The development of functional B lymphocytes in conditional PU.1 knock-out mice

Polli, Matthew; Dakic, Aleksandar; Light, Amanda; Wu, Li; Tarlinton, David M.; Nutt, Stephen L.

doi:10.1182/blood-2005-01-0283

Cited by 73 publications

(81 citation statements)

References 42 publications

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“…When Sfpi1 is inactivated in HSCs, B cell development is profoundly blocked [5]. In contrast, when Sfpi1 is inactivated in CLPs using a retrovirally expressed Cre recombinase or in committed B cells using Cre recombinase under control of the CD19 promoter, B cell development is minimally affected [5,11,12]. Taken together with our studies, these data suggest that high levels of PU.1 are essential for B cell development.…”

Section: Discussionsupporting

confidence: 71%

“…During commitment to the B cell lineage, PU.1 expression is reduced to lower levels [10]. Conditional knockout studies demonstrated that deletion of Sfpi1 in committed B cell progenitors minimally affects B cell development [11][12][13]. An important question that remains unanswered in these studies is whether high PU.1 activity is required for specification to the B lineage.…”

Section: Introductionmentioning

confidence: 95%

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Reduction in PU.1 activity results in a block to B-cell development, abnormal myeloid proliferation, and neonatal lethality

Houston

Kamath

Schweitzer

et al. 2007

Experimental Hematology

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Objective-It has been demonstrated that high concentration of the transcription factor PU.1 (encoded by Sfpi1) promotes macrophage development, whereas low concentration induces B cell development in vitro. This has led to the hypothesis that lower levels of PU.1 activity are required for B cell than for macrophage development in vivo. We utilized an allele of Sfpi1 (termed BN) with a mutation in the first coding exon which resulted in a reduction of PU.1 expression in order to test this hypothesis. Methods-Using gene targeting in ES cells, two ATG-start site codons of PU.1 were mutated, resulting in reduced PU.1 expression originating from a third start codon. Mice were assayed for phenotypic abnormalities using fluorescence activated cell sorting, microscopy, and colony forming ability. In addition, isolated cells were tested for their differentiation potential in vitro and in vivo.Results-Lymphoid and myeloid cells derived from cultured Sfpi1 BN/BN fetal liver cells had reduced levels of PU.1 expression and activity. B cell development was intrinsically blocked in cells isolated from Sfpi1 BN/BN mice. In addition, myeloid development was impaired in Sfpi1 BN/BN fetal liver. However, neonatal Sfpi1 BN/BN mice had a dramatic expansion and infiltration of immature myeloid cells.Conclusion-Contrary to our original hypothesis, high levels of PU.1 activity are required to induce both myeloid and B cell development. In addition, neonatal mice homozygous for the hypomorphic allele acquire a myeloproliferative disorder and die within 1 month of age.

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Section: Discussionsupporting

confidence: 71%

Section: Introductionmentioning

confidence: 95%

Reduction in PU.1 activity results in a block to B-cell development, abnormal myeloid proliferation, and neonatal lethality

Houston

Kamath

Schweitzer

et al. 2007

Experimental Hematology

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“…PU.1 and its close relative Spi-B are members of the Ets domain-containing transcription factor family that is expressed in hematopoietic cells, including B cells, T cells, and macrophages (27). The specific deletion of PU.1 in the B lineage did not markedly affect B cell development (28). However, although the investigators did not pay much attention in the details of B cell populations, their results revealed that follicular B cells were markedly reduced (to half) in mutant mice (17 6 3.4% versus 33.7 6 2.5% in wild-type control mice), suggesting that further analysis is necessary to determine the role of PU.1 in the survival of mGC B cells.…”

Section: Discussionmentioning

confidence: 99%

Lyn Signaling To Upregulate GANP Is Critical for the Survival of High-Affinity B Cells in Germinal Centers of Lymphoid Organs

Kuwahara

Nakaya

Phimsen

et al. 2012

The Journal of Immunology

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Signals through BCR and costimulatory molecules play essential roles in selecting high-affinity B cells with Ig V-region mutations in the germinal centers (GCs) of peripheral lymphoid organs. Lyn-deficient (lyn−/−) mice show impaired BCR signal triggering for cell proliferation and GC formation, causing hyper-IgM, and display autoimmunity after aging. In this study, we demonstrate that Lyn-mediated signaling to upregulate GANP is essential for the survival of mature GC-like (mGC) B cells with high-affinity type BCR mutations upon Ag immunization. Transgenic ganp expression into lyn−/− mice did not recover the Lyn-deficient phenotype with regard to B cell differentiation, serum Igs, and impaired GC formation in spleens after immunization with nitrophenyl-chicken γ-globulin, but it markedly rescued cell survival of mGC B cells by suppressing DNA damage, thereby increasing the frequency of the Trp33-to-Leu mutation in the IgVH-186.2 region and affinity maturation of nitrophenyl-binding B cells. GANP may play a critical role in Lyn-mediated signaling for the selection of high-affinity B cells in peripheral lymphoid organs.

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“…Second, PU.1 is required for the generation of lymphoid progenitors, and therefore no B cells are detected in PU.1 Ϫ/Ϫ fetal livers (24,25). However, conditional knockout studies indicate that PU.1 is not required for the continued survival and differentiation of B cells once they are generated (24,26,27). One of the consequences of PU.1 deletion in committed B cells is a switch from a B-2 to a B-1 phenotype (27).…”

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confidence: 99%

Spi-C Has Opposing Effects to PU.1 on Gene Expression in Progenitor B Cells

Schweitzer

Huang

Kamath

et al. 2006

The Journal of Immunology

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The Ets transcription factor Spi-C, expressed in B cells and macrophages, is closely related to PU.1 and has the ability to recognize the same DNA consensus sequence. However, the function of Spi-C has yet to be determined. The purpose of this study is to further examine Spi-C activity in B cell development. First, using retroviral vectors to infect PU.1−/− fetal liver progenitors, Spi-C was found to be inefficient at inducing cytokine-dependent proliferation and differentiation of progenitor B (pro-B) cells or macrophages relative to PU.1 or Spi-B. Next, Spi-C was ectopically expressed in fetal liver-derived, IL-7-dependent pro-B cell lines. Wild-type (WT) pro-B cells ectopically expressing Spi-C (WT-Spi-C) have several phenotypic characteristics of pre-B cells such as increased CD25 and decreased c-Kit surface expression. In addition, WT-Spi-C pro-B cells express increased levels of IgH sterile transcripts and reduced levels of expression and transcription of the FcγRIIb gene. Gel-shift analysis suggests that Spi-C, ectopically expressed in pro-B cells, can bind PU.1 consensus sites in the IgH intronic enhancer and FcγRIIb promoter. Transient transfection analysis demonstrated that PU.1 functions to repress the IgH intronic enhancer and activate the FcγRIIb promoter, while Spi-C opposes these activities. WT-Spi-C pro-B cells have reduced levels of dimethylation on lysine 9 of histone H3 within the IgH 3′ regulatory region, indicating that Spi-C can contribute to removal of repressive features in the IgH locus. Overall, these studies suggest that Spi-C may promote B cell differentiation by modulating the activity of PU.1-dependent genes.

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The development of functional B lymphocytes in conditional PU.1 knock-out mice

Cited by 73 publications

References 42 publications

Reduction in PU.1 activity results in a block to B-cell development, abnormal myeloid proliferation, and neonatal lethality

Reduction in PU.1 activity results in a block to B-cell development, abnormal myeloid proliferation, and neonatal lethality

Lyn Signaling To Upregulate GANP Is Critical for the Survival of High-Affinity B Cells in Germinal Centers of Lymphoid Organs

Spi-C Has Opposing Effects to PU.1 on Gene Expression in Progenitor B Cells

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