Demethylation of the FCER1G promoter leads to FcεRI overexpression on monocytes of patients with atopic dermatitis

Comprehensive analysis reveals the tumor suppressor role of macrophage signature gene FCER1G in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) progression is closely linked to the role of macrophages. This study utilized single-cell RNA sequencing and genomic analysis to explore the characteristic genes of macrophages in HCC and their impact on patient prognosis. We obtained single-cell se-quencing data from seven HCC samples in the GEO database. Through principal component analysis and t-SNE dimensionality reduction, we identified 2,000 highly variable genes and per-formed clustering and annotation of 17 cell clusters, revealing 482 macrophage-related feature genes. A LASSO regression model based on these genes was developed to predict the prognosis of HCC patients, with validation in the TCGA-LIHC cohort demonstrating model accuracy (AUC = 0.78, 0.72, 0.71 for 1-, 3-, and 5-year survival rates, respectively). Additionally, patients in the high-risk group exhibited elevated tumor stemness scores, although no significant differences were observed in microsatellite instability (MSI) and tumor mutational burden (TMB) scores. Immune-related analyses revealed that FCER1G expression was downregulated in HCC and was associated with key pathways such as apoptosis and ferroptosis. Reduced FCER1G expression significantly affected HCC cell proliferation and migration. Our prognostic model provides new insights into precision and immunotherapy for HCC and holds significant implications for future clinical applications.

Resolution of Chronic Inflammation, Restoration of Epigenetic Disturbances and Correction of Dysbiosis as an Adjunctive Approach to the Treatment of Atopic Dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with multifactorial and unclear pathogenesis. Its development is characterized by two key elements: epigenetic dysregulation of molecular pathways involved in AD pathogenesis and disrupted skin and gut microbiota (dysbiosis) that jointly trigger and maintain chronic inflammation, a core AD characteristic. Current data suggest that failed inflammation resolution is the main pathogenic mechanism underlying AD development. Inflammation resolution is provided by specialized pro-resolving mediators (SPMs) derived from dietary polyunsaturated fatty acids acting through cognate receptors. SPM levels are reduced in AD patients. Administration of SPMs or their stable, small-molecule mimetics and receptor agonists, as well as supplementation with probiotics/prebiotics, demonstrate beneficial effects in AD animal models. Epidrugs, compounds capable of restoring disrupted epigenetic mechanisms associated with the disease, improve impaired skin barrier function in AD models. Based on these findings, we propose a novel, multilevel AD treatment strategy aimed at resolving chronic inflammation by application of SPM mimetics and receptor agonists, probiotics/prebiotics, and epi-drugs. This approach can be used in conjunction with current AD therapy, resulting in AD alleviation.

Integrating multi-omics approaches in deciphering atopic dermatitis pathogenesis and future therapeutic directions

Atopic dermatitis (AD), a complex and heterogeneous chronic inflammatory skin disorder, manifests in a spectrum of clinical subtypes. The application of genomics has elucidated the role of genetic variations in predisposing individuals to AD. Transcriptomics, analyzing gene expression alterations, sheds light on the molecular underpinnings of AD. Proteomics explores the involvement of proteins in AD pathophysiology, while epigenomics examines the impact of environmental factors on gene expression. Lipidomics, which investigates lipid profiles, enhances our understanding of skin barrier functionalities and their perturbations in AD. This review synthesizes insights from these omics approaches, highlighting their collective importance in unraveling the intricate pathogenesis of AD. The review culminates by projecting future trajectories in AD research, particularly the promise of multi-omics in forging personalized medicine and novel therapeutic interventions. Such an integrated multi-omics strategy is poised to transform AD comprehension and management, steering towards more precise and efficacious treatment modalities.

The pathogenesis of food allergy and protection offered by dietary compounds from the perspective of epigenetics

Food allergy is a global food safety concern, with an increasing prevalence in recent decades. However, the immunological and cellular mechanisms involved in allergic reactions remain incompletely understood, which impedes the development of effective prevention and treatment strategies. Current evidence supports those epigenetic modifications regulate the activation of immune cells, and their dysregulation can contribute to the development of food allergies. Patients with food allergy show epigenetic alterations that lead to the onset, duration and recovery of allergic disease. Moreover, many preclinical studies have shown that certain dietary components exert nutriepigenetic effects in changing the course of food allergies. In this review, we provide an up-to-date overview of DNA methylation, noncoding RNA and histone modification, with a focus on their connections to food allergies. Following this, we discuss the epigenetic mechanisms that regulate the activation and differentiation of innate and adapted immune cell in the context of food allergies. Subsequently, this study specifically focuses on the multidimensional epigenetic effects of dietary components in modulating the immune response, which holds promise for preventing food allergies in the future.

Epigenetic control of inflammation in Atopic Dermatitis

Atopic dermatitis (AD), also known as atopic eczema, is a common but also complex chronic, itchy skin condition with underlying inflammation of the skin. This skin ailment is prevalent worldwide and affects people of all ages, particularly children below five years of age. The itching and resulting rashes in AD patients are often the result of inflammatory signals, thus necessitating a closer look at the inflammation-regulating mechanisms for putative relief, care and therapy. Several chemical- as well as genetically-induced animal models have established the importance of targeting pro-inflammatory AD microenvironment. Epigenetic mechanisms are gaining attention towards a better understanding of the onset as well as the progression of inflammation. Several physiological processes with implications in pathophysiology of AD, such as, barrier dysfunction either due to reduced filaggrin / human β-defensins or altered microbiome, reprograming of Fc receptors with resulting overexpression of high affinity IgE receptors, elevated eosinophil numbers or the elevated IL-22 production by CD4 + T cells have underlying epigenetic mechanisms that include differential promoter methylation and/or regulation by non-coding RNAs. Reversing these epigenetic changes has been verified to reduce inflammatory burden through altered secretion of cytokines IL-6, IL-4, IL-13, IL-17, IL-22 etc, with benefit against AD progression in experimental models. A thorough understanding of epigenetic remodeling of inflammation in AD has the potential of opening avenues for novel diagnostic, prognostic and therapeutic options.

Multi-Omics Approach to Improved Diagnosis and Treatment of Atopic Dermatitis and Psoriasis

Psoriasis and atopic dermatitis fall within the category of cutaneous immune-mediated inflammatory diseases (IMIDs). The prevalence of IMIDs is increasing in industrialized societies, influenced by both environmental changes and a genetic predisposition. However, the exact immune factors driving these chronic, progressive diseases are not fully understood. By using multi-omics techniques in cutaneous IMIDs, it is expected to advance the understanding of skin biology, uncover the underlying mechanisms of skin conditions, and potentially devise precise and personalized approaches to diagnosis and treatment. We provide a narrative review of the current knowledge in genomics, epigenomics, and proteomics of atopic dermatitis and psoriasis. A literature search was performed for articles published until 30 November 2023. Although there is still much to uncover, recent evidence has already provided valuable insights, such as proteomic profiles that permit differentiating psoriasis from mycosis fungoides and β-defensin 2 correlation to PASI and its drop due to secukinumab first injection, among others.

Lipidomics and Metabolomics in Infant Atopic Dermatitis: What's the Correlation with Early Nutrition?

To date, the complex picture of atopic dermatitis (AD) has not yet been fully clarified, despite the important prevalence of this disease in the pediatric population (20%) and the possibility of persistence into adulthood, with important implications for the quality of life of those affected, as well as significant social and financial costs. The most recent scientific evidence suggests a new interpretation of AD, highlighting the important role of the environment, particularly that of nutrition in the early stages of development. In fact, the new indications seem to point out the harmful effect of elimination diets, except in rare cases, the uselessness of chrono-insertions during complementary feeding and some benefits, albeit weak, of breastfeeding in those at greater risk. In this context, metabolomics and lipidomics can be necessary for a more in-depth knowledge of the complex metabolic network underlying this pathology. In fact, an alteration of the metabolic contents in children with AD has been highlighted, especially in correlation to the intestinal microbiota. While preliminary lipidomic studies showed the usefulness of a more in-depth knowledge of the alterations of the skin barrier to improve the development of baby skin care products. Therefore, investigating the response of different allergic phenotypes could be useful for better patient management and understanding, thus providing an early intervention on dysbiosis necessary to regulate the immune response from the earliest stages of development.

Identification of FCER1G as a cyclosporin A plus corticosteroid sensitization gene in female patients with Vogt-Koyanagi-Harada disease

The resistance development of the combination regimen of corticosteroids (CS) with cyclosporin A (CsA) leads to therapeutic failure of some patients with autoimmune diseases. In the male patients with Vogt-Koyanagi-Harada (VKH) disease, we have identified RPS4Y1 as an important resistance gene of the regimen and a functional mediator of chlorambucil (CLB). However, it remains unclear what is responsible for the resistance in female patients. In the present study, we performed RNA sequencing, tandem mass tag (TMT) proteomics, gain- and loss-of-function assays and rescue assays to screen and validate potential resistant mediators. The results showed that only Fc epsilon receptor Ig (FCER1G) exhibited significantly differential expression in CD4+ T cells among female CsA & CS resistant, sensitive and CLB & CsA & CS treated patients at transcription and protein levels. Inhibition of FCER1G was demonstrated to modulate CD4+ T cell resistance to CsA & CS in female patients. Importantly, the inhibition was mediated by elevated DNA methylation in the promoter region of the FCER1G gene. Moreover, we found that the salvage effect of CLB on CsA & CS resistance was mediated by an increased FCER1G expression via DNA demethylation in female patients. Taken together, the downregulation of FCER1G due to DNA hypermethylation is responsible for the resistance to CsA & CS and CLB reverses this resistance by inducing FCER1G expression via DNA demethylation in female patients. Modulation of FCER1G would be a promising sensitization strategy in female patients with resistance to CsA & CS.

Role of the membrane-spanning 4A gene family in lung adenocarcinoma

Lung adenocarcinoma, which is the second most prevalent cancer in the world, has a poor prognosis and a low 5-year survival rate. The MS4A protein family is crucial to disease development and progression, particularly for cancers, allergies, metabolic disorders, autoimmune diseases, infections, and neurodegenerative disorders. However, its involvement in lung adenocarcinoma remains unclear. In this study, we found that 11 MS4A family genes were upregulated or downregulated in lung adenocarcinoma. Furthermore, we described the genetic variation landscape of the MS4A family in lung adenocarcinoma. Notably, through functional enrichment analysis, we discovered that the MS4A family is involved in the immune response regulatory signaling pathway and the immune response regulatory cell surface receptor signaling pathway. According to the Kaplan-Meier curve, patients with lung adenocarcinoma having poor expression of MS4A2, MS4A7, MS4A14, and MS4A15 had a low overall survival rate. These four prognostic genes are substantially associated with immune-infiltrating cells, and a prognosis model incorporating them may more accurately predict the overall survival rate of patients with lung adenocarcinoma than current models. The findings of this study may offer creative suggestions and recommendations for the identification and management of lung adenocarcinoma.

Advances in Current Drugs and Formulations for the Management of Atopic Dermatitis

Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disease with a complex pathophysiology. Treatment of AD remains challenging owing to the presence of a wide spectrum of clinical phenotypes and limited response to existing therapies. However, recent genetic, immunological, and pathophysiological insights into the disease mechanism resulted in the invention of novel therapeutic drug candidates. This review provides a comprehensive overview of current therapies and assesses various novel drug delivery strategies currently under clinical investigation. Further, this review majorly emphasizes on various topical treatments including emollient therapies, barrier repair agents, topical corticosteroids (TCS), phosphodiesterase 4 (PDE4) inhibitors, calcineurin inhibitors, and Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway inhibitors. It also discusses biological and systemic therapies, upcoming treatments based on ongoing clinical trials. Additionally, this review scrutinized the use of pharmaceutical inactive ingredients in the approved topical dosage forms for AD treatment.

Quantifying the role of transcript levels in mediating DNA methylation effects on complex traits and diseases

High-dimensional omics datasets provide valuable resources to determine the causal role of molecular traits in mediating the path from genotype to phenotype. Making use of molecular quantitative trait loci (QTL) and genome-wide association study (GWAS) summary statistics, we propose a multivariable Mendelian randomization (MVMR) framework to quantify the proportion of the impact of the DNA methylome (DNAm) on complex traits that is propagated through the assayed transcriptome. Evaluating 50 complex traits, we find that on average at least 28.3% (95% CI: [26.9%-29.8%]) of DNAm-to-trait effects are mediated through (typically multiple) transcripts in the cis-region. Several regulatory mechanisms are hypothesized, including methylation of the promoter probe cg10385390 (chr1:8'022'505) increasing the risk for inflammatory bowel disease by reducing PARK7 expression. The proposed integrative framework can be extended to other omics layers to identify causal molecular chains, providing a powerful tool to map and interpret GWAS signals.

A Prognostic Nomogram for Hepatocellular Carcinoma Based on Wound Healing and Immune Checkpoint Genes

BACKGROUND AND AIMS

Wound healing and tumor progression share some common biological features; however, how variations in wound healing patterns affect hepatocellular carcinoma (HCC) prognosis remains unclear.

METHODS

We analyzed the wound healing patterns of 594 HCC samples from The Cancer Genome Atlas (TCGA) and the International Cancer Genome Consortium (ICGC) and correlated them with immune infiltration and the expression levels of immune checkpoint genes. A risk score, which we named the "heal.immune" score, was established via stepwise Cox estimation. We constructed a nomogram based on age, sex, TNM stage, and heal.immune score and explored its predictive value for HCC prognosis. Seventy-four clinical patients were enrolled in this study, and all were from Huashan Hospital of Fudan University between 2015 and 2017 to serve as an independent validation group.

RESULTS

We identified two distinct wound healing patterns in HCC. The biological processes of healing cluster 1 (C1) are related to metabolism, while those of healing cluster 2 (C2) are related to the inflammatory response and immune cell accumulation. A total of 565 wound healing-related genes (based on Gene Ontology) and 25 immune checkpoint genes were considered. By analyzing differentially expressed genes and implementing a stepwise Cox estimation analysis, six genes with p values less than 0.02 in a multivariate Cox estimation were chosen as the "heal.immune" gene set (FCER1G, PLAT, ITGA5, CCNB1, CD86 and CD40). The "heal.immune" gene set, as an OS risk factor, was further validated in Fudan cohort. We constructed a nomogram to predict the 1-, 3- and 5-year overall survival (OS) in the TCGA cohort. The area under curve vales of the receiver characteristic operator curves were 0.82, 0.76 and 0.73 in the training group and 0.84, 0.76 and 0.72 in the test group.

CONCLUSIONS

We established a prognostic nomogram based on the heal.immune gene signature, which includes six wound healing- and immunity-related genes. This nomogram accurately predicts the OS of HCC patients.

FCER1G Gene Hypomethylation in Patients with Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease that, when improperly treated, leads to disability in patients. Various factors that may cause the development and activity of RA are being considered. Epigenetic factors are also receiving increasing attention. In our study, we analyzed the association between FCER1G gene methylation and RA activity. We conducted our study in 50 RA patients and 24 controls. The patients were divided into two groups in terms of high disease activity and remission. Quantitative real-time methylation-specific PCR was used to analyze the methylation status of the investigated genes. We observed that RA patients have lower levels of methylation of the FCER1G gene compared to controls, but we did not find any difference in the methylation status of this gene between patients with high disease activity and remission. The results of this study suggest that FCER1G gene methylation may be a new potential epigenetic marker of RA that is independent of disease activity.

Identification of Hub Genes and Therapeutic Agents for IgA Nephropathy Through Bioinformatics Analysis and Experimental Validation

Background

IgA nephropathy (IgAN) is the most common primary glomerular disease and the leading cause of the end-stage renal disease in the world. The pathogenesis of IgAN has not been well elucidated, and yet treatment is limited. High-throughput microarray has been applied for elucidating molecular biomarkers and potential mechanisms involved in IgAN. This study aimed to identify the potential key genes and therapeutics associated with IgAN using integrative bioinformatics and transcriptome-based computational drug repurposing approach.

Methods

Three datasets of mRNA expression profile were obtained from the gene expression omnibus database and differentially expressed genes (DEGs) between IgAN glomeruli and normal tissue were identified by integrated analysis. Gene ontology and pathway enrichment analyses of the DEGs were performed by R software, and protein-protein interaction networks were constructed using the STRING online search tool. External dataset and immunohistochemical assessment of kidney biopsy specimens were used for hub gene validation. Potential compounds for IgAN therapy were obtained by Connectivity Map (CMap) analysis and preliminarily verified in vitro. Stimulated human mesangial cells were collected for cell proliferation and cell cycle analysis using cell counting kit 8 and flow cytometry, respectively.

Results

134 DEGs genes were differentially expressed across kidney transcriptomic data from IgAN patients and healthy living donors. Enrichment analysis showed that the glomerular compartments underwent a wide range of interesting pathological changes during kidney injury, focused on anion transmembrane transporter activity and protein digestion and absorption mostly. Hub genes (ITGB2, FCER1G, CSF1R) were identified and verified to be significantly upregulated in IgAN patients, and associated with severity of renal lesions. Computational drug repurposing with the CMap identified tetrandrine as a candidate treatment to reverse IgAN hub gene expression. Tetrandrine administration significantly reversed mesangial cell proliferation and cell cycle transition.

Conclusion

The identification of DEGs and related therapeutic strategies of IgAN through this integrated bioinformatics analysis provides a valuable resource of therapeutic targets and agents of IgAN. Especially, our findings suggest that tetrandrine might be beneficial for IgAN, which deserves future research.

Identification of Cell Markers and Their Expression Patterns in Skin Based on Single-Cell RNA-Sequencing Profiles

Atopic dermatitis and psoriasis are members of a family of inflammatory skin disorders. Cellular immune responses in skin tissues contribute to the development of these diseases. However, their underlying immune mechanisms remain to be fully elucidated. We developed a computational pipeline for analyzing the single-cell RNA-sequencing profiles of the Human Cell Atlas skin dataset to investigate the pathological mechanisms of skin diseases. First, we applied the maximum relevance criterion and the Boruta feature selection method to exclude irrelevant gene features from the single-cell gene expression profiles of inflammatory skin disease samples and healthy controls. The retained gene features were ranked by using the Monte Carlo feature selection method on the basis of their importance, and a feature list was compiled. This list was then introduced into the incremental feature selection method that combined the decision tree and random forest algorithms to extract important cell markers and thus build excellent classifiers and decision rules. These cell markers and their expression patterns have been analyzed and validated in recent studies and are potential therapeutic and diagnostic targets for skin diseases because their expression affects the pathogenesis of inflammatory skin diseases.

Epigenetic regulation of pediatric and neonatal immune responses

Epigenetic regulation of transcription is a collective term that refers to mechanisms known to regulate gene transcription without changing the underlying DNA sequence. These mechanisms include DNA methylation and histone tail modifications which influence chromatin accessibility, and microRNAs that act through post-transcriptional gene silencing. Epigenetics is known to regulate a variety of biological processes, and the role of epigtenetics in immunity and immune-mediated diseases is becoming increasingly recognized. While DNA methylation is the most widely studied, each of these systems play an important role in the development and maintenance of appropriate immune responses. There is clear evidence that epigenetic mechanisms contribute to developmental stage-specific immune responses in a cell-specific manner. There is also mounting evidence that prenatal exposures alter epigenetic profiles and subsequent immune function in exposed offspring. Early life exposures that are associated with poor long-term health outcomes also appear to impact immune specific epigenetic patterning. Finally, each of these epigenetic mechanisms contribute to the pathogenesis of a wide variety of diseases that manifest during childhood. This review will discuss each of these areas in detail. IMPACT: Epigenetics, including DNA methylation, histone tail modifications, and microRNA expression, dictate immune cell phenotypes. Epigenetics influence immune development and subsequent immune health. Prenatal, perinatal, and postnatal exposures alter immune cell epigenetic profiles and subsequent immune function. Numerous pediatric-onset diseases have an epigenetic component. Several successful strategies for childhood diseases target epigenetic mechanisms.

Prioritization of candidate causal genes for asthma in susceptibility loci derived from UK Biobank

To identify candidate causal genes of asthma, we performed a genome-wide association study (GWAS) in UK Biobank on a broad asthma definition (n = 56,167 asthma cases and 352,255 controls). We then carried out functional mapping through transcriptome-wide association studies (TWAS) and Mendelian randomization in lung (n = 1,038) and blood (n = 31,684) tissues. The GWAS reveals 72 asthma-associated loci from 116 independent significant variants (P_GWAS < 5.0E-8). The most significant lung TWAS gene on 17q12-q21 is GSDMB (P_TWAS = 1.42E-54). Other TWAS genes include TSLP on 5q22, RERE on 1p36, CLEC16A on 16p13, and IL4R on 16p12, which all replicated in GTEx lung (n = 515). We demonstrate that the largest fold enrichment of regulatory and functional annotations among asthma-associated variants is in the blood. We map 485 blood eQTL-regulated genes associated with asthma and 50 of them are causal by Mendelian randomization. Prioritization of druggable genes reveals known (IL4R, TSLP, IL6, TNFSF4) and potentially new therapeutic targets for asthma.

Analysis of deficiency of adenosine deaminase 2 pathogenesis based on single-cell RNA sequencing of monocytes

Deficiency of adenosine deaminase 2 (DADA2) is a rare autosomal recessive disease caused by loss-of-function variants in the ADA2 gene. DADA2 typically presents in childhood and is characterized by vasculopathy, stroke, inflammation, immunodeficiency, as well as hematologic manifestations. ADA2 protein is predominantly present in stimulated monocytes, dendritic cells, and macrophages. To elucidate molecular mechanisms in DADA2, CD14⁺ monocytes from 14 patients and 6 healthy donors were analyzed using single-cell RNA sequencing (scRNA-seq). Monocytes were purified by positive selection based on CD14 expression. Subpopulations were imputed from their transcriptomes. Based on scRNA-seq, monocytes could be classified as classical, intermediate, and nonclassical. Further, we used gene pathway analytics to interpret patterns of up- and down-regulated gene transcription. In DADA2, the frequency of nonclassical monocytes was higher compared with that of healthy donors, and M1 macrophage markers were up-regulated in patients. By comparing gene expression of each monocyte subtype between patients and healthy donors, we identified upregulated immune response pathways, including IFNα/β and IFNγ signaling, in all monocyte subtypes. Distinctively, the TNFR2 noncanonical NF-κB pathway was up-regulated only in nonclassical monocytes. Patients' plasma showed increased IFNγ and TNFα levels. Our results suggest that elevated IFNγ activates cell signaling, leading to differentiation into M1 macrophages from monocytes and release of TNFα. Immune responses and more general response to stimuli pathways were up-regulated in DADA2 monocytes, and protein synthesis pathways were down-regulated, perhaps as stress responses. Our identification of novel aberrant immune pathways has implications for therapeutic approaches in DADA2 (registered at clinicaltrials.gov NCT00071045).

Epigenetic-modifying therapies: An emerging avenue for the treatment of inflammatory skin diseases

Epigenetic modifications include DNA methylation, histone modification and the action of microRNAs. These mechanisms coordinate in complex networks to control gene expression, thereby regulating key physiological processes in the skin and immune system. Recently, researchers have turned to the epigenome to understand the pathogenesis of inflammatory skin diseases. In psoriasis and atopic dermatitis, epigenetic modifications contribute to key pathogenic events such as immune activation, T-cell polarization and keratinocyte dysfunction. These discoveries have introduced new possibilities for the treatment of skin diseases; unlike genetics, epigenetic alterations are readily modifiable and potentially reversible. In this viewpoint essay, we summarize the current state of epigenetic research in inflammatory skin diseases and propose that targeting the histone machinery is a promising avenue for the development of new therapies for psoriasis and atopic dermatitis. Expanding on the progress that has already been made in the field of cancer epigenetics, we discuss existing epigenetic-modifying tools that can be applied to the treatment of inflammatory skin diseases and consider future directions for investigation in order to allow for the widespread clinical application of such therapies.

Epigenetic and metabolic regulation of epidermal homeostasis

Continuous exposure of the skin to environmental, mechanical and chemical stress necessitates constant self‐renewal of the epidermis to maintain its barrier function. This self‐renewal ability is attributed to epidermal stem cells (EPSCs), which are long‐lived, multipotent cells located in the basal layer of the epidermis. Epidermal homeostasis – coordinated proliferation and differentiation of EPSCs – relies on fine‐tuned adaptations in gene expression which in turn are tightly associated with specific epigenetic signatures and metabolic requirements. In this review, we will briefly summarize basic concepts of EPSC biology and epigenetic regulation with relevance to epidermal homeostasis. We will highlight the intricate interplay between mitochondrial energy metabolism and epigenetic events – including miRNA‐mediated mechanisms – and discuss how the loss of epigenetic regulation and epidermal homeostasis manifests in skin disease. Discussion of inherited epidermolysis bullosa (EB) and disorders of cornification will focus on evidence for epigenetic deregulation and failure in epidermal homeostasis, including stem cell exhaustion and signs of premature ageing. We reason that the epigenetic and metabolic component of epidermal homeostasis is significant and warrants close attention. Charting epigenetic and metabolic complexities also represents an important step in the development of future systemic interventions aimed at restoring epidermal homeostasis and ameliorating disease burden in severe skin conditions.

Epigenetics in Non-tumor Immune-Mediated Skin Diseases

Epigenetics is the study of the mechanisms that regulate gene expression without modifying DNA sequences. Knowledge of and evidence about how epigenetics plays a causative role in the pathogenesis of many skin diseases is increasing. Since the epigenetic changes present in tumor diseases have been thoroughly reviewed, we believe that knowledge of the new epigenetic findings in non-tumor immune-mediated dermatological diseases should be of interest to the general dermatologist. Hence, the purpose of this review is to summarize the recent literature on epigenetics in most non-tumor dermatological pathologies, focusing on psoriasis. Hyper- and hypomethylation of DNA methyltransferases and methyl-DNA binding domain proteins are the most common and studied methylation mechanisms. The acetylation and methylation of histones H3 and H4 are the most frequent and well-characterized histone modifications and may be associated with disease severity parameters and serve as therapeutic response markers. Many specific microRNAs dysregulated in non-tumor dermatological disease have been reviewed. Deepening the study of how epigenetic mechanisms influence non-tumor immune-mediated dermatological diseases might help us better understand the role of interactions between the environment and the genome in the physiopathogenesis of these diseases.

Prognostic and predictive value of FCER1G in glioma outcomes and response to immunotherapy

PURPOSE

Glioma is the most prevalent malignant form of brain tumors, with a dismal prognosis. Currently, cancer immunotherapy has emerged as a revolutionary treatment for patients with advanced highly aggressive therapy-resistant tumors. However, there is no effective biomarker to reflect the response to immunotherapy in glioma patient so far. So we aim to assess the clinical predictive value of FCER1G in patients with glioma.

METHODS

The expression level and correlation between clinical prognosis and FER1G levels were analyzed with the data from CGGA, TCGA, and GEO database. Univariate and multivariate cox regression model was built to predict the prognosis of glioma patients with multiple factors. Then the correlation between FCER1G with immune cell infiltration and activation was analyzed. At last, we predict the immunotherapeutic response in both high and low FCER1G expression subgroups.

RESULTS

FCER1G was significantly higher in glioma with greater malignancy and predicted poor prognosis. In multivariate analysis, the hazard ratio of FCER1G expression (Low versus High) was 0.66 and 95 % CI is 0.54 to 0.79 (P < 0.001), whereas age (HR = 1.26, 95 % CI  1.04-1.52), grade (HR = 2.75, 95 % CI 2.06-3.68), tumor recurrence (HR = 2.17, 95 % CI  1.81-2.62), IDH mutant (HR = 2.46, 95 % CI 1.97-3.01) and chemotherapeutic status (HR = 1.4, 95 % CI  1.20-1.80) are also included. Furthermore, we illustrated that gene FCER1G stratified glioma cases into high and low FCER1G expression subgroups that demonstrated with distinct clinical outcomes and T cell activation. At last, we demonstrated that high FCER1G levels presented great immunotherapeutic response in glioma patients.

CONCLUSIONS

This study demonstrated FCER1G as a novel predictor for clinical diagnosis, prognosis, and response to immunotherapy in glioma patient. Assess expression of FCER1G is a promising method to discover patients that may benefit from immunotherapy.

The DNA methylation of FOXO3 and TP53 as a blood biomarker of late-onset asthma

BACKGROUND

Late-onset asthma (LOA) is beginning to account for an increasing proportion of asthma patients, which is often underdiagnosed in the elderly. Studies on the possible relations between aging-related genes and LOA contribute to the diagnosis and treatment of LOA. Forkhead Box O3 (FOXO3) and TP53 are two classic aging-related genes. DNA methylation varies greatly with age which may play an important role in the pathogenesis of LOA. We supposed that the differentially methylated sites of FOXO3 and TP53 associated with clinical phenotypes of LOA may be useful biomarkers for the early screening of LOA.

METHODS

The mRNA expression and DNA methylation of FOXO3 and TP53 in peripheral blood of 43 LOA patients (15 mild LOA, 15 moderate LOA and 13 severe LOA) and 60 healthy controls (HCs) were determined. The association of methylated sites with age was assessed by Cox regression to control the potential confounders. Then, the correlation between differentially methylated sites (DMSs; p-value < 0.05) and clinical lung function in LOA patients was evaluated. Next, candidate DMSs combining with age were evaluated to predict LOA by receiver operating characteristic (ROC) analysis and principal components analysis (PCA). Finally, HDM-stressed asthma model was constructed, and DNA methylation inhibitor 5-Aza-2'-deoxycytidine (5-AZA) were used to determine the regulation of DNA methylation on the expression of FOXO3 and TP53.

RESULTS

Compared with HCs, the mRNA expression and DNA methylation of FOXO3 and TP53 vary significantly in LOA patients. Besides, 8 DMSs from LOA patients were identified. Two of the DMSs, chr6:108882977 (FOXO3) and chr17:7591672 (TP53), were associated with the severity of LOA. The combination of the two DMSs and age could predict LOA with high accuracy (AUC values = 0.924). In HDM-stressed asthma model, DNA demethylation increased the expression of FOXO3 and P53.

CONCLUSIONS

The mRNA expression of FOXO3 and TP53 varies significantly in peripheral blood of LOA patients, which may be due to the regulation of DNA methylation. FOXO3 and TP53 methylation is a suitable blood biomarker to predict LOA, which may be useful targets for the risk diagnosis and clinical management of LOA.

Weighted gene co-expression network analysis identifies FCER1G as a key gene associated with diabetic kidney disease

Background

Diabetic kidney disease (DKD) is the primary cause of end-stage renal disease. However, the pathogenesis of DKD remains unclarified, and there is an urgent need for improved treatments. Recently, many crucial genes closely linked to the molecular mechanism underlying various diseases were discovered using weighted gene co-expression network analysis.

Methods

We used a gene expression omnibus series dataset GSE104948 with 12 renal glomerular DKD tissue samples and 18 control samples obtained from the gene expression omnibus database and performed weighted gene co-expression network analysis. After obtaining the trait-related modules, gene ontology and Kyoto encyclopedia of genes and genomes enrichment analyses of the modules were conducted and the key gene associated with DKD was selected from the top two most significant gene ontology terms using the maximal clique centrality method. Finally, we verified the key gene using protein-protein interaction analysis, additional datasets, and explored the relationship between the key gene and DKD renal function using the Nephroseq v5 online database.

Results

Among the 10 gene co-expression modules identified, the darkorange2 and red modules were highly related to DKD and the normal biological process, respectively. Majority of the genes in the darkorange2 module were related to immune and inflammatory responses, and potentially related to the progression of DKD due to their abnormal up-regulation. After performing sub-network analysis of the genes extracted from the top two most significant gene ontology terms and calculating the maximal clique centrality values of each gene, FCER1G, located at the center of the protein-protein interaction network, was identified as a key gene related to DKD. Furthermore, gene expression omnibus validation in additional datasets also showed that FCER1G was overexpressed in DKD compared with normal tissues. Finally, Pearson’s correlation analysis between the expression of FCER1G and DKD renal function revealed that the abnormal upregulation of FCER1G was related to diabetic glomerular lesions.

Conclusions

Our study demonstrated for the first time that FCER1G is a crucial gene associated with the pathogenesis of DKD.

Epigenetic alterations in skin homing CD4+CLA+ T cells of atopic dermatitis patients

T cells expressing the cutaneous lymphocyte antigen (CLA) mediate pathogenic inflammation in atopic dermatitis (AD). The molecular alterations contributing to their dysregulation remain unclear. With the aim to elucidate putative altered pathways in AD we profiled DNA methylation levels and miRNA expression in sorted T cell populations (CD4⁺, CD4⁺CD45RA⁺ naïve, CD4⁺CLA⁺, and CD8⁺) from adult AD patients and healthy controls (HC). Skin homing CD4⁺CLA⁺ T cells from AD patients showed significant differences in DNA methylation in 40 genes compared to HC (p < 0.05). Reduced DNA methylation levels in the upstream region of the interleukin-13 gene (IL13) in CD4⁺CLA⁺ T cells from AD patients correlated with increased IL13 mRNA expression in these cells. Sixteen miRNAs showed differential expression in CD4⁺CLA⁺ T cells from AD patients targeting genes in 202 biological processes (p < 0.05). An integrated network analysis of miRNAs and CpG sites identified two communities of strongly interconnected regulatory elements with strong antagonistic behaviours that recapitulated the differences between AD patients and HC. Functional analysis of the genes linked to these communities revealed their association with key cytokine signaling pathways, MAP kinase signaling and protein ubiquitination. Our findings support that epigenetic mechanisms play a role in the pathogenesis of AD by affecting inflammatory signaling molecules in skin homing CD4⁺CLA⁺ T cells and uncover putative molecules participating in AD pathways.

Genetic and Epigenetic Aspects of Atopic Dermatitis

Atopic dermatitis is a heterogeneous disease, in which the pathogenesis is associated with mutations in genes encoding epidermal structural proteins, barrier enzymes, and their inhibitors; the role of genes regulating innate and adaptive immune responses and environmental factors inducing the disease is also noted. Recent studies point to the key role of epigenetic changes in the development of the disease. Epigenetic modifications are mainly mediated by DNA methylation, histone acetylation, and the action of specific non-coding RNAs. It has been documented that the profile of epigenetic changes in patients with atopic dermatitis (AD) differs from that observed in healthy people. This applies to the genes affecting the regulation of immune response and inflammatory processes, e.g., both affecting Th1 bias and promoting Th2 responses and the genes of innate immunity, as well as those encoding the structural proteins of the epidermis. Understanding of the epigenetic alterations is therefore pivotal to both create new molecular classifications of atopic dermatitis and to enable the development of personalized treatment strategies.

The Role of Genetics, the Environment, and Epigenetics in Atopic Dermatitis

Atopic Dermatitis (AD) is a common inflammatory disease with a genetic background. The prevalence of AD has been increasing in many countries. AD patients often have manifestations of pruritus, generalized skin dryness, and eczematous lesions. The pathogenesis of AD is complicated. The impaired skin barrier and immune imbalance play significant roles in the development of AD. Environmental factors such as allergens and pollutants are associated with the increasing prevalence. Many genetic and environmental factors induce a skin barrier deficiency, and this can lead to immune imbalance, which exacerbates the impaired skin barrier to form a vicious cycle (outside-inside-outside view). Genetic studies find many gene mutations and genetic variants, such as filaggrin mutations, which may directly induce the deficiency of the skin barrier and immune system. Epigenetic studies provide a connection between the relationship of an impaired skin barrier and immune and environmental factors, such as tobacco exposure, pollutants, microbes, and diet and nutrients. AD is a multigene disease, and thus there are many targets for regulation of expression of these genes which may contribute to the pathogenesis of AD. However, the epigenetic regulation of environmental factors in AD pathogenesis still needs to be further researched.

Genetics and epigenetics of allergy

PURPOSE OF REVIEW

Allergic diseases are prototypic examples for gene × environment-wide interactions. This review considers the current evidence for genetic and epigenetic mechanisms in allergic diseases and highlights barriers and facilitators for the implementation of these novel tools both for research and clinical practice.

RECENT FINDINGS

The value of whole-genome sequencing studies and the use of polygenic risk score analysis in homogeneous well characterized populations are currently being tested. Epigenetic mechanisms are known to play a crucial role in the pathogenesis of allergic disorders, especially through mediating the effects of the environmental factors, well recognized risk modifiers. There is emerging evidence for the immune-modulatory role of probiotics through epigenetic changes. Direct or indirect targeting of epigenetic mechanisms affect expression of the genes favouring the development of allergic diseases and can improve tissue biology. The ability to specifically edit the epigenome, especially using the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)/Cas9 technology, holds the promise of enhancing understanding of how epigenetic modifications function and enabling manipulation of cell phenotype for research or therapeutic purposes.

SUMMARY

Additional research in the role of genetic and epigenetic mechanisms in relation to allergic diseases' endotypes is needed. An international project characterizing the human epigenome in relation to allergic diseases is warranted.

Replicated methylation changes associated with eczema herpeticum and allergic response

Background

Although epigenetic mechanisms are important risk factors for allergic disease, few studies have evaluated DNA methylation differences associated with atopic dermatitis (AD), and none has focused on AD with eczema herpeticum (ADEH+). We will determine how methylation varies in AD individuals with/without EH and associated traits. We modeled differences in genome-wide DNA methylation in whole blood cells from 90 ADEH+, 83 ADEH−, and 84 non-atopic, healthy control subjects, replicating in 36 ADEH+, 53 ADEH−, and 55 non-atopic healthy control subjects. We adjusted for cell-type composition in our models and used genome-wide and candidate-gene approaches.

Results

We replicated one CpG which was significantly differentially methylated by severity, with suggestive replication at four others showing differential methylation by phenotype or severity. Not adjusting for eosinophil content, we identified 490 significantly differentially methylated CpGs (ADEH+ vs healthy controls, genome-wide). Many of these associated with severity measures, especially eosinophil count (431/490 sites).

Conclusions

We identified a CpG in IL4 associated with serum tIgE levels, supporting a role for Th2 immune mediating mechanisms in AD. Changes in eosinophil level, a measure of disease severity, are associated with methylation changes, providing a potential mechanism for phenotypic changes in immune response-related traits.

Electronic supplementary material

The online version of this article (10.1186/s13148-019-0714-1) contains supplementary material, which is available to authorized users.

Thymic stromal lymphopoietin epigenetically upregulates Fc receptor γ subunit-related receptors on antigen-presenting cells and induces TH2/TH17 polarization through dectin-2

BACKGROUND

Fc receptor γ subunit (FcRγ)-related receptors expressed on antigen-presenting cells (APCs) enhance allergen sensitization and allergic inflammation. DNA demethylation of the high-affinity IgE receptor γ subunit gene (FCER1G) leads to FcRγ and FcεRI overexpression on monocytes from patients with atopic dermatitis.

OBJECTIVE

We investigated epigenetic mechanisms underlying FCER1G demethylation and upregulation of FcRγ-related receptors on APCs and the consequent effect on allergic responses.

METHODS

Effects of thymic stromal lymphopoietin (TSLP) on expression of FcRγ and its related receptors and methylation or hydroxymethylation of FCER1G in human monocytes were assessed. Recruitment of ten-eleven translocation protein (TET) 2 to FCER1G by TSLP-activated phosphorylated signal transducer and activator of transcription 5 (pSTAT5) was evaluated. Effects of TSLP on expression of FcRγ-related receptors and costimulatory receptors on monocyte-derived dendritic cells (DCs) and the ability of DCs to take up ovalbumin were analyzed. TSLP-induced T_H polarization and related cytokine production were also analyzed.

RESULTS

pSTAT5 activation by TSLP resulted in TET2 recruitment to FCER1G, leading to FCER1G demethylation and subsequent upregulation of FcRγ-related receptors on monocytes. TSLP not only stimulated monocyte-derived DC maturation but also maintained their allergen uptake ability, likely through maintenance and upregulation of FcRγ-related receptors. Allergen sensitization and upregulation of T_H2/T_H17-related cytokines contributed to TSLP-DC-induced T_H2/T_H17 polarization. The latter was attenuated on neutralization with a dectin-2 antibody.

CONCLUSIONS

TSLP mediated upregulation of FcRγ-related receptors on APCs through activation of pSTAT5, which recruited TET2 to induce FCER1G demethylation. TSLP-induced allergic T_H2/T_H17 polarization likely depends on dectin-2-mediated allergen sensitization and upregulation of T_H2/T_H17-related cytokines.

Leveraging Multilayered "Omics" Data for Atopic Dermatitis: A Road Map to Precision Medicine

Atopic dermatitis (AD) is a complex multifactorial inflammatory skin disease that affects ~280 million people worldwide. About 85% of AD cases begin in childhood, a significant portion of which can persist into adulthood. Moreover, a typical progression of children with AD to food allergy, asthma or allergic rhinitis has been reported (“allergic march” or “atopic march”). AD comprises highly heterogeneous sub-phenotypes/endotypes resulting from complex interplay between intrinsic and extrinsic factors, such as environmental stimuli, and genetic factors regulating cutaneous functions (impaired barrier function, epidermal lipid, and protease abnormalities), immune functions and the microbiome. Though the roles of high-throughput “omics” integrations in defining endotypes are recognized, current analyses are primarily based on individual omics data and using binary clinical outcomes. Although individual omics analysis, such as genome-wide association studies (GWAS), can effectively map variants correlated with AD, the majority of the heritability and the functional relevance of discovered variants are not explained or known by the identified variants. The limited success of singular approaches underscores the need for holistic and integrated approaches to investigate complex phenotypes using trans-omics data integration strategies. Integrating omics layers (e.g., genome, epigenome, transcriptome, proteome, metabolome, lipidome, exposome, microbiome), which often have complementary and synergistic effects, might provide the opportunity to capture the flow of information underlying AD disease manifestation. Overlapping genes/candidates derived from multiple omics types include FLG, SPINK5, S100A8, and SERPINB3 in AD pathogenesis. Overlapping pathways include macrophage, endothelial cell and fibroblast activation pathways, in addition to well-known Th1/Th2 and NFkB activation pathways. Interestingly, there was more multi-omics overlap at the pathway level than gene level. Further analysis of multi-omics overlap at the tissue level showed that among 30 tissue types from the GTEx database, skin and esophagus were significantly enriched, indicating the biological interconnection between AD and food allergy. The present work explores multi-omics integration and provides new biological insights to better define the biological basis of AD etiology and confirm previously reported AD genes/pathways. In this context, we also discuss opportunities and challenges introduced by “big omics data” and their integration.

Distinct human circulating NKp30+FcεRIγ+CD8+ T cell population exhibiting high natural killer-like antitumor potential

CD8⁺ T cells are considered prototypical cells of adaptive immunity. Here, we uncovered a distinct CD8⁺ T cell population expressing the activating natural killer (NK) receptor NKp30 in the peripheral blood of healthy individuals. We revealed that IL-15 could de novo induce NKp30 expression in a population of CD8⁺ T cells and drive their differentiation toward a broad innate transcriptional landscape. The adaptor FcεRIγ was concomitantly induced and was shown to be crucial to enable NKp30 cell-surface expression and function in CD8⁺ T cells. FcεRIγ de novo expression required promoter demethylation and was accompanied by acquisition of the signaling molecule Syk and the "innate" transcription factor PLZF. IL-15-induced NKp30⁺CD8⁺ T cells exhibited high NK-like antitumor activity in vitro and were able to synergize with T cell receptor signaling. Importantly, this population potently controlled tumor growth in a preclinical xenograft mouse model. Our study, while blurring the borders between innate and adaptive immunity, reveals a unique NKp30⁺FcεRIγ⁺CD8⁺ T cell population with high antitumor therapeutic potential.

Screening of candidate key genes associated with human osteosarcoma using bioinformatics analysis

The aim of the present study was to identify the key genes associated with osteosarcoma (OS) using a bioinformatics approach. Microarray data (GSE36004) was downloaded from the Gene Expression Omnibus database, including 19 OS cell lines and 6 normal controls. Differentially expressed genes (DEGs) in the OS cell lines were identified using the Limma package, and differentially methylated regions were screened with methyAnalysis in R. Copy number analysis was performed and genes with copy number gains/losses were further screened using DNAcopy and cghMCR packages. Functional enrichment analyses were performed using the Database for Annotation, Visualization and Integrated Discovery online tool, and protein-protein interactions were identified based on information obtained from the Search Tool for the Retrieval of Interacting Genes database. A total of 47 downregulated genes were screened in hyper-methylated regions, including the fragment crystallizable (Fc) region of immunoglobulin E, high affinity I, receptor for; γ polypeptide (FCER1G), leptin (LEP) and feline Gardner-Rasheed sarcoma viral oncogene homolog (FGR). In addition, a total of 17 upregulated genes, including the TPase family, AAA domain containing 2 (ATAD2) and cyclin-dependent kinase 4 (CDK4), exhibited copy number gains, while 5 downregulated genes, including Rho GTPase activating protein 9 (ARHGAP9) and major histocompatibility complex, class II, DO α (HLA-DOA), exhibited copy number losses. These results indicate that hyper-methylation of FCER1G, LEP, and FGR may serve a crucial function in the development of OS. In addition, copy number alterations of these DEGs, including ATAD2, CDK4, ARHGAP9 and HLA-DOA, may also contribute to OS progression. These DEGs may be candidate targets for the diagnosis and treatment of this disease.

Epigenetics and allergy: from basic mechanisms to clinical applications

Allergic diseases are on the rise in the Western world and well-known allergy-protecting and -driving factors such as microbial and dietary exposure, pollution and smoking mediate their influence through alterations of the epigenetic landscape. Here, we review key facts on the involvement of epigenetic modifications in allergic diseases and summarize and critically evaluate the lessons learned from epigenome-wide association studies. We show the potential of epigenetic changes for various clinical applications: as diagnostic tools, to assess tolerance following immunotherapy or possibly predict the success of therapy at an early time point. Furthermore, new technological advances such as epigenome editing and DNAzymes will allow targeted alterations of the epigenome in the future and provide novel therapeutic tools.

The Genetics and Epigenetics of Atopic Dermatitis-Filaggrin and Other Polymorphisms

Atopic dermatitis (AD) is a chronic inflammatory skin disease caused by a combination of genetic and environmental factors. Genetic evidences depict a complex network comprising by epidermal barrier dysfunctions and dysregulation of innate and adaptive immunity in the pathogenesis of AD. Mutations in the human filaggrin gene (FLG) are the most significant and well-replicated genetic mutation associated with AD, and other mutations associated with epidermal barriers such as SPINK5, FLG-2, SPRR3, and CLDN1 have all been linked to AD. Gene variants may also contribute to the abnormal innate and adaptive responses found in AD, including mutations in PRRs and AMPs, TSLP and TSLPR, IL-1 family cytokines and receptors genes, vitamin D pathway genes, FCER1A, and Th2 and other cytokines genes. GWAS and Immunochip analysis have identified a total of 19 susceptibility loci for AD. Candidate genes at these susceptibility loci identified by GWAS and Immunochip analysis also suggest roles for epidermal barrier functions, innate and adaptive immunity, interleukin-1 family signaling, regulatory T cells, the vitamin D pathway, and the nerve growth factor pathway in the pathogenesis of AD. Increasing evidences show the modern lifestyle (i.e., the hygiene hypothesis, Western diet) and other environmental factors such as pollution and environmental tobacco smoke (ETS) lead to the increasing prevalence of AD with the development of industrialization. Epigenetic alterations in response to these environmental factors, including DNA methylation and microRNA related to immune system and skin barriers, have been found to contribute to the pathogenesis of AD. Genetic variants and epigenetic alteration might be the key tools for the molecular taxonomy of AD and provide the background for the personalized management.

Genetic and epigenetic studies of atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a chronic inflammatory disease caused by the complex interaction of genetic, immune and environmental factors. There have many recent discoveries involving the genetic and epigenetic studies of AD.

METHODS

A retrospective PubMed search was carried out from June 2009 to June 2016 using the terms "atopic dermatitis", "association", "eczema", "gene", "polymorphism", "mutation", "variant", "genome wide association study", "microarray" "gene profiling", "RNA sequencing", "epigenetics" and "microRNA". A total of 132 publications in English were identified.

RESULTS

To elucidate the genetic factors for AD pathogenesis, candidate gene association studies, genome-wide association studies (GWAS) and transcriptomic profiling assays have been performed in this period. Epigenetic mechanisms for AD development, including genomic DNA modification and microRNA posttranscriptional regulation, have been explored. To date, candidate gene association studies indicate that filaggrin (FLG) null gene mutations are the most significant known risk factor for AD, and genes in the type 2 T helper lymphocyte (Th2) signaling pathways are the second replicated genetic risk factor for AD. GWAS studies identified 34 risk loci for AD, these loci also suggest that genes in immune responses and epidermal skin barrier functions are associated with AD. Additionally, gene profiling assays demonstrated AD is associated with decreased gene expression of epidermal differentiation complex genes and elevated Th2 and Th17 genes. Hypomethylation of TSLP and FCER1G in AD were reported; and miR-155, which target the immune suppressor CTLA-4, was found to be significantly over-expressed in infiltrating T cells in AD skin lesions.

CONCLUSIONS

The results suggest that two major biologic pathways are responsible for AD etiology: skin epithelial function and innate/adaptive immune responses. The dysfunctional epidermal barrier and immune responses reciprocally affect each other, and thereby drive development of AD.

Molecular Mechanisms of Cutaneous Inflammatory Disorder: Atopic Dermatitis

Atopic dermatitis (AD) is a multifactorial inflammatory skin disease resulting from interactions between genetic susceptibility and environmental factors. The pathogenesis of AD is poorly understood, and the treatment of recalcitrant AD is still challenging. There is accumulating evidence for new gene polymorphisms related to the epidermal barrier function and innate and adaptive immunity in patients with AD. Newly-found T cells and dendritic cell subsets, cytokines, chemokines and signaling pathways have extended our understanding of the molecular pathomechanism underlying AD. Genetic changes caused by environmental factors have been shown to contribute to the pathogenesis of AD. We herein present a review of the genetics, epigenetics, barrier dysfunction and immunological abnormalities in AD with a focus on updated molecular biology.

Evolving insights on how cytosine methylation affects protein-DNA binding

Many anecdotal observations exist of a regulatory effect of DNA methylation on gene expression. However, in general, the underlying mechanisms of this effect are poorly understood. In this review, we summarize what is currently known about how this important, but mysterious, epigenetic mark impacts cellular functions. Cytosine methylation can abrogate or enhance interactions with DNA-binding proteins, or it may have no effect, depending on the context. Despite being only a small chemical change, the addition of a methyl group to cytosine can affect base readout via hydrophobic contacts in the major groove and shape readout via electrostatic contacts in the minor groove. We discuss the recent discovery that CpG methylation increases DNase I cleavage at adjacent positions by an order of magnitude through altering the local 3D DNA shape and the possible implications of this structural insight for understanding the methylation sensitivity of transcription factors (TFs). Additionally, 5-methylcytosines change the stability of nucleosomes and, thus, affect the local chromatin structure and access of TFs to genomic DNA. Given these complexities, it seems unlikely that the influence of DNA methylation on protein-DNA binding can be captured in a small set of general rules. Hence, data-driven approaches may be essential to gain a better understanding of these mechanisms.

Systems biology of asthma and allergic diseases: a multiscale approach

Systems biology is an approach to understanding living systems that focuses on modeling diverse types of high-dimensional interactions to develop a more comprehensive understanding of complex phenotypes manifested by the system. High-throughput molecular, cellular, and physiologic profiling of populations is coupled with bioinformatic and computational techniques to identify new functional roles for genes, regulatory elements, and metabolites in the context of the molecular networks that define biological processes associated with system physiology. Given the complexity and heterogeneity of asthma and allergic diseases, a systems biology approach is attractive, as it has the potential to model the myriad connections and interdependencies between genetic predisposition, environmental perturbations, regulatory intermediaries, and molecular sequelae that ultimately lead to diverse disease phenotypes and treatment responses across individuals. The increasing availability of high-throughput technologies has enabled system-wide profiling of the genome, transcriptome, epigenome, microbiome, and metabolome, providing fodder for systems biology approaches to examine asthma and allergy at a more holistic level. In this article we review the technologies and approaches for system-wide profiling, as well as their more recent applications to asthma and allergy. We discuss approaches for integrating multiscale data through network analyses and provide perspective on how individually captured health profiles will contribute to more accurate systems biology views of asthma and allergy.

Molecular biology of atopic dermatitis

Atopic dermatitis (AD) is a chronic inflammatory skin disease with specific genetic and immunological mechanisms. The rapid development of new techniques in molecular biology had ushered in new discoveries on the role of cytokines, chemokines, and immune cells in the pathogenesis of AD. New polymorphisms of AD are continually being reported in different populations. The physical and immunological barrier of normal intact skin is an important part of the innate immune system that protects the host against microbials and allergens that are associated with AD. Defects in the filaggrin gene FLG may play a role in facilitating exposure to allergens and microbial pathogens, which may induce Th2 polarization. Meanwhile, Th22 cells also play roles in skin barrier impairment through IL-22, and AD is often considered to be a Th2/Th22-dominant allergic disease. Mast cells and eosinophils are also involved in the inflammation via Th2 cytokines. Release of pruritogenic substances by mast cells induces scratching that further disrupts the skin barrier. Th1 and Th17 cells are mainly involved in chronic phase of AD. Keratinocytes also produce proinflammatory cytokines such as thymic stromal lymphopoietin (TSLP), which can further affect Th cells balance. The immunological characteristics of AD may differ for various endotypes and phenotypes. Due to the heterogeneity of the disease, and the redundancies of these mechanisms, our knowledge of the pathophysiology of the disease is still incomplete, which is reflected by the absence of a cure for the disease.

Promoter demethylation contributes to TSLP overexpression in skin lesions of patients with atopic dermatitis

BACKGROUND

Thymic stromal lymphopoietin (TSLP) plays an important role in promoting T-cell homeostasis, and appears to be a central player in the development of allergic symptoms, especially in asthma and atopic dermatitis (AD). Human TSLP is overexpressed in keratinocytes of patients with acute and chronic AD. However, the mechanism of TSLP overexpression remains unclear.

AIM

To investigate whether TSLP expression is regulated by aberrant DNA methylation modification of the TSLP promoter in keratinocytes of patients with AD.

METHODS

mRNA and protein levels of TSLP in lesional skin samples from 10 children with AD and 10 healthy controls were measured by real-time quantitative reverse transcriptase-PCR and immunohistochemistry. Bisulfite sequencing was performed to determine the methylation status of the TSLP promoter, and 5-azacytidine (5-aza), a DNA methyltransferase inhibitor, was used to determine the influence of DNA methylation on TSLP expression.

RESULTS

TSLP mRNA and protein expression levels were increased in skin lesions from patients with AD compared with healthy controls. Moreover, promoter hypomethylation of the TSLP gene was identified in skin lesions from patients with AD, and treating keratinocytes with 5-aza reduced the methylation level of the TSLP promoter and increased TSLP transcription.

CONCLUSIONS

DNA demethylation of a specific regulatory region of the TSLP gene may contribute to TSLP overexpression in skin lesions in patients with AD.

Epigenetics and development of food allergy (FA) in early childhood

This review aims to highlight the latest advance on epigenetics in the development of food allergy (FA) and to offer future perspectives. FA, a condition caused by an immunoglobulin (Ig) E-mediated hypersensitivity reaction to food, has emerged as a major clinical and public health problem worldwide in light of its increasing prevalence, potential fatality, and significant medical and economic impact. Current evidence supports that epigenetic mechanisms are involved in immune regulation and that the epigenome may represent a key "missing piece" of the etiological puzzle for FA. There are a growing number of population-based epigenetic studies on allergy-related phenotypes, mostly focused on DNA methylation. Previous studies mostly applied candidate-gene approaches and have demonstrated that epigenetic marks are associated with multiple allergic diseases and/or with early-life exposures relevant to allergy development (such as early-life smoking exposure, air pollution, farming environment, and dietary fat). Rapid technological advancements have made unbiased genome-wide DNA methylation studies highly feasible, although there are substantial challenge in study design, data analyses, and interpretation of findings. In conclusion, epigenetics represents both an important knowledge gap and a promising research area for FA. Due to the early onset of FA, epigenetic studies of FA in prospective birth cohorts have the potential to better understand gene-environment interactions and underlying biological mechanisms in FA during critical developmental windows (preconception, in utero, and early childhood) and may lead to new paradigms in the diagnosis, prevention, and management of FA and provide novel targets for future drug discovery and therapies for FA.

Characteristic DNA methylation profiles in peripheral blood monocytes are associated with inflammatory phenotypes of asthma

Epigenetic changes including DNA methylation caused by environmental exposures may contribute to the heterogeneous inflammatory response in asthma. Here we investigate alterations in DNA methylation of purified blood monocytes that are associated with inflammatory phenotypes of asthma. Peripheral blood was collected from adults with eosinophilic asthma (EA; n = 21), paucigranulocytic asthma (PGA; n = 22), neutrophilic asthma (NA; n = 9), and healthy controls (n = 10). Blood monocytes were isolated using ficoll density gradient and immuno-magnetic cell separation. Bisulfite converted genomic DNA was hybridized to Illumina Infinium Methylation27 arrays and analyzed for differential methylation using R/Bioconductor packages; networks of gene interactions were identified using the STRING database. Compared with healthy controls, differentially methylated CpG loci were identified in EA (n = 413), PGA (n = 495), and NA (n = 89). We found that 223, 237, and 72 loci were significantly hypermethylated in EA, PGA, and NA, respectively. Nine genes were common to all three phenotypes and showed increased methylation in asthma. Three pathway networks were identified in EA, involved in purine metabolism, calcium signaling, and ECM-receptor interaction. In PGA, two networks were identified, involved in neuroactive ligand-receptor interaction and ubiquitin mediated proteolysis. In NA, one network was identified involving sFRP1 as a key node, over representing the Wnt signaling pathway. We have identified characteristic alterations in DNA methylation that are associated with inflammatory phenotypes of asthma and may contribute to the disease mechanisms. This network-based characterization may help in the development of epigenetic biomarkers and therapeutic targets for asthma.

Myogenic differential methylation: diverse associations with chromatin structure

Employing a new algorithm for identifying differentially methylated regions (DMRs) from reduced representation bisulfite sequencing profiles, we identified 1972 hypermethylated and 3250 hypomethylated myogenic DMRs in a comparison of myoblasts (Mb) and myotubes (Mt) with 16 types of nonmuscle cell cultures. DMRs co-localized with a variety of chromatin structures, as deduced from ENCODE whole-genome profiles. Myogenic hypomethylation was highly associated with both weak and strong enhancer-type chromatin, while hypermethylation was infrequently associated with enhancer-type chromatin. Both myogenic hypermethylation and hypomethylation often overlapped weak transcription-type chromatin and Polycomb-repressed-type chromatin. For representative genes, we illustrate relationships between DNA methylation, the local chromatin state, DNaseI hypersensitivity, and gene expression. For example, MARVELD2 exhibited myogenic hypermethylation in transcription-type chromatin that overlapped a silenced promoter in Mb and Mt while TEAD4 had myogenic hypomethylation in intronic subregions displaying enhancer-type or transcription-type chromatin in these cells. For LSP1, alternative promoter usage and active promoter-type chromatin were linked to highly specific myogenic or lymphogenic hypomethylated DMRs. Lastly, despite its myogenesis-associated expression, TBX15 had multiple hypermethylated myogenic DMRs framing its promoter region. This could help explain why TBX15 was previously reported to be underexpressed and, unexpectedly, its promoter undermethylated in placentas exhibiting vascular intrauterine growth restriction.