title: Sublethal radiation injury uncovers a functional transition during erythroid maturation.
abstract: OBJECTIVE
  Clastogenic injury of the erythroid lineage results in anemia, reticulocytopenia, and transient appearance of micronucleated reticulocytes. However, the micronucleated reticulocyte dose-response in murine models is only linear to 2 Gy total body irradiation and paradoxically decreases at higher exposures, suggesting complex radiation effects on erythroid intermediates. To better understand this phenomenon, we investigated the kinetics and apoptotic response of the erythron to sublethal radiation injury.
  
  
  METHODS
  We analyzed the response to 1 and 4 Gy total body irradiation of erythroid progenitors and precursors using colony assays and imaging flow cytometry, respectively. We also investigated cell cycling and apoptotic gene expression of the steady-state erythron.
  
  
  RESULTS
  After 1 Gy total body irradiation, erythroid progenitors and precursors were partially depleted. In contrast, essentially all bone marrow erythroid progenitors and precursors were lost within 2 days after 4 Gy irradiation. Imaging flow cytometry analysis revealed preferential loss of phenotypic erythroid colony-forming units and proerythroblasts immediately after sublethal irradiation. Furthermore, these populations underwent radiation-induced apoptosis, without changes in steady-state cellular proliferation, at much higher frequencies than later-stage erythroid precursors. Primary erythroid precursor maturation is associated with marked Bcl-xL upregulation and Bax and Bid downregulation.
  
  
  CONCLUSIONS
  Micronucleated reticulocyte loss after higher sublethal radiation exposures results from rapid depletion of erythroid progenitors and precursors. This injury reveals that erythroid colony-forming units and proerythroblasts constitute a particularly proapoptotic compartment within the erythron. We conclude that the functional transition of primary proerythroblasts to later-stage erythroid precursors is characterized by a shift from a proapoptotic to an antiapoptotic phenotype.
authors.affiliation: Center for Pediatric Biomedical Research, Department of Pediatrics, University of Rochester Medical Center, Rochester, NY 14642, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Peslak
authors.forename: Jesse
authors.initials: J
authors.lastname: Wenger
authors.forename: Jeffrey C
authors.initials: JC
authors.lastname: Bemis
authors.forename: Paul D
authors.initials: PD
authors.lastname: Kingsley
authors.forename: Jenna M
authors.initials: JM
authors.lastname: Frame
authors.forename: Anne D
authors.initials: AD
authors.lastname: Koniski
authors.forename: Yuhchyau
authors.initials: Y
authors.lastname: Chen
authors.forename: Jacqueline P
authors.initials: JP
authors.lastname: Williams
authors.forename: Kathleen E
authors.initials: KE
authors.lastname: McGrath
authors.forename: Stephen D
authors.initials: SD
authors.lastname: Dertinger
authors.forename: James
authors.initials: J
authors.lastname: Palis
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000528:radiation effects; D051023:BH3 Interacting Domain Death Agonist Protein / Q000235:genetics; D002453:Cell Cycle / Q000528:radiation effects; D002454:Cell Differentiation / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D004900:Erythroblasts / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects; D041905:Erythroid Cells / Q000166:cytology / Q000378:metabolism / Q000528:radiation effects*; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000528:radiation effects; D051379:Mice; D008810:Mice, Inbred C57BL; D011833:Radiation Injuries, Experimental / Q000503:physiopathology*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors; D014916:Whole-Body Irradiation; D051028:bcl-2-Associated X Protein / Q000235:genetics; D051020:bcl-X Protein / Q000235:genetics
chemical_list: D051023:BH3 Interacting Domain Death Agonist Protein; C494827:Bax protein, mouse; C494812:Bcl2l1 protein, mouse; C494815:Bid protein, mouse; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein