Regulation of αβ/γδ T Cell Lineage Commitment and Peripheral T Cell Responses by Notch/RBP-J Signaling

ADAM10 modulates the efficacy of T-cell-mediated therapy in solid tumors

T-cell-mediated therapeutic strategies are the most potent effectors of cancer immunotherapy. However, an essential barrier to this therapy in solid tumors is disrupting the anti-cancer immune response, cancer-immunity cycle, T-cell priming, trafficking and T-cell cytotoxic capacity. Thus, reinforcing the anti-cancer immune response is needed to improve the effectiveness of T-cell-mediated therapy. Tumor-associated protease ADAM10, endothelial cells (ECs) and cytotoxic CD8+ T cells engage in complex communication via adhesion, transmigration and chemotactic mechanisms to facilitate an anti-cancer immune response. The precise impact of ADAM10 on the intricate mechanisms underlying these interactions remains unclear. This paper broadly explores how ADAM10, through different routes, influences the efficacy of T-cell-mediated therapy. ADAM10 cleaves CD8+ T-cell-targeting genes and impacts their expression and specificity. In addition, ADAM10 mediates the interactions of adhesion molecules with T cells and influences CD8+ T-cell activity and trafficking. Thus, understanding the role of ADAM10 in these events may lead to innovative strategies for advancing T-cell-mediated therapies.

The role of the Notch signalling pathway in the pathogenesis of ulcerative colitis: from the perspective of intestinal mucosal barrier

Ulcerative colitis is a common digestive disorder worldwide, with increasing incidence in recent years. It is an urgent problem to be solved, as it seriously affects and threatens the health and life of the global population. Studies have shown that dysfunction of the intestinal mucosal barrier is a critical pathogenic factor and molecular basis of ulcerative colitis, and some scholars have described it as a "barrier organ disease." While the Notch signalling pathway affects a series of cellular processes, including proliferation, differentiation, development, migration, and apoptosis. Therefore, it can regulate intestinal stem cells, CD4+ T cells, innate lymphoid cells, macrophages, and intestinal microbiota and intervene in the chemical, physical, immune, and biological mucosal barriers in cases of ulcerative colitis. The Notch signalling pathway associated with the pathogenesis of ulcerative colitis has distinct characteristics, with good regulatory effects on the mucosal barrier. However, research on ulcerative colitis has mainly focused on immune regulation, anti-inflammatory activity, and antioxidant stress; therefore, the study of the Notch signalling pathway suggests the possibility of understanding the pathogenesis of ulcerative colitis from another perspective. In this article we explore the role and mechanism of the Notch signalling pathway in the pathogenesis of ulcerative colitis from the perspective of the intestinal mucosal barrier to provide new targets and theoretical support for further research on the pathogenesis and clinical treatment of ulcerative colitis.

Cdc73 protects Notch-induced T-cell leukemia cells from DNA damage and mitochondrial stress

ABSTRACT

Activated Notch signaling is highly prevalent in T-cell acute lymphoblastic leukemia (T-ALL), but pan-Notch inhibitors showed excessive toxicity in clinical trials. To find alternative ways to target Notch signals, we investigated cell division cycle 73 (Cdc73), which is a Notch cofactor and key component of the RNA polymerase-associated transcriptional machinery, an emerging target in T-ALL. Although we confirmed previous work that CDC73 interacts with NOTCH1, we also found that the interaction in T-ALL was context-dependent and facilitated by the transcription factor ETS1. Using mouse models, we showed that Cdc73 is important for Notch-induced T-cell development and T-ALL maintenance. Mechanistically, chromatin and nascent gene expression profiling showed that Cdc73 intersects with Ets1 and Notch at chromatin within enhancers to activate expression of known T-ALL oncogenes through its enhancer functions. Cdc73 also intersects with these factors within promoters to activate transcription of genes that are important for DNA repair and oxidative phosphorylation through its gene body functions. Consistently, Cdc73 deletion induced DNA damage and apoptosis and impaired mitochondrial function. The CDC73-induced DNA repair expression program co-opted by NOTCH1 is more highly expressed in T-ALL than in any other cancer. These data suggest that Cdc73 might induce a gene expression program that was eventually intersected and hijacked by oncogenic Notch to augment proliferation and mitigate the genotoxic and metabolic stresses of elevated Notch signaling. Our report supports studying factors such as CDC73 that intersect with Notch to derive a basic scientific understanding on how to combat Notch-dependent cancers without directly targeting the Notch complex.

Cdc73 protects Notch-induced T-cell leukemia cells from DNA damage and mitochondrial stress

Activated Notch signaling is highly prevalent in T-cell acute lymphoblastic leukemia (T-ALL) but pan-Notch inhibitors were toxic in clinical trials. To find alternative ways to target Notch signals, we investigated Cell division cycle 73 (Cdc73), which is a Notch cofactor and component of transcriptional machinery, a potential target in T-ALL. While we confirmed previous work that CDC73 interacts with NOTCH1, we also found that the interaction in T-ALL was context-dependent and facilitated by the lymphoid transcription factor ETS1. Using mouse models, we showed that Cdc73 is important for Notch-induced T-cell development and T-ALL maintenance. Mechanistically, Cdc73, Ets1, and Notch intersect chromatin at promoters and enhancers to activate oncogenes and genes that are important for DNA repair and oxidative phosphorylation. Consistently, Cdc73 deletion in T-ALL cells induced DNA damage and impaired mitochondrial function. Our data suggests that Cdc73 might promote a gene expression program that was eventually intersected by Notch to mitigate the genotoxic and metabolic stresses of elevated Notch signaling. We also provide mechanistic support for testing inhibitors of DNA repair, oxidative phosphorylation, and transcriptional machinery. Inhibiting pathways like Cdc73 that intersect with Notch at chromatin might constitute a strategy to weaken Notch signals without directly targeting the Notch complex.

Multimodal human thymic profiling reveals trajectories and cellular milieu for T agonist selection

To prevent autoimmunity, thymocytes expressing self-reactive T cell receptors (TCRs) are negatively selected, however, divergence into tolerogenic, agonist selected lineages represent an alternative fate. As thymocyte development, selection, and lineage choices are dependent on spatial context and cell-to-cell interactions, we have performed Cellular Indexing of Transcriptomes and Epitopes by sequencing (CITE-seq) and spatial transcriptomics on paediatric human thymu​​s. Thymocytes expressing markers of strong TCR signalling diverged from the conventional developmental trajectory prior to CD4⁺ or CD8⁺ lineage commitment, while markers of different agonist selected T cell populations (CD8αα(I), CD8αα(II), T_(agonist), T_reg(diff), and T_reg) exhibited variable timing of induction. Expression profiles of chemokines and co-stimulatory molecules, together with spatial localisation, supported that dendritic cells, B cells, and stromal cells contribute to agonist selection, with different subsets influencing thymocytes at specific developmental stages within distinct spatial niches. Understanding factors influencing agonist T cells is needed to benefit from their immunoregulatory effects in clinical use.

Transcriptional regulation of Notch1 by nuclear factor-κB during T cell activation

Notch1 plays important roles in T cell development and is highly expressed in activated CD4⁺ T cells. However, the underlying mechanism of Notch1 transcription in T cells has not been fully characterized. Therefore, we aimed to determine how Notch1 expression is regulated during the activation of CD4⁺ T cells. Both the surface expression and mRNA transcription of Notch1 were significantly higher in activated CD4⁺ T cells, but the inhibition of phosphatidylinositol 3-kinase (PI3K) by LY294002 or deletion of the Pdk1 gene impaired this upregulation of Notch1. Interrogation of the Notch1 promoter region using serially deleted Notch1 promoter reporters revealed that the - 300 to - 270 region is crucial for its transcription in activated T cells. In addition, we found that nuclear factor (NF)-κB subunits containing RelA bind directly to this promoter region, thereby upregulating transcription. In addition, inhibition of NF-κB by SN50 impaired upregulation of Notch1 surface protein and mRNA in activated CD4⁺ T cells. Thus, we provide evidence that Notch1 transcription in activated CD4⁺ T cells is upregulated via the PI3K-PDK1-NF-κB signaling pathway.

A double-negative thymocyte-specific enhancer augments Notch1 signaling to direct early T cell progenitor expansion, lineage restriction and β-selection

T cell differentiation requires Notch1 signaling. In the present study, we show that an enhancer upstream of Notch1 active in double-negative (DN) mouse thymocytes is responsible for raising Notch1 signaling intrathymically. This enhancer is required to expand multipotent progenitors intrathymically while delaying early differentiation until lineage restrictions have been established. Early thymic progenitors lacking the enhancer show accelerated differentiation through the DN stages and increased frequency of B, innate lymphoid (IL) and natural killer (NK) cell differentiation. Transcription regulators for T cell lineage restriction and commitment are expressed normally, but IL and NK cell gene expression persists after T cell lineage commitment and T cell receptor β VDJ recombination, Cd3 expression and β-selection have been impaired. This Notch1 enhancer is inactive in double-positive (DP) thymocytes. Its aberrant reactivation at this stage in Ikaros mutants is required for leukemogenesis. Thus, the DN-specific Notch1 enhancer harnesses the regulatory architecture of DN and DP thymocytes to achieve carefully orchestrated changes in Notch1 signaling required for early lineage restrictions and normal T cell differentiation.

Spermidine activates mitochondrial trifunctional protein and improves antitumor immunity in mice

Spermidine (SPD) delays age-related pathologies in various organisms. SPD supplementation overcame the impaired immunotherapy against tumors in aged mice by increasing mitochondrial function and activating CD8 + T cells. Treatment of naïve CD8 + T cells with SPD acutely enhanced fatty acid oxidation. SPD conjugated to beads bound to the mitochondrial trifunctional protein (MTP). In the MTP complex, synthesized and purified from Escherichia coli , SPD bound to the α and β subunits of MTP with strong affinity and allosterically enhanced their enzymatic activities. T cell–specific deletion of the MTP α subunit abolished enhancement of programmed cell death protein 1 (PD-1) blockade immunotherapy by SPD, indicating that MTP is required for SPD-dependent T cell activation.

RNA m6A demethylase ALKBH5 regulates the development of γδ T cells

γδ T cells are an abundant T cell population at the mucosa and are important in providing immune surveillance as well as maintaining tissue homeostasis. However, despite γδ T cells' origin in the thymus, detailed mechanisms regulating γδ T cell development remain poorly understood. N⁶-methyladenosine (m⁶A) represents one of the most common posttranscriptional modifications of messenger RNA (mRNA) in mammalian cells, but whether it plays a role in γδ T cell biology is still unclear. Here, we show that depletion of the m⁶A demethylase ALKBH5 in lymphocytes specifically induces an expansion of γδ T cells, which confers enhanced protection against gastrointestinal Salmonella typhimurium infection. Mechanistically, loss of ALKBH5 favors the development of γδ T cell precursors by increasing the abundance of m⁶A RNA modification in thymocytes, which further reduces the expression of several target genes including Notch signaling components Jagged1 and Notch2. As a result, impairment of Jagged1/Notch2 signaling contributes to enhanced proliferation and differentiation of γδ T cell precursors, leading to an expanded mature γδ T cell repertoire. Taken together, our results indicate a checkpoint role of ALKBH5 and m⁶A modification in the regulation of γδ T cell early development.

Transcriptome Signature of Vγ9Vδ2 T Cells Treated With Phosphoantigens and Notch Inhibitor Reveals Interplay Between TCR and Notch Signaling Pathways

Gamma delta (γδ) T cells, especially the Vγ9Vδ2 subtype, have been implicated in cancer therapy and thus have earned the spotlight in the past decade. Although one of the most important properties of γδ T cells is their activation by phosphoantigens, which are intermediates of the Mevalonate and Rohmer pathway of isoprenoid biosynthesis, such as IPP and HDMAPP, respectively, the global effects of such treatments on Vγ9Vδ2 T cells remain elusive. Here, we used the high-throughput transcriptomics approach to elucidate the transcriptional changes in human Vγ9Vδ2 T cells upon HDMAPP, IPP, and anti-CD3 treatments in combination with interleukin 2 (IL2) cytokine stimulation. These activation treatments exhibited a dramatic surge in transcription with distinctly enriched pathways. We further assessed the transcriptional dynamics upon inhibition of Notch signaling coupled with activation treatments. We observed that the metabolic processes are most affected upon Notch inhibition via GSI-X. The key effector genes involved in gamma-delta cytotoxic function were downregulated upon Notch blockade even in combination with activation treatment, suggesting a transcriptional crosstalk between T-cell receptor (TCR) signaling and Notch signaling in Vγ9Vδ2 T cells. Collectively, we demonstrate the effect of the activation of TCR signaling by phosphoantigens or anti-CD3 on the transcriptional status of Vγ9Vδ2 T cells along with IL2 stimulation. We further show that the blockade of Notch signaling antagonistically affects this activation.

Inhibition of gamma-secretase activity without interfering in Notch signalling decreases inflammatory response in patients with cutaneous leishmaniasis

Cutaneous leishmaniasis (CL) patients present an exacerbated inflammatory response associated with tissue damage and ulcer development. Increasing numbers of patients have exhibited treatment failure, which remains not well understood. We hypothesized that adjuvant anti-inflammatory therapy would benefit CL patients. The aim of the present study was to investigate the contribution of Notch signalling and gamma-secretase activity to the inflammatory response observed in CL patients. Notch signalling is a molecular signalling pathway conserved among animal species. Gamma-secretase forms a complex of proteins that, among other pathways, modulates Notch signalling and immune response. We found that Notch 1 cell receptor signalling protects against the pathologic inflammatory response, and JLK6, a gamma-secretase inhibitor that does not interfere with Notch signalling, was shown to decrease the in-vitro inflammatory response in CL. Our data suggest that JLK6 may serve as an adjuvant treatment for CL patients.

Ontogenic timing, T cell receptor signal strength, and Notch signaling direct γδ T cell functional differentiation in vivo

γδ T cells form an integral arm of the immune system and are critical during protective and destructive immunity. However, how γδ T cells are functionally programmed in vivo remains unclear. Here, we employ RBPJ-inducible and KN6-transgenic mice to assess the roles of ontogenic timing, T cell receptor (TCR) signal strength, and Notch signaling. We find skewing of Vγ1+ cells toward the PLZF+Lin28b+ lineage at the fetal stage. Generation of interleukin-17 (IL-17)-producing γδ T cells is favored during, although not exclusive to, the fetal stage. Surprisingly, Notch signaling is dispensable for peripheral γδ T cell IL-17 production. Strong TCR signals, together with Notch, promote IL-4 differentiation. Conversely, less strong TCR signals promote Notch-independent IL-17 differentiation. Single-cell transcriptomic analysis reveals differential programming instilled by TCR signal strength and Notch for specific subsets. Thus, our results precisely define the roles of ontogenic timing, TCR signal strength, and Notch signaling in γδ T cell functional programming in vivo.

Whole-Exome Sequencing of Radiation-Induced Thymic Lymphoma in Mouse Models Identifies Notch1 Activation as a Driver of p53 Wild-Type Lymphoma

Mouse models of radiation-induced thymic lymphoma are widely used to study the development of radiation-induced blood cancers and to gain insights into the biology of human T-cell lymphoblastic leukemia/lymphoma. Here we aimed to identify key oncogenic drivers for the development of radiation-induced thymic lymphoma by performing whole-exome sequencing using tumors and paired normal tissues from mice with and without irradiation. Thymic lymphomas from irradiated wild-type (WT), p53^+/-, and Kras^LA1 mice were not observed to harbor significantly higher numbers of nonsynonymous somatic mutations compared with thymic lymphomas from unirradiated p53^-/- mice. However, distinct patterns of recurrent mutations arose in genes that control the Notch1 signaling pathway based on the mutational status of p53. Preferential activation of Notch1 signaling in p53 WT lymphomas was also observed at the RNA and protein level. Reporter mice for activation of Notch1 signaling revealed that total-body irradiation (TBI) enriched Notch1^hi CD44⁺ thymocytes that could propagate in vivo after thymocyte transplantation. Mechanistically, genetic inhibition of Notch1 signaling in immature thymocytes prevented formation of radiation-induced thymic lymphoma in p53 WT mice. Taken together, these results demonstrate a critical role of activated Notch1 signaling in driving multistep carcinogenesis of thymic lymphoma following TBI in p53 WT mice. SIGNIFICANCE: These findings reveal the mutational landscape and key drivers in murine radiation-induced thymic lymphoma, a classic animal model that has been used to study radiation carcinogenesis for over 70 years.

Logic and lineage impacts on functional transcription factor deployment for T-cell fate commitment

Transcription factors are the major agents that read the regulatory sequence information in the genome to initiate changes in expression of specific genes, both in development and in physiological activation responses. Their actions depend on site-specific DNA binding and are largely guided by their individual DNA target sequence specificities. However, their action is far more conditional in a real developmental context than would be expected for simple reading of local genomic DNA sequence, which is common to all cells in the organism. They are constrained by slow-changing chromatin states and by interactions with other transcription factors, which affect their occupancy patterns of potential sites across the genome. These mechanisms lead to emergent discontinuities in function even for transcription factors with minimally changing expression. This is well revealed by diverse lineages of blood cells developing throughout life from hematopoietic stem cells, which use overlapping combinations of transcription factors to drive strongly divergent gene regulation programs. Here, using development of T lymphocytes from hematopoietic multipotent progenitor cells as a focus, recent evidence is reviewed on how binding specificity and dynamics, transcription factor cooperativity, and chromatin state changes impact the effective regulatory functions of key transcription factors including PU.1, Runx1, Notch-RBPJ, and Bcl11b.

The role of MKK4 in T-cell development and immunity to viral infections

The stress-activated protein kinases (SAPKs)/c-Jun-N-terminal-kinases (JNK) are members of the mitogen-activated protein kinase family. These kinases are responsible for transducing cellular signals through a phosphorylation-dependent signaling cascade. JNK activation in immune cells can lead to a range of critical cellular responses that include proliferation, differentiation and apoptosis. MKK4 is a SAPK that can activate both JNK1 and JNK2; however, its role in T-cell development and function has been controversial. Additionally, loss of either JNK1 or JNK2 has opposing effects in the generation of T-cell immunity to viral infection and cancer. We used mice with a conditional loss of MKK4 in T cells to investigate the in vivo role of MKK4 in T-cell development and function during lymphocytic choriomeningitis virus (LCMV) infection. We found no physiologically relevant differences in T-cell responses or immunity to either acute or chronic LCMV in the absence of MKK4.

Notch signaling at the crossroads of innate and adaptive immunity

Notch signaling is an evolutionarily conserved cell-to-cell signaling pathway that regulates cellular differentiation and function across multiple tissue types and developmental stages. In this review, we discuss our current understanding of Notch signaling in mammalian innate and adaptive immunity. The importance of Notch signaling is pervasive throughout the immune system, as it elicits lineage and context-dependent effects in a wide repertoire of cells. Although regulation of binary cell fate decisions encompasses many of the functions first ascribed to Notch in the immune system, recent advances in the field have refined and expanded our view of the Notch pathway beyond this initial concept. From establishing T cell identity in the thymus to regulating mature T cell function in the periphery, the Notch pathway is an essential, recurring signal for the T cell lineage. Among B cells, Notch signaling is required for the development and maintenance of marginal zone B cells in the spleen. Emerging roles for Notch signaling in innate and innate-like lineages such as classical dendritic cells and innate lymphoid cells are likewise coming into view. Lastly, we speculate on the molecular underpinnings that shape the activity and versatility of the Notch pathway.

CD28 Signaling Drives Notch Ligand Expression on CD4 T Cells

Notch signaling provides an important cue in the mammalian developmental process. It is a key player in T cell development and function. Notch ligands such as Delta-like ligands (DLL) 1, 3, 4, and JAG1, 2 can impact Notch signaling positively or negatively, by trans-activation or cis-inhibition. Trans and cis interactions are receptor-ligand interaction on two adjacent cells and interaction on the same cell, respectively. The former sends an activation signal and the later, a signal for inhibition of Notch. However, earlier reports suggested that Notch is activated in the absence of Notch ligand-expressing APCs in a purified population of CD4 T cells. Thus, the role of ligands in Notch activation, in a purified population of CD4 T cells, remains obscure. In this study, we demonstrate that mature CD4 T cells are capable of expressing Notch ligands on their surface very early upon activation with soluble antibodies against CD3 and CD28. Moreover, signaling solely through CD28 induces Notch ligand expression and CD3 signaling inhibits ligand expression, in contrast to Notch which is induced by CD3 signaling. Additionally, by using decoys, mimicking the Notch extracellular domain, we demonstrated that DLL1, DLL4, and JAG1, expressed on the T cells, can cis-interact with the Notch receptor and inhibit activation of Notch. Thus, our data indicate a novel mechanism of the regulation of Notch ligand expression on CD4 T cells and its impact on activated Notch.

Endothelial Notch activation promotes neutrophil transmigration via downregulating endomucin to aggravate hepatic ischemia/reperfusion injury

Inflammatory leukocytes infiltration is orchestrated by mechanisms involving chemokines, selectins, addressins and other adhesion molecules derived from endothelial cells (ECs), but how they respond to inflammatory cues and coordinate leukocyte transmigration remain elusive. In this study, using hepatic ischemia/reperfusion injury (HIRI) as a model, we identified that endothelial Notch activation was rapidly and dynamically induced in liver sinusoidal endothelial cells (LSECs) in acute inflammation. In mice with EC-specific Notch activation (NIC^eCA), HIRI induced exacerbated liver damage. Consistently, endothelial Notch activation enhanced neutrophil infiltration and tumor necrosis factor (TNF)-α expression in HIRI. Transcriptome analysis and further qRT-PCR as well as immunofluorescence indicated that endomucin (EMCN), a negative regulator of leukocyte adhesion, was downregulated in LSECs from NIC^eCA mice. EMCN was downregulated during HIRI in wild-type mice and in vitro cultured ECs insulted by hypoxia/re-oxygenation injury. Notch activation in ECs led to increased neutrophil adhesion and transendothelial migration, which was abrogated by EMCN overexpression in vitro. In mice deficient of RBPj, the integrative transcription factor of canonical Notch signaling, although overwhelming sinusoidal malformation aggravated HIRI, the expression of EMCN was upregulated; and pharmaceutical Notch blockade in vitro also upregulated EMCN and inhibited transendothelial migration of neutrophils. The Notch activation-exaggerated HIRI was compromised by blocking LFA-1, which mediated leukocyte adherence by associating with EMCN. Therefore, endothelial Notch signaling controls neutrophil transmigration via EMCN to modulate acute inflammation in HIRI.

Allergin-1 Immunoreceptor Suppresses House Dust Mite-Induced Allergic Airway Inflammation

House dust mite (HDM) allergens are leading causes of allergic asthma characterized by Th2 responses. The lung-resident CD11b⁺ dendritic cells (DCs) play a key role in Th2 cell development in HDM-induced allergic asthma. However, the regulatory mechanism of HDM-induced CD11b⁺ DC activation remains incompletely understood. In this study, we demonstrate that mice deficient in an inhibitory immunoreceptor, Allergin-1, showed exacerbated HDM-induced airway eosinophilia and serum IgE elevation. By using bone marrow-chimeric mice that were sensitized with adoptively transferred HDM-stimulated wild-type or Allergin-1-deficient CD11b⁺ bone marrow-derived cultured DCs (BMDCs), followed by challenge with HDM, we show that Allergin-1 on the BMDCs suppressed HDM-induced allergic airway inflammation. We also show that Allergin-1 suppressed HDM-induced PGE₂ production from CD11b⁺ BMDCs by inhibiting Syk tyrosine kinase activation through recruitment of SHP-1, subsequently leading to negative regulation of Th2 responses. These results suggest that Allergin-1 plays an important role in regulation of HDM-induced allergic airway inflammation.

Role of the Orphan Nuclear Receptor NR4A Family in T-Cell Biology

The nuclear orphan receptors NR4A1, NR4A2, and NR4A3 are immediate early genes that are induced by various signals. They act as transcription factors and their activity is not regulated by ligand binding and are thus regulated via their expression levels. Their expression is transiently induced in T cells by triggering of the T cell receptor following antigen recognition during both thymic differentiation and peripheral T cell responses. In this review, we will discuss how NR4A family members impact different aspects of the life of a T cell from thymic differentiation to peripheral response against infections and cancer.

Notch signalling in T cell homeostasis and differentiation

The evolutionarily conserved Notch signalling pathway regulates the differentiation and function of mature T lymphocytes with major context-dependent consequences in host defence, autoimmunity and alloimmunity. The emerging effects of Notch signalling in T cell responses build upon a more established role for Notch in T cell development. Here, we provide a critical review of this burgeoning literature to make sense of what has been learned so far and highlight the experimental strategies that have been most useful in gleaning physiologically relevant information. We outline the functional consequences of Notch signalling in mature T cells in addition to key specific Notch ligand–receptor interactions and downstream molecular signalling pathways. Our goal is to help clarify future directions for this expanding body of work and the best approaches to answer important open questions.

RBPJ-dependent Notch signaling initiates the T cell program in a subset of thymus-seeding progenitors

T cell specification and commitment require Notch signaling. Although the requirement for Notch signaling during intrathymic T cell development is known, it is still unclear whether the onset of T cell priming can occur in a prethymic niche and whether RBPJ-dependent Notch signaling has a role during this event. Here, we established an Rbpj-inducible system that allowed temporal and tissue-specific control of the responsiveness to Notch in all hematopoietic cells. Using this system, we found that Notch signaling was required before the early T cell progenitor stage in the thymus. Lymphoid-primed multipotent progenitors in the bone marrow underwent Notch signaling with Rbpj induction, which inhibited development towards the myeloid lineage in thymus-seeding progenitors. Thus, our results indicated that the onset of T cell differentiation occurred in a prethymic setting, and that Notch played an important role during this event.

Transcriptome analysis of fowl adenovirus serotype 4 infection in chickens

Fowl adenovirus serotype 4 (FAdV-4) is a causative agent of inclusion body hepatitis and hydropericardium–hepatitis syndrome. These diseases cause considerable economic losses in the global poultry industry and are significant stressors for infected chickens. However, the molecular mechanisms of FAdV-4 pathogenesis are poorly understood. In the present study, we identified differentially expressed genes from the livers of FAdV-4-infected chickens using RNA-seq at 7, 14 and 21 days after FAdV-4 infection. We identified 2395 differentially expressed genes at the three time points. These genes were enriched in variety of biological processes and pathways including PPAR and Notch signaling, cytokine–cytokine receptor interactions and Toll-like receptor signaling pathways. The transcriptional data were validated by quantitative real-time PCR. Our results will assist in the understanding of the molecular pathogenesis of FAdV-4 infection and for developing novel antiviral therapies.

Metabolic signaling directs the reciprocal lineage decisions of αβ and γδ T cells

The interaction between extrinsic factors and intrinsic signal strength governs thymocyte development, but the mechanisms linking them remain elusive. We report that mechanistic target of rapamycin complex 1 (mTORC1) couples microenvironmental cues with metabolic programs to orchestrate the reciprocal development of two fundamentally distinct T cell lineages, the αβ and γδ T cells. Developing thymocytes dynamically engage metabolic programs including glycolysis and oxidative phosphorylation, as well as mTORC1 signaling. Loss of RAPTOR-mediated mTORC1 activity impairs the development of αβ T cells but promotes γδ T cell generation, associated with disrupted metabolic remodeling of oxidative and glycolytic metabolism. Mechanistically, we identify mTORC1-dependent control of reactive oxygen species production as a key metabolic signal in mediating αβ and γδ T cell development, and perturbation of redox homeostasis impinges upon thymocyte fate decisions and mTORC1-associated phenotypes. Furthermore, single-cell RNA sequencing and genetic dissection reveal that mTORC1 links developmental signals from T cell receptors and NOTCH to coordinate metabolic activity and signal strength. Our results establish mTORC1-driven metabolic signaling as a decisive factor for reciprocal αβ and γδ T cell development and provide insight into metabolic control of cell signaling and fate decisions.

The multifaceted role of Notch signal in regulating T cell fate

Notch signaling pathway facilitates important cellular functions of the host. Notch signal is essential for the development of T cells, and the role of Notch in fine tuning of αβ versus γδ T cell lineage commitment is fundamentally different in mice and human. The Notch family of cell surface receptor likewise plays a critical role in regulating T cell activation, and influences T cell response both intrinsically and through the local environment. In this review, we take an overview of Notch signaling pathway and also emphasize the role of Notch signal in T cell lineage differentiation and activating effector function of peripheral T cells.

Dynamic regulation of NOTCH1 activation and Notch ligand expression in human thymus development

T-cell development is a complex dynamic process that relies on ordered stromal signals delivered to thymus-seeding progenitors that migrate throughout different thymus microenvironments (TMEs). Particularly, Notch signaling provided by thymic epithelial cells (TECs) is crucial for T-cell fate specification and generation of mature T cells. Four canonical Notch ligands (Dll1, Dll4, Jag1 and Jag2) are expressed in the thymus, but their spatial distribution in functional TMEs is largely unknown, especially in humans, and their impact on Notch1 activation during T-lymphopoiesis remains undefined. Based on immunohistochemistry and quantitative confocal microscopy of fetal, postnatal and adult human and mouse thymus samples, we show that spatial regulation of Notch ligand expression defines discrete Notch signaling niches and dynamic species-specific TMEs. We further show that Notch ligand expression, particularly DLL4, is tightly regulated in cortical TECs during human thymus ontogeny and involution. Also, we provide the first evidence that NOTCH1 activation is induced in vivo in CD34⁺ progenitors and developing thymocytes at particular cortical niches of the human fetal and postnatal thymus. Collectively, our results show that human thymopoiesis involves complex spatiotemporal regulation of Notch ligand expression, which ensures the coordinated delivery of niche-specific NOTCH1 signals required for dynamic T-cell development.

Presenilin1 regulates Th1 and Th17 effector responses but is not required for experimental autoimmune encephalomyelitis

Multiple Sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system (CNS) where pathology is thought to be regulated by autoreactive T cells of the Th1 and Th17 phenotype. In this study we sought to understand the functions of Presenilin 1 (PSEN1) in regulating T cell effector responses in the experimental autoimmune encephalomyelitis (EAE) murine model of MS. PSEN1 is the catalytic subunit of γ-secretase a multimolecular protease that mediates intramembranous proteolysis. γ-secretase is known to regulate several pathways of immune importance. Here we examine the effects of disrupting PSEN1 functions on EAE and T effector differentiation using small molecule inhibitors of γ-secretase (GSI) and T cell-specific conditional knockout mice (PSEN1 cKO). Surprisingly, blocking PSEN1 function by GSI treatment or PSEN1 cKO had little effect on the development or course of MOG35-55-induced EAE. In vivo GSI administration reduced the number of myelin antigen-specific T cells and suppressed Th1 and Th17 differentiation following immunization. In vitro, GSI treatment inhibited Th1 differentiation in neutral but not IL-12 polarizing conditions. Th17 differentiation was also suppressed by the presence of GSI in all conditions and GSI-treated Th17 T cells failed to induce EAE following adoptive transfer. PSEN cKO T cells showed reduced Th1 and Th17 differentiation. We conclude that γ-secretase and PSEN1-dependent signals are involved in T effector responses in vivo and potently regulate T effector differentiation in vitro, however, they are dispensable for EAE.

Stage-specific roles for Zmiz1 in Notch-dependent steps of early T-cell development

Notch1 signaling must elevate to high levels in order to drive the proliferation of CD4^-CD8^- double-negative (DN) thymocytes and progression to the CD4⁺CD8⁺ double-positive (DP) stage through β-selection. During this critical phase of pre-T-cell development, which is also known as the DN-DP transition, it is unclear whether the Notch1 transcriptional complex strengthens its signal output as a discrete unit or through cofactors. We previously showed that the protein inhibitor of activated STAT-like coactivator Zmiz1 is a context-dependent cofactor of Notch1 in T-cell leukemia. We also showed that withdrawal of Zmiz1 generated an early T-lineage progenitor (ETP) defect. Here, we show that this early defect seems inconsistent with loss-of-Notch1 function. In contrast, at the later pre-T-cell stage, withdrawal of Zmiz1 impaired the DN-DP transition by inhibiting proliferation, like withdrawal of Notch. In pre-T cells, but not ETPs, Zmiz1 cooperatively regulated Notch1 target genes Hes1, Lef1, and Myc. Enforced expression of either activated Notch1 or Myc partially rescued the Zmiz1-deficient DN-DP defect. We identified residues in the tetratricopeptide repeat (TPR) domain of Zmiz1 that bind Notch1. Mutating only a single residue impaired the Zmiz1-Notch1 interaction, Myc induction, the DN-DP transition, and leukemic proliferation. Similar effects were seen using a dominant-negative TPR protein. Our studies identify stage-specific roles of Zmiz1. Zmiz1 is a context-specific cofactor for Notch1 during Notch/Myc-dependent thymocyte proliferation, whether normal or malignant. Finally, we highlight a vulnerability in leukemic cells that originated from a developmentally important Zmiz1-Notch1 interaction that is hijacked during transformation from normal pre-T cells.

Cellular fate decisions in the developing female anteroventral periventricular nucleus are regulated by canonical Notch signaling

The hypothalamic anteroventral periventricular nucleus (AVPV) is the major regulator of reproductive function within the hypothalamic-pituitary-gonadal (HPG) axis. Despite an understanding of the function of neuronal subtypes within the AVPV, little is known about the molecular mechanisms regulating their development. Previous work from our laboratory has demonstrated that Notch signaling is required in progenitor cell maintenance and formation of kisspeptin neurons of the arcuate nucleus (ARC) while simultaneously restraining POMC neuron number. Based on these findings, we hypothesized that the Notch signaling pathway may act similarly in the AVPV by promoting development of kisspeptin neurons at the expense of other neuronal subtypes. To address this hypothesis, we utilized a genetic mouse model with a conditional loss of Rbpj in Nkx2.1 expressing cells (Rbpj cKO). We noted an increase in cellular proliferation, as marked by Ki-67, in the hypothalamic ventricular zone (HVZ) in Rbpj cKO mice at E13.5. This corresponded to an increase in general neurogenesis and more TH-positive neurons. Additionally, an increase in OLIG2-positive early oligodendrocytic precursor cells was observed at postnatal day 0 in Rbpj cKO mice. By 5 weeks of age in Rbpj cKO mice, TH-positive cells were readily detected in the AVPV but few kisspeptin neurons were present. To elucidate the direct effects of Notch signaling on neuron and glia differentiation, an in vitro primary hypothalamic neurosphere assay was employed. We demonstrated that treatment with the chemical Notch inhibitor DAPT increased mKi67 and Olig2 mRNA expression while decreasing astroglial Gfap expression, suggesting Notch signaling regulates both proliferation and early glial fate decisions. A modest increase in expression of TH in both the cell soma and neurite extensions was observed after extended culture, suggesting that inhibition of Notch signaling alone is enough to bias progenitors towards a dopaminergic fate. Together, these data suggest that Notch signaling restricts early cellular proliferation and differentiation of neurons and oligodendrocytes both in vivo and in vitro and acts as a fate selector of kisspeptin neurons.

A Review of Notch Processing With New Insights Into Ligand-Independent Notch Signaling in T-Cells

The Notch receptor is an evolutionarily highly conserved transmembrane protein essential to a wide spectrum of cellular systems, and its deregulation has been linked to a vast number of developmental disorders and malignancies. Regulated Notch function is critical for the generation of T-cells, in which abnormal Notch signaling results in leukemia. Notch activation through trans-activation of the receptor by one of its ligands expressed on adjacent cells has been well defined. In this canonical ligand-dependent pathway, Notch receptor undergoes conformational changes upon ligand engagement, stimulated by a pulling-force on the extracellular fragment of Notch that results from endocytosis of the receptor-bound ligand into the ligand-expressing cell. These conformational changes in the receptor allow for two consecutive proteolytic cleavage events to occur, which release the intracellular region of the receptor into the cytoplasm. It can then travel to the nucleus, where it induces gene transcription. However, there is accumulating evidence that other pathways may induce Notch signaling. A ligand-independent mechanism of Notch activation has been described in which receptor processing is initiated via cell-internal signals. These signals result in the internalization of Notch into endosomal compartments, where chemical changes existing in this microenvironment result in the conformational modifications required for receptor processing. This review will present mechanisms underlying both canonical ligand-dependent and non-canonical ligand-independent Notch activation pathways and discuss the latter in the context of Notch signaling in T-cells.

Role of Polyamines in Immune Cell Functions

The immune system is remarkably responsive to a myriad of invading microorganisms and provides continuous surveillance against tissue damage and developing tumor cells. To achieve these diverse functions, multiple soluble and cellular components must react in an orchestrated cascade of events to control the specificity, magnitude and persistence of the immune response. Numerous catabolic and anabolic processes are involved in this process, and prominent roles for l-arginine and l-glutamine catabolism have been described, as these amino acids serve as precursors of nitric oxide, creatine, agmatine, tricarboxylic acid cycle intermediates, nucleotides and other amino acids, as well as for ornithine, which is used to synthesize putrescine and the polyamines spermidine and spermine. Polyamines have several purported roles and high levels of polyamines are manifest in tumor cells as well in autoreactive B- and T-cells in autoimmune diseases. In the tumor microenvironment, l-arginine catabolism by both tumor cells and suppressive myeloid cells is known to dampen cytotoxic T-cell functions suggesting there might be links between polyamines and T-cell suppression. Here, we review studies suggesting roles of polyamines in normal immune cell function and highlight their connections to autoimmunity and anti-tumor immune cell function.

Regulation of CD8+ T Cells and Antitumor Immunity by Notch Signaling

Cancer immunosurveillance is critical for the elimination of neoplastic cells. In addition, recent advances in immunological checkpoint blockade drugs have revealed the importance of the immune system in cancer treatment. As a component of the immune system, CD8⁺ T cells have important roles in suppressing tumors. CD8⁺ T cells can kill tumor cells with cytotoxic molecules, such as granzymes and perforin. IFNγ, which is produced by CD8⁺ T cells, can increase the expression of MHC class I antigens by tumor cells, thereby rendering them better targets for CD8⁺ T cells. IFNγ also has crucial functions in enhancing the antitumor abilities of other immune cells. Therefore, it has been hypothesized that antitumor immunity could be improved by modulating the activity of CD8⁺ T cells. The Notch pathway regulates CD8⁺ T cells in multiple ways. It directly upregulates mRNA expression of granzyme B and perforin, enhances differentiation toward short-lived effector cells, and maintains memory T cells. Intriguingly, CD8⁺ T cell-specific Notch2 deletion impairs antitumor immunity, whereas the stimulation of the Notch pathway can increase tumor suppression. In this review, we will summarize the roles of the Notch pathway in CD8⁺ T cells and discuss issues and implications for its use in antitumor immunity.

Inhibition of Notch signalling has ability to alter the proximal and distal TCR signalling events in human CD3+ αβ T-cells

The Notch signalling pathway is an important regulator of T cell function and is known to regulate the effector functions of T cells driven by T cell receptor (TCR). However, the mechanism integrating these pathways in human CD3⁺ αβ T cells is not well understood. The present study was carried out to investigate how Notch and TCR driven signalling are synchronized in human αβ T cells. Differential expression of Notch receptors, ligands, and target genes is observed on human αβ T cells which are upregulated on stimulation with α-CD3/CD28 mAb. Inhibition of Notch signalling by GSI-X inhibited the activation of T cells and affected proximal T cell signalling by regulating CD3-ζ chain expression. Inhibition of Notch signalling decreased the protein expression of CD3-ζ chain and induced expression of E3 ubiquitin ligase (GRAIL) in human αβ T cells. Apart from affecting proximal TCR signalling, Notch signalling also regulated the distal TCR signalling events. In the absence of Notch signalling, α-CD3/CD28 mAb induced activation and IFN-γ production by αβ T cells was down-modulated. The absence of Notch signalling in human αβ T cells inhibited proliferative responses despite strong signalling through TCR and IL-2 receptor. This study shows how Notch signalling cooperates with TCR signalling by regulating CD3-ζ chain expression to support proliferation and activation of human αβ T cells.

Notch Signaling: Linking Embryonic Lung Development and Asthmatic Airway Remodeling

Lung development is mediated by assorted signaling proteins and orchestrated by complex mesenchymal-epithelial interactions. Notch signaling is an evolutionarily conserved cell-cell communication mechanism that exhibits a pivotal role in lung development. Notably, both aberrant expression and loss of regulation of Notch signaling are critically linked to the pathogenesis of various lung diseases, in particular, pulmonary fibrosis, lung cancer, pulmonary arterial hypertension, and asthmatic airway remodeling; implying that precise regulation of intensity and duration of Notch signaling is imperative for appropriate lung development. Moreover, evidence suggests that Notch signaling links embryonic lung development and asthmatic airway remodeling. Herein, we summarized all-recent advances associated with the mechanistic role of Notch signaling in lung development, consequences of aberrant expression or deletion of Notch signaling in linking early-impaired lung development and asthmatic airway remodeling, and all recently investigated potential therapeutic strategies to treat asthmatic airway remodeling.

Pleiotropic Hes-1 Concomitant with its Differential Activation Mediates Neural Stem Cell Maintenance and Radial Glial Propensity in Developing Neocortex

Notch signaling pathway and its downstream effector Hes-1 are well known for their role in cortical neurogenesis. Despite the canonical activation of Hes-1 in developing neocortex, recent advances have laid considerable emphasis on Notch/CBF1-independent Hes-1 (NIHes-1) expression with poor understanding of its existence and functional significance. Here, using reporter systems and in utero electroporation, we could qualitatively unravel the existence of NIHes-1 expressing neural stem cells from the cohort of dependent progenitors throughout the mouse neocortical development. Though Hes-1 expression is maintained in neural progenitor territory at all times, a simple shift from Notch-independent to -dependent state makes it pleiotropic as the former maintains the neural stem cells in a non-dividing/slow-dividing state, whereas the latter is very much required for maintenance and proliferation of radial glial cells. Therefore, our results provide an additional complexity in neural progenitor heterogeneity regarding differential Hes-1 expression in the germinal zone during neo-cortical development.

Hes1: the maestro in neurogenesis

The process of neurogenesis is well orchestrated by the harmony of multiple cues in a spatiotemporal manner. In this review, we focus on how a dynamic gene, Hes1, is involved in neurogenesis with the view of its regulation and functional implications. Initially, we have reviewed the immense functional significance drawn by this maestro during neural development in a context-dependent manner. How this indispensable role of Hes1 in conferring the competency for neural differentiation partly relies on the direct/indirect mode of repression mediated by very specific structural and functional arms of this protein has also been outlined here. We also review the detailed molecular mechanisms behind the well-tuned oscillatory versus sustained expression of this antineurogenic bHLH repressor, which indeed makes it a master gene to implement the elusive task of neural progenitor propensity. Apart from the functional aspects of Hes1, we also discuss the molecular insights into the endogenous regulatory machinery that regulates its expression. Though Hes1 is a classical target of the Notch signaling pathway, we discuss here its differential expression at the molecular, cellular, and/or regional level. Moreover, we describe how its expression is fine-tuned by all possible ways of gene regulation such as epigenetic, transcriptional, post-transcriptional, post-translational, and environmental factors during vertebrate neurogenesis.

High selective pressure for Notch1 mutations that induce Myc in T-cell acute lymphoblastic leukemia

Activating NOTCH1 mutations are frequent in human T-cell acute lymphoblastic leukemia (T-ALL) and Notch inhibitors (γ-secretase inhibitors [GSIs]) have produced responses in patients with relapsed, refractory disease. However, sustained responses, although reported, are uncommon, suggesting that other pathways can substitute for Notch in T-ALL. To address this possibility, we first generated Kras^G12D transgenic mice with T-cell-specific expression of the pan-Notch inhibitor, dominant-negative Mastermind (DNMAML). These mice developed leukemia, but instead of accessing alternative oncogenic pathways, the tumor cells acquired Notch1 mutations and subsequently deleted DNMAML, reinforcing the notion that activated Notch1 is particularly transforming within the context of T-cell progenitors. We next took a candidate approach to identify oncogenic pathways downstream of Notch, focusing on Myc and Akt, which are Notch targets in T-cell progenitors. Kras^G12D mice transduced with Myc developed T-ALLs that were GSI-insensitive and lacked Notch1 mutations. In contrast, Kras^G12D mice transduced with myristoylated AKT developed GSI-sensitive T-ALLs that acquired Notch1 mutations. Thus, Myc can substitute for Notch1 in leukemogenesis, whereas Akt cannot. These findings in primary tumors extend recent work using human T-ALL cell lines and xenografts and suggest that the Notch/Myc signaling axis is of predominant importance in understanding both the selective pressure for Notch mutations in T-ALL and response and resistance of T-ALL to Notch pathway inhibitors.

Signaling in T cells - is anything the m(a)TOR with the picture(s)?

The excitement surrounding checkpoint inhibitors in the treatment of patients with cancer exemplifies a triumph of the long-term value of investing in basic science and fundamental questions of T-cell signaling. The pharmaceutical future actively embraces ways of making more patients’ cancers responsive to these inhibitors. Such a process will be aided by elucidation of signaling and regulation. With thousands of articles spread across almost 30 years, this commentary can touch only on portions of the canonical picture of T-cell signaling and provide a few parables from work on mammalian (or mechanistic) target of rapamycin (mTOR) pathways as they link to early and later phases of lymphocyte activation. The piece will turn a critical eye to some issues with models about these pathways in T cells. Many of the best insights lie in the future despite all that is uncovered already, but a contention is that further therapeutic successes will be fostered by dealing with disparities among findings and attention to the temporal, spatial, and stochastic aspects of T-cell responses. Finally, thoughts on some (though not all) items urgently needed for future progress will be mooted.

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.

Administration of naloxone in combination with recombinant Plasmodium vivax AMA-1 in BALB/c mice induces mixed Th1/Th2 immune responses

Naloxone (NLX) has the ability to shift the immune response to a Th1 profile. Therefore, the adjuvant efficacy of NLX with recombinant P. vivax apical membrane antigen-1(rPvAMA-1) in BALB/c mice was evaluated. Mice were immunized subcutaneously with purified rPvAMA-1 formulated with NLX (doses of 5 mg/kg body weight) alone or in combination with IFA. A significant increase in anti-PvAMA-1 IgG antibody after the second boost (mean OD₄₉₀  = 2·08 and 2·17, in groups received, rPvAMA-1/NLX and rPvAMA-1/NLX/IFA, respectively) was detected. IgG1 and IgG2b were the predominant isotypes in all immunized mouse groups. In immunized mice with rPvAMA-1/NLX (mean: 1036 pg/mL) and with rPvAMA-1/NLX/IFA (mean: 1024 pg/mL), IFN-γ was elicited in response to rPvAMA-1 after the second boost. No detectable IL-4 secretion was determined in all tested groups. In conclusion, the administration of NLX alone or NLX/IFA with rPvAMA-1 in BALB/c mice, which induced mixed Th1/Th2 immune responses, was comparable with that of the same recombinant antigen with CFA/IFA adjuvant. The results indicate that NLX alone may possibly not be considered as a potent Th1 adjuvant in PvAMA-1-based vaccine. However, in order to modulate immune responses from mixed Th1/Th2 to strong and protective Th1 response, further study is warranted on combination of NLX with other adjuvants such as CpG motifs or MPL in proper vaccine formulation. Additionally, dose-response study is necessary to determine the effect of different doses of antigen combined with NLX (at various doses) in Balb/c mice.

Multivalent Forms of the Notch Ligand DLL-1 Enhance Antitumor T-cell Immunity in Lung Cancer and Improve Efficacy of EGFR-Targeted Therapy

Activation of Notch signaling in hematopoietic cells by tumors contributes to immune escape. T-cell defects in tumors can be reversed by treating tumor-bearing mice with multivalent forms of the Notch receptor ligand DLL-1, but the immunologic correlates of this effect have not been elucidated. Here, we report mechanistic insights along with the efficacy of combinational treatments of multivalent DLL-1 with oncoprotein targeting drugs in preclinical mouse models of lung cancer. Systemic DLL-1 administration increased T-cell infiltration into tumors and elevated numbers of CD44(+)CD62L(+)CD8(+) memory T cells while decreasing the number of regulatory T cells and limiting tumor vascularization. This treatment was associated with upregulation of Notch and its ligands in tumor-infiltrating T cells enhanced expression of T-bet and phosphorylation of Stat1/2. Adoptive transfer of T cells from DLL1-treated tumor-bearing immunocompetent hosts into tumor-bearing SCID-NOD immunocompromised mice attenuated tumor growth and extended tumor-free survival in the recipients. When combined with the EGFR-targeted drug erlotinib, DLL-1 significantly improved progression-free survival by inducing robust tumor-specific T-cell immunity. In tissue culture, DLL1 induced proliferation of human peripheral T cells, but lacked proliferative or clonogenic effects on lung cancer cells. Our findings offer preclinical mechanistic support for the development of multivalent DLL1 to stimulate antitumor immunity.

Rbpj-κ mediated Notch signaling plays a critical role in development of hypothalamic Kisspeptin neurons

The mammalian arcuate nucleus (ARC) houses neurons critical for energy homeostasis and sexual maturation. Proopiomelanocortin (POMC) and Neuropeptide Y (NPY) neurons function to balance energy intake and Kisspeptin neurons are critical for the onset of puberty and reproductive function. While the physiological roles of these neurons have been well established, their development remains unclear. We have previously shown that Notch signaling plays an important role in cell fate within the ARC of mice. Active Notch signaling prevented neural progenitors from differentiating into feeding circuit neurons, whereas conditional loss of Notch signaling lead to a premature differentiation of these neurons. Presently, we hypothesized that Kisspeptin neurons would similarly be affected by Notch manipulation. To address this, we utilized mice with a conditional deletion of the Notch signaling co-factor Rbpj-κ (Rbpj cKO), or mice persistently expressing the Notch1 intracellular domain (NICD tg) within Nkx2.1 expressing cells of the developing hypothalamus. Interestingly, we found that in both models, a lack of Kisspeptin neurons are observed. This suggests that Notch signaling must be properly titrated for formation of Kisspeptin neurons. These results led us to hypothesize that Kisspeptin neurons of the ARC may arise from a different lineage of intermediate progenitors than NPY neurons and that Notch was responsible for the fate choice between these neurons. To determine if Kisspeptin neurons of the ARC differentiate similarly through a Pomc intermediate, we utilized a genetic model expressing the tdTomato fluorescent protein in all cells that have ever expressed Pomc. We observed some Kisspeptin expressing neurons labeled with the Pomc reporter similar to NPY neurons, suggesting that these distinct neurons can arise from a common progenitor. Finally, we hypothesized that temporal differences leading to premature depletion of progenitors in cKO mice lead to our observed phenotype. Using a BrdU birthdating paradigm, we determined the percentage of NPY and Kisspeptin neurons born on embryonic days 11.5, 12.5, and 13.5. We found no difference in the timing of differentiation of either neuronal subtype, with a majority occurring at e11.5. Taken together, our findings suggest that active Notch signaling is an important molecular switch involved in instructing subpopulations of progenitor cells to differentiate into Kisspeptin neurons.

The differential expression of IL-4 and IL-13 and its impact on type-2 immunity

Allergic disease represents a significant global health burden, and disease incidence continues to rise in urban areas of the world. As such, a better understanding of the basic immune mechanisms underlying disease pathology are key to developing therapeutic interventions to both prevent disease onset as well as to ameliorate disease morbidity in those individuals already suffering from a disorder linked to type-2 inflammation. Two factors central to type-2 immunity are interleukin (IL)-4 and IL-13, which have been linked to virtually all major hallmarks associated with type-2 inflammation. Therefore, IL-4 and IL-13 and their regulatory pathways represent ideal targets to suppress disease. Despite sharing many common regulatory pathways and receptors, these cytokines perform very distinct functions during a type-2 immune response. This review summarizes the literature surrounding the function and expression of IL-4 and IL-13 in CD4+ T cells and innate immune cells. It highlights recent findings in vivo regarding the differential expression and non-canonical regulation of IL-4 and IL-13 in various immune cells, which likely play important and underappreciated roles in type-2 immunity.

T helper 2 (Th2) cell differentiation, type 2 innate lymphoid cell (ILC2) development and regulation of interleukin-4 (IL-4) and IL-13 production

Interleukin-4 (IL-4), IL-5 and IL-13, the signature cytokines that are produced during type 2 immune responses, are critical for protective immunity against infections of extracellular parasites and are responsible for asthma and many other allergic inflammatory diseases. Although many immune cell types within the myeloid lineage compartment including basophils, eosinophils and mast cells are capable of producing at least one of these cytokines, the production of these "type 2 immune response-related" cytokines by lymphoid lineages, CD4 T helper 2 (Th2) cells and type 2 innate lymphoid cells (ILC2s) in particular, are the central events during type 2 immune responses. In this review, I will focus on the signaling pathways and key molecules that determine the differentiation of naïve CD4 T cells into Th2 cells, and how the expression of Th2 cytokines, especially IL-4 and IL-13, is regulated in Th2 cells. The similarities and differences in the differentiation of Th2 cells, IL-4-producing T follicular helper (Tfh) cells and ILC2s as well as their relationships will also be discussed.

Notch signaling regulates antigen sensitivity of naive CD4+ T cells by tuning co-stimulation

Adaptive immune responses begin when naive CD4(+) T cells engage peptide+major histocompatibility complex class II and co-stimulatory molecules on antigen-presenting cells (APCs). Notch signaling can influence effector functions in differentiated CD4(+) T helper and T regulatory cells. Whether and how ligand-induced Notch signaling influences the initial priming of CD4(+) T cells has not been addressed. We have found that Delta Like Ligand 4 (DLL4)-induced Notch signaling potentiates phosphatidylinositol 3-OH kinase (PI3K)-dependent signaling downstream of the T cell receptor+CD28, allowing naive CD4(+) T cells to respond to lower doses of antigen. In vitro, DLL4-deficient APCs were less efficient stimulators of CD4(+) T cell activation, metabolism, proliferation, and cytokine secretion. With deletion of DLL4 from CD11c(+) APCs in vivo, these deficits translated to an impaired ability to mount an effective CD4(+)-dependent anti-tumor response. These data implicate Notch signaling as an important regulator of adaptive immune responses.

F-box protein FBXW7 inhibits cancer metastasis in a non-cell-autonomous manner

The gene encoding F-box protein FBXW7 is frequently mutated in many human cancers. Although most previous studies have focused on the tumor-suppressive capacity of FBXW7 in tumor cells themselves, we determined that FBXW7 in the host microenvironment also suppresses cancer metastasis. Deletion of Fbxw7 in murine BM-derived stromal cells induced accumulation of NOTCH and consequent transcriptional activation of Ccl2. FBXW7-deficient mice exhibited increased serum levels of the chemokine CCL2, which resulted in the recruitment of both monocytic myeloid-derived suppressor cells and macrophages, thereby promoting metastatic tumor growth. Administration of a CCL2 receptor antagonist blocked the enhancement of metastasis in FBXW7-deficient mice. Furthermore, in human breast cancer patients, FBXW7 expression in peripheral blood was associated with serum CCL2 concentration and disease prognosis. Together, these results suggest that FBXW7 antagonizes cancer development in not only a cell-autonomous manner, but also a non-cell-autonomous manner, and that modulation of the FBXW7/NOTCH/CCL2 axis may provide a potential approach to suppression of cancer metastasis.