Project description:C-terminal mutation of Nucleophosmin 1 (NPM1C+) was thought to be a primary driving event that reprograms leukemic-associated transcription program to transform hematopoietic stem and progenitor cells (HS/PCs). However, molecular mechanism underlying NPM1C+-driven leukemogenesis remain elusive. Here, we reported that NPM1C+ reprograms MIZ-1/MYC regulatory axis by altering NPM1-associated CTCF-driven topologically associated domains (TADs) that switched the balance of MIZ1 interaction with co-repressors MYC/G9A and coactivator p300 to control cell cycle progress and myeloid lineage-specific PU.1/CEBPa transcription networks. These alterations impaired hematopoietic cell cycle progression and myeloid differentiation. Knock-in of NPM1C+ in bone marrow HSPCs alters cell cycle regulators and myeloid master transcription factor (TF) TAD topology, chromatin accessibility, and gene regulation leading blockage of myeloid differentiation. Retention of NPM1 or reactivation of PU.1 or CEBPa within nucleus activates differentiation program by reorganizing TADs critical for myeloid TFs and cell cycle regulator, leading to blockage of NPM1C+-driven leukemogenesis. Thus, our data revealed that NPM1C+ reshapes CTCF-defined TAD topology to reprogram signature leukemic transcription program require for cell cycle progression and leukemic progression. Restoration of myeloid transcription program in nucleus reversed NPM1C+-driven transcription signature and promotes myeloid differentiation leading to mitigation of AML.
Project description:Characterization of gene expression changes 72 hours after withdrawal of tamoxifen in murine hematopoietic progenitors transformed by Hoxa9-ER/Meis1 using RNAseq. In the presence of tamoxifen (4OHT), Hoxa9-ER localizes to the nucleus of cells allowing for transformation, while withdrawal of 4OHT (culture in EtOH) leads to loss of nuclear Hoxa9-ER. Loss of Hoxa9-ER leads to a decrease in cellular proliferation and differentiation along the myeloid lineage.
Project description:Characterization of gene expression changes 72 hours after withdrawal of tamoxifen in murine hematopoietic progenitors transformed by Hoxa9-ER/Meis1 using RNAseq. In the presence of tamoxifen (4OHT), Hoxa9-ER localizes to the nucleus of cells allowing for transformation, while withdrawal of 4OHT (culture in EtOH) leads to loss of nuclear Hoxa9-ER. Loss of Hoxa9-ER leads to a decrease in cellular proliferation and differentiation along the myeloid lineage. Examination of gene expression by RNAseq in two conditions in biological replicates.
Project description:To explore the molecular mechanisms induced by the leukemic fusion protein NUP98-HOXA9, we performed gene expression analysis of human hematopoietic progenitors and primary samples of patients that express NUP98-HOXA9. By combining these data with ChIP-seq results, we observed that the fusion protein is able to both activate and repress the expression of its target genes.
Project description:Accumulating evidence indicates that HOXA9 dysregulation is sufficient and necessary for leukemic transformation. Leukemia subtypes showing HOXA9 overexpression include those carrying MLL gene rearrangements (MLL-r), NPM1c mutations, and other genetic alterations. HOXA9 protein is a poor therapeutic target as it lacks targetable pocket domains. Therefore, understanding HOXA9’s functional downstream genes and its regulation might provide alternative therapeutic targets. However, it remains largely unknown how HOXA9, as a homeobox transcriptional factor, binds to noncoding regulatory sequences and controls the downstream genes in MLL-r leukemia and across leukemias of other genetic subtypes. In this study, we have successfully conducted dropout CRISPR screens in the MLL-r SEM cell line stably expressing Cas9 against ~1,800 HOXA9 binding peaks. Integrative data analysis identified six reproducible noncoding hits, including a positive control located in the distal enhancer of FLT3. Cas9-editing and dCas9-KRAB silencing HOXA9’s binding site in distal region of FLT3 reduced transcription and impaired cell proliferation in vitro and in vivo. In addition, RNA-seq and Q-PCR analysis further identified the functional relevant downstream genes upon CRISPR editing of other candidate HOXA9-bound noncoding segments, including survival essential genes as XBP1, JUN and BAHCC1. In summary, the work is significant as it will advance our understanding of how HOXA9-associated transcription programs reconstruct the regulatory network specifying MLL-r dependency. Moreover, our study will promote the future development of HOXA9-mediated noncoding regulation, and alternative therapeutic targets in HOXA9-driven (including HOXA9 and possibly NUP98-HOXA9 subtype) leukemia in patients.
Project description:Pyrydopyrazine A2 induced in vitro the differentiation of leukemic cells (HoxA9-Meis1) into macrophages, we decided to perform a transcriptomic study in order to analyze the GM-CSF pathway regulation. We therefore compared effect with A2 to cells treated with Retinoic acid and D3 Vitamin, a combination known to induce also differentiation of leukemic cells. HoxA9-Meis1 murine AML cells were treated in vitro during 24h, with Pyrydopyrazine( A2) at 3.4μM or a combination of all-trans Retinoic Acid (RA) and 1α-hydroxy-D3 Vitamin (D3V), 10μM each. Gene expression signature was compared to untreated control. One sample was tested for each condition
Project description:Additional Sex Combs Like 1 (ASXL1) is frequently mutated in myeloid malignancies and clonal hematopoiesis of indeterminate potential (CHIP). Although loss of ASXL1 promotes hematopoietic transformation, there is growing evidence that ASXL1 mutations might confer an alteration of function. Here we identify that physiological expression of a C-terminal truncated Asxl1 mutant in vivo using conditional knock-in (KI) results in myeloid skewing, age-dependent anemia, thrombocytosis, and morphologic dysplasia. Although expression of mutant Asxl1 altered the functions of hematopoietic stem cells (HSCs), it maintained their survival in competitive transplantation assays and increased susceptibility to leukemic transformation by co-occurring RUNX1 mutation or viral insertional mutagenesis. KI mice displayed substantial reductions in H3K4me3 and H2AK119Ub without significant reductions in H3K27me3, distinct from the effects of Asxl1 loss. ChIP-seq analysis demonstrated opposing effects of wildtype and mutant Asxl1 on H3K4me3. These findings reveal that ASXL1 mutations confer HSCs with an altered epigenome and increase susceptibility for leukemic transformation, presenting a novel model for CHIP.