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Epigenetic Changes Are Associated with Prenatal Air Pollution Exposure and Autism-Related Quantitative Traits

Poster Presentation
Friday, May 3, 2019: 11:30 AM-1:30 PM
Room: 710 (Palais des congres de Montreal)
C. Ladd-Acosta1, J. I. Feinberg1, F. Lurmann2, L. A. Croen3, I. Hertz-Picciotto4, C. J. Newschaffer5, A. P. Feinberg6, M. D. Fallin1 and H. E. Volk1, (1)Wendy Klag Center for Autism and Developmental Disabilities, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, (2)Sonoma Technology, Inc., Petaluma, CA, (3)Division of Research, Kaiser Permanente, Oakland, CA, (4)University of California at Davis, Davis, CA, (5)AJ Drexel Autism Institute, Philadelphia, PA, (6)Johns Hopkins University, Baltimore, MD
Background: Prenatal exposure to air pollution has been associated with increased risk of autism spectrum disorder (ASD). Identification of biologic mechanisms of this association can provide molecular targets for intervention. Evidence from the fields of environmental and autism epidemiology supports DNA methylation as a plausible biologic mechanism linking air pollution exposure with ASD risk.

Objectives: The main goal of this study was to identify DNA methylation changes, in two developmentally relevant tissue types, associated with prenatal exposure to air pollution and with autism-related quantitative traits. Secondary objectives included identifying sex-specific DNA methylation changes related to prenatal air pollution exposure and evaluate whether air pollutant related methylation changes show tissue-specificity or not.

Methods: Early Autism Risk Longitudinal Investigation (EARLI) is a US multi-site enriched-familial risk pregnancy cohort study. Genome-scale DNA methylation measurements for 133 placenta and 175 cord blood samples were obtained using the Infinium HumanMethylation450k platform. Ambient nitrogen dioxide (NO2) and ozone (O3) air pollutant exposure levels were estimated from prenatal address locations of EARLI mothers using inverse distance weighting via measurements from the Environmental Protection Agency’s monitoring network. ASD-related quantitative traits include the Social Responsiveness Scale (SRS), Vineland Adaptive Behavior Scales (VABS)-2 composite, and the Mullen Scales of Early Learning (MSEL) composite scores at 36 months. Bumphunting was performed to identify differentially methylated regions (DMRs) associated with prenatal O3 and NO2 exposures in each tissue and by sex, adjusting for technical and biological sources of variation. Permutation testing was applied and a family wise error rate (FWER) statistic was used to assess statistical significance. Exposure-associated DMRs were then examined for associations with 36 month outcomes.

Results: We identified 9 DMRs in either cord blood or placenta, including 6 sex-specific, associated with prenatal O3 or NO2 exposures. Among these 9 air pollution associated DMRs, 2 also showed a significant (FDR < 0.05) and 1 showed a suggestive (FDR < 0.10) difference in methylation associated with a poorer 36-month outcome and in a direction that is consistent with air pollution – outcome main effects. For example, increased prenatal exposure to NO2 and low VABS scores are both associated with a 9% loss of methylation in placenta, on average, at the ZNF442 locus. Formal mediation analyses are underway and will also be presented.

Conclusions: We observed locus and sex-specific methylation changes associated with prenatal NO2 and O3 exposures, providing potential biologic targets for a wide range of child health outcomes, including ASD. Associations, in the same direction, of some DMRs with both prenatal air pollutant exposure and quantitative traits, suggest DNA methylation may mediate the effects of prenatal air pollution exposure on child developmental function.

See more of: Epigenetics
See more of: Epigenetics