Vincent D. Gaertner

Polymorphisms related to ORMDL3 are associated with asthma susceptibility, alterations in transcriptional regulation of ORMDL3, and changes in TH2 cytokine levels.

BACKGROUND Chromosome 17q21, harboring the orosomucoid 1-like 3 (ORMDL3) gene, has been consistently associated with childhood asthma in genome-wide association studies. OBJECTIVE We investigated genetic variants in and around ORMDL3 that can change the function of ORMDL3 and thus contribute to asthma susceptibility. METHODS We performed haplotype analyses and fine mapping of the ORMDL3 locus in a cross-sectional (International Study of Asthma and Allergies in Childhood Phase II, n = 3557 total subjects, n = 281 asthmatic patients) and case-control (Multicenter Asthma Genetics in Childhood Study/International Study of Asthma and Allergies in Childhood Phase II, n = 1446 total subjects, n = 763 asthmatic patients) data set to identify putative causal single nucleotide polymorphisms (SNPs) in the locus. Top asthma-associated polymorphisms were analyzed for allele-specific effects on transcription factor binding and promoter activity in vitro and gene expression in PBMCs after stimulation ex vivo. RESULTS Two haplotypes (H1 and H2) were significantly associated with asthma in the cross-sectional (P = 9.9 × 10(-5) and P = .0035, respectively) and case-control (P = 3.15 × 10(-8) and P = .0021, respectively) populations. Polymorphisms rs8076131 and rs4065275 were identified to drive these effects. For rs4065275, a quantitative difference in transcription factor binding was found, whereas for rs8076131, changes in upstream stimulatory factor 1 and 2 transcription factor binding were observed in vitro by using different cell lines and PBMCs. This might contribute to detected alterations in luciferase activity paralleled with changes in ORMDL3 gene expression and IL-4 and IL-13 cytokine levels ex vivo in response to innate and adaptive stimuli in an allele-specific manner. Both SNPs were in strong linkage disequilibrium with asthma-associated 17q21 SNPs previously related to altered ORMDL3 gene expression. CONCLUSION Polymorphisms in a putative promoter region of ORMDL3, which are associated with childhood asthma, alter transcriptional regulation of ORMDL3, correlate with changes in TH2 cytokines levels, and therefore might contribute to the childhood asthma susceptibility signal from 17q21.

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.

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.

The cAMP response element modulator (CREM) regulates T H 2 mediated inflammation

A characteristic feature of allergic diseases is the appearance of a subset of CD4+ cells known as TH2 cells, which is controlled by transcriptional and epigenetic mechanisms. We aimed to analyze the role of CREM, a known transcriptional activator of T cells, with regard to TH2 responses and allergic diseases in men and mice. Here we demonstrate that T cells of asthmatic children and PBMCs of adults with atopy express lower mRNA levels of the transcription factor CREM compared to cells from healthy controls. CREM deficiency in murine T cells results in enhanced TH2 effector cytokines in vitro and in vivo and CREM−/− mice demonstrate stronger airway hyperresponsiveness in an OVA-induced asthma model. Mechanistically, both direct CREM binding to the IL-4 and IL-13 promoter as well as a decreased IL-2 dependent STAT5 activation suppress the TH2 response. Accordingly, mice selectively overexpressing CREMα in T cells display decreased TH2 type cytokines in vivo and in vitro, and are protected in an asthma model. Thus, we provide evidence that CREM is a negative regulator of the TH2 response and determines the outcome of allergic asthma.

6q12 and 11p14 variants are associated with postnatal exhaled nitric oxide levels and respiratory symptoms

Background: Exhaled nitric oxide (eNO) is a biomarker of airway inflammation and seems to precede respiratory symptoms, such as asthma, in childhood. Identifying genetic determinants of postnatal eNO levels might aid in unraveling the role of eNO in epithelial function or airway inflammation and disease. Objective: We sought to identify genetic determinants of early postnatal eNO levels and subsequent respiratory symptoms during the first year of life. Methods: Within a population‐based birth cohort, eNO levels were measured in healthy term infants aged 5 weeks during quiet tidal breathing in unsedated sleep. We assessed associations of single nucleotide polymorphisms with eNO levels in a genome‐wide association study and subsequent symptoms of lower respiratory tract infections during the first year of life and asked whether this was modified by prenatal and early‐life environmental factors. Results: We identified thus far unknown determinants of infant eNO levels: rs208515 (P = 3.3 × 10−8), which is located at 6q12, probably acting in “trans” and explaining 10.3% of eNO level variance, and rs1441519 (P = 1.6 × 10−6), which is located at 11p14, potentially affecting nitric oxide synthase 3 (NOS3) expression, as shown by means of in vitro functional analyses. Moreover, the 6q12 locus was inversely associated with subsequent respiratory symptoms (P < .05) and time to recovery after first respiratory symptoms during the first year of life (P < .05). Conclusion: The identification of novel genetic determinants of infant eNO levels might implicate that postnatal eNO metabolism in healthy infants before first viral infections and sensitization is related to mechanisms other than those associated with asthma, atopy, or increased risk thereof later in life.

Neuropeptide S (NPS) variants modify the signaling and risk effects of NPS Receptor 1 (NPSR1) variants in asthma

Single nucleotide polymorphisms (SNPs) close to the gain-of-function substitution, Asn(107)Ile (rs324981, A>T), in Neuropeptide S Receptor 1 (NPSR1) have been associated with asthma. Furthermore, a functional SNP (rs4751440, G>C) in Neuropeptide S (NPS) encodes a Val(6)Leu substitution on the mature peptide that results in reduced bioactivity. We sought to examine the effects of different combinations of these NPS and NPSR1 variants on downstream signaling and genetic risk of asthma. In transfected cells, the magnitude of NPSR1-induced activation of cAMP/PKA signal transduction pathways and downstream gene expression was dependent on the combination of the NPS and NPSR1 variants with NPS-Val(6)/NPSR1-Ile(107) resulting in strongest and NPS-Leu(6)/NPSR1-Asn(107) in weakest effects, respectively. One or two copies of the NPS-Leu(6) (rs4751440) were associated with physician-diagnosed childhood asthma (OR: 0.67, 95%CI 0.49–0.92, p = 0.01) and together with two other linked NPS variants (rs1931704 and rs10830123) formed a protective haplotype (p = 0.008) in the Swedish birth cohort BAMSE (2033 children). NPS rs10830123 showed epistasis with NPSR1 rs324981 encoding Asn(107)Ile (p = 0.009) in BAMSE and with the linked NPSR1 rs17199659 (p = 0.005) in the German MAGIC/ISAAC II cohort (1454 children). In conclusion, NPS variants modify asthma risk and should be considered in genetic association studies of NPSR1 with asthma and other complex diseases.

Asthma- and IgE-associated polymorphisms affect expression of TH17 genes

TH 17 cells contribute to the pathogenesis of chronic inflammatory diseases such as asthma and TH 17 pathway tagging SNPs were associated with asthma and total serum IgE levels in childhood. In this study genotype-specific effects of these SNPs on the expression of TH 17 related molecules were analyzed in peripheral blood mononuclear cells (PBMCs) before and after allergen stimulation in 61 individuals. After correction for multiple testing, protein or mRNA expression levels of several molecules, including IL-17A, IL17-F, IL-23 and IL-23 receptor, were significantly correlated with asthma-associated SNPs (located in IL17F, IL22, IL23R and IL23A) and IgE-associated polymorphisms (located in IL17A and three SNPs in IL12B). Most extensive effects on TH 17 pathway expression were observed for the asthma-associated polymorphism IL17F rs7741835. In conclusion, genetic variants in IL17F and, to a smaller degree, IL17A and IL-23 signaling genes associated with asthma and IgE levels seem functional in influencing expression of TH 17 related molecules, indicating a contribution of these mechanisms to genetic susceptibility towards asthma and atopy. This article is protected by copyright. All rights reserved.