A deeper understanding of the molecular mechanisms regulating hematopoietic lineage specification is critical for developing improved therapeutics for disorders that affect red blood cell and platelet abnormalities. Currently, we do not know the mechanisms that influence the fate decisions of the megakaryocyte-eryhtroid progenitors (MEP) that can differentiate down either the red blood cell or megakaryocyte lineage. The overall goal of this proposal is to identify the mechanisms by which the lineage fate is determined in these bipotent progenitors. Progress in determining how bipotent cells become committed has been hampered in part due to lack of ability to identify and enrich for bipotent cells that are at this critical stage. The Krause laboratory has recently addressed this barrier to progress by enhancing, and then using, an in vitro functional assay for individual bipotent MEP to develop improved approaches to enrich for the cells. Our preliminary data using these MEP strongly support the hypothesis that more rapid cell cycling causes an MEP to become biased toward the erythroid over the megakaryocytic lineage. These data include 1) single cell RNA deep sequencing to prove that the enriched cells represent a unique progenitor population that is not fully committed to either of its potential downstream fates and to provide hypothesis-generating data on potential mechanisms of MEP fat determination; 2) determination of small molecules that influence fate decisions; 3) validation of an approach to test knockout of specific genes that affect the fate decision (e.g. MYB); 4) CFSE assessment of changes in proliferation and accompanying cell fate biases; 5) validation of longterm timelapse microscopy from single cells to colony formation to assess cell cycle timing and fate determination; and 6) use of a novel in vivo cell cycle timer reporter. Based on these extensive preliminary data, we propose to: 1) test the hypothesis that cell cycle speed plays a critical role in the MEP fate decision; 2) dissect the molecular mechanisms underlying the MEP fate decision; and 3) test the hypothesis that the elevated platelet counts in humans and mice with iron deficiency anemia are due to a biased MEP fate decision. The results of these studies will contribute to our understanding of fate regulation of normal hematopoietic progenitor cells in mice and healthy human donors, and will provide important insights relevant to the pathogenesis of common treatment-refractory hematopoietic diseases including iron refractory iron deficiency anemia and bone marrow failure. Clinical applications also include enhancement of our ability to produce RBCs and platelets in vitro for transfusion for anemia and thrombocytopenia.

Public Health Relevance

Disorders that affect red blood cell (RBC) and platelet numbers affect millions of patients, and many such disorders are challenging to treat. Transfusion with donated RBCs and/or platelets can be effective in the short-term, but such treatments have long- term risks. An improved understanding of the mechanisms that control the progenitor cells in the bone marrow that ultimately produce RBCs and platelets will allow for the development of improved treatments for patients with disorders that affect RBCs and platelets.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Molecular and Cellular Hematology Study Section (MCH)
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Roy, Cindy
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Yale University
Schools of Medicine
New Haven
United States
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Rahman, Nur-Taz; Schulz, Vincent P; Wang, Lin et al. (2018) MRTFA augments megakaryocyte maturation by enhancing the SRF regulatory axis. Blood Adv 2:2691-2703
Xavier-Ferrucio, Juliana; Krause, Diane S (2018) Concise Review: Bipotent Megakaryocytic-Erythroid Progenitors: Concepts and Controversies. Stem Cells 36:1138-1145
Xavier-Ferrucio, Juliana; Ricon, Lauremília; Vieira, Karla et al. (2018) Hematopoietic defects in response to reduced Arhgap21. Stem Cell Res 26:17-27