title: PU.1 opposes IL-7-dependent proliferation of developing B cells with involvement of the direct target gene bruton tyrosine kinase.
abstract: Deletion of genes encoding the E26 transformation-specific transcription factors PU.1 and Spi-B in B cells (CD19-CreΔPB mice) leads to impaired B cell development, followed by B cell acute lymphoblastic leukemia at 100% incidence and with a median survival of 21 wk. However, little is known about the target genes that explain leukemogenesis in these mice. In this study we found that immature B cells were altered in frequency in the bone marrow of preleukemic CD19-CreΔPB mice. Enriched pro-B cells from CD19-CreΔPB mice induced disease upon transplantation, suggesting that these were leukemia-initiating cells. Bone marrow cells from preleukemic CD19-CreΔPB mice had increased responsiveness to IL-7 and could proliferate indefinitely in response to this cytokine. Bruton tyrosine kinase (BTK), a negative regulator of IL-7 signaling, was reduced in preleukemic and leukemic CD19-CreΔPB cells compared with controls. Induction of PU.1 expression in cultured CD19-CreΔPB pro-B cell lines induced Btk expression, followed by reduced STAT5 phosphorylation and early apoptosis. PU.1 and Spi-B regulated Btk directly as shown by chromatin immunoprecipitation analysis. Ectopic expression of BTK was sufficient to induce apoptosis in cultured pro-B cells. In summary, these results suggest that PU.1 and Spi-B activate Btk to oppose IL-7 responsiveness in developing B cells.
authors.affiliation: Centre for Human Immunology, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada;
authors.forename: Darah A
authors.initials: DA
authors.lastname: Christie
authors.affiliation: Centre for Human Immunology, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada;
authors.forename: Li S
authors.initials: LS
authors.lastname: Xu
authors.affiliation: Centre for Human Immunology, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada;
authors.forename: Shereen A
authors.initials: SA
authors.lastname: Turkistany
authors.affiliation: Centre for Human Immunology, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada;
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Solomon
authors.affiliation: Centre for Human Immunology, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada;
authors.forename: Stephen K H
authors.initials: SK
authors.lastname: Li
authors.affiliation: Centre for Human Immunology, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada;
authors.forename: Edmund
authors.initials: E
authors.lastname: Yim
authors.affiliation: Department of Animal Care and Veterinary Services, University of Western Ontario, London, Ontario N6A 5C1, Canada;
authors.forename: Ian
authors.initials: I
authors.lastname: Welch
authors.affiliation: Robarts Research Institute, University of Western Ontario, London, Ontario N6A 5C1, Canada; Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada; and.
authors.forename: Gillian I
authors.initials: GI
authors.lastname: Bell
authors.affiliation: Robarts Research Institute, University of Western Ontario, London, Ontario N6A 5C1, Canada; Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario N6A 5C1, Canada; and Division of Genetics and Development, Children's Health Research Institute, Lawson Research Institute, London, Ontario N6C 2R5, Canada.
authors.forename: David A
authors.initials: DA
authors.lastname: Hess
authors.affiliation: Centre for Human Immunology, Department of Microbiology and Immunology, University of Western Ontario, London, Ontario N6A 5C1, Canada; Division of Genetics and Development, Children's Health Research Institute, Lawson Research Institute, London, Ontario N6C 2R5, Canada rdekoter@uwo.ca.
authors.forename: Rodney P
authors.initials: RP
authors.lastname: DeKoter
mesh_terms: D000077329:Agammaglobulinaemia Tyrosine Kinase; D000818:Animals; D018941:Antigens, CD19 / Q000235:genetics / Q000276:immunology; D017209:Apoptosis / Q000235:genetics / Q000276:immunology*; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology*; D049109:Cell Proliferation; D017353:Gene Deletion; D015870:Gene Expression; D015851:Interleukin-7 / Q000235:genetics / Q000276:immunology*; D051379:Mice; D018345:Mice, Knockout; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000276:immunology*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000276:immunology*; D015534:Trans-Activators / Q000235:genetics / Q000276:immunology*; D000099232:Proto-Oncogene Protein Spi-1
chemical_list: D000077329:Agammaglobulinaemia Tyrosine Kinase; D018941:Antigens, CD19; D015851:Interleukin-7; D011505:Protein-Tyrosine Kinases; D011518:Proto-Oncogene Proteins; D015534:Trans-Activators; D000099232:Proto-Oncogene Protein Spi-1; C000625949:BTK protein, human; C000625951:Btk protein, mouse