Publications

@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.},
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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.},
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}

@article{Franco2006,
title = {Notch/Delta signaling constrains reengineering of pro-T cells by PU.1.},
author = {Christopher B Franco and Deirdre D Scripture-Adams and Irina Proekt and Tom Taghon and Angela H Weiss and Mary A Yui and Stephanie L Adams and Rochelle A Diamond and Ellen V Rothenberg},
doi = {10.1073/pnas.0601188103},
issn = {0027-8424},
year = {2006},
date = {2006-08-01},
journal = {Proceedings of the National Academy of Sciences of the United States of America},
volume = {103},
pages = {11993--11998},
abstract = {PU.1 is essential for early stages of mouse T cell development but antagonizes it if expressed constitutively. Two separable mechanisms are involved: attenuation and diversion. Dysregulated PU.1 expression inhibits pro-T cell survival, proliferation, and passage through beta-selection by blocking essential T cell transcription factors, signaling molecules, and Rag gene expression, which expression of a rearranged T cell antigen receptor transgene cannot rescue. However, Bcl2 transgenic cells are protected from this attenuation and may even undergo beta-selection, as shown by PU.1 transduction of defined subsets of Bcl2 transgenic fetal thymocytes with differentiation in OP9-DL1 and OP9 control cultures. The outcome of PU.1 expression in these cells depends on Notch/Delta signaling. PU.1 can efficiently divert thymocytes toward a myeloid-like state with multigene regulatory changes, but Notch/Delta signaling vetoes diversion. Gene expression analysis distinguishes sets of critical T lineage regulatory genes with different combinatorial responses to PU.1 and Notch/Delta signals, suggesting particular importance for inhibition of E proteins, Myb, and/or Gfi1 (growth factor independence 1) in diversion. However, Notch signaling only protects against diversion of cells that have undergone T lineage specification after Thy-1 and CD25 up-regulation. The results imply that in T cell precursors, Notch/Delta signaling normally acts to modulate and channel PU.1 transcriptional activities during the stages from T lineage specification until commitment.},
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}

@article{DavidFung2006,
title = {Progression of regulatory gene expression states in fetal and adult pro-T-cell development.},
author = {Elizabeth-Sharon David-Fung and Mary A Yui and Marissa Morales and Hua Wang and Tom Taghon and Rochelle A Diamond and Ellen V Rothenberg},
doi = {10.1111/j.0105-2896.2006.00355.x},
issn = {0105-2896},
year = {2006},
date = {2006-02-01},
journal = {Immunological reviews},
volume = {209},
pages = {212--236},
abstract = {Precursors entering the T-cell developmental pathway traverse a progression of states characterized by distinctive patterns of gene expression. Of particular interest are regulatory genes, which ultimately control the dwell time of cells in each state and establish the mechanisms that propel them forward to subsequent states. Under particular genetic and developmental circumstances, the transitions between these states occur with different timing, and environmental feedbacks may shift the steady-state accumulations of cells in each state. The fetal transit through pro-T-cell stages is faster than in the adult and subject to somewhat different genetic requirements. To explore causes of such variation, this review presents previously unpublished data on differentiation gene activation in pro-T cells of pre-T-cell receptor-deficient mutant mice and a quantitative comparison of the profiles of transcription factor gene expression in pro-T-cell subsets of fetal and adult wildtype mice. Against a background of consistent gene expression, several regulatory genes show marked differences between fetal and adult expression profiles, including those encoding two basic helix-loop-helix antagonist Id factors, the Ets family factor SpiB and the Notch target gene Deltex1. The results also reveal global differences in regulatory alterations triggered by the first T-cell receptor-dependent selection events in fetal and adult thymopoiesis.},
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@article{Taghon2006,
title = {Developmental and molecular characterization of emerging beta- and gammadelta-selected pre-T cells in the adult mouse thymus.},
author = {Tom Taghon and Mary A Yui and Rashmi Pant and Rochelle A Diamond and Ellen V Rothenberg},
doi = {10.1016/j.immuni.2005.11.012},
issn = {1074-7613},
year = {2006},
date = {2006-01-01},
journal = {Immunity},
volume = {24},
pages = {53--64},
abstract = {The first checkpoint in T cell development, beta selection, has remained incompletely characterized for lack of specific surface markers. We show that CD27 is upregulated in DN3 thymocytes initiating beta selection, concomitant with intracellular TCR-beta expression. Clonal analysis determined that CD27high DN3 cells generate CD4+CD8+ progeny with more than 90% efficiency, faster and more efficiently than the CD27low majority. CD27 upregulation also occurs in gammadelta-selected DN3 thymocytes in TCR-beta-/- mice and in IL2-GFP transgenic reporter mice where GFP marks the earliest emerging TCR-gammadelta cells from DN3 thymocytes. With CD27 to distinguish pre- and postselection DN3 cells, a detailed gene expression analysis defined regulatory changes associated with checkpoint arrest, with beta selection, and with gammadelta selection. gammadelta selection induces higher CD5, Egr, and Runx3 expression as compared to beta selection, but it triggers less proliferation. Our results also reveal differences in Notch/Delta dependence at the earliest stages of divergence between developing alphabeta and gammadelta T-lineage cells.},
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@article{Taghon2005,
title = {Delayed, asynchronous, and reversible T-lineage specification induced by Notch/Delta signaling.},
author = {Tom N Taghon and Elizabeth-Sharon David and Juan Carlos Zúñiga-Pflücker and Ellen V Rothenberg},
doi = {10.1101/gad.1298305},
issn = {0890-9369},
year = {2005},
date = {2005-04-01},
journal = {Genes & development},
volume = {19},
pages = {965--978},
abstract = {Using the OP9-DL1 system to deliver temporally controlled Notch/Delta signaling, we show that pluripotent hematolymphoid progenitors undergo T-lineage specification and B-lineage inhibition in response to Notch signaling in a delayed and asynchronous way. Highly enriched progenitors from fetal liver require > or =3 d to begin B- or T-lineage differentiation. Clonal switch-culture analysis shows that progeny of some single cells can still generate both B- and T-lineage cells, after 1 wk of continuous delivery or deprivation of Notch/Delta signaling. Notch signaling induces T-cell genes and represses B-cell genes, but kinetics of activation of lineage-specific transcription factors are significantly delayed after induction of Notch target genes and can be temporally uncoupled from the Notch response. In the cells that initiate T-cell differentiation and gene expression most slowly in response to Notch/Delta signaling, Notch target genes are induced to the same level as in the cells that respond most rapidly. Early lineage-specific gene expression is also rapidly reversible in switch cultures. Thus, while necessary to induce and sustain T-cell development, Notch/Delta signaling is not sufficient for T-lineage specification and commitment, but instead can be permissive for the maintenance and proliferation of uncommitted progenitors that are omitted in binary-choice models.},
keywords = {},
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@article{Rothenberg2005,
title = {Molecular genetics of T cell development.},
author = {Ellen V Rothenberg and Tom Taghon},
doi = {10.1146/annurev.immunol.23.021704.115737},
issn = {0732-0582},
year = {2005},
date = {2005-01-01},
journal = {Annual review of immunology},
volume = {23},
pages = {601--649},
abstract = {T cell development is guided by a complex set of transcription factors that act recursively, in different combinations, at each of the developmental choice points from T-lineage specification to peripheral T cell specialization. This review describes the modes of action of the major T-lineage-defining transcription factors and the signal pathways that activate them during intrathymic differentiation from pluripotent precursors. Roles of Notch and its effector RBPSuh (CSL), GATA-3, E2A/HEB and Id proteins, c-Myb, TCF-1, and members of the Runx, Ets, and Ikaros families are critical. Less known transcription factors that are newly recognized as being required for T cell development at particular checkpoints are also described. The transcriptional regulation of T cell development is contrasted with that of B cell development, in terms of their different degrees of overlap with the stem-cell program and the different roles of key transcription factors in gene regulatory networks leading to lineage commitment.},
note = {Grant numbers: NASA NAG2-1588, NSF MCB-9983129.},
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@article{DeSmedt2002,
title = {Active form of Notch imposes T cell fate in human progenitor cells.},
author = {Magda De Smedt and Katia Reynvoet and Tessa Kerre and Tom Taghon and Bruno Verhasselt and Bart Vandekerckhove and Georges Leclercq and Jean Plum},
doi = {10.4049/jimmunol.169.6.3021},
issn = {0022-1767},
year = {2002},
date = {2002-09-01},
journal = {Journal of immunology (Baltimore, Md. : 1950)},
volume = {169},
pages = {3021--3029},
abstract = {The crucial role of Notch signaling in cell fate decisions in hematopoietic lineage and T lymphocyte development has been well established in mice. Overexpression of the intracellular domain of Notch mediates signal transduction of the protein. By retroviral transduction of this constitutively active truncated intracellular domain in human CD34+ umbilical cord blood progenitor cells, we were able to show that, in coculture with the stromal MS-5 cell line, depending on the cytokines added, the differentiation toward CD19+ B lymphocytes was blocked, the differentiation toward CD14+ monocytes was inhibited, and the differentiation toward CD56+ NK cells was favored. The number of CD7+cyCD3+ cells, a phenotype similar to T/NK progenitor cells, was also markedly increased. In fetal thymus organ culture, transduced CD34+ progenitor cells from umbilical cord blood cells or from thymus consistently generated more TCR-gammadelta T cells, whereas the other T cell subpopulations were largely unaffected. Interestingly, when injected in vivo in SCID-nonobese diabetic mice, the transduced cells generated ectopically human CD4+CD8+ TCR-alphabeta cells in the bone marrow, cells that are normally only present in the thymus, and lacked B cell differentiation potential. Our results show unequivocally that, in human, Notch signaling inhibits the monocyte and B cell fate, promotes the T cell fate, and alters the normal T cell differentiation pathway compatible with a pretumoral state.},
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tppubtype = {article}
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@article{Taghon2002,
title = {HOX-A10 regulates hematopoietic lineage commitment: evidence for a monocyte-specific transcription factor.},
author = {Tom Taghon and Frank Stolz and Magda De Smedt and Maggy Cnockaert and Bruno Verhasselt and Jean Plum and Georges Leclercq},
doi = {10.1182/blood.v99.4.1197},
issn = {0006-4971},
year = {2002},
date = {2002-02-01},
journal = {Blood},
volume = {99},
pages = {1197--1204},
abstract = {Homeobox genes are well known for their crucial role during embryogenesis but have also been found to be critically involved in normal and leukemic hematopoiesis. Because most previous studies focused on the role of aberrant HOX gene expression in leukemogenesis and because HOX-A10 is expressed in human CD34(+) precursor cells, this study investigated whether HOX-A10 also plays a pivotal role in normal hematopoietic-lineage determination. The effect of enforced expression of this transcription factor on hematopoietic differentiation of highly purified human cord-blood progenitors was examined by using in vitro assays. In fetal thymic organ cultures, a dramatic reduction in cells expressing high levels of HOX-A10 was observed, along with absence of thymocytes positive for CD3(+) T-cell receptor alphabeta. Furthermore, in MS-5 stromal cell cultures, there was a 7-fold reduction in the number of natural killer cells and a 9-fold reduction in the number of B cells, thus showing a profound defect in differentiation toward the lymphoid lineage in HOX-A10-transduced progenitors. In contrast, the number of CD14(+) monocytic cells in the stromal cell culture was 6-fold higher, suggesting an enhanced differentiation toward the myeloid differentiation pathway of HOX-A10-transduced progenitors. However, there was a slight reduction in the number of CD15(+) granulocytic cells, which were blocked in their final maturation. These data show that HOX-A10 can act as an important key regulator of lineage determination in human hematopoietic progenitor cells.},
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