Project description:Acute megakaryoblastic leukemia (AMKL) is more frequently seen in Down syndrome patients, where it is often preceded by a transient myeloproliferative disorder (DS-TMD). The development of DS-TMD and DS-AMKL require not only the presence of the trisomy 21 but also that of GATA1 mutations. However, despite extensive studies into the genetics of DS-AMKL, not much is known about the epigenetic deregulation associated with this disease. In order to understand how epigenetic changes at the DNA methylation level contribute to DS leukemogenesis we performed DNA methylation profiling at different stages of development of this disease and analyzed the dynamics of epigenetic reprogramming. Early genome-wide epigenetic changes can be detected in trisomy 21 fetal liver mononuclear cells, even prior to the development of hematological abnormalities. These early changes are characterized by marked loss of DNA methylation at genes associated with regulation of key developmental processes. This first wave of aberrant DNA hypomethylation is followed by a second wave of epigenetic reprogramming detected in blast cells from DS-TMD and DS-AMKL, characterized by gains of methylation. This second wave of hypermethylation targets a distinct set of genes, preferentially affecting genes involved in hematopoiesis and regulation of cell growth and proliferation. DNA methylation profiles obtained at different stages of the development of Down syndrome AMKL and from CD41+ cells from partial trisomic mice
Project description:Acute megakaryoblastic leukemia (AMKL) is more frequently seen in Down syndrome patients, where it is often preceded by a transient myeloproliferative disorder (DS-TMD). The development of DS-TMD and DS-AMKL require not only the presence of the trisomy 21 but also that of GATA1 mutations. However, despite extensive studies into the genetics of DS-AMKL, not much is known about the epigenetic deregulation associated with this disease. In order to understand how epigenetic changes at the DNA methylation level contribute to DS leukemogenesis we performed DNA methylation profiling at different stages of development of this disease and analyzed the dynamics of epigenetic reprogramming. Early genome-wide epigenetic changes can be detected in trisomy 21 fetal liver mononuclear cells, even prior to the development of hematological abnormalities. These early changes are characterized by marked loss of DNA methylation at genes associated with regulation of key developmental processes. This first wave of aberrant DNA hypomethylation is followed by a second wave of epigenetic reprogramming detected in blast cells from DS-TMD and DS-AMKL, characterized by gains of methylation. This second wave of hypermethylation targets a distinct set of genes, preferentially affecting genes involved in hematopoiesis and regulation of cell growth and proliferation.
Project description:Children with Down syndrome have a 150-fold increased risk of developing myeloid leukemia. As Down syndrome leukemogenesis initiates during fetal development, we sought to characterize the cellular mechanisms of preleukemic initiation and leukemic progression using CRISPR/Cas9-mediated gene editing in human disomic and trisomic fetal liver hematopoietic cells and xenotransplantation. Compared to disomic fetal liver, trisomy 21 initiated atypical fetal hematopoiesis, in part through up-regulation of chromosome 21 miRNAs. GATA1 mutations caused transient preleukemia only when introduced into trisomy 21 long-term hematopoietic stem cells. By contrast, progression to leukemia was independent of trisomy 21 and originated in a wide spectrum of stem and progenitor cells through additional mutations in cohesin genes such as STAG2. CD117+ cells mediated the propagation and progression of the preleukemic and leukemic disease. Treatment with small molecule CD117/KIT inhibitors efficiently targeted preleukemic stem cells and blocked progression to leukemia; thereby laying the groundwork for early prevention strategies in Down syndrome newborns.
Project description:Children with Down syndrome have a 150-fold increased risk of developing myeloid leukemia. As Down syndrome leukemogenesis initiates during fetal development, we sought to characterize the cellular mechanisms of preleukemic initiation and leukemic progression using CRISPR/Cas9-mediated gene editing in human disomic and trisomic fetal liver hematopoietic cells and xenotransplantation. Compared to disomic fetal liver, trisomy 21 initiated atypical fetal hematopoiesis, in part through up-regulation of chromosome 21 miRNAs. GATA1 mutations caused transient preleukemia only when introduced into trisomy 21 long-term hematopoietic stem cells. By contrast, progression to leukemia was independent of trisomy 21 and originated in a wide spectrum of stem and progenitor cells through additional mutations in cohesin genes such as STAG2. CD117+ cells mediated the propagation and progression of the preleukemic and leukemic disease. Treatment with small molecule CD117/KIT inhibitors efficiently targeted preleukemic stem cells and blocked progression to leukemia; thereby laying the groundwork for early prevention strategies in Down syndrome newborns.
Project description:Aneuploidy and structural aberrations affecting chromosome 21 (Hsa21) are the most frequent in cytogentic events in acute myeloid leukemia. However, it remains unclear why leukemic blasts select for amplifications of Hsa21 or parts of it and why children with Down syndrome (i.e. trisomy 21) are at a high risk of developing leukemia. Here, we propose that disequilibrium of the RUNX1 isoforms and resultant RUNX1A dominance are key to trisomy 21-associated leukemogenesis. Using a Hsa21-focussed CRISPR-Cas9 screen, we uncovered a strong and specific RUNX1 dependency in myeloid leukemia associated with Down syndrome (ML-DS). High levels of RUNX1A – as seen in ML-DS – synergized with the pathognomonic Gata1s mutation in ML-DS pathogenesis, an effect that was reversed upon restoration of the normal RUNX1A:RUNX1C equilibrium. Mechanistically, RUNX1A displaces RUNX1C from its endogenous binding sites and recruits the MYC cofactor MAX to induce oncogenic programs and perturb normal differentiation. This presents a therapeutic vulnerability that can be exploited by interfering with MYC:MAX dimerization. Our study highlights the importance of alternative splicing in leukemogenesis, and paves the way for developing specific and targeted therapies for ML-DS as well as for other leukemias with Hsa21 aneuploidy or RUNX1 isoform disequilibrium.