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Open Access Publications from the University of California

Placental methylome analysis from a prospective autism study.

  • Author(s): Schroeder, Diane I
  • Schmidt, Rebecca J
  • Crary-Dooley, Florence K
  • Walker, Cheryl K
  • Ozonoff, Sally
  • Tancredi, Daniel J
  • Hertz-Picciotto, Irva
  • LaSalle, Janine M
  • et al.

BACKGROUND:Autism spectrum disorders (ASD) are increasingly prevalent neurodevelopmental disorders that are behaviorally diagnosed in early childhood. Most ASD cases likely arise from a complex mixture of genetic and environmental factors, an interface where the epigenetic marks of DNA methylation may be useful as risk biomarkers. The placenta is a potentially useful surrogate tissue characterized by a methylation pattern of partially methylated domains (PMDs) and highly methylated domains (HMDs) reflective of methylation patterns observed in the early embryo. METHODS:In this study, we investigated human term placentas from the MARBLES (Markers of Autism Risk in Babies: Learning Early Signs) prospective study by whole genome bisulfite sequencing. We also examined the utility of PMD/HMDs in detecting methylation differences consistent with ASD diagnosis at age three. RESULTS:We found that while human placental methylomes have highly reproducible PMD and HMD locations, there is a greater variation between individuals in methylation levels over PMDs than HMDs due to both sampling and individual variability. In a comparison of methylation differences in placental samples from 24 ASD and 23 typically developing (TD) children, a HMD containing a putative fetal brain enhancer near DLL1 was found to reach genome-wide significance and was validated for significantly higher methylation in ASD by pyrosequencing. CONCLUSIONS:These results suggest that the placenta could be an informative surrogate tissue for predictive ASD biomarkers in high-risk families.

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