Tle corepressors are differentially partitioned to instruct CD8+ T cell lineage choice and identity

The transcriptional cofactor Tle3 reciprocally controls effector and central memory CD8+ T cell fates

Antigen-experienced CD8+ T cells form effector and central memory T cells (TEM and TCM cells, respectively); however, the mechanism(s) controlling their lineage plasticity remains incompletely understood. Here we show that the transcription cofactor Tle3 critically regulates TEM and TCM cell fates and lineage stability through dynamic redistribution in antigen-responding CD8+ T cell genome. Genetic ablation of Tle3 promoted CD8+ TCM cell formation at the expense of CD8+ TEM cells. Lineage tracing showed that Tle3-deficient CD8+ TEM cells underwent accelerated conversion into CD8+ TCM cells while retaining robust recall capacity. Tle3 acted as a coactivator for Tbet to increase chromatin opening at CD8+ TEM cell-characteristic sites and to activate CD8+ TEM cell signature gene transcription, while engaging Runx3 and Tcf1 to limit CD8+ TCM cell-characteristic molecular features. Thus, Tle3 integrated functions of multiple transcription factors to guard lineage fidelity of CD8+ TEM cells, and manipulation of Tle3 activity could favor CD8+ TCM cell production.

Grandmaternal allergen sensitization reprograms epigenetic and airway responses to allergen in second-generation offspring

Asthma susceptibility is influenced by environmental, genetic, and epigenetic factors. DNA methylation is one form of epigenetic modification that regulates gene expression and is both inherited and modified by environmental exposures throughout life. Prenatal development is a particularly vulnerable time period during which exposure to maternal asthma increases asthma risk in offspring. How maternal asthma affects DNA methylation in offspring and what the consequences of differential methylation are in subsequent generations are not fully known. In this study, we tested the effects of grandmaternal house dust mite (HDM) allergen sensitization during pregnancy on airway physiology and inflammation in HDM-sensitized and challenged second-generation mice. We also tested the effects of grandmaternal HDM sensitization on tissue-specific DNA methylation in allergen-naïve and -sensitized second-generation mice. Descendants of both allergen- and vehicle-exposed grandmaternal founders exhibited airway hyperreactivity after HDM sensitization. However, grandmaternal allergen sensitization significantly potentiated airway hyperreactivity and altered the epigenomic trajectory in second-generation offspring after HDM sensitization compared with HDM-sensitized offspring from vehicle-exposed founders. As a result, biological processes and signaling pathways associated with epigenetic modifications were distinct between lineages. A targeted analysis of pathway-associated gene expression found that Smad3 was significantly dysregulated as a result of grandmaternal allergen sensitization. These data show that grandmaternal allergen exposure during pregnancy establishes a unique epigenetic trajectory that reprograms allergen responses in second-generation offspring and may contribute to asthma risk.NEW & NOTEWORTHY Asthma susceptibility is influenced by environmental, genetic, and epigenetic factors. This study shows that maternal allergen exposure during pregnancy promotes unique epigenetic trajectories in second-generation offspring at baseline and in response to allergen sensitization, which is associated with the potentiation of airway hyperreactivity. These effects are one mechanism by which maternal asthma may influence the inheritance of asthma risk.

Decreased Peripheral Blood Lymphocyte Count Predicts Poor Treatment Response in Peritoneal Dialysis-Associated Peritonitis

Purpose

Peripheral blood lymphocyte counts is a pivotal parameter in assessing the host's immune response during maladies and the equilibrium of the immune system which has been found to correlate with various diseases progression and prognosis. However, there was no study on patients with peritoneal dialysis-associated peritonitis (PDAP). We sought to investigate the prognostic value of baseline peripheral blood lymphocyte count in PDAP patients.

Patients and methods

This retrospective study analyzed data from 286 PDAP patients over nine years. Episodes were categorized according to the tertiles of peripheral blood lymphocyte counts (Very Low Lymphocyte Count (VLLC) Group, <0.72×106/L; Low Lymphocyte Count (LLC) Group, 0.72-1.11×106/L; Normal Lymphocyte Count (NLC) Group, ≥ 1.11×106/L). Demographic, laboratory, and infection-related variables were analyzed. Cox regression and generalized estimating equation (GEE) models were used to estimate the association between lymphocyte counts and PDAP treatment failure, which included PD catheter removal and death.

Results

After adjusting for other potential predictors, decreased lymphocyte counts exhibited an incremental relationship with the risk of treatment failure. The VLLC group indicated a 270% (95% CI, 1.168-6.247, P=0.020) and 273% (95% CI, 1.028-7.269, P=0.044) increased venture of treatment failure in Cox regression and GEE analyses, respectively, compared with the NLC group. As a continuous variable, the restricted cubic spline showed a linear negative correlation between lymphocyte counts and the treatment failure risk (P for overall = 0.026). The multivariate model C (combined lymphocyte count with baseline age, sex, dialysis age, Charlson Comorbidity index (CCI), etiology of kidney failure, hemoglobin, albumin, total bilirubin and infection type) showed an area under the curve of 0.824 (95% CI, 0.767-0.881, P=0.001) for the prediction of treatment failure.

Conclusion

Lower lymphocyte counts are linked to increased PDAP treatment failure risk. This highlights lymphocyte count's potential as a prognostic indicator for PDAP.

Intrinsically disordered domain of transcription factor TCF-1 is required for T cell developmental fidelity

In development, pioneer transcription factors access silent chromatin to reveal lineage-specific gene programs. The structured DNA-binding domains of pioneer factors have been well characterized, but whether and how intrinsically disordered regions affect chromatin and control cell fate is unclear. Here, we report that deletion of an intrinsically disordered region of the pioneer factor TCF-1 (termed L1) leads to an early developmental block in T cells. The few T cells that develop from progenitors expressing TCF-1 lacking L1 exhibit lineage infidelity distinct from the lineage diversion of TCF-1-deficient cells. Mechanistically, L1 is required for activation of T cell genes and repression of GATA2-driven genes, normally reserved to the mast cell and dendritic cell lineages. Underlying this lineage diversion, L1 mediates binding of TCF-1 to its earliest target genes, which are subject to repression as T cells develop. These data suggest that the intrinsically disordered N terminus of TCF-1 maintains T cell lineage fidelity.

Tle4 controls both developmental acquisition and early post-natal maturation of corticothalamic projection neuron identity

Identities of distinct neuron subtypes are specified during embryonic development, then maintained during post-natal maturation. In cerebral cortex, mechanisms controlling early acquisition of neuron-subtype identities have become increasingly understood. However, mechanisms controlling neuron-subtype identity stability during post-natal maturation are largely unexplored. We identify that Tle4 is required for both early acquisition and post-natal stability of corticothalamic neuron-subtype identity. Embryonically, Tle4 promotes acquisition of corticothalamic identity and blocks emergence of core characteristics of subcerebral/corticospinal projection neuron identity, including gene expression and connectivity. During the first post-natal week, when corticothalamic innervation is ongoing, Tle4 is required to stabilize corticothalamic neuron identity, limiting interference from differentiation programs of developmentally related neuron classes. We identify a deacetylation-based epigenetic mechanism by which TLE4 controls Fezf2 expression level by corticothalamic neurons. This contributes to distinction of cortical output subtypes and ensures identity stability for appropriate maturation of corticothalamic neurons.

TLE3 and TLE4-coordinated colonic macrophage-CD4+ T cell crosstalk maintains intestinal immune homeostasis

Colonic macrophages are critical for maintenance of cluster of differentiation 4 T helper (CD4⁺ T) cell homeostasis in the intestinal lamina propria. However, the mechanisms by which this process is regulated at the transcriptional level remain unknown. In this study, we found that the transcriptional corepressors transducin-like enhancer of split (TLE)3 and TLE4, but not TLE1 or TLE2, in colonic macrophages controlled homeostasis of CD4⁺ T-cell pool in the colonic lamina propria. Mice lacking TLE3 or TLE4 in myeloid cells exhibited markedly increased numbers of regulatory T (T_reg) and T helper (T_H) 17 cells under homeostatic conditions, rendering them more resistant to experimental colitis. Mechanistically, TLE3 and TLE4 negatively regulated matrix metalloproteinase (Mmp)9 transcription in colonic macrophages. Tle3 or Tle4 deficiency in colonic macrophages resulted in upregulated MMP9 production and thus enhanced latent transforming growth factor-beta (TGF-β) activation, which subsequently led to T_reg and T_H17 cell expansion. These results advanced our knowledge regarding the intricate crosstalk between the intestinal innate and adaptive immune compartments.

Functional heterogeneity in the memory B-cell response

Most vaccines induce robust antibody and memory B-cell (MBC) responses that are capable of mediating protective immunity. However, antibody titers wane following vaccination necessitating the administration of booster vaccines to maintain a protective antibody titer. MBCs are stably maintained following vaccination and can rapidly give rise to antibody-secreting cells or undergo further affinity maturation upon antigen re-encounter. Repeated antigen encounter results in the development of MBCs that encode antibodies capable of mediating broadly protective immunity against viruses such as SARS-CoV-2 and influenza. Here, we summarize emerging evidence that MBCs are a heterogeneous population composed of transcriptionally and phenotypically distinct subsets that have discrete roles in mediating protective immunity upon antigen re-encounter and examine the implications of these findings for the development of vaccines capable of eliciting broadly protective immunity.

Roles of transducin-like enhancer of split (TLE) family proteins in tumorigenesis and immune regulation

Mammalian transducin-like enhancer of split family proteins (TLEs) are homologous to Drosophila Groucho (Gro) and are essential transcriptional repressors. Seven TLE family members, TLE1-7, have been identified to date. These proteins do not bind DNA directly; instead, they bind a set of transcription factors and thereby inhibit target gene expression. Loss of TLEs in mice usually leads to defective early development; however, TLE functions in developmentally mature cells are unclear. Recent studies have revealed that TLEs are dysregulated in certain human cancer types and may function as oncogenes or tumor suppressors in different contexts. TLE levels also affect the efficacy of cancer treatments and the development of drug resistance. In addition, TLEs play critical roles in the development and function of immune cells, including macrophages and lymphocytes. In this review, we provide updates on the expression, function, and mechanism of TLEs; discuss the roles played by TLEs in tumorigenesis and the inflammatory response; and elaborate on several TLE-associated signaling pathways, including the Notch, Wnt, and MAPK pathways. Finally, we discuss potential strategies for targeting TLEs in cancer therapy.

TCF1 in T cell immunity: a broadened frontier

TCF1 and its homologue LEF1 are historically known as effector transcription factors downstream of the WNT signalling pathway and are essential for early T cell development. Recent advances bring TCF1 into the spotlight for its versatile, context-dependent functions in regulating mature T cell responses. In the cytotoxic T cell lineages, TCF1 is required for the self-renewal of stem-like CD8⁺ T cells generated in response to viral or tumour antigens, and for preserving heightened responses to checkpoint blockade immunotherapy. In the helper T cell lineages, TCF1 is indispensable for the differentiation of T follicular helper and T follicular regulatory cells, and crucially regulates immunosuppressive functions of regulatory T cells. Mechanistic investigations have also identified TCF1 as the first transcription factor that directly modifies histone acetylation, with the capacity to bridge transcriptional and epigenetic regulation. TCF1 also has the potential to become an important clinical biomarker for assessing the prognosis of tumour immunotherapy and the success of viral control in treating HIV and hepatitis C virus infection. Here, we summarize the key findings on TCF1 across the fields of T cell immunity and reflect on the possibility of exploring TCF1 and its downstream transcriptional programmes as therapeutic targets for improving antiviral and antitumour immunity.

Host T cell dedifferentiation effects drive HIV-1 latency stability

The development of therapies to eliminate the latent HIV-1 reservoir is hampered by our incomplete understanding of the biomolecular mechanism governing HIV-1 latency. To further complicate matters, recent single cell RNA-seq studies reported extensive heterogeneity between latently HIV-1-infected primary T cells, implying that latent HIV-1 infection can persist in greatly differing host cell environments. We here show that transcriptomic heterogeneity is also found between latently infected T cell lines, which allowed us to study the underlying mechanisms of intercell heterogeneity at high signal resolution. Latently infected T cells exhibited a de-differentiated phenotype, characterized by the loss of T cell-specific markers and gene regulation profiles reminiscent of hematopoietic stem cells (HSC). These changes had functional consequences. As reported for stem cells, latently HIV-1 infected T cells efficiently forced lentiviral superinfections into a latent state and favored glycolysis. As a result, metabolic reprogramming or cell re-differentiation destabilized latent infection. Guided by these findings, data-mining of single cell RNA-seq data of latently HIV-1 infected primary T cells from patients revealed the presence of similar dedifferentiation motifs. >20% of the highly detectable genes that were differentially regulated in latently infected cells were associated with hematopoietic lineage development (e.g. HUWE1, IRF4, PRDM1, BATF3, TOX, ID2, IKZF3, CDK6) or were hematopoietic markers (SRGN; hematopoietic proteoglycan core protein). The data add to evidence that the biomolecular phenotype of latently HIV-1 infected cells differs from normal T cells and strategies to address their differential phenotype need to be considered in the design of therapeutic cure interventions. IMPORTANCE HIV-1 persists in a latent reservoir in memory CD4 T cells for the lifetime of a patient. Understanding the biomolecular mechanisms used by the host cells to suppress viral expression will provide essential insights required to develop curative therapeutic interventions. Unfortunately, our current understanding of these control mechanisms is still limited. By studying gene expression profiles, we demonstrated that latently HIV-1-infected T cells have a de-differentiated T cell phenotype. Software-based data integration allowed for the identification of drug targets that would re-differentiate viral host cells and, in extension, destabilize latent HIV-1 infection events. The importance of the presented data lies within the clear demonstration that HIV-1 latency is a host cell phenomenon. As such, therapeutic strategies must first restore proper host cell functionality to accomplish efficient HIV-1 reactivation.

Transcriptomic analysis revealed increased expression of genes involved in keratinization in the tears of COVID-19 patients

Recent studies have focused their attention on conjunctivitis as one of the symptoms of coronavirus disease 2019 (COVID-19). Therefore, tear samples were taken from COVID-19 patients and the presence of SARS-CoV-2 was evidenced using Real Time reverse transcription polymerase chain reaction. The main aim of this study was to analyze mRNA expression in the tears of patients with COVID-19 compared with healthy subjects using Next Generation Sequencing (NGS). The functional evaluation of the transcriptome highlighted 25 genes that differ statistically between healthy individuals and patients affected by COVID-19. In particular, the NGS analysis identified the presence of several genes involved in B cell signaling and keratinization. In particular, the genes involved in B cell signaling were downregulated in the tears of COVID-19 patients, while those involved in keratinization were upregulated. The results indicated that SARS-CoV-2 may induce a process of ocular keratinization and a defective B cell response.

The prognostic role of the Transducin-like Enhancer of split protein family in lung adenocarcinoma

Background

Lung cancer claims more lives than any other cancer worldwide. Lung adenocarcinoma (LUAD) accounts for approximately 40% of all lung cancers. Members of the Transducin-like Enhancer of split (TLE) protein family repress transcription through multiple mechanisms; however, their prognostic value in LUAD is still unclear.

Methods

A dataset from The Cancer Genome Atlas was used to analyze the relationship between the expression of TLE family members and outcomes of LUAD. The expression of TLE family members in 59 normal and 513 tumor samples in the TCGA dataset was selected. For paired analysis, 57 normal and 57 tumor paired tissues were selected. Gene Ontology (GO) term and Reactome pathway enrichment analyses of the TLE family members were performed. Progression-free survival (PFS) and overall survival (OS) served as endpoints in this study. All statistical analyses were performed with R 3.6.0.

Results

The expression levels of TLE family proteins differed between 59 normal and 513 tumor samples. High TLE1 and low TLE2 levels were associated with poor progression-free and OS (all P<0.050). Multivariate analysis demonstrated that high TLE1 expression and low TLE2 expression were independent risk factors for a poor outcome in LUAD. Moreover, the combined expression of these two proteins was a good tool for prognostication.

Conclusions

High TLE1 expression and low TLE2 are independent adverse prognostic factors in LUAD and can serve as prognostic biomarkers.

The pioneer transcription factors Foxa1 and Foxa2 regulate alternative RNA splicing during thymocyte positive selection

During positive selection at the transition from CD4+CD8+ double-positive (DP) to single-positive (SP) thymocyte, TCR signalling results in appropriate MHC restriction and signals for survival and progression. We show that the pioneer transcription factors Foxa1 and Foxa2 are required to regulate RNA splicing during positive selection of mouse T cells and that Foxa1 and Foxa2 have overlapping/compensatory roles. Conditional deletion of both Foxa1 and Foxa2 from DP thymocytes reduced positive selection and development of CD4SP, CD8SP and peripheral naïve CD4+ T cells. Foxa1 and Foxa2 regulated the expression of many genes encoding splicing factors and regulators, including Mbnl1, H1f0, Sf3b1, Hnrnpa1, Rnpc3, Prpf4b, Prpf40b and Snrpd3. Within the positively selecting CD69+DP cells, alternative RNA splicing was dysregulated in the double Foxa1/Foxa2 conditional knockout, leading to >850 differentially used exons. Many genes important for this stage of T-cell development (Ikzf1-3, Ptprc, Stat5a, Stat5b, Cd28, Tcf7) and splicing factors (Hnrnpab, Hnrnpa2b1, Hnrnpu, Hnrnpul1, Prpf8) showed multiple differentially used exons. Thus, Foxa1 and Foxa2 are required during positive selection to regulate alternative splicing of genes essential for T-cell development, and, by also regulating splicing of splicing factors, they exert widespread control of alternative splicing.

Transcriptional repression by FEZF2 restricts alternative identities of cortical projection neurons

Projection neuron subtype identities in the cerebral cortex are established by expressing pan-cortical and subtype-specific effector genes that execute terminal differentiation programs bestowing neurons with a glutamatergic neuron phenotype and subtype-specific morphology, physiology, and axonal projections. Whether pan-cortical glutamatergic and subtype-specific characteristics are regulated by the same genes or controlled by distinct programs remains largely unknown. Here, we show that FEZF2 functions as a transcriptional repressor, and it regulates subtype-specific identities of both corticothalamic and subcerebral neurons by selectively repressing expression of genes inappropriate for each neuronal subtype. We report that TLE4, specifically expressed in layer 6 corticothalamic neurons, is recruited by FEZF2 to inhibit layer 5 subcerebral neuronal genes. Together with previous studies, our results indicate that a cortical glutamatergic identity is specified by multiple parallel pathways active in progenitor cells, whereas projection neuron subtype-specific identity is achieved through selectively repressing genes associated with alternate identities in differentiating neurons.

TFH cells depend on Tcf1-intrinsic HDAC activity to suppress CTLA4 and guard B-cell help function

Precise regulation of coinhibitory receptors is essential for maintaining immune tolerance without interfering with protective immunity, yet the mechanism underlying such a balanced act remains poorly understood. In response to protein immunization, T follicular helper (T_FH) cells lacking Tcf1 and Lef1 transcription factors were phenotypically normal but failed to promote germinal center formation and antibody production. Transcriptomic profiling revealed that Tcf1/Lef1-deficient T_FH cells aberrantly up-regulated CTLA4 and LAG3 expression, and treatment with anti-CTLA4 alone or combined with anti-LAG3 substantially rectified B-cell help defects by Tcf1/Lef1-deficient T_FH cells. Mechanistically, Tcf1 and Lef1 restrain chromatin accessibility at the Ctla4 and Lag3 loci. Groucho/Tle corepressors, which are known to cooperate with Tcf/Lef factors, were essential for T_FH cell expansion but dispensable for repressing coinhibitory receptors. In contrast, mutating key amino acids in histone deacetylase (HDAC) domain in Tcf1 resulted in CTLA4 derepression in T_FH cells. These findings demonstrate that Tcf1-instrinsic HDAC activity is necessary for preventing excessive CTLA4 induction in protein immunization-elicited T_FH cells and hence guarding their B-cell help function.

Waiting in the wings: RUNX3 reveals hidden depths of immune regulation with potential implications for inflammatory bowel disease

BACKGROUND

Complex interactions between the environment and the mucosal immune system underlie inflammatory bowel disease (IBD). The involved cytokine signalling pathways are modulated by a number of transcription factors, one of which is runt-related transcription factor 3 (RUNX3).

OBJECTIVE

To systematically review the immune roles of RUNX3 in immune regulation, with a focus on the context of IBD.

METHODS

Relevant articles and reviews were identified through a Scopus search in April 2020. Information was categorized by immune cell types, analysed and synthesized. IBD transcriptome data sets and FANTOM5 regulatory networks were processed in order to complement the literature review.

RESULTS

The available evidence on the immune roles of RUNX3 allowed for its description in twelve cell types: intraepithelial lymphocyte, Th1, Th2, Th17, Treg, double-positive T, cytotoxic T, B, dendritic, innate lymphoid, natural killer and macrophages. In the gut, the activity of RUNX3 is multifaceted and context-dependent: it may promote homeostasis or exacerbated reactions via cytokine signalling and regulation of receptor expression. RUNX3 is mostly engaged in pathways involving ThPOK, T-bet, IFN-γ, TGF-β/IL-2Rβ, GATA/CBF-β, SMAD/p300 and a number of miRNAs. RUNX3 targets relevant to IBD may include RAG1, OSM and IL-17B. Moreover, in IBD RUNX3 expression correlates positively with GZMM, and negatively with IFNAR1, whereas in controls, it strongly associates with TGFBR3.

CONCLUSIONS

Dysregulation of RUNX3, mostly in the form of deficiency, likely contributes to IBD pathogenesis. More clinical research is needed to examine RUNX3 in IBD.

Effect of radiotherapy on T cell and PD-1 / PD-L1 blocking therapy in tumor microenvironment

Cancer is a worldwide problem that threatens human health. Radiotherapy plays an important role in a variety of cancer treatment methods. The administration of radiotherapy can alter the differentiation pathways and functions of T cells, which in turn improves the immune response of T cells. Radiotherapy can also induce up-regulation of PD-L1 expression, which means that it has great potential for enhancing the therapeutic effect of anti-PD-1/PD-L1 inhibitors and reducing the risk of drug resistance toward them. At present, the combination of radiotherapy and anti-PD-1/PD-L1 inhibitors has shown significant therapeutic effects in clinical tumor research. This review focuses on the mechanism of radiotherapy on T cells reported in recent years, as well as related research progress in the application of PD-1/PD-L1 blockers. It will provide a theoretical basis for the rational clinical application of radiotherapy combined with PD-1/PD-L1 inhibitors.

Transcriptional regulation of memory B cell differentiation

Memory B cells (MBCs) are critical for the rapid development of protective immunity following re-infection. MBCs capable of neutralizing distinct subclasses of pathogens, such as influenza and HIV, have been identified in humans. However, efforts to develop vaccines that induce broadly protective MBCs to rapidly mutating pathogens have not yet been successful. Better understanding of the signals regulating MBC development and function are essential to overcome current challenges hindering successful vaccine development. Here, we discuss recent advancements regarding the signals and transcription factors regulating germinal centre-derived MBC development and function.

The transcription factor Hhex cooperates with the corepressor Tle3 to promote memory B cell development

Memory B cells (MBCs) are essential for long-lived humoral immunity. However, the transcription factors involved in MBC differentiation are poorly defined. Here, using single-cell RNA sequencing analysis, we identified a population of germinal center (GC) B cells in the process of differentiating into MBCs. Using an inducible CRISPR-Cas9 screening approach, we identified the hematopoietically expressed homeobox protein Hhex as a transcription factor regulating MBC differentiation. The corepressor Tle3 was also identified in the screen and was found to interact with Hhex to promote MBC development. Bcl-6 directly repressed Hhex in GC B cells. Reciprocally, Hhex-deficient MBCs exhibited increased Bcl6 expression and reduced expression of the Bcl-6 target gene Bcl2. Overexpression of Bcl-2 was able to rescue MBC differentiation in Hhex-deficient cells. We also identified Ski as an Hhex-induced transcription factor involved in MBC differentiation. These findings establish an important role for Hhex-Tle3 in regulating the transcriptional circuitry governing MBC differentiation.

Twist2 promotes CD8+ T-cell differentiation by repressing ThPOK expression

CD4/CD8 T-cell lineage differentiation is a key process in immune system development; however, a defined regulator(s) that converts the signal from T-cell receptor and co-receptor complexes into lineage differentiation remains unclear. Here, we show that Twist2 is a critical factor in CD4/CD8 thymocyte differentiation. Twist2 expression is differentially regulated by T-cell receptor signaling, leading to differentiation into the CD4 or CD8 lineage. Forced Twist2 expression perturbed CD4⁺ thymocyte differentiation while enhancing CD8⁺ thymocyte differentiation. Furthermore, Twist2 expression produced mature CD8⁺ thymocytes in B₂m^-/- mice, while its deficiency significantly impaired CD8⁺ cells in MHC class-II^-/- and TCR transgenic mice, favoring CD8 T-cell differentiation. During CD8 lineage differentiation, Twist2 interacted with Runx3 to bind to the silencer region of the ThPOK locus, thereby blocking ThPOK expression. These findings indicate that Twist2 is a part of the transcription factor network controlling CD8 lineage differentiation.

Transducin-Like Enhancer of Split-1 Inhibits Malignant Behaviors in vitro and Predicts a Better Prognosis in Pancreatic Ductal Adenocarcinoma

Background: Transducin-like enhancer of split-1 (TLE1), a member of the Groucho/TLE family of transcriptional corepressors, has been reported to be involved in the tumorigenesis of various cancers and function as a clinical prognostic indicator. However, the mechanisms and prognostic significance of TLE1 in pancreatic ductal adenocarcinoma (PDAC) have not been elucidated. Methods: In this study, western blot analyses and real-time polymerase chain reaction (RT-PCR) were employed to evaluate the expression of TLE1 and related proteins in PDAC cell lines. Wound healing, transwell migration and invasion, and Cell Counting Kit-8 (CCK-8) assays were used to determine cell line-specific differences in metastasis and proliferation. Flow cytometry was performed for cell cycle detection. RNA sequencing and bioinformatics were undertaken to explore the molecular mechanisms and potential targeted molecules of TLE1. TLE1 expression in tumor and para-tumor tissues was evaluated by tissue microarray-based immunohistochemistry using a semiquantitative method (H-score) in 262 patients with radical PDAC resection. Correlation, Kaplan-Meier survival, univariate, and multivariate analyses were also performed. Results: Our findings showed that TLE1 expression was common in PDAC cell lines. Upregulation of TLE1 inhibited PDAC cell migration, invasion, and proliferation in vitro by delaying the G0/G1 transition. Immunohistochemistry revealed that TLE1 was specifically expressed in the nucleus and at higher levels in tumor tissues compared with para-tumor tissues. Generally, high TLE1 expression was associated with no vascular invasion. In univariate analyses, high TLE1 expression was associated with longer disease-specific survival (DSS) in all patients and in 16 patient subgroups. In multivariate analyses, TLE1 expression was independently associated with DSS in all patients and four patient subgroups. Conclusion: In conclusion, these results suggest that TLE1 has an inhibitory role in PDAC progression and is a favorable prognostic indicator for patients with resectable PDAC.

Ectopic Tcf1 expression instills a stem-like program in exhausted CD8+ T cells to enhance viral and tumor immunity

Exhausted CD8⁺ T (Tex) cells are dysfunctional due to persistent antigen exposure in chronic viral infection and tumor contexts. A stem cell-like Tex (Tex-stem) subset can self-renew and differentiate into terminally exhausted (Tex-term) cells. Here, we show that ectopic Tcf1 expression potently promoted the generation of Tex-stem cells in both a chronic viral infection and preclinical tumor models. Tcf1 overexpression diminished coinhibitory receptor expression and enhanced polycytokine-producing capacity while retaining a heightened responses to checkpoint blockade, leading to enhanced viral and tumor control. Mechanistically, ectopically expressed Tcf1 exploited existing and novel chromatin accessible sites as transcriptional enhancers or repressors and modulated the transcriptome by enforcing pre-existing expression patterns in Tex-stem cells, such as enhanced suppression of Blimp1 and Bim and acquisition of new downstream genes, including Mx1, Tox2, and Runx3. These findings reveal a pronounced impact of ectopic Tcf1 expression on Tex functional restoration and highlight the therapeutic potential of harnessing Tcf1-enforced transcriptional programs.

The Roles of RUNX Family Proteins in Development of Immune Cells

The Runt-related transcription factors (RUNX) transcription factors have been known for their critical roles in numerous developmental processes and diseases such as autoimmune disorders and cancer. Especially, RUNX proteins are best known for their roles in hematopoiesis, particularly during the development of T cells. As scientists discover more types of new immune cells, the functional diversity of RUNX proteins also has been increased over time. Furthermore, recent research has revealed complicated transcriptional networks involving RUNX proteins by the current technical advances. Databases established by next generation sequencing data analysis has identified ever increasing numbers of potential targets for RUNX proteins and other transcription factors. Here, we summarize diverse functions of RUNX proteins mainly on lymphoid lineage cells by incorporating recent discoveries.

Molecular networks of FOXP family: dual biologic functions, interplay with other molecules and clinical implications in cancer progression

Though Forkhead box P (FOXP) transcription factors comprising of FOXP1, FOXP2, FOXP3 and FOXP4 are involved in the embryonic development, immune disorders and cancer progression, the underlying function of FOXP3 targeting CD4 + CD25+ regulatory T (Treg) cells and the dual roles of FOXP proteins as an oncogene or a tumor suppressor are unclear and controversial in cancers to date. Thus, the present review highlighted research history, dual roles of FOXP proteins as a tumor suppressor or an oncogene, their molecular networks with other proteins and noncoding RNAs, cellular immunotherapy targeting FOXP3, and clinical implications in cancer progression.

Critical Role for TCR Signal Strength and MHC Specificity in ThPOK-Induced CD4 Helper Lineage Choice

Sustained TCR signaling is critical for ThPOK induction in MHC class II (MHCII)-signaled thymocytes leading to the CD4 helper lineage commitment. ThPOK suppresses the cytotoxic program in the signaled thymocytes and is shown to be necessary and sufficient for the CD4 helper lineage choice. Accordingly, loss and gain of ThPOK function redirects MHCII- and MHC class I (MHCI)-signaled thymocytes into the CD8 cytotoxic and CD4 helper lineage, respectively. However, the impact of a defined ThPOK level on the CD4 helper lineage choice of MHCII- and MHCI-specific thymocytes and the role of TCR signaling in this process is not evaluated. Equally, it is not clear if suppression of the cytotoxic program by ThPOK is sufficient in redirecting MHCI-restricted thymocytes into the CD4 helper lineage. In this study, we have investigated CD8 to CD4 helper lineage redirection in three independent ThPOK overexpressing transgenic mouse lines. Our analysis shows that one of the transgenic lines, despite overexpressing ThPOK compared with wild-type CD4 mature T cells and compromising cytotoxic program, failed to redirect all MHCI-signaled thymocytes into the CD4 helper lineage, resulting in the continued presence of CD8⁺ mature T cells and the generation of a large number of double negative mature T cells. Critically, the same ThPOK transgene completely restored the CD4 helper lineage commitment of MHCII-specific Thpok ^-/- thymocytes. Importantly, augmenting TCR signaling significantly enhanced the ThPOK-mediated CD4 helper lineage choice of MHCI-specific thymocytes but was still substantially less efficient than that of MHCII-specific thymocytes expressing the same amount of ThPOK. Together, these data suggest that the ThPOK-induced CD4 helper lineage commitment is strongly influenced by TCR signal strength and MHC specificity of developing thymocytes.

Tcf1 and Lef1 are required for the immunosuppressive function of regulatory T cells

Tcf1 and Lef1 are underexpressed in T reg cells compared with conventional CD4⁺ T cells. Xing et al. demonstrate that genetic ablation of both factors impairs immunosuppressive function of T reg cells and leads to spontaneous multi-organ autoimmunity.

Tcf1 and Lef1 have versatile functions in regulating T cell development and differentiation, but intrinsic requirements for these factors in regulatory T (T reg) cells remain to be unequivocally defined. Specific ablation of Tcf1 and Lef1 in T reg cells resulted in spontaneous multi-organ autoimmunity that became more evident with age. Tcf1/Lef1-deficient T regs showed reduced protection against experimentally induced colitis, indicative of diminished immuno-suppressive capacity. Transcriptomic analysis revealed that Tcf1 and Lef1 were responsible for positive regulation of a subset of T reg–overrepresented signature genes such as Ikzf4 and Izumo1r. Unexpectedly, Tcf1 and Lef1 were necessary for restraining expression of cytotoxic CD8⁺ effector T cell–associated genes in T reg cells, including Prdm1 and Ifng. Tcf1 ChIP-seq revealed substantial overlap between Tcf1 and Foxp3 binding peaks in the T reg cell genome, with Tcf1-Foxp3 cooccupancy observed at key T reg signature and cytotoxic effector genes. Our data collectively indicate that Tcf1 and Lef1 are critical for sustaining T reg suppressive functions and preventing loss of self-tolerance.