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Prenatal lead exposure is associated with decreased cord blood DNA methylation of the glycoprotein VI gene involved in platelet activation and thrombus formation

ABSTRACT: Early-life lead exposure impairs neurodevelopment and later exposure affects the cardiovascular system. Lead has been associated with reduced global 5-methylcytosine DNA methylation, suggesting that lead toxicity acts through epigenetic mechanisms. The objective of this study is to clarify how early life lead exposure alters DNA methylation of specific genes, using an epigenomic approach. We measured lead concentrations in urine (gestational week, GW, 8) and erythrocytes (GW 14), using ICP-MS, for 127 pregnant mothers recruited in the MINIMat food and supplementation cohort in rural Bangladesh. Cord blood DNA methylation was analyzed with the Infinium HumanMethylation450K BeadChip and top sites were validated by methylation-sensitive high-resolution melt curve analysis. Maternal urinary lead concentrations (divided into quartiles) showed significant (after adjustment for FDR) inverse associations with methylation at nine CpGs. Three of these sites were in the 5’ end, including the promoter, of glycoprotein IV (GP6); cg18355337 (q=0.029, β=-0.30), cg25818583 (q=0.041, β=-0.18) and cg23796967 (q=0.047, β=-0.17). The methylation in another CpG site in GP6 was close to significant (cg05374025, q=0.057, β=-0.23). The erythrocyte lead concentrations (divided into quartiles) were also inversely associated with CpG methylation in GP6, although this was not statistically significant after FDR-adjustments. Eight CpG sites in GP6 constituted a differentially methylated region in relation to urinary lead (p=0.005, q=0.48) and erythrocyte lead (p=0.007, q=0.46). In conclusion, we found that moderate prenatal lead exposure appear to epigenetically affect GP6, a key component of platelet aggregation and thrombus formation, suggesting a novel link between early lead exposure and cardiovascular disease later in life.

PROVIDER: EGAS00001001575 | EGA |

REPOSITORIES: EGA

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Project description:Prenatal exposure to inorganic arsenic (iAs) is detrimental to the health of newborns and increases the risk of disease development later in life. Here we examined a subset of newborn cord blood leukocyte samples collected from mothers enrolled in the Biomarkers of Exposure to ARsenic (BEAR) pregnancy cohort in Gomez Palacio, Mexico who were exposed to a range of drinking water arsenic concentrations (0.456-236 µg/L). Changes in iAs-associated DNA 5-methyl cytosine methylation were assessed across 424,935 CpG sites representing 18,761 genes and were compared to corresponding expression levels and birth outcomes. In the context of arsenic exposure, a total of 2,705 genes were identified with iAs-associated differences in DNA methylation. Site-specific analyzes identified DNA methylation changes that were most predictive of gene expression levels. Specifically, CpG methylation within CpG islands positioned within the first exon and 200bp upstream of the transcription start site yielded the most significant association with gene expression levels. A set of 16 genes was identified with correlated iAs-associated changes in DNA methylation and mRNA expression and all were highly enriched for binding sites of the early growth response (EGR) and CCCTC-binding factor (CTCF) transcription factors. Furthermore, DNA methylation levels of seven of these genes were associated with differences in birth outcomes including gestational age, placental weight and head circumference. These data highlight the complex interplay between DNA methylation and functional changes in gene expression and health outcomes and underscore the need for functional analyzes coupled to epigenetic assessments. 48 DNA methylation profiles were obtained but only 38 samples corresponding to samples also analyzed for gene expression (see Rager 2014) were further normalized and used in the publication from the Biomarkers of Arsenic (BEAR) cohort were analyzed for DNA methylation profiles.

Project description:This data was generated by ENCODE. If you have questions about the data, contact the submitting laboratory directly (Florencia Pauli mailto:fpauli@hudsonalpha.org). If you have questions about the Genome Browser track associated with this data, contact ENCODE (mailto:genome@soe.ucsc.edu). This track is produced as part of the ENCODE project. The track displays the methylation status of specific CpG dinucleotides in the given cell types as identified by the Illumina Infinium Human Methylation 450 Bead Array platform (http://www.illumina.com/products/methylation_450_beadchip_kits.ilmn). In general, methylation of CpG sites within a promoter causes silencing of the gene associated with that promoter. The Infinium Human Methylation 450 platform uses bisulfite treated genomic DNA to assay the methylation status of more than 450,000 CpG sites covering all designatable RefSeq genes, including promoter, 5' and 3' regions, without bias against those lacking CpG islands. Additionally, the assay includes CpG islands and shores, CpG sites outside of CpG islands, non-CpG methylated sites identified in human stem cells, differentially methylated sites identified in tumor versus normal (multiple forms of cancer) and across several tissue types, CpG islands outside of coding regions, miRNA promoter regions, and disease-associated regions identified through GWAS. Detailed information for the CpG targets is in an CSV formatted spreadsheet in the supplemental directory (http://hgdownload-test.cse.ucsc.edu/goldenPath/hg19/encodeDCC/wgEncodeHaibMethyl450/supplemental/). For data usage terms and conditions, please refer to http://www.genome.gov/27528022 and http://www.genome.gov/Pages/Research/ENCODE/ENCODEDataReleasePolicyFinal2008.pdf Cells were grown according to the approved ENCODE cell culture protocols (http://hgwdev.cse.ucsc.edu/ENCODE/protocols/cell). Genomic DNA was isolated from each cell line with the QIAGEN DNeasy Blood & Tissue Kit according to the instructions provided by the manufacturer. DNA concentrations and a level of quality of each preparation was determined by fluorescence with the Qubit Fluorometer (Invitrogen). Genomic DNA was treated with sodium bisulfite, converting unmethylated cytosines of CpG dinucleotides into uracils; methylated cytosines did not get converted. After bisulfite treatment, the methylation status of a site was assayed by single base-pair extension with a Cy3 or Cy5 labeled nucleotide on oligo-beads specific for the methylated or unmethylated state. The bisulfite conversion reaction was done using the Zymo Research EZ-96 DNA Methylation Kit (http://www.zymoresearch.com/product/ez-96-dna-methylation-kit-d5003). One step of the protocol was modified. During the incubation, a 30 second 95oC denaturing step every hour was included to increase reaction efficiency as recommended by the Illumina Infinium Human Methylation27 protocol. The bead arrays were run according to the protocol provided by Illumina (http://hgdownload-test.cse.ucsc.edu/goldenPath/hg19/encodeDCC/wgEncodeHaibMethyl450/supplemental/wgEncodeHaibMethyl450IlluminaProtocol.pdf). A beta value was calculated for each CpG target with Illumina's Bead Studio software with the Methylation Module v3.2. Beta-value = intensity value from the methylated bead type/(intensity values from the methylated + intensity value from unmethylated bead types + 100). The data was then quality-filtered using p-values. Beta values with p-value greater than 0.01 are considered to fall below the minimum intensity and threshold are displayed as "NA". Any beta value equal to or greater than 0.6 was considered fully methylated. Any beta value equal to or less than 0.2 was considered to be fully unmethylated. Beta values between 0.2 and 0.6 were considered to be partially methylated. Score in the bed files is beta value x 1000

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Prenatal lead exposure is associated with decreased cord blood DNA methylation of the glycoprotein VI gene involved in platelet activation and thrombus formation

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