251
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Fitzsimmons SP, Bernstein RM, Max EE, Skok JA, Shapiro MA. Dynamic changes in accessibility, nuclear positioning, recombination, and transcription at the Ig kappa locus. THE JOURNAL OF IMMUNOLOGY 2007; 179:5264-73. [PMID: 17911612 DOI: 10.4049/jimmunol.179.8.5264] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
The 3-megabase Igkappa locus undergoes differentially controlled nuclear positioning events and chromatin structural changes during the course of B cell development. The temporal association of chromatin structural changes, transcription, and recombination at the Igkappa locus was determined in a murine pre-B cell line that can be induced to recombine at the Igkappa locus and in ex vivo-cultured murine pre-B cells. Additionally, the timing of nuclear positioning relative to the temporal order of chromatin structural changes and recombination and transcription was determined. We demonstrate that before induction, the Igkappa locus was poised for recombination; both alleles were in a contracted state, and the enrichment of histone modifications and germline transcripts of specific Vkappa genes were observed. Histone modifications of the Vkappa genes did not vary upon induction but the levels of modifications correlated with the levels of germline Vkappa gene transcripts and recombination. Upon induction, but before VkappaJkappa recombination, centromeric recruitment of single Igkappa alleles occurred. DNase I sensitivity of the entire locus increased gradually over the course of differentiation while the enrichment of histone modifications downstream of the Vkappa genes was increased in the silencer regions upstream of Jkappa1, within the Igkappa sterile transcript, the kappa constant region, the Ekappai and Ekappa3' enhancers, and the recombining sequence. The ex vivo pre-B cells showed similar patterns of histone modifications across the locus except at the Vkappa genes. In this study, H3 acetylation correlated with levels of germline transcripts while H3 methylation correlated with levels of recombination.
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Affiliation(s)
- Sean P Fitzsimmons
- Division of Monoclonal Antibodies, Food and Drug Administration, Center for Drug Evaluation and Research, Rockville, MD 20852, USA
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252
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Abstract
The activity of the transcription factor paired box gene 5 (Pax5) is essential for many aspects of B lymphopoiesis including the initial commitment to the lineage, immunoglobulin rearrangement, pre-B cell receptor signalling and maintaining cell identity in mature B cells. Deregulated or reduced Pax5 activity has also been implicated in B-cell malignancies both in human disease and mouse models. Candidate gene approaches and biochemical analysis have revealed that Pax5 regulates B lymphopoiesis by concurrently activating B cell-specific gene expression as well as repressing the expression of genes, many of which are associated with non-B cell lineages. These studies have been recently complemented with more exhaustive microarray studies, which have identified and validated a large panel of Pax5 target genes. These target genes reveal a gene regulatory network, with Pax5 at its centre that controls the B-cell gene expression programme.
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253
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Alt FW. From gene amplification to V(D)J recombination and back: a personal account of my early years in B cell biology. Eur J Immunol 2007; 37 Suppl 1:S138-47. [PMID: 17972338 PMCID: PMC2572819 DOI: 10.1002/eji.200737848] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
I have been invited to write a short historical feature in the context of being a co-recipient with Klaus Rajewsky and Fritz Melchers of the 2007 Novartis Prize in Basic Immunology that was given in the general area of the molecular biology of B cells. In this feature, I cover the main points of the short talk that I presented at the Award Ceremony at the International Immunology Congress in Rio de Janeiro, Brazil. This talk focused primarily on the work and people involved early on in generating the models and ideas that have formed the basis for my ongoing efforts in the areas of V(D)J recombination and B cell development.
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Affiliation(s)
- Frederick W Alt
- Howard Hughes Medical Institute, The Children's Hospital, The Immune Disease Institute, Department of Genetics, Harvard Medical School, Boston, MA 02215, USA.
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254
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Wutz A, Gribnau J. X inactivation Xplained. Curr Opin Genet Dev 2007; 17:387-93. [PMID: 17869504 DOI: 10.1016/j.gde.2007.08.001] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2007] [Revised: 08/01/2007] [Accepted: 08/02/2007] [Indexed: 11/21/2022]
Abstract
Random inactivation of one of the two female X chromosomes establishes dosage compensation between XY males and XX females in placental mammals. X inactivation is controlled by the X inactivation center (Xic). Recent advances in genome sequencing show that the Xic has evolved from an ancestral vertebrate gene cluster in placental mammals and has undergone separate rearrangements in marsupials. The Xic ensures that all but one X chromosome per diploid genome are inactivated. Which chromosome remains active is randomly chosen. Pairing of Xic loci on the two X chromosomes and alternate states of the X chromosomes before inactivation have recently been implicated in the mechanism of random choice. Chromosome-wide silencing is then initiated by the noncoding Xist RNA, which evolved with the mammalian Xic and covers the inactive X chromosome.
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Affiliation(s)
- Anton Wutz
- Research Institute of Molecular Pathology, Dr. Bohr-Gasse 7, 1030 Vienna, Austria.
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255
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Murre C. Epigenetics of antigen-receptor gene assembly. Curr Opin Genet Dev 2007; 17:415-21. [PMID: 17920858 PMCID: PMC2151926 DOI: 10.1016/j.gde.2007.08.006] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2007] [Revised: 07/17/2007] [Accepted: 08/17/2007] [Indexed: 02/05/2023]
Abstract
The antigen receptor genes are organized into distinct DNA elements that encode the variable (V), diversity (D) and joining (J) regions. It is now well established that the rearrangement of antigen receptor genes is regulated by developmental-specific modulation of chromatin structure. Further studies involving statistical mechanics should provide physical insight into the physical mechanisms that underlie the association of antigen receptor gene segments.
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Affiliation(s)
- Cornelis Murre
- Division of Biological Sciences, 03777, University of California, San Diego, La Jolla, CA 92093, United States.
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256
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Cobaleda C, Jochum W, Busslinger M. Conversion of mature B cells into T cells by dedifferentiation to uncommitted progenitors. Nature 2007; 449:473-7. [PMID: 17851532 DOI: 10.1038/nature06159] [Citation(s) in RCA: 379] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2007] [Accepted: 08/08/2007] [Indexed: 12/12/2022]
Abstract
Lineage commitment and differentiation to a mature cell type are considered to be unidirectional and irreversible processes under physiological conditions. The commitment of haematopoietic progenitors to the B-cell lineage and their development to mature B lymphocytes critically depend on the transcription factor encoded by the paired box gene 5 (Pax5). Here we show that conditional Pax5 deletion in mice allowed mature B cells from peripheral lymphoid organs to dedifferentiate in vivo back to early uncommitted progenitors in the bone marrow, which rescued T lymphopoiesis in the thymus of T-cell-deficient mice. These B-cell-derived T lymphocytes carried not only immunoglobulin heavy- and light-chain gene rearrangements but also participated as functional T cells in immune reactions. Mice lacking Pax5 in mature B cells also developed aggressive lymphomas, which were identified by their gene expression profile as progenitor cell tumours. Hence, the complete loss of Pax5 in late B cells could initiate lymphoma development and uncovered an extraordinary plasticity of mature peripheral B cells despite their advanced differentiation stage.
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Affiliation(s)
- César Cobaleda
- Research Institute of Molecular Pathology, Vienna Biocenter, Dr. Bohr-Gasse 7, A-1030 Vienna, Austria
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257
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Abstract
T lymphocyte development is directed by a gene-expression program that occurs in the complex nucleoprotein environment of chromatin. This review examines basic principles of chromatin regulation and evaluates ongoing progress toward understanding how the chromatin template is manipulated to control gene expression and gene recombination in developing thymocytes. Special attention is devoted to the loci encoding T cell receptors alpha and beta, T cell coreceptors CD4 and CD8, and the enzyme terminal deoxynucleotidyl transferase. The properties of SATB1, a notable organizer of thymocyte chromatin, are also addressed.
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Affiliation(s)
- Michael S Krangel
- Department of Immunology, Duke University Medical Center, Durham, North Carolina 27710 USA.
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258
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Abstract
The transcription factor Pax5 is a critical regulator of B lymphocyte commitment and identity. In this issue of Immunity, Schebesta et al. (2007) demonstrate how Pax5 activates 170 different genes involved in B cell signaling, adhesion, migration, and maturation.
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Affiliation(s)
- James Hagman
- Integrated Department of Immunology, K516B, National Jewish Medical and Research Center, 1400 Jackson Street, Denver, CO 80206, USA.
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259
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Schebesta A, McManus S, Salvagiotto G, Delogu A, Busslinger GA, Busslinger M. Transcription factor Pax5 activates the chromatin of key genes involved in B cell signaling, adhesion, migration, and immune function. Immunity 2007; 27:49-63. [PMID: 17658281 DOI: 10.1016/j.immuni.2007.05.019] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2007] [Revised: 05/21/2007] [Accepted: 05/24/2007] [Indexed: 01/03/2023]
Abstract
The transcription factor Pax5 represses B lineage-inappropriate genes and activates B cell-specific genes in B lymphocytes. Here we have identified 170 Pax5-activated genes. Conditional mutagenesis demonstrated that the Pax5-regulated genes require continuous Pax5 activity for normal expression in pro-B and mature B cells. Expression of half of the Pax5-activated genes is either absent or substantially reduced upon Pax5 loss in plasma cells. Direct Pax5 target genes were identified based on their protein synthesis-independent activation by a Pax5-estrogen receptor fusion protein. Chromatin immunoprecipitation (ChIP) of Pax5 together with chromatin profiling by ChIP-on-chip analysis demonstrated that Pax5 directly activates the chromatin at promoters or putative enhancers of Pax5 target genes. The Pax5-activated genes code for key regulatory and structural proteins involved in B cell signaling, adhesion, migration, antigen presentation, and germinal-center B cell formation, thus revealing a complex regulatory network that is activated by Pax5 to control B cell development and function.
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Affiliation(s)
- Alexandra Schebesta
- Research Institute of Molecular Pathology, Vienna Biocenter, Dr. Bohr-Gasse 7, A-1030 Vienna, Austria
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260
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Cobaleda C, Schebesta A, Delogu A, Busslinger M. Pax5: the guardian of B cell identity and function. Nat Immunol 2007; 8:463-70. [PMID: 17440452 DOI: 10.1038/ni1454] [Citation(s) in RCA: 463] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The transcription factor Pax5 is essential for commitment of lymphoid progenitors to the B lymphocyte lineage. Pax5 fulfils a dual role by repressing B lineage 'inappropriate' genes and simultaneously activating B lineage-specific genes. This transcriptional reprogramming restricts the broad signaling capacity of uncommitted progenitors to the B cell pathway, regulates cell adhesion and migration, induces V(H)-DJ(H) recombination, facilitates (pre-)B cell receptor signaling and promotes development to the mature B cell stage. Conditional Pax5 inactivation in early and late B lymphocytes revealed an essential role for Pax5 in controlling the identity and function of B cells throughout B lymphopoiesis. PAX5 has also been implicated in human B cell malignancies, as it is deregulated by chromosomal translocations in a subset of acute lymphoblastic leukemias and non-Hodgkin lymphomas.
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Affiliation(s)
- César Cobaleda
- Research Institute of Molecular Pathology, Vienna Biocenter, Dr. Bohr-Gasse 7, A-1030 Vienna, Austria
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261
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Xue HH, Bollenbacher-Reilley J, Wu Z, Spolski R, Jing X, Zhang YC, McCoy JP, Leonard WJ. The transcription factor GABP is a critical regulator of B lymphocyte development. Immunity 2007; 26:421-31. [PMID: 17442597 DOI: 10.1016/j.immuni.2007.03.010] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2006] [Revised: 01/09/2007] [Accepted: 03/16/2007] [Indexed: 12/19/2022]
Abstract
GA binding protein (GABP) is a ubiquitously expressed Ets-family transcription factor that critically regulates the expression of the interleukin-7 receptor alpha chain (IL-7Ralpha) in T cells, whereas it is dispensable for IL-7Ralpha expression in fetal liver B cells. Here we showed that deficiency of GABPalpha, the DNA-binding subunit of GABP, resulted in profoundly defective B cell development and a compromised humoral immune response, in addition to thymic developmental defects. Furthermore, the expression of Pax5 and Pax5 target genes such as Cd79a was greatly diminished in GABPalpha-deficient B cell progenitors, pro-B, and mature B cells. GABP could bind to the regulatory regions of Pax5 and Cd79a in vivo. Thus, GABP is a key regulator of B cell development, maturation, and function.
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Affiliation(s)
- Hai-Hui Xue
- Laboratory of Molecular Immunology, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892-1674, USA
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262
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Abstract
The expression of lineage-associated genes, as well as the survival and expansion of committed B cell progenitors, is controlled by multiple transcriptional regulators and growth-factor receptors. Whereas certain DNA-binding proteins, such as Ikaros and PU.1, are required primarily for the formation of more primitive lymphoid progenitors, other factors such as E2A and EBF1 have more direct roles in specifying the B cell-specific gene-expression program. Further, Pax5 functions to promote B cell commitment by repressing lineage-inappropriate gene expression and reinforcing B cell-specific gene expression. In this review, we focus on recent studies that have revealed that instead of a simple transcriptional hierarchy, efficient B cell commitment and differentiation requires the combinatorial activity of multiple transcription factors in a complex gene regulatory network.
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Affiliation(s)
- Stephen L Nutt
- The Walter and Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville, Victoria 3050, Australia.
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263
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Bolland DJ, Wood AL, Afshar R, Featherstone K, Oltz EM, Corcoran AE. Antisense intergenic transcription precedes Igh D-to-J recombination and is controlled by the intronic enhancer Emu. Mol Cell Biol 2007; 27:5523-33. [PMID: 17526723 PMCID: PMC1952079 DOI: 10.1128/mcb.02407-06] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
V(D)J recombination is believed to be regulated by alterations in chromatin accessibility to the recombinase machinery, but the mechanisms responsible remain unclear. We previously proposed that antisense intergenic transcription, activated throughout the mouse Igh VH region in pro-B cells, remodels chromatin for VH-to-DJH recombination. Using RNA fluorescence in situ hybridization, we now show that antisense intergenic transcription occurs throughout the Igh DHJH region before D-to-J recombination, indicating that this is a widespread process in V(D)J recombination. Transcription initiates near the Igh intronic enhancer Emu and is abrogated in mice lacking this enhancer, indicating that Emu regulates DH antisense transcription. Emu was recently demonstrated to regulate DH-to-JH recombination of the Igh locus. Together, these data suggest that Emu controls DH-to-JH recombination by activating this form of germ line Igh transcription, thus providing a long-range, processive mechanism by which Emu can regulate chromatin accessibility throughout the DH region. In contrast, Emu deletion has no effect on VH antisense intergenic transcription, which is rarely associated with DH antisense transcription, suggesting differential regulation and separate roles for these processes at sequential stages of V(D)J recombination. These results support a directive role for antisense intergenic transcription in enabling access to the recombination machinery.
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Affiliation(s)
- Daniel J Bolland
- Laboratory of Chromatin and Gene Expression, Babraham Institute, Babraham Research Campus, Cambridge CB22 3AT, United Kingdom
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264
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Buckingham M, Relaix F. The role of Pax genes in the development of tissues and organs: Pax3 and Pax7 regulate muscle progenitor cell functions. Annu Rev Cell Dev Biol 2007; 23:645-73. [PMID: 17506689 DOI: 10.1146/annurev.cellbio.23.090506.123438] [Citation(s) in RCA: 328] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Pax genes play key roles in the formation of tissues and organs during embryogenesis. Pax3 and Pax7 mark myogenic progenitor cells and regulate their behavior and their entry into the program of skeletal muscle differentiation. Recent results have underlined the importance of the Pax3/7 population of cells for skeletal muscle development and regeneration. We present our current understanding of different aspects of Pax3/7 function in myogenesis, focusing on the mouse model. This is compared with that of other Pax proteins in the emergence of tissue specific lineages and their differentiation as well as in cell survival, proliferation, and migration. Finally, we consider the molecular mechanisms that underlie the function of Pax transcription factors, including the cofactors and regulatory networks with which they interact.
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Affiliation(s)
- Margaret Buckingham
- Department of Developmental Biology, CNRS URA 2578, Pasteur Institute, 75015 Paris, France.
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265
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Affiliation(s)
- Kathryn Calame
- Department of Microbiology, Columbia University Medical Center, New York, New York 10032, USA.
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266
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Abstract
DNA segments that are separated from the promoter region of a gene by many thousands of bases may nonetheless regulate the transcriptional activity of that gene. This finding has led to the investigation of mechanisms underlying long-range chromatin interactions. In intermitotic cells, chromosomes decondense, filling the nucleus with distinct chromosome territories that interdigitate and intercalate with neighboring and even more distant chromosome territories. Both intrachromosomal and interchromosomal long-range associations have been demonstrated, and DNA binding proteins have been implicated in the maintenance of these interactions. A single gene may have interactions with many distant DNA segments. Genes that are monoallelically expressed, such as imprinted genes and odorant receptors, are frequently found to be regulated by these long-range interactions. These findings emphasize the importance of studying the geography and architecture of the nucleus as an important factor in the regulation of gene transcription.
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267
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Fuxa M, Skok JA. Transcriptional regulation in early B cell development. Curr Opin Immunol 2007; 19:129-36. [PMID: 17292598 DOI: 10.1016/j.coi.2007.02.002] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2006] [Accepted: 02/01/2007] [Indexed: 01/08/2023]
Abstract
Transcription factors and signalling molecules are important for both lineage commitment and lineage-specific regulation. The B cell specification factor Pax5 plays a dual role in B lineage commitment. Simultaneously, it potentiates and limits lineage choice by activating genes that are required for the B cell program while repressing lineage-inappropriate genes; more than 100 of the latter have now been identified. In this context, repression of the tyrosine kinase Flt3 has been shown to be essential for B lineage commitment. Regulation of antigen receptor recombination constitutes another level at which lineage specificity is determined, and the identification of two factors, E47 and FOXP1, which regulate the activity of the recombinase enzymes in B lineage cells, provides insight into the mechanisms that determine this. New information regarding the control of ordered recombination and allelic exclusion comes from studies of cis-acting elements within the Ig loci.
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Affiliation(s)
- Martin Fuxa
- The Department of Immunology and Molecular Pathology, Division of Infection and Immunity, University College London, London W1T 4JF, United Kingdom
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268
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Espinoza CR, Feeney AJ. Chromatin accessibility and epigenetic modifications differ between frequently and infrequently rearranging VH genes. Mol Immunol 2007; 44:2675-85. [PMID: 17218014 PMCID: PMC2570232 DOI: 10.1016/j.molimm.2006.12.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2006] [Revised: 11/16/2006] [Accepted: 12/06/2006] [Indexed: 11/30/2022]
Abstract
The molecular mechanisms that control the temporal and lineage-specific accessibility, as well as the rearrangement frequency of V(H) genes for V(H)-to-DJ(H) recombination, are not fully understood. We previously found a positive correlation between the extent of histone acetylation and the differential rearrangement frequency of individual V(H) genes. Here, we demonstrated that poorly rearranging V(H) genes are more highly associated with histone H3 dimethylated at lysine 9, a marker of repressive chromatin, than frequently rearranging V(H) genes. We also observed a positive relationship between the differential binding of Pax5 to individual V(H)S107 genes and rearrangement frequency. Furthermore, we showed that accessibility of the regions flanking the Pax5 binding site and the recombination signal sequence (RSS) to restriction enzyme cleavage correspond with the differential rearrangement frequency of the V(H)S107 family members. In addition, we found that the CpG sites located in the coding regions of V(H) genes are methylated in general, while the extent of DNA methylation drops dramatically near the RSS. For the V(H)S107 family, one CpG site located 101bp upstream of the RSS showed variable methylation that correlates with rearrangement frequency, and the methylation status of a CpG site located 34bp downstream of the RSS could also favor the rearrangement of V1 over V11. These findings suggest that the extent of histone modifications, chromatin accessibility, DNA methylation, as well as the differential binding of Pax5 to V(H) coding regions, could all influence the rearrangement frequency of individual V(H) genes, although some of these mechanisms are not strictly B cell specific.
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Affiliation(s)
- Celia R Espinoza
- The Scripps Research Institute, Department of Immunology IMM-22, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA
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269
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Skok JA, Gisler R, Novatchkova M, Farmer D, de Laat W, Busslinger M. Reversible contraction by looping of the Tcra and Tcrb loci in rearranging thymocytes. Nat Immunol 2007; 8:378-87. [PMID: 17334367 DOI: 10.1038/ni1448] [Citation(s) in RCA: 119] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2006] [Accepted: 02/05/2007] [Indexed: 02/06/2023]
Abstract
Reversible contraction of immunoglobulin loci juxtaposes the variable (V) genes next to the (diversity)-joining-constant ((D)JC) gene domain, thus facilitating V-(D)J recombination. Here we show that the T cell receptor beta (Tcrb) and T cell receptor alphadelta (Tcra-Tcrd) loci also underwent long-range interactions by looping in double-negative and double-positive thymocytes, respectively. Contraction of the Tcrb and Tcra loci occurred in rearranging thymocytes and was reversed at the next developmental stage. Decontraction of the Tcrb locus probably prevented further V(beta)-DJ(beta) rearrangements in double-positive thymocytes by separating the V(beta) genes from the DJC(beta) domain. In most double-negative cells, one Tcrb allele was recruited to pericentromeric heterochromatin. Such allelic positioning may facilitate asynchronous V(beta)-DJ(beta) recombination. Hence, pericentromeric recruitment and locus 'decontraction' seem to contribute to the initiation and maintenance of allelic exclusion at the Tcrb locus.
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Affiliation(s)
- Jane A Skok
- Department of Immunology and Molecular Pathology, Division of Infection and Immunity, University College London, London W1T 4JF, UK
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270
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Hodawadekar S, Wei F, Yu D, Thomas-Tikhonenko A, Atchison ML. Epigenetic histone modifications do not control Igkappa locus contraction and intranuclear localization in cells with dual B cell-macrophage potential. THE JOURNAL OF IMMUNOLOGY 2006; 177:6165-71. [PMID: 17056545 PMCID: PMC1635549 DOI: 10.4049/jimmunol.177.9.6165] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Somatic rearrangement of the Ig genes during B cell development is believed to be controlled, at least in part, by accessibility of the loci to the recombinational machinery. Accessibility is poorly understood, but appears to be controlled by a combination of histone posttranslational modifications, large scale Ig locus contractions, and changes in intranuclear localization of the loci. These changes are regulated by developmental stage-specific as well as tissue-specific mechanisms. We previously isolated a murine B cell lymphoma line, Myc5, that can oscillate between the B cell and macrophage lineages depending upon growth conditions. This line provides an opportunity to study tissue-specific regulation of epigenetic mechanisms operating on the Ig loci. We found that when Myc5 cells are induced to differentiate from B cells into macrophages, expression of macrophage-specific transcripts was induced (M-CSFR, F4/80, and CD14), whereas B cell-specific transcripts decreased dramatically (mb-1, E47, IRF4, Pax5, and Igkappa). Loss of Igkappa transcription was associated with reduced Igkappa locus contraction, as well as increased association with heterochromatin protein-1 and association of the Igkappa locus with the nuclear periphery. Surprisingly, however, we found that histone modifications at the Igkappa locus remained largely unchanged whether the cells were grown in vivo as B cells, or in vitro as macrophages. These results mechanistically uncouple histone modifications at the Igkappa locus from changes in locus contraction and intranuclear localization.
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Affiliation(s)
| | - Fang Wei
- Department of Animal Biology and
| | - Duonan Yu
- Department of Pathobiology, School of Veterinary
Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Andrei Thomas-Tikhonenko
- Department of Pathobiology, School of Veterinary
Medicine, University of Pennsylvania, Philadelphia, PA 19104
| | - Michael L. Atchison
- Department of Animal Biology and
- Address correspondence and reprint requests to Dr.
Michael L. Atchison, School of Veterinary Medicine, University of Pennsylvania,
3800 Spruce Street, Philadelphia, PA 19104. E-mail address:
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271
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Roessler S, Györy I, Imhof S, Spivakov M, Williams RR, Busslinger M, Fisher AG, Grosschedl R. Distinct promoters mediate the regulation of Ebf1 gene expression by interleukin-7 and Pax5. Mol Cell Biol 2006; 27:579-94. [PMID: 17101802 PMCID: PMC1800812 DOI: 10.1128/mcb.01192-06] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Early differentiation of B lymphocytes requires the function of multiple transcription factors that regulate the specification and commitment of the lineage. Loss- and gain-of-function experiments have provided important insight into the transcriptional control of B lymphopoiesis, whereby E2A was suggested to act upstream of EBF1 and Pax5 downstream of EBF1. However, this simple hierarchy cannot account for all observations, and our understanding of a presumed regulatory network, in which transcription factors and signaling pathways operate, is limited. Here, we show that the expression of the Ebf1 gene involves two promoters that are differentially regulated and generate distinct protein isoforms. We find that interleukin-7 signaling, E2A, and EBF1 activate the distal Ebf1 promoter, whereas Pax5, together with Ets1 and Pu.1, regulates the stronger proximal promoter. In the absence of Pax5, the function of the proximal Ebf1 promoter and accumulation of EBF1 protein are impaired and the replication timing and subcellular localization of the Ebf1 locus are altered. Taken together, these data suggest that the regulation of Ebf1 via distinct promoters allows for the generation of several feedback loops and the coordination of multiple determinants of B lymphopoiesis in a regulatory network.
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Affiliation(s)
- Stephanie Roessler
- Max Planck Institute of Immunobiology, Department of Cellular and Molecular Immunology, 79108 Freiburg, Germany
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272
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Hodawadekar S, Yu D, Cozma D, Freedman B, Sunyer O, Atchison ML, Thomas-Tikhonenko A. B-Lymphoma cells with epigenetic silencing of Pax5 trans-differentiate into macrophages, but not other hematopoietic lineages. Exp Cell Res 2006; 313:331-40. [PMID: 17098231 PMCID: PMC1839943 DOI: 10.1016/j.yexcr.2006.10.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Revised: 10/07/2006] [Accepted: 10/16/2006] [Indexed: 01/08/2023]
Abstract
In mice, zygotic or pro-B-cell-specific knock-out of the Pax5 gene allows differentiation of pro-B-cells into all hematopoietic lineages. We previously generated and characterized a murine B-cell lymphoma, dubbed Myc5, whose cells spontaneously lose Pax5 expression when cultured in vitro, but regain it when re-injected into syngeneic mice. In cultured Myc5 cells, the loss of Pax5 correlates with the acquisition of myeloid markers, such as CD11b and F4/80. Here, we sought to determine whether these cells are truly B-macrophage-restricted or, like Pax5-null progenitors, can give rise to additional hematopoietic lineages. In vitro differentiation assays with various cytokines showed that Myc5 cells do not differentiate into NK cells, dendritic cells, neutrophils, or osteoclasts. At the same time, in the presence of macrophage colony-stimulating factor (M-CSF), they readily phagocytose latex beads and provide T-cell help. Both phenomena are indicative of the bona fide macrophage phenotype. Conversely, enforced Pax5 re-expression in macrophage-like Myc5 cells led to down-regulation of the M-CSF receptor and re-acquisition of some B-cell surface markers (e.g., CD79a) and lineage-specific transcription factors (e.g., IRF4 and Blimp). Retrovirally encoded Pax5 also restored expression of several master B-cell differentiation proteins, such as the IL-7 receptor and transcription factor E2A. In contrast, levels of EBF were unaffected by Pax5 suggesting that EBF acts exclusively upstream of Pax5 and might contribute to Pax5 expression. Indeed, transduction with an EBF-encoding retrovirus partly reactivated endogenous Pax5. Our data reveal the complex relationship between B-cell-specific transcription factors and suggest the existence of numerous feedback mechanisms.
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Affiliation(s)
- Suchita Hodawadekar
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104-6051
| | - Duonan Yu
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104-6051
| | - Diana Cozma
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104-6051
| | - Bruce Freedman
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104-6051
| | - Oriol Sunyer
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104-6051
| | - Michael L. Atchison
- Department of Animal Biology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104-6051
| | - Andrei Thomas-Tikhonenko
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, 3800 Spruce Street, Philadelphia, PA 19104-6051
- * Corresponding Author: , Tel: (215) 573-5138, Fax: (215) 746-0380
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273
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Fraenkel S, Bergman Y. Variability and Exclusion in Host and Parasite: Epigenetic Regulation of Ig and var Expression. THE JOURNAL OF IMMUNOLOGY 2006; 177:5767-74. [PMID: 17056499 DOI: 10.4049/jimmunol.177.9.5767] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The immune system generates highly diverse AgRs of different specificities from a pool of designated genomic loci, each containing large arrays of genes. Ultimately, each B or T cell expresses a receptor of a single type on its surface. Immune evasion by the malaria parasite Plasmodium falciparum is mediated by the mutually exclusive expression of a single member of the var family of genes, which encodes variant surface Ags. In this review, we discuss the similarities as well as the unique characteristics of the epigenetic mechanisms involved in the establishment of mutually exclusive expression in the immune and parasite systems.
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Affiliation(s)
- Shira Fraenkel
- Department of Experimental Medicine and Cancer Research, Hebrew University-Hadassah Medical School, Jerusalem 91120, Israel
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274
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Abstract
Paired box protein 5 (Pax5) is essential for early B cell commitment as well as for B cell development, and continuous expression of Pax5 is required throughout the B cell lineage to maintain the functional identity of B cells. During B cell activation, Pax5 is downregulated before terminal differentiation into antibody-secreting plasma cells, and enforced expression of Pax5 prevents plasmacytic development. Recently, loss of Pax5 was shown to result in the substantial transition to a plasma cell state, demonstrating a functionally significant role for Pax5 in the regulation of terminal B cell differentiation. Here we elucidate the current understanding about the function of Pax5 as a key inhibitor of plasma cell differentiation.
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Affiliation(s)
- K-P Nera
- Turku Graduate School of Biomedical Sciences, Department of Medical Microbiology, University of Turku, Kiinamyllynkatu 13, 20500 Turku, Finland.
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275
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Souabni A, Jochum W, Busslinger M. Oncogenic role of Pax5 in the T-lymphoid lineage upon ectopic expression from the immunoglobulin heavy-chain locus. Blood 2006; 109:281-9. [PMID: 16968900 DOI: 10.1182/blood-2006-03-009670] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Abstract
Four of 9 PAX transcription factor genes have been associated with chromosomal translocations in human tumors, although their oncogenic potential has not yet been demonstrated in transgenic mouse models. The B-lymphoidPAX5 gene participates in the generation of the t(9;14)(p13;q32) translocation in germinal center B cells, which leads to deregulated PAX5 expression under the control of the immunoglobulin heavy-chain (IgH) locus in a subset of B-cell non-Hodgkin lymphomas. Here we reconstructed a human t(9;14) translocation in a knock-in mouse by inserting a PAX5 minigene into the IgH locus. The IgHP5ki allele, which corresponds to a germline rather than somatic mutation, is activated in multipotent hematopoietic progenitors and is subsequently expressed in dendritic cells (DCs) and in natural killer (NK), T, and B cells. Ectopic Pax5 expression interferes with normal T-cell development and causes immature T-lymphoblastic lymphomas in IgHP5ki/+ and IgHP5ki/P5ki mice. Aggressive T-cell lymphomas develop even faster in IkPax5/+ mice expressing Pax5 from the Ikaros locus. Pax5 expression in thymocytes activates B-cell–specific genes and represses T-lymphoid genes, suggesting that Pax5 contributes to lymphomagenesis by deregulating the T-cell gene-expression program. These data identify Pax5 as a potent oncogene and demonstrate that the T-lymphoid lineage is particularly sensitive to the oncogenic action of Pax5.
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MESH Headings
- Alleles
- Animals
- B-Lymphocytes/metabolism
- B-Lymphocytes/pathology
- Bone Marrow Transplantation
- Cell Differentiation/genetics
- Cell Lineage
- Cell Transformation, Neoplastic/genetics
- Chromosomes, Human, Pair 14/genetics
- Chromosomes, Human, Pair 14/ultrastructure
- Chromosomes, Human, Pair 9/genetics
- Chromosomes, Human, Pair 9/ultrastructure
- Dendritic Cells/metabolism
- Dendritic Cells/pathology
- Embryonal Carcinoma Stem Cells
- Gene Expression Regulation, Neoplastic
- Humans
- Ikaros Transcription Factor/genetics
- Immunoglobulin Heavy Chains/genetics
- Killer Cells, Natural/metabolism
- Killer Cells, Natural/pathology
- Lymphocytes/metabolism
- Lymphocytes/pathology
- Lymphoma, B-Cell/genetics
- Lymphoma, B-Cell/pathology
- Mice
- Mice, Inbred C57BL
- Mutagenesis, Insertional
- Neoplasm Transplantation
- Neoplastic Stem Cells/metabolism
- Neoplastic Stem Cells/pathology
- PAX5 Transcription Factor/genetics
- PAX5 Transcription Factor/physiology
- Precursor Cell Lymphoblastic Leukemia-Lymphoma/genetics
- Precursor Cell Lymphoblastic Leukemia-Lymphoma/pathology
- Promoter Regions, Genetic
- Radiation Chimera
- T-Lymphocytes/metabolism
- T-Lymphocytes/pathology
- Translocation, Genetic
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Affiliation(s)
- Abdallah Souabni
- Research Institute of Molecular Pathology, Vienna Biocenter, Dr Bohr-Gasse 7, A-1030 Vienna, Austria
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276
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Fraser P. Transcriptional control thrown for a loop. Curr Opin Genet Dev 2006; 16:490-5. [PMID: 16904310 DOI: 10.1016/j.gde.2006.08.002] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2006] [Accepted: 08/01/2006] [Indexed: 11/21/2022]
Abstract
The relationships among in vivo chromatin structures, chromosome organization and genome function must be understood in order to reveal the hidden regulatory information in our genomes. Rather than being stable architectural features, it appears that chromatin and chromosome conformations at all levels are highly dynamic, which is the key to their function. Studies in recent years have elucidated long-range interactions or folded chromatin conformations that play significant roles in gene regulation. Most recently, intrachromosomal associations and co-associations with shared nuclear transcription compartments have been discovered in mammals, with the potential to greatly expand our view of how the genome is regulated.
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Affiliation(s)
- Peter Fraser
- Laboratory of Chromatin and Gene Expression, The Babraham Institute, Babraham Research Campus, Cambridge, CB2 4AT, UK.
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277
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Pawlitzky I, Angeles CV, Siegel AM, Stanton ML, Riblet R, Brodeur PH. Identification of a candidate regulatory element within the 5' flanking region of the mouse Igh locus defined by pro-B cell-specific hypersensitivity associated with binding of PU.1, Pax5, and E2A. THE JOURNAL OF IMMUNOLOGY 2006; 176:6839-51. [PMID: 16709844 DOI: 10.4049/jimmunol.176.11.6839] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The Igh locus is controlled by cis-acting elements, including Emu and the 3' IgH regulatory region which flank the C region genes within the well-studied 3' part of the locus. Although the presence of additional control elements has been postulated to regulate rearrangements of the VH gene array that extends to the 5' end of the locus, the 5' border of Igh and its flanking region have not been characterized. To facilitate the analysis of this unexplored region and to identify potential novel control elements, we physically mapped the most D-distal VH segments and scanned 46 kb of the immediate 5' flanking region for DNase I hypersensitive sites. Our studies revealed a cluster of hypersensitive sites 30 kb upstream of the most 5' VH gene. Detection of one site, HS1, is restricted to pro-B cell lines and HS1 is accessible to restriction enzyme digestion exclusively in normal pro-B cells, the stage defined by actively rearranging Igh-V loci. Sequence motifs within HS1 for PU.1, Pax5, and E2A bind these proteins in vitro and these factors are recruited to HS1 sequence only in pro-B cells. Transient transfection assays indicate that the Pax5 binding site is required for the repression of transcriptional activity of HS1-containing constructs. Thus, our characterization of the region 5' of the VH gene cluster demonstrated the presence of a single cluster of DNase I hypersensitive sites within the 5' flanking region, and identified a candidate Igh regulatory region defined by pro-B cell-specific hypersensitivity and interaction with factors implicated in regulating VDJ recombination.
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Affiliation(s)
- Inka Pawlitzky
- Immunology Program, Sackler School of Graduate Biomedical Sciences, Tufts University School of Medicine, Boston, MA 02111, USA
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278
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Jackson AM, Krangel MS. A role for MAPK in feedback inhibition of Tcrb recombination. THE JOURNAL OF IMMUNOLOGY 2006; 176:6824-30. [PMID: 16709842 DOI: 10.4049/jimmunol.176.11.6824] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The Tcrb locus is subject to a host of regulatory mechanisms that impart a strict cell and developmental stage-specific order to variable (V), diversity (D), and joining (J) gene segment recombination. The Tcrb locus is also regulated by allelic exclusion mechanisms, which restrict functional rearrangements to a single allele. The production of a functional rearrangement in CD4-CD8- double-negative (DN) thymocytes leads to the assembly of a pre-TCR and initiates signaling cascades that allow for DN to CD4+CD8+ double-positive (DP) differentiation, proliferation, and feedback inhibition of further Vbeta to DJbeta rearrangement. Feedback inhibition is believed to be controlled, in part, by the loss of Vbeta gene segment accessibility during the DN to DP transition. However, the pre-TCR signaling pathways that lead to the inactivation of Vbeta chromatin have not been determined. Because activation of the MAPK pathway is documented to promote DP differentiation in the absence of allelic exclusion, we characterized the properties of Vbeta chromatin within DP thymocytes generated by a constitutively active Raf1 (Raf-CAAX) transgene. Consistent with previous reports, we show that the Raf-CAAX transgene does not inhibit Tcrb recombination in DN thymocytes. Nevertheless, DP thymocytes generated by Raf-CAAX signals display normal down-regulation of Vbeta segment accessibility and normal feedback inhibition of the Vbeta to DJbeta rearrangement. Therefore, our results emphasize the distinct requirements for feedback inhibition in the DN and DP compartments. Although MAPK activation cannot impose feedback in DN thymocytes, it contributes to feedback inhibition through developmental changes that are tightly linked to DN to DP differentiation.
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MESH Headings
- Adaptor Proteins, Signal Transducing/deficiency
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/physiology
- Alleles
- Animals
- Chromatin/chemistry
- Chromatin/genetics
- Down-Regulation/genetics
- Down-Regulation/immunology
- Feedback, Physiological/genetics
- Feedback, Physiological/immunology
- Gene Rearrangement, beta-Chain T-Cell Antigen Receptor
- Humans
- Membrane Proteins/deficiency
- Membrane Proteins/genetics
- Membrane Proteins/physiology
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Mice, Transgenic
- Phosphoproteins/deficiency
- Phosphoproteins/genetics
- Phosphoproteins/physiology
- Protein Prenylation
- Proto-Oncogene Proteins c-raf/genetics
- Proto-Oncogene Proteins c-raf/physiology
- Receptors, Antigen, T-Cell, alpha-beta/antagonists & inhibitors
- Receptors, Antigen, T-Cell, alpha-beta/biosynthesis
- Receptors, Antigen, T-Cell, alpha-beta/genetics
- Signal Transduction/genetics
- Signal Transduction/immunology
- T-Lymphocyte Subsets/cytology
- T-Lymphocyte Subsets/immunology
- T-Lymphocyte Subsets/metabolism
- Thymus Gland/cytology
- Thymus Gland/immunology
- Thymus Gland/metabolism
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Affiliation(s)
- Annette M Jackson
- Department of Immunology, Duke University Medical Center, Durham NC 27710, USA
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279
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Hu H, Wang B, Borde M, Nardone J, Maika S, Allred L, Tucker PW, Rao A. Foxp1 is an essential transcriptional regulator of B cell development. Nat Immunol 2006; 7:819-26. [PMID: 16819554 DOI: 10.1038/ni1358] [Citation(s) in RCA: 249] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2006] [Accepted: 05/24/2006] [Indexed: 01/08/2023]
Abstract
Forkhead transcription factors are key participants in development and immune regulation. Here we demonstrate that absence of the gene encoding the forkhead transcription factor Foxp1 resulted in a profound defect in early B cell development. Foxp1 deficiency was associated with decreased expression of all B lineage genes in B220+ fetal liver cells as well as with a block in the transition from pro-B cell to pre-B cell involving diminished expression of recombination-activating genes 1 and 2. Foxp1 bound to the Erag enhancer and was involved in controlling variable-(diversity)-joining recombination of the gene encoding immunoglobulin heavy chain in a B cell lineage-specific way. Our results identify Foxp1 as an essential participant in the transcriptional regulatory network of B lymphopoiesis.
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Affiliation(s)
- Hui Hu
- Department of Pathology, Harvard Medical School, CBR Institute for Biomedical Research, Boston, Massachusetts 02115, USA.
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280
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Jung D, Giallourakis C, Mostoslavsky R, Alt FW. Mechanism and control of V(D)J recombination at the immunoglobulin heavy chain locus. Annu Rev Immunol 2006; 24:541-70. [PMID: 16551259 DOI: 10.1146/annurev.immunol.23.021704.115830] [Citation(s) in RCA: 435] [Impact Index Per Article: 24.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
V(D)J recombination assembles antigen receptor variable region genes from component germline variable (V), diversity (D), and joining (J) gene segments. For B cells, such rearrangements lead to the production of immunoglobulin (Ig) proteins composed of heavy and light chains. V(D)J is tightly controlled at the Ig heavy chain locus (IgH) at several different levels, including cell-type specificity, intra- and interlocus ordering, and allelic exclusion. Such controls are mediated at the level of gene segment accessibility to V(D)J recombinase activity. Although much has been learned, many long-standing questions regarding the regulation of IgH locus rearrangements remain to be elucidated. In this review, we summarize advances that have been made in understanding how V(D)J recombination at the IgH locus is controlled and discuss important areas for future investigation.
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Affiliation(s)
- David Jung
- Howard Hughes Medical Institute, Children's Hospital, CBR Institute for Biomedical Research, and Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115, USA.
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281
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Inlay MA, Lin T, Gao HH, Xu Y. Critical roles of the immunoglobulin intronic enhancers in maintaining the sequential rearrangement of IgH and Igk loci. ACTA ACUST UNITED AC 2006; 203:1721-32. [PMID: 16785310 PMCID: PMC2118354 DOI: 10.1084/jem.20052310] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
V(D)J recombination of immunoglobulin (Ig) heavy (IgH) and light chain genes occurs sequentially in the pro– and pre–B cells. To identify cis-elements that dictate this order of rearrangement, we replaced the endogenous matrix attachment region/Igk intronic enhancer (MiEκ) with its heavy chain counterpart (Eμ) in mice. This replacement, denoted EμR, substantially increases the accessibility of both Vκ and Jκ loci to V(D)J recombinase in pro–B cells and induces Igk rearrangement in these cells. However, EμR does not support Igk rearrangement in pre–B cells. Similar to that in MiEκ−/− pre–B cells, the accessibility of Vκ segments to V(D)J recombinase is considerably reduced in EμR pre–B cells when compared with wild-type pre–B cells. Therefore, Eμ and MiEκ play developmental stage-specific roles in maintaining the sequential rearrangement of IgH and Igk loci by promoting the accessibility of V, D, and J loci to the V(D)J recombinase.
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Affiliation(s)
- Matthew A Inlay
- Section of Molecular Biology, Division of Biological Sciences, University of California, San Diego, La Jolla, CA 92093, USA
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282
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Sen R, Oltz E. Genetic and epigenetic regulation of IgH gene assembly. Curr Opin Immunol 2006; 18:237-42. [PMID: 16616470 DOI: 10.1016/j.coi.2006.03.008] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2006] [Accepted: 03/27/2006] [Indexed: 12/19/2022]
Abstract
Precursor B cells assemble a diverse repertoire of immunoglobulin (Ig) genes by the process of V(D)J recombination. Assembly of IgH genes is regulated in a tissue- and stage-specific manner via the activation and then the inactivation of distinct regions within the one megabase IgH locus. Recent studies have shown that regional control is achieved using a combination of genetic and epigenetic strategies, which modulate chromatin accessibility to V(D)J recombinase, relocate IgH loci within the nucleus, and promote changes in locus conformation that alter the spatial proximity of target gene segments. Orchestration of these regulatory processes is crucial for the generation of a functional B cell repertoire.
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Affiliation(s)
- Ranjan Sen
- Laboratory of Cellular and Molecular Biology, National Institute on Aging/National Institutes of Health, 5600 Nathan Shock Drive, Baltimore, MD 21224, USA
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283
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Zhang Z, Espinoza CR, Yu Z, Stephan R, He T, Williams GS, Burrows PD, Hagman J, Feeney AJ, Cooper MD. Transcription factor Pax5 (BSAP) transactivates the RAG-mediated V(H)-to-DJ(H) rearrangement of immunoglobulin genes. Nat Immunol 2006; 7:616-24. [PMID: 16680144 DOI: 10.1038/ni1339] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2005] [Accepted: 03/27/2006] [Indexed: 11/09/2022]
Abstract
Immunoglobulin rearrangement from variable heavy chain (V(H)) to diversity (D)-joining heavy chain (J(H)), which occurs exclusively in B lineage cells, is impaired in mice deficient for the B lineage-specific transcription factor Pax5. Conversely, ectopic Pax5 expression in thymocytes promotes the rearrangement of D(H)-proximal V(H)7183 genes. In exploring the mechanism for Pax5 regulation of V(H)-to-DJ(H) recombination, we have identified multiple Pax5 binding sites in the coding regions of human and mouse V(H) gene segments. Pax5 bound to those sites in vitro and occupied V(H) genes in early human and mouse B lineage cells. Moreover, Pax5 interacted with the recombination-activating gene 1 (RAG1)-RAG2 complex to enhance RAG-mediated V(H) recombination signal sequence cleavage and recombination of a V(H) gene substrate. These findings indicate a direct activating function for Pax5 in RAG-mediated immunoglobulin V(H)-to-DJ(H) recombination.
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Affiliation(s)
- Zhixin Zhang
- Division of Developmental and Clinical Immunology, University of Alabama at Birmingham, 35294, USA.
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284
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Nera KP, Kohonen P, Narvi E, Peippo A, Mustonen L, Terho P, Koskela K, Buerstedde JM, Lassila O. Loss of Pax5 promotes plasma cell differentiation. Immunity 2006; 24:283-93. [PMID: 16546097 DOI: 10.1016/j.immuni.2006.02.003] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2005] [Revised: 01/26/2006] [Accepted: 02/01/2006] [Indexed: 01/06/2023]
Abstract
Pax5 is indispensable for the commitment of early lymphoid progenitors to the B cell lineage as well as for the development of B cells. To better understand the functional importance of Pax5 at the later stages of B cell differentiation, we established a Pax5-deficient DT40 B cell line. The Pax5(-/-) cells exhibited slower growth, decreased surface IgM expression, and total loss of B cell receptor signaling. Moreover, the expression of the plasma cell-characteristic transcription factors Blimp-1 and XBP-1 were significantly upregulated and the expression of Bcl-6 diminished in the Pax5(-/-) cells, and this alteration was normalized by restored Pax5 expression. The Pax5-deficient cells further manifested substantially elevated secretion of IgM into the supernatant, another characteristic of plasma cells. These results indicate that downregulation of Pax5 function promotes the plasma cell differentiation of B cells.
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Affiliation(s)
- Kalle-Pekka Nera
- Turku Graduate School of Biomedical Sciences, University of Turku, Kiinamyllynkatu 13, 20520 Turku, Finland.
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285
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Johnston CM, Wood AL, Bolland DJ, Corcoran AE. Complete Sequence Assembly and Characterization of the C57BL/6 Mouse Ig Heavy Chain V Region. THE JOURNAL OF IMMUNOLOGY 2006; 176:4221-34. [PMID: 16547259 DOI: 10.4049/jimmunol.176.7.4221] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The mechanisms that regulate variable (V) gene selection during the development of the mouse IgH repertoire are not fully understood, due in part to the absence of the complete locus sequence. To better understand these processes, we have assembled the entire 2.5-Mb mouse IgH (Igh) V region sequence of the C57BL/6 strain from public sequences and present the first complete annotated map of the region, including V genes, pseudogenes, repeats, and nonrepetitive intergenic sequences. In so doing, we have discovered a new V gene family, VH16. We have identified clusters of conserved region-specific intergenic sequences and have verified our assembly by genic and intergenic Southern blotting. We have observed that V pseudogenes are not evenly spread throughout the V region, but rather cluster together. The largest J558 family, which spans more than half of the locus, has two strikingly different domains, which suggest points of evolutionary divergence or duplication. The 5' end contains widely spaced J558 genes interspersed with 3609 genes and is pseudogene poor. The 3' end contains closely spaced J558 genes, no 3609 genes, and is pseudogene rich. Each occupies a different branch of the phylogenetic tree. Detailed analysis of 500-bp upstream of all functional genes has revealed several conserved binding sites, general and B cell-specific, as well as key differences between families. This complete and definitive assembly of the mouse Igh V region will facilitate detailed study of promoter function and large-scale mechanisms associated with V(D)J recombination including locus contraction and antisense intergenic transcription.
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Affiliation(s)
- Colette M Johnston
- Laboratory of Chromatin and Gene Expression, Babraham Institute, Cambridge, UK
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286
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Will WM, Aaker JD, Burchill MA, Harmon IR, O'Neil JJ, Goetz CA, Hippen KL, Farrar MA. Attenuation of IL-7 Receptor Signaling Is Not Required for Allelic Exclusion. THE JOURNAL OF IMMUNOLOGY 2006; 176:3350-5. [PMID: 16517702 DOI: 10.4049/jimmunol.176.6.3350] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Allelic exclusion prevents pre-B cells from generating more than one functional H chain, thereby ensuring the formation of a unique pre-BCR. The signaling processes underlying allelic exclusion are not clearly understood. IL-7R-dependent signals have been clearly shown to regulate the accessibility of the Ig H chain locus. More recent work has suggested that pre-BCR-dependent attenuation of IL-7R signaling returns the H chain loci to an inaccessible state; this process has been proposed to underlie allelic exclusion. Importantly, this model predicts that preventing pre-BCR-dependent down-regulation of IL-7R signaling should interfere with allelic exclusion. To test this hypothesis, we made use of transgenic mice that express a constitutively active form of STAT5b (STAT5b-CA). STAT5b-CA expression restores V(D)J recombination in IL-7R(-/-) B cells, demonstrating that IL-7 regulates H chain locus accessibility and V(D)J recombination via STAT5 activation. To examine the effects of constitutively active STAT5b on allelic exclusion, we crossed STAT5b-CA mice (which express the IgM(b) allotype) to IgM(a) allotype congenic mice. We found no difference in the percentage of IgM(a)/IgM(b)-coexpressing B cells in STAT5b-CA vs littermate control mice; identical results were observed when crossing STAT5b-CA mice with hen egg lysozyme (HEL) H chain transgenic mice. The HEL transgene enforces allelic exclusion, preventing rearrangement of endogenous H chain genes; importantly, rearrangement of endogenous H chain genes was suppressed to a similar degree in STAT5b-CA vs HEL mice. Thus, attenuation of IL-7R/STAT5 signaling is not required for allelic exclusion.
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Affiliation(s)
- Wynette M Will
- Department of Laboratory Medicine and Pathology, The Cancer Center, University of Minnesota, Minneapolis, MN 55455, USA
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287
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Tagoh H, Ingram R, Wilson N, Salvagiotto G, Warren AJ, Clarke D, Busslinger M, Bonifer C. The mechanism of repression of the myeloid-specific c-fms gene by Pax5 during B lineage restriction. EMBO J 2006; 25:1070-80. [PMID: 16482219 PMCID: PMC1409732 DOI: 10.1038/sj.emboj.7600997] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2005] [Accepted: 01/19/2006] [Indexed: 11/09/2022] Open
Abstract
The transcription factor Pax5 (BSAP) is required for the expression of a B-cell-specific genetic program and for B-cell differentiation, and also to suppress genes of alternative lineages. The molecular mechanism by which repression of myeloid genes occurs during early B-lineage restriction is unknown and in this study we addressed this question. One of the genes repressed by Pax5 in B cells is the colony-stimulating factor receptor 1 gene (csf1r or c-fms). We examined the changes in chromatin caused by Pax5 activity, and we show that Pax5 is directly recruited to c-fms resulting in the rapid loss of RNA polymerase II binding, followed by loss of transcription factor binding and DNaseI hypersensitivity at all cis-regulatory elements. We also show that Pax5 targets the basal transcription machinery of c-fms by interacting with a binding site within the major transcription start sites. Our results support a model by which Pax5 does not lead to major alterations in chromatin modification, but inhibits transcription by interfering with the action of myeloid transcription factors.
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Affiliation(s)
- Hiromi Tagoh
- Division of Experimental Haematology, LIMM, University of Leeds, St James's University Hospital, Leeds, UK
| | - Richard Ingram
- Division of Experimental Haematology, LIMM, University of Leeds, St James's University Hospital, Leeds, UK
| | - Nicola Wilson
- Division of Experimental Haematology, LIMM, University of Leeds, St James's University Hospital, Leeds, UK
| | - Giorgia Salvagiotto
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna, Austria
| | - Alan J Warren
- MRC Laboratory of Molecular Biology, Cambridge, UK
- Department of Haematology, University of Cambridge, Cambridge, UK
| | - Deborah Clarke
- Division of Experimental Haematology, LIMM, University of Leeds, St James's University Hospital, Leeds, UK
| | - Meinrad Busslinger
- Research Institute of Molecular Pathology, Vienna Biocenter, Vienna, Austria
| | - Constanze Bonifer
- Division of Experimental Haematology, LIMM, University of Leeds, St James's University Hospital, Leeds, UK
- Leeds Institute of Molecular Medicine, The JIF Building, St James University Hospital, University of Leeds, Leeds LS9 7TF, UK. Tel.: +44 113 343 8525; Fax: +44 113 343 8702; E-mail:
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288
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Spicuglia S, Franchini DM, Ferrier P. Regulation of V(D)J recombination. Curr Opin Immunol 2006; 18:158-63. [PMID: 16459067 DOI: 10.1016/j.coi.2006.01.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2005] [Accepted: 01/24/2006] [Indexed: 12/15/2022]
Abstract
Adaptive immunity is intimately linked to the expression of antigen-specific immunoglobulin and T cell receptor genes and their recombination assembly from germline V, D and J gene segments. This developmentally regulated process relies on the activity of the Rag1-Rag2 recombinase, on accessibility of target gene segments and on monoallelic gene activation. Recent studies have revealed new mechanisms that, along with recombinase activity and locus accessibility, are likely to contribute to the control of V(D)J recombination, including target-site bias by the recombinase, RNA processing and chromosome positioning.
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Affiliation(s)
- Salvatore Spicuglia
- Centre d'Immunologie de Marseille-Luminy (CIML), Institut National de la Santé et de la Recherche Médicale (INSERM), 13288 Marseille Cedex 9, France
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289
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Abstract
Successful V(D)J recombination at the T-cell receptor beta (Tcrb) locus is critical for early thymocyte development. The locus is subject to a host of regulatory mechanisms that impart a strict developmental order to Tcrb recombination events and that insure that Tcrb recombination occurs in an allelically excluded fashion. Progress has been made in the understanding of the cis-acting control of Tcrb locus chromatin structure and the extent to which such accessibility control can account for the developmental regulation of Tcrb recombination. However, recent studies in our laboratory and elsewhere have made it abundantly clear that accessibility control is only part of the story, and multiple additional mechanisms impact both the developmental activation and inactivation of locus recombination events. Here we evaluate our current understanding of developmental regulation at the Tcrb locus. We highlight the many unresolved issues and we discuss how recent concepts emerging from studies of other antigen receptor loci may (or may not) help to resolve these issues.
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Affiliation(s)
- Annette M Jackson
- Department of Immunology, Duke University Medical Center, Durham, NC 27710, USA
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290
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Roessler S, Grosschedl R. Role of transcription factors in commitment and differentiation of early B lymphoid cells. Semin Immunol 2006; 18:12-9. [PMID: 16431127 DOI: 10.1016/j.smim.2005.12.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
B lymphopoiesis is a differentiation process in which hematopoietic stem cells are converted into antibody-producing plasma cells. B cell differentiation involves multiple steps, including cell specification, commitment to the B cell lineage, immunoglobulin rearrangements, maturation of B cells and terminal differentiation into plasma cells. Each of these steps is controlled by signaling pathways and transcription factors that act in synergy, feedback-loops or cross-antagonism to generate complex regulatory networks that allow for plasticity and stability of B cell differentiation.
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Affiliation(s)
- Stephanie Roessler
- Max-Planck Institute of Immunobiology, Department of Cellular and Molecular Immunology, Stubeweg 51, 79108 Freiburg, Germany
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291
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Ye M, Ermakova O, Graf T. PU.1 is not strictly required for B cell development and its absence induces a B-2 to B-1 cell switch. ACTA ACUST UNITED AC 2006; 202:1411-22. [PMID: 16301746 PMCID: PMC2212978 DOI: 10.1084/jem.20051089] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
In this paper, we describe the unexpected outgrowth of B lineage cells from PU.1(-/-) fetal liver cultures. The cells express all early B cell genes tested, including the putative PU.1 target genes IL-7R and EBF but not B220, and can produce immunoglobulin M. However, we observed a delay in the PU.1(-/-) B cell outgrowth and reduced precursor frequencies, indicating that although PU.1 is not strictly required for B cell commitment, it facilitates B cell development. We also ablated PU.1 in CD19-expressing B lineage cells in vivo, using a Cre-lox approach that allows them to be tracked. PU.1 excision resulted in a shift from B-2 cells to B-1-like cells, which dramatically increased with the age of the mice. Our data indicate that this shift is predominantly caused by a B-2 to B-1 cell reprogramming. Furthermore, we found that B-2 cells express substantially more PU.1 than B-1 cells, which is consistent with the idea that maintenance of the B-2 cell phenotype requires relatively high levels of PU.1, but B-1 cells require little.
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Affiliation(s)
- Min Ye
- Department of Developmental and Molecular Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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292
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Abstract
Progenitor B lymphocytes that successfully assemble a heavy chain gene encoding an immunoglobulin capable of pairing with surrogate light chain proteins trigger their own further differentiation by signaling via the pre-BCR complex. The pre-BCR signals several rounds of proliferation and, in this expanded population, directs a complex, B cell-specific set of epigenetic changes resulting in allelic exclusion of the heavy chain locus and activation of the light chain loci for V(D)J recombination.
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Affiliation(s)
- Jamie K Geier
- UC-Berkeley, Department of Molecular & Cell Biology, Division of Immunology, 439 Life Sciences Addition, Berkeley, CA 94720-3200, USA
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293
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Hsu CL, King-Fleischman AG, Lai AY, Matsumoto Y, Weissman IL, Kondo M. Antagonistic effect of CCAAT enhancer-binding protein-alpha and Pax5 in myeloid or lymphoid lineage choice in common lymphoid progenitors. Proc Natl Acad Sci U S A 2006; 103:672-7. [PMID: 16407117 PMCID: PMC1334685 DOI: 10.1073/pnas.0510304103] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Lymphoid lineage-committed progenitors, such as common lymphoid progenitors (CLPs), maintain a latent myeloid differentiation potential, which can be initiated by stimulation through exogenously expressed cytokine receptors, including IL-2 receptors. Here we show that the transcription factor CCAAT enhancer-binding protein-alpha (C/EBPalpha) is promptly up-regulated in CLPs upon ectopic IL-2 stimulation. Enforced C/EBPalpha expression is sufficient to initiate myeloid differentiation from CLPs, as well as from proT and proB cells, even though proB cells do not give rise to myeloid cells after ectopic IL-2 stimulation. Expression of Pax5, a B lymphoid-affiliated transcription factor, is completely suppressed by enforced C/EBPalpha but not by ectopic IL-2 stimulation in proB cells. Introduction of Pax5 blocks ectopic IL-2 receptor-mediated myeloid lineage conversion in CLPs. These data suggest that C/EBPalpha is a proximal target of cytokine-induced lineage conversion in lymphoid progenitors. Furthermore, complete loss of Pax5 expression triggered by up-regulation of C/EBPalpha is a critical event for lineage conversion from lymphoid to myeloid lineage in CLPs and proB cells.
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Affiliation(s)
- Chia-Lin Hsu
- Department of Immunology, Duke University Medical Center, DUMC 3010, Research Drive, Durham, NC 27710, USA
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294
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Espinoza CR, Feeney AJ. The extent of histone acetylation correlates with the differential rearrangement frequency of individual VH genes in pro-B cells. THE JOURNAL OF IMMUNOLOGY 2006; 175:6668-75. [PMID: 16272322 DOI: 10.4049/jimmunol.175.10.6668] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
During B lymphocyte development, Ig heavy and L chain genes are assembled by V(D)J recombination. Individual V, D, and J genes rearrange at very different frequencies in vivo, and the natural variation in recombination signal sequence does not account for all of these differences. Because a permissive chromatin structure is necessary for the accessibility of VH genes for VH to DJH recombination, we hypothesized that gene rearrangement frequency might be influenced by the extent of histone modifications. Indeed, we found in freshly isolated pro-B cells from muMT mice a positive correlation between the level of enrichment of VHS107 genes in the acetylated histone fractions as assayed by chromatin immunoprecipitation, and their relative rearrangement frequency in vivo. In the VH7183 family, the very frequently rearranging VH81X gene showed the highest association with acetylated histones, especially in the newborn. Together, our data show that the extent of histone modifications in pro-B cells should be considered as a mechanism by which accessibility and the rearrangement level of individual VH genes is regulated.
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Affiliation(s)
- Celia R Espinoza
- Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA
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295
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Abstract
Mammals contend with a universe of evolving pathogens by generating an enormous diversity of antigen receptors during lymphocyte development. Precursor B and T cells assemble functional immunoglobulin (Ig) and T cell receptor (TCR) genes via recombination of numerous variable (V), diversity (D), and joining (J) gene segments. Although this combinatorial process generates significant diversity, genetic reorganization is inherently dangerous. Thus, V(D)J recombination must be tightly regulated to ensure proper lymphocyte development and avoid chromosomal translocations that cause lymphoid tumors. Each genomic rearrangement is mediated by a common V(D)J recombinase that recognizes sequences flanking all antigen receptor gene segments. The specificity of V(D)J recombination is due, in large part, to changes in the accessibility of chromatin at target gene segments, which either permits or restricts access to recombinase. The chromatin configuration of antigen receptor loci is governed by the concerted action of enhancers and promoters, which function as accessibility control elements (ACEs). In general, ACEs act as conduits for transcription factors, which in turn recruit enzymes that covalently modify or remodel nucleosomes. These ACE-mediated alterations are critical for activation of gene segment transcription and for opening chromatin associated with recombinase target sequences. In this chapter, we describe advances in understanding the mechanisms that control V(D)J recombination at the level of chromatin accessibility. The discussion will focus on cis-acting regulation by ACEs, the nuclear factors that control ACE function, and the epigenetic modifications that establish recombinase accessibility.
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Affiliation(s)
- Robin Milley Cobb
- Department of Microbiology and Immunology, Vanderbilt University, Nashville, Tennessee, USA
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296
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Zhou J, Saleque S, Ermakova O, Sepulveda MA, Yang Q, Eckhardt LA, Schildkraut CL, Birshtein BK. Changes in replication, nuclear location, and expression of the Igh locus after fusion of a pre-B cell line with a T cell line. THE JOURNAL OF IMMUNOLOGY 2005; 175:2317-20. [PMID: 16081801 PMCID: PMC2724393 DOI: 10.4049/jimmunol.175.4.2317] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
We have previously observed that replication and nuclear location of the murine Igh locus are developmentally regulated during B cell differentiation. In non-B, B, and plasma cells, sequences near the 3' end of the Igh locus replicate early in S while upstream Vh sequences replicate late in S, and the Igh locus is located near the nuclear periphery. In fact, in MEL non-B cells, replication of a 500-kb segment containing Igh-C and flanking sequences occurs progressively later throughout S by 3' to 5' unidirectional fork movement. In contrast, in pro- and pre-B cells, the entire 3-Mb Igh locus is located away from the nuclear periphery and replicates early in S by forks progressing in both directions. In this study, using an 18-81 (pre-B) x BW5147 (T) cell fusion system in which Igh expression is extinguished, we found that in all Igh alleles, Vh sequences replicated later in S than 3' Igh sequences (similar to that detected in BW5147), but the Igh locus was situated away from the nuclear periphery (similar to that observed in 18-81). Thus, pre-B cell-derived Igh genes had changes in replication timing, but not in nuclear location, whereas T cell-derived Igh genes changed their nuclear location but not their replication timing. These data are consistent with the silencing of a pre-B cell-specific replication program in the fusion hybrid cells and independent regulation of the nuclear location of Igh loci.
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Affiliation(s)
- Jie Zhou
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Shireen Saleque
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Olga Ermakova
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Manuel A. Sepulveda
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Qiaoxin Yang
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Laurel A. Eckhardt
- Department of Biological Sciences, Hunter College, and Graduate School of City University of New York, New York, NY 10021
| | - Carl L. Schildkraut
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
| | - Barbara K. Birshtein
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461
- Address correspondence and reprint requests to Dr. Barbara K. Birshtein, Department of Cell Biology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461. E-mail address:
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297
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Parker MJ, Licence S, Erlandsson L, Galler GR, Chakalova L, Osborne CS, Morgan G, Fraser P, Jumaa H, Winkler TH, Skok J, Mårtensson IL. The pre-B-cell receptor induces silencing of VpreB and lambda5 transcription. EMBO J 2005; 24:3895-905. [PMID: 16281060 PMCID: PMC1283949 DOI: 10.1038/sj.emboj.7600850] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2005] [Accepted: 10/06/2005] [Indexed: 01/17/2023] Open
Abstract
The pre-B-cell receptor (pre-BCR), composed of Ig heavy and surrogate light chain (SLC), signals pre-BII-cell proliferative expansion. We have investigated whether the pre-BCR also signals downregulation of the SLC genes (VpreB and lambda5), thereby limiting this expansion. We demonstrate that, as BM cells progress from the pre-BI to large pre-BII-cell stage, there is a shift from bi- to mono-allelic lambda5 transcription, while the second allele is silenced in small pre-BII cells. A VpreB1-promoter-driven transgene shows the same pattern, therefore suggesting that VpreB1 is similarly regulated and thereby defines the promoter as a target for transcriptional silencing. Analyses of pre-BCR-deficient mice show a temporal delay in lambda5 downregulation, thereby demonstrating that the pre-BCR is essential for monoallelic silencing at the large pre-BII-cell stage. Our data also suggest that SLP-65 is one of the signaling components important for this process. Furthermore, the VpreB1/lambda5 alleles undergo dynamic changes with respect to nuclear positioning and heterochromatin association, thereby providing a possible mechanism for their transcriptional silencing.
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Affiliation(s)
- Mathew J Parker
- Laboratory of Lymphocyte Signaling and Development, The Babraham Institute, Cambridge, UK
| | - Steve Licence
- Laboratory of Lymphocyte Signaling and Development, The Babraham Institute, Cambridge, UK
| | - Lena Erlandsson
- Laboratory of Lymphocyte Signaling and Development, The Babraham Institute, Cambridge, UK
| | | | - Lyubomira Chakalova
- Laboratory of Chromatin and Gene Expression, The Babraham Institute, Cambridge, UK
| | - Cameron S Osborne
- Laboratory of Chromatin and Gene Expression, The Babraham Institute, Cambridge, UK
| | - Geoff Morgan
- Flow Cytometry Facility, The Babraham Institute, Cambridge, UK
| | - Peter Fraser
- Laboratory of Chromatin and Gene Expression, The Babraham Institute, Cambridge, UK
| | - Hassan Jumaa
- Institute for Biology III, Max-Planck-Institute for Immunobiology, Freiburg, Germany
| | | | - Jane Skok
- Department of Immunology and Molecular Pathology, UCL, London, UK
| | - Inga-Lill Mårtensson
- Laboratory of Lymphocyte Signaling and Development, The Babraham Institute, Cambridge, UK
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298
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Curry JD, Geier JK, Schlissel MS. Single-strand recombination signal sequence nicks in vivo: evidence for a capture model of synapsis. Nat Immunol 2005; 6:1272-9. [PMID: 16286921 DOI: 10.1038/ni1270] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2005] [Accepted: 09/16/2005] [Indexed: 11/08/2022]
Abstract
Variable (diversity) joining (V(D)J) recombination is initiated by the introduction of single-strand DNA breaks (nicks) at recombination signal sequences (RSSs). The importance and fate of these RSS nicks for the regulation of the V(D)J rearrangement and their potential contribution to genomic instability are poorly understood. Using two new methodologies, we were able to detect and quantify specific RSS nicks introduced into genomic DNA by incubation with recombination-activating gene proteins in vitro. In vivo, however, we found that nicks mediated by recombination-activating gene (RAG) proteins were detectable only in gene segments associated with RSSs containing 12-base pair spacers but not in those containing 23-base pair spacers. These data support a model of capture rather than synapsis for pairwise RSS cleavage during V(D)J recombination.
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Affiliation(s)
- John D Curry
- Department of Molecular and Cell Biology, Division of Immunology, University of California, Berkeley, California 94720-3200, USA
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299
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van Zelm MC, van der Burg M, de Ridder D, Barendregt BH, de Haas EFE, Reinders MJT, Lankester AC, Révész T, Staal FJT, van Dongen JJM. Ig Gene Rearrangement Steps Are Initiated in Early Human Precursor B Cell Subsets and Correlate with Specific Transcription Factor Expression. THE JOURNAL OF IMMUNOLOGY 2005; 175:5912-22. [PMID: 16237084 DOI: 10.4049/jimmunol.175.9.5912] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The role of specific transcription factors in the initiation and regulation of Ig gene rearrangements has been studied extensively in mouse models, but data on normal human precursor B cell differentiation are limited. We purified five human precursor B cell subsets, and assessed and quantified their IGH, IGK, and IGL gene rearrangement patterns and gene expression profiles. Pro-B cells already massively initiate D(H)-J(H) rearrangements, which are completed with V(H)-DJ(H) rearrangements in pre-B-I cells. Large cycling pre-B-II cells are selected for in-frame IGH gene rearrangements. The first IGK/IGL gene rearrangements were initiated in pre-B-I cells, but their frequency increased enormously in small pre-B-II cells, and in-frame selection was found in immature B cells. Transcripts of the RAG1 and RAG2 genes and earlier defined transcription factors, such as E2A, early B cell factor, E2-2, PAX5, and IRF4, were specifically up-regulated at stages undergoing Ig gene rearrangements. Based on the combined Ig gene rearrangement status and gene expression profiles of consecutive precursor B cell subsets, we identified 16 candidate genes involved in initiation and/or regulation of Ig gene rearrangements. These analyses provide new insights into early human precursor B cell differentiation steps and represent an excellent template for studies on oncogenic transformation in precursor B acute lymphoblastic leukemia and B cell differentiation blocks in primary Ab deficiencies.
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Affiliation(s)
- Menno C van Zelm
- Department of Immunology, Erasmus MC, University Medical Center, Rotterdam, The Netherlands
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300
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Medina KL, Singh H. Gene regulatory networks orchestrating B cell fate specification, commitment, and differentiation. Curr Top Microbiol Immunol 2005; 290:1-14. [PMID: 16480036 DOI: 10.1007/3-540-26363-2_1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The B cell developmental pathway represents a leading system for the analysis of regulatory circuits that orchestrate cell fate specification, commitment, and differentiation. We review the progress that has been achieved in the identification and characterization of regulatory components of such circuits, including transcription factors, chromatin modifying proteins, and signaling molecules. A comprehensive developmental model is proposed that invokes sequentially acting regulatory networks which dictate the generation of B cells from multipotential hematopoietic progenitors.
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Affiliation(s)
- K L Medina
- Howard Hughes Medical Institute, The University of Chicago, IL 60637, USA
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