To dissect regulatory processes of cell proliferation and differentiation we generated mouse strains carrying any combination of the four Stat5 alleles, thus expressing STAT5 from 0 to 100%. RNA-Seq analyses revealed that different STAT5 levels activate specific genetic programs linked to cell proliferation and differentiation. Overall design: We refer to wild-type mice and Stat5abfl/fl mice as AABB mice; Stat5abfl/fl;MMTV-Cre (with Stat5ab-deficient mammary epithelial cells) as Null mice; Stat5a-/- mice as BB mice; Stat5b-/- mice as AA mice; Stat5ab+/null mice as AB mice.
Sequential activation of genetic programs in mouse mammary epithelium during pregnancy depends on STAT5A/B concentration.
Specimen part, Cell line, Subject
View SamplesThe mammary luminal lineage relies on the common cytokine-sensing transcription factor STAT5 to establish super-enhancers during pregnancy and activate mammary genes required for the nutrition of the offspring. Exploiting progressive differentiation during lactation, we investigated how hormonal cues shape an evolving enhancer landscape and impact the biology of mammary cells. Employing ChIP-seq, we uncover a changing transcription factor occupancy at mammary enhancers. Using mouse genetics, we demonstrate changing biological properties of enhancers as lactation progresses, with individual enhancers gaining strength and an abolished need for the Wap seed enhancer. We further investigated whether permissive chromatin facilitates cell-specific transcription factor binding. Wap enhancers translocated into the widely expressed neighboring Ramp3 gene retained their mammary-specificity and failed to activate the receptive Ramp3 gene in non-mammary tissues. Our studies unveil a previously unrecognized progressive enhancer landscape, in which structurally equivalent components serve unique and differentiation-specific functions. While enhancer redundancy has been suggested and demonstrated for many genes, components of the cytokine-responsive mammary tripartite Wap super-enhancer display a remarkable specificity. Overall design: Total RNA-seq was done for mammary tissues at day one and ten of lactation.
Progressing super-enhancer landscape during mammary differentiation controls tissue-specific gene regulation.
Specimen part, Subject
View SamplesMammary alveologenesis is abrogated in the absence of the transcription factors STAT5A/5B that mediate cytokine signaling. To reveal the underlying causes for this developmental block we studied mammary stem and progenitor cells. While loss of STAT5A/5B did not affect the stem cell population and their ability to form mammary ducts, luminal progenitors were greatly reduced and unable to form alveoli during pregnancy. Temporally-controlled expression of transgenic STAT5A in mammary epithelium lacking STAT5A/5B restored the luminal progenitor population and rescued alveologenesis in a reversible fashion in vivo. Taken together, STAT5A is necessary and sufficient for the establishment of luminal progenitor cells.
Development of mammary luminal progenitor cells is controlled by the transcription factor STAT5A.
Specimen part
View SamplesAlthough the cytokine-inducible transcription factors STAT5a/b promote proliferation of a wide range of cell types, there are cell- and context specific cases in which loss of STAT5a/b results in enhanced cell proliferation. Here we report that loss of STAT5a/b from mouse embryonic fibroblasts (MEFs) leads to enhanced proliferation, which was linked to reduced levels of the cell cycle inhibitor p15INK4B and p21CIP1. We further demonstrate that growth hormone through the transcription factor STAT5a/b enhances expression of the cdkn2B gene and that STAT5a binds to GAS sites within the promoter. We have recently demonstrated that ablation of STAT5a/b from liver results in hepatocellular carcinoma upon a CCl4 insult. We also established that in liver tissue, like in MEFs, STAT5a/b activates expression of the cdkn2B gene. Loss of STAT5a/b led to diminished p15INK4B and increased hepatocyte proliferation. This study for the first time demonstrates that cytokines through STAT5a/b can induce the expression of a key cell cycle inhibitor. These experiments therefore shed a light on the context-specific role of STAT5a/b as tumor suppressors.
The transcription factors signal transducer and activator of transcription 5A (STAT5A) and STAT5B negatively regulate cell proliferation through the activation of cyclin-dependent kinase inhibitor 2b (Cdkn2b) and Cdkn1a expression.
Specimen part
View SamplesPrecise spatiotemporal regulation of genetic programs, driven by cellspecific super-enhancers, is paramount for the function of cell lineages. Studies have suggested that insulated neighborhoods, formed by the zincfinger protein CTCF, sequester genes and their associated enhancers thus preventing them from trespassing on off-target genes. Although this could explain the enhancer-gene-specificity conundrum, there is limited genetic evidence that the search space of cell-specific super-enhancers is constrained by CTCF. We have addressed this question in the Wap locus with its exceptional mammary-specific super-enhancer, which is separated by five CTCF sites from neighboring genes. Three of these sites are positioned between the Wap super-enhancer and the widely expressed Ramp3. Enhancer deletions demonstrated that the Wap super-enhancer controls Ramp3 expression despite the presence of three parting CTCF sites. Individual and combinatorial deletions of these CTCF sites revealed cell-specific functions of the conserved anchor site. Although unable to block super-enhancer activity, it muffled its impact on Ramp3 in mammary tissue. Unexpectedly, this CTCF site was obligatory for Ramp3 expression in cerebellum, suggesting the coinciding presence of regulatory elements. While our results suggest a surprisingly limited in vivo role for a CTCF anchor in blocking a mammary-specific super-enhancer, they also implicate this site in cerebellum-specific gene activation. Our study illustrates additional complexities of CTCF sites supporting tissue-specific functions. Overall design: Total RNA-seq was done for mammary tissue at pregnancy day 18.
Facultative CTCF sites moderate mammary super-enhancer activity and regulate juxtaposed gene in non-mammary cells.
Specimen part, Cell line, Subject
View SamplesAlthough epigenetic mechanisms, such as specific histone modifications, control common and cell-specific genetic programs, a role for histone modifying enzymes in liver metabolism and disease has not been investigated. This report demonstrates that the combined loss of the histone methyltransferases EZH1 and EZH2 in mouse hepatocytes led to the disruption of H3K27me3 homeostasis by age three months, simple fatty liver by age six months and fatal fibrosis by age 15 months. Global and gene-specific reduction of H3K27me3 marks paralleled a concomitant increase of H3K4me3 marks at genes associated with chronic liver disease. Advanced disease was accompanied by widespread infiltration of immune cells, an increase of activated hepatic stellate cells and collagen deposition. Expression of genes from the cytochrome P450 family that control drug metabolism was already deregulated by age two months and mice were fatally hypersensitive to carbon tetrachloride (CCl4). These genetic experiments, for the first time, illustrate that the simple loss of EZH1/EZH2, which results in the disruption of epigenetic modifications, is sufficient for the progression of fatal liver disease. Overall design: RNA-seq and ChIP-seq were performed in liver tissues.
The methyltransferases enhancer of zeste homolog (EZH) 1 and EZH2 control hepatocyte homeostasis and regeneration.
No sample metadata fields
View SamplesStat5+/- mice were bred into the C57BL/6 background. Stat5+/- mice were intercrossed and mouse embryonic fibroblasts (MEFs) were isolated from 12.5-13.5-day WT or Stat5-/- fetuses. The retroviral-expression vector carrying a wild-type Stat5A gene based on an MSCV-IRES-GFP backbone (gift from Richard Moriggl, Ludwig-Boltzmann Institute, Vienna, Austria) was infected into Stat5-/- MEFs. FACS was used to select GFP+ cells. After 5 hours starvation in serum free medium with 0.1% of BSA, MEFs were treated with growth hormone for 2 hours. Total cellular RNA from each group of the MEFs was extracted with TRIzol reagent (Invitrogen) according to the manufacturer's instructions. Microarray analyses were performed using Affymetrix Mouse Genome 430 2.0 GeneChips (Affymetrix, Santa Clara, CA) (six groups, biological replicates for each group). Expression values were determined with GeneChip Operating Software (GCOS) v1.1.1 software. RMA signals were summarized using GeneSpring GX 10.0.1 (Agilent) and normalized by quantile normalization. All data analysis was performed with GeneSpring software GX 10.01.
Genome-wide analyses reveal the extent of opportunistic STAT5 binding that does not yield transcriptional activation of neighboring genes.
Specimen part
View SamplesIron is essential for all cells but is toxic in excess, so iron absorption and distribution are tightly regulated. Serum iron is bound to transferrin and primarily enters erythroid cells via receptor-mediated endocytosis of the transferrin receptor (Tfr1). Tfr1 is essential for developing erythrocytes and reduced Tfr1 expression is associated with anemia. The transcription factors STAT5A/B are activated by many cytokines, including erythropoietin. Stat5a/b-/- mice are severely anemic and die perinatally, but no link has been made to iron homeostasis. To study the function of STAT5A/B in vivo, we deleted the floxed Stat5a/b locus in hematopoietic cells with a Tie2-Cre transgene. These mice exhibited microcytic, hypochromic anemia, as did lethally irradiated mice transplanted with Stat5a/b-/- fetal liver cells. Flow cytometry and RNA analyses of erythroid cells from mutant mice revealed a 50% reduction in Tfr1 mRNA and protein. We detected STAT5A/B binding sites in the first intron of the Tfr1 gene and found that expression of constitutively active STAT5A in an erythroid cell line increased Tfr1 levels. Chromatin immunoprecipitation experiments confirmed the binding of STAT5A/B to these sites. We conclude that STAT5A/B is an important regulator of erythroid progenitor iron uptake via its control of Tfr1 transcription.
Hematopoietic-specific Stat5-null mice display microcytic hypochromic anemia associated with reduced transferrin receptor gene expression.
No sample metadata fields
View SamplesGM-CSF controls the development of granulocytes but little is known about the contribution of the downstream mediating transcription factor STAT5A/B. To elucidate this pathway, we generated mice lacking the Stat5a and 5b genes in blood cells. Peripheral neutrophils were decreased and administration of 5-FU and GM-CSF failed to induce granulopoiesis in Stat5a/b-mutant mice. GMPs were isolated and cultured with GM-CSF. Both the number and size of STAT5A/B-null colonies were reduced and GM-CSF-induced survival of mature STAT5A/B-null neutrophils was impaired. Time-lapse cinematography and single cell tracking of GMPs revealed that STAT5A/B-null cells were characterized by a longer generation time and an increased cell death. Gene expression profiling experiments suggested that STAT5A/B directs GM-CSF signaling through the regulation of cell survival genes.
The transcription factors STAT5A/B regulate GM-CSF-mediated granulopoiesis.
No sample metadata fields
View SamplesPurpose: Among the diverse cytokines involved in osteoclast differentiation, IL-3 has been shown to inhibit RANKL-induced osteoclastogenesis. However, the mechanism underlying IL-3-mediated inhibition of osteoclast differentiation is not fully understood. In the present study, we demonstrate that IL-3 activation of STAT5 inhibits RANKL-induced osteoclastogenesis through the induction of Id genes. Methods: To investigate the effect of STAT5 on osteoclast differentiation and IL-3-mediated inhibition of osteoclast differentiation, bone marrow derived macrophages isolated from STAT5 wild-type (Stat5fl/fl) or STAT5 cKO (STAT5;MX1-Cre) were differentiated to osteoclast in the presence of M-CSF and RANKL with or without IL-3; and bone marrow derived macrophges from STAT5 wild-type and STAT5 cKO were overexpressed with PMX-FIG (control) or STAT5A1*6 (constitutively active form of STAT5A) and differentiated to osteoclast. To analyze bone phenotype, femurs and tibiae of 16 week-old STAT5 wild-type and STAT5 cKO were subjected to micro CT analysis and histomorphometry, respectively. Results: Overexpression of STAT5 inhibited RANKL-induced osteoclastogenesis. However, RANKL did not regulate either expression or activation of STAT5 during osteoclast differentiation. STAT5 deficiency prevented IL-3-mediated inhibition of osteoclastogenesis, suggesting that STAT5 plays an important role in IL-3-mediated inhibition of osteoclast differentiation. In addition, IL-3-induced STAT5 activation upregulated expression of the Id1 and Id2 genes, which are negative regulators of osteoclastogenesis. Overexpression of ID1 or ID2 in STAT5-deficient cells reversed osteoclast development recovered from IL-3-mediated inhibition. Moreover, micro-computed tomography and histomorphometric analysis revealed that STAT5 conditional knockout mice showed reduced bone mass, with an increased number of osteoclasts. Furthermore, IL-3 inhibited RANKL-induced osteoclast differentiation less effectively in STAT5 conditional knockout mice than in wild-type mice in a RANKL injection model. Conclusion: Taken together, our results suggest that STAT5 is a key transcription factor for IL-3-mediated inhibition of RANKL-induced osteoclastogenesis through Id gene expression. Overall design: Examination of 4 different combination of osteoclast differentiation condition of bone marrow derived macrophages.
STAT5 is a key transcription factor for IL-3-mediated inhibition of RANKL-induced osteoclastogenesis.
Sex, Age, Specimen part, Cell line, Subject
View Samples