Progressive chromatin rewiring by ETO2::GLIS2 revealed in a human iPSC model of pediatric leukemia initiation.

Pediatric acute myeloid leukemia frequently harbor fusion oncogenes associated with poor prognosis, including KMT2A, NUP98 and GLIS2 rearrangements. While murine models have demonstrated their leukemogenic activities, the steps from a normal human cell to leukemic blasts remain unclear. Here, we precisely reproduced the inversion of chromosome 16 resulting in ETO2::GLIS2 fusion in human induced pluripotent stem cells (iPSC).

The ETO2 transcriptional cofactor maintains acute leukemia by driving a MYB/EP300-dependent stemness program.

Transcriptional cofactors of the ETO family are recurrent fusion partners in acute leukemia. We characterized the ETO2 regulome by integrating transcriptomic and chromatin binding analyses in human erythroleukemia xenografts and controlled ETO2 depletion models. We demonstrate that beyond its well-established repressive activity, ETO2 directly activates transcription of MYB, among other genes.

In vivo screening characterizes chromatin factor functions during normal and malignant hematopoiesis.

Cellular differentiation requires extensive alterations in chromatin structure and function, which is elicited by the coordinated action of chromatin and transcription factors. By contrast with transcription factors, the roles of chromatin factors in differentiation have not been systematically characterized. Here, we combine bulk ex vivo and single-cell in vivo CRISPR screens to characterize the role of chromatin factor families in hematopoiesis.

High caspase 3 and vulnerability to dual BCL2 family inhibition define ETO2::GLIS2 pediatric leukemia.

Pediatric acute myeloid leukemia expressing the ETO2::GLIS2 fusion oncogene is associated with dismal prognosis. Previous studies have shown that ETO2::GLIS2 can efficiently induce leukemia development associated with strong transcriptional changes but those amenable to pharmacological targeting remained to be identified. By studying an inducible ETO2::GLIS2 cellular model, we uncovered that de novo ETO2::GLIS2 expression in human cells led to increased CASP3 transcription, CASP3 activation, and cell death.

HOXA9 forms a repressive complex with nuclear matrix-associated protein SAFB to maintain acute myeloid leukemia.

HOXA9 is commonly upregulated in acute myeloid leukemia (AML), in which it confers a poor prognosis. Characterizing the protein interactome of endogenous HOXA9 in human AML, we identified a chromatin complex of HOXA9 with the nuclear matrix attachment protein SAFB. SAFB perturbation phenocopied HOXA9 knockout to decrease AML proliferation, increase differentiation and apoptosis in vitro, and prolong survival in vivo.

Screening of ETO2-GLIS2-induced Super Enhancers identifies targetable cooperative dependencies in acute megakaryoblastic leukemia.

Super Enhancers (SEs) are clusters of regulatory elements associated with cell identity and disease. However, whether these elements are induced by oncogenes and can regulate gene modules cooperating for cancer cell transformation or maintenance remains elusive. To address this question, we conducted a genome-wide CRISPRi-based screening of SEs in ETO2-GLIS2 acute megakaryoblastic leukemia.

Human erythroleukemia genetics and transcriptomes identify master transcription factors as functional disease drivers.

Acute erythroleukemia (AEL or acute myeloid leukemia [AML]-M6) is a rare but aggressive hematologic malignancy. Previous studies showed that AEL leukemic cells often carry complex karyotypes and mutations in known AML-associated oncogenes. To better define the underlying molecular mechanisms driving the erythroid phenotype, we studied a series of 33 AEL samples representing 3 genetic AEL subgroups including TP53-mutated, epigenetic regulator-mutated (eg, DNMT3A, TET2, or IDH2), and undefined cases with low mutational burden.

Ontogenic Changes in Hematopoietic Hierarchy Determine Pediatric Specificity and Disease Phenotype in Fusion Oncogene-Driven Myeloid Leukemia.

Fusion oncogenes are prevalent in several pediatric cancers, yet little is known about the specific associations between age and phenotype. We observed that fusion oncogenes, such as , are associated with acute megakaryoblastic or other myeloid leukemia subtypes in an age-dependent manner. Analysis of a novel inducible transgenic mouse model showed that expression in fetal hematopoietic stem cells induced rapid megakaryoblastic leukemia whereas expression in adult bone marrow hematopoietic stem cells resulted in a shift toward myeloid transformation with a strikingly delayed leukemogenic potential.

[Pediatric de novo acute megakaryoblastic leukemia: an affair of complexes].

Pediatric acute megakaryoblastic leukemia (AMKL) are generally associated with poor prognosis and the expression of fusion oncogenes involving transcriptional regulators. Recent results indicate that the ETO2-GLIS2 fusion, associated with 25-30 % of pediatric AMKL, binds and alters the activity of regulatory regions of gene expression, called "enhancers", resulting in the deregulation of GATA and ETS factors essential for the development of hematopoietic stem cells. An imbalance in GATA/ETS factor activity is also found in other AMKL subgroups.

Partial trisomy 21 contributes to T-cell malignancies induced by JAK3-activating mutations in murine models.

JAK3-activating mutations are commonly seen in chronic or acute hematologic malignancies affecting the myeloid, megakaryocytic, lymphoid, and natural killer (NK) cell compartment. Overexpression models of mutant JAK3 or pharmacologic inhibition of its kinase activity have highlighted the role that these constitutively activated mutants play in the T-cell, NK cell, and megakaryocytic lineages, but to date, the functional impact of JAK3 mutations at an endogenous level remains unknown. Here, we report a JAK3 knockin mouse model and demonstrate that activated JAK3 leads to a progressive and dose-dependent expansion of CD8 T cells in the periphery before colonization of the bone marrow.

B-cell tumor development in -deficient mice.

The gene encodes an α-ketoglutarate-dependent dioxygenase able to oxidize 5-methylcytosine into 5-hydroxymethylcytosine, which is a step toward active DNA demethylation. is frequently mutated in myeloid malignancies but also in B- and T-cell malignancies. somatic mutations are also identified in healthy elderly individuals with clonal hematopoiesis.

AIF loss deregulates hematopoiesis and reveals different adaptive metabolic responses in bone marrow cells and thymocytes.

Mitochondrial metabolism is a tightly regulated process that plays a central role throughout the lifespan of hematopoietic cells. Herein, we analyze the consequences of the mitochondrial oxidative phosphorylation (OXPHOS)/metabolism disorder associated with the cell-specific hematopoietic ablation of apoptosis-inducing factor (AIF). AIF-null (AIF ) mice developed pancytopenia that was associated with hypocellular bone marrow (BM) and thymus atrophy.

Molecular pathways driven by ETO2-GLIS2 in aggressive pediatric leukemia.

The ETO2-GLIS2 fusion oncoprotein is associated with poor prognosis pediatric acute megakaryoblastic leukemia. Recently, we observed that ETO2-GLIS2 controls enhancers activity at genes regulating haematopoietic progenitor self-renewal and differentiation toward the megakaryocytic lineage. We also showed that targeting ETO2-GLIS2 complex stability inhibits these properties and may represent a novel therapeutic strategy.

Pediatric Acute Megakaryoblastic Leukemia: Multitasking Fusion Proteins and Oncogenic Cooperations.

Pediatric leukemia presents specific clinical and genetic features from adult leukemia but the underpinning mechanisms of transformation are still unclear. Acute megakaryoblastic leukemia (AMKL) is the malignant accumulation of progenitors of the megakaryocyte lineage that normally produce blood platelets. AMKL is diagnosed de novo, in patients showing a poor prognosis, or in Down syndrome (DS) patients with a better prognosis.

ETO2-GLIS2 Hijacks Transcriptional Complexes to Drive Cellular Identity and Self-Renewal in Pediatric Acute Megakaryoblastic Leukemia.

Chimeric transcription factors are a hallmark of human leukemia, but the molecular mechanisms by which they block differentiation and promote aberrant self-renewal remain unclear. Here, we demonstrate that the ETO2-GLIS2 fusion oncoprotein, which is found in aggressive acute megakaryoblastic leukemia, confers megakaryocytic identity via the GLIS2 moiety while both ETO2 and GLIS2 domains are required to drive increased self-renewal properties. ETO2-GLIS2 directly binds DNA to control transcription of associated genes by upregulation of expression and interaction with the ETS-related ERG protein at enhancer elements.

Identification of regulators of polyploidization presents therapeutic targets for treatment of AMKL.

The mechanism by which cells decide to skip mitosis to become polyploid is largely undefined. Here we used a high-content image-based screen to identify small-molecule probes that induce polyploidization of megakaryocytic leukemia cells and serve as perturbagens to help understand this process. Our study implicates five networks of kinases that regulate the switch to polyploidy.

TET2 inactivation results in pleiotropic hematopoietic abnormalities in mouse and is a recurrent event during human lymphomagenesis.

Loss-of-function mutations affecting one or both copies of the Ten-Eleven-translocation (TET)2 gene have been described in various human myeloid malignancies. We report that inactivation of Tet2 in mouse perturbs both early and late steps of hematopoiesis including myeloid and lymphoid differentiation in a cell-autonomous manner, endows the cells with competitive advantage, and eventually leads to the development of malignancies. We subsequently observed TET2 mutations in human lymphoid disorders.

Crosstalk between NOTCH and AKT signaling during murine megakaryocyte lineage specification.

The NOTCH signaling pathway is implicated in a broad range of developmental processes, including cell fate decisions. However, the molecular basis for its role at the different steps of stem cell lineage commitment is unclear. We recently identified the NOTCH signaling pathway as a positive regulator of megakaryocyte lineage specification during hematopoiesis, but the developmental pathways that allow hematopoietic stem cell differentiation into the erythro-megakaryocytic lineages remain controversial.