Project description:DZ (B220+ IgDlo GL-7+ CD95+CXCR4+CD86lo) or LZ (B220+ IgDlo GL-7+ CD95+CXCR4loCD86+) GC B cells were sorted from male Sle1.yaa lupus mice at 2,4,6 months of age. RNA-seq was employed to assess transcriptional changes in the different GC B cell subsets throughout course of disease.
Project description:Analysis of DZ and LZ compartments in the germinal center of WT and SykY317F mice revealed that Syk degradation regulates the gene expression in the light zone compartment.
Project description:The pathways regulating the formation of the germinal center (GC) dark- (DZ) and light- (LZ) zones are unknown. We show that FOXO1 expression is restricted to the GC DZ and is required for DZ formation, since its absence in mice leads to the complete loss of DZ gene programs and the formation of LZ-only GCs. FOXO1-negative GC B-cells display normal somatic hypermutation, but defective affinity maturation and class switch recombination. The function of FOXO1 in sustaining the DZ program involves the transactivation of the chemokine receptor CXCR4, and the cooperation with BCL6 in the trans-repression of genes involved in immune activation, DNA-repair and plasma cell differentiation. These results have also implications for understanding the role of FOXO1 mutations in lymphomagenesis. We used microarrays to determine the consequences of FOXO1 deletion in the GC B cell comparment, and correlate these data with phenotypic changes
Project description:The pathways regulating the formation of the germinal center (GC) dark- (DZ) and light- (LZ) zones are unknown. We show that FOXO1 expression is restricted to the GC DZ and is required for DZ formation, since its absence in mice leads to the complete loss of DZ gene programs and the formation of LZ-only GCs. FOXO1-negative GC B-cells display normal somatic hypermutation, but defective affinity maturation and class switch recombination. The function of FOXO1 in sustaining the DZ program involves the transactivation of the chemokine receptor CXCR4, and the cooperation with BCL6 in the trans-repression of genes involved in immune activation, DNA-repair and plasma cell differentiation. These results have also implications for understanding the role of FOXO1 mutations in lymphomagenesis. We used microarrays to determine the consequences of FOXO1 deletion in the GC B cell comparment, and correlate these data with phenotypic changes GC B cell subpopulations were collected by Fluorescence Activated Cell Sorting (FACS) from B cell enriched fractions of splenic mononuclear cell pools (12 days after SRBC immunization). 20ng of total RNA (RIN>9) for each sample was used as a template for linear cDNA amplification (Ovation RNA amplification Kit, NuGen). cDNA was labeled using the Encore Biotin Labeling Kit (NuGen) and hybridized to Affymetrix Mouse 430.2 gene expression arrays
Project description:Germinal centers (GCs), sites of antibody affinity maturation, are organized into dark (DZ) and light (LZ) zones. Here, we uncovered a B cell intrinsic role for STAT3 in GC DZ and LZ organization. Altered zonal organization of STAT3-deficient GCs dampened GC output of long-lived plasma cells (LL-PCs) but increased memory B cells (MBCs). Tfh-GC B cell interaction drive STAT3 tyrosine 705 and serine 727 phosphorylation in LZ B cells, facilitating their recycling into the DZ. An inducible system confirmed STAT3 is not involved in initiating or maintaining the GC but sustains GC zonal organization by regulating GC B cell recycling. RNAseq and ChIPseq analysis identified genes regulated by STAT3 that are critical for LZ cell recycling and transiting through the DZ proliferation and differentiation phases of the DZ. Thus, STAT3 signaling in B cells controls GC zone organization and recycling, and GC egress of LL-PCs, but negatively regulates MBC output.
Project description:Germinal centers (GCs), sites of antibody affinity maturation, are organized into dark (DZ) and light (LZ) zones. Here, we uncovered a B cell intrinsic role for STAT3 in GC DZ and LZ organization. Altered zonal organization of STAT3-deficient GCs dampened GC output of long- lived plasma cells (LL-PCs) but increased memory B cells (MBCs). Tfh-GC B cell interaction drive STAT3 tyrosine 705 and serine 727 phosphorylation in LZ B cells, facilitating their recycling into the DZ. An inducible system confirmed STAT3 is not involved in initiating or maintaining the GC but sustains GC zonal organization by regulating GC B cell recycling. RNAseq and ChIPseq analysis identified genes regulated by STAT3 that are critical for LZ cell recycling and transiting through the DZ proliferation and differentiation phases of the DZ. Thus, STAT3 signaling in B cells controls GC zone organization and recycling, and GC egress of LL- PCs, but negatively regulates MBC output.
Project description:Gene expression analysis performed on FACS sort purified GC LZ and DZ cells of either high and low affinity to identify unique gene signatures. In order to reveal differences between LZ and DZ independent of affinity, we compared a DZ data set (consisting of high and low affinity samples), to a LZ data set (consisting of high and low affinity samples). Analysis revealed distrinct transcription patterns.
Project description:Germinal center (GC) B cells cycle between two states, the light zone (LZ) and the dark zone (DZ), and in the latter they proliferate and hypermutate their immunoglobulin genes. How this functional transition takes place is still controversial. In this study, we demonstrate that ablation of Foxo1 after GC development led to the loss of the DZ GC B cells and disruption of the GC architecture. Mechanistically, even upon provision of adequate T cell help, Foxo1-deficient GC B cells showed less proliferative expansion than controls. Moreover, we found that the transcription factor BATF was transiently induced in LZ GC B cells in a Foxo1-dependent manner and that deletion of BATF similarly led to GC disruption. Thus, our results are consistent with a model where the switch from the LZ to the DZ is triggered after receipt of T cell help, and suggest that Foxo1-mediated BATF up-regulation is at least partly involved in this switch.
Project description:Within germinal centers (GCs), complex and highly orchestrated molecular programs must balance proliferation, somatic hypermutation (SHM), class switch recombination (CSR) and selection to both provide effective humoral immunity and to protect against genomic instability and neoplastic transformation. In contrast to this complexity, GC B cells are canonically divided into two principal populations, dark zone (DZ) and light zone (LZ) cells. We now demonstrate that following selection in the LZ, B cells migrate to microniches within the canonical DZ that are sites of ongoing cell division. These proliferating DZ (DZp) cells then transit into the larger DZ to become differentiating DZ (DZd) cells before re-entering the LZ. Multidimensional analysis revealed distinct molecular programs in each population commensurate with observed compartmentization of non-compatable functions. These data provide a new three cell zone model that both orders critical GC functions and reveals essential molecular programs of humoral adaptive immunity.
Project description:Germinal centers (GC) arise within B cell follicles upon antigenic challenge. In the dark zones (DZ) of GCs, B cells proliferate and hypermutate their immunoglobulin genes, and mutants with increased affinity are positively selected in the light zone (LZ) to either differentiate into plasma and memory cells, or re-enter the DZ for further refinement. However, the molecular circuits governing GC positive selection are not known. Here, we show that the GC reaction requires the biphasic regulation of c-MYC expression, involving its transient induction during early GC commitment, its repression by BCL6 in DZ B cells, and its re-induction in a subpopulation of positively selected LZ B cells destined to DZ re-entry. Accordingly, acute disruption of MYC function in vivo leads to GC collapse, indicating an essential role in GC physiology. These results have implications for our understanding of GC selection and the role of MYC deregulation in B cell lymphomas. We used microarrays to determine the global gene expression programs that distinguish MYC+ GC B cells from their MYC- negative counterparts.