The overarching goal of the proposed research is to investigate the association of prenatal exposure to EDCs: phthalates and BPA) with DNA methylation patterns and childhood obesity using novel epigenomic approaches. The program provides mentored training (K99) and a research phase (R00) for Allan Just PhD, an environmental epidemiologist, to become an independent academic investigator in epigenetic epidemiology. Dr. Just will receive training and guidance from a mentoring team of internationally recognized scientists with specializations in environmental and epigenetic epidemiology, pediatrics, and biostatistics, including Dr. Andrea Baccarelli, Dr. Robert Wright and Dr. Xihong Lin. Prior research has demonstrated that human prenatal exposures can alter the fetal epigenome, and animal models have shown that phthalates and BPA impact methylation and obesity risk in the offspring. The proposed research uses methylation microarrays and new sequencing-based technologies to investigate methylation patterns in the umbilical cord blood of two cohorts of human children. An epigenome-wide methylation microarray (Illumina Human Methylation 450K BeadChip), already being conducted on umbilical cord blood DNA from 120 children, will measure methylation in 480K individual sites spanning almost all known genes. Statistical models will relate these methylation measures to prenatal EDC exposures and to measures of obesity at age 4. These models use new statistical approaches that account for multiple comparisons and reflect the dependence between methylation sites within the genome. Replication in an independent cohort (n=150), using the same design, assures that findings are consistent and generalizable. All samples and obesity measures are already collected or ongoing in the two cohorts (called PROGRESS and PRISM) under existing grants led by members of the mentoring team. In the R00 phase, a novel technique, targeted enrichment, which has not yet been applied in large-scale epigenetic epidemiologic studies, will be used in conjunction with bisulfite treatment and next generation sequencing; this approach will generate new high resolution measures of all methylation sites in identified regions of interest. This research should provide greater power to detect associations between EDC exposures, methylation patterns, and obesity in children. This approach may also contribute to future epigenetic epidemiological studies by comparing the contributions of the sparser, genome- wide platform with patterns found by the novel high density sequencing-based measures. This research is important because it quantifies the extent to which prenatal exposures to EDCs are associated with methylation patterns in human fetal tissue, and then links these findings to childhood obesity. Another innovation is its techniques to conduct epidemiologic studies with two different methylation technologies. The proposed work trains Dr. Just in state-of-the-art epigenomic approaches and in this way contributes to understanding of the impact of endocrine disruptors on children's health.