title: CD34 is a specific marker of mature murine mast cells.
abstract: OBJECTIVE
  CD34 is a 90- to 120-kDa cell surface sialomucin that is widely used for the enrichment of human hematopoietic stem cells (HSCs) because of its selective expression on progenitor cells and absence on mature hematopoietic cells. Recently we found that CD34 is the prototypic member of a family of three proteins with similar structure and gene organization. In light of this observation, we further examined the distribution of CD34 family members in the mouse.
  
  
  METHODS
  Hematopoietic cell lines and primary tissues were evaluated for CD34 mRNA expression by Northern blot and protein expression by cell surface immunofluorescence. To confirm specific reactivity of the CD34 antibody, cells from CD34-deficient mice were used as controls.
  
  
  RESULTS
  Although CD34 mRNA was undetectable in all murine progenitor cell lines tested, high level expression was detected for bone marrow-derived mast cells (BMMCs). Likewise, cell surface immunofluorescence confirmed that CD34 is expressed by BMMCs and by in vivo peritoneal mast cells. No protein expression was observed for CD34-deficient mast cells. In addition, our data show that mast cells highly express the stem cell antigen Sca-1 and the well-known stem cell and mast cell antigen c-kit.
  
  
  CONCLUSIONS
  Our results demonstrate that, contrary to current dogma, CD34 is expressed by one mature hematopoietic lineage: mast cells. Our data also demonstrate that antigenically, murine mast cells and their precursors closely resemble HSCs and suggest caution should be used in the phenotypic characterization of HSCs to prevent mast cell contamination of stem cell preparations.
authors.affiliation: The Biomedical Research Centre, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Erin
authors.initials: E
authors.lastname: Drew
authors.forename: Helen
authors.initials: H
authors.lastname: Merkens
authors.forename: Shierley
authors.initials: S
authors.lastname: Chelliah
authors.forename: Regis
authors.initials: R
authors.lastname: Doyonnas
authors.forename: Kelly M
authors.initials: KM
authors.lastname: McNagny
mesh_terms: D000818:Animals; D018952:Antigens, CD34 / Q000032:analysis* / Q000235:genetics; D015415:Biomarkers; D001854:Bone Marrow Cells / Q000166:cytology / Q000276:immunology; D002454:Cell Differentiation; D002460:Cell Line; D002478:Cells, Cultured; D005434:Flow Cytometry; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D008407:Mast Cells / Q000166:cytology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D012333:RNA, Messenger / Q000235:genetics; D012680:Sensitivity and Specificity; D014158:Transcription, Genetic
chemical_list: D018952:Antigens, CD34; D015415:Biomarkers; D012333:RNA, Messenger