STAT6 - polymorphisms, haplotypes and epistasis in relation to atopy and asthma

A partial loss-of-function variant in STAT6 protects against type 2 asthma

BACKGROUND

Signal transducer and activator of transcription 6 (STAT6) is central to type 2 (T2) inflammation, and common noncoding variants at the STAT6 locus associate with various T2 inflammatory traits, including diseases, and its pathway is widely targeted in asthma treatment.

OBJECTIVE

We sought to test the association of a rare missense variant in STAT6, p.L406P, with T2 inflammatory traits, including the risk of asthma and allergic diseases, and to characterize its functional consequences in cell culture.

METHODS

The association of p.L406P with plasma protein levels, white blood cell counts, and the risk of asthma and allergic phenotypes was tested. Significant associations in other cohorts were also tested using a burden test. The effects of p.L406P on STAT6 protein function were examined in cell lines and by comparing CD4+ T-cell responses from carriers and noncarriers of the variant.

RESULTS

p.L406P associated with reduced plasma levels of STAT6 and IgE as well as with lower eosinophil and basophil counts in blood. It also protected against asthma, mostly driven by severe T2-high asthma. p.L406P led to lower IL-4-induced activation in luciferase reporter assays and lower levels of STAT6 in CD4+ T cells. We identified multiple genes with expression that was affected by the p.L406P genotype on IL-4 treatment of CD4+ T cells; the effect was consistent with a weaker IL-4 response in carriers than in noncarriers of p.L406P.

CONCLUSIONS

A partial loss-of-function variant in STAT6 resulted in dampened IL-4 responses and protection from T2-high asthma, implicating STAT6 as an attractive therapeutic target.

Toxoplasma gondii macrophage migration inhibitory factor shows anti-Mycobacterium tuberculosis potential via AZIN1/STAT1 interaction

Mycobacterium tuberculosis (MTB) is a pathogenic bacterium, belonging to the family Mycobacteriaceae, that causes tuberculosis (TB). Toxoplasma gondii macrophage migration inhibitory factor (TgMIF), a protein homolog of macrophage migration inhibitory factor, has been explored for its potential to modulate immune responses during MTB infections. We observed that TgMIF that interacts with CD74, antizyme inhibitor 1 (AZIN1), and signal transducer and activator of transcription 1 (STAT1) modulates endocytosis, restoration of mitochondrial function, and macrophage polarization, respectively. These interactions promote therapeutic efficacy in mice infected with MTB, thereby presenting a potential route to host-directed therapy development. Furthermore, TgMIF, in combination with first-line TB drugs, significantly inhibited drug-resistant MTB strains, including multidrug-resistant TB. These results demonstrate that TgMIF is potentially a multifaceted therapeutic agent against TB, acting through immune modulation, enhancement of mitochondrial function, and dependent on STAT1 and AZIN1 pathways.

Asthma is associated with a lower incidence of metastatic colorectal cancer in a US patient cohort

In previous pre-clinical studies, we examined the contribution of interleukin 4 receptor (IL4R) signaling in the progression and metastasis of colorectal cancer (CRC). Aberrant activation of this receptor can result in atopic diseases such as asthma. We hypothesized that further evidence for the contribution of excessive IL4R being associated with CRC progression could be seen in medical records, and specifically that chronic asthma patients were more likely to be diagnosed with metastatic CRC. To test this hypothesis, we took advantage of the Synthetic Derivative, a resource developed at Vanderbilt University Medical Center that hosts de-identified data taken from the electronic medical record. We developed search protocols that produced retrospective cohorts of invasive CRC patients and cancer-free equivalents. In comparing 787 metastatic CRC patients to 238 non-metastatic patients, we actually found significantly fewer asthmatics went on to develop metastatic CRC (P=0.0381). By comparing these groups together against 1197 cancer-free patients, even fewer asthmatic patients would develop invasive CRC (P<0.0001). While these results are clearly in opposition to our original hypothesis, they still support a link between chronic asthma and metastatic CRC development. One intriguing possibility, that will be examined in the future, is whether treatment for chronic asthma may be responsible for the reduction in metastatic cancer.

T-helper-2 cells and atopic disease: lessons learnt from inborn errors of immunity

Inborn errors of immunity (IEI) are caused by monogenic variants that affect the host response to bacterial, viral, and fungal pathogens. As such, individuals with IEI often present with severe, recurrent, and life-threatening infections. However, the spectrum of disease due to IEI is very broad and extends to include autoimmunity, malignancy, and atopic diseases such as eczema, atopic dermatitis, and food and environmental allergies. Here, I review IEI that affect cytokine signaling pathways that dysregulate CD4⁺ T-cell differentiation, resulting in increased T-helper-2 (Th2) cell development, function, and pathogenicity. These are elegant examples of how rare IEI can provide unique insights into more common pathologies such as allergic disease that are impacting the general population at increased frequency.

A germline STAT6 gain-of-function variant is associated with early-onset allergies

BACKGROUND

The signal transducer and activator of transcription 6 (STAT6) signaling pathway plays a central role in allergic inflammation. To date, however, there have been no descriptions of STAT6 gain-of-function variants leading to allergies in humans.

OBJECTIVE

We report a STAT6 gain-of-function variant associated with early-onset multiorgan allergies in a family with 3 affected members.

METHODS

Exome sequencing and immunophenotyping of T-helper cell subsets were conducted. The function of the STAT6 protein was analyzed by Western blot, immunofluorescence, electrophoretic mobility shift assays, and luciferase assays. Gastric organoids obtained from the index patient were used to study downstream effector cytokines.

RESULTS

We identified a heterozygous missense variant (c.1129G>A;p.Glu377Lys) in the DNA binding domain of STAT6 that was de novo in the index patient's father and was inherited by 2 of his 3 children. Severe atopic dermatitis and food allergy were key presentations. Clinical heterogeneity was observed among the affected individuals. Higher levels of peripheral blood T_H2 lymphocytes were detected. The mutant STAT6 displayed a strong preference for nuclear localization, increased DNA binding affinity, and spontaneous transcriptional activity. Moreover, gastric organoids showed constitutive activation of STAT6 downstream signaling molecules.

CONCLUSIONS

A germline STAT6 gain-of-function variant results in spontaneous activation of the STAT6 signaling pathway and is associated with an early-onset and severe allergic phenotype in humans. These observations enhance our knowledge of the molecular mechanisms underlying allergic diseases and will potentially contribute to novel therapeutic interventions.

T cell epitope of arginine kinase with CpG co-encapsulated nanoparticles attenuates a shrimp allergen-induced Th2-bias food allergy

T cell peptide-based immunotherapy (PIT) is an appealing therapeutic strategy for modulating allergic responses without IgE cross-linking. We propose a novel PIT that combines a T-cell epitope of the shrimp allergen arginine kinase (AKp) with TLR9 agonist CpG-ODN in nanoparticles (CpG-AKp NPs) to attenuate a shrimp allergen-induced food allergy. Treatment with CpG-AKp NPs demonstrated the attenuation of anaphylaxis responses such as the reduced incidence of diarrhea and hypothermia, lower levels of specific IgE and the induction of IgG2a in serum. Th2 cytokines were suppressed and higher Th1 cytokines were detected in the splenocyte culture supernatants. Treatment of CpG-AKp NPs also enhanced the protein expression of Foxp3 and IL-10 in small intestine but decreased the activation of STAT6 and GATA3 expression, which are related to differentiation of Th2. Our data indicated that CpG-AKp NPs may represent a promising PIT against shrimp allergy.

Association study in African-admixed populations across the Americas recapitulates asthma risk loci in non-African populations

Asthma is a complex disease with striking disparities across racial and ethnic groups. Despite its relatively high burden, representation of individuals of African ancestry in asthma genome-wide association studies (GWAS) has been inadequate, and true associations in these underrepresented minority groups have been inconclusive. We report the results of a genome-wide meta-analysis from the Consortium on Asthma among African Ancestry Populations (CAAPA; 7009 asthma cases, 7645 controls). We find strong evidence for association at four previously reported asthma loci whose discovery was driven largely by non-African populations, including the chromosome 17q12-q21 locus and the chr12q13 region, a novel (and not previously replicated) asthma locus recently identified by the Trans-National Asthma Genetic Consortium (TAGC). An additional seven loci reported by TAGC show marginal evidence for association in CAAPA. We also identify two novel loci (8p23 and 8q24) that may be specific to asthma risk in African ancestry populations.

Epigenetics of Mucus Hypersecretion in Chronic Respiratory Diseases

Asthma, chronic obstructive pulmonary disease, and cystic fibrosis are three chronic pulmonary diseases that affect an estimated 420 million individuals across the globe. A key factor contributing to each of these conditions is mucus hypersecretion. Although management of these diseases is vastly studied, researchers have only begun to scratch the surface of the mechanisms contributing to mucus hypersecretion. Epigenetic regulation of mucus hypersecretion, other than microRNA post-translational modification, is even more scarcely researched. Detailed study of epigenetic mechanisms, such as DNA methylation and histone modification, could not only help to better the understanding of these respiratory conditions but also reveal new treatments for them. Because mucus hypersecretion is such a complex event, there are innumerable genes involved in the process, which are beyond the scope of a single review. Therefore, the purpose of this review is to narrow the focus and summarize specific epigenetic research that has been conducted on a few aspects of mucus hypersecretion in asthma, chronic obstructive pulmonary disease, cystic fibrosis, and some cancers. Specifically, this review emphasizes the contribution of DNA methylation and histone modification of particular genes involved in mucus hypersecretion to identify possible targets for the development of future therapies for these conditions. Elucidating the role of epigenetics in these respiratory diseases may provide a breath of fresh air to millions of affected individuals around the world.

DETECTION OF RS9939609 POLYMORPHISM OF FTO GENE AND RS324011 POLYMORPHISM OF STAT6 GENE AND SEVERITY DEGREE OF BRONCHIAL ASTHMA ASSOCIATED WITH OBESITY

The aim of this research was to analyze the distribution of FTO and STAT6 genes polymorphism in patients with bronchial asthma (BA), associated with obesity (Ob) depending on the main disease severity degree. Materials and methods. The study included 117 patients 18–48 years old, divided in 3 groups. The main group (bronchial asthma, associated with obesity) included 57 patients, two groups of comparison – 30 patients with the diagnosis BA and a normal body weight, and 30 patients with obesity, but without the pathology of the bronchopulmonary system. The general genomic DNA was extracted from blood according to the standard protocol. The genetic typing was realized by the method of allele-specific amplification with the detection of results in the real time regime using TaqMan-probes, complementary to polymorphic parts of DNA. The detection of deletions in FTO and STAT 6 genes was realized by the method of polymerase chain reaction (PCR) using specific primers. Results. In the main group, among patients with BA and Ob, carriers of Т/Т genotype were 36,84 %, Т/А – 45,61 %, А/А – 17,55 % against 40 %, 60 % and 0 % respectively in PHP group by FTO gene. Carriers of С/С genotype in the main group were 38,6 %, С/Т – 35,09 %, Т/Т – 26,31 % against 40 %, 55 % and 5 % respectively in PHP group by STAT6 gene. In the main group the light persisting BA was diagnosed in 20,0 % of cases, middle severity – in 60,0 % and severe – in 20,0 % of patients. In the group of comparison this disease severity was observed in 17,7 %, 66,5 % and 15,8 % of observations, respectively. Conclusions. So, among patients with BA, associated with Ob with the middle and severe course of asthma the percent of heterozygous (Т/А) and mutant carriers (А/А) rs9939609 polymorphism of FTO gene is higher than at the light course. The analogous situation is observed at the study of rs324011 polymorphism of STAT6 (C2892T) gene among this category of patients. So, the determination of FTO and STAT6 genes polymorphism in patients with BA, associated with Ob, can be considered as a marker of the more severe course of asthma.

18β-Glycyrrhetinic acid, the major bioactive component of Glycyrrhizae Radix, attenuates airway inflammation by modulating Th2 cytokines, GATA-3, STAT6, and Foxp3 transcription factors in an asthmatic mouse model

18β-Glycyrrhetinic acid (18Gly), the major bioactive component of Glycyrrhizae Radix, possesses anti-ulcerative, anti-inflammatory, and other pharmacological properties. Although 18Gly is associated with immunoregulatory functions of allergic diseases, the pathophysiological mechanisms of 18Gly action in allergic inflammatory lung disease have not been examined. Moreover, there are no in vivo studies on the anti-asthmatic effects of 18Gly in allergic asthma. We investigated its effect and mechanism of action in airway inflammation in a BALB/c mouse model of allergic asthma. Interestingly, 18Gly strongly suppressed airway hyperresponsiveness, accumulation of inflammatory cells, and levels of T helper type 2 (Th2) cytokines (interleukin (IL)-5 and IL-13) in bronchoalveolar lavage fluid (BALF). It also attenuated lung IL-5, IL-13, and IL-4 expression, but it upregulated peroxisome proliferator-activated receptor gamma (PPARγ) mRNA expression in lungs. Moreover, it exerted immunomodulatory effects by suppressing Th2 cytokines (IL-5, IL-13) production through upregulation of forkhead box p3 (Foxp3), and downregulation of signal transducer and activator of transcription (STAT6), GATA-binding protein 3 (GATA-3), and retinoic acid-related orphan receptor γ t (RORγt) expression. These results suggest that the anti-asthmatic activity of 18Gly may occur by the suppression of IL-5, IL-13, and OVA-specific Immunoglobulin E (IgE) production through inhibition of the RORγt, STAT6, GATA-3 pathways and upregulation of the Foxp3 transcription pathway. Also, 18Gly treatment was protective against the oxidative stress by inducing significant decrease of reactive oxygen species (ROS) generation in MH-S alveolar macrophage cells. Our results suggest that 18Gly can improve allergic asthma and can be a novel therapeutic component for the treatment of allergic asthma.

Analysis of changes in expression of IL-4/IL-13/STAT6 pathway and correlation with the selected clinical parameters in patients with atopic asthma

INTRODUCTION

Asthma is associated with activation of interleukin-4 (IL-4)/interleukin-13 (IL-13)/signal transducer and activator of transcription factor-6(STAT6) inflammatory response via overexpression of all pathway components: IL-4, IL-13, and STAT6.

OBJECTIVES

To evaluate the association of IL-4, IL-13, and STAT6 expression and immunoexpression with atopic asthma development.

PATIENTS AND METHODS

Fifty patients with atopic asthma and 20 healthy controls were enrolled into the study. Relative gene expression was analyzed by qPCR method. Immunoexpression was assessed by ELISA method.

RESULTS

The expression levels of IL-4, IL-13, and STAT6 were higher in patients compared to the controls, but a statistically significant difference was observed only for IL-13 (P = 0.03). In immunoexpression analysis, a statistically significant difference between patients and controls was found for IgE (P = 0.03). Significant positive correlations in the patient group were found between IL-13 gene expression and total level of serum IgE (rho = 0.230, P = 0.033), STAT6 gene/STAT6 protein and total level of serum IgE (STAT6: rho = 0.077, P = 0.038; STAT6: rho = 0.049, P = 0.042), IL-4, and STAT6 expression (rho = 0.098, P = 0.048). Any significant correlations were found between expression/immunoexpression levels of the studied genes and clinical classification, clinical features, or lung function parameters.

CONCLUSIONS

Our data support the role of Th2 cytokines (IL-4, IL-13) and STAT6 in Th1/Th2 imbalance and highlight the etiological relationship between IL-4/IL-13/STAT6 signaling and atopy and asthma.

An SNP marker at the STAT6 locus can identify the hybrids between rhesus (Macaca mulatta) and long-tailed macaques (M. fascicularis) in Thailand: a rapid and simple screening method and its application

A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) assay was developed to genetically discriminate rhesus (Macaca mulatta) macaques from long-tailed (M. fascicularis) macaques. The 745 bp PCR amplicon of the STAT6 locus that spans a potentially species-diagnostic single nucleotide polymorphism (SNP) marker was digested with ApaI and gel electrophoresed to give (1) two (234 and 511 bp), (2) one (745 bp) and (3) three (234, 511 and 745 bp) band patterns that correspond to the genotypes G/G (long-tailed macaque specific homozygote), A/A (rhesus macaque specific homozygote) and A/G (hybrid specific heterozygote), respectively. The diagnostic robustness and efficiency of this PCR-RFLP assay was tested on wild rhesus and long-tailed macaques inhabiting Thailand and a known hybrid population. The Indochinese and Sundaic long-tailed macaque samples (n = 18) all showed a homozygous G/G pattern, while the Indochinese rhesus macaques (n = 10) all showed a homozygous A/A pattern. The rhesus/long-tailed hybrid population at Khao Khieow Open Zoo, which resulted from an introduced group of rhesus macaques that hybridized with the indigenous long-tailed macaques about 20 years ago, revealed 47% (56/118 samples analyzed) with the heterogenous A/G genotype. In addition, the frequency of the rhesus-specific allele A significantly decreased in the hybrid population during 2006-2014, where a strong association between the STAT6 genotype and the morphology of the individuals was detected. In conclusion, a robust PCR-RFLP assay allows a simple, effective and inexpensive approach, in particular for field studies, to assess hybrid individuals between rhesus and long-tailed macaques. Although this assay cannot conclusively identify all the hybrids over two or more generations, it at least can allow the evaluation of the process of hybridization, and so it is applicable to the assessment of the status of natural or anthropogenic hybridization between the two species across their geographic range.

Epigenomics and allergic disease

Allergic disease development is affected by both genes and the environment, and epigenetic mechanisms are hypothesized to mediate these environmental effects. In this article, we discuss the link between the environment, DNA methylation and allergic disease, as well as questions of causality inherent to analyses of DNA methylation. From the practical side, we describe characteristics of allergic phenotypes and contrast different epidemiologic study designs used in epigenetic research. We examine methodological considerations, how best to conduct preprocessing and analysis of DNA methylation data sets, and the latest methods, technologies and discoveries in this rapidly advancing field. DNA methylation and other epigenetic marks are firmly entwined with allergic disease, a link that may hold the basis for future allergic disease diagnosis and treatment.

Expression data analysis to identify biomarkers associated with asthma in children

Asthma is characterized by recurrent episodes of wheezing, shortness of breath, chest tightness, and coughing. It is usually caused by a combination of complex and incompletely understood environmental and genetic interactions. We obtained gene expression data with high-throughput screening and identified biomarkers of children's asthma using bioinformatics tools. Next, we explained the pathogenesis of children's asthma from the perspective of gene regulatory networks: DAVID was applied to perform Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enriching analysis for the top 3000 pairs of relationships in differentially regulatory network. Finally, we found that HAND1, PTK1, NFKB1, ZIC3, STAT6, E2F1, PELP1, USF2, and CBFB may play important roles in children's asthma initiation. On account of regulatory impact factor (RIF) score, HAND1, PTK7, and ZIC3 were the potential asthma-related factors. Our study provided some foundations of a strategy for biomarker discovery despite a poor understanding of the mechanisms underlying children's asthma.