Project description:Mechanistic knowledge about the homeostatic interplay between T cell-mediated immunity and gut microbiota is still limited. We aimed to investigate how restriction of the T-cell receptor (TCR) repertoire (VDJ region) may influence gut microbiota composition, causing tissue inflammation and disruption of peripheral immune tolerance. Based on the clinical observation of colonic inflammation in patients with partial RAG deficiency (pRD), we applied a multi-omics strategy to study a mouse model of hypomorphic Rag1 deficiency (Rag1 mutant mice) with spontaneous development of colitis.
Project description:The Mediator complex functions as a control center orchestrating diverse signalings, gene activities, and biological processes. However, how Mediator subunits determine distinct cell fates remains to be fully elucidated. Here, we show that Mediator MED23 controls the cell fate preference that directs differentiation into smooth muscle cells (SMCs) or adipocytes. Med23-deficiency facilitates SMC differentiation but represses adipocyte differentiation from the multipotent mesenchymal stem cells. Gene profiling revealed that the presence or absence of Med23 oppositely regulates two sets of genes: the RhoA/MAL-targeted cytoskeleton/SMC genes and the Ras/ELK1 targeted growth/adipocyte genes. Mechanistically, MED23 favors ELK1-SRF binding to SMC gene promoters for repression, whereas the lack of MED23 favors MAL-SRF binding to SMC gene promoters for activation. Remarkably, the effect of MED23 on SMC differentiation can be recapitulated in zebrafish embryogenesis. Collectively, our data demonstrate the dual, opposing roles for MED23 in regulating the cytoskeleton/SMC and growth/adipocyte gene programs, suggesting its “Ying-Yang” function in directing adipogenesis vs. SMC differentiation. Examination of SRF enrichment in sictrl and si23 10T1/2 cells
Project description:The bone marrow niche plays a critical role in controlling the fate of hematopoietic stem cells (HSCs) by integrating intrinsic and extrinsic signals. However, the molecular events in the HSC niche remain to be investigated. Here, we report that intercellular adhesion molecule-1 (ICAM-1) maintains HSC quiescence and repopulation capacity in the niche. ICAM-1-deficient mice (ICAM-1-/-) displayed significant expansion of phenotypic long-term HSCs with impaired quiescence, as well as favors myeloid cell expansion. ICAM-1-deficient HSCs presented normal reconstitution capacity during serial transplantation; however, reciprocal transplantation experiments showed that ICAM-1 deficiency in the niche impaired HSCs quiescence and repopulation capacity. In addition, ICAM-1 deletion caused failure to retain HSCs in the bone marrow and changed the expression profile of stroma cell-derived factors, possibly representing the mechanism for defective HSCs in ICAM-1-/- mice. Collectively, these observations identify ICAM-1 as a regulator in the bone marrow niche.
Project description:By their impact on nuclear organisation, enhancers are master regulators of cell fate. We thus developed double Emu-RAG-deficient, 3’RR-RAG-deficient mice and KOKI-RAG-deficient mice to investigate a potential transcriptional cross-talk between Emu and 3'RR enhancers at the pro-B cell stage.
Project description:V(D)J recombination initiated by recombination-activating gene (RAG) endonucleases is a crucial process for the generation of diversified antigen receptors of T and B lymphocytes but regarded dispensable for the generation of innate natural killer (NK) lymphocytes that lack clonotypic receptors. However, a fraction of human and murine NK cells derives from RAG-expressing progenitors, which have non-productive rearrangements within their Ig and TCR loci. An impact of V(D)J rearrangements on maturation and function of NK cells has been suggested by mouse and human models. We studied the impact of RAG expression ontogeny on NK cell maturation and function by using RAG-fate mapping reporter permanently labeling NK progenitors and mature NK cells.
Project description:Growth factor independence genes (Gfi1 and Gfi1b) repress recombination activating genes (Rag) transcription in developing B lymphocytes. Because all blood lineages originate from hematopoietic stem cells (HSCs) and different lineage progenitors have been shown to share transcription factor networks prior to cell fate commitment, we hypothesized that GFI family proteins may also play a role in repressing Rag transcription or a global lymphoid transcriptional program in other blood lineages. We tested the level of Rag transcription in various blood cells when Gfi1 and Gfi1b were deleted, and observed an upregulation of Rag expression in plasmacytoid dendritic cells (pDCs). Using microarray analysis, we observed that Gfi1 and Gfi1b regulate a broad spectrum of cellular processes in pDCs, but not a lymphoid specific transcriptional program. This study establishes a role for Gfi1 and Gfi1b in Rag regulation in a non-B lineage cell type
Project description:Growth factor independence genes (Gfi1 and Gfi1b) repress recombination activating genes (Rag) transcription in developing B lymphocytes. Because all blood lineages originate from hematopoietic stem cells (HSCs) and different lineage progenitors have been shown to share transcription factor networks prior to cell fate commitment, we hypothesized that GFI family proteins may also play a role in repressing Rag transcription or a global lymphoid transcriptional program in other blood lineages. We tested the level of Rag transcription in various blood cells when Gfi1 and Gfi1b were deleted, and observed an upregulation of Rag expression in plasmacytoid dendritic cells (pDCs). Using microarray analysis, we observed that Gfi1 and Gfi1b regulate a broad spectrum of cellular processes in pDCs, but not a lymphoid specific transcriptional program. This study establishes a role for Gfi1 and Gfi1b in Rag regulation in a non-B lineage cell type Gfi1f/f; Gfi1bf/f; ERCre bone marrow progenitors were untreated and treated with tamoxifen (4OHT) to delete floxed alleles during pDC differentiation in culture. Cells from three individual mouse constitute triplicates of untreated (-4OHT) and treated (+4OHT) conditions, corresponding to wildtype or knockout genotypes.
Project description:Most autoreactive B cells are normally counterselected during early B cell development. To determine whether Toll-like receptors (TLRs) regulate the removal of autoreactive B lymphocytes, we tested the reactivity of recombinant antibodies from single B cells isolated from patients deficient for IL-1R-associated kinase (IRAK)-4, myeloid differentiation factor 88 (MyD88) and UNC-93B. Indeed, all TLRs except TLR3 require IRAK-4 and MyD88 to signal and UNC-93B-deficient cells are unresponsive to TLR3, TLR7, TLR8 and TLR9. All patients suffered from defective central and peripheral B cell tolerance checkpoints resulting in the accumulation of large numbers of autoreactive mature naïve B cells in their blood. Hence, TLR7, TLR8, and TLR9 may prevent the recruitment of developing autoreactive B cells in healthy donors. Paradoxically, IRAK-4-, MyD88- and UNC-93B-deficient patients did not display autoreactive antibodies in their serum nor developed autoimmune diseases, suggesting that IRAK-4, MyD88 and UNC-93B pathway blockade may thwart autoimmunity in humans. Experiment Overall Design: RNA was extracted from 105-3.105 batch sorted new emigrant and mature naïve B cells isolated from donors using the Absolutely RNA microprep kit (Stratagene). 100-200 ng of RNA was obtained per sample, and the quality of the purified RNA was assessed by the Bioanalyzer from Agilent. Using the Ovation biotin system kit from Nugen, 30-50ng of RNA was amplified and labeled to produce cDNA. Labeled cDNA was hybridized on chips containing the whole human genome (Human Genome U133 2.0 from Affymetrix). Raw data from new emigrant (1 healthy donor) and mature naive (4 healthy donors) B cells were analyzed in order to determine the expression of some molecules involved in the TLR pathway in these B cell population in humans.
Project description:Regulatory T (Treg) cells are crucial for maintaining peripheral immune tolerance and preventing destructive autoreactive responses, but how heterogeneous Treg populations establish tolerant status remains unclear. Here, we found that Zinc finger protein 335 (Zfp335) is indispensable for the differentiation and maintenance of effector Treg (eTreg) population and immunological self-tolerance in neonates. Mice with Zfp335 deletion in Treg cells exhibit early-onset autoimmune disease with severe inflammation in multiple organs and unrestricted activation and expansion of conventional T cells. Zfp335-deficient Treg cells display dysfunctional and pathogenic features together with multiple defects in proliferation, survival and suppressive function. Importantly, our single-cell RNA sequencing (scRNA-seq) analyses reveal distinct Treg populations and that Zfp335 deficiency causes an almost complete loss of eTreg population along with significant accumulation of dysfunctional Treg populations. Mechanistically, Zfp335 controls both fate decision and homeostasis of eTreg cells by directly targeting genes associated with homeostasis and oxidation-fueled oxidative phosphorylation (OXPHOS) and PI3K-Akt-mTOR metabolic pathways. Our data establish the concept that Zfp335 serves as a checkpoint and safeguard for eTreg lineage commitment and maintenance.
Project description:An autoimmune B cell origin for childhood idiopathic nephrotic syndrome (INS) is predicted based on the efficacy of rituximab (RTX) at maintaining long-term remission from proteinuria. Knowledge regarding the nature of the culprit B cell response is very limited. In particular, no transcriptomics work has been performed to evaluate the B cell response in INS. Using single-cell RNA-sequencing (scRNAseq) on peripheral blood mononuclear cells (PBMC) isolated from four affected children with active INS and four age/sex-matched health controls (HC), we demonstrate that a B cell transcriptional program poised for effector functions represents the major immune perturbation in the blood of children with active INS. We show that this nephrotic B cell signature is conferred by the engagement of memory B cells through an extrafollicular developmental route defined by expression of the interfollicular-homing gene GPR183 and the expansion of atypical B cells and marginal zone-like B cells. Moreover, we show that genes involved in APRIL signaling, which promotes extrafollicular antibody-secreting cell development, were substantially upregulated in B cells, monocytes, and dendritic cells from INS children. Collectively, our study provides evidence for an extrafollicular origin for humoral immunity in active INS.