Loss of the FOXP1 transcription factor leads to deregulation of B lymphocyte development and function at multiple stages
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE137463 | GEO | 2019/09/17
REPOSITORIES: GEO
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Project description:Somatic hypermutation (SHM) and class switch recombination (CSR) increase the affinity and diversify the effector functions of antibodies during immune responses. Although SHM and CSR are fundamentally different, their independent roles in regulating B cell fate have been difficult to uncouple because a single enzyme, activation-induced cytidine deaminase (encoded by Aicda), initiates both reactions. Here, we used a combination of Aicda and antibody mutant alleles that separate the effects of CSR and SHM on polyclonal immune responses. We found that class-switching to IgG1 biased the fate choice made by B cells, favoring the plasma cell over memory cell fate without significantly affecting clonal expansion in the germinal center (GC). In contrast, SHM reduced the longevity of memory B cells by creating polyreactive specificities that were selected against over time. Our data define the independent contributions of SHM and CSR to the generation and persistence of memory in the antibody system.
2016-10-19 | GSE76864 | GEO
Project description:Somatic hypermutation (SHM) and class switch recombination (CSR) increase the affinity and diversify the effector functions of antibodies during immune responses. Although SHM and CSR are fundamentally different, their independent roles in regulating B cell fate have been difficult to uncouple because a single enzyme, activation-induced cytidine deaminase (encoded by Aicda), initiates both reactions. Here, we used a combination of Aicda and antibody mutant alleles that separate the effects of CSR and SHM on polyclonal immune responses. We found that class-switching to IgG1 biased the fate choice made by B cells, favoring the plasma cell over memory cell fate without significantly affecting clonal expansion in the germinal center (GC). In contrast, SHM reduced the longevity of memory B cells by creating polyreactive specificities that were selected against over time. Our data define the independent contributions of SHM and CSR to the generation and persistence of memory in the antibody system.
2016-10-19 | GSE76865 | GEO
Project description:Most human B cell lymphomas (B-NHL) are derived from germinal centers (GCs), the structure where B-cells undergo class switch recombination (CSR) and somatic hypermutation (SHM) and are selected for high-affinity antibody production. The pathogenesis of B-NHL is associated with distinct genetic lesions, including chromosomal translocations and aberrant somatic hypermutation, which appear to arise from mistakes occurring during CSR and SHM. To ascertain the role of CSR and SHM in lymphomagenesis, we crossed three oncogene-driven (MYC, BCL6, MYC/BCL6) mouse models of B cell lymphoma with mice lacking activation-induced cytidine deaminase (AID), the enzyme required for both processes. We show that AID deficiency prevents BCL6-dependent, GC-derived B-NHL, while it has no impact on the formation of MYC-driven, pre-GC lymphomas. Accordingly, abrogation of AID is associated with the disappearance of both CSR- and SHM-mediated structural alterations, including cMYC-IgH chromosomal translocations and aberrant SHM. These results demonstrate that AID is required for GC-derived lymphomagenesis, providing direct support to the notion that errors in AID-mediated antigen-receptor gene modification events represent major contributors to the pathogenesis of human B-NHL. Keywords: Phenotypic characterization of tumors developing in oncogene-driven mouse models of lymphomas
2007-11-01 | GSE9249 | GEO
Project description:The activation induced cytosine deaminase (AID) mediates diversification of B cell immunoglobulin genes by the three distinct yet related processes of somatic hypermutation (SHM), class switch recombination (CSR), and gene conversion (GCV). SHM occurs in germinal center B cells, and the transcription factor Bcl6 is a key regulator of the germinal center B cell gene expression program, including expression of AID. To test the hypothesis that Bcl6 function is important for the process of SHM, we compared WT chicken DT40 B cells, which constitutively perform SHM/GCV, to their Bcl6-deficient counterparts. We found that Bcl6-deficient DT40 cells were unable to perform SHM and GCV despite enforced high level expression of AID and substantial levels of AID in the nucleus of the cells. To gain mechanistic insight into the GCV/SHM dependency on Bcl6, transcriptional features of a highly expressed SHM target gene were analyzed in Bcl6-sufficient and -deficient DT40 cells. No defect was observed in the accumulation of single stranded DNA in the target gene as a result of Bcl6 deficiency. In contrast, association of Spt5, an RNA polymerase II (Pol II) and AID binding factor, was strongly reduced at the target gene body relative to the transcription start site in Bcl6-deficient cells as compared to WT cells. However, partial reconstitution of Bcl6 function substantially reconstituted Spt5 association with the target gene body but did not restore detectable SHM. Our observations suggest that in the absence of Bcl6, Spt5 fails to associate efficiently with Pol II at SHM targets, perhaps precluding robust AID action on the SHM target DNA. Our data also suggest, however, that Spt5 binding is not sufficient for SHM of a target gene even in DT40 cells with strong expression of AID. Sequencing of the IgL V region and mutationally active GFP transgene in WT, Bcl6-/- Pax5R, and Bcl6-/- Pax5R Bcl6R chicken DT40 cells for evidence of AID dependent mutations. ChIP-seq proiles of RNA Pol II, Spt5, and pSer5 Pol II at a GFP transgene in WT, Bcl6-/- Pax5R, and Bcl6-/- Pax5R Bcl6R chicken DT40 cells.
2016-02-21 | E-GEOD-77141 | biostudies-arrayexpress
Project description:The activation induced cytosine deaminase (AID) mediates diversification of B cell immunoglobulin genes by the three distinct yet related processes of somatic hypermutation (SHM), class switch recombination (CSR), and gene conversion (GCV). SHM occurs in germinal center B cells, and the transcription factor Bcl6 is a key regulator of the germinal center B cell gene expression program, including expression of AID. To test the hypothesis that Bcl6 function is important for the process of SHM, we compared WT chicken DT40 B cells, which constitutively perform SHM/GCV, to their Bcl6-deficient counterparts. We found that Bcl6-deficient DT40 cells were unable to perform SHM and GCV despite enforced high level expression of AID and substantial levels of AID in the nucleus of the cells. To gain mechanistic insight into the GCV/SHM dependency on Bcl6, transcriptional features of a highly expressed SHM target gene were analyzed in Bcl6-sufficient and -deficient DT40 cells. No defect was observed in the accumulation of single stranded DNA in the target gene as a result of Bcl6 deficiency. In contrast, association of Spt5, an RNA polymerase II (Pol II) and AID binding factor, was strongly reduced at the target gene body relative to the transcription start site in Bcl6-deficient cells as compared to WT cells. However, partial reconstitution of Bcl6 function substantially reconstituted Spt5 association with the target gene body but did not restore detectable SHM. Our observations suggest that in the absence of Bcl6, Spt5 fails to associate efficiently with Pol II at SHM targets, perhaps precluding robust AID action on the SHM target DNA. Our data also suggest, however, that Spt5 binding is not sufficient for SHM of a target gene even in DT40 cells with strong expression of AID.
2016-02-21 | GSE77141 | GEO
Project description:CD4+ T follicular helper (Tfh) cells are essential for germinal center (GC) and high-affinity antibody responses. Yet the regulation that determines the initial development of Tfh cells is still largely unknown. Here we find that transcription factor Foxp1, previously shown to be essential in maintaining T cell quiescence, is a rate-limiting and essential negative regulator of Tfh cell differentiation. NaM-CM-/ve CD4+ T cells constitutively express Foxp1A, and stimulation through the T cell receptor (TCR) transiently induces the expression of a shorter Foxp1D isoform. In T cell-dependent (TD) humoral responses, CD4+ T cells deficient in all Foxp1 isoforms preferentially differentiate into Tfh cells, resulting in substantially increased GC and antibody responses. This negative regulation of Foxp1 on Tfh cell differentiation shows profound dominance: even in the absence of B cells, Foxp1-deficient CD4+ T cells differentiate into Tfh cells with high frequencies and sustained Bcl6 expression. Further, in the absence of Foxp1, Tfh cells are generated in higher frequencies than seen with Bcl6 overexpression and Tfh cell differentiation becomes significantly resistant to Blimp1-mediated repression. Finally, our experiments reveal specific roles of Foxp1A and Foxp1D in inhibiting Tfh cell differentiation: TCR-induced Foxp1D functions as a M-bM-^@M-^XgatekeeperM-bM-^@M-^Y to block the initial Tfh cell development, and together Foxp1A and Foxp1D proteins inversely determine Tfh cell generation in a dosage-dependent manner. Our study suggests that two Foxp1 isoforms provide a M-bM-^@M-^\double checkM-bM-^@M-^] mechanism as fundamental regulators in Tfh cell differentiation and humoral responses. Gene expression analysis of ex vivo OT-II Foxp1-WT Tfh cells and OT-II Foxp-conditional knockout (CKO) Tfh cells 5 days after immunization.
2014-05-18 | E-GEOD-50725 | biostudies-arrayexpress
Project description:CD4+ T follicular helper (Tfh) cells are essential for germinal center (GC) and high-affinity antibody responses. Yet the regulation that determines the initial development of Tfh cells is still largely unknown. Here we find that transcription factor Foxp1, previously shown to be essential in maintaining T cell quiescence, is a rate-limiting and essential negative regulator of Tfh cell differentiation. Naïve CD4+ T cells constitutively express Foxp1A, and stimulation through the T cell receptor (TCR) transiently induces the expression of a shorter Foxp1D isoform. In T cell-dependent (TD) humoral responses, CD4+ T cells deficient in all Foxp1 isoforms preferentially differentiate into Tfh cells, resulting in substantially increased GC and antibody responses. This negative regulation of Foxp1 on Tfh cell differentiation shows profound dominance: even in the absence of B cells, Foxp1-deficient CD4+ T cells differentiate into Tfh cells with high frequencies and sustained Bcl6 expression. Further, in the absence of Foxp1, Tfh cells are generated in higher frequencies than seen with Bcl6 overexpression and Tfh cell differentiation becomes significantly resistant to Blimp1-mediated repression. Finally, our experiments reveal specific roles of Foxp1A and Foxp1D in inhibiting Tfh cell differentiation: TCR-induced Foxp1D functions as a ‘gatekeeper’ to block the initial Tfh cell development, and together Foxp1A and Foxp1D proteins inversely determine Tfh cell generation in a dosage-dependent manner. Our study suggests that two Foxp1 isoforms provide a “double check” mechanism as fundamental regulators in Tfh cell differentiation and humoral responses.
2014-05-18 | GSE50725 | GEO
Project description:Activation-induced cytidine deaminase (AID) plays a vital role in adaptive immunity by enabling class switch recombination (CSR) and somatic hypermutation (SHM). While many molecular factors affect AID targeting and function, mounting evidence implicates G-quadruplex (G4) nucleic acid structures as critical effectors of AID biology. To examine the function of AID-G4 binding in vivo, we generated a knock-in mouse with a mutation in Aicda (AIDG133V) that disrupts AID-G4 binding without altering DNA deaminase activity. AIDG133V mice completely lack CSR and SHM, modeling the pathology of hyper-IgM syndrome patients with an orthologous mutation. ChIP-sequencing experiments reveal a broad defect in AIDG133V chromatin localization, implicating AID-G4 binding in genome-wide AID targeting. We find that major histocompatibility complex (MHC) class II genes are AID targets, and that increased AID expression in diffuse large B-cell lymphomas (DLBCLs) correlates with decreased MHC class II expression. Given that loss of MHC class II expression in DLBCLs is highly correlated with adverse outcomes, AID-dependent gene regulation may provide a novel therapeutic target.
2020-10-14 | GSE136959 | GEO
Project description:The transcription factor FOXP1 is implicated in the pathogenesis of B-cell lymphomas through immunoglobulin heavy chain (IGH) locus-related chromosomal translocations leading to dysregulated expression of FOXP1. Translocations of FOXP1 with non-IG gene sequences have been also reported, but the molecular consequences of such aberrations remain undetermined. Here, using molecular cytogenetics and molecular biology studies, we comprehensively analyzed four lymphoma cases with non-IG rearrangements of FOXP1 and compared these with cases harboring t(3;14)(p13;q32)/IGH-FOXP1 and FOXP1-expressing lymphomas without underlying t(3p13/FOXP1). We found that non-IG rearrangements are usually acquired during evolution of lymphoma and constantly target the coding region of FOXP1, promiscuously fusing with coding and non-coding gene sequences at various reciprocal breakpoints (2q36, 10q24 and 3q11). Intriguingly, these rearrangements do not generate functional chimeric genes but commonly disrupt the full-length FOXP1 transcript leading to an aberrant expression of N-truncated FOXP1 isoforms, as shown by QRT-PCR and Western blot analysis. In contrast, cases with t(3;14)(p13;q32)/IGH-FOXP1 overexpress the full-length FOXP1. Collectively, our findings point to a dual mechanism through which FOXP1 is implicated in B-cell lymphomagenesis. The primary t(3;14)(p13;q32)/IGH-FOXP1 produces the full-length protein with potent oncogenic activity, whereas the secondary non-IG 17 rearrangements of FOXP1 generate N-truncated FOXP1 isoforms, likely driving progression of disease. Using molecular cytogenetics and molecular biology studies (including RNA-seq), we comprehensively analyzed four lymphoma cases with non-IG rearrangements of FOXP1 and compared these with cases harboring t(3;14)(p13;q32)/IGH-FOXP1 and FOXP1-expressing lymphomas without underlying t(3p13/FOXP1).
2013-09-04 | E-GEOD-50514 | biostudies-arrayexpress
Project description:Identification of peptides matching to LCK in FOXP1 immunoprecipitates from HONE1 cells by mass spectrometry
2022-04-04 | PXD031014 | Pride