Life Sciences Research for Lifelong Health

Publications

The Babraham Institute Publications database contains details of all publications resulting from our research groups and scientific services.

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Title / Authors / Details Open Access Download

Regulation of the Germinal Center Response.
Stebegg M, Kumar SD, Silva-Cayetano A, Fonseca VR, Linterman MA, Graca L

The germinal center (GC) is a specialized microstructure that forms in secondary lymphoid tissues, producing long-lived antibody secreting plasma cells and memory B cells, which can provide protection against reinfection. Within the GC, B cells undergo somatic mutation of the genes encoding their B cell receptors which, following successful selection, can lead to the emergence of B cell clones that bind antigen with high affinity. However, this mutation process can also be dangerous, as it can create autoreactive clones that can cause autoimmunity. Because of this, regulation of GC reactions is critical to ensure high affinity antibody production and to enforce self-tolerance by avoiding emergence of autoreactive B cell clones. A productive GC response requires the collaboration of multiple cell types. The stromal cell network orchestrates GC cell dynamics by controlling antigen delivery and cell trafficking. T follicular helper (Tfh) cells provide specialized help to GC B cells through cognate T-B cell interactions while Foxp3 T follicular regulatory (Tfr) cells are key mediators of GC regulation. However, regulation of GC responses is not a simple outcome of Tfh/Tfr balance, but also involves the contribution of other cell types to modulate the GC microenvironment and to avoid autoimmunity. Thus, the regulation of the GC is complex, and occurs at multiple levels. In this review we outline recent developments in the biology of cell subsets involved in the regulation of GC reactions, in both secondary lymphoid tissues, and Peyer's patches (PPs). We discuss the mechanisms which enable the generation of potent protective humoral immunity whilst GC-derived autoimmunity is avoided.

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Frontiers in immunology, 9, 1664-3224, 2469, 2018

PMID: 30410492

Open Access

Mice Deficient in Nucleoporin Nup210 Develop Peripheral T Cell Alterations.
van Nieuwenhuijze A, Burton O, Lemaitre P, Denton AE, Cascalho A, Goodchild RE, Malengier-Devlies B, Cauwe B, Linterman MA, Humblet-Baron S, Liston A

The nucleopore is an essential structure of the eukaryotic cell, regulating passage between the nucleus and cytoplasm. While individual functions of core nucleopore proteins have been identified, the role of other components, such as Nup210, are poorly defined. Here, through the use of an unbiased ENU mutagenesis screen for mutations effecting the peripheral T cell compartment, we identified a Nup210 mutation in a mouse strain with altered CD4/CD8 T cell ratios. Through the generation of Nup210 knockout mice we identified Nup210 as having a T cell-intrinsic function in the peripheral homeostasis of T cells. Remarkably, despite the deep evolutionary conservation of this key nucleopore complex member, no other major phenotypes developed, with viable and healthy knockout mice. These results identify Nup210 as an important nucleopore complex component for peripheral T cells, and raise further questions of why this nucleopore component shows deep evolutionary conservation despite seemingly redundant functions in most cell types.

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Frontiers in immunology, 9, 1664-3224, 2234, 2018

PMID: 30323813

Open Access

Genetic regulation of antibody responsiveness to immunization in substrains of BALB/c mice.
Poyntz HC, Jones A, Jauregui R, Young W, Gestin A, Mooney A, Lamiable O, Altermann E, Schmidt A, Gasser O, Weyrich L, Jolly CJ, Linterman MA, Le Gros G, Hawkins ED, Forbes-Blom E

Antibody-mediated immunity is highly protective against disease. The majority of current vaccines confer protection through humoral immunity, but there is high variability in responsiveness across populations. Identifying immune mechanisms that mediate low antibody responsiveness may provide potential strategies to boost vaccine efficacy. Here, we report diverse antibody responsiveness to unadjuvanted as well as adjuvanted immunization in substrains of BALB/c mice, resulting in high and low antibody response phenotypes. Furthermore, these antibody phenotypes were not affected by changes in environmental factors such as the gut microbiota composition. Antigen-specific B cells following immunization had a marked difference in capability to class-switch, resulting in perturbed IgG isotype antibody production. In vitro, a B cell intrinsic defect in the regulation of class-switch recombination was identified in mice with low IgG antibody production. Whole genome sequencing identified polymorphisms associated with the magnitude of antibody produced, and we propose candidate genes that may regulate isotype class-switching capability. This study highlights that mice sourced from different vendors can have significantly altered humoral immune response profiles, and provides a resource to interrogate genetic regulators of antibody responsiveness. Together these results further our understanding of immune heterogeneity and suggest additional research on the genetic influences of adjuvanted vaccine strategies is warranted for enhancing vaccine efficacy. This article is protected by copyright. All rights reserved.

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Immunology and cell biology, , 1440-1711, , 2018

PMID: 30152893

Paths to expansion: Differential requirements of IRF4 in CD8 T-cell expansion driven by antigen and homeostatic cytokines.
Lugli E, Brummelman J, Pilipow K, Roychoudhuri R

Interferon regulatory factor 4 (IRF4) regulates the clonal expansion and metabolic activity of activated T cells, but the precise context and mechanisms of its function in these processes are unclear. In this issue of the European Journal of Immunology, Miyakoda et al. [Eur. J. Immunol. 2018. 48: 1319-1328] show that IRF4 is required for activation and expansion of naïve and memory CD8 T cells driven by T-cell receptor (TCR) signaling, but dispensable for memory CD8 T-cell maintenance and homeostatic proliferation driven by homeostatic cytokines. The authors show that the function of IRF4 in CD8 T-cell expansion is partially dependent upon activation of the PI3K/AKT pathway through direct or indirect attenuation of PTEN expression. These data shed light upon the differential intracellular pathways required for naïve and memory T cells to respond to self-antigens and/or homeostatic cytokines, and highlight the potential translational relevance of these findings in the context of immune reconstitution such as following allogeneic stem cell transplantation.

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European journal of immunology, 48, 1521-4141, 1281-1284, 2018

PMID: 30133745

Transcriptome analysis of infected and bystander type 2 alveolar epithelial cells during influenza A virus infection reveals Wnt pathway downregulation.
Hancock AS, Stairiker CJ, Boesteanu AC, Monzón-Casanova E, Lukasiak S, Mueller YM, Stubbs AP, Garcia-Sastre A, Turner M, Katsikis PD

Influenza virus outbreaks remain a serious threat to public health. Greater understanding of how cells targeted by the virus respond to the infection can provide insight into the pathogenesis of disease. Here we examined the transcriptional profile of infected and uninfected type 2 alveolar epithelial cells (AEC) in the lungs of influenza virus infected mice. We show for the first time the unique gene expression profiles induced by the infection of AEC as well as the transcriptional response of uninfected bystander cells. This work allows us to distinguish the direct and indirect effects of infection at the cellular level. Transcriptome analysis revealed that although directly infected and bystander AEC from infected animals shared many transcriptome changes when compared to AEC from uninfected animals, directly infected cells compared to bystander uninfected AEC produce more interferon and express lower Wnt signaling associated transcripts, while concurrently expressing more transcripts associated with cell death pathways. The Wnt signaling pathway was downregulated in both infected AEC and infected human lung epithelial A549 cells. Wnt signaling did not affect type I and III interferon production by infected A549 cells. Our results reveal unique transcriptional changes that occur within infected AEC and show that influenza virus downregulates Wnt signaling. In light of recent findings that Wnt signaling is essential for lung epithelial stem cells, our findings reveal a mechanism by which influenza virus may affect host lung repair. Influenza virus infection remains a major public health problem. Utilizing a recombinant green fluorescent protein expressing influenza virus we compared the in vivo transcriptomes of directly infected and uninfected bystander cells from infected mouse lungs and discovered many pathways uniquely regulated in each population. The Wnt signaling pathway was downregulated in directly infected cells and was shown to affect virus but not interferon production. Our study is the first to discern the in vivo transcriptome changes induced by direct viral infection as compared to mere exposure to the lung inflammatory milieu and highlight the downregulation of Wnt signaling. This downregulation has important implications for understanding influenza virus pathogenesis as Wnt signaling is critical for lung epithelial stem cells and lung epithelial cell differentiation. Our findings reveal a mechanism by which influenza virus may affect host lung repair and suggest interventions that prevent damage or accelerate recovery of the lung.

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Journal of virology, , 1098-5514, , 2018

PMID: 30111569

PI3Kδ hyper-activation promotes development of B cells that exacerbate Streptococcus pneumoniae infection in an antibody-independent manner.
Stark AK, Chandra A, Chakraborty K, Alam R, Carbonaro V, Clark J, Sriskantharajah S, Bradley G, Richter AG, Banham-Hall E, Clatworthy MR, Nejentsev S, Hamblin JN, Hessel EM, Condliffe AM, Okkenhaug K

Streptococcus pneumoniae is a major cause of pneumonia and a leading cause of death world-wide. Antibody-mediated immune responses can confer protection against repeated exposure to S. pneumoniae, yet vaccines offer only partial protection. Patients with Activated PI3Kδ Syndrome (APDS) are highly susceptible to S. pneumoniae. We generated a conditional knock-in mouse model of this disease and identify a CD19B220 B cell subset that is induced by PI3Kδ signaling, resides in the lungs, and is correlated with increased susceptibility to S. pneumoniae during early phases of infection via an antibody-independent mechanism. We show that an inhaled PI3Kδ inhibitor improves survival rates following S. pneumoniae infection in wild-type mice and in mice with activated PI3Kδ. These results suggest that a subset of B cells in the lung can promote the severity of S. pneumoniae infection, representing a potential therapeutic target.

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Nature communications, 9, 2041-1723, 3174, 2018

PMID: 30093657

Open Access

Translational repression of pre-formed cytokine-encoding mRNA prevents chronic activation of memory T cells.
Salerno F, Engels S, van den Biggelaar M, van Alphen FPJ, Guislain A, Zhao W, Hodge DL, Bell SE, Medema JP, von Lindern M, Turner M, Young HA, Wolkers MC

Memory T cells are critical for the immune response to recurring infections. Their instantaneous reactivity to pathogens is empowered by the persistent expression of cytokine-encoding mRNAs. How the translation of proteins from pre-formed cytokine-encoding mRNAs is prevented in the absence of infection has remained unclear. Here we found that protein production in memory T cells was blocked via a 3' untranslated region (3' UTR)-mediated process. Germline deletion of AU-rich elements (AREs) in the Ifng-3' UTR led to chronic cytokine production in memory T cells. This aberrant protein production did not result from increased expression and/or half-life of the mRNA. Instead, AREs blocked the recruitment of cytokine-encoding mRNA to ribosomes; this block depended on the ARE-binding protein ZFP36L2. Thus, AREs mediate repression of translation in mouse and human memory T cells by preventing undesirable protein production from pre-formed cytokine-encoding mRNAs in the absence of infection.

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Nature immunology, , 1529-2916, , 2018

PMID: 29988089

Antigen phagocytosis by B cells is required for a potent humoral response.
Martínez-Riaño A, Bovolenta ER, Mendoza P, Oeste CL, Martín-Bermejo MJ, Bovolenta P, Turner M, Martínez-Martín N, Alarcón B

Successful vaccines rely on activating a functional humoral response that results from promoting a proper germinal center (GC) reaction. Key in this process is the activation of follicular B cells that need to acquire antigens and to present them to cognate CD4 T cells. Here, we report that follicular B cells can phagocytose large antigen-coated particles, a process thought to be exclusive of specialized antigen-presenting cells such as macrophages and dendritic cells. We show that antigen phagocytosis by B cells is BCR-driven and mechanistically dependent on the GTPase RhoG. Using mice, we show that phagocytosis of antigen by B cells is important for the development of a strong GC response and the generation of high-affinity class-switched antibodies. Importantly, we show that the potentiation effect of alum, a common vaccine adjuvant, requires direct phagocytosis of alum-antigen complexes by B cells. These data suggest a new avenue for vaccination approaches by aiming to deliver 1-3 μm size antigen particles to follicular B cells.

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EMBO reports, , 1469-3178, , 2018

PMID: 29987136

Open Access

The Calcineurin Inhibitor Tacrolimus Specifically Suppresses Human T Follicular Helper Cells.
Wallin EF, Hill DL, Linterman MA, Wood KJ

T follicular helper (Tfh) cells are key players in the production of antibody-producing B cells the germinal center reaction. Therapeutic strategies targeting Tfh cells are important where antibody formation is implicated in disease, such as transplant rejection and autoimmune diseases. We investigated the impact of the immunosuppressive agent tacrolimus on human Tfh cell differentiation and function in transplant recipients.

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Frontiers in immunology, 9, 1664-3224, 1184, 2018

PMID: 29904381

Open Access

Uncovering the Role of RNA-Binding Proteins in Gene Expression in the Immune System.
Díaz-Muñoz MD, Turner M

Fighting external pathogens requires an ever-changing immune system that relies on tight regulation of gene expression. Transcriptional control is the first step to build efficient responses while preventing immunodeficiencies and autoimmunity. Post-transcriptional regulation of RNA editing, location, stability, and translation are the other key steps for final gene expression, and they are all controlled by RNA-binding proteins (RBPs). Nowadays we have a deep understanding of how transcription factors control the immune system but recent evidences suggest that post-transcriptional regulation by RBPs is equally important for both development and activation of immune responses. Here, we review current knowledge about how post-transcriptional control by RBPs shapes our immune system and discuss the perspective of RBPs being the key players of a hidden immune cell epitranscriptome.

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Frontiers in immunology, 9, 1664-3224, 1094, 2018

PMID: 29875770

Open Access

Compensation between CSF1R+ macrophages and Foxp3+ Treg cells drives resistance to tumor immunotherapy.
Gyori D, Lim EL, Grant FM, Spensberger D, Roychoudhuri R, Shuttleworth SJ, Okkenhaug K, Stephens LR, Hawkins PT

Redundancy and compensation provide robustness to biological systems but may contribute to therapy resistance. Both tumor-associated macrophages (TAMs) and Foxp3+ regulatory T (Treg) cells promote tumor progression by limiting antitumor immunity. Here we show that genetic ablation of CSF1 in colorectal cancer cells reduces the influx of immunosuppressive CSF1R+ TAMs within tumors. This reduction in CSF1-dependent TAMs resulted in increased CD8+ T cell attack on tumors, but its effect on tumor growth was limited by a compensatory increase in Foxp3+ Treg cells. Similarly, disruption of Treg cell activity through their experimental ablation produced moderate effects on tumor growth and was associated with elevated numbers of CSF1R+ TAMs. Importantly, codepletion of CSF1R+ TAMs and Foxp3+ Treg cells resulted in an increased influx of CD8+ T cells, augmentation of their function, and a synergistic reduction in tumor growth. Further, inhibition of Treg cell activity either through systemic pharmacological blockade of PI3Kδ, or its genetic inactivation within Foxp3+ Treg cells, sensitized previously unresponsive solid tumors to CSF1R+ TAM depletion and enhanced the effect of CSF1R blockade. These findings identify CSF1R+ TAMs and PI3Kδ-driven Foxp3+ Treg cells as the dominant compensatory cellular components of the immunosuppressive tumor microenvironment, with implications for the design of combinatorial immunotherapies.

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JCI insight, 3, 2379-3708, , 2018

PMID: 29875321

Open Access

Phosphoinositide 3-kinase δ inhibition promotes antitumor responses but antagonizes checkpoint inhibitors.
Lim EL, Cugliandolo FM, Rosner DR, Gyori D, Roychoudhuri R, Okkenhaug K

Multiple modes of immunosuppression restrain immune function within tumors. We previously reported that phosphoinositide 3-kinase δ (PI3Kδ) inactivation in mice confers resistance to a range of tumor models by disrupting immunosuppression mediated by regulatory T cells (Tregs). The PI3Kδ inhibitor idelalisib has proven highly effective in the clinical treatment of chronic lymphocytic leukemia and the potential to extend the use of PI3Kδ inhibitors to nonhematological cancers is being evaluated. In this work, we demonstrate that the antitumor effect of PI3Kδ inactivation is primarily mediated through the disruption of Treg function, and correlates with tumor dependence on Treg immunosuppression. Compared with Treg-specific PI3Kδ deletion, systemic PI3Kδ inactivation is less effective at conferring resistance to tumors. We show that PI3Kδ deficiency impairs the maturation and reduces the capacity of CD8+ cytotoxic T lymphocytes (CTLs) to kill tumor cells in vitro, and to respond to tumor antigen-specific immunization in vivo. PI3Kδ inactivation antagonized the antitumor effects of tumor vaccines and checkpoint blockade therapies intended to boost the CD8+ T cell response. These findings provide insights into mechanisms by which PI3Kδ inhibition promotes antitumor immunity and demonstrate that the mechanism is distinct from that mediated by immune checkpoint blockade.

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JCI insight, 3, 2379-3708, , 2018

PMID: 29875319

Open Access

Bach2 Promotes B Cell Receptor-Induced Proliferation of B Lymphocytes and Represses Cyclin-Dependent Kinase Inhibitors.
Miura Y, Morooka M, Sax N, Roychoudhuri R, Itoh-Nakadai A, Brydun A, Funayama R, Nakayama K, Satomi S, Matsumoto M, Igarashi K, Muto A

BTB and CNC homology 2 (Bach2) is a transcriptional repressor that is required for the formation of the germinal center (GC) and reactions, including class switch recombination and somatic hypermutation of Ig genes in B cells, within the GC. Although BCR-induced proliferation is essential for GC reactions, the function of Bach2 in regulating B cell proliferation has not been elucidated. In this study, we demonstrate that Bach2 is required to sustain high levels of B cell proliferation in response to BCR signaling. Following BCR engagement in vitro, B cells from-deficient () mice showed lower incorporation of BrdU and reduced cell cycle progression compared with wild-type cells.B cells also underwent increased apoptosis, as evidenced by an elevated frequency of sub-Gcells and early apoptotic cells. Transcriptome analysis of BCR-engaged B cells frommice revealed reduced expression of the antiapoptotic geneencoding Bcl-xand elevated expression of cyclin-dependent kinase inhibitor (CKI) family genes, including,, andReconstitution of Bcl-xexpression partially rescued the proliferation defect ofB cells. Chromatin immunoprecipitation experiments showed that Bach2 bound to the CKI family genes, indicating that these genes are direct repression targets of Bach2. These findings identify Bach2 as a requisite factor for sustaining high levels of BCR-induced proliferation, survival, and cell cycle progression, and it promotes expression of Bcl-xand repression of CKI genes. BCR-induced proliferation defects may contribute to the impaired GC formation observed inmice.

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Journal of immunology (Baltimore, Md. : 1950), , 1550-6606, , 2018

PMID: 29540581

Epigenetic control of CD8+ T cell differentiation.
Henning AN, Roychoudhuri R, Restifo NP

Upon stimulation, small numbers of naive CD8+ T cells proliferate and differentiate into a variety of memory and effector cell types. CD8+ T cells can persist for years and kill tumour cells and virally infected cells. The functional and phenotypic changes that occur during CD8+ T cell differentiation are well characterized, but the epigenetic states that underlie these changes are incompletely understood. Here, we review the epigenetic processes that direct CD8+ T cell differentiation and function. We focus on epigenetic modification of DNA and associated histones at genes and their regulatory elements. We also describe structural changes in chromatin organization that affect gene expression. Finally, we examine the translational potential of epigenetic interventions to improve CD8+ T cell function in individuals with chronic infections and cancer.

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Nature reviews. Immunology, , 1474-1741, , 2018

PMID: 29379213

The RNA-binding protein PTBP1 is necessary for B cell selection in germinal centers.
Monzón-Casanova E, Screen M, Díaz-Muñoz MD, Coulson RMR, Bell SE, Lamers G, Solimena M, Smith CWJ, Turner M

Antibody affinity maturation occurs in germinal centers (GCs), where B cells cycle between the light zone (LZ) and the dark zone. In the LZ, GC B cells bearing immunoglobulins with the highest affinity for antigen receive positive selection signals from helper T cells, which promotes their rapid proliferation. Here we found that the RNA-binding protein PTBP1 was needed for the progression of GC B cells through late S phase of the cell cycle and for affinity maturation. PTBP1 was required for proper expression of the c-MYC-dependent gene program induced in GC B cells receiving T cell help and directly regulated the alternative splicing and abundance of transcripts that are increased during positive selection to promote proliferation.

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Nature immunology, , 1529-2916, , 2018

PMID: 29358707

PI3K induces B-cell development and regulates B cell identity.
Abdelrasoul H, Werner M, Setz CS, Okkenhaug K, Jumaa H

Phosphoinositide-3 kinase (PI3K) signaling is important for the survival of numerous cell types and class IA of PI3K is specifically required for the development of B cells but not for T cell development. Here, we show that class IA PI3K-mediated signals induce the expression of the transcription factor Pax5, which plays a central role in B cell commitment and differentiation by activating the expression of central B cell-specific signaling proteins such as SLP-65 and CD19. Defective class IA PI3K function leads to reduction in Pax5 expression and prevents B cell development beyond the stage expressing the precursor B cell receptor (pre-BCR). Investigating the mechanism of PI3K-induced Pax5 expression revealed that it involves a network of transcription factors including FoxO1 and Irf4 that directly binds to the Pax5 gene. Together, our results suggest that PI3K signaling links survival and differentiation of developing B cells with B cell identity and that decreased PI3K activity in pre-B cells results in reduced Pax5 expression and lineage plasticity.

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Scientific reports, 8, 2045-2322, 1327, 2018

PMID: 29358580

Open Access

RNA-binding proteins control gene expression and cell fate in the immune system.
Turner M, Díaz-Muñoz MD

RNA-binding proteins (RBPs) are essential for the development and function of the immune system. They interact dynamically with RNA to control its biogenesis and turnover by transcription-dependent and transcription-independent mechanisms. In this Review, we discuss the molecular mechanisms by which RBPs allow gene expression changes to occur at different speeds and to varying degrees, and which RBPs regulate the diversity of the transcriptome and proteome. These proteins are nodes for integration of transcriptional and signaling networks and are intimately linked to intermediary metabolism. They are essential components of regulatory feedback mechanisms that maintain immune tolerance and limit inflammation. The role of RBPs in malignancy and autoimmunity has led to their emergence as targets for the development of new therapeutic modalities.

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Nature immunology, , 1529-2916, , 2018

PMID: 29348497

Regulatory T Cell Migration Is Dependent on Glucokinase-Mediated Glycolysis.
Kishore M, Cheung KCP, Fu H, Bonacina F, Wang G, Coe D, Ward EJ, Colamatteo A, Jangani M, Baragetti A, Matarese G, Smith DM, Haas R, Mauro C, Wraith DC, Okkenhaug K, Catapano AL, De Rosa V, Norata GD, Marelli-Berg FM

Migration of activated regulatory T (Treg) cells to inflamed tissue is crucial for their immune-modulatory function. While metabolic reprogramming during Treg cell differentiation has been extensively studied, the bioenergetics of Treg cell trafficking remains undefined. We have investigated the metabolic demands of migrating Treg cells in vitro and in vivo. We show that glycolysis was instrumental for their migration and was initiated by pro-migratory stimuli via a PI3K-mTORC2-mediated pathway culminating in induction of the enzyme glucokinase (GCK). Subsequently, GCK promoted cytoskeletal rearrangements by associating with actin. Treg cells lacking this pathway were functionally suppressive but failed to migrate to skin allografts and inhibit rejection. Similarly, human carriers of a loss-of-function GCK regulatory protein gene-leading to increased GCK activity-had reduced numbers of circulating Treg cells. These cells displayed enhanced migratory activity but similar suppressive function, while conventional T cells were unaffected. Thus, GCK-dependent glycolysis regulates Treg cell migration.

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Immunity, 47, 1097-4180, 875-889.e10, 2017

PMID: 29166588

Open Access

TFR cells trump autoimmune antibody responses to limit sedition.
Linterman MA, Toellner KM

Nature immunology, 18, 1529-2916, 1185-1186, 2017

PMID: 29044242

Tia1 dependent regulation of mRNA subcellular location and translation controls p53 expression in B cells.
Díaz-Muñoz MD, Kiselev VY, Novère NL, Curk T, Ule J, Turner M

Post-transcriptional regulation of cellular mRNA is essential for protein synthesis. Here we describe the importance of mRNA translational repression and mRNA subcellular location for protein expression during B lymphocyte activation and the DNA damage response. Cytoplasmic RNA granules are formed upon cell activation with mitogens, including stress granules that contain the RNA binding protein Tia1. Tia1 binds to a subset of transcripts involved in cell stress, including p53 mRNA, and controls translational silencing and RNA granule localization. DNA damage promotes mRNA relocation and translation in part due to dissociation of Tia1 from its mRNA targets. Upon DNA damage, p53 mRNA is released from stress granules and associates with polyribosomes to increase protein synthesis in a CAP-independent manner. Global analysis of cellular mRNA abundance and translation indicates that this is an extended ATM-dependent mechanism to increase protein expression of key modulators of the DNA damage response.Sequestering mRNA in cytoplasmic stress granules is a mechanism for translational repression. Here the authors find that p53 mRNA, present in stress granules in activated B lymphocytes, is released upon DNA damage and is translated in a CAP-independent manner.

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Nature communications, 8, 2041-1723, 530, 2017

PMID: 28904350

Open Access

RNA-binding protein ZFP36L1 maintains posttranscriptional regulation of bile acid metabolism.
Tarling EJ, Clifford BL, Cheng J, Morand P, Cheng A, Lester E, Sallam T, Turner M, de Aguiar Vallim TQ

Bile acids function not only as detergents that facilitate lipid absorption but also as signaling molecules that activate the nuclear receptor farnesoid X receptor (FXR). FXR agonists are currently being evaluated as therapeutic agents for a number of hepatic diseases due to their lipid-lowering and antiinflammatory properties. FXR is also essential for maintaining bile acid homeostasis and prevents the accumulation of bile acids. Elevated bile acids activate FXR, which in turn switches off bile acid synthesis by reducing the mRNA levels of bile acid synthesis genes, including cholesterol 7α-hydroxylase (Cyp7a1). Here, we show that FXR activation triggers a rapid posttranscriptional mechanism to degrade Cyp7a1 mRNA. We identified the RNA-binding protein Zfp36l1 as an FXR target gene and determined that gain and loss of function of ZFP36L1 reciprocally regulate Cyp7a1 mRNA and bile acid levels in vivo. Moreover, we found that mice lacking hepatic ZFP36L1 were protected from diet-induced obesity and steatosis. The reduced adiposity and antisteatotic effects observed in ZFP36L1-deficient mice were accompanied by impaired lipid absorption that was consistent with altered bile acid metabolism. Thus, the ZFP36L1-dependent regulation of bile acid metabolism is an important metabolic contributor to obesity and hepatosteatosis.

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The Journal of clinical investigation, , 1558-8238, , 2017

PMID: 28891815

Open Access

Chromosome contacts in activated T cells identify autoimmune disease candidate genes.
Burren OS, Rubio García A, Javierre BM, Rainbow DB, Cairns J, Cooper NJ, Lambourne JJ, Schofield E, Castro Dopico X, Ferreira RC, Coulson R, Burden F, Rowlston SP, Downes K, Wingett SW, Frontini M, Ouwehand WH, Fraser P, Spivakov M, Todd JA, Wicker LS, Cutler AJ, Wallace C

Autoimmune disease-associated variants are preferentially found in regulatory regions in immune cells, particularly CD4(+) T cells. Linking such regulatory regions to gene promoters in disease-relevant cell contexts facilitates identification of candidate disease genes.

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Genome biology, 18, 1474-760X, 165, 2017

PMID: 28870212

Open Access

Human blood Tfr cells are indicators of ongoing humoral activity not fully licensed with suppressive function.
Fonseca VR, Agua-Doce A, Maceiras AR, Pierson W, Ribeiro F, Romão VC, Pires AR, da Silva SL, Fonseca JE, Sousa AE, Linterman MA, Graca L

Germinal center (GC) responses are controlled by T follicular helper (Tfh) and T follicular regulatory (Tfr) cells and are crucial for the generation of high-affinity antibodies. Although the biology of human circulating and tissue Tfh cells has been established, the relationship between blood and tissue Tfr cells defined as CXCR5(+)Foxp3(+) T cells remains elusive. We found that blood Tfr cells are increased in Sjögren syndrome, an autoimmune disease with ongoing GC reactions, especially in patients with high autoantibody titers, as well as in healthy individuals upon influenza vaccination. Although blood Tfr cells correlated with humoral responses, they lack full B cell-suppressive capacity, despite being able to suppress T cell proliferation. Blood Tfr cells have a naïve-like phenotype, although they are absent from human thymus or cord blood. We found that these cells were generated in peripheral lymphoid tissues before T-B interaction, as they are maintained in B cell-deficient patients. Therefore, blood CXCR5(+)Foxp3(+) T cells in human pathology indicate ongoing humoral activity but are not fully competent circulating Tfr cells.

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Science immunology, 2, 2470-9468, , 2017

PMID: 28802258

Cellular Stress in the Context of an Inflammatory Environment Supports TGF-β-Independent T Helper-17 Differentiation.
Brucklacher-Waldert V, Ferreira C, Stebegg M, Fesneau O, Innocentin S, Marie JC, Veldhoen M

T helper-17 (Th17) cells are associated with inflammatory disorders and cancer. We report that environmental conditions resulting in cellular stress, such as low oxygen, glucose, and isotonic stress, particularly enhance the generation of Th17 cells. Pharmacological inhibition of cell stress reduces Th17 cell differentiation while stress inducers enhance the development of Th17 cells. The cellular stress response results in Th17 cell development via sustained cytoplasmic calcium levels and, in part, XBP1 activity. Furthermore, in an inflammatory environment, conditions resulting in cell stress can bring about de novo Th17 cell differentiation, even in the absence of transforming growth factor β (TGF-β) signaling. In vivo, cell stress inhibition enhances resistance to Th17-mediated autoimmunity while stress-exposed T cells enhance disease severity. Adverse metabolic environments during inflammation provide a link between adaptive immunity and inflammation and may represent a risk factor for the development of chronic inflammatory conditions by facilitating Th17 cell differentiation.

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Cell reports, 19, 2211-1247, 2357-2370, 2017

PMID: 28614720

Open Access

Characterization of the B Cell Transcriptome Bound by RNA-Binding Proteins with iCLIP.
Díaz-Muñoz MD, Monzón-Casanova E, Turner M

Posttranscriptional regulation of gene expression shapes the B cell transcriptome and controls messenger RNA (mRNA) translation into protein. Recent reports have highlighted the importance of RNA binding proteins (RBPs) for mRNA splicing, subcellular location, stability, and translation during B lymphocyte development, activation, and differentiation. Here we describe individual-nucleotide resolution UV cross-linking and immunoprecipitation (iCLIP) in primary lymphocytes, a method that maps RNA-protein interactions in a genome-wide scale allowing mechanistic analysis of RBP function. We discuss the latest improvements in iCLIP technology and provide some examples of how integration of the RNA-protein interactome with other high-throughput mRNA sequencing methodologies uncovers the important role of RBP-mediated RNA regulation in key biological cell processes.

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Methods in molecular biology (Clifton, N.J.), 1623, 1940-6029, 159-179, 2017

PMID: 28589356