Association of FcepsilonR1-beta polymorphisms with asthma and associated traits in Australian asthmatic families

Potential Metabolic Biomarkers in Adult Asthmatics

Asthma is the most common chronic airway inflammation, with multiple phenotypes caused by complicated interactions of genetic, epigenetic, and environmental factors. To date, various determinants have been suggested for asthma pathogenesis by a new technology termed omics, including genomics, transcriptomics, proteomics, and metabolomics. In particular, the systematic analysis of all metabolites in a biological system, such as carbohydrates, amino acids, and lipids, has helped identify a novel pathway related to complex diseases. These metabolites are involved in the regulation of hypermethylation, response to hypoxia, and immune reactions in the pathogenesis of asthma. Among them, lipid metabolism has been suggested to be related to lung dysfunction in mild-to-moderate asthma. Sphingolipid metabolites are an important mediator contributing to airway inflammation in obese asthma and aspirin-exacerbated respiratory disease. Although how these molecular variants impact the disease has not been completely determined, identification of new causative factors may possibly lead to more-personalized and precise pathway-specific approaches for better diagnosis and treatment of asthma. In this review, perspectives of metabolites related to asthma and clinical implications have been highlighted according to various phenotypes.

Study of gene-gene interactions for endophenotypic quantitative traits in Chinese asthmatic children

BACKGROUND

Asthma is a complex disease resulting from interactions between multiple genes and environmental factors. Study of gene-gene interactions could provide insight into the pathophysiology of asthma.

METHODS

We investigated the interactions among 18 single-nucleotide polymorphisms in eight candidate genes for plasma total immunoglobulin E (IgE) concentration and peripheral blood (PB) eosinophil count in 298 Chinese asthmatic children and 175 controls. Generalized multifactor dimensionality reduction and generalized linear model were used to analyze gene-gene interactions for the quantitative traits.

RESULTS

A significant interaction was found between R130Q in IL13 and I50V in IL4RA for plasma total IgE concentration, with a cross-validation (CV) consistency of nine of 10 and a prediction error of 41.1% (P = 0.013). Plasma total IgE concentration was significantly higher in the high-risk than the low-risk groups (P < 0.0001). For PB eosinophil count, significant interaction was found between C-431T in TARC and RsaI_in2 in FCERIB, with a CV consistency of nine of 10 and a prediction error of 40.2% (P = 0.009). PB eosinophil count was significantly higher in the high-risk group than the low-risk groups (P < 0.0001). Generalized linear model also revealed significant gene-gene interaction for the above two endophenotypes with P = 0.013 for plasma total IgE concentration and P = 0.029 for PB eosinophil count respectively.

CONCLUSIONS

Our data suggest significant interactions between IL13 and IL4RA for plasma total IgE concentration, and this is the first report to show significant interaction between TARC and FCERIB for PB eosinophil count in Chinese asthmatic children.

Genome-wide scan on total serum IgE levels identifies FCER1A as novel susceptibility locus

High levels of serum IgE are considered markers of parasite and helminth exposure. In addition, they are associated with allergic disorders, play a key role in anti-tumoral defence, and are crucial mediators of autoimmune diseases. Total IgE is a strongly heritable trait. In a genome-wide association study (GWAS), we tested 353,569 SNPs for association with serum IgE levels in 1,530 individuals from the population-based KORA S3/F3 study. Replication was performed in four independent population-based study samples (total n = 9,769 individuals). Functional variants in the gene encoding the alpha chain of the high affinity receptor for IgE (FCER1A) on chromosome 1q23 (rs2251746 and rs2427837) were strongly associated with total IgE levels in all cohorts with P values of 1.85 x 10(-20) and 7.08 x 10(-19) in a combined analysis, and in a post-hoc analysis showed additional associations with allergic sensitization (P = 7.78 x 10(-4) and P = 1.95 x 10(-3)). The "top" SNP significantly influenced the cell surface expression of FCER1A on basophils, and genome-wide expression profiles indicated an interesting novel regulatory mechanism of FCER1A expression via GATA-2. Polymorphisms within the RAD50 gene on chromosome 5q31 were consistently associated with IgE levels (P values 6.28 x 10(-7)-4.46 x 10(-8)) and increased the risk for atopic eczema and asthma. Furthermore, STAT6 was confirmed as susceptibility locus modulating IgE levels. In this first GWAS on total IgE FCER1A was identified and replicated as new susceptibility locus at which common genetic variation influences serum IgE levels. In addition, variants within the RAD50 gene might represent additional factors within cytokine gene cluster on chromosome 5q31, emphasizing the need for further investigations in this intriguing region. Our data furthermore confirm association of STAT6 variation with serum IgE levels.

[Asthma genetic factors]

Asthma is a chronic inflammatory airways disease, with a rising prevalence, particularly in childhood, and is considered an important public health problem. Its familial transmission is recognised, while the description and identification of the genes implicated in this disease are a challenge. In this revision paper the authors give a comprehensive explanation of the associated genes as well as the laboratorial methods that allow their identification.

Association between IL-13 gene polymorphism and asthma in Han nationality in Hubei Chinese population

In order to investigate whether Arg110Gln polymorphism in the coding region of the IL-13 gene is associated with asthma and total plasma IgE level in Han nationality in Hubei Chinese population, the allele frequency of 4257(g/a) site and Arg110Gln genotype of IL-13 was detected by using restriction fragment length polymorphism in Han nationality in Hubei Chinese population including 43 asthmatic children, 45 asthmatic adults, 31 control children and 46 control adults. Total plasma IgE was measured by Chemiluminescence assay. The results showed that the frequency of allele A at 4257 bp of IL-13 in children and adults was 0.39 and 0.32, respectively. The GlnGln form of Arg110Gln polymorphism of IL-13 gene was associated with susceptibility of asthma and elevated total plasma IgE in children (P=0.030 and 0.0009, respectively), but not with them in adults (P=0.219 and 0.174, respectively). Our results suggest that the Arg110Gln polymorphism of IL-13 gene is associated with susceptibility of asthma and elevated total plasma IgE in Chinese children of Han nationality in Hubei, but not with them in adults.

Patterns of expression, membrane localization, and effects of ectopic expression suggest a function for MS4a4B, a CD20 homolog in Th1 T cells

The membrane-spanning 4A (MS4A) family of proteins includes CD20, Fc epsilonRIbeta, and HTm4, whose genes are grouped in a chromosomal location that is associated with increased susceptibility to allergy and atopic asthma. One family member, Chandra/MS4a4B, was reported to be expressed in T helper 1 (Th1) T cells but not Th2 T cells. In the present study, Ms4a4b was isolated in a screen of genes differentially expressed during thymocyte development. MS4a4B was detected in immature CD4- CD8- CD44+ CD25- thymocytes, turned off during further stages of thymocyte development and reexpressed in mature single-positive thymocytes. MS4a4B expression was found in naive CD8+ and CD4+ peripheral T cells and natural killer (NK) cells but not in B cells. MS4a4B is expressed at the cell surface with its C-terminus located in the cytoplasm. When expressed in a T-cell hybridoma by retroviral vector, MS4a4B protein constitutively associated with lipid raft microdomains, whereas in primary T cells endogenous MS4a4B protein became enriched in rafts after T-cell activation. Overexpression of MS4a4B in primary CD4+ T-cell blasts enhanced T-cell receptor (TCR)-induced Th1 cytokine production. These results suggest that MS4a4B expression is tightly regulated during T-cell development and that MS4a4B expression promotes Th1 function and/or differentiation.

A_16_C haplotype in the FcepsilonRIbeta gene confers a higher risk for atopic asthma in the Indian population

We conducted a case-control study aimed at identifying polymorphisms and haplotypes in the FcepsilonRIbeta gene associated with asthma and its associated phenotypes such as serum IgE levels. A G/A polymorphism in intron 2, a (CA)n repeat polymorphism in intron 5, and a C/T polymorphism in 3'-UTR, encompassing a length of 8.74 Kb, were genotyped, and haplotypes were generated for unrelated patients and healthy volunteers in two independent cohorts. A significant association was observed at the level of alleles and genotypes studied with asthma independently in the two cohorts (p < 0.05). A change in CC_AA genotype combination to a non-CC_AA genotype was associated with reduced risk for asthma. Interestingly, a three-locus haplotype, A_16_C, was found to be significantly associated with asthma (p = 10(-5) in cohort A and p = 0.004 in cohort B). On the other hand, the haplotype G_18_T was found to be negatively associated with asthma (p = 0.007 in cohort A and p = 0.0004 in cohort B). This is the first study identifying a haplotype A_16_C that predisposes individuals to asthma in the Indian population.

The E237G polymorphism of the high-affinity IgE receptor beta chain and asthma

BACKGROUND

The beta chain of high-affinity IgE receptor (FcepsilonRI beta) has been proposed as a candidate gene for asthma and atopic diseases.

OBJECTIVES

To determine the prevalence of the E237G polymorphism of the FcepsilonRI beta gene and to investigate its association with asthma and total IgE levels in 3 Asian populations.

METHODS

A total of 291 asthmatic patients (141 Chinese, 68 Malay, and 82 Indian) and 355 asymptomatic blood donors (157 Chinese, 100 Malay, and 98 Indian) were recruited. The E237G genotype was determined by allele-specific polymerase chain reaction. Total serum IgE level was measured by enzyme-linked immunosorbent assay.

RESULTS

The G allele was more common in Chinese controls (17.9%) than in Malay (11.5%) (P = .05) and Indian (9.2%) (P = .01) controls. Genotypes with the G allele were more prevalent in asthmatic patients in the Chinese population (odds ratio, 1.97; 95% confidence interval, 1.05-3.77; P = .04).

CONCLUSIONS

There were interethnic differences in the frequencies of the G variant among Chinese, Malay, and Indian populations. The E237G polymorphism of FcsRI beta may be a risk factor for asthma in the Chinese population.

Inflammation in allergic asthma: initiating events, immunological response and risk factors

Allergic asthma affects 155 million people worldwide. Currently, it is a disease that can be controlled by diverse therapeutic approaches but that cannot be cured. This means that asthma is one of the most expensive diseases for healthcare systems in developed countries. Efficient prevention strategies are therefore greatly needed to reduce both individual morbidity and national economic burdens. This requires a detailed knowledge of the immunological and physiological mechanisms involved in asthma. This review synthesizes current understanding about the immunobiology of IgE-mediated asthma. It discusses the initiating events, the main immunological and inflammatory processes, and addresses the importance of risk factors in the development and maintenance of allergic diseases. Finally, it integrates these concepts in a theoretical causal model for atopic asthma.

Association studies for asthma and atopic diseases: a comprehensive review of the literature

Hundreds of genetic association studies on asthma-related phenotypes have been conducted in different populations. To date, variants in 64 genes have been reported to be associated with asthma or related traits in at least one study. Of these, 33 associations were replicated in a second study, 9 associations were not replicated either in a second study or a second sample in the same study, and 22 associations were reported in just a single published study. These results suggest the potential for a great amount of heterogeneity underlying asthma. However, many of these studies are methodologically limited and their interpretation hampered by small sample sizes.

Associations between polymorphisms of the high-affinity immunoglobulin E receptor and late-onset airflow obstruction in older populations

OBJECTIVES

To test the hypothesis that genetic polymorphisms in the beta subunit of the high-affinity immunoglobulin E (IgE) receptor are associated with late-onset airflow obstruction.

DESIGN

Case-control candidate gene association study.

SETTING

Department of Medicine for the Elderly and Respiratory Medicine in three teaching hospitals in Leicester and Manchester, United Kingdom.

PARTICIPANTS

Cases with late-onset airflow obstruction with age-, sex-, and geographically matched controls.

MEASUREMENTS

Subjects were genotyped for two polymorphisms of the beta subunit of the high-affinity IgE receptor (RsaI intron 2 and RsaI exon 7). The association between the polymorphisms and phenotypes was examined using contingency tables and linear regression models.

RESULTS

Two hundred eighty-three cases and 144 controls were genotyped. RsaI exon 7 AA was associated with eczema (odds ratio (OR)=2.27, 95% confidence interval (CI)=1.17-4.38, P=.015). No other associations were found. Total serum IgE levels were significantly higher in cases than controls (adjusted OR for high/low IgE=2.56, 95% CI=1.53-4.28, P<.001).

CONCLUSION

Serum IgE levels, but not the high-affinity IgE receptor polymorphisms, were associated with late-onset airflow obstruction, suggesting that interaction between environmental and genetic factors controlling serum IgE levels and disease pathogenesis may differ between early- and late-onset airflow obstruction phenotypes.

Distribution in allele frequencies of predisposition-to-atopy genotypes in Chinese children

Asthma is one of the most common chronic diseases in childhood; it is caused by a complex interaction between genetic factors and exposure to environmental allergens and irritants. Previous studies using the candidate gene approach showed that asthma was linked to a number of susceptibility genetic loci in Caucasian subjects. There are, however, only a few studies on asthma predisposition genes in the Chinese population. We studied the distribution of allele frequencies of I50V for the interleukin-4 receptor, two polymorphisms in intron 2 and exon 7 for the high-affinity IgE receptor (Fc epsilon RI-beta), R16G and E27Q for the beta(2)-adrenoceptor,and R275Q (824G/A) for CC chemokine receptor 3 in Chinese children.Seventy-six patients, with a mean age of 10.6 years, and 70 age- and sex-matched controls, were studied. Significantly more subjects in the asthma group had specific IgE antibodies against environmental allergens (P < 0.0001; odds ratio, 9.82). Genotyping of the six genetic markers showed that none of the six polymorphisms was associated with asthma in this cohort. The allele frequencies of I50V, R16G, and E27Q in our population were similar to those published for Asian subjects but not Caucasians. The R275Q substitution was a rare finding in our study and in the published reports. Our results demonstrate ethnic differences in polymorphisms of atopy candidate genes. Additional studies involving larger samples are required to investigate the association between asthma or atopy and the genotypes studied to date in Chinese children.

Associations of Fc epsilon R1-beta polymorphisms with immunoglobin E antibody responses to common inhalant allergens in a rural population

BACKGROUND

Polymorphisms within the beta subunit of the high-affinity receptor for IgE (Fc epsilon R1-beta ) on chromosome 11q13 have been related to atopy and asthma and the lymphotoxin alpha (LT alpha) gene on chromosome 6 is implicated in asthma.

OBJECTIVE

To elucidate the association of polymorphisms in the Fc epsilon R1-beta and LT alpha genes to IgE responses and asthma in a family-orientated rural population.

METHODS

A total of 461 adult farmers, who participated in an epidemiological follow-up study on respiratory symptoms among farmers on the Swedish island of Gotland, were examined. The traits assessed included serum total IgE, IgE antibody responses to 21 common inhalant allergens and asthma.

RESULTS

The 237G mutation was only detected in seven persons. Atopy was found to be associated with the RsaI-ex7 AB-genotype (OR = 1.9; P = 0.04). The RsaI-ex7 B allele had a significant influence on IgE responses to pollens and dust mites (OR = 5.5; P = 0.03 and OR = 5.2; P = 0.049, respectively). The influence of this allele was stronger when the association towards single dust mite species (Lepidoglyphus destructor) was estimated (OR = 7.1, P = 0.03) and the association increased even more when the major allergen of L. destructor (rLep d 2) was analysed (OR = 11.2, P = 0.02). These associations were independent of sex, age and smoking, and the estimates of RsaI-in2 independent of RsaI-ex7. RsaI-in2, RsaI-ex7 and LT alpha genotypes were unassociated with total serum IgE. No significant difference in the distribution of RsaI-in2, RsaI-ex7 and LT alpha genotypes was found among subjects with atopy or asthma compared to healthy controls.

CONCLUSION

This study supports the notion that polymorphisms in the Fc epsilon R1-beta gene have significant effects on IgE responsiveness. Secondly, dust mites in rural populations influence the expression of genes on chromosome 11q13.

What we know about the genetics of asthma at the beginning of the 21st century

The understanding of the genetic controls that lead to the development of asthma is essential to its proper diagnosis and management. As we enter the 21st century, the goals of genetic research in asthma and allergies will be to: 1) identify genetic factors, 2) define environmental cofactors, 3) characterize how genes and the environment work together to cause disease, 4) develop treatment and prevention measures, including drugs designed for the individual's genetic make-up.

Interactions between genes and environmental factors in asthma and atopy: new developments

Asthma and associated phenotypes are complex traits most probably caused by an interaction of multiple disease susceptibility genes and environmental factors. Major achievements have occurred in identifying chromosomal regions and polymorphisms in candidate genes linked to or associated with asthma, atopic dermatitis, IgE levels and response to asthma therapy. The aims of this review are to explain the methodology of genetic studies of multifactorial diseases, to summarize chromosomal regions and polymorphisms in candidate genes linked to or associated with asthma and associated traits, to list genetic alterations that may alter response to asthma therapy, and to outline genetic factors that may render individuals more susceptible to asthma and atopy due to environmental changes.

A polymorphism in the coding region of interleukin-13 gene is associated with atopy but not asthma in Chinese children

BACKGROUND

Interleukin (IL)-13 is an important cytokine secreted from type 2 helper T lymphocytes. It is essential for modulating IgE synthesis by human B cells. Previous studies showed that polymorphisms in the IL-13 gene were associated with serum total IgE or allergic asthma. The relationship of this marker with sensitization to individual aeroallergens has not been evaluated.

OBJECTIVE

We tested whether a polymorphism in the coding region of the IL-13 gene is associated with asthma and atopy in asthmatic children in Hong Kong.

METHODS

We used restriction fragment length polymorphism to detect R130Q genotype in Chinese children with asthma and control subjects. Serum total IgE was measured by microparticle immunoassay and specific IgE to common aeroallergens was measured using fluorescent enzyme immunoassay. Pulmonary function studies were performed using spirometry.

RESULTS

One hundred and fifty-seven patients and 54 control children were recruited. Their mean serum total IgE concentrations were 994 kIU/L and 473 kIU/L, respectively (P < 0.0001). Atopy as defined by > or = 1 positive RAST was found in 141 patients and 32 control children. The GlnGln form of the R130Q polymorphism in the IL-13 gene was associated with serum total IgE (P = 0.005) as well as specific IgE to Der p 1 (P = 0.021), mixed cockroaches (P = 0.03) and dog (P = 0.003) but not with physician-diagnosed asthma (P = 0.621). In addition, the R130Q polymorphism did not correlate with subjective or objective indicators of asthma severity in our patients.

CONCLUSION

Our results suggest that the R130Q polymorphism of the IL-13 gene is associated with elevated serum total and allergen-specific IgE but not asthma in Chinese children.

An IL13 coding region variant is associated with a high total serum IgE level and atopic dermatitis in the German multicenter atopy study (MAS-90)

BACKGROUND

Allergic diseases are one of the major causes of morbidity in the developed countries today, and the prevalence of these diseases is increasing steadily. Study of total serum gE level is important in understanding the genetics of allergic iseases because IgE levels are considered to be a crucial pathogenic component. IL-13 plays an important role in the induction of IgE synthesis and in the pathogenesis of allergic diseases.

OBJECTIVE

We sought to examine potential variation at the IL13 gene and estimate its effect on elevated IgE level and atopic dermatitis (AD).

METHODS

We conducted mutational analyses of the IL13 gene by using single-stranded conformation polymorphism and DNA sequencing. Case control studies for high-IgE phenotype and AD were performed by using subjects from the German MAS-90 cohort.

RESULTS

A novel IL13 coding region variant at 4257 bp (G to A, fourth exon) was identified. Case control studies of a German sample from the MAS-90 cohort showed significant associations between the presence of the A allele and two atopic phenotypes: high IgE (odds ratio, 2.38; 95% confidence interval, 1.35-4.21; P =.0026) and AD (odds ratio, 1.77; 95% confidence interval, 1.06-2.96; P =.03).

CONCLUSION

This IL13 coding region variant may be involved in the pathogenesis of AD and high total serum IgE level in a study population of white subjects.