Cutting edge: Identification of an alternative GATA-3 promoter directing tissue-specific gene expression in mouse and human

Pharmacogenomic and epigenomic approaches to untangle the enigma of IL-10 blockade in oncology

The host immune system status remains an unresolved mystery among several malignancies. An immune-compromised state or smart immune-surveillance tactics orchestrated by cancer cells are the primary cause of cancer invasion and metastasis. Taking a closer look at the tumour-immune microenvironment, a complex network and crosstalk between infiltrating immune cells and cancer cells mediated by cytokines, chemokines, exosomal mediators and shed ligands are present. Cytokines such as interleukins can influence all components of the tumour microenvironment (TME), consequently promoting or suppressing tumour invasion based on their secreting source. Interleukin-10 (IL-10) is an interlocked cytokine that has been associated with several types of malignancies and proved to have paradoxical effects. IL-10 has multiple functions on cellular and non-cellular components within the TME. In this review, the authors shed the light on the regulatory role of IL-10 in the TME of several malignant contexts. Moreover, detailed epigenomic and pharmacogenomic approaches for the regulation of IL-10 were presented and discussed.

Differential regulation of lineage-determining transcription factor expression in innate lymphoid cell and adaptive T helper cell subsets

CD4 T helper (Th) cell subsets, including Th1, Th2 and Th17 cells, and their innate counterparts innate lymphoid cell (ILC) subsets consisting of ILC1s, ILC2s and ILC3s, display similar effector cytokine-producing capabilities during pro-inflammatory immune responses. These lymphoid cell subsets utilize the same set of lineage-determining transcription factors (LDTFs) for their differentiation, development and functions. The distinct ontogeny and developmental niches between Th cells and ILCs indicate that they may adopt different external signals for the induction of LDTF during lineage commitment. Increasing evidence demonstrates that many conserved cis-regulatory elements at the gene loci of LDTFs are often preferentially utilized for the induction of LDTF expression during Th cell differentiation and ILC development at different stages. In this review, we discuss the functions of lineage-related cis-regulatory elements in inducing T-bet, GATA3 or RORγt expression based on the genetic evidence provided in recent publications. We also review and compare the upstream signals involved in LDTF induction in Th cells and ILCs both in vitro and in vivo. Finally, we discuss the possible mechanisms and physiological importance of regulating LDTF dynamic expression during ILC development and activation.

Whole-genome profiling of DNA methylation and hydroxymethylation identifies distinct regulatory programs among innate lymphocytes

Innate lymphocytes encompass a diverse array of phenotypic identities with specialized functions. DNA methylation and hydroxymethylation are essential for epigenetic fidelity and fate commitment. The landscapes of these modifications are unknown in innate lymphocytes. Here, we characterized the whole-genome distribution of methyl-CpG and 5-hydroxymethylcytosine in mouse ILC3, ILC2, and NK cells. We identified differentially methylated and hydroxymethylated DNA regions between ILC-NK subsets and correlated them with transcriptional signatures. We associated lineage-determining transcription factors with demethylation and demonstrated unique patterns of DNA methylation/hydroxymethylation in relationship to open chromatin regions, histone modifications, and transcription factor binding sites. We further discovered a novel association between hydroxymethylation and NK cell super-enhancers. Using mice lacking DNA hydroxymethylase TET2, we showed its requirement for optimal production of hallmark cytokines by ILC3 and IL-17A by inflammatory ILC2. These findings provide a powerful resource for studying innate lymphocyte epigenetic regulation and decode the regulatory logic governing their identity.

Gata3 Silencing Is Involved in Neuronal Differentiation and Its Abnormal Expression Impedes Neural Activity in Adult Retinal Neurocytes

GATA binding protein 3 (Gata3), a zinc-finger transcription factor, plays an important role in neural development. However, its expression and bioactivity in the retina remain unclear. In the present study, our data indicated that Gata3 maintains the precursor state of 661W cells, and Gata3 silencing induces cell differentiation. The expression of Nestin, a marker of precursor cells, was significantly decreased in parallel, whereas the expression of Map2, a marker of differentiated neurons, was significantly increased following the decrease in Gata3. Neurite outgrowth was increased by 2.78-fold in Gata3-silenced cells. Moreover, Gata3 expression generally paralleled that of Nestin in developing mouse retinas. Both Gata3 and Nestin were expressed in the retina at postnatal day 1 and silenced in the adult mouse retina. Exogenous Gata3 significantly inhibited the neural activity of primary retinal neurocytes (postnatal day 1) by decreasing synaptophysin levels, neurite outgrowth, and cell viability. Furthermore, in vivo, exogenous Gata3 significantly induced apoptosis and the contraction of retinal outlay filaments and decreased the a- and b-waves in adult mouse intravitreal injected with AAV-Re-Gata3-T2A-GFP. Thus, Gata3 silencing promotes neuronal differentiation and neurite outgrowth. Its abnormal expression impedes neural activity in adult retinal neurocytes. This study provides new insights into Gata3 bioactivity in retinal neurocytes.

Dynamic regulation of chromatin organizer SATB1 via TCR-induced alternative promoter switch during T-cell development

The chromatin organizer SATB1 is highly enriched in thymocytes and is essential for T-cell development. Although SATB1 regulates a large number of genes important for T-cell development, the mechanism(s) regulating expression of SATB1 during this process remain elusive. Using chromatin immune precipitation-seq-based occupancy profiles of H3K4me3 and H3Kme1 at Satb1 gene locus, we predicted four different alternative promoters of Satb1 in mouse thymocytes and characterized them. The expression of Satb1 transcript variants with distinct 5′ UTRs occurs in a stage-specific manner during T-cell development and is dependent on TCR signaling. The observed discrepancy between the expression levels of SATB1 mRNA and protein in developing thymocytes can be explained by the differential translatability of Satb1 transcript variants as confirmed by polysome profiling and in vitro translation assay. We show that Satb1 alternative promoters exhibit lineage-specific chromatin accessibility during T-cell development from progenitors. Furthermore, TCF1 regulates the Satb1 P2 promoter switch during CD4SP development, via direct binding to the Satb1 P2 promoter. CD4SP T cells from TCF1 KO mice exhibit downregulation of P2 transcript variant expression as well as low levels of SATB1 protein. Collectively, these results provide unequivocal evidence toward alternative promoter switch-mediated developmental stage-specific regulation of SATB1 in thymocytes.

NK-4 exerts selective regulatory effects on the activation and function of allergy-related Th2 cells

NK-4 is the main component of the antiallergic drug Lumin, which has been in popular usage since the early 1950s. In this study, we examined whether NK-4 exerts a regulatory effect on the activation and effector function of Th2 cells. NK-4 inhibited IL-4 production by anti-CD3ε mAb-stimulated BALB/c mouse spleen cells, whereas NK-4 had little effect on IFN-γ production. IL-4 and IL-5 secretion by anti-CD3ε mAb- or antigen-stimulated Th2 cells (D10.G4.1) was abrogated by NK-4 without affecting cell numbers, whereas IFN-γ secretion by activated Th1 cells was unchanged. Mechanistic analysis revealed that NK-4 inhibited mRNA expression of the Th2-associated transcription factors GATA-3 and NFATc1 in anti-CD3ε mAb-stimulated D10.G4.1 cells. Regarding the regulation of Th2 cell effector functions, NK-4 inhibited the secretion of eotaxin and thymus and activation-regulated chemokine (TARC) by normal human dermal fibroblasts in response to IL-4 and/or TNF-α. NK-4 achieved TARC attenuation comparable to what is observed with suplatast tosilate, an antiallergic drug that selectively inhibits Th2 cytokine production, at 14-fold lower concentrations of suplatast tosilate. Dexamethasone increased TARC production by 2.2- to 2.6-fold of control cultures. NK-4 successfully inhibited the STAT6 signaling pathway, suggesting a potential mechanism for down-regulating chemokines expression. In addition, NK-4 abrogated IL-4-driven modulation of cytokine production profile in human monocytic THP-1 cells from proinflammatory to anti-inflammatory response, as seen in the inverted ratio of TNF-α to IL-10 produced in response to LPS. These results suggest that NK-4 could prevent IL-4-driven polarization to alternatively activated macrophages, which are proposed to have pathogenic roles in allergic asthma. The importance of Th2 cytokines and chemokines in the development and progression of type 2 inflammatory disorders has been highlighted by recent advance in our understanding the immunological mechanism underlying allergic disease. Our results support the use of NK-4 as a reasonable therapeutic option to alleviate Th2-mediated allergic inflammation.

Staphylococcal enterotoxin A-activated regulatory T cells promote allergen-specific TH2 response to intratracheal allergen inoculation

BACKGROUND

T_H2 responses are implicated in asthma pathobiology. Epidemiologic studies have found a positive association between asthma and exposure to staphylococcal enterotoxins.

OBJECTIVE

We used a mouse model of asthma to determine whether staphylococcal enterotoxins promote T_H2 differentiation of allergen-specific CD4 conventional T (Tcon) cells and asthma by activating allergen-nonspecific regulatory T (Treg) cells to create a T_H2-polarizing cytokine milieu.

METHODS

Ovalbumin (OVA)-specific, staphylococcal enterotoxin A (SEA)-nonreactive naive CD4 Tcon cells were cocultured with SEA-reactive allergen-nonspecific Treg or CD4 Tcon cells in the presence of OVA and SEA. The OVA-specific CD4 T cells were then analyzed for IL-13 and IFN-γ expression. SEA-activated Treg cells were analyzed for the expression of the T_H2-polarizing cytokine IL-4 and the T-cell activation markers CD69 and CD62L. For asthma induction, mice were intratracheally sensitized with OVA or cat dander extract (CDE) alone or together with SEA and then challenged with OVA or CDE. Mice were also subject to transient Treg cell depletion before sensitization with OVA plus SEA. Asthma features and T_H2 differentiation in these mice were analyzed.

RESULTS

SEA-activated Treg cells induced IL-13 but suppressed IFN-γ expression in OVA-specific CD4 Tcon cells. SEA-activated Treg cells expressed IL-4, upregulated CD69, and downregulated CD62L. Sensitization with OVA plus SEA but not OVA alone induced asthma, and SEA exacerbated asthma induced by CDE. Depletion of Treg cells abolished these effects of SEA and IL-13 expression in OVA-specific T cells.

CONCLUSION

SEA promoted T_H2 responses of allergen-specific T cells and asthma pathogenesis by activating Treg cells.

Regulation of IL-4 Expression in Immunity and Diseases

IL-4 was first identified as a T cell-derived growth factor for B cells. Studies over the past several decades have markedly expanded our understanding of its cellular sources and function. In addition to T cells, IL-4 is produced by innate lymphocytes, such as NTK cells, and myeloid cells, such as basophils and mast cells. It is a signature cytokine of type 2 immune response but also has a nonimmune function. Its expression is tightly regulated at several levels, including signaling pathways, transcription factors, epigenetic modifications, microRNA, and long noncoding RNA. This chapter will review in detail the molecular mechanism regulating the cell type-specific expression of IL-4 in physiological and pathological type 2 immune responses.

PU.1 Suppresses Th2 Cytokine Expression via Silencing of GATA3 Transcription in Dendritic Cells

The transcription factor PU.1 is predominantly expressed in dendritic cells (DCs) and is essential for DC differentiation. Although there are several reports that PU.1 positively regulates the expression of DC-specific genes, whether PU.1 also has a suppressive effect on DCs is largely unknown. Here we demonstrate that PU.1 suppresses the expression of Th2 cytokines including IL-13 and IL-5 in bone marrow-derived DCs (BMDCs), through repression of the expression of GATA3, which is a master regulator of Th2 differentiations. When PU.1 siRNA was introduced into BMDCs, LPS-induced expression of IL-13 and IL-5 was increased along with upregulation of the constitutive expression of GATA2 and GATA3. The additional introduction of GATA3 siRNA but not of GATA2 siRNA abrogated PU.1 siRNA-mediated upregulation of IL-13 and IL-5. A chromatin immunoprecipitation assay showed that PU.1 bound to Gata3 proximal promoter region, which is more dominant than the distal promoter in driving GATA3 transcription in DCs. The degree of histone acetylation at the Gata3 promoter was decreased in PU.1 siRNA-introduced DCs, suggesting the involvement of PU.1 in chromatin modification of the Gata3 promoter. Treatment with a histone deacetylase (HDAC) inhibitor, trichostatin A, increased the degree of histone H3 acetylation at the Gata3 promoter and induced the subsequent expression of GATA3. Experiments using HDAC inhibitors and siRNAs showed that HDAC3 suppressed GATA3 expression. The recruitment of HDAC3 to the Gata3 promoter was decreased by PU.1 knockdown. LPS-induced IL-13 expression was dramatically reduced in BMDCs generated from mice lacking the conserved GATA3 response element, termed CGRE, which is an essential site for the binding of GATA3 on the Il-13 promoter. The degree of H3K4me3 at CGRE was significantly increased in PU.1 siRNA-transfected stimulated DCs. Our results indicate that PU.1 plays pivotal roles in DC development and function, serving not only as a transcriptional activator but also as a repressor.

Essential role of GATA3 in regulation of differentiation and cell proliferation in SK-N-SH neuroblastoma cells

Neuroblastoma is a common solid malignant tumor of the sympathetic nervous system, which contributes to 15% of cancer‑related mortality in children. The differentiation status of neuroblastoma is correlated with clinical outcome, and the induction of differentiation thus constitutes a therapeutic approach in this disease. However, the molecular mechanisms that control the differentiation of neuroblastoma remain poorly understood. The present study aimed to define whether GATA3 is involved in the differentiation of neuroblastoma cells. The results demonstrated that GATA3 is a prognostic marker for survival in patients with neuroblastoma, and that high‑level GATA3 expression is associated with increased self‑renewal and proliferation of neuroblastoma cells. Retinoic acid treatment led to GATA3 downregulation together with neuronal differentiation, suppression of cell proliferation and inhibition of tumorigenecity in neuroblastoma cells. These findings suggest that GATA3 is a key regulator of neuroblastoma differentiation, and provide a novel potential therapeutic strategy for the induction of neuroblastoma differentiation.

Nuclear factor of activated T cells regulates the expression of interleukin-4 in Th2 cells in an all-or-none fashion

Th2 memory lymphocytes have imprinted their Il4 genes epigenetically for expression in dependence of T cell receptor restimulation. However, in a given restimulation, not all Th cells with a memory for IL-4 expression express IL-4. Here, we show that in reactivated Th2 cells, the transcription factors NFATc2, NF-kB p65, c-Maf, p300, Brg1, STAT6, and GATA-3 assemble at the Il4 promoter in Th2 cells expressing IL-4 but not in Th2 cells not expressing it. NFATc2 is critical for assembly of this transcription factor complex. Because NFATc2 translocation into the nucleus occurs in an all-or-none fashion, dependent on complete dephosphorylation by calcineurin, NFATc2 controls the frequencies of cells reexpressing Il4, translates analog differences in T cell receptor stimulation into a digital decision for Il4 reexpression, and instructs all reexpressing cells to express the same amount of IL-4. This analog-to-digital conversion may be critical for the immune system to respond to low concentrations of antigens.

Human Th2 but not Th9 cells release IL-31 in a STAT6/NF-κB-dependent way

IL-31, a member of the IL-6 protein family, is one of the latest additions to the list of T cell-derived cytokines. Th2 cells are regarded as a main source of IL-31, which is produced in response to stimulation by IL-4. Because the development of Th9 cells also requires IL-4 as a polarizing cytokine, the current study investigates IL-31 production in human Th9 cells compared with Th2 cells. We found that, although Th9 cells were able to release IL-31 during the first weeks of in vitro polarization, no IL-31 was detected in Th9 cultures after a final restimulation in the absence of polarizing cytokines. We further show that TGF-β, which is required to obtain Th9 cells in vitro, potently inhibits the release of IL-31 from Th2 cells, whereas IL-33, a cytokine associated with Th2-mediated inflammation, synergizes with IL-4 in inducing IL-31 secretion. To analyze the molecular mechanisms underlying the induction of IL-31, EMSAs, reporter gene assays, and small interfering RNA-based silencing experiments were carried out. We show that STAT6 and NF-κB are central players in mediating IL-31 expression induced by IL-4/IL-33. In addition, we identified a novel NF-κB-binding element within the Il31 promoter that mediates the enhancing effects of IL-33 on IL-4/STAT6-induced IL-31 expression in human Th2 cells. Taken together, this study shows that IL-4 is essential for the production of IL-31, whereas TGF-β significantly suppresses IL-31 expression at the mRNA and protein levels. As a consequence, in vitro polarized Th2 cells, but not Th9 cells, are able to release IL-31.

IFN-α suppresses GATA3 transcription from a distal exon and promotes H3K27 trimethylation of the CNS-1 enhancer in human Th2 cells

CD4(+) Th2 development is regulated by the zinc finger transcription factor GATA3. Once induced by acute priming signals, such as IL-4, GATA3 poises the Th2 cytokine locus for rapid activation and establishes a positive-feedback loop that maintains elevated GATA3 expression. Type I IFN (IFN-α/β) inhibits Th2 cells by blocking the expression of GATA3 during Th2 development and in fully committed Th2 cells. In this study, we uncovered a unique mechanism by which IFN-α/β signaling represses the GATA3 gene in human Th2 cells. IFN-α/β suppressed expression of GATA3 mRNA that was transcribed from an alternative distal upstream exon (1A). This suppression was not mediated through DNA methylation, but rather by histone modifications localized to a conserved noncoding sequence (CNS-1) upstream of exon 1A. IFN-α/β treatment led to a closed conformation of CNS-1, as assessed by DNase I hypersensitivity, along with enhanced accumulation of H3K27me3 mark at this CNS region, which correlated with increased density of total nucleosomes at this putative enhancer. Consequently, accessibility of CNS-1 to GATA3 DNA binding activity was reduced in response to IFN-α/β signaling, even in the presence of IL-4. Thus, IFN-α/β disrupts the GATA3-autoactivation loop and promotes epigenetic silencing of a Th2-specific regulatory region within the GATA3 gene.

GATA4 autoregulates its own expression in mouse gonadal cells via its distal 1b promoter

Transcription factor GATA4 is required for the development and function of the mammalian gonads. We first reported that the GATA4 gene in both human and rodents is expressed as two major alternative transcripts that differ solely in their first untranslated exon (exon 1a vs. exon 1b). We had also showed by quantitative PCR that in mouse tissues, both Gata4 exon 1a- and 1b-containing transcripts are present in all sites that are normally positive for GATA4 protein. In adult tissues, exon 1a-containing transcripts generally predominate. A notable exception, however, is the testis where the Gata4 exon 1a and 1b transcripts exhibit a similar level of expression. We now confirm by in situ hybridization analysis that each transcript is also strongly expressed during gonad differentiation in both sexes in the rat. To gain further insights into how Gata4 gene expression is controlled, we characterized the mouse Gata4 promoter sequence located upstream of exon 1b. In vitro studies revealed that the Gata4 1b promoter is less active than the 1a promoter in several gonadal cell lines tested. Whereas we have previously shown that endogenous Gata4 transcription driven by the 1a promoter is dependent on a proximally located Ebox motif, we now show using complementary in vitro and in vivo approaches that Gata4 promoter 1b-directed expression is regulated by GATA4 itself. Thus, Gata4 transcription in the gonads and other tissues is ensured by distinct promoters that are regulated differentially and independently.

Linking GATA-3 and interleukin-13: implications in asthma

INTRODUCTION

Asthma is one of the serious global health problems and cause of huge mortality and morbidity. It is characterized by persistent airway inflammation, airway hyperresponsiveness, increased IgE levels and mucus hypersecretion. Asthma is mediated by dominant Th2 immune response, causing enhanced expression of Th2 cytokines. These cytokines are responsible for the various pathological changes associated with allergic asthma.

MATERIALS AND METHODS

The role of Th2 cells in the pathogenesis of the asthma is primarily mediated through the cytokine IL-13, also produced by type 2 innate lymphoid cells, that comes under the transcriptional regulation of GATA3. In this review we will try to explore the link between IL-13 and GATA3 in the progression and regulation of asthma and its possible role as a therapeutic target.

CONCLUSION

Inhibition of GATA3 activity or blockade of GATA3 expression may attenuate the interleukin-13 mediated asthma phenotypes. So, GATA3 might be a potential therapeutic target for the treatment of allergic asthma.

Diverting T helper cell trafficking through increased plasticity attenuates autoimmune encephalomyelitis

Naive T helper cells differentiate into functionally distinct effector subsets that drive specialized immune responses. Recent studies indicate that some of the effector subsets have plasticity. Here, we used an EAE model and found that Th17 cells deficient in the transcription factor BCL11B upregulated the Th2-associated proteins GATA3 and IL-4 without decreasing RAR-related orphan receptor γ (RORγt), IL-17, and GM-CSF levels. Surprisingly, abnormal IL-4 production affected Th17 cell trafficking, diverting migration from the draining lymph nodes/CNS route to the mesenteric lymph nodes/gut route, which ameliorated EAE without overt colitis. T helper cell rerouting in EAE was dependent on IL-4, which enhanced retinoic acid (RA) production by dendritic cells, which further induced expression of gut-homing receptors CCR9 and α4β7 on Bcl11b-deficient CD4+ T cells. Furthermore, IL-4 treatment or Th2 immunization of wild-type mice with EAE caused no alteration in Th17 cytokines or RORγt, but diverted T helper cell trafficking to the gut, which improved EAE outcome without overt colitis. Our data demonstrate that Th17 cells are permissive to Th2 gene expression without affecting Th17 gene expression. This Th17 plasticity has an impact on trafficking, which is a critical component of the immune response and may represent a possible avenue for treating multiple sclerosis.

'All things considered': transcriptional regulation of T helper type 2 cell differentiation from precursor to effector activation

T helper type 2 (Th2) cells are critical to host defence against helminth infection and the pathogenesis of allergic diseases. The differentiation of Th2 cells from naive CD4 T cells is controlled by intricate transcriptional mechanisms. At the precursor stage of naive CD4 T cells, transcriptional mechanisms maintain the potential and in the meantime prevent spontaneous differentiation to Th2 fate. In addition, intrachromosomal interactions important for co-ordinated expression of Th2 cytokines pre-exist in naive CD4 T cells. Upon T-cell receptor (TCR) engagement, naive CD4 T cells are induced by polarizing signals of the interleukin-4/Stat6 and Jagged/Notch pathways to up-regulate the expression of GATA-3. Once up-regulated, GATA-3 drives Th2 and suppresses Th1 differentiation in a cell autonomous fashion. In this stage of differentiation, the Th2 cytokine locus, as well as the interferon-γ locus, undergoes chromatin remodelling and epigenetic modifications that contribute to the somatic memory of Th2 cytokine gene expression pattern. Once differentiated, Th2 effector cells promptly produce Th2 cytokines upon TCR stimulation, which is regulated by concerted actions of GATA-3, TCR signalling, enhancers and the Th2 locus control region. This review provides a detailed account of the transcriptional regulatory events at these different stages of Th2 differentiation.

Stemness of T cells and the hematopoietic stem cells: fate, memory, niche, cytokines

Stem cells are able to generate both cells that differentiate and cells that remain undifferentiated but potentially have the same developmental program. The prolonged duration of the protective immune memory for infectious diseases such as polio, small pox, and measles, suggested that memory T cells may have stem cell properties. Understanding the molecular basis for the life-long persistence of memory T cells may be useful to project targeted therapies for immune deficiencies and infectious diseases and to formulate vaccines. In the last decade evidence from different laboratories shows that memory T cells may share self-renewal pathways with bone marrow hematopoietic stem cells. In stem cells the intrinsic self-renewal activity, which depends on gene expression, is known to be modulated by extrinsic signals from the environment that may be tissue specific. These extrinsic signals for stemness of memory T cells include cytokines such as IL-7 and IL-15 and there are other cytokine signals for maintaining the cytokine signature (TH1, TH2, etc.) of memory T cells. Intrinsic and extrinsic pathways that might be common to bone marrow hematopoietic stem cells and memory T lymphocytes are discussed and related to self-renewal functions.

Tissue-derived hedgehog proteins modulate Th differentiation and disease

Genome-wide association studies of complex immune-mediated diseases have indicated that many genetic factors, each with individual low risk, contribute to overall disease. It is therefore timely and important to characterize how immune responses may be subtly modified by tissue context. In this article, we explore the role of tissue-derived molecules in influencing the function of T cells, which, owing to their migratory nature, come into contact with many different microenvironments through their lifespan. Hedgehog (Hh) proteins act as secreted morphogens, providing concentration-dependent positional and temporal cell-fate specification in solid tissues. Hh signaling is required for embryogenesis and is important in postnatal tissue renewal and in malignancy. However, the function of Hh in dynamic, fluid systems, such as in mammalian immunity, is largely unknown. In this article, we show that Hh-dependent transcription in T cells promoted Th2 transcriptional programs and differentiation, exacerbating allergic disease. Of interest, expression of Sonic Hh increased in lung epithelial cells following the induction of allergic disease, and lung T cells upregulated Hh target gene expression, indicating that T cells respond to locally secreted Hh ligands in vivo. We show that Il4, the key Th2 cytokine, is a novel transcriptional target of Hh signals in T cells, providing one mechanism for the role of Hh in Th differentiation. We propose that Hh, secreted from inflamed, remodeling, or malignant tissue, can modulate local T cell function. Our data present an unexpected and novel role for tissue-derived morphogens in the regulation of fluid immune responses, with implications for allergy and tumor responses, suggesting new uses for anti-Hh therapeutics.

E2A transcription factors limit expression of Gata3 to facilitate T lymphocyte lineage commitment

The E2A transcription factors promote the development of thymus-seeding cells, but it remains unknown whether these proteins play a role in T lymphocyte lineage specification or commitment. Here, we showed that E2A proteins were required to promote T-lymphocyte commitment from DN2 thymocytes and to extinguish their potential for alternative fates. E2A proteins functioned in DN2 cells to limit expression of Gata3, which encodes an essential T-lymphocyte transcription factor whose ectopic expression can arrest T-cell differentiation. Genetic, or small interfering RNA-mediated, reduction of Gata3 rescued T-cell differentiation in the absence of E2A and restricted the development of alternative lineages by limiting the expanded self-renewal potential in E2A−/− DN2 cells. Our data support a novel paradigm in lymphocyte lineage commitment in which the E2A proteins are necessary to limit the expression of an essential lineage specification and commitment factor to restrain self-renewal and to prevent an arrest in differentiation.

STAT6-dependent and -independent mechanisms in Th2 polarization

Th2 cells play a key role in directing immune responses against helminths. Additionally, Th2 cells are crucial for many types of allergic reactions. Whereas the molecular mechanisms underlying the differentiation of other types of Th cells are well understood, Th2 differentiation is still a controversial topic. IL-4 and its downstream transcription factor signal transducer and activator of transcription (STAT)6 are well-known key mediators in Th2 differentiation. The fact that Th2 cells themselves are the most potent source of IL-4 suggests that additional mechanisms promoting the initiation of Th2 differentiation exist. This article gives an overview on STAT6-dependent and -independent mechanisms involved in the process of Th2 polarization, including Notch, mTORC2, IL-2/STAT5, and Wnt. Furthermore, we emphasize the role of STAT6 not only as a transcriptional activator promoting Th2 development, but also in fine-tuning alternative signaling pathways which are involved in the initiation of Th2 polarization.

The role of Notch in the differentiation of CD4⁺ T helper cells

CD4⁺ T helper cells are playing critical roles in host defense to pathogens and in the maintenance of immune homeostasis. Naïve CD4⁺T cells, upon antigen-specific recognition, receive signals to differentiate into distinct effector T helper cell subsets characterized by their pattern of cytokine production and specific immune functions. A tight balance between these different subsets ensures proper control of the immune response. There is increasing evidence revealing an important role for Notch signaling in the regulation of CD4⁺T helper cell differentiation or function in the periphery. However, the exact mechanisms involved remain unclear and appear contradictory. In this review, we summarize current knowledge and discuss recent advances in the field to reconcile different views on the role of Notch signaling in the differentiation of functional T helper subsets.

The role of the GATA2 transcription factor in normal and malignant hematopoiesis

Hematopoiesis involves an elaborate regulatory network of transcription factors that coordinates the expression of multiple downstream genes, and maintains homeostasis within the hematopoietic system through the accurate orchestration of cellular proliferation, differentiation and survival. As a result, defects in the expression levels or the activity of these transcription factors are intimately linked to hematopoietic disorders, including leukemia. The GATA family of nuclear regulatory proteins serves as a prototype for the action of lineage-restricted transcription factors. GATA1 and GATA2 are expressed principally in hematopoietic lineages, and have essential roles in the development of multiple hematopoietic cells, including erythrocytes and megakaryocytes. Moreover, GATA2 is crucial for the proliferation and maintenance of hematopoietic stem cells and multipotential progenitors. In this review, we summarize the current knowledge regarding the biological properties and functions of the GATA2 transcription factor in normal and malignant hematopoiesis.

From the cradle to the grave: activities of GATA-3 throughout T-cell development and differentiation

GATA family transcription factors play multiple vital roles in hematopoiesis in many cell lineages, and in particular, T cells require GATA-3 for execution of several developmental steps. Transcriptional activation of the Gata3 gene is observed throughout T-cell development and differentiation in a stage-specific fashion. GATA-3 has been described as a master regulator of T-helper 2 (Th2) cell differentiation in mature CD4(+) T cells. During T-cell development in the thymus, its roles in the CD4 versus CD8 lineage choice and at the β-selection checkpoint are the best characterized. In contrast, its importance prior to β-selection has been obscured both by the developmental heterogeneity of double negative (DN) 1 thymocytes and the paucity of early T-lineage progenitors (ETPs), a subpopulation of DN1 cells that contains the most immature thymic progenitors that retain potent T-lineage developmental potential. By examining multiple lines of in vivo evidence procured through the analysis of Gata3 mutant mice, we have recently demonstrated that GATA-3 is additionally required at the earliest stage of thymopoiesis for the development of the ETP population. Here, we review the characterized functions of GATA-3 at each stage of T-cell development and discuss hypothetical molecular pathways that mediate these functions.

E proteins and the regulation of early lymphocyte development

Lymphopoiesis generates mature B, T, and NK lymphocytes from hematopoietic stem cells via a series of increasingly restricted developmental intermediates. The transcriptional networks that regulate these fate choices are composed of both common and lineage-specific components, which combine to create a cellular context that informs the developmental response to external signals. E proteins are an important factor during lymphopoiesis, and E2A in particular is required for normal T- and B-cell development. Although the other E proteins, HEB and E2-2, are expressed during lymphopoiesis and can compensate for some of E2A's activity, E2A proteins have non-redundant functions during early T-cell development and at multiple checkpoints throughout B lymphopoiesis. More recently, a role for E2A has been demonstrated in the generation of lymphoid-primed multipotent progenitors and shown to favor their specification toward lymphoid over myeloid lineages. This review summarizes both our current understanding of the wide-ranging functions of E proteins during the development of adaptive lymphocytes and the novel functions of E2A in orchestrating a lymphoid-biased cellular context in early multipotent progenitors.

An NK and T cell enhancer lies 280 kilobase pairs 3' to the gata3 structural gene

Transcription factor GATA-3 is vital for multiple stages of T cell and natural killer (NK) cell development, and yet the factors that directly regulate Gata3 transcription during hematopoiesis are only marginally defined. Here, we show that neither of the Gata3 promoters, previously implicated in its tissue-specific regulation, is alone capable of directing Gata3 transcription in T lymphocytes. In contrast, by surveying large swaths of DNA surrounding the Gata3 locus, we located a cis element that can recapitulate aspects of the Gata3-dependent T cell regulatory program in vivo. This element, located 280 kbp 3' to the structural gene, directs both T cell- and NK cell-specific transcription in vivo but harbors no other tissue activity. This novel, distant element regulates multiple major developmental stages that require GATA-3 activity.

Regulation of GATA-3 expression during CD4 lineage differentiation

GATA-3 is necessary for the development of MHC class II-restricted CD4 T cells, and its expression is increased during positive selection of these cells. TCR signals drive this upregulation, but the signaling pathways that control this process are not well understood. Using genetic and pharmacological approaches, we show that GATA-3 upregulation during thymocyte-positive selection is the result of additive inputs from the Ras/MAPK and calcineurin pathways. This upregulation requires the presence of the transcription factor c-Myb. Furthermore, we show that TH-POK can also upregulate GATA-3 in double-positive thymocytes, suggesting the existence of a positive feedback loop that contributes to lock in the initial commitment to the CD4 lineage during differentiation.

Inhibition of suppressive T cell factor 1 (TCF-1) isoforms in naive CD4+ T cells is mediated by IL-4/STAT6 signaling

The Wnt pathway transcription factor T cell factor 1 (TCF-1) plays essential roles in the control of several developmental processes, including T cell development in the thymus. Although previously regarded as being required only during early T cell development, recent studies demonstrate an important role for TCF-1 in T helper 2 (Th2) cell polarization. TCF-1 was shown to activate expression of the Th2 transcription factor GATA-binding protein 3 (GATA3) and thus to promote the development of IL-4-producing Th2 cells independent of STAT6 signaling. In this study, we show that TCF-1 is down-regulated in human naive CD4(+) T cells cultured under Th2-polarizing conditions. The down-regulation is largely due to the polarizing cytokine IL-4 because IL-4 alone is sufficient to substantially inhibit TCF-1 expression. The IL-4-induced suppression of TCF-1 is mediated by STAT6, as shown by electrophoretic mobility shift assays, chromatin immunoprecipitation, and STAT6 knockdown experiments. Moreover, we found that IL-4/STAT6 predominantly inhibits the shorter, dominant-negative TCF-1 isoforms, which were reported to inhibit IL-4 transcription. Thus, this study provides a model for an IL-4/STAT6-dependent fine tuning mechanism of TCF-1-driven T helper cell polarization.

TCF1 and beta-catenin regulate T cell development and function

T cell factor-1 (TCF1) critically regulates T cell development. However, signals that control TCF1 function in developing and mature T cells remain unknown. TCF1 along with beta-catenin activates gene transcription and in cooperation with Groucho family of proteins mediates gene repression. It has been established that the beta-catenin-dependent gene expression is often downstream of the canonical Wnt signaling pathway. We have genetically manipulated the beta-catenin gene and generated mutant mice that have shown an essential role for beta-catenin and TCF1 during pre-T cell receptor (TCR) and TCR-dependent stages of T cell development. We have also demonstrated a function for TCF1 and beta-catenin downstream of TCR signaling in the differentiation of mature CD4 T cells into T helper lineages.

STAT6-mediated displacement of polycomb by trithorax complex establishes long-term maintenance of GATA3 expression in T helper type 2 cells

Polycomb group (PcG) and trithorax group (TrxG) complexes exert opposing effects on the maintenance of the transcriptional status of the developmentally regulated Hox genes. In this study, we show that activation of STAT6 induces displacement of the PcG complex by the TrxG complex at the upstream region of the gene encoding GATA3, a transcription factor essential for T helper type 2 (Th2) cell differentiation. Once Th2 cells differentiate, TrxG complex associated with the TrxG component Menin binds to the whole GATA3 gene locus, and this binding is required for the long-term maintenance of expression of GATA3 and Th2 cytokine. Thus, STAT6-mediated displacement of PcG by the TrxG complex establishes subsequent STAT6-independent maintenance of GATA3 expression in Th2 cells via the recruitment of the Menin-TrxG complex.

Candidate molecular pathway genes related to appetite regulatory neural network, adipocyte homeostasis and obesity: results from the CARDIA Study

Appetite regulatory neural network and adipocyte homeostasis molecular pathways are critical to long-term weight maintenance. Associations between obesity-related phenotypes and four genes in these pathways - leptin (LEP), leptin receptor (LEPR), neuropeptide Y2 receptor (NPY2R) and peptide YY (PYY) were examined in CARDIA Study participants (aged 18-30 at recruitment in 1985-6). Weight, BMI and waist circumference were measured at baseline and at years 2, 5, 7, 10, 15, and 20. Genotyping was conducted using tag SNPs characterising common genetic variations in these genes. Generalized estimating equation (GEE) models estimated associations between SNPs and repeated anthropometric measurements, controlling for sex and age. False discovery rate was used to adjust for multiple testing. In African-Americans, SNPs across the LEP gene demonstrated significant overall associations with all obesity-related phenotypes. The associations between LEP rs17151919 with weight tended to strengthen with time - the difference in weight associated with each additional minor allele increased from 2.6 kg at baseline to 4.8 kg at year 20 (SNP*time interaction p = 0.0193). NPY2R gene SNPs were associated with waist circumference among African-American men (p = 0.0462). In Caucasians, LEP SNPs also tended to be associated with weight (p = 0.0471), and PYY rs11684664 was associated with obesity-related phenotypes in women only (p = 0.010-0.026). Several LEP, and NPY2R and PYY SNPs were associated with obesity-related phenotypes in young adults, particularly among African-Americans.

Increased levels of NOTCH1, NF-kappaB, and other interconnected transcription factors characterize primitive sets of hematopoietic stem cells

As previously shown, higher levels of NOTCH1 and increased NF-kappaB signaling is a distinctive feature of the more primitive umbilical cord blood (UCB) CD34+ hematopoietic stem cells (HSCs), as compared to bone marrow (BM). Differences between BM and UCB cell composition also account for this finding. The CD133 marker defines a more primitive cell subset among CD34+ HSC with a proposed hemangioblast potential. To further evaluate the molecular basis related to the more primitive characteristics of UCB and CD133+ HSC, immunomagnetically purified human CD34+ and CD133+ cells from BM and UCB were used on gene expression microarrays studies. UCB CD34+ cells contained a significantly higher proportion of CD133+ cells than BM (70% and 40%, respectively). Cluster analysis showed that BM CD133+ cells grouped with the UCB cells (CD133+ and CD34+) rather than to BM CD34+ cells. Compared with CD34+ cells, CD133+ had a higher expression of many transcription factors (TFs). Promoter analysis on all these TF genes revealed a significantly higher frequency (than expected by chance) of NF-kappaB-binding sites (BS), including potentially novel NF-kappaB targets such as RUNX1, GATA3, and USF1. Selected transcripts of TF related to primitive hematopoiesis and self-renewal, such as RUNX1, GATA3, USF1, TAL1, HOXA9, HOXB4, NOTCH1, RELB, and NFKB2 were evaluated by real-time PCR and were all significantly positively correlated. Taken together, our data indicate the existence of an interconnected transcriptional network characterized by higher levels of NOTCH1, NF-kappaB, and other important TFs on more primitive HSC sets.

TCR-dependent translational control of GATA-3 enhances Th2 differentiation

The differentiation of CD4(+) T cells into the Th2 subset is controlled by the transcription factor GATA-3. GATA-3 is both necessary and sufficient for Th2 differentiation and works through the induction of chromatin remodeling at the Th2 effector cytokine loci. We show in this study that IL-4 stimulation induces GATA-3 mRNA upregulation, but the level of GATA-3 protein induced is insufficient for Th2 differentiation. The levels of GATA-3 protein and Th2 differentiation are enhanced by concomitant TCR signaling through the PI3K/mammalian target of rapamycin pathway. The PI3K-mediated increase in GATA-3 protein occurs without increasing the GATA-3 mRNA level. Rather, TCR signaling through PI3K specifically enhances the translation rate of GATA-3 without affecting the protein stability. Importantly, this role of TCR signaling is independent of the effects of TCR signaling in T cell survival and expansion. Thus, TCR signaling through PI3K may play a critical role in Th2 differentiation by the specific enhancement of GATA-3 translation.

c-Myb, Menin, GATA-3, and MLL form a dynamic transcription complex that plays a pivotal role in human T helper type 2 cell development

GATA-3 and c-Myb are core elements of a transcriptionally active complex essential for human Th2 cell development and maintenance. We report herein mechanistic details concerning the role of these transcription factors in human peripheral blood Th2 cell development. Silencing c-Myb in normal human naive CD4(+) cells under Th2 cell-promoting conditions blocked up-regulation of GATA-3 and interleukin-4, and in effector/memory CD4(+) T cells, decreased expression of GATA-3 and Th2 cytokines. In primary T cells, c-Myb allows GATA-3 to autoactivate its own expression, an event that requires the direct interaction of c-Myb and GATA-3 on their respective binding sites in promoter of GATA-3. Immunoprecipitation revealed that the c-Myb/GATA-3 complex contained Menin and mixed lineage leukemia (MLL). MLL recruitment into the c-Myb-GATA-3-Menin complex was associated with the formation Th2 memory cells. That MLL-driven epigenetic changes were mechanistically important for this transition was suggested by the fact that silencing c-Myb significantly decreased the methylation of histone H3K4 and the acetylation of histone H3K9 at the GATA-3 locus in developing Th2 and CD4(+) effector/memory cells. Therefore, c-Myb, GATA-3, and Menin form a core transcription complex that regulates GATA-3 expression and, with the recruitment of MLL, Th2 cell maturation in primary human peripheral blood T cells.

Conserved usage of alternative 5' untranslated exons of the GATA4 gene

BACKGROUND

GATA4 is an essential transcription factor required for the development and function of multiple organs. Despite this important role, our knowledge of how the GATA4 gene is regulated remains limited. To better understand this regulation, we characterized the 5' region of the mouse, rat, and human GATA4 genes.

METHODOLOGY/PRINCIPAL FINDINGS

Using 5' RACE, we identified novel transcription start sites in all three species. GATA4 is expressed as multiple transcripts with varying 5' ends encoded by alternative untranslated first exons. Two of these non-coding first exons are conserved between species: exon 1a located 3.5 kb upstream of the GATA4 ATG site in exon 2, and a second first exon (exon 1b) located 28 kb further upstream. Expression of both mRNA variants was found in all GATA4-expressing organs but with a preference for the exon 1a-containing transcript. The exception was the testis where exon 1a- and 1b-containing transcripts were similarly expressed. In some tissues such as the intestine, alternative transcript expression appears to be regionally regulated. Polysome analysis suggests that both mRNA variants contribute to GATA4 protein synthesis.

CONCLUSIONS/SIGNIFICANCE

Taken together, our results indicate that the GATA4 gene closely resembles the other GATA family members in terms of gene structure where alternative first exon usage appears to be an important mechanism for regulating its tissue- and cell-specific expression.

Alternative promoter and GATA5 transcripts in mouse

GATA5 is a member of the GATA zinc finger transcription factor family involved in tissue-specific transcriptional regulation during cell differentiation and embryogenesis. Previous reports indicate that null mutation of the zebrafish GATA5 gene results in embryonic lethality, whereas deletion of exon 1 from the mouse GATA5 gene causes only derangement of female urogenital development. Here, we have identified an alternate promoter within intron 1 of the mouse GATA5 gene that transcribes a 2.5-kb mRNA that lacks exon 1 entirely but includes 82 bp from intron 1 and all of exons 2-6. The alternative promoter was active during transient transfection in cultured airway myocytes and bronchial epithelial cells, and it drove reporter gene expression in gastric epithelial cells in transgenic mice. The 2.5-kb alternative transcript encodes an NH(2)-terminally truncated "short GATA5" comprising aa 226-404 with a single zinc finger, which retains ability to transactivate the atrial natriuretic factor promoter (albeit less efficiently than full-length GATA5). Another new GATA5 transcript contains all of exons 1-5 and the 5' portion of exon 6 but lacks the terminal 1143 bp of the 3'-untranslated region from exon 6. These findings extend current understanding of the tissue distribution of GATA5 expression and suggests that GATA5 expression and function are more complex than previously appreciated.

Gata4 and Gata5 cooperatively regulate cardiac myocyte proliferation in mice

GATA5 is a member of the zinc finger transcription factor GATA family (GATA1-6) that plays a wide variety of roles in embryonic and adult development. Experiments in multiple model systems have emphasized the importance of the GATA family members 4-6 in the development of the endoderm and mesoderm. Yet despite overlapping expression patterns, there is little evidence of an important role for GATA5 in mammalian cardiac development. We have generated a new Gata5 mutant allele lacking exons 2 and 3 that encodes both zinc finger domains (Gata5(tm)(2)(Eem)), and we show that although Gata5(-/-) mice are viable, Gata4(+/-)5(-/-) mutants die at mid-gestation and exhibit profound cardiovascular defects, including abnormalities of cardiomyocyte proliferation and cardiac chamber maturation. These results demonstrate functional redundancy between Gata4 and Gata5 during cardiac development and implicate Gata5 as a candidate modifier gene for congenital heart disease.

GATA3 is selectively expressed in the trophectoderm of peri-implantation embryo and directly regulates Cdx2 gene expression

During early mammalian development, genesis of the first two cell lineages, inner cell mass (ICM) and trophectoderm (TE), is dependent upon functions of key transcription factors that are expressed in a regulated and spatially restricted fashion. In this study, we demonstrate that during early mouse development, mRNA expression of transcription factor GATA3 is induced at the 4-cell stage and is consistently present during pre-implantation embryonic development. Interestingly, at the blastocyst stage, Gata3 mRNA is selectively up-regulated within the TE lineage, and GATA3 protein is abundantly present only in the TE but not in the ICM. Using mouse trophoblast stem cells (TS cells) as a model, we found that, knockdown of GATA3 by RNA interference (RNAi) down-regulates expression of caudal-type homeobox 2 (CDX2), a key regulator of the TE lineage. Chromatin immunoprecipitation (ChIP) analyses revealed that, in TS cells, GATA3 directly regulates Cdx2 transcription from a conserved GATA motif at the intron 1 region of the Cdx2 locus. ChIP analyses with mouse blastocysts also detected GATA3 occupancy at intron 1 of the Cdx2 locus. In addition, down-regulation of GATA3 in pre-implantation mouse embryos reduces Cdx2 expression and inhibits morula to blastocyst transformation. Our results indicate a novel function of GATA3, in which it is selectively expressed in TE, regulates expression of key genes in TE lineage, and is involved in morula to blastocyst transformation.

T cell factor 1 initiates the T helper type 2 fate by inducing the transcription factor GATA-3 and repressing interferon-gamma

The differentiation of activated CD4(+) T cells into the T helper type 1 (T(H)1) or T(H)2 fate is regulated by cytokines and the transcription factors T-bet and GATA-3. Whereas interleukin 12 (IL-12) produced by antigen-presenting cells initiates the T(H)1 fate, signals that initiate the T(H)2 fate are not completely characterized. Here we show that early GATA-3 expression, required for T(H)2 differentiation, was induced by T cell factor 1 (TCF-1) and its cofactor beta-catenin, mainly from the proximal Gata3 promoter upstream of exon 1b. This activity was induced after T cell antigen receptor (TCR) stimulation and was independent of IL-4 receptor signaling through the transcription factor STAT6. Furthermore, TCF-1 blocked T(H)1 fate by negatively regulating interferon-gamma (IFN-gamma) expression independently of beta-catenin. Thus, TCF-1 initiates T(H)2 differentiation of activated CD4(+) T cells by promoting GATA-3 expression and suppressing IFN-gamma expression.

The different faces of Notch in T-helper-cell differentiation

Interleukin-12 (IL-12) and IL-4 induce T helper 1 (T(H)1)- and T(H)2-cell differentiation, respectively, in vitro. However, not all T(H)1-cell responses require IL-12 in vivo, and T(H)2-cell responses are remarkably independent of IL-4-receptor signalling, suggesting that other polarizing signals must exist. Accumulating evidence indicates that Notch is a candidate receptor that might mediate these signals. However, contrasting roles for Notch have been proposed: some evidence shows that Notch promotes T(H)1-cell differentiation, whereas other evidence supports a prominent role for Notch in T(H)2-cell differentiation. In this Review, we discuss recent findings that help to reconcile this discrepancy and highlight the accumulating evidence for the role of Notch in T-cell-mediated diseases.

Epigenetic control of T-helper-cell differentiation

Naive CD4(+) T cells give rise to T-helper-cell subsets with functions that are tailored to their respective roles in host defence. The specification of T-helper-cell subsets is controlled by networks of lineage-specifying transcription factors, which bind to regulatory elements in genes that encode cytokines and other transcription factors. The nuclear context in which these transcription factors act is affected by epigenetic processes, which allow programmes of gene expression to be inherited by progeny cells that at the same time retain the potential for change in response to altered environmental signals. In this Review, we describe these epigenetic processes and discuss how they collaborate to govern the fate and function of T helper cells.

GATA3 and the T-cell lineage: essential functions before and after T-helper-2-cell differentiation

Many advances in our understanding of the molecules that regulate the development, differentiation and function of T cells have been made over the past few years. One important regulator of T-cell differentiation is the transcription factor GATA-binding protein 3 (GATA3). Although the main function of GATA3 is to act as a master transcription factor for the differentiation of T helper 2 (T(H)2) cells, new research has helped to uncover crucial functions of GATA3 in T cells that go beyond T(H)2-cell differentiation and that are important at earlier stages of haematopoietic and lymphoid-cell development. This Review focuses on the functions of GATA3 from early thymocyte development to effector T-cell differentiation. In addition, we discuss the interactions between GATA3 and other transcription factors and signalling pathways, and highlight the functional significance of the GATA3 protein structure.

BRG1-mediated chromatin remodeling regulates differentiation and gene expression of T helper cells

During T helper cell differentiation, distinct programs of gene expression play a key role in defining the immune response to an environmental challenge. How chromatin remodeling events at the associated cytokine loci control differentiation is not known. We found that the ATP-dependent remodeling enzyme subunit BRG1 was required for T helper 2 (Th2) differentiation and Th2 cytokine transcription. BRG1 binding to cytokine genes was regulated by the extent of differentiation, the extent of activation, and cell fate. BRG1 was required for some features of the chromatin structure in target genes (DNase I hypersensitivity and histone acetylation), suggesting that BRG1 remodeling activity was directly responsible for changes in gene expression. NFAT and STAT6 activity were required for BRG1 recruitment to the Th2 locus control region, and STAT6 associated with BRG1 in a differentiation-inducible manner, suggesting direct recruitment of BRG1 to the bound loci. Together, these findings suggest BRG1 interprets differentiation signals and plays a causal role in gene regulation, chromatin structure, and cell fate.

GATA3 mRNA in ginbuna crucian carp (Carassius auratus langsdorfii): cDNA cloning, splice variants and expression analysis

GATA3, a transcriptional activator, plays a critical role in the development of T-cells and differentiation to T helper type 2 cells. To date, no information is available on the role of GATA3 in the teleost immune system. We identified full-length cDNA and alternatively spliced variants of ginbuna crucian carp GATA3 (gbGATA3). The gbGATA3 gene is transcribed into multiple splice variants lacking either one or both zinc finger domains, although the sequences of both domains are fully conserved between ginbuna and other vertebrates. We found that alternative splice site and stop codon in gbGATA3 intron 3, located between exons that separately encode the two zinc finger domains, are conserved among teleosts, suggesting that teleost GATA3 gene can be translated into multiple isoforms. RT-PCR analysis revealed that the gbGATA3 is strongly expressed in the brain, thymus and gill of unstimulated fish. Moreover, gbGATA3 expression was detected in surface-IgM-negative lymphocytes among kidney cells sorted by FACS. Real-time PCR demonstrated that expression levels of full-length gbGATA3 and the splice variants differed with tissue type, but full length was always the predominantly expressed form. These results suggest that gbGATA3, including its splice variants, is involved in teleost T-cell function.

Notch: filling a hole in T helper 2 cell differentiation

In this issue of Immunity, Amsen et al. (2007) and Fang et al. (2007) propose a direct role for Notch signaling in the expression of GATA-3 transcription factor and T helper 2 cell differentiation.

c-Myb regulates lineage choice in developing thymocytes via its target gene Gata3

During T-cell development, thymocytes with intermediate avidity for antigen-MHC complexes are positively selected and then differentiate into functional cytotoxic and helper T cells. This process is controlled by signalling from the T-cell receptor (TCR). Here, we show that the c-Myb transcription factor is a critical downstream regulator of positive selection, promoting the development of helper T cells and blocking the development of cytotoxic T cells. A gain-of-function c-Myb transgene stops development of cytotoxic T cells, instead causing accumulation of a precursor population. Conversely, loss of c-Myb in selecting cells results in significantly fewer helper T cells. In c-Myb-null thymocytes, Gata3, a critical inducer of T-helper cell fate, is not upregulated in response to T-cell receptor signaling, following selection. We show that Gata3 is a direct target of c-Myb, and propose that c-Myb is an important regulator of Gata3, required for transduction of the T-cell receptor signal for subsequent helper cell lineage differentiation.