Will Carroll

Review article: Epigenetic control of fetal gene expression

Each differentiated cell type has its own epigenetic signature, which reflects its genotype, developmental history, and environmental influences, and is ultimately reflected in the phenotype of the cell and organism. Some cells undergo major epigenetic ‘reprogramming’ during fetal development. The proper, or improper, handling of these highly sensitive periods may have significant short‐term and long‐term effects on the newborn and his/her progeny. This review highlights the impact of environmental and nutritional factors on the epigenome and the potential effect of epigenetic dysregulation on maternal and fetal pregnancy outcomes, as well as possible long‐term implications.

Quantitative, high-resolution epigenetic profiling of CpG loci identifies associations with cord blood plasma homocysteine and birth weight in humans

Supplementation with folic acid during pregnancy is known to reduce the risk of neural tube defects and low birth weight. It is thought that folate and other one-carbon intermediates might secure these clinical effects via DNA methylation. We examined the effects of folate on the human methylome using quantitative interrogation of 27,578 CpG loci associated with 14,496 genes at single-nucleotide resolution across 12 fetal cord blood samples. Consistent with previous studies, the majority of CpG dinucleotides located within CpG islands exhibited hypo-methylation while those outside CpG islands showed mid-high methylation. However, for the first time in human samples, unbiased analysis of methylation across samples revealed a significant correlation of methylation patterns with plasma homocysteine, LINE-1 methylation and birth weight centile. Additionally, CpG methylation significantly correlated with either birth weight or LINE-1 methylation were predominantly located in CpG islands. These data indicate that levels of folate-associated intermediates in cord blood reflect their influence and consequences for the fetal epigenome and potentially on pregnancy outcome. In these cases, their influence might be exerted during late gestation or reflect those present during the peri-conceptual period.

Hydrogen cyanide as a biomarker for Pseudomonas aeruginosa in the breath of children with cystic fibrosis

Hydrogen cyanide (HCN) is emitted by Pseudomonas aeruginosa (PA) in vitro. We hypothesized that exhaled HCN could be measured using Selected Ion Flow Tube Mass Spectrometry (SIFT‐MS) and that concentrations would be higher in children with cystic fibrosis (CF) and PA infection than in children with asthma.

LINE-1 DNA methylation is inversely correlated with cord plasma homocysteine in man: A preliminary study

Folic acid supplementation during pregnancy has known beneficial effects. It reduces risk of neural tube defects and low birth weight. Folate and other one-carbon intermediates might secure these clinical effects via DNA methylation. However, most data on the effects of folate on the epigenome is derived from animal or in vitro models. We examined the relationship between cord blood methylation and maternal folic acid intake, cord blood folate and homocysteine using data from 24 pregnant women. Genome-wide methylation was determined by the level of methylation of LINE-1 repeats using Pyrosequencing. We show that cord plasma homocysteine (p = 0.001, r = -0.688), but not serum folate or maternal folic acid intake, is inverse correlated with LINE-1 methylation. This remained significant after correction for potential confounders (p = 0.004). These data indicate that levels of folate-associated intermediates in cord blood during late pregnancy have significant consequences for the fetal epigenome.

Asthma severity and atopy: how clear is the relationship?

Background: The relationship between asthma severity and atopy is complex. Many studies have failed to show significant relationships between clinical severity or lung function and markers of atopic sensitisation. Aim: To determine whether increasing asthma severity is related to atopic sensitisation in a population of children with asthma. Methods: A total of 400 children (7–18 years) with asthma were recruited as part of a multicentre study of the genetics of asthma. Detailed phenotypic data were collected on all participants. Associations between measures of asthma severity and atopic sensitisation were sought using multilevel models allowing variation at the individual and family level. Results: Children recruited to the study had a range of asthma severities, with just over a third having mild persistent asthma. The logarithm of total serum IgE was associated with increased asthma severity score, decreased FEV1, increased airways obstruction, risk of hospital admission, and inhaled steroid use. Increasing skin prick test reactivity to a panel of seven aeroallergens was associated with increased risk of hospital admission, use of an inhaled steroid, and airways obstruction. The results remained highly significant after corrections for age, gender, and birth order. Conclusions: In children with asthma, increasing atopy is associated with increasing asthma severity. However, the relationships between asthma severity and skin prick tests, and asthma severity and total serum IgE values, appear subtly different.

Effects of glutathione S‐transferase M1, T1 and P1 on lung function in asthmatic families

Rationale Previous data have suggested that glutathione‐S‐transferase (GST) genotypes are important in determining the rate of lung function growth in childhood. This effect was most marked in Caucasian children with asthma.

Randomized controlled trial of nebulized adrenaline in acute bronchiolitis

Use of both l‐epinephrine and racemic epinephrine (adrenaline) has improved clinical symptoms and composite respiratory scores in acute bronchiolitis. The objective of this randomized double‐blind placebo‐controlled study was to assess whether there was sufficient improvement in clinical state to reduce hospital admissions. Seventy‐five infants aged 1 month to 1 year with a clinical diagnosis of acute bronchiolitis were treated with either 2 ml of 1:1000 nebulized adrenaline or 2 ml of nebulized normal saline administered after baseline assessment and 30 min later. Clinical respiratory parameters were recorded at 15‐min intervals for a period of 2 h following the baseline assessment. Admission to hospital was the primary end‐point and changes in respiratory parameters were secondary end‐points. Fifty percent (19/38) of infants treated with adrenaline were discharged home compared with 38 percent (14/37) of those treated with saline. This 12 percent reduction in rate of admission is not statistically significant (95% CI of difference: −10% to 35%). There was no difference between treated and placebo groups in respiratory rate, oxygen saturation, heart rate or a composite respiratory distress score at 30, 60 or 120 min post‐treatment. In this study, nebulized epinephrine did not confer a significant advantage over nebulized saline in the emergency room treatment of acute bronchiolitis.

Maternal glutathione S-transferase GSTP1 genotype is a specific predictor of phenotype in children with asthma

Maternal factors are known to influence the heritability and expression of asthma and atopy. We report the association of maternal, paternal and proband GSTP1 genotype with lung function in 145 Caucasian children with asthma. GSTP1 Val105/Val105 and Ala114/Val114 genotypes in the child were associated with non‐significant increases in lung function (forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC) and the FEV1/FVC ratio). Paternal genotype had no influence on lung function in the child. In contrast, maternal GSTP1 Val105/Val105 genotype was significantly associated with offspring lung function and was strongly predictive of FEV1/FVC (Val105/Val105 105.2%, Ile105/Val105 and Ile105/Ile105 97.9% p = 0.006) and maternal GSTP1 Ala114/Val114 genotype was associated with significantly higher FEV1 (Ala114/Val114 109.0%, Ala114/Ala114 99.0% p = 0.008), and FEV1/FVC ratios (Ala114/Val114 104.1%, Ala114/Ala114 98.2% p = 0.04). The associations between maternal GSTP1 Val105/Val105 genotype and FEV1/FVC and maternal GSTP1 Ala114/Val114 genotype and FEV1 remained significant (p = 0.003 and p = 0.007) after correction for child and maternal atopic status, passive smoke exposure, smoking during pregnancy, individual and paternal GSTP1 genotype and was independent of transmission to the child. These data support the hypothesis that maternal GSTP1 genotype can act as a specific risk factor which has ex utero consequences for children with asthma. As a childs genotype is not independent of maternal genotype, effects seen in candidate gene studies may be due at least in part to this phenomenon.

Drug therapy in the management of acute asthma

If our management of children with asthma was optimal, there would be no need for this article as we would be able to prevent the development and progression of any asthma exacerbation. In reality, we are quite a long way from optimal care of childhood asthma in the UK and although hospital admissions for acute asthma are at last beginning to decline, having reached their peak in the late 1980s, acute asthma remains the most common reason for emergency admission to hospital.1 The vast majority of children respond well to treatment with oral steroids and inhaled bronchodilators, with deaths from childhood asthma remaining low: approximately 25 UK children die each year.2 However, identifiable causes of death include suboptimal routine and emergency care in a third to half of all children.3,4 The initial management of children with acute asthma has changed little over the last 20 years.5–7 However, data continue to emerge on how best to manage the small number of children who respond poorly to first-line treatment. This article aims to review the recent evidence (or highlight the lack of it) and gives suggestions for treatment strategies when faced with a child who is failing to respond. As background to this article, we interrogated the MEDLINE database for articles concerning “acute asthma” AND “treatment” OR “therapeutics”. By limiting the search to articles about children and excluding reviews, we initially retrieved 494 abstracts. For the sake of clarity we have attempted to exclude opinions and keep the evidence separate whenever possible. At the end of each section of the review we offer a brief description of our own views and experience in managing children with acute severe asthma with particular reference to the clinical cases described. A 4 year old child was admitted to the …

Combined influence of gene-specific cord blood methylation and maternal smoking habit on birth weight

AIM Evidence suggests that folic acid intake affects birth weight and that these effects may be mediated via the fetal epigenome. Our previous array data indicate that methylation in human cord blood at gene-specific CpGs is associated with birth weight percentile (BWP). Our aims were to investigate associations with BWP in specific CpGs identified by the array analysis in a significantly larger cohort and investigate the effects of other relevant factors on this association. MATERIALS & METHODS Methylation status was examined in candidate CpGs in 129 cord blood samples using Pyrosequencing™. The effects of other potentially important factors; maternal smoking, folate-related metabolite levels and genetic variation in the MTHFR gene, were examined. Linear and logistic regression analyses were used to identify relationships between BWP and methylation levels in the context of other key factors. RESULTS Increased cord methylation at CpGs in GSTM5 and MAP2K3 was associated with a reduced risk of having a birth weight below the 50th percentile (p = 0.010; odds ratio [OR]: 0.33 and p = 0.024; OR: 0.24, respectively) while higher methylation levels in APOB were associated with an increased risk (p = 0.023; OR: 2.56). Smoking during pregnancy modified the effect of methylation on BWP. Thus, compared with nonsmokers with a GSTM5 methylation level of >25% (median BWP: 54.7%), those who had smoked during pregnancy and whose GSTM5 methylation was <25% had the lowest median BWP (12.0%; p = 0.001). Furthermore, this latter group had the highest proportion of cases with BWPs below 50% (92.9 compared with 47.8% in nonsmokers with a GSTM5 methylation level of >25%; p = 0.013; OR: 14.2). Similar results were identified for MAP2K3, while the link with APOB reflected the inverse relationship between methylation at this locus and BWP. CONCLUSION Our data suggest that gene-specific methylation of cord DNA is associated with BWP and this methylation provides an additional effect on BWP to that of smoking during pregnancy.