Leukemogenic MLL-ENL fusions induce alternative chromatin states to drive a functionally dichotomous group of target genes
Ontology highlight
ABSTRACT:
INSTRUMENT(S): Illumina HiSeq 2500
ORGANISM(S): Mus musculus
SUBMITTER: Robert Slany
PROVIDER: E-MTAB-3593 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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2012-11-02 | E-MEXP-3648 | biostudies-arrayexpress
Project description:MLL encodes a histone methyltransferase that is critical in maintaining gene expression during embryonic development and hematopoiesis. 11q23 translocations encode chimeric MLL fusions that act as potent drivers of acute leukemia. However, it remains unclear what portion of the leukemic genome is under the direct control of the MLL fusion protein. By comparing patient-derived leukemic cell lines, we find that MLL fusion-bound genes are a small subset of that recognized by wild-type MLL. In an inducible MLL-ENL cellular model, binding of the MLL fusion protein and changes in H3K79 methylation are limited to a specific portion of the genome, whereas wild-type MLL distributes to a much larger set of gene loci. Surprisingly, among 223 MLL fusion-bound genes, only 12 demonstrate a significant increase in mRNA expression upon induction of the fusion protein. In addition to Hoxa9 and Meis1, this includes Eya1 and Six1 which comprise a heterodimeric transcription factor important in several developmental pathways. We show that Eya1 has the capacity to immortalize hematopoietic progenitor cells in vitro and collaborates with Six1 in hematopoietic transformation assays. Altogether, our data suggest that MLL fusions contribute to the development of acute leukemia through direct activation of a small set of target genes. We explored an inducible MLL-ENL cellular model, which was obtained from Dr. Robert Slany (University Erlangen, Germany). We wished to examine the differential expressed genes that are bound by MLL wild type (No 4-OHT) and fusion (4-OHT) proteins, combinding the ChIP-chip data to explore the potential MLL fusion-regulated genes.
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Project description:Translocations involving the MLL genes are frequently found in Acute Myeloid Leukemia (AML) and are associated with poor prognosis. The MLL fusion proteins act as aberrant transcription factor activating a transcriptional program that transforms the cells, potentially through collaboration with other transcription factors. To investigate this we searched gene expression profiles from patients with MLL-rearranged AML compared with normal hematopoietic progenitor cells for transcriptional regulators and found targets of C/EBPα to be up-regulated in the AML samples, suggesting that C/EBPα might collaborate with MLL fusion proteins in the initial transformation process. We could show that transformation by MLL fusion proteins is dependent on C/EBPα activity both in early progenitors as well as in GMPs. In contrast, C/EBPα was found to be indispensable in an already established leukemia. These results suggest that C/EBPα play an important role in the early transforming event of leukemogenesis. We used microarray to study the early transcriptional changes induced by MLL-ENL expression and we identified a combined C/EBPα / MLL-ENL transcriptional signature. 3 Cebpaflox/flox;Mx1Cre and 3 Cebpaflox/flox;Mx1Cre- mice were sacrificed 14 days after pIpC injection and bone marrow cells were harvested, enriched for cKit-expression and transduced with a pMIG retroviral vector expressing the MLL-ENL fusion protein and GFP. 72 h post first transduction, GFP-positive or negative PreGM cells were sorted.
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2015-11-03 | E-GEOD-72801 | biostudies-arrayexpress
Project description:Background: Clinical trial and epidemiological data support that the cardiovascular effects of estrogen are complex, including a mixture of both potentially beneficial and harmful effects. In animal models, estrogen protects females from vascular injury and inhibits atherosclerosis. These effects are mediated by estrogen receptors (ERs), which when bound to estrogen can bind to DNA to directly regulate transcription. ERs can also activate several cellular kinases by inducing a M-bM-^@M-^\rapidM-bM-^@M-^] non-nuclear signaling cascade. However, the biologic significance of this rapid signaling pathway has been unclear. Methods and Results: Here, we develop a novel transgenic mouse in which rapid signaling is blocked by over-expression of a peptide that prevents ERs from interacting with the scaffold protein, striatin (the Disrupting Peptide Mouse, DPM). Microarray analysis of ex vivo-treated mouse aortas demonstrates that rapid ER signaling plays an important role in E2-mediated gene regulatory responses. Disruption of ER-striatin interactions also eliminates the ability of E2 to stimulate cultured endothelial cell migration and to inhibit cultured vascular smooth muscle cell growth. The importance of these findings is underscored by in vivo experiments demonstrating loss of estrogen-mediated protection against vascular injury in the DPM mouse following carotid artery wire injury. Conclusions: Taken together, these results support that rapid, non-nuclear ER signaling contributes to the transcriptional regulatory functions of ER, and is essential for many of the vasoprotective effects of estrogen. These findings also identify the rapid ER signaling pathway as a potential target for the development of novel therapeutic agents. Transgenic disrupting peptide mice (DPM) express the Estrogen Receptor (ER) alpha amino acids 176-253 peptide under CMV promoter control. This peptide blocks interactions between ER and striatin, which inhibits rapid non-genomic signaling by ER to cellular kinases. Female WT and DPM mice (4 mice per sample) were overiectomized, and 1 week later aortas were harvested and treated + 10 nM beta-estradiol (E2) or + EtOH vehicle (Veh) for 4 hrs ex vivo. Total RNA was collected, reverse transcribed to cDNA and used to probe Affymetrix mouse 430.A 2.0 arrays.
2012-09-01 | E-GEOD-35558 | biostudies-arrayexpress
Project description:Chromosomal rearrangements involving the mixed-lineage leukemia (MLL) gene occur in primary and treatment-related leukemias, and confer a poor prognosis. Studies based primarily on mouse models have substantially advanced our understanding of MLL leukemia pathogenesis, but often employ supra-physiologic oncogene expression with uncertain implications for human leukemia. Genome editing using site-specific nucleases provides a powerful new technology for gene modification to potentially model human disease, however this approach has not been used to recreate acute leukemia in human cells of origin comparable to disease observed in patients. We applied TALEN-mediated genome editing to generate endogenous MLL-AF9 and MLL-ENL oncogenes through insertional mutagenesis in primary human hematopoietic stem and progenitor cells (HSPCs) derived from human umbilical cord blood. Engineered HSPCs displayed altered in vitro growth potentials and induced acute leukemias following transplantation in immuno-compromised mice at a mean latency of 14.5 weeks. The leukemias displayed phenotypic and morphologic similarities with patient leukemia blasts including a subset with mixed phenotype, a distinctive feature seen in clinical disease. The leukemic blasts expressed an MLL-associated transcriptional program with elevated levels of crucial MLL target genes, displayed heightened sensitivity to DOT1L inhibition, and demonstrated increased oncogenic potential ex vivo and in secondary transplant assays. Thus, genome editing to create endogenous MLL oncogenes in primary human HSPCs faithfully models acute MLL-rearranged leukemia and provides an experimental platform for prospective studies of leukemia initiation and stem cell biology in a genetic subtype of poor prognosis leukemia. BM cells (sorted for hCD45) of leukemic mice (ALL) were used for global gene expression measurement using Affymetrix Microarray GeneChip platform (HG-U133 Plus 2.0). The data together with those from 70 MLL patients (ALL) and 6 control samples (same GeneChip platform) from the leukemia study group were used for unsupervised hierarchical clustering analysis Haferlach T, Kohlmann A, Wieczorek L, et al. Clinical utility of microarray-based gene expression profiling in the diagnosis and subclassification of leukemia: report from the International Microarray Innovations in Leukemia Study Group. J Clin Oncol. 2010;28(15):2529-2537). Gene expression matrix from the arrays was normalized in the same way using RMA model from Bioconductor affy package. Gene expression values were then independently filtered to remove low variance probes using Bioconductor package, genefilter 1.50. Finally, 25,000 probes were then subjected to unsupervised hierarchical clustering analysis using R packages, ape and heatmap 2.0. -------------------------------- Stanford Functional Genomics Facility
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