scholarly journals Zebrafish mafbb Mutants Display Osteoclast Over-Activation and Bone Deformity Resembling Osteolysis in MCTO Patients

Biomolecules ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 480
Author(s):  
Yujie Han ◽  
Weihao Shao ◽  
Dan Zhong ◽  
Cui Ma ◽  
Xiaona Wei ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Cell Differentiation ◽  
Bone Development ◽  
Myeloid Differentiation ◽  
Missense Mutations ◽  
Wild Type ◽  
Bone Deformity ◽  
Tarsal Bones

Multicentric carpotarsal osteolysis (MCTO) is a rare skeletal dysplasia with osteolysis at the carpal and tarsal bones. Heterozygous missense mutations in the transcription factor MAFB are found in patients with MCTO. MAFB is reported to negatively regulate osteoclastogenesis in vitro. However, the in vivo function of MAFB and its relation to MCTO remains unknown. In this study, we generated zebrafish MAFB homolog mafbb mutant utilizing CRISPR/Cas9 technology. Mafbb deficient zebrafish demonstrated enhanced osteoclast cell differentiation and abnormal cartilage and bone development resembling MCTO patients. It is known that osteoclasts are hematopoietic cells derived from macrophages. Loss of mafbb caused selective expansion of definitive macrophages and myeloid cells, supporting that mafbb restricts myeloid differentiation in vivo. We also demonstrate that MAFB MCTO mutations failed to rescue the defective osteoclastogenesis in mafbb−/− embryos, but did not affect osteoclast cells in wild type embryos. The mechanism of MCTO mutations is likely haploinsufficiency. Zebrafish mafbb mutant provides a useful model to study the function of MAFB in osteoclastogenesis and the related MCTO disease.

Pathophysiology of Thrombocytopenia and Anemia in Mice Lacking Transcription Factor NF-E2

Blood ◽  
1999 ◽  
Vol 94 (9) ◽  
pp. 3037-3047 ◽  
Author(s):  
Jack Levin ◽  
Jin-Peng Peng ◽  
Georgiann R. Baker ◽  
Jean-Luc Villeval ◽  
Patrick Lecine ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Fetal Life ◽  
Wild Type ◽  
Cell Lineages ◽  
Cell Fragments ◽  
Proliferation Potential

Abstract Expression of the p45 subunit of transcription factor NF-E2 is restricted to selected blood cell lineages, including megakaryocytes and developing erythrocytes. Mice lacking p45 NF-E2 show profound thrombocytopenia, resulting from a late arrest in megakaryocyte differentiation, and a number of red blood cell defects, including anisocytosis and hypochromia. Here we report results of studies aimed to explore the pathophysiology of these abnormalities. Mice lacking NF-E2 produce very few platelet-like particles that display highly disorganized ultrastructure and respond poorly to platelet agonists, features consistent with the usually lethal hemorrhage in these animals. Thrombocytopenia was evident during fetal life and was not corrected by splenectomy in adults. Surprisingly, fetal NF-E2–deficient megakaryocyte progenitors showed reduced proliferation potential in vitro. Thus, NF-E2 is required for regulated megakaryocyte growth as well as for differentiation into platelets. All the erythroid abnormalities were reproduced in lethally irradiated wild-type recipients of hematopoietic cells derived from NF-E2-null fetuses. Whole blood from mice lacking p45 NF-E2 showed numerous small red blood cell fragments; however, survival of intact erythrocytes in vivo was indistinguishable from control mice. Considered together, these observations indicate a requirement for NF-E2 in generating normal erythrocytes. Despite impressive splenomegaly at baseline, mice lacking p45 NF-E2 survived splenectomy, which resulted in increased reticulocyte numbers. This reveals considerable erythroid reserve within extra-splenic sites of hematopoiesis and suggests a role for the spleen in clearing abnormal erythrocytes. Our findings address distinct aspects of the requirements for NF-E2 in blood cell homeostasis and establish its roles in proper differentiation of megakaryocytes and erythrocytes.

Thrombopoietin Regulates Proliferation and Maturation of Murine Mast Cells.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 1707-1707
Author(s):  
Giovanni Migliaccio ◽  
Barbara Ghinassi ◽  
Lucia Centurione ◽  
Maria Zingariello ◽  
Lucia Bianchi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Mast Cell ◽  
Cell Differentiation ◽  
Growth Factor ◽  
Mast Cells ◽  
Wild Type ◽  
Connective Tissues ◽  
Immature Cells

Abstract Megakaryocytopoiesis is regulated by extrinsic (interaction of the growth factor thrombopoietin, TPO with its receptor Mpl) and intrinsic (interaction between the trascription factors GATA-1 and Fog-1) factors. The observation that mice impaired for GATA-1 expression (i.e. harbouring the GATA-1low mutation) are defective not only in megakaryocyte maturation but also in mast cell differentiation (Migliaccio et al. J Exp Med197:281, 2003), led us to investigate whether TPO might control mast cell differentiation as well. We first observed that mice genetically unable to responde to TPO (Mplnull mice) express in the connective tissues 5 times more mast cells than their normal littermates. Then, we analysed the effects on mast cell differentiation of in vivo treatment with TPO. Normal mice, and their GATA-1low littermates, were injected i.p. with TPO (100 μg/kg/day per 5 days, kindly provided by Kirin Brewery, Japan) and the number of immature (Toluidinepos) and mature (AlcianBlue/Saphraninepos) mast cells present in the connective tissues of the animals, as well as the frequency of GATA-1pos and TUNELpos mast cells, was evaluated 14 days after treatment. In wild-type animals, TPO reduced the presence of GATA-1 in mast cells (by immuno-histochemistry) and increased the number of immature cells (from 320±28 to 852±60) and of those undergoing apoptosis (from 16±1 to 600±43). In contrast, in GATA-1low animals, TPO-treatment induced the expression of GATA-1 in mast cells while decreased the number of immature cells (from 1100±72 to 427±29) as well as that of apoptotic cells (from 600±45 to 60±2). The role of TPO on mast cell differentiation were further confirmed by the analysis of the effects exerted by the growth factor on in vitro differentiation of bone marrow derived mast cells (BMMC). In these experiments, wild type bone marrow and spleen cells were cultured for 21 days with SCF and IL-3 with or without TPO and BMMC differentiation measured on the basis of the number of cells expressing the phenotype c-kithigh/CD34high and FcεRIpos. In cultures stimulated with SCF and IL-3, all the cells expressed the phenotype c-kithigh/CD34high and FcεRIpos. In contrast, in cultures supplemented also with SCF, IL-3 and TPO, only 25% of the cells were c-kithigh/CD34high and none of them was FcεRIpos. These results establish a role for TPO in the control of mast cell differentiation (possibly by modulating the GATA-1 content of the cells) and unveil further similarities between the mechanism(s) controlling megakaryocyte and mast cell differentiation.

GA Binding Protein (GABP) Is Required for Development and Maturation of Myeloid Cells.

Blood ◽  
2004 ◽  
Vol 104 (11) ◽  
pp. 776-776
Author(s):  
Zhongfa Yang ◽  
Alan G. Rosmarin
Keyword(s):  
Cell Cycle ◽  
Transcription Factor ◽  
Target Genes ◽  
Embryonic Stem ◽  
Myeloid Cells ◽  
Transactivation Domain ◽  
Wild Type ◽  
Floxed Allele

Abstract GABP is an ets transcription factor that regulates transcription of key myeloid genes, including CD18 (beta2 leukocyte integrin), neutrophil elastase, lysozyme, and other key mediators of the inflammatory response; it is also known to regulate important cell cycle control genes. GABP consists of two distinct and unrelated proteins that, together, form a functional transcription factor complex. GABPalpha (GABPa) is an ets protein that binds to DNA; it forms a tetrameric complex by recruiting its partner, GABPbeta (GABPb), which contains the transactivation domain. GABPa is a single copy gene in both the human and murine genomes and it is the only protein that can recruit GABPb to DNA. We cloned GABPa from a murine genomic BAC library and prepared a targeting vector in which exon 9 (which encodes the GABPa ets domain) was flanked by loxP (floxed) recombination sites. The targeting construct was electroporated into embryonic stem cells, homologous recombinants were implanted into pseudopregnant mice, heterozygous floxed GABPa mice were identified, and intercrossing yielded expected Mendelian ratios of wild type, heterozygous, and homozygous floxed GABPa mice. Breeding of heterozygous floxed GABPa mice to CMV-Cre mice (which express Cre recombinase in all tissues) yielded expected numbers of hemizygous mice (only one intact GABPa allele), but no nullizygous (GABPa−/−) mice among 64 pups; we conclude that homozygous deletion of GABPa causes an embryonic lethal defect. To determine the effect of GABPa deletion on myeloid cell development, we bred heterozygous and homozygous floxed mice to LysMCre mice, which express Cre only in myeloid cells. These mice had a normal complement of myeloid cells but, unexpectedly, PCR indicated that their Gr1+ myeloid cells retained an intact (undeleted) floxed GABPa allele. We detected similar numbers of in vitro myeloid colonies from bone marrow of wild type, heterozygous floxed, and homozygous floxed progeny of LysMCre matings. However, PCR of twenty individual in vitro colonies from homozygous floxed mice indicated that they all retained an intact floxed allele. Breeding of floxed GABPa/LysMCre mice with hemizygous mice indicated that retention of a floxed allele was not due to incomplete deletion by LysMCre; rather, it appears that only myeloid cells that retain an intact GABPa allele can survive to mature in vitro or in vivo. We prepared murine embryonic fibroblasts from homozygous floxed mice and efficiently deleted GABPa in vitro. We found striking abnormalities in proliferation and G1/S phase arrest. We used quantitative RT-PCR to identify mechanisms that account for the altered growth of GABPa null cells. We found dramatically reduced expression of known GABP target genes that regulate DNA synthesis and cell cycle that appear to account for the proliferative defect. We conclude that GABPa is required for growth and maturation of myeloid cells and we identified downstream targets that may account for their failure to proliferate and mature in vitro and in vivo.

Differential Activation of Notch1 and Notch2 by Delta1 and Jagged1 Determines Hematopoietic Cell Fate.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 864-864
Author(s):  
Barbara J. Varnum-Finney ◽  
Lia M. Halasz ◽  
Irwin D. Bernstein
Keyword(s):  
T Cell ◽  
Cell Fate ◽  
Side Population ◽  
Hematopoietic Cell ◽  
Myeloid Differentiation ◽  
Wild Type ◽  
Differential Activation ◽  
Notch Ligands

Abstract Spatially restricted in vivo expression of the Notch ligands Delta1 and Jagged1 suggests their differential roles in inducing hematopoietic cell fates, and studies have shown that each induces alternative fates during in vitro culture. We hypothesize that the ligands induce alternative fates via differential activation of Notch1 and/or Notch2. To address this, we assessed fate outcomes of Notch1- and Notch2-deficient murine bone marrow derived lin−Sca-1+c-kit+ Hoescht side population progenitors (LSKSP) after 14-days incubation with either purified Delta1 or Jagged1 in serum containing medium. Ligands consisted of purified Delta1 and Jagged1 extracellular domains fused to HumanIgG1 (Delta1ext-IgG or Jagged1ext-IgG). Equal amounts of ligand, as determined by ELISA, were immobilized to plastic surfaces of culture wells along with fibronectin. Notch deficient cells were generated by infecting either Notch1fl/fl or Notch2fl/fl LSKSP with lentivirus encoding cre recombinase. We show here that both ligands inhibit myeloid differentiation, since after 14 days, LSKSP incubated with either ligand generated multi-log increased numbers of immature progeny with significantly reduced percentages of GR1+ and/or F480+ cells compared to LSKSP incubated with control-IgG. However, only Delta1ext-IgG promotes T-cell progenitor differentiation, since a higher percentage of progeny cultured with Delta1ext-IgG expressed CD25 (37.0+/−0.6%) compared to Jagged1ext-IgG (1.7+/−1.0%; p=0.01). In contrast, Jagged1ext-IgG is less effective at inhibiting myeloid differentiation, since a higher percentage of progeny cultured with Jagged1ext-IgG (2.1+/−0.9%) expressed GR1 and F4/80 compared to Delta1ext-IgG (56.5+/−6.3; p=0.02). Furthermore, Delta1ext-IgG is more effective than Jagged1ext-IgG at inducing Notch activation as measured by increased expression of Notch target Hes1, since we found 3.3-fold more expression of Hes1 mRNA following incubation of LSKSP cells with Delta1ext-IgG compared to Jagged1ext-IgG. We further show that Notch2 is required to prevent myeloid differentiation, since Notch2 deficient LSKSP incubated with either Delta1ext-IgG or Jagged1ext-IgG generated cultures containing fewer numbers of cells and a higher percentage of GR1+ and/or F480+ myeloid progeny (83% with Delta1ext-IgGor 86% with Jagged1ext-IgG) similarly to those generated with control-IgG. Likewise, we found a reduced percentage of immature Sca-1+c-kit+ cells (19.3+/−4.4 or 13.0+/−5.2) than wild-type cells incubating with Delta1ext-IgG or Jagged1ext-IgG (92.2+/−3.0 or 71.0+/−15.0: p=0.004 or p=0.05). We found that Notch1 is required to induce T-cell differentiation, since Notch1 deficient LSKSP incubated with Delta1ext-IgG had a reduced percentage of CD25+ cells compared to wild-type cells (4.4+/−1.9% to 30.3+/− 3.3) even though myeloid differentiation was inhibited. In summary, we show that both Delta1ext-IgG and Jagged1ext-IgG induce signaling via Notch2 to prevent myeloid differentiation, whereas only Delta1ext-IgG induces signaling via Notch1 to promote generation of T-cell progenitors. Our results indicate unique Notch ligands differentially activate Notch1 or Notch2, resulting in alternative cell fate choices and lay a framework for investigating the mechanisms underlying differential activation, including determining the role of Notch modifiers such as Fringe.

GABP Transcription Factor Is Required for Myeloid Cell Development In Vivo.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 374-374 ◽  
Author(s):  
Zhong-fa Yang ◽  
Karen Drumea ◽  
Alan G. Rosmarin
Keyword(s):  
Bone Marrow ◽  
Transcription Factor ◽  
T Cell ◽  
Myeloid Cells ◽  
Myeloid Cell ◽  
Cell Development ◽  
Wild Type ◽  
Ets Domain

Abstract GABP is an ets transcription factor that regulates genes that are required for innate immunity, including CD18 (β2 leukocyte integrin), lysozyme, and neutrophil elastase. GABP consists of two distinct and unrelated proteins. GABPα binds to DNA through its ets domain and recruits GABPβ, which contains the transactivation domain; together, they form a functional tetrameric transcription factor complex. We recently showed that GABP is required for entry into S phase of the cell cycle through its regulation of genes that are required for DNA synthesis and cyclin dependent kinase inhibitors (Yang, et al. Nature Cell Biol9:339, 2007). Furthermore, GABP is an essential component of a retinoic acid responsive myeloid enhanceosome (Resendes and Rosmarin Mol Cell Biol26:3060, 2006). We cloned Gabpa (the gene that encodes mouse Gabpα) from a mouse genomic BAC library and prepared a targeting vector in which the ets domain is flanked by loxP recombination sites (floxed allele). Deletion of both floxed Gabpa alleles causes an early embryonic lethal defect. In order to define the role of Gabpα in myelopoiesis, we bred floxed Gabpa mice to mice that bear the Mx1-Cre transgene, which drives expression of Cre recombinase in response to injection of the synthetic polynucleotide, poly I-C. Deletion of Gabpa dramatically reduced granulocytes and monocytes in the peripheral blood, spleen, and bone marrow, but myeloid cells recovered within weeks. In vitro colony forming assays indicated that myeloid cells in these mice were derived only from Gabpa replete myeloid precursors (that failed to delete both Gabpa alleles), suggesting strong pressure to retain Gabpα in vivo. We used a novel competitive bone marrow transplantation approach to determine if Gabp is required for myeloid cell development in vivo. Sub-lethally irradiated wild-type recipient mice bearing leukocyte marker CD45.1 received equal proportions of bone marrow from wild type CD45.1 donor mice and floxed-Mx1-Cre donor mice that bear CD45.2. Both the CD45.2 (floxed-Mx1-Cre) and CD45.1 (wild type) bone marrow engrafted well. Mice were then injected with pI-pC to induce Cre-mediated deletion of floxed Gabpa. The mature myeloid and T cell compartments were derived almost entirely from wild type CD45.1 cells. This indicates that the proliferation and/or differentiation of myeloid and T cell lineages requires Gabp. In contrast, B cell development was not impaired. We conclude that Gabpa disruption causes a striking loss of myeloid cells in vivo and corroborates prior in vitro data that GABP plays a crucial role in proliferation of myeloid progenitor cells.

Trisomy of the Down Syndrome Critical Region Suppresses Precursor B-Cell Differentiation and Promotes B-Cell Transformation Associated with Altered Expression of Polycomb Repressor Complex 2 Targets

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 115-115
Author(s):  
Andrew A. Lane ◽  
Diederik van Bodegom ◽  
Bjoern Chapuy ◽  
Gabriela Alexe ◽  
Timothy J Sullivan ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Cell Differentiation ◽  
B Cells ◽  
B Cell ◽  
Cell Transformation ◽  
B Cell Differentiation ◽  
Wild Type ◽  
Repressor Complex

Abstract Abstract 115 Extra copies of chromosome 21 (polysomy 21) is the most common somatic aneuploidy in B-cell acute lymphoblastic leukemia (B-ALL), including >90% of cases with high hyperdiploidy. In addition, children with Down syndrome (DS) have a 20-fold increased risk of developing B-ALL, of which ∼60% harbor CRLF2 rearrangements. To examine these associations within genetically defined models, we investigated B-lineage phenotypes in Ts1Rhr mice, which harbor triplication of 31 genes syntenic with the DS critical region (DSCR) on human chr.21. Murine pro-B cell (B220+CD43+) development proceeds sequentially through “Hardy fractions” defined by cell surface phenotype: A (CD24−BP-1−), B (CD24+BP-1−) and then C (CD24+BP-1+). Compared with otherwise isogenic wild-type littermates, Ts1Rhr bone marrow harbored decreased percentages of Hardy fraction B and C cells, indicating that DSCR triplication is sufficient to disrupt the Hardy A-to-B transition. Of note, the same phenotype was reported in human DS fetal liver B-cells, which have a block between the pre-pro- and pro-B cell stages (analogous to Hardy A-to-B). To determine whether DSCR triplication affects B-cell proliferation in vitro, we analyzed colony formation and serial replating in methylcellulose cultures. Ts1Rhr bone marrow (B6/FVB background) formed 2–3-fold more B-cell colonies in early passages compared to bone marrow from wild-type littermates. While wild-type B-cells could not serially replate beyond 4 passages, Ts1Rhr B-cells displayed indefinite serial replating (>10 passages). Ts1Rhr mice do not spontaneously develop leukemia, so we utilized two mouse models to determine whether DSCR triplication cooperates with leukemogenic oncogenes in vivo. First, we generated Eμ-CRLF2 F232C mice, which express the constitutively active CRLF2 mutant solely within B-cells. Like Ts1Rhr B-cells, (but not CRLF2 F232C B-cells) Ts1Rhr/CRLF2 F232C cells had indefinite serial replating potential. In contrast with Ts1Rhr B-cells, Ts1Rhr/CRLF2 F232C B-cells also engrafted into NOD.Scid.IL2Rγ−/− mice and caused fatal and serially transplantable B-ALL. Second, we retrovirally transduced BCR-ABL1 into unselected bone marrow from wild-type and Ts1Rhr mice and transplanted into irradiated wild-type recipients. Transplantation of transduced Ts1Rhr cells (106, 105, or 104) caused fatal B-ALL in recipient mice with shorter latency and increased penetrance compared to recipients of the same number of transduced wild-type cells. By Poisson calculation, the number of B-ALL initiating cells in transduced Ts1Rhr bone marrow was ∼4-fold higher than in wild-type animals (1:60 vs 1:244, P=0.0107). Strikingly, transplantation of individual Hardy A, B, and C fractions after sorting and BCR-ABL1 transduction demonstrated that the increased leukemia-initiating capacity almost completely resides in the Ts1Rhr Hardy B fraction; i.e., the same subset suppressed during Ts1Rhr B-cell differentiation. To define transcriptional determinants of these phenotypes, we performed RNAseq of Ts1Rhr and wild-type B cells in methylcellulose culture (n=3 biologic replicates per genotype). As expected, Ts1Rhr colonies had ∼1.5-fold higher RNA abundance of expressed DSCR genes. We defined a Ts1Rhr signature of the top 200 genes (false discovery rate (FDR) <0.25) differentially expressed compared with wild-type cells. Importantly, this Ts1Rhr signature was significantly enriched (P=0.02) in a published gene expression dataset of DS-ALL compared with non-DS-ALL (Hertzberg et al., Blood 2009). Query of >2,300 signatures in the Molecular Signatures Database (MSigDB) C2 Chemical and Genetic Perturbations with the Ts1Rhr signature identified enrichment in multiple gene sets of polycomb repressor complex (PRC2) targets and H3K27 trimethylation. Most notably, SUZ12 targets within human embryonic stem cells were more highly expressed in Ts1Rhr cells (P=1.2×10−6, FDR=0.003) and the same SUZ12 signature was enriched in patients with DS-ALL compared to non-DS-ALL (P=0.007). In summary, DSCR triplication directly suppresses precursor B-cell differentiation and promotes B-cell transformation both in vitro and by cooperating with proliferative alterations such as CRLF2 activation and BCR-ABL1 in vivo. Pharmacologic modulation of H3K27me3 effectors may overcome the pro-leukemogenic effects of polysomy 21. Disclosures: No relevant conflicts of interest to declare.

Pathophysiology of Thrombocytopenia and Anemia in Mice Lacking Transcription Factor NF-E2

Blood ◽  
1999 ◽  
Vol 94 (9) ◽  
pp. 3037-3047 ◽  
Author(s):  
Jack Levin ◽  
Jin-Peng Peng ◽  
Georgiann R. Baker ◽  
Jean-Luc Villeval ◽  
Patrick Lecine ◽  
...  
Keyword(s):  
Transcription Factor ◽  
Blood Cell ◽  
Red Blood Cell ◽  
Fetal Life ◽  
Wild Type ◽  
Cell Lineages ◽  
Cell Fragments ◽  
Proliferation Potential

Expression of the p45 subunit of transcription factor NF-E2 is restricted to selected blood cell lineages, including megakaryocytes and developing erythrocytes. Mice lacking p45 NF-E2 show profound thrombocytopenia, resulting from a late arrest in megakaryocyte differentiation, and a number of red blood cell defects, including anisocytosis and hypochromia. Here we report results of studies aimed to explore the pathophysiology of these abnormalities. Mice lacking NF-E2 produce very few platelet-like particles that display highly disorganized ultrastructure and respond poorly to platelet agonists, features consistent with the usually lethal hemorrhage in these animals. Thrombocytopenia was evident during fetal life and was not corrected by splenectomy in adults. Surprisingly, fetal NF-E2–deficient megakaryocyte progenitors showed reduced proliferation potential in vitro. Thus, NF-E2 is required for regulated megakaryocyte growth as well as for differentiation into platelets. All the erythroid abnormalities were reproduced in lethally irradiated wild-type recipients of hematopoietic cells derived from NF-E2-null fetuses. Whole blood from mice lacking p45 NF-E2 showed numerous small red blood cell fragments; however, survival of intact erythrocytes in vivo was indistinguishable from control mice. Considered together, these observations indicate a requirement for NF-E2 in generating normal erythrocytes. Despite impressive splenomegaly at baseline, mice lacking p45 NF-E2 survived splenectomy, which resulted in increased reticulocyte numbers. This reveals considerable erythroid reserve within extra-splenic sites of hematopoiesis and suggests a role for the spleen in clearing abnormal erythrocytes. Our findings address distinct aspects of the requirements for NF-E2 in blood cell homeostasis and establish its roles in proper differentiation of megakaryocytes and erythrocytes.

The Ets-1 transcription factor is required for Stat1-mediated T-bet expression and IgG2a class switching in mouse B cells

Blood ◽  
2012 ◽  
Vol 119 (18) ◽  
pp. 4174-4181 ◽  
Author(s):  
Hai Vu Nguyen ◽  
Enguerran Mouly ◽  
Karine Chemin ◽  
Romain Luinaud ◽  
Raymonde Despres ◽  
...  
Keyword(s):  
Transcription Factor ◽  
B Cells ◽  
Molecular Mechanisms ◽  
Wild Type ◽  
Transcriptional Enhancer ◽  
T Box ◽  
Class Switch ◽  
Ifn Γ

Abstract In response to antigens and cytokines, mouse B cells undergo class-switch recombination (CSR) and differentiate into Ig-secreting cells. T-bet, a T-box transcription factor that is up-regulated in lymphocytes by IFN-γ or IL-27, was shown to regulate CSR to IgG2a after T cell–independent B-cell stimulations. However, the molecular mechanisms controlling this process remain unclear. In the present study, we show that inactivation of the Ets-1 transcription factor results in a severe decrease in IgG2a secretion in vivo and in vitro. No T-bet expression was observed in Ets-1–deficient (Ets-1−/−) B cells stimulated with IFN-γ and lipopolysaccharide, and forced expression of T-bet in these cells rescued IgG2a secretion. Furthermore, we identified a transcriptional enhancer in the T-bet locus with an activity in B cells that relies on ETS-binding sites. After IFN-γ stimulation of Ets-1−/− B cells, activated Stat1, which forms a complex with Ets-1 in wild-type cells, no longer binds to the T-bet enhancer or promotes histone modifications at this site. These results demonstrate that Ets-1 is critical for IgG2a CSR and acts as an essential cofactor for Stat1 in the regulation of T-bet expression in B cells.

Two missense mutations identified in venous thrombosis patients impair the inhibitory function of the protein Z dependent protease inhibitor

2012 ◽  
Vol 107 (05) ◽  
pp. 854-863 ◽  
Author(s):  
Nigel P. Birch ◽  
Peter J. Browett ◽  
Paul B. Coughlin ◽  
Anita J. Horvath ◽  
Neil S. Van de Water ◽  
...  
Keyword(s):  
Protease Inhibitor ◽  
Venous Thrombosis ◽  
Nonsense Mutation ◽  
Healthy Controls ◽  
Missense Mutations ◽  
Wild Type ◽  
Protein Z ◽  
Inhibitory Function

SummaryProtein Z-dependent protease inhibitor (ZPI) is a plasma inhibitor of factor (F)Xa and FXIa. In an earlier study, five mutations were identified within the ZPI gene of venous thrombosis patients and healthy controls. Two of these were nonsense mutations and three were missense mutations in important regions of the protein. Here we report that two of these latter three mutations, F145L and Q384R, impair the inhibitory function of ZPI in vitro. Recombinant wild-type and mutant proteins were prepared; stability in response to thermal challenge was similar. Inhibition of FXa in the presence of the cofactor protein Z was reduced 68-fold by the Q384R mutant; inhibition of FXIa by the F145L mutant was reduced two- to three-fold compared to the wild-type ZPI. An analysis of all five ZPI mutations was undertaken in a cohort of venous thrombosis patients (n=550) compared to healthy controls (n=600). Overall, there was a modest increase in incidence of these mutations in the thrombosis group (odds ratio 2.0, 1.05–3.7, p=0.044). However, in contrast to W324X (nonsense mutation), the Q384R missense mutation and R88X nonsense mutation were evenly distributed in patients and controls; F145L was rare. The final mutation (S143Y) was also rare and did not significantly alter ZPI function in laboratory studies. The F145L and particularly the Q384R mutation impaired the function of the coagulation inhibitor ZPI; however, there was no convincing association between these mutations and venous thrombosis risk. The functional role for ZPI in vivo has yet to be clarified.

scholarly journals TFIIA Plays a Role in the Response to Oxidative Stress

2006 ◽  
Vol 5 (7) ◽  
pp. 1081-1090 ◽  
Author(s):  
Susan M. Kraemer ◽  
David A. Goldstrohm ◽  
Ann Berger ◽  
Susan Hankey ◽  
Sherry A. Rovinsky ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Transcription Factor ◽  
Rna Polymerase Ii ◽  
Expression Profiles ◽  
Intracellular Localization ◽  
Regulation Of Gene Expression ◽  
Wild Type ◽  
Mutant Strains

ABSTRACT To characterize the role of the general transcription factor TFIIA in the regulation of gene expression by RNA polymerase II, we examined the transcriptional profiles of TFIIA mutants of Saccharomyces cerevisiae using DNA microarrays. Whole-genome expression profiles were determined for three different mutants with mutations in the gene coding for the small subunit of TFIIA, TOA2. Depending on the particular mutant strain, approximately 11 to 27% of the expressed genes exhibit altered message levels. A search for common motifs in the upstream regions of the pool of genes decreased in all three mutants yielded the binding site for Yap1, the transcription factor that regulates the response to oxidative stress. Consistent with a TFIIA-Yap1 connection, the TFIIA mutants are unable to grow under conditions that require the oxidative stress response. Underexpression of Yap1-regulated genes in the TFIIA mutant strains is not the result of decreased expression of Yap1 protein, since immunoblot analysis indicates similar amounts of Yap1 in the wild-type and mutant strains. In addition, intracellular localization studies indicate that both the wild-type and mutant strains localize Yap1 indistinguishably in response to oxidative stress. As such, the decrease in transcription of Yap1-dependent genes in the TFIIA mutant strains appears to reflect a compromised interaction between Yap1 and TFIIA. This hypothesis is supported by the observations that Yap1 and TFIIA interact both in vivo and in vitro. Taken together, these studies demonstrate a dependence of Yap1 on TFIIA function and highlight a new role for TFIIA in the cellular mechanism of defense against reactive oxygen species.

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