Setd2 supports GATA3+ST2+ thymic-derived Treg cells and suppresses intestinal inflammation.

Treg cells acquire distinct transcriptional properties to suppress specific inflammatory responses. Transcription characteristics of Treg cells are regulated by epigenetic modifications, the mechanism of which remains obscure. Here, we report that Setd2, a histone H3K36 methyltransferase, is important for the survival and suppressive function of Treg cells, especially those from the intestine. Setd2 supports GATA3+ST2+ intestinal thymic-derived Treg (tTreg) cells by facilitating the expression and reciprocal relationship of GATA3 and ST2 in tTreg cells. IL-33 preferentially boosts Th2 cells rather than GATA3+ Treg cells in Foxp3Cre-YFPSetd2 flox/flox mice, corroborating the constraint of Th2 responses by Setd2 expression in Treg cells. SETD2 sustains GATA3 expression in human Treg cells, and SETD2 expression is increased in Treg cells from human colorectal cancer tissues. Epigenetically, Setd2 regulates the transcription of target genes (including Il1rl1) by modulating the activity of promoters and intragenic enhancers where H3K36me3 is typically deposited. Our findings provide mechanistic insights into the regulation of Treg cells and intestinal immunity by Setd2.

Decreased Jumonji Domain-Containing 3 at the Promoter Downregulates Hematopoietic Progenitor Kinase 1 Expression and Cytoactivity of T Follicular Helper Cells from Systemic Lupus Erythematosus Patients.

T follicular helper (Tfh) cells are overactivated in systemic lupus erythematosus (SLE) patients and contribute to excessive immunity. Hematopoietic progenitor kinase 1 (HPK1), as an inhibitor of T cells, is underexpressed in SLE Tfh cells and consequently induces autoimmunity. However, the reason for downregulation of HPK1 in SLE Tfh cells remains elusive. By combining chromatin immunoprecipitation with quantitative polymerase chain reaction assays, it was found that histone H3 lysine 27 trimethylation (H3K27me3) at the HPK1 promoter in SLE Tfh cells elevated greatly. We also confirmed jumonji domain-containing 3 (JMJD3) binding at the HPK1 promoter in SLE Tfh cells reduced profoundly. Knocking down JMJD3 in normal Tfh cells with siRNA alleviated enrichments of JMJD3, H3K4me3, and mixed-lineage leukemia (MLL) 1 at the HPK1 promoter and increased H3K27me3 number in the region. HPK1 expression was lowered, while Tfh cell proliferation activity, IL-21 and IFNγ secretions in the supernatants of Tfh cells, and IgG1 and IgG3 concentrations in the supernatants of Tfh-B cell cocultures all upregulated markedly. In contrast, elevating JMJD3 amount in SLE Tfh cells by JMJD3-overexpressed plasmid showed opposite effects. The abundances of H3K4me3 and MLL1 at the HPK1 promoter in SLE Tfh cells were greatly attenuated. Our results suggest that deficient JMJD3 binding at the promoter dampens HPK1 expression in SLE Tfh cells, thus making Tfh cells overactive, and ultimately results in onset of SLE.

Does lineage plasticity enable escape from CAR-T cell therapy? Lessons from MLL-r leukemia.

The clinical success of engineered, CD19-directed chimeric antigen receptor (CAR) T cells in relapsed, refractory B-cell acute lymphoblastic leukemia (B-ALL) has generated great enthusiasm for the use of CAR T cells in patients with cytogenetics that portend a poor prognosis with conventional cytotoxic therapies. One such group includes infants and children with mixed lineage leukemia (MLL1, KMT2A) rearrangements (MLL-r), who fare much worse than patients with low- or standard-risk B-ALL. Although early clinical trials using CD19 CAR T cells for MLL-r B-ALL produced complete remission in most patients, relapse with CD19-negative disease was a common mechanism of treatment failure. Whereas CD19neg relapse has been observed across a broad spectrum of B-ALL patients treated with CD19-directed therapy, patients with MLL-r have manifested the emergence of AML, often clonally related to the B-ALL, suggesting that the inherent heterogeneity or lineage plasticity of MLL-r B-ALL may predispose patients to a myeloid relapse. Understanding the factors that enable and drive myeloid relapse may be important to devise strategies to improve durability of remissions. In this review, we summarize clinical observations to date with MLL-r B-ALL and generally discuss lineage plasticity as a mechanism of escape from immunotherapy.

Role of Dot1L and H3K79 methylation in regulating somatic hypermutation of immunoglobulin genes.

Somatic hypermutation (SHM) and class-switch recombination (CSR) of the immunoglobulin (Ig) genes allow B cells to make antibodies that protect us against a wide variety of pathogens. SHM is mediated by activation-induced deaminase (AID), occurs at a million times higher frequency than other mutations in the mammalian genome, and is largely restricted to the variable (V) and switch (S) regions of Ig genes. Using the Ramos human Burkitt's lymphoma cell line, we find that H3K79me2/3 and its methyltransferase Dot1L are more abundant on the V region than on the constant (C) region, which does not undergo mutation. In primary naïve mouse B cells examined ex vivo, the H3K79me2/3 modification appears constitutively in the donor Sµ and is inducible in the recipient Sγ1 upon CSR stimulation. Knockout and inhibition of Dot1L in Ramos cells significantly reduces V region mutation and the abundance of H3K79me2/3 on the V region and is associated with a decrease of polymerase II (Pol II) and its S2 phosphorylated form at the IgH locus. Knockout of Dot1L also decreases the abundance of BRD4 and CDK9 (a subunit of the P-TEFb complex) on the V region, and this is accompanied by decreased nascent transcripts throughout the IgH gene. Treatment with JQ1 (inhibitor of BRD4) or DRB (inhibitor of CDK9) decreases SHM and the abundance of Pol II S2P at the IgH locus. Since all these factors play a role in transcription elongation, our studies reinforce the idea that the chromatin context and dynamics of transcription are critical for SHM.

PP2Cδ Controls the Differentiation and Function of Dendritic Cells Through Regulating the NSD2/mTORC2/ACLY Pathway.

Dendritic cells (DCs) are recognized as a key orchestrator of immune response and homeostasis, deregulation of which may lead to autoimmunity such as experimental autoimmune encephalomyelitis (EAE). Herein we show that the phosphatase PP2Cδ played a pivotal role in regulating DC activation and function, as PP2Cδ ablation caused aberrant maturation, activation, and Th1/Th17-priming of DCs, and hence induced onset of exacerbated EAE. Mechanistically, PP2Cδ restrained the expression of the essential subunit of mTORC2, Rictor, primarily through de-phosphorylating and proteasomal degradation of the methyltransferase NSD2 via CRL4DCAF2 E3 ligase. Loss of PP2Cδ in DCs accordingly sustained activation of the Rictor/mTORC2 pathway and boosted glycolytic and mitochondrial metabolism. Consequently, ATP-citrate lyse (ACLY) was increasingly activated and catalyzed acetyl-CoA for expression of the genes compatible with hyperactivated DCs under PP2Cδ deletion. Collectively, our findings demonstrate that PP2Cδ has an essential role in controlling DCs activation and function, which is critical for prevention of autoimmunity.

The Histone Methyltransferase DOT1L Is Essential for Humoral Immune Responses.

Histone modifiers are essential for the ability of immune cells to reprogram their gene expression during differentiation. The recruitment of the histone methyltransferase DOT1L (disruptor of telomeric silencing 1-like) induces oncogenic gene expression in a subset of B cell leukemias. Despite its importance, its role in the humoral immune system is unclear. Here, we demonstrate that DOT1L is a critical regulator of B cell biology. B cell development is defective in Dot1lf/fMb1Cre/+ mice, culminating in a reduction of peripheral mature B cells. Upon immunization or influenza infection of Dot1lf/fCd23Cre/+ mice, class-switched antibody-secreting cells are significantly attenuated and germinal centers fail to form. Consequently, DOT1L is essential for B cell memory formation. Transcriptome, pathway, and histological analyses identified a role for DOT1L in reprogramming gene expression for appropriate localization of B cells during the initial stage of the response. Together, these results demonstrate an essential role for DOT1L in generating an effective humoral immune response.

Comprehensive exploratory autoantibody profiling in patients with early rheumatoid arthritis treated with methotrexate or tocilizumab.

BACKGROUND: We sought to identify immunoglobin G autoantibodies predictive of early treatment response to methotrexate, the recommended first-line therapy for patients with newly diagnosed rheumatoid arthritis, and to the interleukin-6 receptor inhibitor biologic tocilizumab, initiated as the first disease-modifying anti-rheumatic drug. MATERIALS AND METHODS: In baseline sera of a subset of patients with newly diagnosed rheumatoid arthritis in the U-Act-Early study, selected based on specific responder/non-responder criteria using the Disease Activity Score assessing 28 joints (DAS28) within the first 20 weeks, we measured immunoglobin G antibody reactivity against 463 protein antigens and performed supervised cluster analysis to identify predictive autoantibodies for treatment response. The analysis subset comprised 56 patients in the methotrexate arm (22 responders, 34 non-responders) and 50 patients in the tocilizumab arm (34 responders, 16 non-responders). For comparison, these analyses were also performed in 50 age- and gender-matched healthy controls. RESULTS: Increased reactivity in responders versus non-responders was found in the methotrexate arm against two antigens-DOT1-like histone lysine methyltransferase (p = 0.009) and tropomyosin (p = 0.003)-and in the tocilizumab arm against one antigen-neuro-oncological ventral antigen 2 (p = 0.039). Decreased reactivity was detected against two antigens in the methotrexate arm-G1 to S phase transition 2 (p = 0.023) and the zinc finger protein ZPR1 (p = 0.021). Reactivity against the identified antigens was not statistically significant in either treatment arm for patients with rheumatoid factor-positive versus-negative or anti-cyclic citrullinated test-positive versus test-negative rheumatoid arthritis (p ≥ 0.06). CONCLUSIONS: Comprehensive profiling of baseline sera revealed several novel immunoglobin G autoantibodies associated with early treatment response to methotrexate and to tocilizumab in disease-modifying anti-rheumatic drug-naive patients with rheumatoid arthritis. These findings could eventually yield clinically relevant predictive markers, if corroborated in different patient cohorts, and may facilitate future benefit in personalised healthcare.

Methyltransferase Dot1l preferentially promotes innate IL-6 and IFN-ß production by mediating H3K79me2/3 methylation in macrophages.

Epigenetic modification, including histone modification, precisely controls target gene expression. The posttranscriptional regulation of the innate signaling-triggered production of inflammatory cytokines and type I interferons has been fully elucidated, whereas the roles of histone modification alteration and epigenetic modifiers in regulating inflammatory responses need to be further explored. Di/tri-methylation modifications of histone 3 lysine 79 (H3K79me2/3) have been shown to be associated with gene transcriptional activation. Disruptor of telomeric silencing-1-like (Dot1l) is the only known exclusive H3K79 methyltransferase and regulates the proliferation and differentiation of tumor cells. However, the roles of Dot1l and Dot1l-mediated H3K79 methylation in innate immunity and inflammatory responses remain unclear. Here, we found that H3K79me2/3 modification levels at the Il6 and Ifnb1 promoters, as well as H3K79me2 modification at the Tnfα promoter, were increased in macrophages activated by Toll-like receptor (TLR) ligands or virus infection. The innate signals upregulated Dot1l expression in macrophages and THP1 cells. Dot1l silencing or a Dot1l inhibitor preferentially suppressed the production of IL-6 and interferon (IFN)-ß but not of TNF-α in macrophages and THP1 cells triggered by TLR ligands or virus infection. Dot1l was recruited to the proximal promoter of the Il6 and Ifnb1 but not Tnfα gene and then mediated H3K79me2/3 modification at the Il6 and Ifnb1 promoters, consequently facilitating the transcription and expression of Il6 and Ifnb1. Thus, Dot1l-mediated selective H3K79me2/3 modifications at the Il6 and Ifnb1 promoters are required for the full activation of innate immune responses. This finding adds new insights into the epigenetic regulation of inflammatory responses and pathogenesis of autoimmune diseases.

The DOT1L inhibitor Pinometostat decreases the host-response against infections: Considerations about its use in human therapy.

Patients with acute myeloid leukemia frequently present translocations of MLL gene. Rearrangements of MLL protein (MLL-r) in complexes that contain the histone methyltransferase DOT1L are common, which elicit abnormal methylation of lysine 79 of histone H3 at MLL target genes. Phase 1 clinical studies with pinometostat (EPZ-5676), an inhibitor of DOT1L activity, demonstrated the therapeutic potential for targeting DOT1L in MLL-r leukemia patients. We previously reported that down-regulation of DOT1L increases influenza and vesicular stomatitis virus replication and decreases the antiviral response. Here we show that DOT1L inhibition also reduces Sendai virus-induced innate response and its overexpression decreases influenza virus multiplication, reinforcing the notion of DOT1L controlling viral replication. Accordingly, genes involved in the host innate response against pathogens (RUBICON, TRIM25, BCL3) are deregulated in human lung epithelial cells treated with pinometostat. Concomitantly, deregulation of some of these genes together with that of the MicroRNA let-7B, may account for the beneficial effects of pinometostat treatment in patients with MLL-r involving DOT1L. These results support a possible increased vulnerability to infection in MLL-r leukemia patients undergoing pinometostat treatment. Close follow up of infection should be considered in pinometostat therapy to reduce some severe side effects during the treatment.

Multiparameter flow cytometry applications in the diagnosis of mixed phenotype acute leukemia.

Mixed phenotype acute leukemias (MPALs) represent a rare subgroup of acute leukemias with a poor prognosis. Proper diagnosis and classification of MPAL is extremely important for patients' outcome. Morphology and flow cytometry recognize two types of MPAL: the "bilineal" MPAL with the coexistence of two blast populations of different lineage and truly "biphenotypic" MPAL coexpressing markers of more than one lineage in a homogenous blast population, respectively. The WHO 2008 classification further delineated three categories: associated with t(9;22)/BCR-ABL1 fusion gene, associated with KMT2A (mixed lineage leukemia) rearrangements, and nonotherwise specified. These categories remained unchanged in the WHO2016 update. Molecular studies have further underlined the heterogeneity of MPAL. In this review, rules for the correct assignment of acute leukemia to the MPAL category are discussed, including both flow cytometry and immunohistochemistry on bone marrow or other tissues biopsies. Comparison of the immunophenotypic classification proposals is provided outlining the explorations mandatory for definitive diagnosis. An extensive review of published data summarizes the reported cytogenetic and molecular anomalies. New developments in the understanding of the early stages of hematopoiesis provide clues to the possible etiopathology of these diseases. Finally, current treatment recommendations are summarized and referenced for clinical use, pointing out that allogeneic hematopoietic stem cell transplantation at an early stage should be considered (at least in adult patients). © 2019 International Clinical Cytometry Society.

The Histone Methyltransferase SETDB1 Controls T Helper Cell Lineage Integrity by Repressing Endogenous Retroviruses.

Upon activation, naive CD4+ T cells differentiate into distinct T cell subsets via processes reliant on epigenetically regulated, lineage-specific developmental programs. Here, we examined the function of the histone methyltransferase SETDB1 in T helper (Th) cell differentiation. Setdb1-/- naive CD4+ T cells exhibited exacerbated Th1 priming, and when exposed to a Th1-instructive signal, Setdb1-/- Th2 cells crossed lineage boundaries and acquired a Th1 phenotype. SETDB1 did not directly control Th1 gene promoter activity but relied instead on deposition of the repressive H3K9me3 mark at a restricted and cell-type-specific set of endogenous retroviruses (ERVs) located in the vicinity of genes involved in immune processes. Refined bioinformatic analyses suggest that these retrotransposons regulate Th1 gene cis-regulatory elements or act as Th1 gene enhancers. Thus, H3K9me3 deposition by SETDB1 ensures Th cell lineage integrity by repressing a repertoire of ERVs that have been exapted into cis-regulatory modules to shape and control the Th1 gene network.

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.

Histone methyltransferase MMSET promotes AID-mediated DNA breaks at the donor switch region during class switch recombination.

In B cells, Ig class switch recombination (CSR) is initiated by activation-induced cytidine deaminase (AID), the activity of which leads to DNA double-strand breaks (DSBs) within IgH switch (S) regions. Preferential targeting of AID-mediated DSBs to S sequences is critical for allowing diversification of antibody functions, while minimizing potential off-target oncogenic events. Here, we used gene targeted inactivation of histone methyltransferase (HMT) multiple myeloma SET domain (MMSET) in mouse B cells and the CH12F3 cell line to explore its role in CSR. We find that deletion of MMSET-II, the isoform containing the catalytic SET domain, inhibits CSR without affecting either IgH germline transcription or joining of DSBs within S regions by classical nonhomologous end joining (C-NHEJ). Instead, we find that MMSET-II inactivation leads to decreased AID recruitment and DSBs at the upstream donor Sµ region. Our findings suggest a role for the HMT MMSET in promoting AID-mediated DNA breaks during CSR.

Activation-induced cytidine deaminase targets SUV4-20-mediated histone H4K20 trimethylation to class-switch recombination sites.

Activation-induced cytidine deaminase (AID) triggers antibody diversification in B cells by catalysing deamination and subsequently mutating immunoglobulin (Ig) genes. Association of AID with RNA Pol II and occurrence of epigenetic changes during Ig gene diversification suggest participation of AID in epigenetic regulation. AID is mutated in hyper-IgM type 2 (HIGM2) syndrome. Here, we investigated the potential role of AID in the acquisition of epigenetic changes. We discovered that AID binding to the IgH locus promotes an increase in H4K20me3. In 293F cells, we demonstrate interaction between co-transfected AID and the three SUV4-20 histone H4K20 methyltransferases, and that SUV4-20H1.2, bound to the IgH switch (S) mu site, is replaced by SUV4-20H2 upon AID binding. Analysis of HIGM2 mutants shows that the AID truncated form W68X is impaired to interact with SUV4-20H1.2 and SUV4-20H2 and is unable to bind and target H4K20me3 to the Smu site. We finally show in mouse primary B cells undergoing class-switch recombination (CSR) that AID deficiency associates with decreased H4K20me3 levels at the Smu site. Our results provide a novel link between SUV4-20 enzymes and CSR and offer a new aspect of the interplay between AID and histone modifications in setting the epigenetic status of CSR sites.

Ash1l and lnc-Smad3 coordinate Smad3 locus accessibility to modulate iTreg polarization and T cell autoimmunity.

Regulatory T (Treg) cells are important for the maintenance of immune homoeostasis and prevention of autoimmune diseases. Epigenetic modifications have been reported to modulate autoimmunity by altering Treg cell fate. Here we show that the H3K4 methyltransferase Ash1l facilitates TGF-ß-induced Treg cell polarization in vitro and protects mice from T cell-mediated colitis in vivo. Ash1l upregulates Smad3 expression by directly targeting Smad3 promoter to increase local H3K4 trimethylation. Furthermore, we identify an lncRNA, namely lnc-Smad3, which interacts with the histone deacetylase HDAC1 and silences Smad3 transcription. After TGF-ß stimulation, activated Smad3 suppresses lnc-Smad3 transcription, thereby recovering the Smad3 promoter accessibility to Ash1l. By revealing the opposite regulatory functions of Ash1l and lnc-Smad3 in Smad3 expression, our data provide insights for the epigenetic control of Treg cell fate to potentially aid in the development of therapeutic intervention for autoimmune diseases.

[Preparation and application of rabbit anti-mouse Setd8 polyclonal antibody].

Objective: To purify the recombinant Setd8 protein and prepare rabbit anti-mouse Setd8 polyclonal antibody. Methods: The recombinant plasmid p ET-30a-Setd8 was constructed by double enzyme digestion and linkage,and then transformed into E. coli BL21. The expression of the target protein was induced by IPTG and the expression product was purified by Ni-NTA affinity chromatograph. The purified protein was used to immunize New Zealand white rabbits to produce polyclonal antibody. The titer and specificity of the antibody were identified by ELISA,Western blotting and immunohistochemistry. Results: The prokaryotic expression vector p ET-30a-Setd8 was constructed successfully. After induced by IPTG,the recombinant Setd8 protein was expressed effectively in E. coli BL21. Polyclonal antibody against Setd8 was generated by immunizing rabbits with the routine method. ELISA showed that the titer of rabbit anti-Setd8 antiserum was 1 ∶ 1 000 000.Western blotting demonstrated that the polyclonal antibody could recognize the native mouse Setd8 protein. Immunohistochemistry revealed that Setd8 protein recognized by the polyclonal antibody was mainly distributed in the nucleus of spermatogonia in adult mouse testis. Conclusion: Using the prokaryotic expression vector p ET-30a-Setd8,we have prepared successfully the polyclonal antibody with high affinity and specificity.

G9a regulates group 2 innate lymphoid cell development by repressing the group 3 innate lymphoid cell program.

Innate lymphoid cells (ILCs) are emerging as important regulators of homeostatic and disease-associated immune processes. Despite recent advances in defining the molecular pathways that control development and function of ILCs, the epigenetic mechanisms that regulate ILC biology are unknown. Here, we identify a role for the lysine methyltransferase G9a in regulating ILC2 development and function. Mice with a hematopoietic cell-specific deletion of G9a (Vav.G9a(-/-) mice) have a severe reduction in ILC2s in peripheral sites, associated with impaired development of immature ILC2s in the bone marrow. Accordingly, Vav.G9a(-/-) mice are resistant to the development of allergic lung inflammation. G9a-dependent dimethylation of histone 3 lysine 9 (H3K9me2) is a repressive histone mark that is associated with gene silencing. Genome-wide expression analysis demonstrated that the absence of G9a led to increased expression of ILC3-associated genes in developing ILC2 populations. Further, we found high levels of G9a-dependent H3K9me2 at ILC3-specific genetic loci, demonstrating that G9a-mediated repression of ILC3-associated genes is critical for the optimal development of ILC2s. Together, these results provide the first identification of an epigenetic regulatory mechanism in ILC development and function.

High Glucose Increases the Expression of Inflammatory Cytokine Genes in Macrophages Through H3K9 Methyltransferase Mechanism.

Recent studies suggest that histone modification is one of the mechanisms regulating inflammatory cytokine gene expression in hyperglycemic conditions. However, it remains unknown how histone methylation is initiated and involved in changes of inflammatory cytokine gene expression under high glucose (HG) conditions. Our aim was to investigate whether H3K9 methylation was involved in HG-induced expression of inflammatory cytokines in macrophages. Expression profile of cytokine genes under hyperglycemia in THP-1-derived macrophages was determined by human cytokine antibody array. Based on the results from the human cytokine antibody array analyses, the H3K9me3 levels of 4 inflammatory cytokine genes, including interleukin-6 (IL-6), IL-12p40, macrophage inflammatory protein-1α (MIP-1α), and MIP-1ß under HG were determined by ChIP assays. Furthermore, the expression of these 4 inflammatory cytokine genes under either HG or chaetocin (an inhibitor of SUV39H1 methyltransferase) exposure or overexpression of SUV39H1 (a H3K9me3-specific methyltransferase) was analyzed by quantitative polymerase chain reaction. Macrophages cultured in HG conditions showed increased gene expression and decreased H3K9me3 levels of inflammatory cytokine genes compared with macrophages incubated in normal glucose (NG) culture. Inhibition of SUV39H1 with chaetocin in NG-treated macrophages also increased the expression of IL-6, IL-12p40, MIP-1α, and MIP-1ß. Furthermore, inhibition of SUV39H1 with chaetocin in HG-treated macrophages further increased the expression of these inflammatory cytokines. Contrarily, NG-treated macrophages transfected with SUV39H1 plasmids show decreased expression of inflammatory cytokines. Furthermore, overexpression of SUV39H1 in HG-treated macrophages alleviated the expression of inflammatory cytokines under HG conditions. Finally, HG also increases the expression of inflammation cytokines in mouse bone marrow-derived macrophages. Our data demonstrated that HG increases the expression of inflammatory cytokines in macrophages through decreased H3K9me3 levels, which was partly mediated by SUV39H1. Dysregulation of epigenetic histone modification may be one of the underlying mechanisms for HG-induced inflammatory cytokine expression in macrophages.

Inhibition of EHMT2 Induces a Robust Antiviral Response Against Foot-and-Mouth Disease and Vesicular Stomatitis Virus Infections in Bovine Cells.

The genetic regulatory network controlling the innate immune system is well understood in many species. However, the role of the epigenetic mechanisms underlying the expression of immunoregulatory genes is less clear, especially in livestock species. Histone H3 lysine 9 dimethylation (H3K9me2) is an epigenetic modification associated with transcriptional silencing within the euchromatin regions. Euchromatic histone-lysine N-methyltransferase 2 (EHMT2; also known as G9a) is a crucial enzyme responsible for regulating the dynamics of this epigenetic modification. It has been shown that histone modifications play a role in regulating type I interferon (IFN) response. In the present study, we investigated the role of EHMT2 in the epigenetic regulation of bovine antiviral innate immunity and explored its therapeutic potential against viral infections. We evaluated the effects of pharmacological and RNAi-mediated inhibition of EHMT2 on the transcription of IFN-ß and other IFN-inducible antiviral genes, as well as its effect on foot-and-mouth disease virus (FMDV) and vesicular stomatitis virus (VSV) replication in bovine cells. We show that treatment of primary bovine cells with the synthetic EHMT2 inhibitor (UNC0638) either before or shortly after virus infection resulted in a significant increase in transcript levels of bovine IFN-ß (boIFN-ß; 300-fold) and other IFN-inducible genes, including IFN-stimulated gene 15 (ISG-15), myxovirus resistance 1 (Mx-1), Mx-2, RIG-I, 2',5'-oligoadenylate synthetase 1 (OAS-1), and protein kinase R (PKR). Expression of these factors correlated with a significant decrease in VSV and FMDV viral titers. Our data confirm the involvement of EHMT2 in the epigenetic regulation of boIFN-ß and demonstrate the activation of a general antiviral state after EHMT2 inhibition.

Epigenetic regulation of IL-12-dependent T cell proliferation.

It is well established that the cytokine IL-12 and the transcription factor STAT4, an essential part of the IL-12 signaling pathway, are critical components of the Th1 differentiation process in T cells. In response to pathogenic stimuli, this process causes T cells to proliferate rapidly and secrete high amounts of the cytokine IFN-γ, leading to the Th1 proinflammatory phenotype. However, there are still unknown components of this differentiation pathway. We here demonstrated that the expression of the histone methyltransferase Mll1 is driven by IL-12 signaling through STAT4 in humans and mice and is critical for the proper differentiation of a naïve T cell to a Th1 cell. Once MLL1 is up-regulated by IL-12, it regulates the proliferation of Th1 cells. As evidence of this, we show that Th1 cells from Mll1(+/-) mice are unable to proliferate rapidly in a Th1 environment in vitro and in vivo. Additionally, upon restimulation with cognate antigen Mll1(+/-), T cells do not convert to a Th1 phenotype, as characterized by IFN-γ output. Furthermore, we observed a reduction in IFN-γ production and proliferation in human peripheral blood stimulated with tetanus toxoid by use of a specific inhibitor of the MLL1/menin complex. Together, our results demonstrate that the MLL1 gene plays a previously unrecognized but essential role in Th1 cell biology and furthermore, describes a novel pathway through which Mll1 expression is regulated.