Background: The presence of allergic sensitization has a major influence on the development and course of common childhood conditions such as asthma and rhinitis. The etiology of allergic sensitization is poorly understood, and its underlying biological mechanisms are not well established. Several studies showed that DNA methylation (DNAm) at some CpGs is associated with allergic sensitization. However, no studies have focused on the critical adolescence period. Methods: We assessed the association of pre- and postadolescence genome-wide DNAm with allergic sensitization against indoor, outdoor and food allergens, using linear mixed models. We hypothesized that DNAm is associated with sensitization in general, and with poly-sensitization status, and these associations are age- and gender-specific. We tested these hypotheses in the IoW cohort (n = 376) and examined the findings in the BAMSE cohort (n = 267). Results: Via linear mixed models, we identified 35 CpGs in IoW associated with allergic sensitization (at false discovery rate of 0.05), of which 33 were available in BAMSE and replicated with respect to the direction of associations with allergic sensitization. At the 35 CpGs except for cg19210306 on C13orf27, a reduction in methylation among atopic subjects was observed, most notably for cg21220721 and cg11699125 (ACOT7). DNAm at cg10159529 was strongly correlated with expression of IL5RA in peripheral blood (P-value = 6.76 × 10−20). Three CpGs (cg14121142, cg23842695, and cg26496795) were identified in IoW with age-specific association between DNAm and allergic sensitization. Conclusion: In adolescence, the status of allergic sensitization was associated with DNAm differentiation and at some CpGs the association is likely to be age-specific.

BackgroundAdolescence is a period characterized by major biological development, which may be associated with changes in DNA methylation (DNA-M). However, it is unknown to what extent DNA-M varies from pre- to post-adolescence, whether the pattern of changes is different between females and males, and how adolescence-related factors are associated with changes in DNA-M.MethodsGenome-scale DNA-M at ages 10 and 18 years in whole blood of 325 subjects (n = 140 females) in the Isle of Wight (IOW) birth cohort was analyzed using Illumina Infinium arrays (450K and EPIC). Linear mixed models were used to examine DNA-M changes between pre- and post-adolescence and whether the changes were gender-specific. Adolescence-related factors and environmental exposure factors were assessed on their association with DNA-M changes. Replication of findings was attempted in the comparable Avon Longitudinal Study of Parents and Children (ALSPAC) cohort.ResultsIn the IOW cohort, after controlling for technical variation and cell compositions at both pre- and post-adolescence, 15,532 cytosine–phosphate–guanine (CpG) sites (of 400,825 CpGs, 3.88%) showed statistically significant DNA-M changes from pre-adolescence to post-adolescence invariant to gender (false discovery rate (FDR) = 0.05). Of these 15,532 CpGs, 10,212 CpGs (66%) were replicated in the ALSPAC cohort. Pathway analysis using Ingenuity Pathway Analysis (IPA) identified significant biological pathways related to growth and development of the reproductive system, emphasizing the importance of this period of transition on epigenetic state of genes. In addition, in IOW, we identified 1179 CpGs with gender-specific DNA-M changes. In the IOW cohort, body mass index (BMI) at age 10 years, age of growth spurt, nonsteroidal drugs use, and current smoking status showed statistically significant associations with DNA-M changes at 15 CpGs on 14 genes such as the AHRR gene. For BMI at age 10 years, the association was gender-specific. Findings on current smoking status were replicated in the ALSPAC cohort.ConclusionAdolescent transition is associated with changes in DNA-M at more than 15K CpGs. Identified pathways emphasize the importance of this period of transition on epigenetic state of genes relevant to cell growth and immune system development.

Little is known about whether DNA methylation (DNAm) of cytosine-phosphate-guanine (CpG) sites at birth predicts patterns of lung function development. We used heel prick DNAm from the F1-generation of Isle of Wight birth cohort (IOWBC-F1) for discovery of CpGs associated with lung function trajectories (Forced Expiratory Volume, Forced Vital Capacity, their ratio, and Forced Expiratory Flow at 25–75%) over the first 26 years, stratified by sex. We replicated the findings in the Avon Longitudinal Study of Parents and Children (ALSPAC) using cord blood DNAm.Epigenome-wide screening was applied to identify CpGs associated with lung function trajectories in 396 boys, and 390 girls of IOWBC-F1. Replication in ALSPAC focused on lung function at ages 8, 15 and 24 years. Statistically significantly replicated CpGs were investigated for consistency in direction of association between cohorts, stability of DNAm over time in IOWBC-F1, relevant biological processes, and for association with gene expression (n=161) in IOWBC F2-generation (IOWBC-F2).Differential DNAm of 8 CpGs on genes GLUL, MYCN, HLX, LHX1, COBL, COL18A1, STRA6, and WNT11 involved in developmental processes, were significantly associated with lung function in the same direction in IOWBC-F1 and ALSPAC, and showed stable patterns at birth, age 10 and 18 years between high and low lung function trajectories in IOWBC-F1. CpGs on LHX1 and COL18A1 were linked to gene expression in IOWBC-F2.In two large cohorts, novel DNAm at birth were associated with patterns of lung function in adolescence and early adulthood providing possible targets for preventative interventions against adverse pulmonary function development.

Immunoglobulin E (IgE) is known to play an important role in allergic diseases. Epigenetic traits acquired due to modification of deoxyribonucleic acid (DNA) methylation (DNAm) in early life may have phenotypic consequences through their role in transcriptional regulation with relevance to the developmental origins of diseases including allergy. However, epigenome-scale studies on the longitudinal association of cord blood DNAm with IgE over time are lacking. Our study aimed to examine the association of DNAm at birth with childhood serum IgE levels during early life. Genome-scale DNAm and total serum IgE measured at birth, 5, 8, and 11 years of children in the Taiwan Maternal and Infant Cohort Study were included in the study in the discovery stage. Linear mixed models were implemented to assess the association between cord blood DNAm at ~310K 5′-cytosine-phosphate-guanine-3′ (CpG) sites with repeated IgE measurements, adjusting for cord blood IgE. Identified statistically significant CpGs (at a false discovery rate, FDR, of 0.05) were further tested in an independent replication cohort, the Isle of Wight (IoW) birth cohort. We mapped replicated CpGs to genes and conducted gene ontology analysis using ToppFun to identify significantly enriched pathways and biological processes of the genes. Cord blood DNAm of 273 CpG sites were significantly (FDR = 0.05) associated with IgE levels longitudinally. Among the identified CpGs available in both cohorts (184 CpGs), 92 CpGs (50%) were replicated in the IoW in terms of consistency in direction of associations between DNA methylation and IgE levels later in life, and 16 of the 92 CpGs showed statistically significant associations ( P < .05). Gene ontology analysis identified 4 pathways (FDR = 0.05). The identified 16 CpG sites had the potential to serve as epigenetic markers associated with later IgE production, beneficial to allergic disease prevention and intervention.