Schnurri-2 controls memory Th1 and Th2 cell numbers in vivo

Yoda1, a Piezo1 agonist, induced latent HIV reactivation associated with upregulation of CD3/TCR complex and HLA genes

There is currently no cure for HIV because of the presence of latent viral reservoirs in people with HIV (PWH) on antiretroviral therapy (ART). Latency-reversing agents (LRAs) that can effectively reactivate and destroy latent HIV are being developed as a possible cure for HIV. Here, we identify Yoda1, a Piezo1 agonist, as a novel LRA. Yoda1 reactivated latent HIV in vitro ACH2 cells and ex vivo PBMCs from an HIV patient on ART. Yoda1 induced infectious virus production and HIV gene expression via Piezo1 activation and calcium signaling. Transcriptomic and proteomic analyses revealed a unique latent HIV reactivation pathway involving T cell activation, upregulation of TCR/CD3 and HLA genes, as well as modulation of host and viral transcription and translation that favors viral gene expression. These findings suggest further testing and development of Yoda1 as an effective LRA to reactivate latent HIV and destroy latent reservoirs for the cure of HIV.

Schnurri 3 promotes Th2 cytokine production during the late phase of T-cell antigen stimulation

Th1 and Th2 polarization is determined by the coordination of numerous factors including the affinity and strength of the antigen-receptor interaction, predominant cytokine environment, and costimulatory molecules present. Here, we show that Schnurri (SHN) proteins have distinct roles in Th1 and Th2 polarization. SHN2 was previously found to block the induction of GATA3 and Th2 differentiation. We found that, in contrast to SHN2, SHN3 is critical for IL-4 production and Th2 polarization. Strength of stimulation controls SHN2 and SHN3 expression patterns, where higher doses of antigen receptor stimulation promoted SHN3 expression and IL-4 production, along with repression of SHN2 expression. SHN3-deficient T cells showed a substantial defect in IL-4 production and expression of AP-1 components, particularly c-Jun and Jun B. This loss of early IL-4 production led to reduced GATA3 expression and impaired Th2 differentiation. Together, these findings uncover SHN3 as a novel, critical regulator of Th2 development.

Costimulation molecules differentially regulate the ERK-Zfp831 axis to shape T follicular helper cell differentiation

T follicular helper (Tfh) cells play essential roles in regulating humoral immunity, especially germinal center reactions. However, how CD4⁺ T cells integrate the antigenic and costimulatory signals in Tfh cell development is still poorly understood. Here, we found that phorbol 12-myristate 13-acetate (PMA) + ionomycin (P+I) stimulation, together with interleukin-6 (IL-6), potently induce Tfh cell-like transcriptomic programs in vitro. The ERK kinase pathway was attenuated under P+I stimulation; ERK2 inhibition enhanced Tfh cell development in vitro and in vivo. We observed that inducible T cell costimulator (ICOS), but not CD28, lacked the ability to activate ERK, which was important in sustaining Tfh cell development. The transcription factor Zfp831, whose expression was repressed by ERK, promoted Tfh cell differentiation by directly upregulating the expression of the transcription factors Bcl6 and Tcf7. We have hence identified an ERK-Zfp831 axis, regulated by costimulation signaling, in critical regulation of Tfh cell development.

Functional CRISPR dissection of gene networks controlling human regulatory T cell identity

Human regulatory T (T_reg) cells are essential for immune homeostasis. The transcription factor (TF) FOXP3 maintains T_reg cell identity, yet the complete set of key TFs that control T_reg cell gene expression remains unknown. Here, we used pooled and arrayed Cas9 ribonucleoprotein (RNP) screens to identify TFs that regulate critical proteins in primary human T_reg cells under basal and pro-inflammatory conditions. We then generated 54,424 single-cell transcriptomes from T_reg cells subjected to genetic perturbations and cytokine stimulation, which revealed distinct gene networks individually regulated by FOXP3 and PRDM1, in addition to a network co-regulated by FOXO1 and IRF4. We also discovered that HIVEP2, not previously implicated in T_reg cell function, co-regulates another gene network with SATB1 and is important for T_reg cell-mediated immunosuppression. By integrating CRISPR screens and scRNA-seq profiling, we have uncovered novel transcriptional regulators and downstream gene networks in human T_reg cells that could be targeted for immunotherapies.

Immature morphological properties in subcellular-scale structures in the dentate gyrus of Schnurri-2 knockout mice: a model for schizophrenia and intellectual disability

Accumulating evidence suggests that subcellular-scale structures such as dendritic spine and mitochondria may be involved in the pathogenesis/pathophysiology of schizophrenia and intellectual disability. Previously, we proposed mice lacking Schnurri-2 (Shn2; also called major histocompatibility complex [MHC]-binding protein 2 [MBP-2], or human immunodeficiency virus type I enhancer binding protein 2 [HIVEP2]) as a schizophrenia and intellectual disability model with mild chronic inflammation. In the mutants’ brains, there are increases in C4b and C1q genes, which are considered to mediate synapse elimination during postnatal development. However, morphological properties of subcellular-scale structures such as dendritic spine in Shn2 knockout (KO) mice remain unknown. In this study, we conducted three-dimensional morphological analyses in subcellular-scale structures in dentate gyrus granule cells of Shn2 KO mice by serial block-face scanning electron microscopy. Shn2 KO mice showed immature dendritic spine morphology characterized by increases in spine length and decreases in spine diameter. There was a non-significant tendency toward decrease in spine density of Shn2 KO mice over wild-type mice, and spine volume was indistinguishable between genotypes. Shn2 KO mice exhibited a significant reduction in GluR1 expression and a nominally significant decrease in SV2 expression, while PSD95 expression had a non-significant tendency to decrease in Shn2 KO mice. There were significant decreases in dendrite diameter, nuclear volume, and the number of constricted mitochondria in the mutants. Additionally, neuronal density was elevated in Shn2 KO mice. These results suggest that Shn2 KO mice serve as a unique tool for investigating morphological abnormalities of subcellular-scale structures in schizophrenia, intellectual disability, and its related disorders.

Effect of inhaled and systemic glucocorticoid treatment on CD4+ regulatory and effector T cells in a mouse model of allergic asthma

To achieve a better understanding of mechanisms underlying the anti-asthmatic action of inhaled and systemic glucocorticoids (GCs) and to provide more data regarding the risk of a negative effect of inhaled GCs on CD4⁺ T cells, a study was conducted on the effect of ciclesonide and methylprednisolone on CD4⁺ effector (Teff), regulatory (Treg) and resting (Trest) T cells within respiratory and extra-respiratory tissues in a mouse model of allergic asthma. The study indicated that one, and possibly a key mechanism, underlying the anti-asthmatic action of inhaled and systemic GCs is the prevention of the activation and clonal expansion of CD4⁺ Teff cells in the mediastinal lymph nodes (MLNs), which consequently prevents infiltration of the lungs with CD4⁺ Teff cells. The beneficial effects of GCs in asthma treatment were not mediated through increased recruitment of Treg cells into the MLNs and lungs and/or local generation of Treg cells. The results demonstrated that inhaled and systemic GCs induced comparable depletion of normal CD4⁺ Teff, Trest and Treg cells in the MLNs, head and neck lymph nodes and peripheral blood. Furthermore, inhaled, but not systemic GC therapy, led to the loss of these cells in the lungs. Thus, the study suggests that inhaled GC therapy may not be safer at all than systemic one with respect to the adverse effect on CD4⁺ T cells present within and outside the respiratory tract. Moreover, administration of inhaled GCs can produce negative effects on lung-residing CD4⁺ T cells.

A possible serologic biomarker for maternal immune activation-associated neurodevelopmental disorders found in the rat models

Epidemiological studies have shown that maternal infection during early pregnancy increases the risk of neurodevelopmental disorders (i.e., schizophrenia or autism) in offspring. Recently, diagnostic/stratification biomarkers for the maternal immune activation background in patients with neurodevelopmental disorders have been energetically searched for in the patient blood. Here, we report a novel serologic marker candidate for the disorders found in the maternal immune activation (MIA) rat model. Serum proteome analysis of the MIA rat showed that the immunoglobulin (Ig) light chain is reproducibly augmented. The Ig light chain in sera takes two forms - free form or bound to the Ig heavy chain. Only the former is an inflammatory disease marker, but pro-inflammatory cytokine levels in the sera of the MIA rats were below detectable limits of the ELISA protocol we used. We thereby carried out serum assays of Ig light chains and pro-inflammatory cytokines of commercially available schizophrenia patient sera for research. Although the number of samples was limited, we found augmentation of free Ig light chains but not pro-inflammatory cytokines in sporadic schizophrenia patient sera. Our findings suggest that Ig light chain assay of the schizophrenia/autism patient sera would be worthy to be validated in larger scale.

IκB kinase β inhibitor, IMD-0354, prevents allergic asthma in a mouse model through inhibition of CD4(+) effector T cell responses in the lung-draining mediastinal lymph nodes

IκB kinase (IKK) is important for nuclear factor (NF)-κB activation under inflammatory conditions. It has been demonstrated that IMD-0354, i.e. a selective inhibitor of IKKβ, inhibited allergic inflammation in a mouse model of ovalbumin (OVA)-induced asthma. The present study attempts to shed light on the involvement of CD4(+) effector (Teff) and regulatory (Treg) T cells in the anti-asthmatic action of IMD-0354. The animals were divided into three groups: vehicle treated, PBS-sensitized/challenged mice (PBS group); vehicle treated, OVA-sensitized/challenged mice (OVA group); and IMD-0354-treated, OVA-sensitized/challenged mice. The analyzed parameters included the absolute counts of Treg cells (Foxp3(+)CD25(+)CD4(+)), activated Teff cells (Foxp3(-)CD25(+)CD4(+)) and resting T cells (CD25(-)CD4(+)) in the mediastinal lymph nodes (MLNs), lungs and peripheral blood. Moreover, lung histopathology was performed to evaluate lung inflammation. It was found that the absolute number of cells in all studied subsets was considerably increased in the MLNs and lungs of mice from OVA group as compared to PBS group. All of these effects were fully prevented by treatment with IMD-0354. Histopathological examination showed that treatment with IMD-0354 protected the lungs from OVA-induced allergic airway inflammation. Our results indicate that IMD-0354 exerts anti-asthmatic action, at least partially, by blocking the activation and clonal expansion of CD4(+) Teff cells in the MLNs, which, consequently, prevents infiltration of the lungs with activated CD4(+) Teff cells. The beneficial effects of IMD-0354 in a mouse model of asthma are not mediated through increased recruitment of Treg cells into the MLNs and lungs and/or local generation of inducible Treg cells.

T Cell Transcription Factors and Their Impact on HIV Expression

By targeting CD4⁺ effector T cells, HIV has a dramatic impact on the depletion, expansion and function of the different polarized T cell subsets. The maturation of T cell lineages is in part driven by intrinsic transcription factors that potentially influence how efficiently HIV replicates. In this review, we explore whether transcription factors that are required for polarizing T cells influence HIV replication. In particular, we examine provirus transcription as well as the establishment and maintenance of HIV latency. Furthermore, it is suggested these factors may provide novel cell-specific therapeutic strategies for targeting the HIV latent reservoir.

Deficiency of schnurri-2, an MHC enhancer binding protein, induces mild chronic inflammation in the brain and confers molecular, neuronal, and behavioral phenotypes related to schizophrenia

Schnurri-2 (Shn-2), an nuclear factor-κB site-binding protein, tightly binds to the enhancers of major histocompatibility complex class I genes and inflammatory cytokines, which have been shown to harbor common variant single-nucleotide polymorphisms associated with schizophrenia. Although genes related to immunity are implicated in schizophrenia, there has been no study showing that their mutation or knockout (KO) results in schizophrenia. Here, we show that Shn-2 KO mice have behavioral abnormalities that resemble those of schizophrenics. The mutant brain demonstrated multiple schizophrenia-related phenotypes, including transcriptome/proteome changes similar to those of postmortem schizophrenia patients, decreased parvalbumin and GAD67 levels, increased theta power on electroencephalograms, and a thinner cortex. Dentate gyrus granule cells failed to mature in mutants, a previously proposed endophenotype of schizophrenia. Shn-2 KO mice also exhibited mild chronic inflammation of the brain, as evidenced by increased inflammation markers (including GFAP and NADH/NADPH oxidase p22 phox), and genome-wide gene expression patterns similar to various inflammatory conditions. Chronic administration of anti-inflammatory drugs reduced hippocampal GFAP expression, and reversed deficits in working memory and nest-building behaviors in Shn-2 KO mice. These results suggest that genetically induced changes in immune system can be a predisposing factor in schizophrenia.

Immature dentate gyrus: an endophenotype of neuropsychiatric disorders

Adequate maturation of neurons and their integration into the hippocampal circuit is crucial for normal cognitive function and emotional behavior, and disruption of this process could cause disturbances in mental health. Previous reports have shown that mice heterozygous for a null mutation in α -CaMKII, which encodes a key synaptic plasticity molecule, display abnormal behaviors related to schizophrenia and other psychiatric disorders. In these mutants, almost all neurons in the dentate gyrus are arrested at a pseudoimmature state at the molecular and electrophysiological levels, a phenomenon defined as "immature dentate gyrus (iDG)." To date, the iDG phenotype and shared behavioral abnormalities (including working memory deficit and hyperlocomotor activity) have been discovered in Schnurri-2 knockout, mutant SNAP-25 knock-in, and forebrain-specific calcineurin knockout mice. In addition, both chronic fluoxetine treatment and pilocarpine-induced seizures reverse the neuronal maturation, resulting in the iDG phenotype in wild-type mice. Importantly, an iDG-like phenomenon was observed in post-mortem analysis of brains from patients with schizophrenia/bipolar disorder. Based on these observations, we proposed that the iDG is a potential endophenotype shared by certain types of neuropsychiatric disorders. This review summarizes recent data describing this phenotype and discusses the data's potential implication in elucidating the pathophysiology of neuropsychiatric disorders.

CLIC4 and Schnurri-2: a dynamic duo in TGF-beta signaling with broader implications in cellular homeostasis and disease

CLIC4 is a highly conserved, multifunctional member of the chloride intracellular channel family of proteins. The protein is largely cytoplasmic but translocates to the nucleus upon a variety of stimuli including TGF-beta, TNF-alpha and etoposide. Nuclear resident CLIC4 causes growth arrest, terminal differentiation and apoptosis. Recently, it was discovered that TGF-beta causes CLIC4 to associate with Schnurri-2 and together they translocate to the nucleus and dissociate thereafter. The nuclear function of CLIC4 was further illuminated by the discovery that CLIC4 enhances TGF-beta signaling by associating with phospho-Smad2 and 3 and preventing their dephosphorylation. Enhanced TGF-beta dependent gene expression and growth inhibition are downstream consequences of this activity of CLIC4. In this article, we speculate on other consequences of the CLIC4 relation to TGF-beta signaling and the potential for CLIC4 to participate in other cellular functions related to normal homeostasis and disease.

Dampening of death pathways by schnurri-2 is essential for T-cell development

Generation of a diverse and self-tolerant T cell repertoire requires appropriate interpretation of T cell receptor (TCR) signals by CD4⁺CD8⁺ double positive (DP) thymocytes. Thymocyte cell fate is dictated by the nature of TCR:MHC-peptide interactions, with signals of higher strength leading to death (negative selection) and signals of intermediate strength leading to differentiation (positive selection)1. Molecules that regulate T cell development by modulating TCR signal strength have been described but components that specifically define the boundaries between positive and negative selection remain unknown. Here we show that repression of TCR-induced death pathways is critical for proper interpretation of positive selecting signals in vivo, and identify Schnurri2 (Shn2) as a crucial death dampener. Our results indicate that Shn2^−/− DP thymocytes inappropriately undergo negative selection in response to positive selecting signals, thus leading to disrupted T cell development. Shn2^−/− DP thymocytes are more sensitive to TCR-induced death in vitro and die in response to positive selection interactions in vivo. However, Shn2-deficient thymocytes can be positively selected when TCR-induced death is genetically-ablated. Shn2 levels increase after TCR stimulation suggesting that integration of multiple TCR:MHC-peptide interactions may fine tune the death threshold. Mechanistically, Shn2 functions downstream of TCR proximal signaling compenents to dampen Bax activation and the mitochondrial death pathway. Our findings uncover a critical regulator of T cell development that controls the balance between death and differentiation.

Schnurri-2 deficiency counteracts against bone loss induced by ovariectomy

Schnurri (Shn)-2 is a transcriptional modulator of bone formation and bone resorption and its deficiency causes low turnover state with higher cancellous bone mass due to the defects in osteoclasts that exceeds the defects in osteoblasts in mice. We addressed whether such low turnover of bone remodeling in Shn2 deficiency may be modulated in the absence of estrogen that induces high turnover state in vivo. Ovariectomy reduced bone mass in wild type compared to sham operated control mice and such reduction in bone mass was also observed in Shn2 deficient mice. However, due to the high levels of basal bone mass in Shn2 deficient mice, the bone mass levels after ovariectomy were still comparable to sham operated wild-type mice. Analysis indicated that estrogen depletion increased bone resorption at similar levels in wild type and Shn2 deficient mice though the basal levels of osteoclast number was slightly lower in Shn2-deficient mice. In contrast, basal levels of bone marrow cell mineralization in cultures were low in Shn2-deficeint mice while estrogen depletion increased the mineralization levels to those that were comparable to sham wild type. This indicates that Shn2-deficient mice maintain bone mass at the levels comparable to wild-type sham mice even after ovariectomy-induced bone loss and this correlates with the high levels of mineralization activity in bone marrow cells after ovariectomy.

Uncoupling of growth plate maturation and bone formation in mice lacking both Schnurri-2 and Schnurri-3

Formation and remodeling of the skeleton relies on precise temporal and spatial regulation of genes expressed in cartilage and bone cells. Debilitating diseases of the skeletal system occur when mutations arise that disrupt these intricate genetic regulatory programs. Here, we report that mice bearing parallel null mutations in the adapter proteins Schnurri2 (Shn2) and Schnurri3 (Shn3) exhibit defects in patterning of the axial skeleton during embryogenesis. Postnatally, these compound mutant mice develop a unique osteochondrodysplasia. The deletion of Shn2 and Shn3 impairs growth plate maturation during endochondral ossification but simultaneously results in massively elevated trabecular bone formation. Hence, growth plate maturation and bone formation can be uncoupled under certain circumstances. These unexpected findings demonstrate that both unique and redundant functions reside in the Schnurri protein family that are required for proper skeletal patterning and remodeling.

Naringenin chalcone suppresses allergic asthma by inhibiting the type-2 function of CD4 T cells

BACKGROUND

Some polyphenols possess anti-allergic activities. Naringenin chalcone is one of the polyphenols that is present in the skin of red tomatoes. In this study, we investigated the effect of naringenin chalcone in allergic responses in vivo using an experimental mouse model system of allergic asthma.

METHODS

Allergic airway inflammation was induced in mice by sensitization and challenge with ovalbumin. Naringenin chalcone was orally administrated every day during the course of the experiment. Airway hyperreactivity, the eosinophilic infiltration in the bronchioalveolar lavage fluid and Th2 cytokine production from splenic CD4 T cells were assessed.

RESULTS

Eosinophilic airway inflammation, airway hyperreactivity and Th2 cytokine production from CD4 T cells were significantly suppressed in mice that were treated with naringenin chalcone. Hyperproduction of mucus was slightly reduced.

CONCLUSIONS

The results of this study suggest that naringenin chalcone suppresses asthmatic symptoms by inhibiting Th2 cytokine production from CD4 T cells. Thus, naringenin chalcone may be a useful supplement for the suppression of allergic symptoms in humans.

Enhanced Th2 cell differentiation and allergen-induced airway inflammation in Zfp35-deficient mice

Studies of human asthma and of animal models of allergic airway inflammation revealed a crucial role for Th2 cells in the pathogenesis of allergic asthma. Kruppel-type zinc finger proteins are the largest family of a regulatory transcription factor for cellular development and function. Zinc finger protein (Zfp) 35 is an 18-zinc finger motif-containing Kruppel-type zinc finger protein, while its function remains largely unknown. The aim of this study was to clarify the role of Zfp35 in the pathogenesis of Th2-dependent allergic inflammation, such as allergic asthma. We examined airway eosinophilic inflammation and hyperresponsiveness in two mouse models, which use our newly generated Zfp35-deficient (Zfp35(-/-)) mice and adoptive transfer of cells. In Zfp35(-/-) mice, Th2 cell differentiation, Th2 cytokine production, eosinophilic inflammation, and airway hyperresponsiveness were substantially enhanced. Furthermore, adoptive transfer of Ag-sensitized Zfp35(-/-) CD4 T cells into the asthmatic mice resulted in enhanced airway inflammation and airway hyperresponsiveness. These results indicate that Zfp35 controls Th2 cell differentiation, allergic airway inflammation, and airway hyperresponsiveness in a negative manner. Thus, Zfp35 may control Th2-dependent diseases, such as allergic asthma.

Regulation of bone formation and immune cell development by Schnurri proteins

Although identified over a decade ago, the function and physiological significance of the mammalian Schnurri protein family remained largely unknown. However, the recent generation and characterization of mice bearing null mutations in the individual Schnurri genes has led to the discovery of unexpected yet central roles for these large zinc-finger proteins in several biological processes. Here, we review findings of these studies and discuss the importance of the Schnurri protein family in regulating both the immune and skeletal systems.

Initiation and maintenance of Th2 cell identity

T helper type 2 (Th2) cells produce IL-4, IL-5, and IL-13 and play an important role in humoral immunity and allergic reactions. During Th2 cell differentiation, naïve CD4 T cells acquire 'Th2 cell identity', that is, the capability to produce selectively a large amount of Th2 cytokines. Th2 cell identity is maintained in memory Th2 cells. Significant advances in understanding of the molecular requirement for these processes have been made. The expression of GATA3, a master transcription factor for Th2 cell differentiation, is uniquely regulated by several distinct mechanisms. Molecular analyses of memory Th2 cells revealed that cell survival and the maintenance of Th2 cell function are epigenetically regulated by various nuclear factors, including Polycomb and Trithorax molecules.

Primer: making sense of T-cell memory

Protective memory is a key property of the immune system. Pathogen-associated molecular patterns of invading organisms deliver signals to pattern-recognition receptors that activate the innate immune system. Ligation of the T-cell receptor by peptides bound to MHC antigens and presented by dendritic cells, together with signals produced by the activated innate immune system, initiate T-cell responses. The nature of the T-cell response, consisting of phases of clonal expansion and contraction, and differentiation to effector and memory cells, however, is determined both by the properties of the antigen and the co-stimuli produced by the innate immune system. Short-lived effector and longer-lived memory T cells are generated during primary responses; after the death of most of the effectors, memory cells remain. Memory cells are heterogeneous in phenotype and function; subsets include the relatively quiescent central and more activated effector memory cells, as well as cells able to promote inflammation, help antibody production or regulate other immune responses. Understanding the properties of memory cells will help in the rational design of vaccines for 'difficult' organisms or cancer, as well as immunotherapies for autoimmune diseases.