Project description:T follicular helper (Tfh) cells are essential for germinal center B cell responses; however, the molecular mechanism underlying Tfh cell programming, in particular, the initial Tfh cell development, remains largely unknown. Here, we show that in vivo, despite enhanced non-Tfh effector functions, the deletion of transcription factor Bach2 still results in preferential Tfh cell differentiation. Mechanistically, the deletion of Bach2 leads to the induction of CXCR5 expression even before the up-regulation of Ascl2. Subsequently we identified a novel regulatory element in the murine CXCR5 locus that negatively regulates CXCR5 promoter activities in a Bach2-dependent manner. Furthermore, we find that Bach2 is also essential for CD4+ T cell memory including Tfh cell memory. These results demonstrate that Bach2 is a novel critical player in controlling Tfh cell responses.
Project description:The transcription factor Bach2 is a critical negative regulator of Tfh cell differentiation, especially IL-4 subset. Tfh cells from the mesenteric lymph nodes of WT and Bach2 CD4 conditional KO mice were collected to process the Rna-seq. Mechanistically, Bach2 may limit abnormal IL-4-produicng Tfh cell formation by repressing c-Maf, CXCR5 and IL-4.
Project description:We identified Bach2 as factor to be expressed at low levels in Tfh cells. Induced overexpression of Bach2 in the germinal center reaction results in loss of the Tfh cell population. RNA-seq of sorted antigen-specific Tfh and non-Tfh cells 18 hours after induction of Bach2 overexpression allowed the simultaneous analysis of Bach2 regulated genes and genes differentially expressed in Tfh and non-Tfh cells.
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.
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.
Project description:The B cell-specific BACH2 transcription factor is required for affinity maturation of mature B cells. Here, we show that Bach2 mediates negative selection at the pre-B cell receptor checkpoint and functions as a critical safeguard against leukemogenesis. Bach2-mediated activation of p53 is required for stringent elimination of pre-B cells that failed to productively rearrange immunoglobulin VH-DJH gene segments, and thus lack pre-B cell receptor expression. Upon productive VH-DJH gene rearrangement, pre-B cell receptor signaling ends negative selection through BCL6-mediated repression of p53. In patients with pre-B acute lymphoblastic leukemia, Bach2-mediated checkpoint control is frequently compromised and low levels of Bach2 expression represent a strong independent predictor of poor clinical outcome. Bach2+/+ pre-B cells resist leukemic transformation by Myc through Bach2-dependent upregulation of p53. Upon transformation with Myc, Bach2-/- pre-B cells fail to upregulate p53, form large colonies and initiate fatal leukemia in transplant recipient mice. ChIP-seq and gene expression analyses revealed that BACH2 competes with BCL6 for promoter binding and reverses BCL6-mediated repression of p53 and multiple other checkpoint control genes. These findings identify Bach2 as a key activator of p53 in pre-B cells, which is critical to maintain stringency of the pre-B cell receptor checkpoint and an important barrier against leukemic transformation. ChIP-seq using BACH2 and BCL6 antibodies in OCI-Ly7 cells
Project description:Natural killer (NK) cells are critical to immune surveillance against infections and cancer. Their role in immune surveillance requires that NK cells are present within tissues in a quiescent state. Mechanisms by which NK cells remain quiescent in tissues are incompletely elucidated. The transcriptional repressor BACH2 plays a critical role within the adaptive immune system, but its function within innate lymphocytes has been unclear. Here, we show that BACH2 acts as an intrinsic negative regulator of NK cell maturation and function. BACH2 is expressed within developing and mature NK cells and promotes the maintenance of immature NK cells by restricting their maturation in the presence of weak stimulatory signals. Loss of BACH2 within NK cells results in accumulation of activated NK cells with unrestrained cytotoxic function within tissues, which mediate augmented immune surveillance to pulmonary cancer metastasis. These findings establish a critical function of BACH2 as a global negative regulator of innate cytotoxic function and tumor immune surveillance by NK cells.
Project description:The B cell-specific BACH2 transcription factor is required for affinity maturation of mature B cells. Here, we show that Bach2 mediates negative selection at the pre-B cell receptor checkpoint and functions as a critical safeguard against leukemogenesis. Bach2-mediated activation of p53 is required for stringent elimination of pre-B cells that failed to productively rearrange immunoglobulin VH-DJH gene segments, and thus lack pre-B cell receptor expression. Upon productive VH-DJH gene rearrangement, pre-B cell receptor signaling ends negative selection through BCL6-mediated repression of p53. In patients with pre-B acute lymphoblastic leukemia, Bach2-mediated checkpoint control is frequently compromised and low levels of Bach2 expression represent a strong independent predictor of poor clinical outcome. Bach2+/+ pre-B cells resist leukemic transformation by Myc through Bach2-dependent upregulation of p53. Upon transformation with Myc, Bach2-/- pre-B cells fail to upregulate p53, form large colonies and initiate fatal leukemia in transplant recipient mice. ChIP-seq and gene expression analyses revealed that BACH2 competes with BCL6 for promoter binding and reverses BCL6-mediated repression of p53 and multiple other checkpoint control genes. These findings identify Bach2 as a key activator of p53 in pre-B cells, which is critical to maintain stringency of the pre-B cell receptor checkpoint and an important barrier against leukemic transformation.
Project description:Through their functional diversification, CD4+ T cells play key roles in both driving and constraining immune-mediated pathology. Transcription factors are critical in the generation and maintenance of cellular diversity and negative regulators antagonistic to alternate fates often act in conjunction with positive regulators to stabilize lineage specification1. Polymorphisms within the locus encoding a transcription factor BACH2 are associated with diverse immune-mediated diseases including asthma2, multiple sclerosis3, Crohn¹s disease4-5, coeliac disease6, vitiligo7 and type 1 diabetes8. A role for Bach2 in maintaining immune homeostasis, however, has not been established. Here, we define Bach2 as a broad regulator of immune activation that stabilizes immunoregulatory capacity while repressing the differentiation programmes of multiple effector lineages in CD4+ T cells. Bach2 was required for efficient formation of regulatory (Treg) cells and consequently for suppression of lethal inflammation in a manner that was Treg cell dependent. Assessment of the genome-wide function of Bach2, however, revealed that it represses genes associated with effector cell differentiation. Consequently, its absence during Treg polarization resulted in inappropriate diversion to effector lineages. In addition, Bach2 constrained full effector differentiation within Th1, Th2 and Th17 cell lineages. These findings identify Bach2 as a key regulator of CD4+ T-cell differentiation that prevents inflammatory disease by controlling the balance between tolerance and immunity. The role of Bach2t to regulate immune homeostasis was investigated by mapping DNA binding profiles of Bach2 in iTreg condition. The function of Bach2 was also evaluated by comparing transcriptome in WT and Bach2-deficient iTreg cells and further comparison was done with transcriptome in naive, Th1, Th2, and Th17 conditions.
Project description:Bach2 has been reported to regulate multiple immune cell development and function. Here we report that Bach2 is constitutively expressed in relatively immature NK subsets. Bach2 negatively regulates NK cell development and Bach2 deficiency results in NK cell with mature effector phenotype. Thus, Bach2 functions as a negative regulator of NK cell maturation and function.