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Browsing CNIO by Publisher "American Society of Hematology (ASH)"
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Publication Activation of the endomitotic spindle assembly checkpoint and thrombocytopenia in Plk1-deficient mice.(American Society of Hematology (ASH), 2015-10-01) Trakala, Marianna; Partida, David; Salazar-Roa, Maria; Maroto, María; Wachowicz, Paulina; de Carcer Diez, Guillermo; Malumbres Martinez, Marcos; Fundación La Caixa; Ministerio de Economía y Competitividad (España); Comunidad de Madrid (España); Worldwide Cancer Research; Unión Europea; Consolider-Ingenio ProgrammePolyploidization in megakaryocytes is achieved by endomitosis, a specialized cell cycle in which DNA replication is followed by aberrant mitosis. Typical mitotic regulators such as Aurora kinases or Cdk1 are dispensable for megakaryocyte maturation, and inhibition of mitotic kinases may in fact promote megakaryocyte maturation. However, we show here that Polo-like kinase 1 (Plk1) is required for endomitosis, and ablation of the Plk1 gene in megakaryocytes results in defective polyploidization accompanied by mitotic arrest and cell death. Lack of Plk1 results in defective centrosome maturation and aberrant spindle pole formation, thus impairing the formation of multiple poles typically found in megakaryocytes. In these conditions, megakaryocytes arrest for a long time in mitosis and frequently die. Mitotic arrest in wild-type megakaryocytes treated with Plk1 inhibitors or Plk1-null cells is triggered by the spindle assembly checkpoint (SAC), and can be rescued in the presence of SAC inhibitors. These data suggest that, despite the dispensability of proper chromosome segregation in megakaryocytes, an endomitotic SAC is activated in these cells upon Plk1 inhibition. SAC activation results in defective maturation of megakaryocytes and cell death, thus raising a note of caution in the use of Plk1 inhibitors in therapeutic strategies based on polyploidization regulators.Publication Telomere shortening in enterocytes of patients with uncontrolled acute intestinal graft-versus-host disease.(American Society of Hematology (ASH), 2015-11-26) Hummel, Sebastian; Ventura Ferreira, Mónica S; Heudobler, Daniel; Huber, Elisabeth; Fahrenkamp, Dirk; Gremse, Felix; Schmid, Karin; Müller-Newen, Gerhard; Ziegler, Patrick; Jost, Edgar; Blasco, MA; Brümmendorf, Tim H; Holler, Ernst; Beier, Fabian; University Hospital AachenAcute intestinal graft-versus-host disease (aGVHD) refractory to immunosuppressive treatment is a serious complication after allogenic hematopoietic stem cell transplantation (HSCT). The underlying mechanisms of refractory aGVHD of the gut are not fully understood. Although telomere length (TL) reflects the replicative history of a cell, critically short telomeres have been associated with replicative exhaustion and tissue failure. In this study, we demonstrate that enterocytes of patients with refractory intestinal aGVHD show significantly increased proliferation, which translates into significant and critical telomere attrition following HSCT as compared with unaffected patients undergoing HSCT. Calculated telomere loss in aGVHD patients is 190 bp/wk, thereby massively exceeding physiological steady-state TL shortening rates such as in lymphocytes (∼50 bp/y). Our data support the hypothesis that increased compensatory proliferation following continued tissue damage can result in massive telomere loss in enterocytes of aGVHD patients. The present study introduces aGVHD-triggered increased cellular turnover and telomere loss with subsequent replicative exhaustion as a mechanism for refractory gut GVHD that is compatible with the long-term clinical aspect of the disease and provides a basis for stem cell protective therapies in the treatment of aGVHD.Publication Whole-genome CRISPR screening identifies N-glycosylation as a genetic and therapeutic vulnerability in CALR-mutant MPNs.(American Society of Hematology (ASH), 2022-09-15) Jutzi, Jonas S; Marneth, Anna E; Ciboddo, Michele; Guerra-Moreno, Angel; Jiménez-Santos, María José; Kosmidou, Anastasia; Dressman, James W; Liang, Hongyan; Hamel, Rebecca; Lozano, Patricia; Rumi, Elisa; Doench, John G; Gotlib, Jason; Krishnan, Anandi; Elf, Shannon; Al-Shahrour, Fatima; Mullally, Ann; NIH - National Cancer Institute (NCI) (Estados Unidos); German Research Foundation (DFG); Leukemia and Lymphoma Society; Novartis; Fondazione AIRC per la ricerca sul cancroCalreticulin (CALR) mutations are frequent, disease-initiating events in myeloproliferative neoplasms (MPNs). Although the biological mechanism by which CALR mutations cause MPNs has been elucidated, there currently are no clonally selective therapies for CALR-mutant MPNs. To identify unique genetic dependencies in CALR-mutant MPNs, we performed a whole-genome clustered regularly interspaced short palindromic repeats (CRISPR) knockout depletion screen in mutant CALR-transformed hematopoietic cells. We found that genes in the N-glycosylation pathway (among others) were differentially depleted in mutant CALR-transformed cells as compared with control cells. Using a focused pharmacological in vitro screen targeting unique vulnerabilities uncovered in the CRISPR screen, we found that chemical inhibition of N-glycosylation impaired the growth of mutant CALR-transformed cells, through a reduction in MPL cell surface expression. We treated Calr-mutant knockin mice with the N-glycosylation inhibitor 2-deoxy-glucose (2-DG) and found a preferential sensitivity of Calr-mutant cells to 2-DG as compared with wild-type cells and normalization of key MPNs disease features. To validate our findings in primary human cells, we performed megakaryocyte colony-forming unit (CFU-MK) assays. We found that N-glycosylation inhibition significantly reduced CFU-MK formation in patient-derived CALR-mutant bone marrow as compared with bone marrow derived from healthy donors. In aggregate, our findings advance the development of clonally selective treatments for CALR-mutant MPNs.