title: Expansion of hematopoietic stem cell phenotype and activity in Trp53-null mice.
abstract: OBJECTIVE
  To study the effects of transformation-related protein 53 (Trp53) and other genes on hematopoiesis and hematopoietic stem cells (HSCs).
  
  
  METHODS
  Frequencies of murine bone marrow cells (BMCs) with the Lin(-)Sca-1(+)c-kit(+)CD34- phenotype were analyzed by flow cytometry, and were increased in mice with germ-line deletion of the Trp53 (Trp53(-/-)) gene but not in 25 other deletions of genes involved in cell cycling, development, cancer, or hematopoiesis. Therefore, Trp53(-/-) and wild-type Trp53(+/+) mice were compared using the following assays: complete blood counts, day-9 colony-forming unit spleen (CFU-S), and competitive repopulation. In the latter assay, donor repopulating ability was analyzed at one, three, and five months, while recipient survival and recipient blood and bone marrow cell composition were analyzed at five months, after transplantation.
  
  
  RESULTS
  In comparison to wild-type controls, Trp53(-/-) mice had normal blood and bone marrow cell counts, increased CD11b(+), and decreased CD45R(+) cell proportions in blood and bone marrow, twice as many Lin(-)Sca-1(+)c-kit(+)CD34(-) BMCs, and 37% more day-9 CFU-S. In the competitive repopulation assay, Trp53(-/-) BMCs engrafted lethally irradiated recipients two to four times better than Trp53(+/+) BMCs. The Trp53(-/-) engraftment advantage increased with time in the recipients. Recipients of Trp53(-/-) donors had two to three times more Lin(-)Sca-1(+)c-kit(+)CD34(-) BMCs than recipients of Trp53(+/+) donors at five months after transplantation. However, only 44% of recipients of Trp53(-/-) donors survived five months after trans-plantation, compared with 92% of recipients of Trp53(+/+) donors.
  
  
  CONCLUSIONS
  The Trp53-null allele expands bone marrow Lin(-)Sca-1(+)c-kit(+)CD34(-) cells and the overall activity of HSCs; however, it increases recipient mortality.
authors.affiliation: The Jackson Laboratory, 600 Main Street, Bar Harbor, Maine 04609, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: TeKippe
authors.forename: David E
authors.initials: DE
authors.lastname: Harrison
authors.forename: Jichun
authors.initials: J
authors.lastname: Chen
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells; D016026:Bone Marrow Transplantation; D039481:CD11b Antigen / Q000032:analysis; D002452:Cell Count; D002455:Cell Division; D005434:Flow Cytometry; D006085:Graft Survival; D006410:Hematopoiesis; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D016130:Immunophenotyping; D017493:Leukocyte Common Antigens / Q000032:analysis; D051379:Mice; D018345:Mice, Knockout; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000502:physiology*
chemical_list: D039481:CD11b Antigen; D016159:Tumor Suppressor Protein p53; D017493:Leukocyte Common Antigens