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Open Access Publications from the University of California

Scholarly Works (7 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2018)

MicroRNA-146a has been characterized as a negative regulator of the NFκB and interferon signaling pathways in myeloid and/or T cells, but its function in B cells is not well defined. Because microRNAs often target different pathways in immune cells, this proposal serves to fill this gap in knowledge in B cells to better understand its dysregulation in human autoimmune diseases, specifically systemic lupus erythematosus.

We use miR-146a knockout mice (KO) to examine the effects of miR-146a on B cell development. We found that KO mice show a T cell-independent defect in marginal zone B (MZ) cell development, although all other immature, transitional B cells, follicular cells, and B1 cells were increased. This MZ developmental defect is likely cell intrinsic, as bone marrow progenitors were not different between KO and WT, and there were no differences in splenic immune cell egress. We then used high-throughput sequencing to compare the various spleen B cell subsets stage-specific transcriptomes, and determined the MZ cell differentiation was impaired due to decreases in the Notch2 signaling pathway. These findings show an important role of miR-146a regulating normal peripheral B cell development.

We then examine the role of miR-146a on B cell function. We utilize in vitro isolated B cell assays to better characterize KO B cell characteristics compared to WT when stimulated with various T-independent (TI) or T-dependent (TD) antigens. We show that KO cells have higher proliferative capacity and activation markers in vitro than WT, in particular to TI antigen stimulation. We then perform immunization experiments with TI and TD antigens. Similar to our in vitro studies, KOs show higher primary immunization responses to TI antigen immunization, although not memory responses. We then use molecular genetics to define mechanisms of miR-146a target repression in B cells, utilizing RNA-Seq and genetic complementation studies currently underway. The combination of cellular and molecular studies will allow for better characterization of miR-146a in B cells.

Finally, we end with a human application using a large, longitudinal systemic lupus cohort and discuss the importance of exploring microRNAs in human autoimmune research as promising biomarkers in an era of precision medicine.

    Cover page: MicroRNA-146a Regulates B Cell Development, Function, and Autoimmunity
    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2016)
    Abstract B cell development in bone marrow is followed by specification into spleen subsets, including marginal zone (MZ) cells. MZ require elaboration of distinct gene expression programs for development. Given their role in gene regulation, its not surprising that microRNAs (miRNAs) influence cell development. Recent work demonstrated that deficiency of NF-κB feedback regulator, Mir146 (miR-146a), led to a range of hematopoietic phenotypes, but B cells have not been extensively characterized. Here, we found miR-146a deficient mice demonstrate a reduction in MZ B cells, likely from a T cell independent developmental block. Utilizing comparative analysis of developmental stage-specific transcriptomes, we show MZ cell differentiation was impaired due to decreases in Notch2 signaling. Further, we discovered that the cell-fate regulatory protein, Numb, is a direct target of miR-146a, and its derepression in miR-146a deficient B cells underlies the decreases in Notch2. Our studies reveal miR-146a-dependent B cell phenotypes regulated by the Numb-Notch2 pathway. Disclosures No relevant conflicts of interest to declare.
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2017)
      B-cell development in the bone marrow is followed by specification into functional subsets in the spleen, including marginal zone (MZ) B-cells. MZ B-cells are classically characterized by T-independent antigenic responses and require the elaboration of distinct gene expression programs for development. Given their role in gene regulation, it is not surprising that microRNAs are important factors in B-cell development. Recent work demonstrated that deficiency of the NFκB feedback regulator, miR-146a, led to a range of hematopoietic phenotypes, but B-cell phenotypes have not been extensively characterized. Here, we found that miR-146a-deficient mice demonstrate a reduction in MZ B-cells, likely from a developmental block. Utilizing high-throughput sequencing and comparative analysis of developmental stage-specific transcriptomes, we determined that MZ cell differentiation was impaired due to decreases in Notch2 signaling. Our studies reveal miR-146a-dependent B-cell phenotypes and highlight the complex role of miR-146a in the hematopoietic system.
        Cover page: Regulation of Marginal Zone B-Cell Differentiation by MicroRNA-146a
        • Article
        • Peer Reviewed
        UCLA Previously Published Works (2022)
        The microRNA, miR-146a, is a negative feedback regulator of the central immune transcription factor, nuclear factor kappa B (NFkB). MiR-146a plays important roles in the immune system, and miR-146a deficient mice show a complex phenotype with features of chronic inflammation and autoimmune disease. In this study, we examined the role of miR-146a in extrafollicular B-cell responses, finding that miR-146a suppresses cellular responses in vivo and in vitro. Gene expression profiling revealed that miR-146a-deficient B-cells showed upregulation of interferon pathway genes, including Traf6, a known miR-146a target. We next interrogated the role of TRAF6 in these B-cell responses, finding that TRAF6 is required for proliferation by genetic and pharmacologic inhibition. Together, our findings demonstrate a novel role for miR-146a and TRAF6 in the extrafollicular B-cell responses, which have recently been tied to autoimmune disease pathogenesis. Our work highlights the pathogenetic role of miR-146a and the potential of pharmacologic inhibition of TRAF6 in autoimmune diseases in which miR-146a is deregulated.
          • Article
          • Peer Reviewed
          UC Riverside Previously Published Works (2008)
          Most autoimmune diseases are more common in women than in men. This may be caused by differences in sex hormones, sex chromosomes, or both. In this study, we determined if there was a contribution of sex chromosomes to sex differences in susceptibility to two immunologically distinct disease models, experimental autoimmune encephalomyelitis (EAE) and pristane-induced lupus. Transgenic SJL mice were created to permit a comparison between XX and XY within a common gonadal type. Mice of the XX sex chromosome complement, as compared with XY, demonstrated greater susceptibility to both EAE and lupus. This is the first evidence that the XX sex chromosome complement, as compared with XY, confers greater susceptibility to autoimmune disease.
            Cover page: A role for sex chromosome complement in the female bias in autoimmune disease
            • Article
            • Peer Reviewed
            UCLA Previously Published Works (2015)
            Systemic autoimmune diseases such as lupus affect multiple organs, usually in a diverse fashion where only certain organs are affected in individual patients. It is unclear whether the "local" immune cells play a role in regulating tissue specificity in relation to disease heterogeneity in systemic autoimmune diseases. In this study, we used skin as a model to determine the role of tissue-resident dendritic cells (DCs) in local and systemic involvement within a systemic lupus disease model. Skin-resident DCs, namely, Langerhans cells (LCs), have been implicated in regulating tolerance or autoimmunity using elegant transgenic models, however, their role in local versus systemic immune regulation is unknown. We demonstrate that although lymphocytes from skin-draining lymph nodes of autoimmune-prone MRL/MpJ-Fas(lpr/lp) (r) (MRL-lpr) mice react spontaneously to a physiological skin self-Ag desmoglein-3, epicutaneous applications of desmoglein-3 induced tolerance that is dependent on LCs. Inducible ablation of LCs in adult preclinical MRL-lpr and MRL/MpJ-Fas(+/+) mice resulted in increased autoantibodies against skin Ags and markedly accelerated lupus dermatitis with increased local macrophage infiltration, but had no effect on systemic autoantibodies such as anti-dsDNA Abs or disease in other organs such as kidneys, lung, and liver. Furthermore, skin-draining lymph nodes of LC-ablated MRL-lpr mice had significantly fewer CD4(+) T cells producing anti-inflammatory cytokine IL-10 than LC-intact controls. These results indicate that a skin-resident DC population regulates local tolerance in systemic lupus and emphasize the importance of the local immune milieu in preventing tissue-specific autoimmunity, yet have no effect on systemic autoimmunity.
              Cover page: Langerhans Cells Maintain Local Tissue Tolerance in a Model of Systemic Autoimmune Disease
              • Article
              • Peer Reviewed
              UCLA Previously Published Works (2023)
              Loss of function in the tumor suppressor gene TP53 is the most common alteration seen in human cancer. In mice, P53 deletion in all cells leads predominantly to the development of T-cell lymphomas, followed by B-cell lymphomas, sarcomas and teratomas. In order to dissect the role of P53 in the hematopoietic system, we generated and analyzed two different mouse models deficient for P53. A pan-hematopoietic P53 deletion mouse was created using Vav1-Cre based deletion; and a B-cell-specific deletion mouse was created using a CD19-Cre based deletion. The Vav1-P53CKO mice predominantly developed T-cell malignancies in younger mice, and myeloid malignancies in older mice. In T-cell malignancies, there was accelerated thymic cell maturation with overexpression of Notch1 and its downstream effectors. CD19-P53CKO mice developed marginal zone expansion in the spleen, followed by marginal zone lymphoma, some of which progressed to diffuse large B-cell lymphomas. Interestingly, marginal zone and diffuse large B-cell lymphomas had a unique gene expression signature characterized by activation of the PI3K pathway, compared with wild type marginal zone or follicular cells of the spleen. This study demonstrates lineage specific P53 deletion leading to distinct phenotypes secondary to unique gene expression programs set in motion.
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