Trithorax complex component Menin controls differentiation and maintenance of T helper 17 cells

Epigenetic regulation of inflammation by CxxC domain-containing proteins

Epigenetic regulation of gene transcription in the immune system is important for proper control of protective and pathogenic inflammation. Aberrant epigenetic modifications are often associated with dysregulation of the immune cells, including lymphocytes and macrophages, leading to pathogenic inflammation and autoimmune diseases. Two classical epigenetic markers-histone modifications and DNA cytosine methylation, the latter is the 5 position of the cytosine base in the context of CpG dinucleotides-play multiple roles in the immune system. CxxC domain-containing proteins, which basically bind to the non-methylated CpG (i.e., epigenetic "readers"), often function as "writers" of the epigenetic markers via their catalytic domain within the proteins or by interacting with other epigenetic modifiers. We herein report the most recent advances in our understanding of the functions of CxxC domain-containing proteins in the immune system and inflammation, mainly focusing on T cells and macrophages.

The Cxxc1 subunit of the Trithorax complex directs epigenetic licensing of CD4+ T cell differentiation

Different dynamics of gene expression are observed during cell differentiation. In T cells, genes that are turned on early or turned off and stay off have been thoroughly studied. However, genes that are initially turned off but then turned on again after stimulation has ceased have not been defined; they are obviously important, especially in the context of acute versus chronic inflammation. Using the Th1/Th2 differentiation paradigm, we found that the Cxxc1 subunit of the Trithorax complex directs transcription of genes initially down-regulated by TCR stimulation but up-regulated again in a later phase. The late up-regulation of these genes was impaired either by prolonged TCR stimulation or Cxxc1 deficiency, which led to decreased expression of Trib3 and Klf2 in Th1 and Th2 cells, respectively. Loss of Cxxc1 resulted in enhanced pathogenicity in allergic airway inflammation in vivo. Thus, Cxxc1 plays essential roles in the establishment of a proper CD4⁺ T cell immune system via epigenetic control of a specific set of genes.

Essential Role for CD30-Transglutaminase 2 Axis in Memory Th1 and Th17 Cell Generation

Memory helper T (Th) cells are crucial for secondary immune responses against infectious microorganisms but also drive the pathogenesis of chronic inflammatory diseases. Therefore, it is of fundamental importance to understand how memory T cells are generated. However, the molecular mechanisms governing memory Th cell generation remain incompletely understood. Here, we identified CD30 as a molecule heterogeneously expressed on effector Th1 and Th17 cells, and CD30^hi effector Th1 and Th17 cells preferentially generated memory Th1 and Th17 cells. We found that CD30 mediated signal induced Transglutaminase-2 (TG2) expression, and that the TG2 expression in effector Th cells is essential for memory Th cell generation. In fact, Cd30-deficiency resulted in the impaired generation of memory Th1 and Th17 cells, which can be rescued by overexpression of TG2. Furthermore, transglutaminase-2 (Tgm2)-deficient CD4 T cells failed to become memory Th cells. As a result, T cells from Tgm2-deficient mice displayed impaired antigen-specific antibody production and attenuated Th17-mediated allergic responses. Our data indicate that CD30-induced TG2 expression in effector Th cells is essential for the generation of memory Th1 and Th17 cells, and that CD30 can be a marker for precursors of memory Th1 and Th17 cells.

Epigenetic initiation of the TH17 differentiation program is promoted by Cxxc finger protein 1

IL-6/STAT3 signaling is known to initiate the T_H17 differentiation program, but the upstream regulatory mechanisms remain minimally explored. Here, we show that Cxxc finger protein 1 (Cxxc1) promoted the generation of T_H17 cells as an epigenetic regulator and prevented their differentiation into T_reg cells. Mice with a T cell-specific deletion of Cxxc1 were protected from experimental autoimmune encephalomyelitis and were more susceptible to Citrobacter rodentium infection. Cxxc1 deficiency decreased IL-6Rα expression and impeded IL-6/STAT3 signaling, whereas the overexpression of IL-6Rα could partially reverse the defects in Cxxc1-deficient T_H17 cells in vitro and in vivo. Genome-wide occupancy analysis revealed that Cxxc1 bound to Il6rα gene loci by maintaining the appropriate H3K4me3 modification of its promoter. Therefore, these data highlight that Cxxc1 as a key regulator governs the balance between T_H17 and T_reg cells by controlling the expression of IL-6Rα, which affects IL-6/STAT3 signaling and has an impact on T_H17-related autoimmune diseases.

Epigenetic and Transcriptional Regulation in the Induction, Maintenance, Heterogeneity, and Recall-Response of Effector and Memory Th2 Cells

Antigen-primed T cells respond to restimulation much faster than naïve T cells and form the cellular basis of immunological memory. The formation of memory Th2 cells starts when naïve CD4 T cells are transformed into effector Th2 cells and is completed after antigen clearance and a long-term resting phase accompanied by epigenetic changes in the Th2 signature genes. Memory Th2 cells maintain their functions and acquired heterogeneity through epigenetic machinery, on which the recall-response of memory Th2 cells is also dependent. We provide an overview of the epigenetics in the whole Th2 cell cycle, mainly focusing on two different histone lysine methyltransferase complexes: the Polycomb and Trithorax groups. We finally discuss the pathophysiology and potential therapeutic strategies for the treatment of Th2-mediated inflammatory diseases in mice and humans.

Serial representation of items during working memory maintenance at letter-selective cortical sites

A key component of working memory is the ability to remember multiple items simultaneously. To understand how the human brain maintains multiple items in memory, we examined direct brain recordings of neural oscillations from neurosurgical patients as they performed a working memory task. We analyzed the data to identify the neural representations of individual memory items by identifying recording sites with broadband gamma activity that varied according to the identity of the letter a subject viewed. Next, we tested a previously proposed model of working memory, which had hypothesized that the neural representations of individual memory items sequentially occurred at different phases of the theta/alpha cycle. Consistent with this model, the phase of the theta/alpha oscillation when stimulus-related gamma activity occurred during maintenance reflected the order of list presentation. These results suggest that working memory is organized by a cortical phase code coordinated by coupled theta/alpha and gamma oscillations and, more broadly, provide support for the serial representation of items in working memory.

Epigenetic regulation of T-helper cell differentiation, memory, and plasticity in allergic asthma

An estimated 300 million people currently suffer from asthma, which causes approximately 250 000 deaths a year. Allergen-specific T-helper (Th) cells produce cytokines that induce many of the hallmark features of asthma including airways hyperreactivity, eosinophilic and neutrophilic inflammation, mucus hypersecretion, and airway remodeling. Cytokine-producing Th subsets including Th1 (IFN-γ), Th2 (IL-4, IL-5, IL-13), Th9 (IL-9), Th17 (IL-17), Th22 (IL-22), and T regulatory (IL-10) cells have all been suggested to play a role in the development of asthma. Th differentiation involves genetic regulation of gene expression through the concerted action of cytokines, transcription factors, and epigenetic regulators. We describe how Th differentiation and plasticity is regulated by epigenetic histone and DNA modifications, with a focus on the regulation of histone methylation by members of the polycomb and trithorax complexes. In addition, we outline environmental influences that could influence epigenetic regulation of Th cells and discuss the potential to regulate Th plasticity and function through drugs targeting the epigenetic machinery. It is also becoming apparent that epigenetic regulation of allergen-specific memory Th cells may be important in the development and persistence of chronic allergies. Finally, we describe how epigenetic modifiers regulate cytokine memory in Th cells and describe recently identified hybrid, plastic, and pathogenic memory Th subsets the context of allergic asthma.

Allergic airway inflammation: key players beyond the Th2 cell pathway

Allergic asthma is characterized by eosinophilic airway inflammation, mucus hyperproduction, and airway hyperreactivity, causing reversible airway obstruction. Accumulating evidence indicates that antigen-specific Th2 cells and their cytokines such as IL-4, IL-5, and IL-13 orchestrate these pathognomonic features of asthma. However, over the past decade, the understanding of asthma pathogenesis has made a significant shift from a Th2 cell-dependent, IgE-mediated disease to a more complicated heterogeneous disease. Recent studies clearly show that not only Th2 cytokines but also other T cell-related cytokines such as IL-17A and IL-22 as well as epithelial cell cytokines such as IL-25, IL-33, and thymic stromal lymphopoietin (TSLP) are involved in the pathogenesis of asthma. In this review, we focus on the roles of these players beyond Th2 pathways in the pathogenesis of asthma.

A Review of the Scaffold Protein Menin and its Role in Hepatobiliary Pathology

Multiple endocrine neoplasia type 1 (MEN1) is a familial cancer syndrome with neuroendocrine tumorigenesis of the parathyroid glands, pituitary gland, and pancreatic islet cells. The MEN1 gene codes for the canonical tumor suppressor protein, menin. Its protein structure has recently been crystallized, and it has been investigated in a multitude of other tissues. In this review, we summarize recent advancements in understanding the structure of the menin protein and its function as a scaffold protein in histone modification and epigenetic gene regulation. Furthermore, we explore its role in hepatobiliary autoimmune diseases, cancers, and metabolic diseases. In particular, we discuss how menin expression and function are regulated by extracellular signaling factors and nuclear receptor activation in various hepatic cell types. How the many signaling pathways and tissue types affect menin's diverse functions is not fully understood. We show that small-molecule inhibitors affecting menin function can shed light on menin's broad role in pathophysiology and elucidate distinct menin-dependent processes. This review reveals menin's often dichotomous function through analysis of its role in multiple disease processes and could potentially lead to novel small-molecule therapies in the treatment of cholangiocarcinoma or biliary autoimmune diseases.

Pathogenic Th cell subsets in chronic inflammatory diseases

CD4(+) T cells play central roles to appropriate protection against pathogens. While, they can also be pathogenic driving inflammatory diseases. Besides the classical model of differentiation of T helper 1 (Th1) and Th2 cells, various CD4(+) T cell subsets, including Th17, Th9, T follicular helper (Tfh) and T regulatory (Treg) cells, have been recognized recently. In this review, we will focus on how these various CD4(+) T cell subsets contribute to the pathogenesis of immune-mediated inflammatory diseases. We will also discuss various unique subpopulations of T helper cells that have been identified. Recent advancement of the basic immunological research revealed that T helper cells are plastic than we imagined. So, we will focus on the molecular mechanisms underlying the generation of the plasticity and heterogeneity of T helper cell subsets. These latest finding regarding T helper cell subsets has pushed us to reconsider the etiology of immune-mediated inflammatory diseases beyond the model based on the conventional Th1/Th2 balance. Toward this end, we put forward another model, "the pathogenic Th population disease induction model", as a possible mechanism for the induction and/or persistence of immune-mediated inflammatory diseases.

Th2 Cells in Health and Disease

Helper T (Th) cell subsets direct immune responses by producing signature cytokines. Th2 cells produce IL-4, IL-5, and IL-13, which are important in humoral immunity and protection from helminth infection and are central to the pathogenesis of many allergic inflammatory diseases. Molecular analysis of Th2 cell differentiation and maintenance of function has led to recent discoveries that have refined our understanding of Th2 cell biology. Epigenetic regulation of Gata3 expression by chromatin remodeling complexes such as Polycomb and Trithorax is crucial for maintaining Th2 cell identity. In the context of allergic diseases, memory-type pathogenic Th2 cells have been identified in both mice and humans. To better understand these disease-driving cell populations, we have developed a model called the pathogenic Th population disease induction model. The concept of defined subsets of pathogenic Th cells may spur new, effective strategies for treating intractable chronic inflammatory disorders.

CD4+ T-cell subsets in inflammatory diseases: beyond the Th1/Th2 paradigm

CD4(+)T cells are crucial for directing appropriate immune responses during host defense and for the pathogenesis of inflammatory diseases. In addition to the classical biphasic model of differentiation of T-helper 1 (Th1) and Th2 cells, unexpected increases in the numbers of CD4(+)T-cell subsets, including Th17, Th9, T follicular-helper (Tfh) and T-regulatory (Treg) cells, have been recognized. In the present review, we focus on how these various T-helper cell subsets contribute to the pathogenesis of immune-mediated inflammatory diseases. In particular, we focus on multiple sclerosis, psoriasis and asthma as typical model diseases in which multiple T-helper cell subsets have recently been suggested to play a role. We will also discuss various unique sub-populations of T-helper cells that have been identified. First, we will introduce the heterogeneous T-helper cell subsets, which are classified by their simultaneous expression of multiple key transcription factors. We will also introduce different kinds of memory-type Th2 cells, which are involved in the pathogenesis of chronic type-2 immune-related diseases. Finally, we will discuss the molecular mechanisms underlying the generation of the plasticity and heterogeneity of T-helper cell subsets. The latest progress in the study of T-helper cell subsets has forced us to reconsider the etiology of immune-mediated inflammatory diseases beyond the model based on the Th1/Th2 balance. To this end, we propose another model--the pathogenic T-helper population disease-induction model--as a possible mechanism for the induction and/or persistence of immune-mediated inflammatory diseases.