IL-13 receptor α2 (IL-13Rα2) is a high-affinity receptor for IL-13, a central mediator of allergic asthma. It acts predominantly as a decoy receptor but can also contribute to IL-13 responses under certain conditions. IL-13Rα2 exists in soluble and membrane forms, which can both bind IL-13 and modulate its activity. Yet the proteolytic processes that contribute to the generation of soluble IL-13Rα2 are largely unknown.
We sought to investigate the role of matrix metalloproteinases (MMPs) in the generation of soluble IL-13Rα2.
Acellular cleavage assays by MMPs were performed by using glutathione-S-transferase fusion proteins of murine or human IL-13Rα2. IL-13Rα2 stable-transfected cells were used for analysis of surface expression and release of soluble IL-13Rα2. Wild-type and MMP-8–deficient mice were used for analysis of allergen-induced airway hyperresponsiveness and solubilization of IL-13Rα2.
Among several MMPs tested, only MMP-8 cleaved IL-13Rα2. Treatment of transfected human or murine cells expressing high levels of surface IL-13Rα2 with MMP-8 resulted in release of soluble IL-13Rα2 into the supernatants, with a concomitant decrease in surface IL-13Rα2 levels. The IL-13Rα2 solubilized by MMP-8 retained IL-13 binding activity. In an asthma model MMP-8–deficient mice displayed increased airway hyperresponsiveness and decreased soluble IL-13Rα2 protein levels in bronchoalveolar lavage fluid compared with those seen in wild-type mice after house dust mite challenge.
MMP-8 cleaves IL-13Rα2 in vitro and contributes to the solubilization of IL-13Rα2 in vivo.
Matrix metalloproteinase 8; IL-13; IL-13 receptor α2
The specific cause(s) of asthma development must be identified in order to prevent this disease.
Our hypothesis was that specific mold exposures are associated with childhood asthma development.
Infants were identified from birth certificates. Dust samples were collected from 289 homes when the infants were age eight months. Samples were analyzed for concentrations of 36 molds that comprise the Environmental Relative Moldiness Index (ERMI) and endotoxin, house dust mite, cat, dog, and cockroach allergens. Children were evaluated at age seven for asthma based on reported symptoms and objective measures of lung function. Host, environmental exposures and home characteristics evaluated included history of parental asthma, race, gender, upper and lower respiratory symptoms, season of birth, family income, cigarette smoke exposure, air conditioning, dehumidifier, carpeting, age of home, and visible mold at age one and child positive skin prick test (SPT) to aeroallergens and molds at age seven.
Asthma was diagnosed in 24% of the children at age seven. A statistically significant increase in asthma risk at age seven was associated with high ERMI levels in the child’s home in infancy (adjusted risk ratio (aRR) for a 10-unit increase in ERMI = 1.8, 95% CI=1.5, 2.2). The summation of levels of three mold species, Aspergillus ochraceus, Aspergillus unguis, and Penicillium variabile was significantly associated with asthma (aRR = 2.2, 95% CI=1.8, 2.7).
In this birth cohort study, exposure during infancy to three mold species common to water-damaged buildings was associated with childhood asthma at age seven.
Asthma; molds; speciation; infants; Environmental Relative Moldiness Index
A wealth of genomic information is available in public and private databases. However, this information is underutilized for uncovering population specific and functionally relevant markers underlying complex human traits. Given the huge amount of SNP data available from the annotation of human genetic variation, data mining is a faster and cost effective approach for investigating the number of SNPs that are informative for ancestry. In this study, we present AncestrySNPminer, the first web-based bioinformatics tool specifically designed to retrieve Ancestry Informative Markers (AIMs) from genomic data sets and link these informative markers to genes and ontological annotation classes. The tool includes an automated and simple “scripting at the click of a button” functionality that enables researchers to perform various population genomics statistical analyses methods with user friendly querying and filtering of data sets across various populations through a single web interface. AncestrySNPminer can be freely accessed at https://research.cchmc.org/mershalab/AncestrySNPminer/login.php.
Ancestry; Ancestry informative markers; AIMs; Bioinformatics; AncestrySNPminer; Data mining; Admixture; Admixture mapping
Secondhand smoke is associated with a myriad of adverse health outcomes. Therefore, it is essential for clinicians to ask precise questions about exposures, particularly for children. We present 4 questions that incorporate several locations of exposure and provide a more comprehensive account of children’s smoke exposures than maternal smoking alone.
Eczema is a chronic inflammatory disorder of the skin that affects up to 30% of children. It often afflicts infants in the first few months of life and can be the first indicator of the atopic march. Recent results from birth cohort studies have uncovered novel information regarding genetic and environmental factors that promote the development of eczema. Birth cohort studies provide an optimal study design to elucidate these associations and prospectively track longitudinal data including exposure assessment and health outcomes from birth into early life and childhood. This is especially relevant for eczema given the age specific emergence of this disease. In this review, we will provide a general overview of pediatric eczema and discuss the important findings in the literature with respect to genetics and environmental exposures, highlighting those derived from birth cohort studies. Additionally, we will review how these relate to the atopic march, the hygiene hypothesis and the integrity of the skin barrier.
atopic march; hygiene hypothesis; genetics; skin barrier; environment; birth cohort study
Completion of the human genome project and rapid progress in genetics and bioinformatics have enabled the development of large public databases, which include genetic and genomic data linked to clinical health data. With the massive amount of information available, clinicians and researchers have the unique opportunity to complement and integrate their daily practice with the existing resources to clarify the underlying etiology of complex phenotypes such as allergic diseases. The genome itself is now often utilized as a starting point for many studies and multiple innovative approaches have emerged applying genetic/genomic strategies to key questions in the field of allergy and immunology. There have been several successes, which have uncovered new insights into the biologic underpinnings of allergic disorders. Herein, we will provide an in depth review of genomic approaches to identifying genes and biologic networks involved in allergic diseases. We will discuss genetic and phenotypic variation, statistical approaches for gene discovery, public databases, functional genomics, clinical implications, and the challenges that remain.
gene; allergy; database; browser; genome; common variants; rare variants; HapMap; imputation
Rationale: Murine models demonstrate a synergistic production of reactive oxygen species on coexposure to diesel exhaust particles and endotoxin.
Objectives: It was hypothesized that coexposure to traffic-related particles and endotoxin would have an additive effect on persistent wheezing during early childhood.
Methods: Persistent wheezing at age 36 months was assessed in the Cincinnati Childhood Allergy and Air Pollution Study, a high-risk birth cohort. A time-weighted average exposure to traffic-related particles was determined by applying a land-use regression model to the homes, day cares, and other locations where children spent time from birth through age 36 months. Indoor levels of endotoxin were measured from dust samples collected before age 12 months. The relationship between dichotomized (≥75th percentile) traffic-related particle and endotoxin exposure and persistent wheezing, controlling for potential covariates, was examined.
Measurements and Main Results: Persistent wheezing at age 36 months was significantly associated with exposure to increased levels of traffic-related particles before age 12 months (OR = 1.75; 95% confidence interval, 1.07–2.87). Coexposure to endotoxin had a synergistic effect with traffic exposure on persistent wheeze (OR = 5.85; 95% confidence interval, 1.89–18.13) after adjustment for significant covariates.
Conclusions: The association between traffic-related particle exposure and persistent wheezing at age 36 months is modified by exposure to endotoxin. This finding supports prior toxicological studies demonstrating a synergistic production of reactive oxygen species after coexposure to diesel exhaust particles and endotoxin. The effect of early versus later exposure to traffic-related particles, however, remains to be studied because of the high correlation between exposure throughout the first 3 years of life.
particles; diesel; land-use regression; wheeze; endotoxin
Transforming growth factor (TGF)-α and its receptor, the epidermal growth factor receptor, are induced after lung injury and are associated with remodeling in chronic pulmonary diseases, such as pulmonary fibrosis and asthma. Expression of TGF-α in the lungs of adult mice causes fibrosis, pleural thickening, and pulmonary hypertension, in addition to increased expression of a transcription factor, early growth response-1 (Egr-1). Egr-1 was increased in airway smooth muscle (ASM) and the vascular adventitia in the lungs of mice conditionally expressing TGF-α in airway epithelium (Clara cell secretory protein–rtTA+/−/[tetO]7–TGF-α+/−). The goal of this study was to determine the role of Egr-1 in TGF-α–induced lung disease. To accomplish this, TGF-α–transgenic mice were crossed to Egr-1 knockout (Egr-1ko/ko) mice. The lack of Egr-1 markedly increased the severity of TGF-α–induced pulmonary disease, dramatically enhancing airway muscularization, increasing pulmonary fibrosis, and causing greater airway hyperresponsiveness to methacholine. Smooth muscle hyperplasia, not hypertrophy, caused the ASM thickening in the absence of Egr-1. No detectable increases in pulmonary inflammation were found. In addition to the airway remodeling disease, vascular remodeling and pulmonary hypertension were also more severe in Egr-1ko/ko mice. Thus, Egr-1 acts to suppress epidermal growth factor receptor–mediated airway and vascular muscularization, fibrosis, and airway hyperresponsiveness in the absence of inflammation. This provides a unique model to study the processes causing pulmonary fibrosis and ASM thickening without the complicating effects of inflammation.
transforming growth factor-α; pulmonary fibrosis; asthma; pulmonary hypertension; vascular remodeling
Established indicators of central obesity include waist circumference, waist to height ratio and the conicity index. Studies utilizing such measures (as opposed to body mass index (BMI) percentiles) to characterize the association between obesity and asthma are lacking despite the fact that these measures have been shown to be most relevant for many other chronic diseases.
To examine measures assessing the distribution of obesity in the context of childhood allergic rhinitis and asthma, and to elucidate the association of obesity, including central obesity, with allergic asthma in children.
Children with allergic rhinitis with (cases) or without (controls) asthma were recruited. BMI percentiles were derived using national growth charts. Waist circumference, waist to height ratio, and conicity index were obtained.
Central obesity was associated with asthma, asthma severity, lower lung function, and reduced atopy in asthmatics.
Measures of central obesity are more associated with the presence of asthma and asthma severity in children with allergic rhinitis when compared to standard BMI measures.
Current practices of measuring weight and height in pediatric clinics that treat children with allergic rhinitis should include waist circumference measurements to better assess obesity and asthma risk.
Asthma; Obesity; Children; BMI percentiles; Waist circumference
Although mice have ng/ml serum levels of soluble (s) IL-13Rα2, humans lack sIL-13Rα2 in serum. Our data provide a mechanism for this biologic divergence. In mice, discrete transcripts encoding s and membrane (mem) forms of IL-13Rα2 are generated by alternative splicing. We utilized siRNA to specifically deplete the transcript encoding memIL-13Rα2 (full-length) or sIL-13Rα2 (ΔEx10) in murine cells. Depletion of the full-length transcript decreased memIL-13Rα2, but had no effect on the level of sIL-13Rα2 in cell supernatants at baseline or following cytokine stimulation. Depletion of the ΔEx10 transcript decreased sIL-13Rα2 in supernatants at baseline and following stimulation. In contrast to mice, we were unable to find a transcript encoding sIL-13Rα2 in humans and siRNA-mediated depletion of full-length IL-13Rα2 decreased both sIL-13Rα2 and memIL-13Rα2 in human cells. Inhibition of matrix metalloproteinases (MMPs)/MMP-8 abolished production of sIL-13Rα2 from human cells. Thus, sIL-13Rα2 is derived exclusively from the memIL-13Rα2 transcript in humans through MMPs/MMP-8 cleavage of memIL-13Rα2, supporting a limited role for sIL-13Rα2 in humans and highlighting the potential importance of memIL-13Rα2 in human immunity. These observations require consideration when results of murine IL-13 studies are applied to humans.
IL-13 receptor; membrane form; soluble form; siRNA; IL-13; MMP-8
Previous studies of allergic rhinitis in children have not documented the environmental risk factors for infants at age one. We examined the relationship of environmental tobacco smoke (ETS) and visible mold exposures on the development of allergic rhinitis, rhinitis and upper respiratory infection (URI) in a birth cohort where at least one parent was skin prick test (SPT) positive. ETS exposure and upper respiratory symptoms were obtained by questionnaires. Visible mold was classified as none, low or high during home visit. Infants had a SPT at age one. After adjustment for potential confounders, exposure to >20 cigarettes per day was associated with an increased risk of developing allergic rhinitis at age one [odds ratio (OR) =2.7; 95% CI 1.04–6.8] and rhinitis symptoms during the first year (OR =1.9; 95% CI 1.1–3.2). Infants with low (OR =1.5; 95% CI 1.1–2.3) or high (OR =5.1; 95% CI 2.2–12.1) levels of visible mold in their homes were more likely to have more frequent URI during the first year. Older siblings were protective for development of both rhinitis symptoms and allergic rhinitis. This study suggests that ETS exposure, rather than visible mold, is associated with rhinitis and allergic rhinitis in infants. The analysis also suggests that mold may be a stronger risk factor for URI that ETS.
environmental tobacco smoke; mold; allergic rhinitis; rhinitis; infant; upper respiratory infection
Increased exposure to microbial products early in life may protect from development of atopic disorders in childhood. Few studies have examined the relationship of endotoxin exposure and pet ownership on atopy and wheezing during infancy.
Evaluate relationships among high endotoxin exposure, pet ownership, atopy, and wheezing in high-risk infants.
Infants (n = 532; mean age, 12.5 ± 0.8 months) with at least 1 parent with confirmed atopy were recruited. A complete medical history and skin prick testing to foods and aeroallergens were performed at age 1 year. House dust samples were analyzed for endotoxin.
Prevalences of wheezing were not independently associated with dog or cat ownership or endotoxin levels. Percutaneous reactivity to at least 1 allergen was observed in 28.6% of infants. Univariate analyses showed significant associations of any wheezing, recurrent wheezing, and recurrent wheezing with an event with daycare attendance, number of siblings, respiratory infections, maternal smoking, and history of parental asthma. Logistic regression adjusting for the latter variables showed that recurrent wheezing (odds ratio, 0.4; 95% CI, 0.1–0.9) as well as 2 other wheeze outcomes were significantly reduced in homes with high endotoxin exposure in the presence of 2 or more dogs.
Pet ownership or endotoxin did not independently modify aeroallergen sensitization or wheezing during infancy. However, high endotoxin exposure in the presence of multiple dogs was associated with reduced wheezing in infants. Clinical implications: A home environment with many dogs and high levels of endotoxin may be conducive to reduced wheezing in infancy.
Endotoxin; birth cohort; wheeze; house dust; pet ownership
To present methodology to identify atopic parents and determine the prevalence of sensitization to 15 aeroallergens in their infant offspring.
A birth cohort of infants was identified from birth records; an infant was enrolled if 1 of the parents reported allergy respiratory symptoms and had a positive skin prick test (SPT) to a common aeroallergen. At age 1 year, these infants were tested to the same aeroallergens.
Of the 680 enrolled infants, 28.4% were SPT+ to 1 or more aeroallergens and/or food, and 18.0% were positive to 1 or more aeroallergens. By category of allergens, 9.7% were sensitized to pollens, 7.5% to molds, 4.3% to house dust mite and/or cockroach, and 3.4% to dog and/or cat. Of the infants who were positive to an aeroallergen, 65.7% remained positive at age 2 years.
Infants born to atopic parents with percutaneous sensitization to aeroallergens are at increased risk for aeroallergen sensitization during infancy, which persists to age 2 years. These findings suggest that current clinical practices, which generally avoid skin testing before age 2 years, be reassessed in this population of high-risk children.
The results of a traditional visual mold inspection were compared to a mold evaluation based on the Relative Moldiness Index (RMI). The RMI is calculated from mold-specific quantitative PCR (MSQPCR) measurements of the concentration of 36 species of molds in floor dust samples. These two prospective mold evaluations were used to classify the mold condition in 271 homes of infants. Later, the development of respiratory illness was measured in the infants living in these homes and the predictive value of each classification system was evaluated.
The binary classification of homes as either moldy or non-moldy by on-site visual home inspection was not predictive of the development of respiratory illness (wheeze and/or rhinitis) (P = 0.27). Conversely, a method developed and validated in this paper, using the RMI index fit to a logistic function, can be used to predict the occurrence of illness in homes and allows stake-holders the choice among various levels of risk.
mold-specific quantitative PCR; mold; infants; wheezing; relative moldiness index
Allergic sensitization is very prevalent and often precedes the development of allergic disease. This study examined the association of race with allergic sensitization among healthy children with no family history of atopy.
275 children, predominantly from lower socioeconomic strata, from Cincinnati, OH aged 2 to 18 years without a family or personal history of allergic diseases, underwent skin prick testing to eleven allergen panels. The Pediatric Allergic Disease Quality of Life Questionnaire (PADQLQ) was used to examine the impact of sensitization on quality of life.
39% of healthy children were sensitized to ≥1 allergen panels. Multivariate logistic regression showed increased risk among African American children for any sensitization (OR 2.17; [95% CI; 1.23, 3.84]) and sensitization to any outdoor allergen (OR 2.96 [95% CI; 1.52, 5.74]). 86% of children had PADQLQ scores ≤1 (0 to 6 scale).
Allergic sensitization is prevalent even among children who do not have a personal or family history of asthma, allergic rhinitis, or atopic dermatitis, and who have no evidence of current even subtle effects from this sensitization on allergic-disease related quality of life. African American children are at greater risk for presence of sensitization, especially to outdoor allergens.
Allergic sensitization; atopy; race; quality of life; child
Goblet cell hyperplasia and mucous hypersecretion contribute to the pathogenesis of chronic pulmonary diseases including cystic fibrosis, asthma, and chronic obstructive pulmonary disease. In the present work, mouse SAM pointed domain-containing ETS transcription factor (SPDEF) mRNA and protein were detected in subsets of epithelial cells lining the trachea, bronchi, and tracheal glands. SPDEF interacted with the C-terminal domain of thyroid transcription factor 1, activating transcription of genes expressed selectively in airway epithelial cells, including Sftpa, Scgb1a1, Foxj1, and Sox17. Expression of Spdef in the respiratory epithelium of adult transgenic mice caused goblet cell hyperplasia, inducing both acidic and neutral mucins in vivo, and stainined for both acidic and neutral mucins in vivo. SPDEF expression was increased at sites of goblet cell hyperplasia caused by IL-13 and dust mite allergen in a process that was dependent upon STAT-6. SPDEF was induced following intratracheal allergen exposure and after Th2 cytokine stimulation and was sufficient to cause goblet cell differentiation of Clara cells in vivo.
We previously reported an association between infant wheezing and residence < 100 m from stop-and-go bus and truck traffic. The use of a proximity model, however, may lead to exposure misclassification.
Results obtained from a land use regression (LUR) model of exposure to truck and bus traffic are compared with those obtained with a proximity model. The estimates derived from the LUR model were then related to infant wheezing.
We derived a marker of diesel combustion—elemental carbon attributable to traffic sources (ECAT)—from ambient monitoring results of particulate matter with aerodynamic diameter < 2.5 μm. We developed a multiple regression model with ECAT as the outcome variable. Variables included in the model were locations of major roads, bus routes, truck traffic count, and elevation. Model parameter estimates were applied to estimate individual ECAT levels at infants’ homes.
The levels of estimated ECAT at the monitoring stations ranged from 0.20 to 1.02 μg/m3. A LUR model of exposure with a coefficient of determination (R2) of 0.75 was applied to infants’ homes. The mean (± SD) ambient exposure of ECAT for infants previously categorized as unexposed, exposed to stop-and-go traffic, or exposed to moving traffic was 0.32 ± 0.06, 0.42 ± 0.14, and 0.49 ± 0.14 μg/m3, respectively. Levels of ECAT from 0.30 to 0.90 μg/m3 were significantly associated with infant wheezing.
The LUR model resulted in a range of ECAT individually derived for all infants’ homes that may reduce the exposure misclassification that can arise from a proximity model.
diesel; land; model; proximity; regression; spatial; traffic; use
Small proline rich protein 2B (SPRR2B) is a skin and lung epithelial protein associated with allergic inflammation in mice that has not been evaluated in human atopic diseases.
To determine whether single-nucleotide polymorphisms (SNPs) in SPRR2B are associated with childhood eczema and with the phenotype of childhood eczema combined with asthma.
Genotyping for SPRR2B and filaggrin (FLG) was performed in 2 independent populations: the Cincinnati Childhood Allergy & Air Pollution Study (CCAAPS; N = 762; birth-age, 4 years) and the Greater Cincinnati Pediatric Clinical Repository (GCPCR;N = 1152; ages 5–10 years). Eczema and eczema plus asthma were clinical outcomes based on parental report and clinician’s diagnosis. Genetic analyses were restricted to whites and adjusted for sex in both cohorts and adjusted for environmental covariates in CCAAPS.
Variants in SPRR2B were not significantly associated with eczema in either cohort after Bonferroni adjustment. Children from both cohorts with the CC genotype of the SPRR2B rs6693927 SNP were at 4 times the risk for eczema plus asthma (adjusted odds ratio, 4.1; 95% confidence interval, 1.5– 10.9; P = .005 in CCAAPS; and adjusted odds ratio, 4.0; 95% confidence interval, 1.8 –9.1; P <.001 in the GCPCR), however. SNPs in SPRR2B were not in strong linkage disequilibrium with the R501X and del2282 FLG mutations, and these findings were independent of FLG.
An SNP in SPRR2B was predictive of asthma among white children with eczema from 2 independent populations. SPRR2B polymorphisms may serve as important predictive markers for the combined eczema plus asthma phenotype.
Diesel exhaust particle (DEP) exposure enhances allergic inflammation and has been linked to the incidence of asthma. Oxidative stress on the thiol molecules cysteine (Cys) and glutathione (GSH) can promote inflammatory host responses. The effect of DEP on the thiol oxidation/reduction (redox) state in the asthmatic lung is unknown.
To determine if DEP exposure alters the Cys or GSH redox state in the asthmatic airway.
Bronchoalveolar lavage fluid was obtained from a house dust mite (HDM) induced murine asthma model exposed to DEP. GSH, glutathione disulfide (GSSG), Cys, cystine (CySS), and s-glutathionylated cysteine (CySSG) were determined by high pressure liquid chromatography.
DEP co-administered with HDM, but not DEP or HDM alone, decreased total Cys, increased CySS, and increased CySSG without significantly altering GSH or GSSG.
DEP exposure promotes oxidation and S-glutathionylation of cysteine amino acids in the asthmatic airway, suggesting a novel mechanism by which DEP may enhance allergic inflammatory responses.
Glutathione S-transferase Pi (GSTPi) is the predominant redox regulator in the lung. While evidence implicates an important role for GSTPi in asthma, the mechanism for this has remained elusive.
To determine how GSTPi is regulated in asthma and to elucidate its role in maintaining redox homeostasis.
We elucidated the regulation of GSTPi in children with asthma and utilized murine models of asthma to determine the role of GSTPi in redox homeostasis.
Measurements and Main Results
Our findings demonstrate that GSTPi transcript levels are markedly down-regulated in allergen and IL-13 treated mouse models of asthma via STAT6 dependent and independent pathways. Nuclear factor-erythroid 2 related factor 2 (Nrf2) was also down-regulated in these models. The decrease in GSTPi expression was associated with decreased total GST activity in the lungs of mice. Examination of cystine intermediates uncovered a functional role for GSTPi in regulating Cys oxidation, whereby GSTPi-deficient mice exhibited increased oxidative stress (increase in % cystine) compared with wild-type mice following allergen challenge. GSTPi expression was similarly down-regulated in children with asthma.
These data collectively suggest that down-regulation of GSTPi following allergen challenge may contribute to the asthma phenotype due to disruption of redox homeostasis and increased oxidative stress. Furthermore, GSTPi may be an important therapeutic target for asthma, and evaluation of GSTPi expression may prove beneficial in identifying individuals who would benefit from therapy targeting this pathway.
GSTPi; asthma; oxidative stress; redox homeostasis; gene
Allergic disorders, including asthma, allergic rhinitis, atopic dermatitis, eosinophilic esophagitis, and food allergy, are a major global health burden. The study and management of allergic disorders is complicated by the considerable heterogeneity in both the presentation and natural history of these disorders. Biorepositories serve as an excellent source of data and biospecimens for delineating subphenotypes of allergic disorders, but such resources are lacking.
In order to define subphenotypes of allergic disease accurately, we established an infrastructure to link and efficiently utilize clinical and epidemiologic data with biospecimens into a single biorepository called the Greater Cincinnati Pediatric Clinic Repository (GCPCR). Children with allergic disorders as well as healthy controls are followed longitudinally at hospital clinic, emergency department, and inpatient visits. Subjects' asthma, allergy, and skin symptoms; past medical, family, social, diet, and environmental histories; physical activity; medication adherence; perceived quality of life; and demographics are ascertained. DNA is collected from all participants, and other biospecimens such as blood, hair, and nasal epithelial cells are collected on a subset.
To date, the GCPCR has 6,317 predominantly Caucasian and African American participants, and 93% have banked DNA. This large sample size supports adequately powered genetic, epidemiologic, environmental, and health disparities studies of childhood allergic diseases.
The GCPCR is a unique biorepository that is continuously evaluated and refined to achieve and maintain rigorous clinical phenotype and biological data. Development of similar disease-specific repositories using common data elements is necessary to enable studies across multiple populations of comprehensively phenotyped patients.
Asthma is a major public health burden worldwide. Studies from our group and others have demonstrated that SERPINB3 and B4 are induced in asthmatics; however their mechanistic role in asthma has yet to be determined.
To evaluate the role of Serpin3a, the murine homolog of human SERPINB3 and B4, in asthma.
We studied wild type Balb/c and Serpinb3a null mice in house dust mite or IL-13 induced asthma models and evaluated airway hyperresponsiveness, inflammation, and goblet cell hyperplasia.
Airway hyperresponsiveness and goblet cell hyperplasia were markedly attenuated in the Serpinb3a null mice compared to the wild type mice following allergen challenge, with minimal effects on inflammation. Expression of SPDEF, a transcription factor that mediates goblet cell hyperplasia, was decreased in the absence of Serpinb3a. IL-13 treated Serpinb3a null mice showed attenuated AHR, inflammation, and mucus production.
Excessive mucus production and mucus plugging are key pathologic features of asthma, yet the mechanisms responsible for mucus production are not well understood. Our data reveal a novel non-redundant role for Serpinb3a in mediating mucus production through regulation of SPDEF expression. This pathway may be used to effectively target mucus hypersecretion.
goblet cells; SPDEF; IL-13; hyperplasia
Admixture mapping is a powerful gene mapping approach for an admixed population formed from ancestral populations with different allele frequencies. The power of this method relies on the ability of ancestry informative markers (AIMs) to infer ancestry along the chromosomes of admixed individuals. In this study, more than one million SNPs from HapMap databases and simulated data have been interrogated in admixed populations using various measures of ancestry informativeness: Fisher Information Content (FIC), Shannon Information Content (SIC), F statistics (FST), Informativeness for Assignment Measure (In), and the Absolute Allele Frequency Differences (delta, δ). The objectives are to compare these measures of informativeness to select SNP markers for ancestry inference, and to determine the accuracy of AIM panels selected by each measure in estimating the contributions of the ancestors to the admixed population.
FST and In had the highest Spearman correlation and the best agreement as measured by Kappa statistics based on deciles. Although the different measures of marker informativeness performed comparably well, analyses based on the top 1 to 10% ranked informative markers of simulated data showed that In was better in estimating ancestry for an admixed population.
Although millions of SNPs have been identified, only a small subset needs to be genotyped in order to accurately predict ancestry with a minimal error rate in a cost-effective manner. In this article, we compared various methods for selecting ancestry informative SNPs using simulations as well as SNP genotype data from samples of admixed populations and showed that the In measure estimates ancestry proportion (in an admixed population) with lower bias and mean square error.
Asthma is a chronic inflammatory disease with a strong genetic predisposition. A major challenge for candidate gene association studies in asthma is the selection of biologically relevant genes.
Using epithelial RNA expression arrays, HapMap allele frequency variation, and the literature, we identified six possible candidate susceptibility genes for childhood asthma including ADCY2, DNAH5, KIF3A, PDE4B, PLAU, SPRR2B. To evaluate these genes, we compared the genotypes of 194 predominantly tagging SNPs in 790 asthmatic, allergic and non-allergic children. We found that SNPs in all six genes were nominally associated with asthma (p<0.05) in our discovery cohort and in three independent cohorts at either the SNP or gene level (p<0.05). Further, we determined that our selection approach was superior to random selection of genes either differentially expressed in asthmatics compared to controls (p = 0.0049) or selected based on the literature alone (p = 0.0049), substantiating the validity of our gene selection approach. Importantly, we observed that 7 of 9 SNPs in the KIF3A gene more than doubled the odds of asthma (OR = 2.3, p<0.0001) and increased the odds of allergic disease (OR = 1.8, p<0.008). Our data indicate that KIF3A rs7737031 (T-allele) has an asthma population attributable risk of 18.5%. The association between KIF3A rs7737031 and asthma was validated in 3 independent populations, further substantiating the validity of our gene selection approach.
Our study demonstrates that KIF3A, a member of the kinesin superfamily of microtubule associated motors that are important in the transport of protein complexes within cilia, is a novel candidate gene for childhood asthma. Polymorphisms in KIF3A may in part be responsible for poor mucus and/or allergen clearance from the airways. Furthermore, our study provides a promising framework for the identification and evaluation of novel candidate susceptibility genes.
Candidate gene case-control studies have identified several single nucleotide polymorphisms (SNPs) that are associated with asthma susceptibility. Most of these studies have been restricted to evaluations of specific SNPs within a single gene and within populations from European ancestry. Recently, there is increasing interest in understanding racial differences in genetic risk associated with childhood asthma. Our aim was to compare association patterns of asthma candidate genes between children of European and African ancestry.
Using a custom-designed Illumina SNP array, we genotyped 1,485 children within the Greater Cincinnati Pediatric Clinic Repository and Cincinnati Genomic Control Cohort for 259 SNPs in 28 genes and evaluated their associations with asthma. We identified 14 SNPs located in 6 genes that were significantly associated (p-values <0.05) with childhood asthma in African Americans. Among Caucasians, 13 SNPs in 5 genes were associated with childhood asthma. Two SNPs in IL4 were associated with asthma in both races (p-values <0.05). Gene-gene interaction studies identified race specific sets of genes that best discriminate between asthmatic children and non-allergic controls.
We identified IL4 as having a role in asthma susceptibility in both African American and Caucasian children. However, while IL4 SNPs were associated with asthma in asthmatic children with European and African ancestry, the relative contributions of the most replicated asthma-associated SNPs varied by ancestry. These data provides valuable insights into the pathways that may predispose to asthma in individuals with European vs. African ancestry.