Project description:The purpose of this study is to investigate the transcriptional programs as it relates to disease latency initiated by different MLL fusion proteins, including: MLL-AF1p, MLL-AF6, MLL-Gas7, MLL-AF9 and MLL-ENL. Leukemia cell lines were established by transforming kit+ mouse bone marrow cells with retroviruses coding MLL-AF1p, MLL-AF6, MLL-Gas7, MLL-AF9 or MLL-ENL. At early phase after the cell lines were established, cells growing at exponential phase (cell density at 0.5~1x106/ml) were harvested for RNA extraction and sequencing purpose. Sequencing is performed on total RNA isolated from mouse leukemia cell lines generated from kit+ mouse bone marrow cells transduced with various MLL fusion proteins and is compared to control total RNA isolated from kit+ mouse bone marrow cells.
Project description:To identify the target genes of Runx1 in MLL fusion leukemia, we performed microarray analysis using control and Runx1-deficient MLL-ENL leukemia cells. Runx1 intact and excised bone marrow cells were transduced with MLL-ENL and transplanted into congenic mice. Leukemic cells were harvested from moribund mice, and gene expression was compared using 3 independent leukemia cells for each genotype.
Project description:The purpose of this study is to investigate the transcriptional programs as it relates to disease latency initiated by different MLL fusion proteins, including: MLL-AF1p, MLL-AF6, MLL-Gas7, MLL-AF9 and MLL-ENL. Leukemia cell lines were established by transforming kit+ mouse bone marrow cells with retroviruses coding MLL-AF1p, MLL-AF6, MLL-Gas7, MLL-AF9 or MLL-ENL. At early phase after the cell lines were established, cells growing at exponential phase (cell density at 0.5~1x106/ml) were harvested for RNA extraction and sequencing purpose.
Project description:MLL-fusions may induce leukemogenic gene expression programs by recruiting the histone H3K79 methyltransferase to MLL-target promoters. We evaluated gene expression changes after cre-mediated loss of Dot1l in leukemia cells obtained from mice injected with MLL-9 transformed lineage negative bone marrow cells. MLL-AF9 murine leukemia cells carrying two conditional Dot1l alleles were retrovirally transduced with Cre or empty control vector, and gene expression changes were monitored on day 3, 5, and 7 after transduction.
Project description:Activation of the MLL-ENL-ERtm oncogene initiates aberrant proliferation of myeloid progenitors. Here, we show induction of a fail-safe mechanism mediated by the DNA damage response (DDR) machinery that results in activation of the ATR/ATM-Chk1/Chk2-p53/p21 checkpoint and cellular senescence at early stages of cellular transformation caused by a regulatable MLL-ENL-ERtm in mice. Furthermore, we identified the transcription program underlying this intrinsic anti-cancer barrier, and DDR-induced inflammatory regulators that fine-tune the signaling towards senescence, thereby modulating the fate of MLL-ENL-immortalized cells in a tissue-environment-dependent manner. Our results indicate that DDR is a rate-limiting event for acquisition of stem cell-like properties in MLL-ENL-ERtm-mediated transformation, as experimental inhibition of the barrier accelerated the transition to immature cell states and acute leukemia development. We created a mouse model wherein the protein function of the MLL-ENL oncogene depends on tamoxifen due to fusion with the mutated estrogen-binding domain of the estrogen receptor (ERtm). After 7 months of tamoxifen administration, the MLL-ENL-ERtm mice developed a myeloproliferative disease, which progressed into the terminal stage after a long period (mean survival: 592 ± 112 days) of continuous tamoxifen provision. We have profiled gene expression at three time-points of tamoxifen treatment corresponding to three distinct cellular states of the MLL-ENL-ERtm-induced myeloproliferation in the bone marrow: 1. 7 months - high proliferation state with low DDR signaling (4 biological replicates), 2. 7-8 months - the transition period of lower proliferation and high DDR activity (4 biogical replicates) and 3. 8 months - the senescence (3 biological replicates). Time-matched tamoxifen-treated wild-type bone marrow analysed in 4 biological replicates. We have profiled gene expression in three disease stages in the spleen: 1. 7 months - early stage - induced proliferation and DDR (3 biological replicates), 2. 9-10 months - progression - partial senescence and DDR is maintained (3 biological replicates) and 3. 16-23 months - terminal stage - proliferation, low or absent DDR and no senescence (3 biological replicates). Time-matched tamoxifen-treated and age-matched wild-type spleens analysed in 5 biological replicates.
Project description:Acute myelogenous leukemia (AML) is driven by leukemic stem cells (LSC) generated by mutations that confer (or maintain) self-renewal potential coupled to an aberrant differentiation program. Using retroviral mutagenesis, we identified genes that generate LSC in collaboration with genetic disruption of the gene encoding interferon response factor 8 (Irf8), which induces a myeloproliferation in vivo. Amongst the targeted genes, we identified Mef2c, encoding a MADS transcription factor, and confirmed that over-expression induced a myelomonocytic leukemia in cooperation with Irf8 deficiency. Strikingly, several of the genes identified in our screen have been reported to be upregulated in the mixed-lineage leukemia (MLL) subtype. High MEF2C expression levels were confirmed in AML patient samples with MLL gene disruptions, prompting an investigation of the causal interplay. Using a conditional mouse strain, we demonstrated that Mef2c deficiency does not impair the establishment nor maintenance of LSC generated in vitro by MLL/ENL fusion proteins â?? however, its loss led to compromised homing and invasiveness of the tumor cells. Mef2c-dependent targets included several genes encoding matrix metalloproteinases and chemokine ligands and receptors, providing a mechanistic link to increased homing and motility. Thus an early event in LSC generation may be responsible for the aggressive nature of this leukemia subtype. Experiment Overall Design: For gene expression profiling of M/E cells, RNA was isolated from M/E-Mef2c del/- cells infected with MYs-iPAC (empty vector) or MYs-pMef2cASR after puromycin selection at three different time points, pooled, and hybridized against the Agilent Whole Mouse Genome Microarray 4x44K using the one-color service of Miltenyi. Transcript levels were verified by real-time RT-PCR using the SYBRGreen Reaction Mix (Roche Mannheim) in a Roche Light-Cycler. cDNA levels were normalized against Hprt transcript levels. Primers and amplification conditions are available upon request.
Project description:Acute myelogenous leukemia (AML) is driven by leukemic stem cells (LSC) generated by mutations that confer (or maintain) self-renewal potential coupled to an aberrant differentiation program. Using retroviral mutagenesis, we identified genes that generate LSC in collaboration with genetic disruption of the gene encoding interferon response factor 8 (Irf8), which induces a myeloproliferation in vivo. Amongst the targeted genes, we identified Mef2c, encoding a MADS transcription factor, and confirmed that over-expression induced a myelomonocytic leukemia in cooperation with Irf8 deficiency. Strikingly, several of the genes identified in our screen have been reported to be upregulated in the mixed-lineage leukemia (MLL) subtype. High MEF2C expression levels were confirmed in AML patient samples with MLL gene disruptions, prompting an investigation of the causal interplay. Using a conditional mouse strain, we demonstrated that Mef2c deficiency does not impair the establishment nor maintenance of LSC generated in vitro by MLL/ENL fusion proteins – however, its loss led to compromised homing and invasiveness of the tumor cells. Mef2c-dependent targets included several genes encoding matrix metalloproteinases and chemokine ligands and receptors, providing a mechanistic link to increased homing and motility. Thus an early event in LSC generation may be responsible for the aggressive nature of this leukemia subtype.
Project description:We have developed a new conditional transgenic mouse showing that MLL-ENL, at an endogenous-like expression level, induces leukemic transformation selectively in LT-HSCs. To investigate the molecular mechanism of leukemic transformation in LT-HSCs conditionally expressing MLL-ENL, we preliminarily performed comprehensive gene expression profiling of CreER-transduced LT-HSCs and ST-HSCs using cDNA microarray analysis.
Project description:Chromosomal translocations encoding the MLL-AF9 and MLL-ENL fusion transcription factors are prevalent in infant acute leukaemia and therapy-related leukaemia. In order to conditionally express the MLL-fusion oncogene in primary haematopoietic progenitor cells (HPC), retroviral delivery of the Tet-off expression system was used (Horton et al., Cancer Res, 2005). Treatment of the conditional cells with Doxycycline caused a decrease in MLL-AF9/ENL mRNA and protein expression, and resulted in terminal differentiation of the cells. By analysing global changes in gene expression after treatment of cells with Doxycycline we were able to identify a number of potential transcriptional target genes of the MLL-AF9 and MLL-ENL fusion oncogenes.
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.