title: Visualizing PU.1 activity during hematopoiesis.
abstract: OBJECTIVE
  PU.1 is a critical transcription factor for hematopoietic development that is required for the early differentiation of myeloid, erythroid, and B lineage cells. To gain a better insight into PU.1 function, we performed a comprehensive analysis of PU.1 gene activity in the hematopoietic system, using a green fluorescent protein reporter mouse line.
  
  
  METHODS
  We used flow cytometry to analyze green fluorescent protein (GFP) expression, along with various cell surface markers, in heterozygote mice that harbor a GFP reporter knocked into exon1 of the PU.1 gene. Phenotypic and functional properties of GFP+ and GFP- precursors were studied.
  
  
  RESULTS
  We show that PU.1 is dynamically and heterogeneously expressed in many hematopoietic lineages, from the stem cell stage to terminally differentiated cells, suggesting that PU.1 is not only important in early differentiation events but also may play a role in mature hematopoietic cell function. Further, examination of GFP+ vs GFP- populations shows that differentiation, but not commitment, to the myeloid lineage requires PU.1. In contrast, B cell commitment is associated with low levels of PU.1 expression.
  
  
  CONCLUSIONS
  Our study provides a detailed visualization of PU.1 gene activity in hematopoietic cells, and shows that highly dynamic regulation of PU.1 accompanies cell fate decisions during hematopoiesis.
authors.affiliation: Institut de Génétique et de Biologie Moléculaire et Cellulaire, IGBMC CNRS/INSERM/ULP, Illkirch, CU Strasbourg, France.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Back
authors.forename: David
authors.initials: D
authors.lastname: Allman
authors.forename: Susan
authors.initials: S
authors.lastname: Chan
authors.forename: Philippe
authors.initials: P
authors.lastname: Kastner
mesh_terms: D000818:Animals; D000954:Antigens, Surface / Q000032:analysis; D001402:B-Lymphocytes; D002454:Cell Differentiation; D019070:Cell Lineage; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000502:physiology*; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D006410:Hematopoiesis; D051379:Mice; D022423:Myeloid Cells; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics / Q000502:physiology*; D000099232:Proto-Oncogene Protein Spi-1
chemical_list: D000954:Antigens, Surface; D049452:Green Fluorescent Proteins; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D000099232:Proto-Oncogene Protein Spi-1