Genetic polymorphisms in genes involved in the type I interferon system (STAT4 and IRF5): association with Asian SLE patients.

Systemic lupus erythematosus (SLE) is a common autoimmune disease with a polymorphic clinical presentation involving multisystem damages with significant differences in prevalence and disease severity among different ethnic groups. Although genetic, hormonal, and environmental factors have been demonstrated to contribute a lot to SLE, the pathogenesis of SLE is still unknown. Numerous evidence revealed that gene variants within the type I interferons (IFN) signaling pathway performed the great genetic associations with autoimmune diseases including SLE. To date, through genome-wide association studies (GWAS), genetic association studies showed that more than 100 susceptibility genes have been linked to the pathogenesis of SLE, among which TYK2, STAT1, STAT4, and IRF5 are important molecules directly connected to the type I interferon signaling system. The review summarized the genetic associations and the detailed risk loci of STAT4 and IRF5 with Asian SLE patients, explored the genotype distributions associated with the main clinical manifestations of SLE, and sorted out the potential reasons for the differences in susceptibility in Asia and Europe. Moreover, the therapies targeting STAT4 and IRF5 were also evaluated in order to propose more personalized and targeted treatment plans in SLE.

IL-12 drives the differentiation of human T follicular regulatory cells.

T follicular regulatory (Tfr) cells can counteract the B cell helper activity of T follicular helper (Tfh) cells and hinder the production of antibodies against self-antigens or allergens. A mechanistic understanding of the cytokines initiating the differentiation of human regulatory T (Treg) cells into Tfr cells is still missing. Herein, we report that low doses of the pro-Tfh cytokine interleukin-12 (IL-12) drive the induction of a Tfr cell program on activated human Treg cells while also preserving their regulatory function. Mechanistically, we found that IL-12 led to STAT4 (signal transducer and activator of transcription 4) phosphorylation and binding to IL-12-driven follicular signature genes. Patients with inborn errors of immunity in the IL12RB1 gene presented with a strong decrease in circulating Tfr cells and produced higher levels of anti-actin autoantibodies in vivo. Overall, this study unveils IL-12 as an inducer of Tfr cell differentiation in vivo and provides an approach for the in vitro generation of human Tfr-like cells.

The JAK-STAT signaling-related signature serves as a prognostic and predictive biomarker for renal cell carcinoma immunotherapy.

Renal cell carcinoma (RCC) represents a significant portion of genitourinary cancers, marked by challenging prognosis and high metastasis rates. Immunotherapy has been applied in managing advanced renal cell carcinoma, but the therapeutic outcomes are unsatisfactory. In this study, we order to construct a Janus kinase/signal transduction and activator transcriptional (JAK/STAT)-related signature linked to kidney patient outcomes for better predicting the efficacy to immune checkpoint inhibitors (ICIs) and to provide guidance for effective combination therapy. We screened 25 differentially expressed genes (DEGs) that exhibited high expression in RCC samples and were enriched in the JAK-STAT signaling pathway. Among these genes, 11 key genes were identified and correlated with the expectation of Kidney Clear Cell Carcinoma (KIRC) patients and all these genes was significantly elevated in RCC tumor tissues and cancer cells compared to para-cancer tissues and normal renal cells. Utilizing these 11 genes, we divided RCC patients into high-risk and low-risk groups. We found a clear correlation between the clinicopathologic factors of KIRC patients and the JAK-STAT-related risk score. And the IHC results shown that the JAK3 and STAT4 expression of tumor was significantly higher than normal tissue in RCC patients, the level of JAK3 and STAT4 was positively related to the T stage of RCC patients. In addition, high-risk patients had a poorer prognosis and greater protumor immune cell infiltration, and benefitted less from immunotherapy than did low-risk patients. Furthermore, the JAK-STAT-related risk score can predict disease-free survival (DFS) in RCC patients according to the nomogram, which constructed in combination with other clinical features such as age, TNM-staging and stage. Our study demonstrated the JAK-STAT signaling pathway's important regulatory function in RCC tumor immunity. This insight not only enhances our ability to accurately predict the survival rate of RCC patients, but also underscores a potential therapeutic alternative for RCC, involving the combined targeting of the JAK-STAT pathway and immune checkpoints.

The Role of JAK-STAT-SOCS1 Axis in Tumorigenesis, Malignant Progression and Lymphatic Metastasis of Penile Cancer.

Background: To uncover the potential significance of JAK-STAT-SOCS1 axis in penile cancer, our study was the pioneer in exploring the altered expression processes of JAK-STAT-SOCS1 axis in tumorigenesis, malignant progression and lymphatic metastasis of penile cancer. Methods: In current study, the comprehensive analysis of JAK-STAT-SOCS1 axis in penile cancer was analyzed via multiple analysis approaches based on GSE196978 data, single-cell data (6 cancer samples) and bulk RNA data (7 cancer samples and 7 metastasis lymph nodes). Results: Our study observed an altered molecular expression of JAK-STAT-SOCS1 axis during three different stages of penile cancer, from tumorigenesis to malignant progression to lymphatic metastasis. STAT4 was an important dominant molecule in penile cancer, which mediated the immunosuppressive tumor microenvironment by driving the apoptosis of cytotoxic T cell and was also a valuable biomarker of immune checkpoint inhibitor treatment response. Conclusions: Our findings revealed that the complexity of JAK-STAT-SOCS1 axis and the predominant role of STAT4 in penile cancer, which can mediate tumorigenesis, malignant progression, and lymphatic metastasis. This insight provided valuable information for developing precise treatment strategies for patients with penile cancer.

Follicular fluid meiosis-activating sterol prevents porcine ovarian granulosa cells from hypoxia-induced apoptosis via inhibiting STAT4 expression.

Follicular fluid meiosis-activating sterol (FF-MAS) is a small molecule compound found in FF, named for its ability to induce oocyte resumption of meiosis. Granulosa cells (GCs) within the follicle are typically located in a hypoxic environment under physiologic conditions due to limited vascular distribution. Previous research suggests that hypoxia-induced cell cycle arrest and apoptosis in GCs may be crucial triggering factors in porcine follicular atresia. However, the impact of FF-MAS on GCs within follicles has not been explored so far. In this study, we uncovered a novel role of FF-MAS in facilitating GC survival under hypoxic conditions by inhibiting STAT4 expression. We found that STAT4 expression was upregulated in porcine GCs exposed to 1% O2. Both gain and loss of function assays confirmed that STAT4 was required for cell apoptosis under hypoxia conditions, and that the GC apoptosis caused by hypoxia was markedly attenuated following FF-MAS treatment through inhibition of STAT4 expression. Correlation analysis in vivo revealed that GC apoptosis was associated with increased STAT4 expression, while the FF-MAS content in follicular fluid was negatively correlated with STAT4 mRNA levels and cell apoptosis. These findings elucidate a novel role of FF-MAS-mediated protection of GCs by inhibiting STAT4 expression under hypoxia, which might contribute to the mechanistic understanding of follicular development.

Granulosa cells (GCs) influence follicle growth and development, with their proliferation and differentiation promoting follicle development and ovulation, while their programmed cell death and degeneration trigger follicular atresia. In this study, to investigate the effect of FF-MAS on GCs of follicles, we performed gene expression profiling in the domestic pig (Sus scrofa). We discovered STAT4 is required for GC apoptosis under hypoxia conditions both in vitro and in vivo and FF-MAS prevents porcine ovarian granulosa cells from hypoxia-induced apoptosis via inhibiting STAT4 expression.

Downregulated GPX4 in salivary gland epithelial cells contributes to salivary secretion dysfunction in Sjogren's syndrome via lipid ROS/pSTAT4/AQP5 axis.

Sjogren's syndrome (SS) is an autoimmune disease characterized by dysfunction of exocrine glands, such as salivary glands. However, the molecular mechanism of salivary secretion dysfunction in SS is still unclear. Given the significance of glutathione peroxidase 4 (GPX4) in cellular redox homeostasis, we hypothesized that dysregulation of GPX4 may play a pivotal role in the pathogenesis of salivary secretion dysfunction observed in SS. The salivary gland of SS patients and the SS mouse model exhibited reduced expression of the ferroptosis inhibitor GPX4 and the important protein aquaporin 5 (AQP5), which is involved in salivary secretion. GPX4 overexpression upregulated and GPX4 knockdown downregulated AQP5 expression in salivary gland epithelial cells (SGECs) and salivary secretion. Bioinformatics analysis of GSE databases from SS patients' salivary glands revealed STAT4 as a key intermediary regulator between GPX4 and AQP5. A higher level of nuclear pSTAT4 was observed in the salivary gland of the SS mouse model. GPX4 overexpression inhibited and GPX4 knockdown promoted STAT4 phosphorylation and nuclear translocation in SGECs. CHIP assay confirmed the binding of pSTAT4 within the promoter of AQP5 inhibiting AQP5 transcription. GPX4 downregulation accumulates intracellular lipid ROS in SGECs. Lipid ROS inhibitor ferrostatin-1 treatment during in vitro and in vivo studies confirmed that lipid ROS activates STAT4 phosphorylation and nuclear translocation in SGECs. In summary, the downregulated GPX4 in SGECs contributes to salivary secretion dysfunction in SS via the lipid ROS/pSTAT4/AQP5 axis. This study unraveled novel targets to revitalize the salivary secretion function in SS patients.

Association between STAT4 gene polymorphism and susceptibility to pulmonary tuberculosis in the Moldavian population.

Signal transducer and activator of transcription 4 (STAT4) plays a crucial role in the host immune response against Mycobacterium tuberculosis. This study investigates the association between STAT4 gene polymorphisms and pulmonary tuberculosis (TB) risk in the Moldavian population. A total of 272 TB patients and 251 community-matched controls underwent screening for functional single-nucleotide polymorphisms (SNPs) rs897200 and rs7574865 in the STAT4 gene. The minor T allele and the TT/CT genotype of rs897200 demonstrated a significant association with reduced pulmonary TB risk (allelic model: adjusted OR = .74, p = .025; log-additive model: adjusted OR = .72, p = .02; and dominant model: adjusted OR = .65, p = .023), indicating a protective effect. Similar associations, characterized by an even more pronounced reduction in risk, were observed among females and late-onset TB patients (>44 years). No significant associations were found for rs7574865. In addition, a combined genotype analysis incorporating 43 SNPs from our previous studies revealed potential associations, such as STAT4 rs897200 CT with IFNG rs2430561 AA (adjusted OR = .36, p = .0025) and STAT4 rs897200 CT with TNFA rs1800629 GA (adjusted OR = .33, p = .0012). This study emphasizes the significant association of STAT4 rs897200 with pulmonary TB risk in the Moldavian population, underscoring its role in the disease development.

Signal Transducer and Activator of Transcription 4-Induced Up-Regulated LINC01278 Enhances Proliferation and Invasion of Non-Small Cell Lung Cancer Cells via the MicroRNA-877-5p/Activating Transcription Factor 4 Axis.

BACKGROUND: The purpose of this study was to investigate the specific effects of signal transducer and activator of transcription 4 (STAT4)-induced long intergenic nonprotein coding RNA 1278 (LINC01278) on the growth of non-small cell lung cancer (NSCLC) cells involved in the microRNA (miR)-877-5p/activated transcription factor 4 (ATF4) axis. METHODS: NSCLC tumor tissue and adjacent normal tissue were collected. Human normal lung epithelial cell BEAS-2B and human NSCLC cell lines (H1299, H1975, A549, H2228) were collected. The expression levels of STAT4, LINC01278, miR-877-5p, and ATF4 were detected. A549 cells were screened for subsequent experiments. The proliferation ability of cells was detected by colony formation experiment. Cell apoptosis was tested by flow cytometry. Scratch test and transwell assay were used to detect the migration and invasion ability of cells. Biological function of LINC01278 in NSCLC was confirmed by xenograft experiments. RESULTS: Low expression miR-877-5p and high expression of STAT4, LINC01278 and ATF4 were detected in NSCLC. Silenced LINC01278 in A549 cell depressed cell proliferation, migration and invasion, but facilitated cell apoptosis. LINC01278 was positively correlated with STAT4 and could directly bind to miR-877-5p. Upregulating miR-877-5p suppressed NSCLC cell progression, while downregulating miR-877-5p had the opposite effect. Upregulating miR-877-5p abrogated the effects of silenced LINC01278 on NSCLC cell progression. MiR-877-5p targeted ATF4. ATF4 upregulation could partly restore the carcinogenic effect of LINC01278 in vitro and in vivo. CONCLUSION: Our data supports that STAT4-induced upregulation of LINC01278 promotes NSCLC progression by modulating the miR-877-5p/ATF4 axis, suggesting a novel direction for NSCLC treatment.

Regulation of STAT1 and STAT4 Expression by Growth Factor and Interferon Supplementation in Sjögren's Syndrome Cell Culture Models.

Our goal was to investigate the effects of epidermal growth factor (EGF) and interferons (IFNs) on signal transducer and activator of transcription STAT1 and STAT4 mRNA and active phosphorylated protein expression in Sjögren's syndrome cell culture models. iSGECs (immortalized salivary gland epithelial cells) and A253 cells were treated with EGF, IFN-alpha, -beta, -gamma, or mitogen-activated protein kinase p38 alpha (p38-MAPK) inhibitor for 0-24-48-72 h. STAT1 and STAT4 mRNA expression was quantified by qRT-PCR. Untreated and treated cells were compared using the delta-delta-CT method based on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) normalized relative fold changes. phospho-tyrosine-701-STAT1 and phospho-serine-721-STAT4 were detected by Western blot analysis. STAT4 mRNA expression decreased 48 h after EGF treatment in A253 cells, immortalized salivary gland epithelial cells iSGECs nSS2 (sicca patient origin), and iSGECs pSS1 (anti-SSA negative Sjögren's Syndrome patient origin). EGF and p38-MAPK inhibitor decreased A253 STAT4 mRNA levels. EGF combined with IFN-gamma increased phospho-STAT4 and phospho-STAT1 after 72 h in all cell lines, suggesting additive effects for phospho-STAT4 and a major effect from IFN-gamma for phospho-STAT1. pSS1 and nSS2 cells responded differently to type I and type II interferons, confirming unique functional characteristics between iSGEC cell lines. EGF/Interferon related pathways might be targeted to regulate STAT1 and STAT4 expression in salivary gland epithelial cells. Further investigation is required learn how to better target the Janus kinases/signal transducer and activator of transcription proteins (JAK/STAT) pathway-mediated inflammatory response in Sjögren's syndrome.

STAT4 Gene Variant rs7574865 Is Associated with Rheumatoid Arthritis Activity and Anti-CCP Levels in the Western but Not in the Southern Population of Mexico.

Rheumatoid Arthritis (RA) is a multifactorial autoimmune disease. Currently, several genes play an important role in the development of the disease. The objective was to evaluate the association of the STAT4 rs7574865 and rs897200 gene variants with RA susceptibility, DAS28, RF, and anti-CCP in Western and Southern Mexico populations. Genotyping was performed on 476 samples (cases = 240; controls = 236) using the Taqman® system and qPCR probes. Disease activity was assessed using DAS28 and HAQ DI. CRP, ESR, RF, and anti-CCP were determined for clinical assessment. Our study showed there is a statistically significant association with susceptibility to RA for the rs7574865 variant in the Western population for the GT and TT genotypes. The same genotypes also showed a moderate-to-high activity according to DAS28 and positive anti-CCP compared to the control group. This association was not found in the Southern population. This work confirms the association of the rs7574865 variant with RA, as well as a moderate-to-high activity and positive anti-CCP in the Western population but not in the Southern population. No association of the rs897200 variant was found in any of the studied populations.

Implications of IFNγ SNP rs2069705 in primary Sjögren's syndrome: transcriptional activation and B cell infiltration.

Primary Sjögren's syndrome (pSS) is characterized by its autoimmune nature. This study investigates the role of the IFNγ SNP rs2069705 in modulating the susceptibility to pSS. Differential expression of IFNγ and BAFF was analyzed using the GEO database's mRNA microarray GSE84844. Genotyping of the IFNγ SNP rs2069705 was conducted via the dbSNP website. The JASPAR tool was used for predicting transcription factor bindings. Techniques such as dual-luciferase reporter assays, Chromatin immunoprecipitation, and analysis of a pSS mouse model were applied to study gene and protein interactions. A notable increase in the mutation frequency of IFNγ SNP rs2069705 was observed in MNCs from the exocrine glands of pSS mouse models. Bioinformatics analysis revealed elevated levels of IFNγ and BAFF in pSS samples. The model exhibited an increase in both CD20+ B cells and cells expressing IFNγ and BAFF. Knocking down IFNγ resulted in lowered BAFF expression and less lymphocyte infiltration, with BAFF overexpression reversing this suppression. Activation of the Janus kinase (JAK)/STAT1 pathway was found to enhance transcription in the BAFF promoter region, highlighting IFNγ's involvement in pSS. In addition, rs2069705 was shown to boost IFNγ transcription by promoting interaction between its promoter and STAT4. SNP rs2069705 in the IFNγ gene emerges as a pivotal element in pSS susceptibility, primarily by augmenting IFNγ transcription, activating the JAK/STAT1 pathway, and leading to B-lymphocyte infiltration in the exocrine glands.NEW & NOTEWORTHY The research employed a combination of bioinformatics analysis, genotyping, and experimental models, providing a multifaceted approach to understanding the complex interactions in pSS. We have uncovered that the rs2069705 SNP significantly affects the transcription of IFNγ, leading to altered immune responses and B-lymphocyte activity in pSS.

Identification and validation of STAT4 as a prognostic biomarker in acute myeloid leukemia.

Acute myelogenous leukemia (AML) is a common malignancy and is supposed to have the ability to escape host immune surveillance. The present study aimed to identify key genes in AML that may affect tumor immunity and to provide prognosis biomarkers of AML. The Cancer Genome Atlas (TCGA) dataset was screened for transcription factors (TFs) involved in immunity and influencing survival, combining Gene Expression Omnibus (GEO) data to validate the impact on patient survival. A prognostic signature was established using four transcription factors, and these genes play an important role in the immune system, with higher regulatory T cell (Treg) scores in high-risk patients compared with the low-risk group. Analysis of individual genes showed that STAT4 and Treg are closely related, which may be due to STAT4 transcribing related genes that affect immunity. STAT4 expression was positively correlated with the proportion of abnormal cells and promoted AML recurrence as verified by AML clinical patient samples. In addition, silencing of STAT4 significantly slowed down the proliferation capacity of HL60 cells. In conclusion, these findings suggest that STAT4 may be a potential biomarker for AML prognosis. As a key gene affecting the prognosis of AML patients, STAT4 has the potential to be a candidate diagnostic and prognostic biomarker for AML.

ERG mediates the inhibition of NK cell cytotoxicity through the HLX/STAT4/Perforin signaling pathway, thereby promoting the progression of myocardial infarction.

This study aimed to investigate the role of ERG in the HLX/STAT4/Perforin signaling axis, impacting natural killer (NK) cell cytotoxicity and myocardial infarction (MI) progression. NK cell cytotoxicity was assessed via co-culture and 51Cr release assays. Datasets GSE34198 and GSE97320 identified common differentially expressed genes in MI. NK cell gene expression was analyzed in MI patients and healthy individuals using qRT-PCR and Western blotting. ERG's regulation of HLX and STAT4's regulation of perforin were studied through computational tools (MEM) and ChIP experiments. HLX's influence on STAT4 was explored with the MG132 proteasome inhibitor. Findings were validated in a mouse MI model.ERG, a commonly upregulated gene, was identified in NK cells from MI patients and mice. ERG upregulated HLX, leading to STAT4 proteasomal degradation and reduced Perforin expression. Consequently, NK cell cytotoxicity decreased, promoting MI progression. ERG mediates the HLX/STAT4/Perforin axis to inhibit NK cell cytotoxicity, fostering MI progression. These results provide vital insights into MI's molecular mechanisms.

Divergent roles for STAT4 in shaping differentiation of cytotoxic ILC1 and NK cells during gut inflammation.

Natural killer (NK) cells and type 1 innate lymphoid cells (ILC1) require signal transducer and activator of transcription 4 (STAT4) to elicit rapid effector responses and protect against pathogens. By combining genetic and transcriptomic approaches, we uncovered divergent roles for STAT4 in regulating effector differentiation of these functionally related cell types. Stat4 deletion in Ncr1-expressing cells led to impaired NK cell terminal differentiation as well as to an unexpected increased generation of cytotoxic ILC1 during intestinal inflammation. Mechanistically, Stat4-deficient ILC1 exhibited upregulation of gene modules regulated by STAT5 in vivo and an aberrant effector differentiation upon in vitro stimulation with IL-2, used as a prototypical STAT5 activator. Moreover, STAT4 expression in NCR+ innate lymphocytes restrained gut inflammation in the dextran sulfate sodium-induced colitis model limiting pathogenic production of IL-13 from adaptive CD4+ T cells in the large intestine. Collectively, our data shed light on shared and distinctive mechanisms of STAT4-regulated transcriptional control in NK cells and ILC1 required for intestinal inflammatory responses.

STAT4, a potential predictor of prognosis, promotes CD8 T­cell infiltration in ovarian serous carcinoma by inducing CCL5 secretion.

Ovarian serous carcinoma (OC) is a common cause of mortality among gynecological malignancies. Although tumor­infiltrating CD8 T cells are associated with a favorable prognosis of OC, the underlying mechanisms are not clearly understood. The present study identified the key genes and potential molecular mechanisms associated with CD8 T­cell infiltration in OC. The score of CD8 T cells in The Cancer Genome Atlas dataset (376 samples from patients with OC) was estimated using the quanTIseq and MCP­counter algorithms. Thereafter, a protein­protein interaction network of differentially expressed genes was constructed and the hub genes were identified using cytoHubba in Cytoscape. The results revealed that signal transducer and activator of transcription 4 (STAT4) was strongly correlated with CD8 T­cell infiltration in OC. Furthermore, the prognostic value of STAT4 in OC was verified by Kaplan­Meier curve, and univariate and multivariate analyses. The biological functions of STAT4 were determined by Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway analyses, which revealed that STAT4 is closely related to cytokines in OC. Moreover, Spearman correlation analysis suggested that STAT4 was most positively correlated with CC chemokine ligand 5 (CCL5). CCL5 was revealed to be critical for orchestrating T­cell infiltration in tumors. Moreover, immunohistochemistry and reverse transcription­quantitative PCR showed that STAT4, CCL5 and CD8A (a marker for CD8 T cells) were closely related in OC. Moreover, in vitro analysis revealed that STAT4 knockdown led to a decrease in CCL5 expression and CD8 T­cell migration. Taken together, the present study suggested that STAT4 may regulate CD8 T­cell infiltration in OC tissues by inducing CCL5 secretion. Furthermore, STAT4 may be considered a promising prognostic biomarker for OC.

SNP in PTPN22, PADI4, and STAT4 but Not TRAF1 and CD40 Increase the Risk of Rheumatoid Arthritis in Polish Population.

Single nucleotide polymorphisms in non-HLA genes are involved in the development of rheumatoid arthritis (RA). SNPS in genes: PADI4 (rs2240340), STAT4 (rs7574865), CD40 (rs4810485), PTPN22 (rs2476601), and TRAF1 (rs3761847) have been described as risk factors for the development of autoimmune diseases, including RA. This study aimed to assess the prevalence of polymorphisms of these genes in the Polish population of patients with rheumatoid arthritis as compared to healthy controls. 324 subjects were included in the study: 153 healthy subjects and 181 patients from the Department of Rheumatology, Medical University of Lodz who fulfilled the criteria of rheumatoid arthritis diagnosis. Genotypes were determined by Taqman SNP Genotyping Assay. rs2476601 (G/A, OR = 2.16, CI = 1.27-3.66; A/A, OR = 10.35, CI = 1.27-84.21), rs2240340 (C/T, OR = 4.35, CI = 2.55-7.42; T/T, OR = 2.80, CI = 1.43-4.10) and rs7574865 (G/T, OR = 1.97, CI = 1.21-3.21; T/T, OR = 3.33, CI = 1.01-11.02) were associated with RA in the Polish population. Rs4810485 was also associated with RA, however after Bonferroni's correction was statistically insignificant. We also found an association between minor alleles of rs2476601, rs2240340, and rs7574865 and RA (OR = 2.32, CI = 1.47-3.66; OR = 2.335, CI = 1.64-3.31; OR = 1.88, CI = 1.27-2.79, respectively). Multilocus analysis revealed an association between CGGGT and rare (below 0.02 frequency) haplotypes (OR = 12.28, CI = 2.65-56.91; OR = 3.23, CI = 1.63-6.39). In the Polish population, polymorphisms of the PADI4, PTPN22, and STAT4 genes have been detected, which are also known risk factors for RA in various other populations.

A family-wide assessment of latent STAT transcription factor interactions reveals divergent dimer repertoires.

The conversion of signal transducer and activator of transcription (STAT) proteins from latent to active transcription factors is central to cytokine signaling. Triggered by their signal-induced tyrosine phosphorylation, it is the assembly of a range of cytokine-specific STAT homo- and heterodimers that marks a key step in the transition of hitherto latent proteins to transcription activators. In contrast, the constitutive self-assembly of latent STATs and how it relates to the functioning of activated STATs is understood less well. To provide a more complete picture, we developed a co-localization-based assay and tested all 28 possible combinations of the seven unphosphorylated STAT (U-STAT) proteins in living cells. We identified five U-STAT homodimers-STAT1, STAT3, STAT4, STAT5A, and STAT5B-and two heterodimers-STAT1:STAT2 and STAT5A:STAT5B-and performed semi-quantitative assessments of the forces and characterizations of binding interfaces that support them. One STAT protein-STAT6-was found to be monomeric. This comprehensive analysis of latent STAT self-assembly lays bare considerable structural and functional diversity in the ways that link STAT dimerization before and after activation.

Association of the STAT4 Gene rs7574865 Polymorphism with IFN-γ Levels in Patients with Systemic Lupus Erythematosus.

STAT4 plays an important role in disease activity in SLE patients. STAT4 particles have the capacity to activate the transcription of genes associated with the production of TH1 and Th17 lymphocytes, with a greater predominance on the production of IFN-γ and IL-17A. The presence of variants in STAT4 genes has a major impact on the generation of autoimmunity. However, there are few studies evaluating the impact of these variants on the production of proinflammatory cytokines such as IFN-γ and IL-17A. Methods-A case-control study was carried out with 206 Mexican mestizo patients residing in Western Mexico with a diagnosis of SLE and a group of 80 patients without autoimmune diseases was captured to determine the cut-off point for high IFN-γ levels. In this study, SLE patients with high IFN-γ levels were considered as cases (cut-off > 15.6 pg/mL), and SLE patients with normal IFN-γ levels were considered as controls (cut-off ≤ 15.6 pg/mL). Disease activity was identified from the systemic lupus erythematosus disease activity index (SLEDAI). For the determination of levels of cytokines IFN-γ, IL-12, and IL17A, commercial ELISA kits were used. Genotyping of STAT4 rs7574865 (G > T) was performed by quantitative polymerase chain reaction (qPCR) using TaqMan probes. Results-The patients with SLE had a median age of 45 years with a range of disease duration from 4 years to 18 years; 45.6% were identified as having disease activity. In this sample, we identified a high IFN-γ prevalence of 35.4%. The levels of IFN-γ were higher in the patients with genotype TT than GG. We found that TT genotype conferred a higher risk of high IFN-γ when compared to the GG and GT genotypes. Conclusions-In this study, we identified that the polymorphic genotype TT of the STAT4 gene rs7574865 polymorphism is associated with increased levels of IFN-γ. However, its strength of association was weak, so complementary studies are needed to evaluate its impact on SLE patients.

Defective binding of ETS1 and STAT4 due to a mutation in the promoter region of THPO as a novel mechanism of congenital amegakaryocytic thrombocytopenia.

Congenital amegakaryocytic thrombocytopenia (CAMT) is a recessive disorder characterized by severe reduction of megakaryocytes and platelets at birth, which evolves toward bone marrow aplasia in childhood. CAMT is mostly caused by mutations in MPL (CAMT-MPL), the gene encoding the receptor of thrombopoietin (THPO), a crucial cytokine regulating hematopoiesis. CAMT can be also due to mutations affecting the THPO coding region (CAMT-THPO). In a child with the clinical picture of CAMT, we identified the homozygous c.-323C>T substitution, affecting a potential regulatory region of THPO. Although mechanisms controlling THPO transcription are not characterized, bioinformatics and in vitro analysis showed that c.-323C>T prevents the binding of transcription factors ETS1 and STAT4 to the putative THPO promoter, impairing THPO expression. Accordingly, in the proband the serum THPO concentration indicates defective THPO production. Based on these findings, the patient was treated with the THPO-mimetic agent eltrombopag, which induced a significant increase in platelet count and stable remission of bleeding symptoms. Herein, we report a novel pathogenic variant responsible for CAMT and provide new insights into the mechanisms regulating transcription of the THPO gene.

Down-Regulation-Resistant STAT4 Risk Haplotype Contributes to Lupus Nephritis Through CD4+ T Cell Interferon-γ Production.

OBJECTIVE: Variants in STAT4 are associated with systemic lupus erythematosus (SLE) and other autoimmune diseases. We undertook this study to investigate how disease-associated variants affect STAT4 expression, in particular in CD4+ T cells where STAT4 plays an essential role. METHODS: We compared Th1 differentiation between naive CD4+ T cells from healthy donors homozygous for the risk (R/R) or nonrisk (NR/NR) alleles. We analyzed epigenetic marks in STAT4 and evaluated the relevance of its third intron, assessed the consequences of Stat4 overexpression in vivo in mice, and analyzed the effects of the STAT4 genotype in patients with lupus nephritis. RESULTS: Naive CD4+ T cells from NR/NR healthy donors down-regulated STAT4 in response to interleukin-12 (IL-12). In contrast, cells from R/R healthy donors maintained high levels. R/R cells exhibited a higher abundance of transcriptionally active STAT4 and increased interferon-γ production. Accordingly, R/R healthy donors exhibited a stronger induction of local active enhancer marks. Genetic editing confirmed the presence of a negative regulatory region in the STAT4 third intron, where most of the SLE-associated STAT4 single-nucleotide polymorphisms (SNPs) are located. In vivo forced expression demonstrated that increases in Stat4 levels in T cells enhanced glomerulonephritis in mice. Accordingly, the R/R genotype was associated with suboptimal response to treatment and with worse clinical outcomes in patients with proliferative lupus nephritis. CONCLUSION: The SLE-associated STAT4 haplotype correlates with an abnormal IL-12-mediated STAT4 transcriptional regulation. Carriers of the risk variant exhibit exaggerated CD4+ proinflammatory capacities that, in the context of SLE, contribute to more severe disease. R/R patients may benefit from blockade of the IL-12/STAT4 pathway.