title: Transient expression of PU.1 commits multipotent progenitors to a myeloid fate whereas continued expression favors macrophage over granulocyte differentiation.
abstract: OBJECTIVE
  The Ets-family transcription factor PU.1 is expressed specifically in the hematopoietic system, in which it is absolutely required for the generation of B lymphocytes and macrophages. In contrast, overexpression of PU.1 blocks terminal differentiation of the erythroid lineage, in which it can act as an oncogene. In this study we used a multipotential progenitor cell line to examine the effects of PU.1 overexpression on myeloerythroid commitment within a single model system.
  
  
  METHODS
  PU.1 cDNA was introduced transiently and stably into the multipotent, nonleukemic hemopoietic cell line FDCPmix. Transiently transfected cells were isolated by fluorescence-activated cell sorting within 18 hours of transfection. Stable transfectants were selected by antibiotic resistance over a number of weeks. The effects of short- and long-term overexpression of PU.1 on self-renewal, proliferation, and differentiation were investigated.
  
  
  RESULTS
  A transient pulse of expression in multipotent progenitor cells eliminated the options of self-renewal and erythroid differentiation, resulting in commitment to the myeloid lineage. However, this transient pulse of expression did not affect the subsequent lineage choice of bipotent granulocyte/macrophage progenitors. In contrast, continuous expression of PU.1 resulted in a strong bias toward macrophage rather than granulocyte differentiation.
  
  
  CONCLUSIONS
  These results demonstrate promyeloid effects of PU.1 at two distinct stages of hematopoiesis.
authors.affiliation: Laboratory of Molecular Medicine, Interdisciplinary Centre for Clinical Research, University of Leipzig, Leipzig, Germany.
authors.forename: Zoe
authors.initials: Z
authors.lastname: McIvor
authors.forename: Sibyll
authors.initials: S
authors.lastname: Hein
authors.forename: Heike
authors.initials: H
authors.lastname: Fiegler
authors.forename: Timm
authors.initials: T
authors.lastname: Schroeder
authors.forename: Carol
authors.initials: C
authors.lastname: Stocking
authors.forename: Ursula
authors.initials: U
authors.lastname: Just
authors.forename: Michael
authors.initials: M
authors.lastname: Cross
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000502:physiology; D002455:Cell Division / Q000187:drug effects; D019070:Cell Lineage; D002469:Cell Separation; D002478:Cells, Cultured / Q000187:drug effects; D003114:Colony-Forming Units Assay; D015672:Erythroid Precursor Cells / Q000166:cytology; D004921:Erythropoietin / Q000494:pharmacology; D005434:Flow Cytometry; D016179:Granulocyte Colony-Stimulating Factor / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D006098:Granulocytes / Q000166:cytology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000187:drug effects; D007377:Interleukin-3 / Q000494:pharmacology; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology*; D051379:Mice; D039902:Multipotent Stem Cells / Q000166:cytology / Q000187:drug effects; D022423:Myeloid Cells / Q000166:cytology*; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000502:physiology; D015534:Trans-Activators / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D014162:Transfection; D000099232:Proto-Oncogene Protein Spi-1
chemical_list: D004921:Erythropoietin; D016179:Granulocyte Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D007377:Interleukin-3; D016173:Macrophage Colony-Stimulating Factor; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D000099232:Proto-Oncogene Protein Spi-1