Project description:DNMT3a is a de novo DNA methyltransferase expressed robustly after T cell activation that regulates plasticity of CD4+ T cell cytokine expression. Here we show that DNMT3a is critical for directing early CD8+ T cell effector and memory fate decisions. While effector function of DNMT3a knockout T cells is normal, they develop more memory precursor and fewer terminal effector cells in a T cell intrinsic manner compared to wild-type animals. Rather than increasing plasticity of differentiated effector CD8+ T cells, loss of DNMT3a biases differentiation of early effector cells into memory precursor cells. This is attributed in part to ineffective repression of Tcf1 expression in knockout T cells, as DNMT3a localizes to the Tcf7 promoter and catalyzes its de novo methylation in early effector WT CD8+ T cells. This data identifies DNMT3a as a crucial regulator of CD8+ early effector cell differentiation and effector versus memory fate decisions. Examination of global genomic DNA methylation by MBD-seq in naïve CD8 T cells and CD8 T cells 8 days post Vaccinia-Ova infection, comparing OT1 TCR-Tg CD8 T cells isolated from WT and T cell conditional DNMT3a KO mice.
Project description:The cell fate decisions between plasmablasts (PBs), germinal center B cells (GCBCs) and non-GC-derived early memory B cells (eMBCs) during early B cell activation determine the outcome of the immune responses to pathogens and vaccines. To characterize these poorly understood lineage choices, we dissected the early B cell responses to T-dependent antigen in mice by single-cell RNA-sequencing. Early after immunization, a homogenous population of activated precursors (APs) gave rise to a transient wave of PBs, followed a day later by the emergence of the first GCBCs, with the transcriptomes of both rapidly diverging from that of APs. The majority of APs started to withdraw from the cell cycle very early on and gave rise to eMBCs, a developmental transition that involved limited transcriptional changes. These events were controlled by antigen availability that rapidly declined soon after immunization, and provision of antigen excess interfered with the cell cycle exit of APs and induced a new wave of PBs. Fate mapping experiments revealed a prominent contribution of eMBCs to the overall MBC pool. Generation of the earliest GCBCs was tightly controlled by the transcriptional repressor Bhlhe40 in the absence of which this population was increased in numbers. Bhlhe40 also restrained in a cell intrinsic fashion the response of T follicular helper (TFH) cells, a specialized T helper cell subset required to mount the GC response. In B cells, Bhlhe40 executed its function in the first days after immunization by selectively restricting the generation of the earliest GCBCs but not of eMBCs or PBs. Conditional Bhlhe40 inactivation confirmed cell-autonomous functions of Bhlhe40 in both GCBCs and TFH cells, while the GC phenotype was further enhanced upon loss of Bhlhe40 in both cell types. This negative regulation of the GC reaction by Bhlhe40 was of crucial importance, as Bhlhe40-deficient mice with progressing age succumbed to a B cell lymphoma characterized by the accumulation of monoclonal GCBCs-like cells and polyclonal TFH cells in various tissues.
Project description:DNMT3a is a de novo DNA methyltransferase expressed robustly after T cell activation that regulates plasticity of CD4+ T cell cytokine expression. Here we show that DNMT3a is critical for directing early CD8+ T cell effector and memory fate decisions. While effector function of DNMT3a knockout T cells is normal, they develop more memory precursor and fewer terminal effector cells in a T cell intrinsic manner compared to wild-type animals. Rather than increasing plasticity of differentiated effector CD8+ T cells, loss of DNMT3a biases differentiation of early effector cells into memory precursor cells. This is attributed in part to ineffective repression of Tcf1 expression in knockout T cells, as DNMT3a localizes to the Tcf7 promoter and catalyzes its de novo methylation in early effector WT CD8+ T cells. This data identifies DNMT3a as a crucial regulator of CD8+ early effector cell differentiation and effector versus memory fate decisions.
Project description:DNA damage activates diverse cellular responses – either protective or deleterious –that ultimately promote or inhibit proliferation. How the distinct responses conferring crucial cell fate decisions are chosen is unclear. Using a systems approach, we demonstrate that the dynamic features of Atm dependent DNA double-strand break (DSB) signalling response dictate cellular outcome. Combining temporal phosphoproteome and nascent transcriptome analyses after low or high DNA-damage-load, we discovered that some responses, such as Tp53 activation, have an activation threshold and others arise independently of DNA-damage-load. Using DSB repair deficient cells, we show that persistent DSBs alter the kinetics – but not the amplitude – of Atm signalling. Thus, we demonstrate that pathway choices are dictated by the signalling dynamics and hence cell fate decisions are responsive to DNA-damage-load and repair capacity of the cells.
Project description:Naïve T cells respond to antigen stimulation by exiting from quiescence into clonal expansion and functional differentiation, but the control mechanism is elusive. Here we describe that Raptor/mTORC1-dependent metabolic reprogramming is a central determinant of this transitional process. Loss of Raptor abrogates T cell priming and Th2 cell differentiation, although Raptor function is less important for continuous proliferation of actively cycling cells. mTORC1 coordinates multiple metabolic programs in T cells including glycolysis, lipid synthesis and oxidative phosphorylation to mediate antigen-triggered exit from quiescence. mTORC1 further links glucose metabolism to the initiation of Th2 differentiation by orchestrating cytokine receptor expression and cytokine responsiveness. Activation of Raptor/mTORC1 integrates T cell receptor (TCR) and CD28 co-stimulatory signals in antigen-stimulated T cells. Our studies identify a Raptor/mTORC1-dependent pathway linking signal-dependent metabolic reprogramming to quiescence exit, and this in turn coordinates lymphocyte activation and fate decisions in adaptive immunity. We used microarrays to explore the gene expression profiles differentially expressed in CD4+ T-cells from wild-type (WT) and CD4(cre) x Raptor(fl/fl) mice before and after stimulation with anti CD3/CD28 antibodies.
Project description:Neural crest cells are embryonic progenitors that generate numerous cell types in vertebrates. With single cell analysis, we show that mouse trunk neural crest cells become biased toward neuronal lineages when they delaminate from the neural tube, whereas cranial neural crest cells acquire ectomesenchyme potential dependent on activation of the transcription factor Twist1. The choices that neural crest cells make to become sensory, glial, autonomic, or mesenchymal cells can be formalized as a series of sequential binary decisions. Each branch of the decision tree involves initial co-activation of bipotential properties followed by gradual shifts towards commitment. Competing fate programs are co-activated before cells acquire fate-specific phenotypic traits. Determination of a specific fate is achieved by increased synchronization of relevant programs and concurrent repression of competing fate programs.