Sven Michel

Variants of DENND1B Associated with Asthma in Children

BACKGROUND Asthma is a complex disease that has genetic and environmental causes. The genetic factors associated with susceptibility to asthma remain largely unknown. METHODS We carried out a genomewide association study involving children with asthma. The sample included 793 North American children of European ancestry with persistent asthma who required daily inhaled glucocorticoid therapy and 1988 matched controls (the discovery set). We also tested for genomewide association in an independent cohort of 917 persons of European ancestry who had asthma and 1546 matched controls (the replication set). Finally, we tested for an association between 20 single-nucleotide polymorphisms (SNPs) at chromosome 1q31 and asthma in 1667 North American children of African ancestry who had asthma and 2045 ancestrally matched controls. RESULTS In our meta-analysis of all samples from persons of European ancestry, we observed an association, with genomewide significance, between asthma and SNPs at the previously reported locus on 17q21 and an additional eight SNPs at a novel locus on 1q31. The SNP most strongly associated with asthma was rs2786098 (P=8.55x10(-9)). We observed replication of the association of asthma with SNP rs2786098 in the independent series of persons of European ancestry (combined P=9.3x10(-11)). The alternative allele of each of the eight SNPs on chromosome 1q31 was strongly associated with asthma in the children of African ancestry (P=1.6x10(-13) for the comparison across all samples). The 1q31 locus contains the 1q31 locus contains DENND1B, a gene expressed by natural killer cells and dendritic cells. DENND1B protein is predicted to interact with the tumor necrosis factor α receptor [corrected]. CONCLUSIONS We have identified a locus containing DENND1B on chromosome 1q31.3 that is associated with susceptibility to asthma.

High-density genotyping study identifies four new susceptibility loci for atopic dermatitis.

Atopic dermatitis is a common inflammatory skin disease with a strong heritable component. Pathogenetic models consider keratinocyte differentiation defects and immune alterations as scaffolds, and recent data indicate a role for autoreactivity in at least a subgroup of patients. FLG (encoding filaggrin) has been identified as a major locus causing skin barrier deficiency. To better define risk variants and identify additional susceptibility loci, we densely genotyped 2,425 German individuals with atopic dermatitis (cases) and 5,449 controls using the Immunochip array followed by replication in 7,196 cases and 15,480 controls from Germany, Ireland, Japan and China. We identified four new susceptibility loci for atopic dermatitis and replicated previous associations. This brings the number of atopic dermatitis risk loci reported in individuals of European ancestry to 11. We estimate that these susceptibility loci together account for 14.4% of the heritability for atopic dermatitis.

Farm exposure and time trends in early childhood may influence DNA methylation in genes related to asthma and allergy

Genetic susceptibility and environmental influences are important contributors to the development of asthma and atopic diseases. Epigenetic mechanisms may facilitate gene by environment interactions in these diseases.

Increased regulatory T-cell numbers are associated with farm milk exposure and lower atopic sensitization and asthma in childhood

BACKGROUND European cross-sectional studies have suggested that prenatal and postnatal farm exposure decreases the risk of allergic diseases in childhood. Underlying immunologic mechanisms are still not understood but might be modulated by immune-regulatory cells early in life, such as regulatory T (Treg) cells. OBJECTIVE We sought to assess whether Treg cells from 4.5-year-old children from the Protection against Allergy: Study in Rural Environments birth cohort study are critical in the atopy and asthma-protective effect of farm exposure and which specific exposures might be relevant. METHODS From 1133 children, 298 children were included in this study (149 farm and 149 reference children). Detailed questionnaires until 4 years of age assessed farming exposures over time. Treg cells were characterized as upper 20% CD4(+)CD25(+) forkhead box protein 3 (FOXP3)(+) (intracellular) in PBMCs before and after stimulation (with phorbol 12-myristate 13-acetate/ionomycin or LPS), and FOXP3 demethylation was assessed. Atopic sensitization was defined by specific IgE measurements; asthma was defined by a doctors diagnosis. RESULTS Treg cells were significantly increased in farm-exposed children after phorbol 12-myristate 13-acetate/ionomycin and LPS stimulation. Exposure to farm milk was defined as a relevant independent farm-related exposure supported by higher FOXP3 demethylation. Treg cell (upper 20% CD4(+)CD25(+), FOXP3(+) T cells) numbers were significantly negatively associated with doctor-diagnosed asthma (LPS stimulated: adjusted odds ratio, 0.26; 95% CI, 0.08-0.88) and perennial IgE (unstimulated: adjusted odds ratio, 0.21; 95% CI, 0.08-0.59). Protection against asthma by farm milk exposure was partially mediated by Treg cells. CONCLUSIONS Farm milk exposure was associated with increased Treg cell numbers on stimulation in 4.5-year-old children and might induce a regulatory phenotype early in life, potentially contributing to a protective effect for the development of childhood allergic diseases.

Unifying Candidate Gene and GWAS Approaches in Asthma

The first genome wide association study (GWAS) for childhood asthma identified a novel major susceptibility locus on chromosome 17q21 harboring the ORMDL3 gene, but the role of previous asthma candidate genes was not specifically analyzed in this GWAS. We systematically identified 89 SNPs in 14 candidate genes previously associated with asthma in >3 independent study populations. We re-genotyped 39 SNPs in these genes not covered by GWAS performed in 703 asthmatics and 658 reference children. Genotyping data were compared to imputation data derived from Illumina HumanHap300 chip genotyping. Results were combined to analyze 566 SNPs covering all 14 candidate gene loci. Genotyped polymorphisms in ADAM33, GSTP1 and VDR showed effects with p-values <0.0035 (corrected for multiple testing). Combining genotyping and imputation, polymorphisms in DPP10, EDN1, IL12B, IL13, IL4, IL4R and TNF showed associations at a significance level between p = 0.05 and p = 0.0035. These data indicate that (a) GWAS coverage is insufficient for many asthma candidate genes, (b) imputation based on these data is reliable but incomplete, and (c) SNPs in three previously identified asthma candidate genes replicate in our GWAS population with significance after correction for multiple testing in 14 genes.

Epigenetic mechanisms and the relationship to childhood asthma

Epigenetic mechanisms mediate genomic adaption to the environment and epigenetic alterations can contribute to the development of disease phenotypes, as can genetic variants. A variety of molecular mechanisms are involved in epigenetic regulation, including post-transcriptional histone modifications, histone variants, ATP-dependent chromatin remodelling complexes, polycomb/trithorax protein complexes, small and other noncoding RNAs (small interfering RNA and micro RNAs) and DNA methylation. Epigenetic mechanisms have been identified in cancer but very little is known about these effects in complex diseases such as asthma. Epigenetic mechanisms have been found to play a primordial role in T-cell differentiation and novel aspects of asthma and allergy development are now investigated by systematic epigenetic studies. Here we give an introduction to epigenetics, review the existing literature in relation to asthma and asthma-related mechanisms and hypothesise on feasible approaches for the study of epigenetics in asthma in the future.

CT-Guided Core Biopsy of Subchondral Bone and Intervertebral Space in Suspected Spondylodiskitis

OBJECTIVE Our objective was to determine the diagnostic performance of CT-guided core biopsy including both intervertebral disks and subchondral bone in suspected spondylodiskitis and compare the results with those for other biopsy techniques. CONCLUSION CT-guided core biopsy of subchondral bone and intervertebral space compares favorably to previously published studies because histology can provide the diagnosis even when no specific infectious agent is isolated.

Genome-wide association study of body mass index in 23 000 individuals with and without asthma

Both asthma and obesity are complex disorders that are influenced by environmental and genetic factors. Shared genetic factors between asthma and obesity have been proposed to partly explain epidemiological findings of co‐morbidity between these conditions.

Prenatal and early-life exposures alter expression of innate immunity genes: The PASTURE cohort study

BACKGROUND There is evidence that gene expression of innate immunity receptors is upregulated by farming-related exposures. OBJECTIVE We sought to determine environmental and nutritional exposures associated with the gene expression of innate immunity receptors during pregnancy and the first year of a childs life. METHODS For the Protection Against Allergy: Study in Rural Environments (PASTURE) birth cohort study, 1133 pregnant women were recruited in rural areas of Austria, Finland, France, Germany, and Switzerland. mRNA expression of the Toll-like receptor (TLR) 1 through TLR9 and CD14 was assessed in blood samples at birth (n= 938) and year 1 (n= 752). Environmental exposures, as assessed by using questionnaires and a diary kept during year 1, and polymorphisms in innate receptor genes were related to gene expression of innate immunity receptors by using ANOVA and multivariate regression analysis. RESULTS Gene expression of innate immunity receptors in cord blood was overall higher in neonates of farmers (P for multifactorial multivariate ANOVA= .041), significantly so for TLR7 (adjusted geometric means ratio [aGMR], 1.15; 95% CI, 1.02-1.30) and TLR8 (aGMR, 1.15; 95% CI, 1.04-1.26). Unboiled farm milk consumption during the first year of life showed the strongest association with mRNA expression at year 1, taking the diversity of other foods introduced during that period into account: TLR4 (aGMR, 1.22; 95% CI, 1.03-1.45), TLR5 (aGMR, 1.19; 95% CI, 1.01-1.41), and TLR6 (aGMR, 1.20; 95% CI, 1.04-1.38). A previously described modification of the association between farm milk consumption and CD14 gene expression by the single nucleotide polymorphism CD14/C-1721T was not found. CONCLUSION Farming-related exposures, such as raw farm milk consumption, that were previously reported to decrease the risk for allergic outcomes were associated with a change in gene expression of innate immunity receptors in early life.

Different IgE recognition of mite allergen components in asthmatic and nonasthmatic children.

Background House dust mites (HDMs) represent one of the most important inducers of respiratory allergies worldwide. Objective We sought to investigate the IgE and IgG reactivity profiles to a comprehensive panel of HDM allergens in children with allergic asthma and to compare them with those of nonasthmatic atopic children. Methods Sera from clinically well-characterized asthmatic children with HDM allergy (n = 105), nonasthmatic children (n = 53), and nonatopic nonasthmatic children (n = 53) were analyzed for IgE and IgG reactivity to a panel of 7 HDM allergens (nDer p 1, rDer p 2, rDer p 5, rDer p 7, rDer p 10, rDer p 21, and rDer p 23) by means of allergen microarray technology. Results Asthmatic children with HDM allergy more frequently showed an IgE response to each of the HDM allergens and recognized more allergens than nonasthmatic children with HDM allergy. Furthermore, IgE levels to certain HDM allergens (nDer p 1, P = .002; rDer p 2, P = .007; rDer p 5, P = .031; and rDer p 23, P < .001) were significantly higher in asthmatic children than in children without asthma. By contrast, fewer asthmatic children showed IgG reactivity to HDM allergens than nonasthmatic children, but allergen-specific IgG levels were comparable. Conclusion The IgE and IgG reactivity profiles to HDM allergens, as well as IgE levels to certain allergen components, differed considerably between children with and without asthmatic symptoms caused by HDM allergy. In fact, asthmatic children were characterized by an expanded IgE repertoire regarding the numbers of recognized allergen components and by increased specific IgE levels.