Biology subjects

Symeonides, C.

Publications and source records attributed to Symeonides, C..

3 recordsLinked to original sources

bioRxiv2025

Prenatal Environmental Determinants of Aromatase Brain-Promoter Methylation in Cord Blood: Chemical, Airborne, Pharmacological, and Nutritional Factors

Aromatase, an enzyme encoded by the gene CYP19A1, plays central roles in neurodevelopment. In the brain, its function is to convert androgens into neuroestrogens, ensuring balanced hormonal signalling. Both animal experiments and human studies have shown that, in males, disruption of aromatase, either genetically or epigenetically, can increase symptoms of autism. Prenatal exposure to bisphenol A (BPA), a common plastic chemical, can increase levels of DNA methylation--a key epigenetic modification--at the brain-specific CYP19A1 promoter, P1.f, reducing CYP19A1 expression. However, the extent to which other neurodevelopmentally relevant environmental exposures influence P1.f methylation remains unclear. Here, in the Barwon Infant Study (BIS) birth cohort (N = 906), we analysed the association between 25 prenatal exposures (from five classes previously linked to neurodevelopmental outcomes: manufactured chemicals, air pollution, and pharmacological, nutrition and sunlight-related factors) and methylation of the CYP19A1 P1.f promoter using Weighted Quantile Sum (WQS) regression. We found that the WQS mixture index, a weighted combination of the prenatal exposures, was positively associated with higher P1.f methylation (Adjusted Mean Difference (AMD) = 0.712 (95% CI 0.11, 1.315), p = 0.021), indicating reduced brain aromatase activity. Prenatal exposures with the strongest contribution to the mixture effect included bisphenols (including BPA), reduced sunlight, household mould, phthalates, low folate intake, and air pollution. These findings highlight epigenetic modification of the aromatase gene as a biologically plausible, convergent mechanism through which multiple environmental risk factors for autism may exert effects.

genomics↗

bioRxiv2025

Prenatal DEHP plastic chemical exposure increases the likelihood of child autism and ADHD symptoms through epigenetic programming

Increasing evidence implicates prenatal exposure to di-(2-ethylhexyl) phthalate (DEHP), a common endocrine-disrupting plastic chemical, in autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD). However, the underlying mechanisms are poorly understood. Here we examined whether cord blood DNA methylation, a key epigenetic marker, mediates the association between prenatal DEHP exposure and ASD/ADHD symptoms in 847 children enrolled in the Barwon Infant Study. ASD and ADHD are complex phenotypes characterised by differences at the gene regulatory network and neuronal circuit level, where heterogeneous genetic and environmental risk factors converge. Accordingly, we employed a data-driven computational strategy that helped elucidate broader functional epigenetic signatures of ASD and ADHD elicited by DEHP exposure. This included (1) a methylation profile score for DEHP exposure (MPSDEHP), and (2) an analysis of co-methylated gene networks. Causal mediation analysis demonstrated that both MPSDEHP and a DEHP-associated network of co-methylated genes mediated the effect of DEHP exposure on increased ASD and ADHD symptoms at ages 2 and 4 years (proportion of effect mediated ranged from 0.21 to 0.80). The co-methylation network was enriched for neural cell-type markers, ASD risk genes (including FOXP1, SHANK2, and PLXNB1), and targets of endocrine receptors previously linked to DEHP (including targets of the estrogen receptor ER and the glucocorticoid receptor GR), providing biological plausibility. We validated key results in independent blood (n=66) and postmortem brain (n=40) DNA methylation datasets. These findings provide mechanistic evidence linking DEHP to ASD and ADHD symptoms and reinforce growing concerns regarding the risks of prenatal exposure.\n\nSignificanceExposure to endocrine-disrupting plastic chemicals has been linked to adverse neurodevelopment, but the underlying biological mechanisms remain unclear. We demonstrate that prenatal exposure to di-(2-ethylhexyl) phthalate (DEHP), a common plasticizer, increases autism and ADHD symptoms through alterations in DNA methylation, a key epigenetic regulator of gene activity. Using birth cohort data, we identify epigenetic signatures of prenatal DEHP exposure, including alterations in an endocrine-related co-methylation network enriched for neural cell-type markers and known autism-associated genes. These signatures mediate the effects of DEHP on autism and ADHD symptoms and are also associated with autism in external blood and postmortem-brain datasets, providing independent validation. This causal evidence further underscores concerns regarding the consequences of prenatal plastic-chemical exposure on the developing brain.

neuroscience↗

bioRxiv2022

Genomic contributions to infant and toddler vocabulary scores: Implications for association with health-, cognition- and behaviour-related outcomes

BackgroundThe number of words children produce (expressive vocabulary) and understand (receptive vocabulary) changes rapidly during early development, partially due to genetic factors, although mechanisms are not well understood. Here, we performed a meta-genome-wide association study within the EAGLE consortium and investigated polygenic overlap with later-life traits, including Attention-Deficit/Hyperactivity Disorder (ADHD) and cognition. MethodsWe studied 37,913 parent-reported vocabulary size measures (English, Dutch, Danish) for 17,298 children of European descent. Meta-analyses were performed for early-phase expressive (infancy, 15-18 months), late-phase expressive (toddlerhood, 24-38 months) and late-phase receptive (toddlerhood, 24-38 months) vocabulary. Subsequently, we estimated Single-Nucleotide Polymorphism heritability (SNP-h2), genetic correlations (rg) and modelled underlying genetic factor structures with multivariate models. ResultsContributions of common genetic variation to early-life vocabulary were modest (SNP-h2: 0.08(SE=0.01) to 0.24(SE=0.03)) and multi-factorial. Genetic overlap between infant expressive and toddler receptive vocabulary was near zero (rg=0.07(SE=0.10)), although both measures were genetically related to toddler expressive vocabulary (rg=0.69(SE=0.14) and rg=0.67(SE=0.16), respectively). Consistently, polygenic association patterns with later-life traits differed: Genetic links with cognition emerged only in toddlerhood (e.g. toddler receptive vocabulary and intelligence: rg=0.36(SE=0.12)), despite comparable study power for infant measures. Furthermore, increased polygenic ADHD risk was associated with larger infant expressive vocabulary (rg=0.23(SE=0.08)), as confirmed by ADHD-symptom-based follow-up analyses in the Avon Longitudinal Study of Parents and Children (ALSPAC-rg=0.54(SE=0.26)). Genetic relationships with toddler receptive vocabulary were, however, opposite (ALSPAC-rg=-0.74(SE=0.23)), highlighting developmental changes in genetic architectures. ConclusionsMultiple genetic components contribute to early-life vocabulary development, shaping polygenic association patterns with later-life ADHD symptoms and cognition.

genomics↗