Publications

@article{DeWeer2011,

title = {EVI1-mediated down regulation of MIR449A is essential for the survival of EVI1 positive leukaemic cells.},

author = {An De Weer and Joni Van der Meulen and Pieter Rondou and Tom Taghon and Torsten A Konrad and Katleen De Preter and Pieter Mestdagh and Tom Van Maerken and Nadine Van Roy and Marta Jeison and Isaac Yaniv and Barbara Cauwelier and Lucien Noens and Hélène-Antoine Poirel and Peter Vandenberghe and Frédéric Lambert and Anne De Paepe and Maria García Sánchez and Maria Odero and Bruno Verhasselt and Jan Philippé and Joke Vandesompele and Rotraud Wieser and Nicole Dastugue and Pieter Van Vlierberghe and Bruce Poppe and Frank Speleman},

doi = {10.1111/j.1365-2141.2011.08737.x},

issn = {1365-2141},

year  = {2011},

date = {2011-08-01},

journal = {British journal of haematology},

volume = {154},

pages = {337--348},

abstract = {Chromosomal rearrangements involving the MECOM (MDS1 and EVI1 complex) locus are recurrent genetic events in myeloid leukaemia and are associated with poor prognosis. In this study, we assessed the role of MECOM locus protein EVI1 in the transcriptional regulation of microRNAs (miRNAs) involved in the leukaemic phenotype. For this, we profiled expression of 366 miRNAs in 38 MECOM-rearranged patient samples, normal bone marrow controls and MECOM (EVI1) knock down/re-expression models. Cross-comparison of these miRNA expression profiling data showed that MECOM rearranged leukaemias are characterized by down regulation of MIR449A. Reconstitution of MIR449A expression in MECOM-rearranged cell line models induced apoptosis resulting in a strong decrease in cell viability. These effects might be mediated in part by MIR449A regulation of NOTCH1 and BCL2, which are shown here to be bona fide MIR449A targets. Finally, we confirmed that MIR449A repression is mediated through direct promoter occupation of the EVI1 transcriptional repressor. In conclusion, this study reveals MIR449A as a crucial direct target of the MECOM locus protein EVI1 involved in the pathogenesis of MECOM-rearranged leukaemias and unravels NOTCH1 and BCL2 as important novel targets of MIR449A. This EVI1-MIR449A-NOTCH1/BCL2 regulatory axis might open new possibilities for the development of therapeutic strategies in this poor prognostic leukaemia subgroup.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{Taveirne2011,

title = {Inhibitory receptors specific for MHC class I educate murine NK cells but not CD8αα intestinal intraepithelial T lymphocytes.},

author = {Sylvie Taveirne and Jessica Filtjens and Els Van Ammel and Veerle De Colvenaer and Tessa Kerre and Tom Taghon and Bart Vandekerckhove and Jean Plum and Werner Held and Georges Leclercq},

doi = {10.1182/blood-2011-01-331124},

issn = {1528-0020},

year  = {2011},

date = {2011-07-01},

journal = {Blood},

volume = {118},

pages = {339--347},

abstract = {The engagement of inhibitory receptors specific for major histocompatibility complex class I (MHC-I) molecules educates natural killer (NK) cells, meaning the improvement of the response of activation receptors to subsequent stimulation. It is not known whether inhibitory MHC-I receptors educate only NK cells or whether they improve the responsiveness of all cell types, which express them. To address this issue, we analyzed the expression of inhibitory MHC-I receptors on intestinal intraepithelial lymphocytes (iIELs) and show that T-cell receptor (TCR)-αβ CD8αα iIELs express multiple inhibitory receptors specific for MHC-I molecules, including CD94/NKG2A, Ly49A, and Ly49G2. However, the presence of MHC-I ligand for these receptors did not improve the response of iIELs to activation via the TCR. The absence of iIEL education by MHC-I receptors was not related to a lack of inhibitory function of these receptors in iIELs and a failure of these receptors to couple to the TCR. Thus, unlike NK cells, iIELs do not undergo an MHC-I-guided education process. These data suggest that education is an NK cell-specific function of inhibitory MHC-I receptors.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{Taveirne2011a,

title = {Langerhans cells are not required for epidermal Vgamma3 T cell homeostasis and function.},

author = {Sylvie Taveirne and Veerle De Colvenaer and Tina Van Den Broeck and Els Van Ammel and Clare L Bennett and Tom Taghon and Bart Vandekerckhove and Jean Plum and Björn E Clausen and Daniel H Kaplan and Georges Leclercq},

doi = {10.1189/jlb.1010581},

issn = {1938-3673},

year  = {2011},

date = {2011-07-01},

journal = {Journal of leukocyte biology},

volume = {90},

pages = {61--68},

abstract = {This study tested the hypothesis that Vγ3 TCR-bearing T cells are influenced by LCs. Vγ3 T cells and LCs are located in the epidermis of mice. Vγ3 T cells represent the main T cell population in the skin epithelium and play a crucial role in maintaining the skin integrity, whereas LCs are professional APCs. Although Vγ3 T cells and LCs form an interdigitating network in the epidermis, not much is known about their reciprocal influence and/or interdependence. We used two different LC-deficient mouse models, in which LCs are constitutively or inducibly depleted, to investigate the role of LCs in maturation, homeostasis, and function of Vγ3 T cells. We show that Vγ3 T cell numbers are unaltered by LC deficiency, and Vγ3 T cells isolated from LC-deficient mice are phenotypically and upon in vitro stimulation, functionally indistinguishable from Vγ3 T cells isolated from WT mice based on their cytotoxic potential and cytokine production. Additionally, in vivo skin-wounding experiments show no major difference in response of Vγ3 T cells to wounding in the absence or presence of LCs. These observations indicate that Vγ3 T cells develop and function independently of LCs.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{Mavrakis2011,

title = {A cooperative microRNA-tumor suppressor gene network in acute T-cell lymphoblastic leukemia (T-ALL).},

author = {Konstantinos J Mavrakis and Joni Van Der Meulen and Andrew L Wolfe and Xiaoping Liu and Evelien Mets and Tom Taghon and Aly A Khan and Manu Setty and Manu Setti and Pieter Rondou and Peter Vandenberghe and Eric Delabesse and Yves Benoit and Nicholas B Socci and Christina S Leslie and Pieter Van Vlierberghe and Frank Speleman and Hans-Guido Wendel},

doi = {10.1038/ng.858},

issn = {1546-1718},

year  = {2011},

date = {2011-06-01},

journal = {Nature genetics},

volume = {43},

pages = {673--678},

abstract = {The importance of individual microRNAs (miRNAs) has been established in specific cancers. However, a comprehensive analysis of the contribution of miRNAs to the pathogenesis of any specific cancer is lacking. Here we show that in T-cell acute lymphoblastic leukemia (T-ALL), a small set of miRNAs is responsible for the cooperative suppression of several tumor suppressor genes. Cross-comparison of miRNA expression profiles in human T-ALL with the results of an unbiased miRNA library screen allowed us to identify five miRNAs (miR-19b, miR-20a, miR-26a, miR-92 and miR-223) that are capable of promoting T-ALL development in a mouse model and which account for the majority of miRNA expression in human T-ALL. Moreover, these miRNAs produce overlapping and cooperative effects on tumor suppressor genes implicated in the pathogenesis of T-ALL, including IKAROS (also known as IKZF1), PTEN, BIM, PHF6, NF1 and FBXW7. Thus, a comprehensive and unbiased analysis of miRNA action in T-ALL reveals a striking pattern of miRNA-tumor suppressor gene interactions in this cancer.},

keywords = {},

pubstate = {epublish},

tppubtype = {article}

}

@article{DeSmedt2011,

title = {T-lymphoid differentiation potential measured in vitro is higher in CD34+CD38-/lo hematopoietic stem cells from umbilical cord blood than from bone marrow and is an intrinsic property of the cells.},

author = {Magda De Smedt and Georges Leclercq and Bart Vandekerckhove and Tessa Kerre and Tom Taghon and Jean Plum},

doi = {10.3324/haematol.2010.036343},

issn = {1592-8721},

year  = {2011},

date = {2011-05-01},

journal = {Haematologica},

volume = {96},

pages = {646--654},

abstract = {Human bone marrow and umbilical cord blood are sources of allogeneic hematopoietic stem cells for transplantation, which is a life-saving treatment in a variety of diseases but is burdened by delayed T-cell reconstitution. Observational studies evaluating T-cell reconstitution in post-transplant recipients suggest that cord blood hematopoietic stem cells have a more effective capacity for T-cell reconstitution. This study focuses on the comparison of the capacity of cord blood and bone marrow hematopoietic stem cells to generate T cells in vitro. Hematopoietic stem cells were cultured in OP9-delta-like-1 and OP9-green fluorescent protein co-cultures to estimate T and myeloid generation capacity, respectively. Phenotypic markers of T-lineage or myeloid differentiation were measured by flow cytometry and used to analyze their kinetics as a function of culture time. Hematopoietic stem cells were labeled with carboxyfluorescein diacetate succinamidyl ester and analyzed after culture to track their phenotypic progression in consecutive generations. Mixed OP9-delta-like-1 co-cultures were done with either carboxyfluorescein diacetate succinamidyl ester-labeled bone marrow and unlabeled cord blood hematopoietic stem cells, or vice versa, to evaluate their mutual influence on T-lineage differentiation. The T-cell potential of hematopoietic stem cells was addressed quantitatively by limiting dilution analysis. Bulk cultures showed faster and more extensive T-cell differentiation by cord blood hematopoietic stem cells. Furthermore, the T-lymphoid differentiation capacity of cord blood and bone marrow hematopoietic stem cells can be discriminated very early based on the coordinated expression of CD34 and CD7. Mixing experiments with cord blood hematopoietic stem cells and bone marrow hematopoietic stem cells showed that these differences are cell intrinsic. Quantitative clonal analyses demonstrated that CD34(+)CD38(-/lo) hematopoietic stem cells from cord blood contained a two-fold higher T-lineage generation capacity than CD34(+)CD38(-/lo) bone marrow hematopoietic stem cells, whereas the myeloid differentiation was similar. Our data shows that cord blood hematopoietic stem cells have higher T-lymphoid differentiation potential than bone marrow hematopoietic stem cells and that this property is cell autonomous.},

keywords = {},

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tppubtype = {article}

}

@article{Klinakis2011,

title = {A novel tumour-suppressor function for the Notch pathway in myeloid leukaemia.},

author = {Apostolos Klinakis and Camille Lobry and Omar Abdel-Wahab and Philmo Oh and Hiroshi Haeno and Silvia Buonamici and Inge van De Walle and Severine Cathelin and Thomas Trimarchi and Elisa Araldi and Cynthia Liu and Sherif Ibrahim and Miroslav Beran and Jiri Zavadil and Argiris Efstratiadis and Tom Taghon and Franziska Michor and Ross L Levine and Iannis Aifantis},

doi = {10.1038/nature09999},

issn = {1476-4687},

year  = {2011},

date = {2011-05-01},

journal = {Nature},

volume = {473},

pages = {230--233},

abstract = {Notch signalling is a central regulator of differentiation in a variety of organisms and tissue types. Its activity is controlled by the multi-subunit γ-secretase (γSE) complex. Although Notch signalling can play both oncogenic and tumour-suppressor roles in solid tumours, in the haematopoietic system it is exclusively oncogenic, notably in T-cell acute lymphoblastic leukaemia, a disease characterized by Notch1-activating mutations. Here we identify novel somatic-inactivating Notch pathway mutations in a fraction of patients with chronic myelomonocytic leukaemia (CMML). Inactivation of Notch signalling in mouse haematopoietic stem cells (HSCs) results in an aberrant accumulation of granulocyte/monocyte progenitors (GMPs), extramedullary haematopoieisis and the induction of CMML-like disease. Transcriptome analysis revealed that Notch signalling regulates an extensive myelomonocytic-specific gene signature, through the direct suppression of gene transcription by the Notch target Hes1. Our studies identify a novel role for Notch signalling during early haematopoietic stem cell differentiation and suggest that the Notch pathway can play both tumour-promoting and -suppressive roles within the same tissue.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{VandeWalle2011,

title = {Jagged2 acts as a Delta-like Notch ligand during early hematopoietic cell fate decisions.},

author = {Inge Van de Walle and Greet De Smet and Martina Gärtner and Magda De Smedt and Els Waegemans and Bart Vandekerckhove and Georges Leclercq and Jean Plum and Jon C Aster and Irwin D Bernstein and Cynthia J Guidos and Bruno Kyewski and Tom Taghon},

doi = {10.1182/blood-2010-06-290049},

issn = {1528-0020},

year  = {2011},

date = {2011-04-01},

journal = {Blood},

volume = {117},

pages = {4449--4459},

abstract = {Notch signaling critically mediates various hematopoietic lineage decisions and is induced in mammals by Notch ligands that are classified into 2 families, Delta-like (Delta-like-1, -3 and -4) and Jagged (Jagged1 and Jagged2), based on structural homology with both Drosophila ligands Delta and Serrate, respectively. Because the functional differences between mammalian Notch ligands were still unclear, we have investigated their influence on early human hematopoiesis and show that Jagged2 affects hematopoietic lineage decisions very similarly as Delta-like-1 and -4, but very different from Jagged1. OP9 coculture experiments revealed that Jagged2, like Delta-like ligands, induces T-lineage differentiation and inhibits B-cell and myeloid development. However, dose-dependent Notch activation studies, gene expression analysis, and promoter activation assays indicated that Jagged2 is a weaker Notch1-activator compared with the Delta-like ligands, revealing a Notch1 specific signal strength hierarchy for mammalian Notch ligands. Strikingly, Lunatic-Fringe- mediated glycosylation of Notch1 potentiated Notch signaling through Delta-like ligands and also Jagged2, in contrast to Jagged1. Thus, our results reveal a unique role for Jagged1 in preventing the induction of T-lineage differentiation in hematopoietic stem cells and show an unexpected functional similarity between Jagged2 and the Delta-like ligands.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

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@article{Vandekerckhove2011,

title = {In vitro generation of immune cells from pluripotent stem cells.},

author = {Bart Vandekerckhove and Stijn Vanhee and Stefanie Van Coppernolle and Sylvia Snauwaert and Imke Velghe and Tom Taghon and Georges Leclercq and Tessa Kerre and Jean Plum},

doi = {10.2741/3800},

issn = {2768-6698},

year  = {2011},

date = {2011-01-01},

journal = {Frontiers in bioscience (Landmark edition)},

volume = {16},

pages = {1488--1504},

abstract = {Stem cell transplant recipients and acquired or inherited immune-deficiency patients could benefit from the infusion of B, T and/or NK cells. These lymphoid cells can be generated in vitro from bone marrow derived CD34+CD45+ hematopoietic stem cells (HSC). The number of cells that can be obtained in this way is limited especially in the adult. An alternative source may therefore constitute human pluripotent stem cells (PSC) such as embryonic (hESC) or induced pluripotent stem cells (hiPSC). Here, we focus on present knowledge on the generation of lymphoid cells from hESC. The two main obstacles for the generation of clinically relevant immune cells are the failure to generate from hESC long-term repopulating HSC which could be kept in culture for prolonged time; and insufficient knowledge of the selection process which generates mature T cells from CD4 CD8 double positive (DP) precursors in vitro.},

keywords = {},

pubstate = {epublish},

tppubtype = {article}

}

@article{DeColvenaer2010,

title = {Continuous CD27 triggering in vivo strongly reduces NK cell numbers.},

author = {Veerle De Colvenaer and Sylvie Taveirne and Jörg Hamann and Alex M de Bruin and Magda De Smedt and Tom Taghon and Bart Vandekerckhove and Jean Plum and René van Lier and Georges Leclercq},

doi = {10.1002/eji.200939251},

issn = {1521-4141},

year  = {2010},

date = {2010-04-01},

journal = {European journal of immunology},

volume = {40},

pages = {1107--1117},

abstract = {NK cells are important mediators of the early defense. In mice, immature and mature NK (mNK) cells constitutively express the TNF receptor family member CD27; however, mNK cells eventually lose CD27 expression and become resting NK cells. Interaction of CD27 with its ligand, CD70, enhances proliferation and effector functions of NK cells. We used mice that constitutively express CD70 on B cells (CD70-Tg) to study the in vivo effects of continuous triggering of CD27 on NK cells. Continuous CD70-CD27 interaction resulted in strongly down-modulated CD27 expression on NK cells and gradually reduced absolute NK cell numbers. This reduction was most prominent in the mNK cell subpopulation and was at least partially due to increased apoptosis. Residual NK cells showed lower expression of activating Ly49 receptors and normal (liver) or decreased (spleen) IFN-gamma production. Nevertheless, NK cells from CD70-Tg mice displayed higher YAC-1 killing capacities. CD70-Tg NK cells exhibited up-regulated expression of NKG2D, which is in accordance with the increased YAC-1 lysis, as this is mainly NKG2D-dependent. Taken together, this study is the first to demonstrate that continuous CD70 triggering of CD27 on NK cells in vivo results in a severe reduction of NK cells. On a single cell basis, however, residual NK cells display enhanced cytotoxicity.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{VanVlierberghe2010,

title = {PHF6 mutations in T-cell acute lymphoblastic leukemia.},

author = {Pieter Van Vlierberghe and Teresa Palomero and Hossein Khiabanian and Joni Van der Meulen and Mireia Castillo and Nadine Van Roy and Barbara De Moerloose and Jan Philippé and Sara González-García and María L Toribio and Tom Taghon and Linda Zuurbier and Barbara Cauwelier and Christine J Harrison and Claire Schwab and Markus Pisecker and Sabine Strehl and Anton W Langerak and Jozef Gecz and Edwin Sonneveld and Rob Pieters and Elisabeth Paietta and Jacob M Rowe and Peter H Wiernik and Yves Benoit and Jean Soulier and Bruce Poppe and Xiaopan Yao and Carlos Cordon-Cardo and Jules Meijerink and Raul Rabadan and Frank Speleman and Adolfo Ferrando},

doi = {10.1038/ng.542},

issn = {1546-1718},

year  = {2010},

date = {2010-04-01},

journal = {Nature genetics},

volume = {42},

pages = {338--342},

abstract = {Tumor suppressor genes on the X chromosome may skew the gender distribution of specific types of cancer. T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy with an increased incidence in males. In this study, we report the identification of inactivating mutations and deletions in the X-linked plant homeodomain finger 6 (PHF6) gene in 16% of pediatric and 38% of adult primary T-ALL samples. Notably, PHF6 mutations are almost exclusively found in T-ALL samples from male subjects. Mutational loss of PHF6 is importantly associated with leukemias driven by aberrant expression of the homeobox transcription factor oncogenes TLX1 and TLX3. Overall, these results identify PHF6 as a new X-linked tumor suppressor in T-ALL and point to a strong genetic interaction between PHF6 loss and aberrant expression of TLX transcription factors in the pathogenesis of this disease.},

keywords = {},

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tppubtype = {article}

}

@article{VanCoppernolle2009,

title = {Functionally mature CD4 and CD8 TCRalphabeta cells are generated in OP9-DL1 cultures from human CD34+ hematopoietic cells.},

author = {Stefanie Van Coppernolle and Greet Verstichel and Frank Timmermans and Imke Velghe and David Vermijlen and Magda De Smedt and Georges Leclercq and Jean Plum and Tom Taghon and Bart Vandekerckhove and Tessa Kerre},

doi = {10.4049/jimmunol.0900714},

issn = {1550-6606},

year  = {2009},

date = {2009-10-01},

journal = {Journal of immunology (Baltimore, Md. : 1950)},

volume = {183},

pages = {4859--4870},

abstract = {Human CD34(+) hematopoietic precursor cells cultured on delta-like ligand 1 expressing OP9 (OP9-DL1) stromal cells differentiate to T lineage cells. The nature of the T cells generated in these cultures has not been studied in detail. Since these cultures do not contain thymic epithelial cells which are the main cell type mediating positive selection in vivo, generation of conventional helper CD4(+) and cytotoxic CD8(+) TCRalphabeta cells is not expected. Phenotypically mature CD27(+)CD1(-) TCRgammadelta as well as TCRalphabeta cells were generated in OP9-DL1 cultures. CD8 and few mature CD4 single-positive TCRalphabeta cells were observed. Mature CD8 single-positive cells consisted of two subpopulations: one expressing mainly CD8alphabeta and one expressing CD8alphaalpha dimers. TCRalphabeta CD8alphaalpha and TCRgammadelta cells both expressed the IL2Rbeta receptor constitutively and proliferated on IL-15, a characteristic of unconventional T cells. CD8alphabeta(+) and CD4(+) TCRalphabeta cells were unresponsive to IL-15, but could be expanded upon TCR stimulation as mature CD8alphabeta(+) and CD4(+) T cells. These T cells had the characteristics of conventional T cells: CD4(+) cells expressed ThPOK, CD40L, and high levels of IL-2 and IL-4; CD8(+) cells expressed Eomes, Runx3, and high levels of granzyme, perforin, and IFN-gamma. Induction of murine or human MHC class I expression on OP9-DL1 cells had no influence on the differentiation of mature CD8(+) cells. Similarly, the presence of dendritic cells was not required for the generation of mature CD4(+) or CD8(+) T cells. These data suggest that positive selection of these cells is induced by interaction between T precursor cells.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{Timmermans2009,

title = {Generation of T cells from human embryonic stem cell-derived hematopoietic zones.},

author = {Frank Timmermans and Imke Velghe and Lieve Vanwalleghem and Magda De Smedt and Stefanie Van Coppernolle and Tom Taghon and Harry D Moore and Georges Leclercq and Anton W Langerak and Tessa Kerre and Jean Plum and Bart Vandekerckhove},

doi = {10.4049/jimmunol.0803670},

issn = {1550-6606},

year  = {2009},

date = {2009-06-01},

journal = {Journal of immunology (Baltimore, Md. : 1950)},

volume = {182},

pages = {6879--6888},

abstract = {Human embryonic stem cells (hESC) are pluripotent stem cells. A major challenge in the field of hESC is the establishment of specific differentiation protocols that drives hESC down a particular lineage fate. So far, attempts to generate T cells from hESC in vitro were unsuccessful. In this study, we show that T cells can be generated in vitro from hESC-derived hematopoietic precursor cells present in hematopoietic zones (HZs). These zones are morphologically similar to blood islands during embryonic development, and are formed when hESC are cultured on OP9 stromal cells. Upon subsequent transfer of these HZs on OP9 cells expressing high levels of Delta-like 1 and in the presence of growth factors, cells expand and differentiate to T cells. Furthermore, we show that T cells derive exclusively from a CD34(high)CD43(low) population, further substantiating the notion that hESC-derived CD34(high)CD43(low) cells are formed in HZs and are the only population containing multipotent hematopoietic precursor cells. Differentiation to T cells sequentially passes through the physiological intermediates: CD34(+)CD7(+) T/NK committed, CD7(+)CD4(+)CD8(-) immature single positive, CD4(+)CD8(+) double positive, and finally CD3(+)CD1(-)CD27(+) mature T cell stages. TCRalphabeta(+) and TCRgammadelta(+) T cells are generated. Mature T cells are polyclonal, proliferate, and secrete cytokines in response to mitogens. This protocol for the de novo generation of T cells from hESC could be clinically and scientifically relevant.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{Taghon2009,

title = {Notch signaling is required for proliferation but not for differentiation at a well-defined beta-selection checkpoint during human T-cell development.},

author = {Tom Taghon and Inge Van de Walle and Greet De Smet and Magda De Smedt and Georges Leclercq and Bart Vandekerckhove and Jean Plum},

doi = {10.1182/blood-2008-07-168906},

issn = {1528-0020},

year  = {2009},

date = {2009-04-01},

journal = {Blood},

volume = {113},

pages = {3254--3263},

abstract = {Notch signaling is absolutely required for beta-selection during mouse T-cell development, both for differentiation and proliferation. In this report, we investigated whether Notch has an equally important role during human T-cell development. We show that human CD34(+) thymocytes can differentiate into CD4(+)CD8beta(+) double positive (DP) thymocytes in the absence of Notch signaling. While these DP cells phenotypically resemble human beta-selected cells, they lack a T-cell receptor (TCR)-beta chain. Therefore, we characterized the beta-selection checkpoint in human T-cell development, using CD28 as a differential marker at the immature single positive CD4(+)CD3(-)CD8alpha(-) stage. Through intracellular TCR-beta staining and gene expression analysis, we show that CD4(+)CD3(-)CD8alpha(-)CD28(+) thymocytes have passed the beta-selection checkpoint, in contrast to CD4(+)CD3(-)CD8alpha(-)CD28(-) cells. These CD4(+)CD3(-)CD8alpha(-)CD28(+) thymocytes can efficiently differentiate into CD3(+)TCRalphabeta(+) human T cells in the absence of Notch signaling. Importantly, preselection CD4(+)CD3(-)CD8alpha(-)CD28(-) thymocytes can also differentiate into CD3(+)TCRalphabeta(+) human T cells without Notch activation when provided with a rearranged TCR-beta chain. Proliferation of human thymocytes, however, is clearly Notch-dependent. Thus, we have characterized the beta-selection checkpoint during human T-cell development and show that human thymocytes require Notch signaling for proliferation but not for differentiation at this stage of development.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{VandeWalle2009,

title = {An early decrease in Notch activation is required for human TCR-alphabeta lineage differentiation at the expense of TCR-gammadelta T cells.},

author = {Inge Van de Walle and Greet De Smet and Magda De Smedt and Bart Vandekerckhove and Georges Leclercq and Jean Plum and Tom Taghon},

doi = {10.1182/blood-2008-06-164871},

issn = {1528-0020},

year  = {2009},

date = {2009-03-01},

journal = {Blood},

volume = {113},

pages = {2988--2998},

abstract = {Although well characterized in the mouse, the role of Notch signaling in the human T-cell receptor alphabeta (TCR-alphabeta) versus TCR-gammadelta lineage decision is still unclear. Although it is clear in the mouse that TCR-gammadelta development is less Notch dependent compared with TCR-alphabeta differentiation, retroviral overexpression studies in human have suggested an opposing role for Notch during human T-cell development. Using the OP9-coculture system, we demonstrate that changes in Notch activation are differentially required during human T-cell development. High Notch activation promotes the generation of T-lineage precursors and gammadelta T cells but inhibits differentiation toward the alphabeta lineage. Reducing the amount of Notch activation rescues alphabeta-lineage differentiation, also at the single-cell level. Gene expression analysis suggests that this is mediated by differential sensitivities of Notch target genes in response to changes in Notch activation. High Notch activity increases DTX1, NRARP, and RUNX3 expression, genes that are down-regulated during alphabeta-lineage differentiation. Furthermore, increased interleukin-7 levels cannot compensate for the Notch dependent TCR-gammadelta development. Our results reveal stage-dependent molecular changes in Notch signaling that are critical for normal human T-cell development and reveal fundamental molecular differences between mouse and human.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{Taghon2008,

title = {Molecular mechanisms that control mouse and human TCR-alphabeta and TCR-gammadelta T cell development.},

author = {Tom Taghon and Ellen V Rothenberg},

doi = {10.1007/s00281-008-0134-3},

issn = {1863-2297},

year  = {2008},

date = {2008-12-01},

journal = {Seminars in immunopathology},

volume = {30},

pages = {383--398},

abstract = {Following specification of hematopoietic precursor cells into the T cell lineage, several developmental options remain available to the immature thymocytes. The paradigm is that the outcome of the T cell receptor rearrangements and the corresponding T cell receptor signaling events will be predominant to determine the first of these choices: the alphabeta versus gammadelta T cell pathways. Here, we review the thymus-derived environmental signals, the transcriptional mediators, and other molecular mechanisms that are also involved in this decision in both the mouse and human. We discuss the differences in cellular events between the alphabeta and gammadelta developmental pathways and try to correlate these with a corresponding complexity of the molecular mechanisms that support them.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{VanDenBroeck2008,

title = {Ly49E-dependent inhibition of natural killer cells by urokinase plasminogen activator.},

author = {Tina Van Den Broeck and Frederik Stevenaert and Sylvie Taveirne and Veronique Debacker and Christel Vangestel and Bart Vandekerckhove and Tom Taghon and Patrick Matthys and Jean Plum and Werner Held and Mieke Dewerchin and Wayne M Yokoyama and Georges Leclercq},

doi = {10.1182/blood-2008-06-164350},

issn = {1528-0020},

year  = {2008},

date = {2008-12-01},

journal = {Blood},

volume = {112},

pages = {5046--5051},

abstract = {The Ly49 natural killer (NK)-cell receptor family comprises both activating and inhibitory members, which recognize major histocompatibility complex (MHC) class I or MHC class I-related molecules and are involved in target recognition. As previously shown, the Ly49E receptor fails to bind to a variety of soluble or cell-bound MHC class I molecules, indicating that its ligand is not an MHC class I molecule. Using BWZ.36 reporter cells, we demonstrate triggering of Ly49E by the completely distinct, non-MHC-related protein urokinase plasminogen activator (uPA). uPA is known to be secreted by a variety of cells, including epithelial and hematopoietic cells, and levels are up-regulated during tissue remodeling, infections, and tumorigenesis. Here we show that addition of uPA to Ly49E-positive adult and fetal NK cells inhibits interferon-gamma secretion and reduces their cytotoxic potential, respectively. These uPA-mediated effects are Ly49E-dependent, as they are reversed by addition of anti-Ly49E monoclonal antibody and by down-regulation of Ly49E expression using RNA interference. Our results suggest that uPA, besides its established role in fibrinolysis, tissue remodeling, and tumor metastasis, could be involved in NK cell-mediated immune surveillance and tumor escape.},

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pubstate = {ppublish},

tppubtype = {article}

}

@article{DeSmedt2007,

title = {Notch signaling induces cytoplasmic CD3 epsilon expression in human differentiating NK cells.},

author = {Magda De Smedt and Tom Taghon and Inge Van de Walle and Greet De Smet and Georges Leclercq and Jean Plum},

doi = {10.1182/blood-2007-03-082206},

issn = {0006-4971},

year  = {2007},

date = {2007-10-01},

journal = {Blood},

volume = {110},

pages = {2696--2703},

abstract = {It has been proposed that heterogeneity in natural killer (NK)-cell phenotype and function can be achieved through distinct thymic and bone marrow pathways of NK-cell development. Here, we show a link between Notch signaling and the generation of intracellular CD3epsilon (cyCD3)-expressing NK cells, a cell population that can be detected in vivo. Differentiation of human CD34(+) cord blood progenitors in IL-15-supplemented fetal thymus organ culture or OP9-Delta-like 1 (DL1) coculture resulted in a high percentage of cyCD3(+) NK cells that was blocked by the gamma-secretase inhibitor DAPT. The requirement for Notch signaling to generate cyCD3(+) NK cells was further illustrated by transduction of CD34(+) cord blood (CB) cells with either the active intracellular part of Notch or the dominant-negative mutant of mastermind-like protein 1 that resulted in the generation of NK cells with respectively high or low frequencies of cyCD3. Human thymic CD34(+) progenitor cells displayed the potential to generate cyCD3(+) NK cells, even in the absence of Notch/DL1 signaling. Peripheral blood NK cells were unable to induce cyCD3 expression after DL1 exposure, indicating that Notch-dependent cyCD3 expression can only be achieved during the early phase of NK-cell differentiation.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{Taghon2007,

title = {Mast cell lineage diversion of T lineage precursors by the essential T cell transcription factor GATA-3.},

author = {Tom Taghon and Mary A Yui and Ellen V Rothenberg},

doi = {10.1038/ni1486},

issn = {1529-2908},

year  = {2007},

date = {2007-08-01},

journal = {Nature immunology},

volume = {8},

pages = {845--855},

abstract = {GATA-3 is essential for T cell development from the earliest stages. However, abundant GATA-3 can drive T lineage precursors to a non-T cell fate, depending on Notch signaling and developmental stage. Here, overexpression of GATA-3 blocked the survival of pro-T cells when Notch-Delta signals were present but enhanced viability in their absence. In fetal thymocytes at the double-negative 1 (DN1) stage and DN2 stage but not those at the DN3 stage, overexpression of GATA-3 rapidly induced respecification to the mast cell lineage with high frequency by direct transcriptional 'reprogramming'. Normal DN2 thymocytes also showed mast cell potential when interleukin 3 and stem cell factor were added in the absence of Notch signaling. Our results suggest a close relationship between the pro-T cell and mast cell programs and a previously unknown function for Notch in T lineage fidelity.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{Smits2007,

title = {Tumor necrosis factor promotes T-cell at the expense of B-cell lymphoid development from cultured human CD34+ cord blood cells.},

author = {Kaatje Smits and Magda De Smedt and Evelien Naessens and Greet De Smet and Veronique Stove and Tom Taghon and Jean Plum and Bruno Verhasselt},

doi = {10.1016/j.exphem.2007.04.009},

issn = {0301-472X},

year  = {2007},

date = {2007-08-01},

journal = {Experimental hematology},

volume = {35},

pages = {1272--1278},

abstract = {Human CD34+ cord blood (CB) cells are hematopoietic progenitors useful for stem cell transplantation, even after ex vivo expansion. We investigated the effect of tumor necrosis factor (TNF) on lymphoid development from cultured CD34+ CB cells. Human CD34+ CB cells were cultured in cytokine mixes with or without TNF. Preculture during 60 hours was followed by in vitro differentiation assays, including fetal thymus organ culture and coculture on murine stromal MS-5 cells. In a next step, experiments were extended to CD34+CD38- and CD34+CD38+ CB cells and prolonged preculture. Preculture in the presence of TNF improved differentiation into T cells and diminished the ability to generate B cells, while NK potential and myeloid development were unaffected. Sorted CD34+CD38- CB cells were more potent T-cell precursors after preculture in TNF, compared to CD34+CD38+ CB cells. In precultured CD34+CD38- CB cells, TNF increased GATA3 but decreased EBF1 expression, in line with the skewed lymphoid differentiation induced by TNF. However, when preculture in the presence of TNF was extended to 1 week, T-cell precursors were lost. After short-term culture of CD34+ CB cells in the presence of TNF, T-cell generation is stimulated at the expense of B-cell generation. T-cell progenitors are enriched in the CD34+CD38- fraction. These results have implications on the culture conditions to be used for CB CD34+ cells prior to transplantation.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}

@article{Tydell2007,

title = {Molecular dissection of prethymic progenitor entry into the T lymphocyte developmental pathway.},

author = {Chace C Tydell and Elizabeth-Sharon David-Fung and Jonathan E Moore and Lee Rowen and Tom Taghon and Ellen V Rothenberg},

doi = {10.4049/jimmunol.179.1.421},

issn = {0022-1767},

year  = {2007},

date = {2007-07-01},

journal = {Journal of immunology (Baltimore, Md. : 1950)},

volume = {179},

pages = {421--438},

abstract = {Notch signaling activates T lineage differentiation from hemopoietic progenitors, but relatively few regulators that initiate this program have been identified, e.g., GATA3 and T cell factor-1 (TCF-1) (gene name Tcf7). To identify additional regulators of T cell specification, a cDNA library from mouse Pro-T cells was screened for genes that are specifically up-regulated in intrathymic T cell precursors as compared with myeloid progenitors. Over 90 genes of interest were identified, and 35 of 44 tested were confirmed to be more highly expressed in T lineage precursors relative to precursors of B and/or myeloid lineage. To a remarkable extent, however, expression of these T lineage-enriched genes, including zinc finger transcription factor, helicase, and signaling adaptor genes, was also shared by stem cells (Lin(-)Sca-1(+)Kit(+)CD27(-)) and multipotent progenitors (Lin(-)Sca-1(+)Kit(+)CD27(+)), although down-regulated in other lineages. Thus, a major fraction of these early T lineage genes are a regulatory legacy from stem cells. The few genes sharply up-regulated between multipotent progenitors and Pro-T cell stages included those encoding transcription factors Bcl11b, TCF-1 (Tcf7), and HEBalt, Notch target Deltex1, Deltex3L, Fkbp5, Eva1, and Tmem131. Like GATA3 and Deltex1, Bcl11b, Fkbp5, and Eva1 were dependent on Notch/Delta signaling for induction in fetal liver precursors, but only Bcl11b and HEBalt were up-regulated between the first two stages of intrathymic T cell development (double negative 1 and double negative 2) corresponding to T lineage specification. Bcl11b was uniquely T lineage restricted and induced by Notch/Delta signaling specifically upon entry into the T lineage differentiation pathway.},

keywords = {},

pubstate = {ppublish},

tppubtype = {article}

}