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Metabolic dysfunction-associated steatohepatitis (MASH) is the progressive form of liver steatosis, the most common liver disease, and substantially increases the mortality rate. However, limited therapies are currently available to prevent MASH development. Identifying potential pharmacological treatments for the condition has been hampered by its heterogeneous and complex nature. Here, we identified a hepatic nonneuronal cholinergic signaling pathway required for metabolic adaptation to caloric overload. We found that cholinergic receptor nicotinic alpha 2 subunit (CHRNA2) is highly expressed in hepatocytes of mice and humans. Further, CHRNA2 is activated by a subpopulation of local acetylcholine-producing macrophages during MASH development. The activation of CHRNA2 coordinates defensive programs against a broad spectrum of MASH-related pathogenesis, including steatosis, inflammation, and fibrosis. Hepatocyte-specific loss of CHRNA2 signaling accelerates the disease onset in different MASH mouse models. Activation of this pathway via pharmacological inhibition of acetylcholine degradation protects against MASH development. Our study uncovers a hepatic nicotinic cholinergic receptor pathway that constitutes a cell-autonomous self-defense route against prolonged metabolic stress and holds therapeutic potential for combatting human MASH., Competing Interests: The authors declare no competing interests., (Copyright: © 2024 Jun et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.)

Bone fracture repair is a complex, multi-step process that involves communication between immune and stromal cells to coordinate the repair and regeneration of damaged tissue. In the US, 10% of all bone fractures do not heal properly without intervention, resulting in non-union. Complications from non-union fractures are physically and financially debilitating. We now appreciate the important role that immune cells play in tissue repair, and the necessity of the inflammatory response in initiating healing after skeletal trauma. The temporal dynamics of immune and stromal cell populations have been well characterized across the stages of fracture healing. Recent studies have begun to untangle the intricate mechanisms driving the immune response during normal or atypical, delayed healing. Various in vivo models of fracture healing, including genetic knockouts, as well as in vitro models of the fracture callus, have been implemented to enable experimental manipulation of the heterogeneous cellular environment. The goals of this review are to (1): summarize our current understanding of immune cell involvement in fracture healing (2); describe state-of-the art approaches to study inflammatory cells in fracture healing, including computational and in vitro models; and (3) identify gaps in our knowledge concerning immune-stromal crosstalk during bone healing., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Capobianco, Hankenson and Knights.)

Purpose of Review: The understanding of inflammation in osteoarthritis is rapidly evolving. This review highlights important basic science, mechanistic, and clinical findings since 2020 that underscore the current notion of osteoarthritis as an inflammatory disease., Recent Findings: There exists a disconnect between clinical radiographic findings and patient symptoms in osteoarthritis. Inflammation, in particular synovitis, has been put forward as a potential explanation for this disconnect. New findings have shed light on the temporal dynamics and activation states of joint-resident or systemically derived immune cell populations, notably macrophages, that participate in the inflammatory response. The intricate crosstalk in which they engage may underpin disparate pain and symptoms in patients, for instance during osteoarthritis flares. The role of biological and environmental factors such as exercise, age, and diet, have been the subject of recent studies for their protective or destructive roles in osteoarthritis inflammation. Despite these advances, no disease-modifying osteoarthritis treatments targeting inflammation have emerged., Summary: Osteoarthritis is a debilitating chronic disease that manifests with widely varying symptomatology. Inflammation is now appreciated as a key pathophysiological process in osteoarthritis, but there remain considerable gaps in our understanding of its role in disease progression and how best to target the inflammatory response for therapeutic interventions., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Eosinophils are granular leukocytes of the innate immune system that play important functions in host defense. Inappropriate activation of eosinophils can occur in pathologies such as asthma and esophagitis. However, eosinophils also reside within adipose tissue, where they play homeostatic roles and are important in the activation of thermogenic beige fat. Here we performed bulk RNA sequencing in mouse adipose tissue-resident eosinophils isolated from both subcutaneous and gonadal depots, for the first time, and compared gene expression to blood eosinophils. We found a predominantly conserved transcriptional landscape in eosinophils between adipose depots that is distinct from blood eosinophils in circulation. Through exploration of differentially expressed transcription factors and transcription factors with binding sites enriched in adipose-resident eosinophil genes, we identified KLF, CEBP, and Fos/Jun family members that may drive functional specialization of eosinophils in adipose tissue. These findings increase our understanding of tissue-specific eosinophil heterogeneity, with implications for targeting eosinophil function to treat metabolic disorders such as obesity., Competing Interests: Conflict of interest The authors declare no conflict of interest., (© The Author(s) 2023. Published by Oxford University Press on behalf of Society for Leukocyte Biology. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Objectives: Synovium is acutely affected following joint trauma and contributes to post-traumatic osteoarthritis (PTOA) progression. Little is known about discrete cell types and molecular mechanisms in PTOA synovium. We aimed to describe synovial cell populations and their dynamics in PTOA, with a focus on fibroblasts. We also sought to define mechanisms of synovial Wnt/β-catenin signalling, given its emerging importance in arthritis., Methods: We subjected mice to non-invasive anterior cruciate ligament rupture as a model of human joint injury. We performed single-cell RNA-sequencing to assess synovial cell populations, subjected Wnt-GFP reporter mice to joint injury to study Wnt-active cells, and performed intra-articular injections of the Wnt agonist R-spondin 2 (Rspo2) to assess whether gain of function induced pathologies characteristic of PTOA. Lastly, we used cultured fibroblasts, macrophages and chondrocytes to study how Rspo2 orchestrates crosstalk between joint cell types., Results: We uncovered seven distinct functional subsets of synovial fibroblasts in healthy and injured synovium, and defined their temporal dynamics in early and established PTOA. Wnt/β-catenin signalling was overactive in PTOA synovium, and Rspo2 was strongly induced after injury and secreted exclusively by Prg4 hi lining fibroblasts. Trajectory analyses predicted that Prg4 hi lining fibroblasts arise from a pool of Dpp4+ mesenchymal progenitors in synovium, with SOX5 identified as a potential regulator of this emergence. We also showed that Rspo2 orchestrated pathological crosstalk between synovial fibroblasts, macrophages and chondrocytes., Conclusions: Synovial fibroblasts assume distinct functional identities during PTOA in mice, and Prg4 hi lining fibroblasts secrete Rspo2 that may drive pathological joint crosstalk after injury., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Myeloid cells are central to homeostasis and immunity. Characterising in vitro myelopoiesis protocols is imperative for their use in research, immunotherapies, and understanding human myelopoiesis. Here, we generate a >470K cells molecular map of human induced pluripotent stem cells (iPSC) differentiation into macrophages. Integration with in vivo single-cell atlases shows in vitro differentiation recapitulates features of yolk sac hematopoiesis, before definitive hematopoietic stem cells (HSC) emerge. The diversity of myeloid cells generated, including mast cells and monocytes, suggests that HSC-independent hematopoiesis can produce multiple myeloid lineages. We uncover poorly described myeloid progenitors and conservation between in vivo and in vitro regulatory programs. Additionally, we develop a protocol to produce iPSC-derived dendritic cells (DC) resembling cDC2. Using CRISPR/Cas9 knock-outs, we validate the effects of key transcription factors in macrophage and DC ontogeny. This roadmap of myeloid differentiation is an important resource for investigating human fetal hematopoiesis and new therapeutic opportunities., (© 2022. The Author(s).)

Non-neuronal cholinergic signaling, mediated by acetylcholine, plays important roles in physiological processes including inflammation and immunity. Our group first discovered evidence of non-neuronal cholinergic circuitry in adipose tissue, whereby immune cells secrete acetylcholine to activate beige adipocytes during adaptive thermogenesis. Here, we reveal that macrophages are the cellular protagonists responsible for secreting acetylcholine to regulate thermogenic activation in subcutaneous fat, and we term these cells cholinergic adipose macrophages (ChAMs). An adaptive increase in ChAM abundance is evident following acute cold exposure, and macrophage-specific deletion of choline acetyltransferase (ChAT), the enzyme for acetylcholine biosynthesis, impairs the cold-induced thermogenic capacity of mice. Further, using pharmacological and genetic approaches, we show that ChAMs are regulated via adrenergic signaling, specifically through the β 2 adrenergic receptor. These findings demonstrate that macrophages are an essential adipose tissue source of acetylcholine for the regulation of adaptive thermogenesis, and may be useful for therapeutic targeting in metabolic diseases., (© 2021 The Authors.)

Objective: Joint injury-induced perturbations to the endocannabinoid system (ECS), a regulator of both inflammation and nociception, remain largely uncharacterized. We employed a mouse model of ACL rupture to assess alterations to nociception, inflammation, and the ECS while using in vitro models to determine whether CB2 agonism can mitigate inflammatory signaling in macrophages and fibroblast-like synoviocytes (FLS)., Design: Mice underwent noninvasive ACL rupture (ACLR) via tibial compression-based loading. Nociception was measured longitudinally using mechanical allodynia and knee hyperalgesia testing. Synovitis was assessed using histological scoring and histomorphometry. Gene and protein markers of inflammation were characterized in whole joints and synovium. Immunohistochemistry assessed injury-induced alterations to CB1+, CB2+, and F4/80+ cells in synovium. To assess whether CB2 agonism can inhibit pro-inflammatory macrophage polarization, murine bone marrow-derived macrophages (mBMDM) were stimulated with IL-1β or conditioned medium from IL-1β-treated FLS and treated with vehicle (DMSO), the CB2 agonist HU308, or cannabidiol (CBD). Macrophage polarization was assessed as the ratio of M1-associated (IL1b, MMP1b, and IL6) to M2-associated (IL10, IL4, and CD206) gene expression. Human FLS (hFLS) isolated from synovial tissue of OA patients were treated with vehicle (DMSO) or HU308 following TNF-α or IL-1β stimulation to assess inhibition of catabolic/inflammatory gene expression., Results: ACLR induces synovitis, progressively-worsening PTOA severity, and an immediate and sustained increase in both mechanical allodynia and knee hyperalgesia, which persist beyond the resolution of molecular inflammation. Enrichment of CB2, but not CB1, was observed in ACLR synovium at 3d, 14d, and 28d, and CB2 was found to be associated with F4/80 (+) cells, which are increased in number in ACLR synovium at all time points. The CB2 agonist HU308 strongly inhibited mBMDM M1-type polarization following stimulation with either IL-1β or conditioned medium from IL-1β-treated mFLS, which was characterized by reductions in Il1b, Mmp1b, and Il6 and increases in Cd206 gene expression. Cannabidiol similarly inhibited IL-1β-induced mBMDM M1 polarization via a reduction in Il1b and an increase in Cd206 and Il4 gene expression. Lastly, in OA hFLS, HU308 treatment inhibited IL-1β-induced CCL2, MMP1, MMP3, and IL6 expression and further inhibited TNF-α-induced CCL2, MMP1, and GMCSF expression, demonstrating human OA-relevant anti-inflammatory effects by targeting CB2., Conclusions: Joint injury perturbs the intra-articular ECS, characterized by an increase in synovial F4/80(+) cells, which express CB2, but not CB1. Targeting CB2 in murine macrophages and human FLS induced potent anti-inflammatory and anti-catabolic effects, which indicates that the CB2 receptor plays a key role in regulating inflammatory signaling in the two primary effector cells in the synovium. The intraarticular ECS is therefore a potential therapeutic target for blocking pathological inflammation in future disease-modifying PTOA treatments., (Copyright © 2021 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.)

Adipose tissue serves as the body's primary energy storage site; however, findings in recent decades have transformed our understanding of the multifaceted roles of this adaptable organ. The ability of adipose tissue to undergo energy expenditure through heat generation is termed adaptive thermogenesis, a process carried out by thermogenic adipocytes. Adipocytes are the primary parenchymal cell type in adipose tissue, yet these cells are sustained within a rich stromal vascular microenvironment comprised of adipose stem cells and progenitors, immune cells, neuronal cells, fibroblasts, and endothelial cells. Intricate cross talk between these diverse cell types is essential in regulating the activation of thermogenic fat, and the past decade has shed significant light on how this intercellular communication functions. This review will draw upon recent findings and current perspectives on the sophisticated repertoire of cellular and molecular features that comprise the adipose thermogenic milieu., (© 2020 by the American Diabetes Association.)

Eosinophils are granular cells of the innate immune system that are found in almost all vertebrates and some invertebrates. Knowledge of their wide-ranging roles in health and disease has largely been attained through studies in mice and humans. Although eosinophils are typically associated with helminth infections and allergic diseases such as asthma, there is building evidence that beneficial homeostatic eosinophils residing in specific niches are important for tissue development, remodelling and metabolic control. In recent years, the importance of immune cells in the regulation of adipose tissue homeostasis has been a focal point of research efforts. There is an abundance of anti-inflammatory innate immune cells in lean white adipose tissue, including macrophages, eosinophils and group 2 innate lymphoid cells, which promote energy homeostasis and stimulate the development of thermogenic beige adipocytes. This review will evaluate evidence for the role of adipose-resident eosinophils in local tissue homeostasis, beiging and systemic metabolism, highlighting where more research is needed to establish the specific effector functions that adipose eosinophils perform in response to different internal and external cues., (© 2020 John Wiley & Sons Australia, Ltd.)

Maintaining energy homeostasis upon environmental challenges, such as cold or excess calorie intake, is essential to the fitness and survival of mammals. Drug discovery efforts targeting β-adrenergic signaling have not been fruitful after decades of intensive research. We recently identified a new beige fat regulatory pathway mediated via the nicotinic acetylcholine receptor subunit CHRNA2. Here, we generated fat-specific Chrna2 KO mice and observed thermogenic defects in cold and metabolic dysfunction upon dietary challenges caused by adipocyte-autonomous regulation in vivo. We found that CHRNA2 signaling is activated after acute high fat diet feeding and this effect is manifested through both UCP1- and creatine-mediated mechanisms. Furthermore, our data suggested that CHRNA2 signaling may activate glycolytic beige fat, a subpopulation of beige adipocytes mediated by GABPα emerging in the absence of β-adrenergic signaling. These findings reveal the biological significance of the CHRNA2 pathway in beige fat biogenesis and energy homeostasis., Competing Interests: Declaration of Interests The authors declare no competing interests., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The conversion of white adipocytes to thermogenic beige adipocytes represents a potential mechanism to treat obesity and related metabolic disorders. However, the mechanisms involved in converting white to beige adipose tissue remain incompletely understood. Here we show profound beiging in a genetic mouse model lacking the transcriptional repressor Krüppel-like factor 3 (KLF3). Bone marrow transplants from these animals confer the beige phenotype on wild type recipients. Analysis of the cellular and molecular changes reveal an accumulation of eosinophils in adipose tissue. We examine the transcriptomic profile of adipose-resident eosinophils and posit that KLF3 regulates adipose tissue function via transcriptional control of secreted molecules linked to beiging. Furthermore, we provide evidence that eosinophils may directly act on adipocytes to drive beiging and highlight the critical role of these little-understood immune cells in thermogenesis.

Bacterial products such as lipopolysaccharides (or endotoxin) cause systemic inflammation, resulting in a substantial global health burden. The onset, progression, and resolution of the inflammatory response to endotoxin are usually tightly controlled to avoid chronic inflammation. Members of the NF-κB family of transcription factors are key drivers of inflammation that activate sets of genes in response to inflammatory signals. Such responses are typically short-lived and can be suppressed by proteins that act post-translationally, such as the SOCS (suppressor of cytokine signaling) family. Less is known about direct transcriptional regulation of these responses, however. Here, using a combination of in vitro approaches and in vivo animal models, we show that endotoxin treatment induced expression of the well-characterized transcriptional repressor Krüppel-like factor 3 (KLF3), which, in turn, directly repressed the expression of the NF-κB family member RELA/p65. We also observed that KLF3-deficient mice were hypersensitive to endotoxin and exhibited elevated levels of circulating Ly6C + monocytes and macrophage-derived inflammatory cytokines. These findings reveal that KLF3 is a fundamental suppressor that operates as a feedback inhibitor of RELA/p65 and may be important in facilitating the resolution of inflammation., (© 2020 Knights et al.)

The article Niacin‑mediated rejuvenation of macrophage/microglia enhances remyelination of the aging central nervous system, written by Khalil S. Rawji, Adam M.H. Young, Tanay Ghosh, Nathan J. Michaels, Reza Mirzaei, Janson Kappen, Kathleen L. Kolehmainen, Nima Alaeiilkhchi, Brian Lozinski, Manoj K. Mishra, Annie Pu, Weiwen Tang, Salma Zein, Deepak K. Kaushik, Michael B. Keough, Jason R. Plemel, Fiona Calvert, Andrew J. Knights, Daniel J. Gaffney, Wolfram Tetzlaff, Robin J. M. Franklin and V. Wee Yong, was originally published electronically on the publisher's internet.

Remyelination following CNS demyelination restores rapid signal propagation and protects axons; however, its efficiency declines with increasing age. Both intrinsic changes in the oligodendrocyte progenitor cell population and extrinsic factors in the lesion microenvironment of older subjects contribute to this decline. Microglia and monocyte-derived macrophages are critical for successful remyelination, releasing growth factors and clearing inhibitory myelin debris. Several studies have implicated delayed recruitment of macrophages/microglia into lesions as a key contributor to the decline in remyelination observed in older subjects. Here we show that the decreased expression of the scavenger receptor CD36 of aging mouse microglia and human microglia in culture underlies their reduced phagocytic activity. Overexpression of CD36 in cultured microglia rescues the deficit in phagocytosis of myelin debris. By screening for clinically approved agents that stimulate macrophages/microglia, we have found that niacin (vitamin B3) upregulates CD36 expression and enhances myelin phagocytosis by microglia in culture. This increase in myelin phagocytosis is mediated through the niacin receptor (hydroxycarboxylic acid receptor 2). Genetic fate mapping and multiphoton live imaging show that systemic treatment of 9-12-month-old demyelinated mice with therapeutically relevant doses of niacin promotes myelin debris clearance in lesions by both peripherally derived macrophages and microglia. This is accompanied by enhancement of oligodendrocyte progenitor cell numbers and by improved remyelination in the treated mice. Niacin represents a safe and translationally amenable regenerative therapy for chronic demyelinating diseases such as multiple sclerosis.

Protein arginine methyltransferases (PRMTs) are enzymes that regulate the evolutionarily conserved process of arginine methylation. It has been reported that PRMTs are involved in many metabolic regulatory pathways. However, until now, their roles in adipocyte function, especially browning and thermogenesis, have not been evaluated. Even though Prmt1 adipocyte-specific-deleted mice (Prmt1fl/flAQcre) appeared normal at basal level, following cold exposure or β-adrenergic stimulation, impaired induction of the thermogenic program was observed in both the interscapular brown adipose tissue and inguinal white adipose tissue of Prmt1fl/flAQcre mice compared with littermate controls. Different splicing variants of Prmt1 have been reported. Among them, PRMT1 variant 1 and PRMT1 variant 2 (PRMT1V2) are well conserved between humans and mice. Both variants contribute to the activation of thermogenic fat, with PRMT1V2 playing a more dominant role. Mechanistic studies using cultured murine and human adipocytes revealed that PRMT1V2 mediates thermogenic fat activation through PGC1α, a transcriptional coactivator that has been shown to play a key role in mitochondrial biogenesis. To our knowledge, our data are the first to demonstrate that PRMT1 plays a regulatory role in thermogenic fat function. These findings suggest that modulating PRMT1 activity may represent new avenues to regulate thermogenic fat and mediate energy homeostasis. This function is conserved in human primary adipocytes, suggesting that further investigation of this pathway may ultimately lead to therapeutic strategies against human obesity and associated metabolic disorders., (Copyright © 2019 Endocrine Society.)

The polarization processes for M1 versus M2 macrophages are quite distinct in the context of changes in cellular metabolism. M1 macrophages are highly glycolytic, whereas M2 macrophages require a more oxidative nutrient metabolism. An important part of M1 polarization involves upregulation of the glucose transporter (GLUT) GLUT1 to facilitate increased glucose uptake and glycolytic metabolism; however, the role of other glucose transporters in this process is largely unknown. In surveying the Functional Annotation of the Mammalian Genome and Gene Expression Omnibus Profiles databases, we discovered that the glucose transporter GLUT6 is highly upregulated in LPS-activated macrophages. In our previous work, we have not detected mouse GLUT6 protein expression in any noncancerous tissue; therefore, in this study, we investigated the expression and significance of GLUT6 in bone marrow-derived macrophages from wild-type and GLUT6 knockout C57BL/6 mice. We show that LPS-induced M1 polarization markedly upregulated GLUT6 protein, whereas naive macrophages and IL-4-induced M2 macrophages do not express GLUT6 protein. However, despite strong upregulation of GLUT6 in M1 macrophages, the absence of GLUT6 did not alter M1 polarization in the context of glucose uptake, glycolytic metabolism, or cytokine production. Collectively, these data show that GLUT6 is dispensable for LPS-induced M1 polarization and function. These findings are important because GLUT6 is an anticancer drug target, and this study suggests that inhibition of GLUT6 may not impart detrimental side effects on macrophage function to interfere with their antitumor properties., (Copyright © 2019 by The American Association of Immunologists, Inc.)

Physical interaction of regulatory elements in three-dimensional space poses a challenge for studies of disease because non-coding risk variants may be great distances from the genes they regulate. Experimental methods to capture these interactions, such as chromosome conformation capture, usually cannot assign causal direction of effect between regulatory elements, an important component of fine-mapping studies. We developed a Bayesian hierarchical approach that uses two-stage least squares and applied it to an ATAC-seq (assay for transposase-accessible chromatin using sequencing) data set from 100 individuals, to identify over 15,000 high-confidence causal interactions. Most (60%) interactions occurred over <20 kb, where chromosome conformation capture-based methods perform poorly. For a fraction of loci, we identified a single variant that alters accessibility across multiple regions, and experimentally validated the BLK locus, which is associated with multiple autoimmune diseases, using CRISPR genome editing. Our study highlights how association genetics of chromatin state is a powerful approach for identifying interactions between regulatory elements.

Tumor-specific T cell receptor (TCR) gene transfer enables specific and potent immune targeting of tumor antigens. Due to the prevalence of the HLA-A2 MHC class I supertype in most human populations, the majority of TCR gene therapy trials targeting public antigens have employed HLA-A2-restricted TCRs, limiting this approach to those patients expressing this allele. For these patients, TCR gene therapy trials have resulted in both tantalizing successes and lethal adverse events, underscoring the need for careful selection of antigenic targets. Broad and safe application of public antigen-targeted TCR gene therapies will require ( i ) selecting public antigens that are highly tumor-specific and ( ii ) targeting multiple epitopes derived from these antigens by obtaining an assortment of TCRs restricted by multiple common MHC alleles. The canonical cancer-testis antigen, NY-ESO-1, is not expressed in normal tissues but is aberrantly expressed across a broad array of cancer types. It has also been targeted with A2-restricted TCR gene therapy without adverse events or notable side effects. To enable the targeting of NY-ESO-1 in a broader array of HLA haplotypes, we isolated TCRs specific for NY-ESO-1 epitopes presented by four MHC molecules: HLA-A2, -B07, -B18, and -C03. Using these TCRs, we pilot an approach to extend TCR gene therapies targeting NY-ESO-1 to patient populations beyond those expressing HLA-A2., Competing Interests: Conflict of interest statement: A patent application has been filed (serial no. 62/727,485) entitled “Composition of NY-ESO-1-Specific T Cell Receptors Restricted on Multiple Major Histocompatibility Complex Molecules.”, (Copyright © 2018 the Author(s). Published by PNAS.)

The ability of transcriptional regulators to drive lineage conversion of somatic cells offers great potential for the treatment of human disease. To explore the concept of switching on specific target genes in heterologous cells, we developed a model system to screen candidate factors for their ability to activate the archetypal megakaryocyte-specific chemokine platelet factor 4 (PF4) in fibroblasts. We found that co-expression of the transcriptional regulators GATA1 and FLI1 resulted in a significant increase in levels of PF4, which became magnified over time. This finding demonstrates that such combinations can be used to produce potentially beneficial chemokines in readily available heterologous cell types.

Despite promising early work into the role of immune cells such as eosinophils in adipose tissue (AT) homeostasis, recent findings revealed that elevating the number of eosinophils in AT alone is insufficient for improving metabolic impairments in obese mice. Eosinophils are primarily recognized for their role in allergic immunity and defence against parasitic worms. They have also been detected in AT and appear to contribute to adipose homeostasis and drive energy expenditure, but the underlying mechanisms remain elusive. It has long been recognized that immune cells such as macrophages respond to external signals to regulate adipose homeostasis and energy balance, however, less is known about the relevance of eosinophil activity in AT. As the authors propose in this review, given recent debate over the relative importance of their tissue-specific abundance, the stage is now set for exploring the functionality and activation states of AT eosinophils., (© 2018 WILEY Periodicals, Inc.)

The histone H3 Lys27-specific demethylase UTX (or KDM6A) is targeted by loss-of-function mutations in multiple cancers. Here, we demonstrate that UTX suppresses myeloid leukemogenesis through noncatalytic functions, a property shared with its catalytically inactive Y-chromosome paralog, UTY (or KDM6C). In keeping with this, we demonstrate concomitant loss/mutation of KDM6A (UTX) and UTY in multiple human cancers. Mechanistically, global genomic profiling showed only minor changes in H3K27me3 but significant and bidirectional alterations in H3K27ac and chromatin accessibility; a predominant loss of H3K4me1 modifications; alterations in ETS and GATA-factor binding; and altered gene expression after Utx loss. By integrating proteomic and genomic analyses, we link these changes to UTX regulation of ATP-dependent chromatin remodeling, coordination of the COMPASS complex and enhanced pioneering activity of ETS factors during evolution to AML. Collectively, our findings identify a dual role for UTX in suppressing acute myeloid leukemia via repression of oncogenic ETS and upregulation of tumor-suppressive GATA programs.

Regulatory variants are often context specific, modulating gene expression in a subset of possible cellular states. Although these genetic effects can play important roles in disease, the molecular mechanisms underlying context specificity are poorly understood. Here, we identified shared quantitative trait loci (QTLs) for chromatin accessibility and gene expression in human macrophages exposed to IFNγ, Salmonella and IFNγ plus Salmonella. We observed that ~60% of stimulus-specific expression QTLs with a detectable effect on chromatin altered the chromatin accessibility in naive cells, thus suggesting that they perturb enhancer priming. Such variants probably influence binding of cell-type-specific transcription factors, such as PU.1, which can then indirectly alter the binding of stimulus-specific transcription factors, such as NF-κB or STAT2. Thus, although chromatin accessibility assays are powerful for fine-mapping causal regulatory variants, detecting their downstream effects on gene expression will be challenging, requiring profiling of large numbers of stimulated cellular states and time points.

Induced pluripotent stem cells (iPSCs), and cells derived from them, have become key tools for modeling biological processes, particularly in cell types that are difficult to obtain from living donors. Here we present a map of regulatory variants in iPSC-derived neurons, based on 123 differentiations of iPSCs to a sensory neuronal fate. Gene expression was more variable across cultures than in primary dorsal root ganglion, particularly for genes related to nervous system development. Using single-cell RNA-sequencing, we found that the number of neuronal versus contaminating cells was influenced by iPSC culture conditions before differentiation. Despite high differentiation-induced variability, our allele-specific method detected thousands of quantitative trait loci (QTLs) that influenced gene expression, chromatin accessibility, and RNA splicing. On the basis of these detected QTLs, we estimate that recall-by-genotype studies that use iPSC-derived cells will require cells from at least 20-80 individuals to detect the effects of regulatory variants with moderately large effect sizes.

The Lgals3 gene encodes a multifunctional β-galactoside-binding protein, galectin-3. Galectin-3 has been implicated in a broad range of biological processes from chemotaxis and inflammation to fibrosis and apoptosis. The role of galectin-3 as a modulator of inflammation has been studied intensively, and recent evidence suggests that it may serve as a protective factor in obesity and other metabolic disorders. Despite considerable interest in galectin-3, little is known about its physiological regulation at the transcriptional level. Here, using knockout mice, chromatin immunoprecipitations, and cellular and molecular analyses, we show that the zinc finger transcription factor Krüppel-like factor 3 (KLF3) directly represses galectin-3 transcription. We find that galectin-3 is broadly up-regulated in KLF3-deficient mouse tissues, that KLF3 occupies regulatory regions of the Lgals3 gene, and that KLF3 directly binds its cognate elements (CACCC boxes) in the galectin-3 promoter and represses its activation in cellular assays. We also provide mechanistic insights into the regulation of Lgals3, demonstrating that C-terminal binding protein (CtBP) is required to drive optimal KLF3-mediated silencing. These findings help to enhance our understanding of how expression of the inflammatory modulator galectin-3 is controlled, opening up avenues for potential therapeutic interventions in the future., (© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.)

Background: A current focus in cancer treatment is to broaden responses to immunotherapy. One reason these therapies may prove inadequate is that T lymphocytes fail to recognize the tumor due to differences in immunogenic epitopes presented by the cancer cells under inflammatory or non-inflammatory conditions. The antigen processing machinery of the cell, the proteasome, cleaves proteins into peptide epitopes for presentation on MHC complexes. Immunoproteasomes in inflammatory melanomas, and in antigen presenting cells of the immune system, are enzymatically different to standard proteasomes expressed by tumors with no inflammation. This corresponds to alterations in protein cleavage between proteasome subtypes, and a disparate repertoire of MHC-presented epitopes., Methods: We assessed steady state and IFNγ-induced immunoproteasome expression in melanoma cells. Using epitope specific T-lymphocyte clones, we studied processing and presentation of three NY-ESO-1 HLA-Cw3 restricted epitopes by melanoma cell lines. Our experimental model allowed comparison of the processing of three distinct epitopes from a single antigen presented on the same HLA complex. We further investigated processing of these epitopes by direct inhibition, or siRNA mediated knockdown, of the immunoproteasome catalytic subunit LMP7., Results: Our data demonstrated a profound difference in the way in which immunogenic T-lymphocyte epitopes are presented by melanoma cells under IFNγ inflammatory versus non-inflammatory conditions. These alterations led to significant changes in the ability of T-lymphocytes to recognize and target melanoma cells., Conclusions: Our results illustrate a little-studied mechanism of immune escape by tumor cells which, with appropriate understanding and treatment, may be reversible. These data have implications for the design of cancer vaccines and adoptive T cell therapies.

When cellular traits are measured using high-throughput DNA sequencing, quantitative trait loci (QTLs) manifest as fragment count differences between individuals and allelic differences within individuals. We present RASQUAL (Robust Allele-Specific Quantitation and Quality Control), a new statistical approach for association mapping that models genetic effects and accounts for biases in sequencing data using a single, probabilistic framework. RASQUAL substantially improves fine-mapping accuracy and sensitivity relative to existing methods in RNA-seq, DNase-seq and ChIP-seq data. We illustrate how RASQUAL can be used to maximize association detection by generating the first map of chromatin accessibility QTLs (caQTLs) in a European population using ATAC-seq. Despite a modest sample size, we identified 2,707 independent caQTLs (at a false discovery rate of 10%) and demonstrated how RASQUAL and ATAC-seq can provide powerful information for fine-mapping gene-regulatory variants and for linking distal regulatory elements with gene promoters. Our results highlight how combining between-individual and allele-specific genetic signals improves the functional interpretation of noncoding variation., Competing Interests: Conflicts of Interest: None declared

Krüppel-like factor 3 (KLF3/BKLF), a member of the Krüppel-like factor (KLF) family of transcription factors, is a widely expressed transcriptional repressor with diverse biological roles. Although there is considerable understanding of the molecular mechanisms that allow KLF3 to silence the activity of its target genes, less is known about the signal transduction pathways and post-translational modifications that modulate KLF3 activity in response to physiological stimuli. We observed that KLF3 is modified in a range of different tissues and found that the serine/threonine kinase homeodomain-interacting protein kinase 2 (HIPK2) can both bind and phosphorylate KLF3. Mass spectrometry identified serine 249 as the primary phosphorylation site. Mutation of this site reduces the ability of KLF3 to bind DNA and repress transcription. Furthermore, we also determined that HIPK2 can phosphorylate the KLF3 co-repressor C-terminal binding protein 2 (CtBP2) at serine 428. Finally, we found that phosphorylation of KLF3 and CtBP2 by HIPK2 strengthens the interaction between these two factors and increases transcriptional repression by KLF3. Taken together, our results indicate that HIPK2 potentiates the activity of KLF3., (© 2015 by The American Society for Biochemistry and Molecular Biology, Inc.)

Obesity is a major public health concern and a strong risk factor for insulin resistance, type 2 diabetes mellitus (T2DM), and cardiovascular disease. The last two decades have seen a reconsideration of the role of white adipose tissue (WAT) in whole body metabolism and insulin action. Adipose tissue-derived cytokines and hormones, or adipokines, are likely mediators of metabolic function and dysfunction. While several adipokines have been associated with obese and insulin-resistant phenotypes, a select group has been linked with insulin sensitivity, namely leptin, adiponectin, and more recently, adipolin. What is known about these insulin-sensitizing molecules and their effects in healthy and insulin resistant states is the subject of this review. There remains a significant amount of research to do to fully elucidate the mechanisms of action of these adipokines for development of therapeutics in metabolic disease.

Krüppel-like factor 3 (KLF3) is a transcriptional regulator that we have shown to be involved in the regulation of adipogenesis in vitro. Here, we report that KLF3-null mice are lean and protected from diet-induced obesity and glucose intolerance. On a chow diet, plasma levels of leptin are decreased, and adiponectin is increased. Despite significant reductions in body weight and adiposity, wild-type and knockout animals show equivalent energy intake, expenditure, and excretion. To investigate the molecular events underlying these observations, we used microarray analysis to compare gene expression in Klf3(+/+) and Klf3(-/-) tissues. We found that mRNA expression of Fam132a, which encodes a newly identified insulin-sensitizing adipokine, adipolin, is significantly upregulated in the absence of KLF3. We confirmed that KLF3 binds the Fam132a promoter in vitro and in vivo and that this leads to repression of promoter activity. Further, plasma adipolin levels were significantly increased in Klf3(-/-) mice compared with wild-type littermates. Boosting levels of adipolin via targeting of KLF3 offers a novel potential therapeutic strategy for the treatment of insulin resistance.

Inhibitor of apoptosis proteins (IAPs) are critical in regulating apoptosis resistance in cancer. Antagonists of IAPs, such as LCL161, are in clinical development and show promise as anti-cancer agents for solid and hematological cancers, with preliminary data suggesting they may act as immunomodulators. IAP antagonists hypersensitize tumor cells to TNF-α-mediated apoptosis, an effect that may work in synergy with that of cancer vaccines. This study aimed to further investigate the immunomodulatory properties of LCL161 on human immune subsets. T lymphocytes treated with LCL161 demonstrated significantly enhanced cytokine secretion upon activation, with little effect on CD4 and CD8 T-cell survival or proliferation. LCL161 treatment of peripheral blood mononuclear cells significantly enhanced priming of naïve T cells with synthetic peptides in vitro. Myeloid dendritic cells underwent phenotypic maturation upon IAP antagonism and demonstrated a reduced capacity to cross-present a tumor antigen-based vaccine. These effects are potentially mediated through an observed activation of the canonical and non-canonical NF-κB pathways, following IAP antagonism with a resulting upregulation of anti-apoptotic molecules. In conclusion, this study demonstrated the immunomodulatory properties of antagonists at physiologically relevant concentrations and indicates their combination with immunotherapy requires further investigation.

NY-ESO-1 has been a major target of many immunotherapy trials because it is expressed by various cancers and is highly immunogenic. In this study, we have identified a novel HLA-B*1801-restricted CD8(+) T cell epitope, NY-ESO-1(88-96) (LEFYLAMPF) and compared its direct- and cross-presentation to that of the reported NY-ESO-1(157-165) epitope restricted to HLA-A*0201. Although both epitopes were readily cross-presented by DCs exposed to various forms of full-length NY-ESO-1 antigen, remarkably NY-ESO-1(88-96) is much more efficiently cross-presented from the soluble form, than NY-ESO-1(157-165). On the other hand, NY-ESO-1(157-165) is efficiently presented by NY-ESO-1-expressing tumor cells and its presentation was not enhanced by IFN-γ treatment, which induced immunoproteasome as demonstrated by Western blots and functionally a decreased presentation of Melan A(26-35); whereas NY-ESO-1(88-96) was very inefficiently presented by the same tumor cell lines, except for one that expressed high level of immunoproteasome. It was only presented when the tumor cells were first IFN-γ treated, followed by infection with recombinant vaccinia virus encoding NY-ESO-1, which dramatically increased NY-ESO-1 expression. These data indicate that the presentation of NY-ESO-1(88-96) is immunoproteasome dependent. Furthermore, a survey was conducted on multiple samples collected from HLA-B18(+) melanoma patients. Surprisingly, all the detectable responses to NY-ESO-1(88-96) from patients, including those who received NY-ESO-1 ISCOMATRIX™ vaccine were induced spontaneously. Taken together, these results imply that some epitopes can be inefficiently presented by tumor cells although the corresponding CD8(+) T cell responses are efficiently primed in vivo by DCs cross-presenting these epitopes. The potential implications for cancer vaccine strategies are further discussed.

Cell junctions are sites of intercellular adhesion that maintain the integrity of epithelial tissue and regulate signalling between cells. These adhesive junctions are comprised of protein complexes that serve to establish an intercellular cytoskeletal network for anchoring cells, in addition to regulating cell polarity, molecular transport and communication. The expression of cell adhesion molecules is tightly controlled and their downregulation is essential for epithelial-mesenchymal transition (EMT), a process that facilitates the generation of morphologically and functionally diverse cell types during embryogenesis. The characteristics of EMT are a loss of cell adhesion and increased cellular mobility. Hence, in addition to its normal role in development, dysregulated EMT has been linked to cancer progression and metastasis, the process whereby primary tumors migrate to invasive secondary sites in the body. This paper will review the current understanding of cell junctions and their role in cancer, with reference to the abnormal regulation of junction protein genes. The potential use of cell junction molecules as diagnostic and prognostic markers will also be discussed, as well as possible therapies for adhesive dysregulation.

Small RNAs are functional molecules that modulate mRNA transcripts and have been implicated in the aetiology of several common diseases. However, little is known about the extent of their variability within the human population. Here, we characterise the extent, causes, and effects of naturally occurring variation in expression and sequence of small RNAs from adipose tissue in relation to genotype, gene expression, and metabolic traits in the MuTHER reference cohort. We profiled the expression of 15 to 30 base pair RNA molecules in subcutaneous adipose tissue from 131 individuals using high-throughput sequencing, and quantified levels of 591 microRNAs and small nucleolar RNAs. We identified three genetic variants and three RNA editing events. Highly expressed small RNAs are more conserved within mammals than average, as are those with highly variable expression. We identified 14 genetic loci significantly associated with nearby small RNA expression levels, seven of which also regulate an mRNA transcript level in the same region. In addition, these loci are enriched for variants significant in genome-wide association studies for body mass index. Contrary to expectation, we found no evidence for negative correlation between expression level of a microRNA and its target mRNAs. Trunk fat mass, body mass index, and fasting insulin were associated with more than twenty small RNA expression levels each, while fasting glucose had no significant associations. This study highlights the similar genetic complexity and shared genetic control of small RNA and mRNA transcripts, and gives a quantitative picture of small RNA expression variation in the human population., Competing Interests: The authors have declared that no competing interests exist.

The ability of dendritic cells (DCs) to cross-present protein tumor antigens to cytotoxic T lymphocytes (CTLs) underpins the success of therapeutic cancer vaccines. We studied cross-presentation of the cancer/testis antigen, NY-ESO-1, and the melanoma differentiation antigen, Melan-A by human DC subsets. Monocyte-derived DCs (MoDCs) efficiently cross-presented human leukocyte associated (HLA)-A2-restricted epitopes from either a formulated NY-ESO-1/ISCOMATRIX vaccine or when either antigen was mixed with ISCOMATRIX adjuvant. HLA-A2 epitope generation required endosomal acidification and was proteasome-independent for NY-ESO-1 and proteasome-dependent for Melan-A. Both MoDCs and CD1c(+) blood DCs cross-presented NY-ESO-1-specific HLA-A2(157-165)-, HLA-B7(60-72)-, and HLA-Cw3(92-100)-restricted epitopes when formulated as an NY-ESO-1/ISCOMATRIX vaccine, but this was limited when NY-ESO-1 and ISCOMATRIX adjuvant were added separately to the DC cultures. Finally, cross-presentation of NY-ESO-1(157-165)/HLA-A2, NY-ESO-1(60-72)/HLA-B7, and NY-ESO-1(92-100)/HLA-Cw3 epitopes was proteasome-dependent when formulated as immune complexes (ICs) but only proteasome-dependent for NY-ESO-1(60-72)/HLA-B7-restricted cross-presentation facilitated by ISCOMATRIX adjuvant. We demonstrate, for the first time, proteasome-dependent and independent cross-presentation of HLA-A-, B-, and C-restricted epitopes within the same full-length tumor antigen by human DCs. Our findings identify important differences in the capacities of human DC subsets to cross-present clinically relevant, full-length tumor antigens and how vaccine formulation impacts CTL responses in vivo.

The development of effective anti-cancer vaccines requires precise assessment of vaccine-induced immunity. This is often hampered by low ex vivo frequencies of antigen-specific T cells and limited defined epitopes. This study investigates the applicability of modified, in vitro-transcribed mRNA encoding a therapeutically relevant tumour antigen to analyse T cell responses in cancer patients. In this study transfection of antigen presenting cells, by mRNA encoding the tumour antigen NY-ESO-1, was optimised and applied to address spontaneous and vaccine-induced T cell responses in cancer patients. Memory CD8+ T cells from lung cancer patients having detectable humoral immune responses directed towards NY-ESO-1 could be efficiently detected in peripheral blood. Specific T cells utilised a range of different T cell receptors, indicating a polyclonal response. Specific killing of a panel of NY-ESO-1 expressing tumour cell lines indicates recognition restricted to several HLA allelic variants, including a novel HLA-B49 epitope. Using a modified mRNA construct targeting the translated antigen to the secretory pathway, detection of NY-ESO-1-specific CD4+ T cells in patients could be enhanced, which allowed the in-depth characterisation of established T cell clones. Moreover, broad CD8+ and CD4+ T cell responses covering multiple epitopes were detected following mRNA stimulation of patients treated with a recombinant vaccinia/fowlpox NY-ESO-1 vaccine. This approach allows for a precise monitoring of responses to tumour antigens in a setting that addresses the breadth and magnitude of antigen-specific T cell responses, and that is not limited to a particular combination of known epitopes and HLA-restrictions.

There remains a need to identify novel epitopes of potential tumour target antigens for use in immunotherapy of cancer. Here, several melanoma tissues and cell lines but not normal tissues were found to overexpress the cancer-testis antigen HAGE at the mRNA and protein level. We identified a HAGE-derived 15-mer peptide containing a shorter predicted MHC class I-binding sequence within a class II-binding sequence. However, only the longer peptide was found to be both endogenously processed and immunogenic for T cells in transgenic mice in vivo, as well as for human T cells in vitro. A different class I-binding peptide, not contained within a longer class II sequence, was subsequently found to be both immunogenic and endogenously processed in transgenic mice, as was a second class II epitope. These novel HAGE-derived epitopes may contribute to the range of immunotherapeutic targets for use in cancer vaccination programs.

Three of the most promising antigens for immunotherapy of chronic myelogenous leukaemia (CML) include the specific fusion-protein, Bcr/Abl, and the overexpressed proteins WT1 and Proteinase 3. The clinical significance of Proteinase 3 as a target in myelogenous leukaemias has been bolstered by detection of high frequencies of cytotoxic CD8+ lymphocytes specific for this antigen in patients undergoing immune therapies. Our investigation aimed to directly identify MHC-ligands derived from these antigens and presented on CML blasts by means of affinity-purification and mass spectrometric peptide-sequencing. Although no known or potential new epitopes were discovered for Bcr/Abl or WT1, a novel peptide from Proteinase 3 was detected among the more abundant MHC-ligands. Additionally, MHC-ligands derived from known immunogenic proteins overexpressed as a result of Bcr/Abl transformation were also identified. Our investigation is the second of only a small number of studies to identify a peptide from Proteinase 3 among the more abundant MHC-associated peptides and thus implies that peptides from this antigen are among the more abundantly presented of the known leukaemic antigens. Taken in conjunction with clinical observations of functional Proteinase 3 specific CTL in patients', these data further support the application of this antigen as an immunotherapeutical target for myelogenous leukaemias.

The reference sequence for each human chromosome provides the framework for understanding genome function, variation and evolution. Here we report the finished sequence and biological annotation of human chromosome 1. Chromosome 1 is gene-dense, with 3,141 genes and 991 pseudogenes, and many coding sequences overlap. Rearrangements and mutations of chromosome 1 are prevalent in cancer and many other diseases. Patterns of sequence variation reveal signals of recent selection in specific genes that may contribute to human fitness, and also in regions where no function is evident. Fine-scale recombination occurs in hotspots of varying intensity along the sequence, and is enriched near genes. These and other studies of human biology and disease encoded within chromosome 1 are made possible with the highly accurate annotated sequence, as part of the completed set of chromosome sequences that comprise the reference human genome.