Project description:[original title] Gene expression analysis of leukemic samples derived from AF4-MLL- or AF4-MLL/MLL-AF4-transduced and transplanted hematopoietic stem/precursor cells in C57BL6 mice. We used microarrays to analyze the global gene expression in leukemic cells with three distinct immunophenotypes. We compared leukemic cells isolated from the bone marrow of diseased mice and compared these profiles with normal bone marrow.
Project description:In our study, we found that MLL-AF4 transcriptionally induces IGF2BP3 and is required for MLL-Af4 mediated leukemogenesis. Deletion of murine Igf2bp3 significantly increased the survival of mice with MLL-Af4 driven leukemia and greatly attenuated disease. Furthermore, Igf2bp3 was necessary for the development of and the self-renewal capacity of MLL-Af4 leukemic initiating cells. eCLIP and transcriptome analysis of MLL-Af4 transformed stem and progenitor cells and primary cells from MLL-Af4 leukemic mice revealed an IGF2BP3-regulated post-transcriptional operon governing tumor cell survival and proliferation. Critical mRNA targets include the Hoxa locus and numerous genes within the Ras signaling pathway. Together, our findings show that IGF2BP3 is an essential positive regulator of MLL-AF4 mediated leukemogenesis and is a potential therapeutic target in this disease.
Project description:Purpose: We designed this study to evaluate the feasibility of using only one factor to respecify human induced pluripotent stem cells (iPSCs)-derived blood cells into long-term engraftable hematopoietic stem and progenitor cells (HSPCs). We also parallelly compared iPSC-derived HSPCs (iHSPCs) with primary HSPCs under the same induction and transplantation condition in order to examine the functional equivalency between iHSPCs and bona fide HSPCs. Methods: In vitro derived human iPSC-HSPCs are induced with or without (w/o) doxycycline for the expression of MLL-AF4. In vivo derived bone marrow cells are harvested and FACS-sorted for human populations from primary transplants over nine to sixteen weeks after transplantation. Either iPSC-HSPCs or primary HSPCs, both of which are induced by MLL-AF4, is used for the transplantation experiments. iPSCs are either derived from peripheral blood mobilized CD34+ HSPCs (CD34-iPSC) or mononuclear cells (MN-iPSCs). Normal human CD34+ HSPCs and mononuclear cells are set as control groups. Results: MLL-AF4 can impart HSC and lymphoid potential to iPSC-derived blood cells in vitro, and induction of MLL-AF4 leads to the cellular identity transition from common myeloid progenitors to hematopoietic stem and progenitor cells. MLL-AF4 alone is sufficient to realize the potent engraftment of induced HSPCs (iHSPCs) from iPSCs, and multilineage and long-term hematopoiesis could be observed. Primary HSPCs with the induction of MLL-AF4 could gain significantly enhanced engraftability. During the long-term engraftment period, leukemic mutations with a bias to B-cell leukemia could be found in the iHSPCs and their derivatives. By contrast, MLL-AF4 induced primary HSPCs maintain the normal hematopoiesis without leukemic transformation. Conclusions: Our study has demonstrated for the first time, to our knowledge, that the pluripotency-dependent conversion of somatic cells to long-term engraftable HSPCs can be achieved by using a single factor in a non-integrative way. This study also suggests that iPSC-derived HSPCs are more prone to leukemic mutations during the long-term engraftment period, which provides a necessary caveat of using them in the actual therapies.
Project description:We created a mouse model where conditional expression of physiologic levels of an Mll-AF4 fusion oncogene induces development of acute lymphoblastic (ALL) or acute myeloid leukemias (AML). Immunophenotypic and gene expression analysis of the ALL cells demonstrated bone marrow replacement with B-precursor cells which express a gene expression profile that has significant overlap with profiles in human MLL-rearranged ALL. To examine early, pre-leukemic changes in lymphoid cells due to Mll-AF4 expression, we infected 5-FU bone marrow cells from Mll-AF4stop knocking mice with activating (Cre-GFP) or control (MIF-GFP) retrovirus ex vivo and measured expression changes after culture under lymphoid growth conditions. Experiment Overall Design: Mll-AF4stop knock-in mice were treated with 5-FU and 5 days later their bone marrow infected ex vivo with either Cre-GFP to activate the Mll-AF4 fusion construct or with a control MIG-Cre retrovirus. GFP+ cells were sorted 2 days post-infection and cultured for 14 days under lymphoid growth conditions before total RNA was isolated for hybridization to Affymetrix expression microarrays.
Project description:[original title] Gene expression analysis of leukemic samples derived from AF4-MLL- or AF4-MLL/MLL-AF4-transduced and transplanted hematopoietic stem/precursor cells in C57BL6 mice. We used microarrays to analyze the global gene expression in leukemic cells with three distinct immunophenotypes.
Project description:The t(4;11)(q21;q23) fuses MLL to AF4, the most common MLL fusion partner. Here we show that MLL fused to murine Af4, highly conserved with human AF4, produces high-titer retrovirus permitting efficient transduction of human CD34+ cells to generate a faithful model of t(4;11) proB ALL that fully recapitulates the immunophenotypic and molecular aspects of the disease. MLL-Af4 induces a distinct B-ALL from MLL-AF9 through differential DNA binding of the fusion proteins leading to specific gene expression patterns. MLL-Af4 cells can assume a myeloid state under environmental pressure but retain lymphoid-lineage potential. We observed this incongruity in t(4;11) patients who evaded CD19-directed therapy by undergoing myeloid-lineage switch. Our model provides a valuable tool to unravel the pathogenesis of MLL-AF4 leukemogenesis.
Project description:We created a mouse model where conditional expression of physiologic levels of an Mll-AF4 fusion oncogene induces development of acute lymphoblastic (ALL) or acute myeloid leukemias (AML). Immunophenotypic and gene expression analysis of the ALL cells demonstrated bone marrow replacement with B-precursor cells which express a gene expression profile that has significant overlap with profiles in human MLL-rearranged ALL. To examine early, pre-leukemic changes in lymphoid cells due to Mll-AF4 expression, we infected 5-FU bone marrow cells from Mll-AF4stop knocking mice with activating (Cre-GFP) or control (MIF-GFP) retrovirus ex vivo and measured expression changes after culture under lymphoid growth conditions. Keywords: Cell type comparison
Project description:Chromatin accessibility was assessed by ATAC-Seq in lymphoid-primed multipotent progenitors (LMPPs) from human foetal livers (FLs) and mouse wild-type FLs as well as FLs from mouse embryos that express the oncofusion Mll-AF4 in the definitive blood system. The aim of this study was to establish whether overall chromatin accessibility at key haematopoietic sites and loci that have been linked to leukaemia are differentially accessible in human vs mouse LMPPs and whether this is altered by the expression of the Mll-AF4 oncofusion.