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  • B cells in rheumatoid arthritis synovial tissues encode focused antibody repertoires that include antibodies that stimulate macrophage TNF-? production. Clinical immunology (Orlando, Fla.) Elliott, S. E., Kongpachith, S., Lingampalli, N., Adamska, J. Z., Cannon, B. J., Blum, L. K., Bloom, M. S., Henkel, M., McGeachy, M. J., Moreland, L. W., Robinson, W. H. 2020: 108360

    Abstract

    Rheumatoid arthritis (RA) is characterized by the production of anti-citrullinated protein antibodies (ACPAs). To gain insights into the relationship between ACPA-expressing B cells in peripheral blood (PB) and synovial tissue (ST), we sequenced the B cell repertoire in paired PB and ST samples from five individuals with established, ACPA+ RA. Bioinformatics analysis of paired heavy and light chain sequences revealed clonally-related family members shared between PB and ST. ST-derived antibody repertoires exhibited reduced diversity and increased normalized clonal family size compared to PB-derived repertoires. Functional characterization showed that seven recombinant antibodies (rAbs) expressed from subject-derived sequences from both compartments bound citrullinated antigens and immune complexes (ICs) formed using one ST-derived rAb stimulated macrophage TNF-? production. Our findings demonstrate B cell trafficking between PB and ST in subjects with RA and ST repertoires include B cells that encode ACPA capable of forming ICs that stimulate cellular responses implicated in RA pathogenesis.

    View details for DOI 10.1016/j.clim.2020.108360

    View details for PubMedID 32035179

  • Antibody Repertoire Sequencing, Antigen Array Analysis, and Cytokine Profiling of Blood from Individuals at High-risk for RA Reveals Candidate Immunoglobulin V Genes, ACPA, and Cytokines That May Promote the Transition to Arthritis Iyer, R., Zia, A., Bloom, M., Nagpal, S., Rao, N., Baribaud, F., Vratsanos, G., Wang, W., Firestein, G., Boyle, D., Buckner, J., Holers, V., Deane, K., Robinson, W. WILEY. 2019
  • B cell checkpoints in autoimmune rheumatic diseases. Nature reviews. Rheumatology Rubin, S. J., Bloom, M. S., Robinson, W. H. 2019

    Abstract

    B cells have important functions in the pathogenesis of autoimmune diseases, including autoimmune rheumatic diseases. In addition to producing autoantibodies, B cells contribute to autoimmunity by serving as professional antigen-presenting cells (APCs), producing cytokines, and through additional mechanisms. B cell activation and effector functions are regulated byimmune checkpoints, including both activating and inhibitory checkpoint receptors that contribute to the regulation of B cell tolerance, activation, antigen presentation, T cell help, classswitching, antibody production and cytokine production. The various activating checkpoint receptors include B cell activating receptors that engage with cognate receptors on T cells or other cells, as well as Toll-like receptors that can provide dual stimulation to B cells via co-engagement with the B cell receptor. Furthermore, various inhibitory checkpoint receptors, including B cell inhibitory receptors, have important functions in regulating B cell development, activation and effector functions. Therapeutically targeting B cell checkpoints represents a promising strategy for the treatment of a variety of autoimmune rheumatic diseases.

    View details for PubMedID 30967621

  • IgE-mediated mast cell activation promotes inflammation and cartilage destruction in osteoarthritis. eLife Wang, Q., Lepus, C. M., Raghu, H., Reber, L. L., Tsai, M. M., Wong, H. H., von Kaeppler, E., Lingampalli, N., Bloom, M. S., Hu, N., Elliott, E. E., Oliviero, F., Punzi, L., Giori, N. J., Goodman, S. B., Chu, C. R., Sokolove, J., Fukuoka, Y., Schwartz, L. B., Galli, S. J., Robinson, W. H. 2019; 8

    Abstract

    Osteoarthritis is characterized by articular cartilage breakdown, and emerging evidence suggests that dysregulated innate immunity is likely involved. Here, we performed proteomic, transcriptomic, and electron microscopic analyses to demonstrate that mast cells are aberrantly activated in human and murine osteoarthritic joint tissues. Using genetic models of mast cell deficiency, we demonstrate that lack of mast cells attenuates osteoarthritis in mice. Using genetic and pharmacologic approaches, we show that the IgE/Fc?RI/Syk signaling axis is critical for the development of osteoarthritis. We find that mast cell-derived tryptase induces inflammation, chondrocyte apoptosis, and cartilage breakdown. Our findings demonstrate a central role for IgE-dependent mast cell activation in the pathogenesis of osteoarthritis, suggesting that targeting mast cells could provide therapeutic benefit in human osteoarthritis.This article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter).

    View details for PubMedID 31084709

  • Dysregulated integrin ?V?3 and CD47 signaling promotes joint inflammation, cartilage breakdown, and progression of osteoarthritis. JCI insight Wang, Q., Onuma, K., Liu, C., Wong, H., Bloom, M. S., Elliott, E. E., Cao, R. R., Hu, N., Lingampalli, N., Sharpe, O., Zhao, X., Sohn, D. H., Lepus, C. M., Sokolove, J., Mao, R., Cisar, C. T., Raghu, H., Chu, C. R., Giori, N. J., Willingham, S. B., Prohaska, S. S., Cheng, Z., Weissman, I. L., Robinson, W. H. 2019; 4 (18)

    Abstract

    Osteoarthritis (OA) is the leading cause of joint failure, yet the underlying mechanisms remain elusive, and no approved therapies that slow progression exist. Dysregulated integrin function was previously implicated in OA pathogenesis. However, the roles of integrin ?V?3 and the integrin-associated receptor CD47 in OA remain largely unknown. Here, transcriptomic and proteomic analyses of human and murine osteoarthritic tissues revealed dysregulated expression of ?V?3, CD47, and their ligands. Using genetically deficient mice and pharmacologic inhibitors, we showed that ?V?3, CD47, and the downstream signaling molecules Fyn and FAK are crucial to OA pathogenesis. MicroPET/CT imaging of a mouse model showed elevated ligand-binding capacities of integrin ?V?3 and CD47 in osteoarthritic joints. Further, our in vitro studies demonstrated that chondrocyte breakdown products, derived from articular cartilage of individuals with OA, induced ?V?3/CD47-dependent expression of inflammatory and degradative mediators, and revealed the downstream signaling network. Our findings identify a central role for dysregulated ?V?3 and CD47 signaling in OA pathogenesis and suggest that activation of ?V?3 and CD47 signaling in many articular cell types contributes to inflammation and joint destruction in OA. Thus, the data presented here provide a rationale for targeting ?V?3, CD47, and their signaling pathways as a disease-modifying therapy.

    View details for DOI 10.1172/jci.insight.128616

    View details for PubMedID 31534047

  • Cohesin Function in Cohesion, Condensation, and DNA Repair Is Regulated by Wpl1p via a Common Mechanism in Saccharomyces cerevisiae GENETICS Bloom, M. S., Koshland, D., Guacci, V. 2018; 208 (1): 111?24

    Abstract

    Cohesin tethers DNA to mediate sister chromatid cohesion, chromosome condensation, and DNA repair. How the cell regulates cohesin to perform these distinct functions remains to be elucidated. One cohesin regulator, Wpl1p, was characterized in Saccharomyces cerevisiae as a promoter of efficient cohesion and an inhibitor of condensation. Wpl1p is also required for resistance to DNA-damaging agents. Here, we provide evidence that Wpl1p promotes the timely repair of DNA damage induced during S-phase. Previous studies have indicated that Wpl1p destabilizes cohesin's binding to DNA by modulating the interface between the cohesin subunits Mcd1p and Smc3p Our results suggest that Wpl1p likely modulates this interface to regulate all of cohesin's biological functions. Furthermore, we show that Wpl1p regulates cohesion and condensation through the formation of a functional complex with another cohesin-associated factor, Pds5p In contrast, Wpl1p regulates DNA repair independently of its interaction with Pds5p Together, these results suggest that Wpl1p regulates distinct biological functions of cohesin by Pds5p-dependent and -independent modulation of the Smc3p/Mcd1p interface.

    View details for DOI 10.1534/genetics.117.300537

    View details for Web of Science ID 000419356300008

    View details for PubMedID 29158426

    View details for PubMedCentralID PMC5753852

  • A novel mechanism for the establishment of sister chromatid cohesion by the ECO1 acetyltransferase MOLECULAR BIOLOGY OF THE CELL Guacci, V., Stricklin, J., Bloom, M. S., Guo, X., Bhatter, M., Koshland, D. 2015; 26 (1): 117?33

    Abstract

    Cohesin complex mediates cohesion between sister chromatids, which promotes high-fidelity chromosome segregation. Eco1p acetylates the cohesin subunit Smc3p during S phase to establish cohesion. The current model posits that this Eco1p-mediated acetylation promotes establishment by abrogating the ability of Wpl1p to destabilize cohesin binding to chromosomes. Here we present data from budding yeast that is incompatible with this Wpl1p-centric model. Two independent in vivo assays show that a wpl1? fails to suppress cohesion defects of eco1? cells. Moreover, a wpl1? also fails to suppress cohesion defects engendered by blocking just the essential Eco1p acetylation sites on Smc3p (K112, K113). Thus removing WPL1 inhibition is insufficient for generating cohesion without ECO1 activity. To elucidate how ECO1 promotes cohesion, we conducted a genetic screen and identified a cohesion activator mutation in the SMC3 head domain (D1189H). Smc3-D1189H partially restores cohesion in eco1? wpl1? or eco1 mutant cells but robustly restores cohesion in cells blocked for Smc3p K112 K113 acetylation. These data support two important conclusions. First, acetylation of the K112 K113 region by Eco1p promotes cohesion establishment by altering Smc3p head function independent of its ability to antagonize Wpl1p. Second, Eco1p targets other than Smc3p K112 K113 are necessary for efficient establishment.

    View details for DOI 10.1091/mbc.E14-08-1268

    View details for Web of Science ID 000346923500010

    View details for PubMedID 25378582

    View details for PubMedCentralID PMC4279223

  • The Complete Spectrum of Yeast Chromosome Instability Genes Identifies Candidate CIN Cancer Genes and Functional Roles for ASTRA Complex Components PLOS GENETICS Stirling, P. C., Bloom, M. S., Solanki-Patil, T., Smith, S., Sipahimalani, P., Li, Z., Kofoed, M., Ben-Aroya, S., Myung, K., Hieter, P. 2011; 7 (4): e1002057

    Abstract

    Chromosome instability (CIN) is observed in most solid tumors and is linked to somatic mutations in genome integrity maintenance genes. The spectrum of mutations that cause CIN is only partly known and it is not possible to predict a priori all pathways whose disruption might lead to CIN. To address this issue, we generated a catalogue of CIN genes and pathways by screening ? 2,000 reduction-of-function alleles for 90% of essential genes in Saccharomyces cerevisiae. Integrating this with published CIN phenotypes for other yeast genes generated a systematic CIN gene dataset comprised of 692 genes. Enriched gene ontology terms defined cellular CIN pathways that, together with sequence orthologs, created a list of human CIN candidate genes, which we cross-referenced to published somatic mutation databases revealing hundreds of mutated CIN candidate genes. Characterization of some poorly characterized CIN genes revealed short telomeres in mutants of the ASTRA/TTT components TTI1 and ASA1. High-throughput phenotypic profiling links ASA1 to TTT (Tel2-Tti1-Tti2) complex function and to TORC1 signaling via Tor1p stability, consistent with the role of TTT in PI3-kinase related kinase biogenesis. The comprehensive CIN gene list presented here in principle comprises all conserved eukaryotic genome integrity pathways. Deriving human CIN candidate genes from the list allows direct cross-referencing with tumor mutational data and thus candidate mutations potentially driving CIN in tumors. Overall, the CIN gene spectrum reveals new chromosome biology and will help us to understand CIN phenotypes in human disease.

    View details for DOI 10.1371/journal.pgen.1002057

    View details for Web of Science ID 000289977000042

    View details for PubMedID 21552543

    View details for PubMedCentralID PMC3084213

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