Daniel P. Potaczek

Current concepts of IgE regulation and impact of genetic determinants

Immunoglobulin E (IgE) mediated immune responses seem to be directed against parasites and neoplasms, but are best known for their involvement in allergies. The IgE network is tightly controlled at different levels as outlined in this review. Genetic determinants were suspected to influence IgE regulation and IgE levels considerably for many years. Linkage and candidate gene studies suggested a number of loci and genes to correlate with total serum IgE levels, and recently genome‐wide association studies (GWAS) provided the power to identify genetic determinants for total serum IgE levels: 1q23 (FCER1A), 5q31 (RAD50, IL13, IL4), 12q13 (STAT6), 6p21.3 (HLA‐DRB1) and 16p12 (IL4R, IL21R). In this review, we analyse the potential role of these GWAS hits in the IgE network and suggest mechanisms of how genes and genetic variants in these loci may influence IgE regulation.

Links between allergy and cardiovascular or hemostatic system

In addition to a well-known immunologic background of atherosclerosis and influences of inflammation on arterial and venous thrombosis, there is growing evidence for the presence of links between allergy and vascular or thrombotic disorders. In this interpretative review, five pretty well-documented areas of such overlap are described and discussed, including: (1) links between atherosclerosis and immunoglobulin E or atopy, (2) mutual effects of blood lipids and allergy, (3) influence of atopy and related disorders on venous thromboembolism, (4) the role of platelets in allergic diseases, and (5) the functions of protein C system in atopic disorders.

Different FCER1A polymorphisms influence IgE levels in asthmatics and non-asthmatics.

Recently, three genome‐wide association studies (GWAS) demonstrated FCER1A, the gene encoding a ligand‐binding subunit of the high‐affinity IgE receptor, to be a major susceptibility locus for serum IgE levels. The top association signal differed between the two studies from the general population and the one based on an asthma case–control design. In this study, we investigated whether different FCER1A polymorphisms are associated with total serum IgE in the general population and asthmatics specifically.

A polymorphism in the TH2 locus control region is associated with changes in DNA methylation and gene expression

Genomewide association and epigenetic studies found a region within the RAD50 gene on chromosome 5q31 to be associated with total serum IgE levels and asthma. In mice, this region harbors a locus control region for nearby TH2 cytokines, which is characterized by four Rad50 DNase I hypersensitive sites (RHS4–7). Among these, RHS7 seems to have the strongest impact on TH2 differentiation. We investigated whether within the human homolog of RHS7, functional polymorphisms exist, which could affect DNA methylation or gene expression in the 5q31 locus and might have an influence on asthma status or IgE regulation.

Fine-mapping of IgE-associated loci 1q23, 5q31, and 12q13 using 1000 Genomes Project data

Genome‐wide association studies (GWAS) repeatedly identified 1q23 (FCER1A), 5q31 (RAD50‐IL13 and IL4), and 12q13 (STAT6) as major susceptibility loci influencing the regulation of total serum IgE levels. As GWAS may be insufficient to capture causal variants, we performed fine‐mapping and re‐genotyping of the three loci using 1000 Genomes Project datasets.

Epigenetic Regulation in Early Childhood: A Miniaturized and Validated Method to Assess Histone Acetylation.

Introduction: Chronic inflammatory diseases including allergies and asthma are the result of complex interactions between genes and environmental factors. Epigenetic mechanisms comprise a set of biochemical reactions that regulate gene expression. In order to understand the cause-effect relationship between environmental exposures and disease development, methods capable of assessing epigenetic regulation (also) in large cohorts are needed. Methods: For this purpose, we developed and evaluated a miniaturized chromatin immunoprecipitation (ChIP) assay allowing for a cost-effective assessment of histone acetylation of candidate genes in a quantitative fashion. This method was then applied to assess H3 and H4 histone acetylation changes in cord blood (CB) samples from an established cohort of Australian children exposed in the fetal period to either very low or very high levels of maternal folate. Results: Our ChIP assay was validated for a minimum requirement of 1 × 105 target cells (e.g. CD4+ T cells). Very high levels of maternal folate were significantly associated with increased H3/H4 acetylation at GATA3 and/or IL9 promoter regions in CD4+ T cells in CB. Conclusion: We developed a ChIP method allowing reliable assessment of H3/H4 acetylation using 1 × 105 cells only. Practical application of this assay demonstrated an association between high maternal folate exposure and increased histone acetylation, corresponding to a more transcriptionally permissive chromatin status in the promoter regions of some Th2-related genes.

A role of FCER1A and FCER2 polymorphisms in IgE regulation

Both FCER2 and FCER1A encode subunits of IgE receptors. Variants in FCER1A were previously identified as major determinants of IgE levels in genome‐wide association studies.

Childhood asthma is associated with mutations and gene expression differences of ORMDL genes that can interact.

Genomewide association studies identified ORMDL3 as a plausible asthma candidate gene. ORMDL proteins regulate sphingolipid metabolism and ceramide homeostasis and participate in lymphocyte activation and eosinophil recruitment. Strong sequence homology between the three ORMDL genes and ORMDL protein conservation among different species suggest that they may have shared functions. We hypothesized that if single nucleotide polymorphisms (SNPs) in ORMDL3 alter its gene expression and play a role in asthma, variants in ORMDL1 and ORMDL2 might also be associated with asthma.

PROS1 mutations associated with protein S deficiency in Polish patients with residual vein obstruction on rivaroxaban therapy.

Protein S (PS) is a vitamin K-dependent glycoprotein that acts as a natural anticoagulant. Approximately 60% of PS forms a non-covalent complex with the complement 4b-binding protein (C4BP) while the remaining 40% is free [1]. Both forms of PS, free and complexed with C4BP, serve as cofactors of activated protein C (PC) in the proteolysis of activated factor (F)V and FVIII [2], but free PS is more potent [3,4]. PS also has an ability to stimulate the FXa inactivation by tissue factor pathway inhibitor (TFPI) via the APC-independent mechanism [5]. PS deficiency is an autosomal dominant disorder with a prevalence of less than 0.5% in the general European population and 2% to 12% in patients with deep-vein thrombosis (DVT) or pulmonary embolism (PE) [6]. Based on laboratory findings, PS deficiency is classified as type I (low total and free antigen, reduced activity), type II (normal total and free antigen, reduced activity) and type III (normal total antigen, reduced free antigen and activity) [7]. Approximately 95% of PS-deficient patients develop PS deficiency of type I or III. The protein S gene (PROS1) is located on chromosome 3q11.2 and consists of 15 exons [7]. PS deficiency is most frequently caused by missense/nonsense substitutions followed by splice-site mutations and small/gross duplications, insertions or deletions (HGMD database, http://www.hgmd.org). Here we report two novel PROS1 mutations, duplication and a missense substitution, detected in two families with marked PS-deficiency associated with venous thromboembolism (VTE), whose members showed resistance to anticoagulant effects of rivaroxaban, an orally administered direct FXa inhibitor.

The role of PKCζ in cord blood T-cell maturation towards Th1 cytokine profile and its epigenetic regulation by fish oil

While immunodeficiency of immaturity of the neonate has been considered important as the basis for unusual susceptibility to infection, it has also been recognized that the ability to progress from an immature Th2 cytokine predominance to a Th1 profile has relevance in determining whether children will develop allergy, providing an opportunity for epigenetic regulation through environmental pressures. However, this notion remains relatively unexplored. Here, we present evidence that there are two major control points to explain the immunodeficiency in cord blood (CB) T-cells, a deficiency in interleukin (IL)-12 (IL-12) producing and IL-10 overproducing accessory cells, leading to a decreased interferon γ (IFNγ) synthesis and the other, an intrinsic defect in T-cell protein kinase C (PKC) ζ (PKCζ) expression. An important finding was that human CB T-cells rendered deficient in PKCζ, by shRNA knockdown, develop into low tumour necrosis factor α (TNFα) and IFNγ but increased IL-13 producing cells. Interestingly, we found that the increase in PKCζ levels in CB T-cells caused by prenatal supplementation with fish oil correlated with modifications of histone acetylation at the PKCζ gene (PRKCZ) promoter. The data demonstrate that PKCζ expression regulates the maturation of neonatal T-cells into specific functional phenotypes and that environmental influences may work via PKCζ to regulate these phenotypes and disease susceptibility.