scholarly journals TET2 deficiency reprograms the germinal center B cell epigenome and silences genes linked to lymphomagenesis

2020 ◽  
Vol 6 (25) ◽  
pp. eaay5872 ◽  
Author(s):  
Wojciech Rosikiewicz ◽  
Xiaowen Chen ◽  
Pilar M. Dominguez ◽  
Hussein Ghamlouch ◽  
Said Aoufouchi ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Somatic Hypermutation ◽  
Cell Receptor ◽  
Regulatory Elements ◽  
Dna Hypermethylation ◽  
Epigenetic Effects ◽  
Germinal Center B Cell ◽  
Epigenetic Pattern

The TET2 DNA hydroxymethyltransferase is frequently disrupted by somatic mutations in diffuse large B cell lymphomas (DLBCLs), a tumor that originates from germinal center (GC) B cells. Here, we show that TET2 deficiency leads to DNA hypermethylation of regulatory elements in GC B cells, associated with silencing of the respective genes. This hypermethylation affects the binding of transcription factors including those involved in exit from the GC reaction and involves pathways such as B cell receptor, antigen presentation, CD40, and others. Normal GC B cells manifest a typical hypomethylation signature, which is caused by AID, the enzyme that mediates somatic hypermutation. However, AID-induced demethylation is markedly impaired in TET2-deficient GC B cells, suggesting that AID epigenetic effects are partially dependent on TET2. Last, we find that TET2 mutant DLBCLs also manifest the aberrant TET2-deficient GC DNA methylation signature, suggesting that this epigenetic pattern is maintained during and contributes to lymphomagenesis.

scholarly journals Uhrf1 regulates germinal center B cell expansion and affinity maturation to control viral infection

2018 ◽  
Vol 215 (5) ◽  
pp. 1437-1448 ◽  
Author(s):  
Chao Chen ◽  
Sulan Zhai ◽  
Le Zhang ◽  
Jingjing Chen ◽  
Xuehui Long ◽  
...  
Keyword(s):  
Cell Proliferation ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Somatic Hypermutation ◽  
Ring Finger ◽  
Affinity Maturation ◽  
Virus Clearance ◽  
Germinal Center B Cell ◽  
Pathogen Clearance

The production of high-affinity antibody is essential for pathogen clearance. Antibody affinity is increased through germinal center (GC) affinity maturation, which relies on BCR somatic hypermutation (SHM) followed by antigen-based selection. GC B cell proliferation is essentially involved in these processes; it provides enough templates for SHM and also serves as a critical mechanism of positive selection. In this study, we show that expression of epigenetic regulator ubiquitin-like with PHD and RING finger domains 1 (Uhrf1) was markedly up-regulated by c-Myc–AP4 in GC B cells, and it was required for GC response. Uhrf1 regulates cell proliferation–associated genes including cdkn1a, slfn1, and slfn2 by DNA methylation, and its deficiency inhibited the GC B cell cycle at G1-S phase. Subsequently, GC B cell SHM and affinity maturation were impaired, and Uhrf1 GC B knockout mice were unable to control chronic virus infection. Collectively, our data suggest that Uhrf1 regulates GC B cell proliferation and affinity maturation, and its expression in GC B cells is required for virus clearance.

scholarly journals Antigen-affinity controls pre-germinal center B cell selection by promoting Mcl-1 induction through BAFF receptor signaling

2016 ◽  
Vol 6 (1) ◽  
Author(s):  
Felix M. Wensveen ◽  
Erik Slinger ◽  
Martijn HA van Attekum ◽  
Robert Brink ◽  
Eric Eldering
Keyword(s):  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Cell Selection ◽  
Germinal Center Reaction ◽  
Cell Pool ◽  
Germinal Center B Cell ◽  
Pi3k Activation

Abstract Upon antigen encounter, the responsive B cell pool undergoes stringent selection which eliminates cells with low B cell receptor (BCR) affinity. Already before formation of the germinal center, activated B cells of low-affinity are negatively selected in a process that is molecularly not well understood. In this study, we investigated the mechanism behind pre-GC affinity-mediated B cell selection. We applied affinity mutants of HEL antigen and found that rapidly after activation B cells become highly dependent on the cytokine BAFF. Moreover, expression of BAFF receptor CD268 is regulated in a BCR-affinity dependent fashion. High affinity responses via BAFF correlated with PI3K activation, which controlled expression of the pro-survival protein Mcl-1, and thereby increased survival. In the presence of excess BAFF, or in absence of the Mcl-1 antagonist Noxa, more low-affinity B cells survived the first two days after antigen encounter. This resulted in increased numbers of antigen-specific B cells of low affinity upon immunization and reduced the overall affinity of cells that contributed to the germinal center reaction. Our findings elucidate a crucial molecular pathway of B cell selection in the earliest phases of activation by identifying a novel link between BCR affinity and BAFF-R signaling towards Mcl-1.

scholarly journals Signatures of B Cell Receptor Repertoire Following Pneumocystis Infection

2021 ◽  
Vol 12 ◽  
Author(s):  
Han Sun ◽  
Hu-Qin Yang ◽  
Kan Zhai ◽  
Zhao-Hui Tong
Keyword(s):  
B Cells ◽  
B Cell ◽  
Single Cell ◽  
Plasma Cells ◽  
Somatic Hypermutation ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Receptor Repertoire ◽  
Elevated Expression ◽  
Pneumocystis Infection

B cells play vital roles in host defense against Pneumocystis infection. However, the features of the B cell receptor (BCR) repertoire in disease progression remain unclear. Here, we integrated single-cell RNA sequencing and single-cell BCR sequencing of immune cells from mouse lungs in an uninfected state and 1–4 weeks post-infection in order to illustrate the dynamic nature of B cell responses during Pneumocystis infection. We identified continuously increased plasma cells and an elevated ratio of (IgA + IgG) to (IgD + IgM) after infection. Moreover, Pneumocystis infection was associated with an increasing naïve B subset characterized by elevated expression of the transcription factor ATF3. The proportion of clonal expanded cells progressively increased, while BCR diversity decreased. Plasma cells exhibited higher levels of somatic hypermutation than naïve B cells. Biased usage of V(D)J genes was observed, and the usage frequency of IGHV9-3 rose. Overall, these results present a detailed atlas of B cell transcriptional changes and BCR repertoire features in the context of Pneumocystis infection, which provides valuable information for finding diagnostic biomarkers and developing potential immunotherapeutic targets.

scholarly journals Germinal center B cell development has distinctly regulated stages completed by disengagement from T cell help

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Ting-ting Zhang ◽  
David G Gonzalez ◽  
Christine M Cote ◽  
Steven M Kerfoot ◽  
Shaoli Deng ◽  
...  
Keyword(s):  
T Cell ◽  
B Cells ◽  
B Cell ◽  
Germinal Center ◽  
B Cell Differentiation ◽  
B Cell Maturation ◽  
Germinal Center B Cell ◽  
T Cell Help ◽  
Dose Dependent

To reconcile conflicting reports on the role of CD40 signaling in germinal center (GC) formation, we examined the earliest stages of murine GC B cell differentiation. Peri-follicular GC precursors first expressed intermediate levels of BCL6 while co-expressing the transcription factors RelB and IRF4, the latter known to repress Bcl6 transcription. Transition of GC precursors to the BCL6hi follicular state was associated with cell division, although the number of required cell divisions was immunogen dose dependent. Potentiating T cell help or CD40 signaling in these GC precursors actively repressed GC B cell maturation and diverted their fate towards plasmablast differentiation, whereas depletion of CD4+ T cells promoted this initial transition. Thus while CD40 signaling in B cells is necessary to generate the immediate precursors of GC B cells, transition to the BCL6hi follicular state is promoted by a regional and transient diminution of T cell help.

scholarly journals A Novel Cytological Model of B-Cell/Macrophage Biphenotypic Cell Hodgkin Lymphoma in Ganp-Transgenic Mice

Cancers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 204 ◽  
Author(s):  
Sakai ◽  
Rezano ◽  
Okada ◽  
Ohtsuki ◽  
Kawashima ◽  
...  
Keyword(s):  
B Cells ◽  
Transgenic Mice ◽  
B Cell ◽  
Hodgkin Lymphoma ◽  
Germinal Center ◽  
Lymphoid Tumor ◽  
Germinal Center B Cell ◽  
Macrophage Colony Stimulating Factor ◽  
Macrophage Colony ◽  
Factor Α

Hodgkin lymphoma (HL) is one of the most difficult neoplasms in terms of cytopathological research owing to the lack of established cytological murine models. Although HL is believed to be of lymphoid germinal center B-cell origin, HL cells exhibit unique biphenotypic characteristics of B cells and macrophages. B-cell/macrophage biphenotypic cells have also been identified in the spleen of Lyn-deficient mice. Moreover, Lyn-targeting germinal center-associated nuclear protein (GANP)-transgenic mice (Ig-ganpTg mice) spontaneously develop a lymphoid tumor. We aimed to investigate whether the lymphoid tumor developed in Ig-ganpTg mice exhibit biphenotypic characteristics of B cells/macrophages that correspond to human HL. Here, we demonstrated GANP overexpression in human HL cells and found that it may regulate transdifferentiation between B cells and macrophages. We also demonstrated that tumors were comparable with B-cell/macrophage biphenotypic Hodgkinoid lymphomas. The tumor cells expressed macrophage-related F4/80, CD68, and CD204 as well as cytoplasmic B220 and µ-/κ-chains; in addition, these cells exhibited phagocytic activity. These cells also expressed transcripts of CD30; c-fms; and the cytokines monocyte chemoattractant protein (MCP)-1, MCP-5, RANTES, tumor necrosis factor-α and thrombopoietin associated with macrophages as well as granulocyte/macrophage colony-stimulating factor, interleukin (IL)-4, IL-10, IL-12, and IL-13. Ig-ganpTg mice represent a novel cytological model for the study of cytopathological etiology and oncogenesis of HL.

Transformation of BCR-deficient germinal-center B cells by EBV supports a major role of the virus in the pathogenesis of Hodgkin and posttransplantation lymphomas

Blood ◽  
2005 ◽  
Vol 106 (13) ◽  
pp. 4345-4350 ◽  
Author(s):  
Dörte Bechtel ◽  
Julia Kurth ◽  
Claus Unkel ◽  
Ralf Küppers
Keyword(s):  
B Cells ◽  
Cell Lines ◽  
Germinal Center ◽  
Somatic Hypermutation ◽  
Cell Receptor ◽  
Lymphoproliferative Disease ◽  
Barr Virus ◽  
Classic Hodgkin Lymphoma ◽  
Epstein Barr

In classic Hodgkin lymphoma (HL) and posttransplantation lymphoproliferative disease (PTLD), 2 malignancies frequently associated with Epstein-Barr virus (EBV), the tumor cells often appear to derive from B-cell receptor (BCR)–deficient and therefore preapoptotic germinal center (GC) B cells. To test whether EBV can rescue BCR-less GC B cells, we infected human tonsillar CD77+ GC B cells in vitro with EBV. More than 60 monoclonal lymphoblastoid cell lines (LCLs) were established. Among these, 28 cell lines did not express surface immunoglobulin (sIg). Two of the sIg-negative cell lines carry obviously destructive mutations that have been introduced into originally functional VH gene rearrangements during the process of somatic hypermutation. Quantitative reverse transcriptase–polymerase chain reaction (RT-PCR) showed that in most other lines the sIg deficiency was not simply the result of transcriptional down-regulation, but it was rather due to posttranscriptional defects. These findings strongly support the idea that EBV plays a central role in the pathogenesis of classic HL and PTLD by rescuing BCR-deficient, preapoptotic GC B cells from apoptosis, and that EBV infection renders the cells independent from survival signals normally supplied by a BCR. The monoclonal LCLs represent valuable models for early stages of lymphoma development in classic HL and PTLD.

GCET2, a New Adaptor Protein in B Cell Signaling.

Blood ◽  
2005 ◽  
Vol 106 (11) ◽  
pp. 1917-1917
Author(s):  
Zenggang Pan ◽  
Yulei Shen ◽  
Baosheng Ge ◽  
Cheng Du ◽  
Timothy McKeithan ◽  
...  
Keyword(s):  
Plasma Membrane ◽  
B Cells ◽  
B Cell ◽  
Tyrosine Phosphorylation ◽  
Germinal Center ◽  
Adaptor Protein ◽  
Phosphorylation Sites ◽  
Germinal Center B Cell ◽  
Membrane Attachment ◽  
Cloned Gene

Abstract GCET2 (Germinal Center B-cell Expressed Transcript 2; also named HGAL, Human Germinal center-Associated Lymphoma) is a newly cloned gene that has been shown to be a useful marker for germinal center (GC) B-cells and GC B-cell derived malignancies, including follicular lymphomas and germinal center B cell-like diffuse large B-cell lymphomas (GCB-DLBCLs). GCET2 is also a prognostic indicator for DLBCLs, and patients with higher expression of GCET2 have significantly better survival than those with lower expression. We cloned GCET2 from a number of GC B cell-restricted expressed sequence tags (ESTs) in order to study the differentiation of GC B-cells and to elucidate the mechanisms underlying the GC reaction, which is not well understood. We are report here the biochemical and biological properties of GCET2, which may help to determine its role in the GC reaction. Sequence analysis of GCET2 did not reveal any known domains but predicted five tyrosine phosphorylation sites, all of which are conserved in its mouse homologue, M17, also a GC B cell-restricted transcript. We first determined the cellular localization of GCET2 using subcellular fractionation of a B cell line, DHL16, and found that GCET2 is constitutively localized in cellular membranes but is excluded from lipid rafts. These findings were further confirmed by fluorescence confocal microscopy. GCET2 does not have a transmembrane domain but has a putative myristoylation site and a putative palmitoylation site, which may mediate its membrane attachment. Using 3H metabolic labeling, we demonstrated that GCET2 was both myristoylated and palmitoylated, and GCET2 lost its membrane association after mutating both of these sites, indicating that the membrane attachment of GCET2 is mediated by these two post-translational modifications. We then studied tyrosine phosphorylation of GCET2. In both Daudi and DHL16 cells, GCET2 was phosphorylated following pervanadate treatment. By serially mutating the five predicated tyrosine-phosphorylation sites, we found that the distal three sites are crucial for GCET2 phosphorylation. GCET2 was also phosphorylated when co-transfected into COS7 cells with protein tyrosine kinases (PTKs) LYN, LCK or SYK, and therefore it may be a substrate of these kinases in B cells. GCET2 has a conserved GRB2 binding site, and it indeed associates with GRB2 following pervanadate treatment. Our data suggest that GCET2 acts as an adaptor protein in GC B-cells by transducing signals from GC B-cell membrane to the cytosol. Our working model is as follows: a stimulus to GC B-cells induces the activation of PTKs LYN and SYK, which sequentially phosphorylate GCET2 at the plasma membrane. Phosphorylated GCET2 then recruits GRB2 from the cytosol to the plasma membrane, and this complex further recruits additional partners and activates downstream pathways, which function in the GC reaction. We are currently identifying other proteins in the GCET2/GRB2 complex to determine the pathways downstream of GCET2 activation.

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