs in a variety of diseases including cancer, chronic heart failure, AIDS, diabetes and renal failure, often aggravating pathological progression. Preventing muscle wasting by promoting muscle growth has been proposed as a possible therapeutic approach. Myostatin is an important negative modulator of muscle growth during myogenesis and myostatin inhibitors are attractive drug targets. However, the role of the myostatin pathway in adulthood and the transcription factors involved in the signaling are unclear. Moreover recent results confirm that other TGF members control muscle mass. Using genetic tools we perturbed this pathway in adult myofibers, in vivo, to characterize the downstream targets and their ability to control muscle mass. Smad2 and Smad3 are the transcription factors downstream of myostatin/TGF and induce an atrophy program which is MuRF1 independent and requires FoxO activity. Furthermore Smad2/3 inhibition promotes muscle hypertrophy independent of satellite cells but partially dependent of mTOR signalling. Thus myostatin and Akt pathways cross-talk at different levels. These findings point to myostatin inhibitors as good drugs to promote muscle growth during rehabilitation especially when they are combined with IGF1-Akt activators.
Smad2 and 3 transcription factors control muscle mass in adulthood.
Specimen part, Time
View SamplesTP53 is mutated in 50% of all cancers, and is often functionally compromised in cancers where it is not mutated. We demonstrate that the pro-tumorigenic/metastatic Six1 homeoprotein decreases p53 levels through a mechanism that does not involve the negative regulator of p53, MDM2. Instead, Six1 regulates p53 via a dual mechanism involving upregulation of microRNA-27a and downregulation of the ribosomal protein L26 (RPL26), a positive regulator of p53 translation. Mutation analysis confirms that RPL26, whose expression inversely correlates with Six1 expression in numerous tumor types, inhibits miR-27a binding to the p53 3UTR and prevents microRNA-mediated translational inhibition of p53. Thus, through simultaneous downregulation of RPL26 and upregulation of miR-27a, Six1 efficiently lowers p53 levels despite regulation of p53 at the level of the proteasome. Consequently, Six1 overexpression, which is observed in numerous tumor types, leads to dramatic resistance to nutlins, as well as other therapies targeting the p53-MDM2 interaction.
The Six1 oncoprotein downregulates p53 via concomitant regulation of RPL26 and microRNA-27a-3p.
Specimen part, Treatment
View SamplesMicroarrays have been widely used for the analysis of gene expression and several commercial platforms are available. The combined use of multiple platforms can overcome the inherent biases of each approach, and may represent an alternative that is complementary to RT-PCR for identification of the more robust changes in gene expression profiles.
Cross platform microarray analysis for robust identification of differentially expressed genes.
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View SamplesTo further understand the differences occurring in MCF10A cells as they polarize and differentiate in the Transwell model, we performed gene expression profiling with Affymetrix Human Genome U133 Plus 2.0 Arrays. Four experimental time points, were sampled: conventional cultures of MCF10A cells grown on plastic (Monolayer) and MCF10A cells plated on Transwells sampled at three TEER values, 200-300 cm2 (Base), 1400-1600 cm2 (Midpoint), and 3000-3200 cm2 (Plateau).
In vitro multipotent differentiation and barrier function of a human mammary epithelium.
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View SamplesEnhancers play a central role in cell-type-specific gene expression and are marked by H3K4me1/2. Active enhancers are further marked by H3K27ac. However, the methyltransferases responsible for the deposition of H3K4me1/2 on enhancers remain elusive. Furthermore, the functions of these methyltransferases on enhancers and associated cell-type-specific gene expression are poorly understood. Here, we identify MLL4 (KMT2D) as a major H3K4 mono- and di-methyltransferase in mammalian cells. Using adipogenesis and myogenesis as model systems, we show that MLL4 exhibits cell-type- and differentiation-stage-specific genomic binding and is predominantly localized on enhancers. MLL4 co-localizes with lineage-determining transcription factors (TFs) on active enhancers during differentiation. Deletion of MLL4 dramatically decreases H3K4me1/2 and H3K27ac on enhancers and leads to severe defects in cell-type-specific gene expression and cell differentiation. Finally, we provide evidence that lineage-determining TFs recruit and require MLL4 to establish enhancers critical for cell-type-specific gene expression. Together, these results identify MLL4 as an H3K4 mono-/di-methyltransferase required for enhancer activation during cell differentiation. Overall design: RNA-Seq analysis of mRNA profiles in adenoviral GFP- or Cre-infected MLL3-/-;MLL4-flox/flox cells. Preadipocytes: brown preadipocytes before differentiation. D5 myocytes: 5 days after MyoD-induced myogenesis of brown preadipocytes.
H3K4 mono- and di-methyltransferase MLL4 is required for enhancer activation during cell differentiation.
Specimen part, Subject
View SamplesSelective genetic ablation of the SIRT1 deacetylase domain in skeletal muscle results in increased H4K16 acetylation and deregulated activation of the myogenic program in satellite cells Overall design: To establish the role of the deacetylase SIRT1 in skeletal muscle we examined the genome wide distribution of H4K16ac in quiescent (FI) and proliferating (Cul) satellite cells isolated from WT mice (C57Bl/6 background) and SIRT1mKO (generated via breeding of Pax7cre/+ knock-in mice with mice containing the floxed exon 4 SIRT1 allele). We also analyzed the distribution of SIRT1 in quiescent and proliferating FACS isolated WT satellite cells (two replicates). We generated the mRNA profiles (at least two replicate for each experiment) of FACS isolated quiescent, proliferating and differentiating (1 day in differentiation medium) satellite cells of WT mice and SIRT1mKO. The selective genetic ablation of the SIRT1 deacetylase domain in skeletal muscle results in increased H4K16 acetylation and deregulated activation of the myogenic program.
The NAD(+)-dependent SIRT1 deacetylase translates a metabolic switch into regulatory epigenetics in skeletal muscle stem cells.
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