Effector Transcription Factors Research Articles

NMDA Suppresses Pancreatic ABCA1 Expression through the MEK/ERK/LXR Pathway in Pancreatic Beta Cells.

Dysfunction or loss of pancreatic β cells can cause insulin deficiency and impaired glucose regulation, resulting in conditions like type 2 diabetes. The ATP-binding cassette transporter A1 (ABCA1) plays a key role in the reverse cholesterol transport system, and its decreased expression is associated with pancreatic β cell lipotoxicity, resulting in abnormal insulin synthesis and secretion. Increased glutamate release can cause glucotoxicity in β cells, though the detailed mechanisms remain unclear. This study investigated the effect of N-methyl-D-aspartic acid (NMDA) on ABCA1 expression in INS-1 cells and primary pancreatic islets to elucidate the signaling mechanisms that suppress insulin secretion. Using Western blotting, microscopy, and biochemical analyses, we found that NMDA activated the mitogen-activated protein kinase (MEK)-dependent pathway, suppressing ABCA1 protein and mRNA expression. The MEK-specific inhibitor PD98059 restored ABCA1 promoter activity, indicating the involvement of the extracellular signal-regulated kinase (MEK/ERK) pathway. Furthermore, we identified the liver X receptor (LXR) as an effector transcription factor in NMDA regulation of ABCA1 transcription. NMDA treatment increased cholesterol and triglyceride levels while decreasing insulin secretion, even under high-glucose conditions. These effects were abrogated by treatment with PD98059. This study reveals that NMDA suppresses ABCA1 expression via the MEK/ERK/LXR pathway, providing new insights into the pathological suppression of insulin secretion in pancreatic β cells and emphasizing the importance of investigating the role of NMDA in β cell dysfunction.

Association of overexpression of TNF receptor superfamily members (CD40, BAFFR, LTβR and RANK) with favorable prognosis in patients with colorectal adenocarcinoma.

e15516 Background: Numerous studies by our and other groups have highlighted the implication of NF-κB in colorectal cancer (CRC) through the deterioration of classical and alternative pathway signaling. The alternative pathway of NF-κB can be activated by members of TNF superfamily, such as lymphotoxin β (LTβ), tumor necrosis factor ligand superfamily member 5 (CD40L), B-cell activation factor (BAFF) and receptor activator of NF-κB ligand (RANKL). We have previously shown that alternative pathway of NF-κΒ is deteriorated in CRC. In the present study, we investigated the clinical significance of the aforementioned receptors in patients with CRC as well as their relation with effector transcription factors NF-κB2 and RELB. Methods: Gene expression of CD40, BAFFR, LT β R, RANK, NF- κ B2 and RELB, quantified by using real-time qRT-PCT and specific primers and probes, was assessed in 97 cancerous and 61 paired non-neoplastic tumor-adjacent formalin-fixed paraffin-embedded (FFPE) tissue specimens from CRC patients who were surgically managed in the University Hospital of Patras, Greece. Concurrently, we assessed protein expression of the same molecules by immunohistochemistry in the same cohort of patients. Both, mRNA and protein levels of the receptors were analyzed in association with clinicopathological parameters and clinical outcome of the patients in terms of time to disease progression. Results: Cytoplasmic expression of all molecules was higher in cancer compared to tumor-adjacent epithelial cells ( p= 0.047 for CD40, p= 0.007 for BAFFR, p< 0.001 for LTβR and p= 0.003 for RANK) and in stromal cells ( p< 0.001 for all molecules), while the reverse pattern (lower in neoplastic epithelial cells) was observed for nuclear expression ( p< 0.001 for all molecules). Similarly, mRNA levels of LTβR and RANK were higher in cancer compared to adjacent non-neoplastic tissues ( p= 0.019 and p= 0.037, respectively). Notably, patients with high mRNA levels of all studied receptors had significantly longer time to disease progression ( p= 0.026 for CD40, p= 0.023 for BAFFR, p= 0.027 for LTβR and p= 0.038 for RANK). In addition, mRNA levels of BAFFR, LTβR and RANK levels were higher in ulcerative tumors compared to polypoid tumors ( p= 0.002, p= 0.005 and p= 0.011, respectively). RELB mRNA levels were positively correlated with mRNA levels of CD40, BAFFR and LTβR in cancerous ( p< 0.001 for all molecules) and non-cancerous tissues (p < 0.001 for all molecules). Surprisingly, NF-κB2 mRNA levels were positively correlated with BAFFR and LTβR mRNA levels in malignant tissues, while in non-malignant tissues were positively correlated with all receptors’ mRNA levels ( p< 0.001 for all molecules). Conclusions: This study suggests a prognostic value for CD40, BAFFR, LTβR and RANK expression in patients with CRC and further supports the role of the alternative pathway of NF-κB in CRC.

Two sequential gene expression programs bridged by cell division support long-distance collective cell migration.

The precise assembly of tissues and organs relies on spatiotemporal regulation of gene expression to coordinate the collective behavior of cells. In Drosophila embryos, the midgut musculature is formed through collective migration of caudal visceral mesoderm (CVM) cells, but how gene expression changes as cells migrate is not well understood. Here, we have focused on ten genes expressed in the CVM and the cis-regulatory sequences controlling their expression. Although some genes are continuously expressed, others are expressed only early or late during migration. Late expression relates to cell cycle progression, as driving string/Cdc25 causes earlier division of CVM cells and accelerates the transition to late gene expression. In particular, we found that the cell cycle effector transcription factor E2F1 is a required input for the late gene CG5080. Furthermore, whereas late genes are broadly expressed in all CVM cells, early gene transcripts are polarized to the anterior or posterior ends of the migrating collective. We show this polarization requires transcription factors Snail, Zfh1 and Dorsocross. Collectively, these results identify two sequential gene expression programs bridged by cell division that support long-distance directional migration of CVM cells.

Myocardial injury causes changes in the transcriptional and regulatory landscape of adaptive immune cells in the heart

Abstract Background Ischaemic heart disease is a leading cause of heart failure (HF) and despite advanced therapeutic options, morbidity and mortality rates remain high. Acute inflammation after myocardial infarction (MI) has been thoroughly studied in recent years and persistent immune-mediated damage has been suggested as a factor contributing to the development of HF. T and B cells are critical mediators of adaptive immune responses after MI, however a thorough analysis of their transcriptomic phenotypes in the heart at baseline and over time after injury are missing. Purpose Here, we aim to understand the transcriptional activity of B and T cells in the post-MI heart, in order to characterize their role in maintaining post-MI autoreactivity. Methods We obtained single cell RNA sequencing data of mouse and human hearts from Forte et al (2020), Martini et al (2019) and Litviňuková et al (2020) and performed differential expression analysis, gene regulatory inferences and trajectory-based differential expression analysis. Results Myocardial T cells subclustered into CD8+, CD4+, CD20+ and NK lineages with naïve, memory and effector functions (Fig. 1). The B cell population was divided into immature, plasma, memory, collagen-producing and B1 cell subgroups (Fig. 2). At baseline, despite a striking presence of effector populations, both B and T cells are governed by homeostatic and tolerance-promoting transcription factors (Deaf1, Ikzf1 and Nr1h3 for T cells and Spi-B as well as Bcl11 for B cells). Post-MI, the activity of transcription factors concerned with differentiation and proliferation increased. T cells express transcripts for proinflammatory chemokines and cytokines (Ccr7, Ccl5, Ifng and Tnf) as well as granzymes and perforin up until 28 days post-MI (Gzma and Prf1). Surprisingly, B cells upregulate collagen transcript levels 5-7 days post-MI (Col1a, Col5a, and Col4a) and regulon analysis supports that B cells increase the activity of transcription factors necessary for collagen production (Ets-1 and Krox20). Both B and T cells remain persistently activated post MI. 28 days post-MI T cells have increased activity of proinflammatory (Nfkb1) and cytokine producing (Crem and Rel) transcription factors, whereas B cells have increase maturation (Nfkb1), autoantibody production (Stat3 and Rel) and memory (Stat5b) transcription factor activity. Conclusion Collectively, our data shows that there are effector immune cell populations present at baseline, which are governed by homeostatic transcription factors. Post-MI, effector transcription factors are upregulated in both T cells and B cells, which promote proliferation, differentiation, cytokine production and in the case of B cells, collagen production. Even after resolution of acute inflammation, both the T and B cell population do not return fully to baseline but remain at a state of persistent activation, as effector transcription factors remain upregulated.

Iron Restriction Alleviates β-Thalassemia By Stimulating ULK1-Mediated Autophagy of Free α-Globin

In β-thalassemia, mutations in the HBB gene cause reduced β-globin synthesis with accumulation of toxic free α-globin, leading to ineffective erythropoiesis and hemolysis. We showed previously that β-thalassemic erythroblasts can eliminate free α-globin by ULK1-mediated autophagy and that this process is stimulated by rapamycin inhibition of mTORC1, which phosphorylates ULK1 to inhibit its activity. Several studies have shown that iron restriction can reduce the accumulation of free α-globin precipitates to alleviate the pathophysiology of β-thalassemia. Considering that iron stimulates mTORC1 activity in numerous cell types including erythroblasts, we tested the hypothesis that iron restriction alleviates β-thalassemia by inhibiting mTORC1, thereby stimulating ULK1-mediated autophagy of free α-globin. Hbb Th3/+ β-thalassemic mice or HbbTh3/+Ulk1-/- mice were treated with the clinical stage oral ferroportin inhibitor vamifeport (known also as VIT-2763) for 45 days to cause systemic iron restriction. In HbbTh3/+ mice, vamifeport administration led to 66% and 40% reductions in the levels of serum iron (p<0.001) and ferritin (p=0.001), respectively, as expected. Iron restriction by vamifeport alleviated the pathophysiology of β-thalassemia compared to vehicle-treatment in HbbTh3/+, as evidenced by a 21% increase in RBC count (p<0.001), 32% reduction in insoluble α-globin in red blood cells (RBC) (p=0.002), 41% reduction in reticulocyte count (p<0.001), 27% reduction in spleen mass (p=0.034) and enhanced maturation of spleen and bone marrow erythroid precursors, indicating reduced ineffective erythropoiesis. Multivariate analysis showed that beneficial effects of iron restriction in β-thalassemic mice were attenuated by concomitant disruption of both Ulk1 alleles. For example, vamifeport treatment of HbbTh3/+Ulk1-/- mice caused only a 12% increase in RBC counts (p=0.015 compared to HbbTh3/+). Additionally, iron restriction improved erythroid maturation in HbbTh3/+Ulk1-/- mice, but to a significantly lesser extent than in thalassemic mice with intact Ulk1alleles. We obtained similar results by inducing iron deprivation with PR73, a peptide hepcidin mimetic. Mechanistically, long-term administration of vamifeport was associated with inhibition of mTORC1, as evidenced by 32% reductions in the phosphorylation of its substrate, ribosomal protein S6 kinase (p=0.004), and activation of the heme-regulated eIF2α kinase (HRI), indicated by increased phosphorylation of eIF2α and/or accumulation of the HRI effector transcription factor ATF4. Similar results were obtained with PR73. Administration of a single dose of PR73 to HbbTh3/+ mice led to activation of HRI in Ter119 + erythroblasts after 8 hours, which preceded the downregulation of mTORC1 activity, detected at 24 hours. This is consistent with prior studies showing that HRI inhibits mTORC1. Loss of ULK1 had no effect on suppression of mTORC1 with either drug, consistent with ULK1 being the substrate of mTORC1; we are currently investigating whether loss of ULK1 alters the HRI pathway. Together, our data support a mechanism through which iron restriction alleviates the pathophysiology of β-thalassemia in part by stimulating ULK1-mediated autophagy of free α-globin. This process is likely mediated by iron restriction that activates HRI which in turn inhibits mTORC1 to block its negative effects on ULK1. Additional mechanisms for iron regulation of mTORC1 activity are also possible. Our findings provide new insight into the mechanisms by which iron restriction alleviates β-thalassemia and illustrate how metabolic regulators of erythropoiesis impact the severity of β-thalassemia by eliminating free α-globin through a key protein quality control pathway.

Epithelial Yap/Taz are required for functional alveolar regeneration following acute lung injury.

A hallmark of idiopathic pulmonary fibrosis (IPF) and other interstitial lung diseases is dysregulated repair of the alveolar epithelium. The Hippo pathway effector transcription factors YAP and TAZ are implicated as essential for type 1 and type 2 alveolar epithelial cell (AT1 and AT2) differentiation in the developing lung, yet aberrant activation of YAP/TAZ is a prominent feature of the dysregulated alveolar epithelium in IPF. In these studies, we sought to define the functional role of YAP/TAZ activity during alveolar regeneration. We demonstrated that Yap and Taz were normally activated in AT2 cells shortly after injury, and deletion of Yap/Taz in AT2 cells led to pathologic alveolar remodeling, failure of AT2-to-AT1 cell differentiation, increased collagen deposition, exaggerated neutrophilic inflammation, and increased mortality following injury induced by a single dose of bleomycin. Loss of Yap/Taz activity prior to an LPS injury prevented AT1 cell regeneration, led to intraalveolar collagen deposition, and resulted in persistent innate inflammation. These findings establish that AT2 cell Yap/Taz activity is essential for functional alveolar epithelial repair and prevention of fibrotic remodeling.

Pregnancy-associated Steroid Effects on Insulin Sensitivity, Adipogenesis, and Lipogenesis: Role of Wnt/β-Catenin Pathway.

The shift in maternal energy metabolism characteristic of pregnancy is thought to be driven by various hormonal changes, especially of ovarian and placental steroids. Imbalances in circulating estradiol (E2) and progesterone (P4) levels during this period are often associated with metabolic disturbances leading to the development of gestational diabetes mellitus (GDM). Since abnormalities in the Wnt pathway effector transcription factor 7-like 2 (TCF7L2) are commonly associated with the occurrence of GDM, we hypothesized that the canonical or β-catenin-dependent Wnt signaling pathway mediates the metabolic actions of E2 and P4. Our study was aimed at elucidating the metabolic function of the steroids E2 and P4, and examining the role of the canonical Wnt signaling pathway in mediating the actions of these steroids. The ovariectomized (OVX) rat was used as a model system to study the effect of known concentrations of exogenously administered E2 and P4. Niclosamide (Nic) was administered to block Wnt signaling. 3T3-L1 cells were used to analyze changes in differentiation in the presence of the steroids or niclosamide. In the present study, we observed that E2 enhanced insulin sensitivity and inhibited lipogenesis while P4 increased lipogenic gene expression-in 3T3-L1 adipocytes, and in adipose tissue and skeletal muscle of OVX rats when the dosage of E2 and P4 mimicked that of pregnancy. Both E2 and P4 were also found to upregulate Wnt signaling. Nic nhibited the steroid-mediated increase in Wnt signaling in adipocytes and OVX rats. The insulin-sensitizing and antilipogenic actions of E2 were found to be mediated by the canonical Wnt pathway, but the effects of P4 on lipogenesis appeared to be independent of it. Additionally, it was observed that inhibition of Wnt signaling by Nic hastened adipogenic differentiation, and the inhibitory effect of E2 on differentiation was prevented by Nic. The findings presented in this study highlight the role of steroids and Wnt pathway in glucose and lipid metabolism and are relevant to understanding the pathophysiology of metabolic disorders arising from hormonal disturbances.

BMP4 triggers regulatory circuits specifying the cardiac mesoderm lineage.

Cardiac lineage specification in the mouse is controlled by TGFβ and WNT signaling. From fly to fish, BMP has been identified as an indispensable heart inducer. A detailed analysis of the role of Bmp4 and its effectors Smad1/5, however, was still missing. We show that Bmp4 induces cardiac mesoderm formation in murine embryonic stem cells in vitro. Bmp4 first activates Wnt3 and upregulates Nodal. pSmad1/5 and the WNT effector Tcf3 form a complex, and together with pSmad2/3 activate mesoderm enhancers and Eomes. They then cooperate with Eomes to consolidate the expression of many mesoderm factors, including T. Eomes and T form a positive- feedback loop and open additional enhancers regulating early mesoderm genes, including the transcription factor Mesp1, establishing the cardiac mesoderm lineage. In parallel, the neural fate is suppressed. Our data confirm the pivotal role of Bmp4 in cardiac mesoderm formation in the mouse. We describe in detail the consecutive and cooperative actions of three signaling pathways, BMP, WNT and Nodal, and their effector transcription factors, during cardiac mesoderm specification.

Distinct transcriptomic and epigenomic modalities underpin human memory T cell subsets and their activation potential

Human memory T cells (MTC) are poised to rapidly respond to antigen re-exposure. Here, we derived the transcriptional and epigenetic programs of resting and ex vivo activated, circulating CD4+ and CD8+ MTC subsets. A progressive gradient of gene expression from naïve to TCM to TEM is observed, which is accompanied by corresponding changes in chromatin accessibility. Transcriptional changes suggest adaptations of metabolism that are reflected in altered metabolic capacity. Other differences involve regulatory modalities comprised of discrete accessible chromatin patterns, transcription factor binding motif enrichment, and evidence of epigenetic priming. Basic-helix-loop-helix factor motifs for AHR and HIF1A distinguish subsets and predict transcription networks to sense environmental changes. Following stimulation, primed accessible chromatin correlate with an augmentation of MTC gene expression as well as effector transcription factor gene expression. These results identify coordinated epigenetic remodeling, metabolic, and transcriptional changes that enable MTC subsets to ultimately respond to antigen re-encounters more efficiently.

Tcf7l2 in hepatocytes regulates de novo lipogenesis in diet-induced non-alcoholic fatty liver disease in mice

Aims/hypothesisNon-alcoholic fatty liver disease (NAFLD) associated with type 2 diabetes may more easily progress towards severe forms of non-alcoholic steatohepatitis (NASH) and cirrhosis. Although the Wnt effector transcription factor 7-like 2 (TCF7L2) is closely associated with type 2 diabetes risk, the role of TCF7L2 in NAFLD development remains unclear. Here, we investigated how changes in TCF7L2 expression in the liver affects hepatic lipid metabolism based on the major risk factors of NAFLD development.MethodsTcf7l2 was selectively ablated in the liver of C57BL/6N mice by inducing the albumin (Alb) promoter to recombine Tcf7l2 alleles floxed at exon 5 (liver-specific Tcf7l2-knockout [KO] mice: Alb-Cre;Tcf7l2f/f). Alb-Cre;Tcf7l2f/f and their wild-type (Tcf7l2f/f) littermates were fed a high-fat diet (HFD) or a high-carbohydrate diet (HCD) for 22 weeks to reproduce NAFLD/NASH. Mice were refed a standard chow diet or an HCD to stimulate de novo lipogenesis (DNL) or fed an HFD to provide exogenous fatty acids. We analysed glucose and insulin sensitivity, metabolic respiration, mRNA expression profiles, hepatic triglyceride (TG), hepatic DNL, selected hepatic metabolites, selected plasma metabolites and liver histology.ResultsAlb-Cre;Tcf7l2f/f essentially exhibited increased lipogenic genes, but there were no changes in hepatic lipid content in mice fed a normal chow diet. However, following 22 weeks of diet-induced NAFLD/NASH conditions, liver steatosis was exacerbated owing to preferential metabolism of carbohydrate over fat. Indeed, hepatic Tcf7l2 deficiency enhanced liver lipid content in a manner that was dependent on the duration and amount of exposure to carbohydrates, owing to cell-autonomous increases in hepatic DNL. Mechanistically, TCF7L2 regulated the transcriptional activity of Mlxipl (also known as ChREBP) by modulating O-GlcNAcylation and protein content of carbohydrate response element binding protein (ChREBP), and targeted Srebf1 (also called SREBP1) via miRNA (miR)-33-5p in hepatocytes. Eventually, restoring TCF7L2 expression at the physiological level in the liver of Alb-Cre;Tcf7l2f/f mice alleviated liver steatosis without altering body composition under both acute and chronic HCD conditions.Conclusions/interpretationIn mice, loss of hepatic Tcf7l2 contributes to liver steatosis by inducing preferential metabolism of carbohydrates via DNL activation. Therefore, TCF7L2 could be a promising regulator of the NAFLD associated with high-carbohydrate diets and diabetes since TCF7L2 deficiency may lead to development of NAFLD by promoting utilisation of excess glucose pools through activating DNL.Data availabilityRNA-sequencing data have been deposited into the NCBI GEO under the accession number GSE162449 (www.ncbi.nlm.nih.gov/geo/query/acc.cgi?acc=GSE162449).Graphical abstract

SARS-CoV-2 Diverges from Other Betacoronaviruses in Only Partially Activating the IRE1α/XBP1 Endoplasmic Reticulum Stress Pathway in Human Lung-Derived Cells.

ABSTRACTSevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has killed over 6 million individuals worldwide and continues to spread in countries where vaccines are not yet widely available or its citizens are hesitant to become vaccinated. Therefore, it is critical to unravel the molecular mechanisms that allow SARS-CoV-2 and other coronaviruses to infect and overtake the host machinery of human cells. Coronavirus replication triggers endoplasmic reticulum (ER) stress and activation of the unfolded protein response (UPR), a key host cell pathway widely believed to be essential for viral replication. We examined the master UPR sensor IRE1α kinase/RNase and its downstream transcription factor effector XBP1s, which is processed through an IRE1α-mediated mRNA splicing event, in human lung-derived cells infected with betacoronaviruses. We found that human respiratory coronavirus OC43 (HCoV-OC43), Middle East respiratory syndrome coronavirus (MERS-CoV), and murine coronavirus (MHV) all induce ER stress and strongly trigger the kinase and RNase activities of IRE1α as well as XBP1 splicing. In contrast, SARS-CoV-2 only partially activates IRE1α through autophosphorylation, but its RNase activity fails to splice XBP1. Moreover, while IRE1α was dispensable for replication in human cells for all coronaviruses tested, it was required for maximal expression of genes associated with several key cellular functions, including the interferon signaling pathway, during SARS-CoV-2 infection. Our data suggest that SARS-CoV-2 actively inhibits the RNase of autophosphorylated IRE1α, perhaps as a strategy to eliminate detection by the host immune system.

The Role of GCN2 Kinase in Mediating the Effects of Amino Acids on Longevity and Feeding Behaviour in Drosophila.

Restriction of amino acids in the diet can extend lifespan in diverse species ranging from flies to mammals. However, the role of individual amino acids and the underlying molecular mechanisms are only partially understood. The evolutionarily conserved serine/threonine kinase General Control Nonderepressible 2 (GCN2) is a key sensor of amino acid deficiency and has been implicated in the response of lifespan to dietary restriction (DR). Here, we generated a novel Drosophila GCN2 null mutant and analyzed its response to individual amino acid deficiency. We show that GCN2 function is essential for fly development, longevity and feeding behaviour under long-term, but not short-term, deprivation of all individual essential amino acids (EAAs) except for methionine. GCN2 mutants were longer-lived than control flies and showed normal feeding behaviour under methionine restriction. Thus, in flies at least two systems regulate these responses to amino acid deprivation. Methionine deprivation acts via a GCN2-independent mechanism, while all other EAA are sensed by GCN2. Combined deficiency of methionine and a second EAA blocked the response of GCN2 mutants to methionine, suggesting that these two pathways are interconnected. Wild type flies showed a short-term rejection of food lacking individual EAA, followed by a long-term compensatory increase in food uptake. GCN2 mutants also showed a short-term rejection of food deprived of individual EAA, but were unable to mount the compensatory long-term increase in food uptake. Over-expression of the downstream transcription factor ATF4 partially rescued the response of feeding behaviour in GCN2 mutants to amino acid deficiency. Phenotypes of GCN2 mutants induced by leucine and tryptophan, but not isoleucine, deficiency were partially rescued by ATF4 over-expression. The exact function of GCN2 as an amino acid sensor in vivo and the downstream action of its transcription factor effector ATF4 are thus context-specific with respect to the EAA involved.

Dysregulation of Wnt signaling in bone of type 2 diabetes mellitus and diabetic Charcot arthropathy

BackgroundType 2 diabetes mellitus (T2DM) patients show a markedly higher fracture risk and impaired fracture healing when compared to non-diabetic patients. However in contrast to type 1 diabetes mellitus, bone mineral density in T2DM is known to be normal or even regionally elevated, also known as diabetic bone disease. Charcot arthropathy is a severe and challenging complication leading to bone destruction and mutilating bone deformities. Wnt signaling is involved in increasing bone mineral density, bone homeostasis and apoptotic processes. It has been shown that type 2 diabetes mellitus is strongly associated with gene variants of the Wnt signaling pathway, specifically polymorphisms of TCF7L2 (transcription factor 7 like 2), which is an effector transcription factor of this pathway.MethodsBone samples of 19 T2DM patients and 7 T2DM patients with additional Charcot arthropathy were compared to 19 non-diabetic controls. qPCR analysis for selected members of the Wnt-signaling pathway (WNT3A, WNT5A, catenin beta, TCF7L2) and bone gamma-carboxyglutamate (BGLAP, Osteocalcin) was performed and analyzed using the 2-ΔΔCt- Method. Statistical analysis comprised one-way analysis of variance (ANOVA).ResultsIn T2DM patients who had developed Charcot arthropathy WNT3A and WNT5A gene expression was down-regulated by 89 and 58% compared to healthy controls (p < 0.0001). TCF7L2 gene expression showed a significant reduction by 63% (p < 0.0001) and 18% (p = 0.0136) in diabetic Charcot arthropathy. In all diabetic patients BGLAP (Osteocalcin) was significantly decreased by at least 59% (p = 0.0019).ConclusionsFor the first time with this study downregulation of members of the Wnt-signaling pathway has been shown in the bone of diabetic patients with and without Charcot arthropathy. This may serve as future therapeutic target for this severe disease.

Ependymoma associated protein Zfta is expressed in immature ependymal cells but is not essential for ependymal development in mice

The fusion protein of uncharacterised zinc finger translocation associated (ZFTA) and effector transcription factor of tumorigenic NF-κB signalling, RELA (ZFTA-RELA), is expressed in more than two-thirds of supratentorial ependymoma (ST-EPN-RELA), but ZFTA’s expression profile and functional analysis in multiciliated ependymal (E1) cells have not been examined. Here, we showed the mRNA expression of mouse Zfta peaks on embryonic day (E) 17.5 in the wholemount of the lateral walls of the lateral ventricle. Zfta was expressed in the nuclei of FoxJ1-positive immature E1 (pre-E1) cells in E18.5 mouse embryonic brain. Interestingly, the transcription factors promoting ciliogenesis (ciliary TFs) (e.g., multicilin) and ZFTA-RELA upregulated luciferase activity using a 5′ upstream sequence of ZFTA in cultured cells. Zftatm1/tm1 knock-in mice did not show developmental defects or abnormal fertility. In the Zftatm1/tm1 E1 cells, morphology, gene expression, ciliary beating frequency and ependymal flow were unaffected. These results suggest that Zfta is expressed in pre-E1 cells, possibly under the control of ciliary TFs, but is not essential for ependymal development or flow. This study sheds light on the mechanism of the ZFTA-RELA expression in the pathogenesis of ST-EPN-RELA: Ciliary TFs initiate ZFTA-RELA expression in pre-E1 cells, and ZFTA-RELA enhances its own expression using positive feedback.

Epi-Aszonalenin B from Aspergillus novofumigatus inhibits NF-κB activity induced by ZFTA-RELA fusion protein that drives ependymoma

Nuclear factor-kappa B (NF-κB) signaling is an intracellular signaling pathway involved in inflammatory responses and the pathogenesis of various cancers, including ependymoma, which is a rare and chemotherapy-resistant glioma. Several isoforms of fusion proteins that consist of a nuclear protein, zinc finger translocation associated (ZFTA), and RELA (ZFTA-RELA), an NF-κB-signaling effector transcription factor, cause excessive activation of the NF-κB signaling pathway and result in supratentorial ependymomas (ST-EPN-RELA). As inhibitors of NF-κB activity induced by ZFTA-RELA are expected to be therapeutic agents for ST-EPN-RELA, we established an NF-κB responsive luciferase reporter cell line that expresses the most common isoform of ZFTA-RELA in a doxycycline-dependent manner. Using this reporter cell line, we screened fungus extracts for compounds that inhibit the NF-κB activity induced by ZFTA-RELA expression and identified aszonalenin, an alkaloid from Aspergillus novofumigatus. We also purified analogs of aszonalenin, namely acetylaszonalenin and epi-aszonalenin B and C. In a luciferase assay using cells constitutively expressing luciferase (counter assay), acetylaszonalenin and epi-aszonalenin C showed non-specific inhibition of the luciferase activity. Aszonalenin and epi-aszonalenin B inhibited the NF-κB responsive luciferase activity by expressing ZFTA-RELA more strongly than the luciferase activity in the counter assay. The upregulation of endogenous NF-κB responsive genes, such as CCND1, ICAM1, and L1CAM, by ZFTA-RELA expression was inhibited by epi-aszonalenin B, but not by aszonalenin. This study suggests that epi-aszonalenin B may be a lead compound for the therapeutic development of ST-EPN-RELA.

Epithelial-Mesenchymal Transition Signaling and Prostate Cancer Stem Cells: Emerging Biomarkers and Opportunities for Precision Therapeutics.

Prostate cancers may reactivate a latent embryonic program called the epithelial–mesenchymal transition (EMT) during the development of metastatic disease. Through EMT, tumors can develop a mesenchymal phenotype similar to cancer stem cell traits that contributes to metastasis and variation in therapeutic responses. Some of the recurrent somatic mutations of prostate cancer affect EMT driver genes and effector transcription factors that induce the chromatin- and androgen-dependent epigenetic alterations that characterize castrate-resistant prostate cancer (CRPC). EMT regulators in prostate cancer comprise transcription factors (SNAI1/2, ZEB1, TWIST1, and ETS), tumor suppressor genes (RB1, PTEN, and TP53), and post-transcriptional regulators (miRNAs) that under the selective pressures of antiandrogen therapy can develop an androgen-independent metastatic phenotype. In prostate cancer mouse models of EMT, Slug expression, as well as WNT/β-Catenin and notch signaling pathways, have been shown to increase stemness potential. Recent single-cell transcriptomic studies also suggest that the stemness phenotype of advanced prostate cancer may be related to EMT. Other evidence correlates EMT and stemness with immune evasion, for example, activation of the polycomb repressor complex I, promoting EMT and stemness and cytokine secretion through RB1, TP53, and PRC1. These findings are helping clinical trials in CRPC that seek to understand how drugs and biomarkers related to the acquisition of EMT can improve drug response.

Fibrous Caps in Atherosclerosis Form by Notch-Dependent Mechanisms Common to Arterial Media Development.

Atheromatous fibrous caps are produced by smooth muscle cells (SMCs) that are recruited to the subendothelial space. We tested whether the recruitment mechanisms are the same as in embryonic artery development, which relies prominently on Notch signaling to form the subendothelial medial SMC layers. Notch elements were expressed in regions of fibrous cap in human and mouse plaques. To assess the causal role of Notch signaling in cap formation, we studied atherosclerosis in mice where the Notch pathway was inactivated in SMCs by conditional knockout of the essential effector transcription factor RBPJ (recombination signal-binding protein for immunoglobulin kappa J region). The recruitment of cap SMCs was significantly reduced without major effects on plaque size. Lineage tracing revealed the accumulation of SMC-derived plaque cells in the cap region was unaltered but that Notch-defective cells failed to re-acquire the SMC phenotype in the cap. Conversely, to analyze whether the loss of Notch signaling is required for SMC-derived cells to accumulate in atherogenesis, we studied atherosclerosis in mice with constitutive activation of Notch signaling in SMCs achieved by conditional expression of the Notch intracellular domain. Forced Notch signaling inhibited the ability of medial SMCs to contribute to plaque cells, including both cap SMCs and osteochondrogenic cells, and significantly reduced atherosclerosis development. Sequential loss and gain of Notch signaling is needed to build the cap SMC population. The shared mechanisms with embryonic arterial media assembly suggest that the cap forms as a neo-media that restores the connection between endothelium and subendothelial SMCs, transiently disrupted in early atherogenesis.

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.

Loss of the Transfer RNA Wobble Uridine-Modifying Enzyme Elp3 Delays T Cell Cycle Entry and Impairs T Follicular Helper Cell Responses through Deregulation of Atf4.

The activation of T cells is accompanied by intensive posttranscriptional remodeling of their proteome. We observed that protein expression of enzymes that modify wobble uridine in specific tRNAs, namely elongator subunit 3 (Elp3) and cytosolic thiouridylase (Ctu)2, increased in the course of T cell activation. To investigate the role of these tRNA epitranscriptomic modifiers in T cell biology, we generated mice deficient for Elp3 in T cells. We show that deletion of Elp3 has discrete effects on T cells. In vitro, Elp3-deficient naive CD4+ T cells polarize normally but are delayed in entering the first cell cycle following activation. In vivo, different models of immunization revealed that Elp3-deficient T cells display reduced expansion, resulting in functional impairment of T follicular helper (TFH) responses, but not of other CD4+ effector T cell responses. Transcriptomic analyses identified a progressive overactivation of the stress-responsive transcription factor Atf4 in Elp3-deficient T cells. Overexpression of Atf4 in wild-type T cells phenocopies the effect of Elp3 loss on T cell cycle entry and TFH cell responses. Reciprocally, partial silencing of Atf4 or deletion of its downstream effector transcription factor Chop rescues TFH responses of Elp3-deficient T cells. Together, our results reveal that specific epitranscriptomic tRNA modifications contribute to T cell cycle entry and promote optimal TFH responses.

The Wnt Effector TCF7l2 Promotes Oligodendroglial Differentiation by Repressing Autocrine BMP4-Mediated Signaling.

Promoting oligodendrocyte (OL) differentiation represents a promising option for remyelination therapy for treating the demyelinating disease multiple sclerosis (MS). The Wnt effector transcription factor 7-like 2 (TCF7l2) was upregulated in MS lesions and had been proposed to inhibit OL differentiation. Recent data suggest the opposite yet underlying mechanisms remain elusive. Here, we unravel a previously unappreciated function of TCF7l2 in controlling autocrine bone morphogenetic protein (BMP)4-mediated signaling. Disrupting TCF7l2 in mice of both sexes results in oligodendroglial-specific BMP4 upregulation and canonical BMP4 signaling activation in vivo Mechanistically, TCF7l2 binds to Bmp4 gene regulatory element and directly represses its transcriptional activity. Functionally, enforced TCF7l2 expression promotes OL differentiation by reducing autocrine BMP4 secretion and dampening BMP4 signaling. Importantly, compound genetic disruption demonstrates that oligodendroglial-specific BMP4 deletion rescues arrested OL differentiation elicited by TCF7l2 disruption in vivo Collectively, our study reveals a novel connection between TCF7l2 and BMP4 in oligodendroglial lineage and provides new insights into augmenting TCF7l2 for promoting remyelination in demyelinating disorders such as MS.SIGNIFICANCE STATEMENT Incomplete or failed myelin repairs, primarily resulting from the arrested differentiation of myelin-forming oligodendrocytes (OLs) from oligodendroglial progenitor cells, is one of the major reasons for neurologic progression in people affected by multiple sclerosis (MS). Using in vitro culture systems and in vivo animal models, this study unraveled a previously unrecognized autocrine regulation of bone morphogenetic protein (BMP)4-mediated signaling by the Wnt effector transcription factor 7-like 2 (TCF7l2). We showed for the first time that TCF7l2 promotes oligodendroglial differentiation by repressing BMP4-mediated activity, which is dysregulated in MS lesions. Our study suggests that elevating TCF7l2 expression may be possible in overcoming arrested oligodendroglial differentiation as observed in MS patients.