Dataset Information

Effects of Cadmium Exposure on DNA Methylation at Imprinting Control Regions and Genome-Wide in Mothers and Newborn Children.

ABSTRACT: Background: Imprinted genes are defined by their preferential expression from one of the two parental alleles. This unique mode of gene expression is dependent on allele-specific DNA methylation profiles established at regulatory sequences called imprinting control regions. These loci are frequently used as biosensors to study how environmental exposures affect methylation and transcription. However, a critical unanswered question is whether they are more, less or equally sensitive to environmental stressors as the rest of the genome. Objectives: Using cadmium exposure in humans as a model, we determined the relative sensitivity of imprinting control regions to perturbation of methylation compared to similar, non-imprinted loci in the genome. Methods: We assayed DNA methylation genome-wide using bisulfite sequencing of newborn cord blood and maternal blood samples selected on the basis of maternal blood cadmium levels. Differentially methylated regions associated with cadmium exposure were identified. Results: In newborn cord blood and maternal blood, 641 and 1945 cadmium-associated differentially methylated regions were identified, respectively. These were strongly enriched at maternally-methylated imprinting control regions when compared to similar loci in newborn cord blood (P = 5.64E-8) and maternal blood (P = 6.22E-14), suggesting an increased sensitivity for imprinting control regions to cadmium. Genome-wide, methylation changes were enriched in maternal blood at genes implicated in body mass index (P = 2.0E-5), blood pressure (P = 3.8E-5) and body weight (P = 1.4E-3), with similar trends for metabolic and cardiovascular functions in cord blood, suggesting that epigenetic changes may contribute to the etiology of cadmium-associated diseases. Conclusions: We present the first global nucleotide-resolution DNA methylation profile associated with cadmium exposure in humans. We identify imprinting control regions as hotspots for perturbation by cadmium, possibly due to their unique modes of regulation, motivating further study of these loci to provide insight into the mechanisms of cadmium action.

ORGANISM(S): Homo sapiens

PROVIDER: GSE123279 | GEO | 2018/12/04

REPOSITORIES: GEO

ACCESS DATA

Similar Datasets

Project description:Genomic imprinting is a mechanism in which the expression of genes varies depending on their parent-of-origin. Imprinting occurs through differential DNA methylation and histone modifications on the two parental alleles, with most imprinted genes marked by CpG-rich differentially methylated regions (DMRs). DNA methylation profiling in cases of uniparental disomy (UPD) provides a unique system permitting the study of DNA derived from a single parent (PMID: 20631049). Approximately 70 human imprinted genes have been described, and imprinted loci have been associated with diseases such as diabetes and cancer. We profiled parent of origin DNA methylation marks to find novel imprinted loci. Methods: We have an unprecedented collection of whole blood DNA from XX patients with UPD covering 18 different chromosomes, allowing for the efficient detection of DMRs associated with imprinted genes for 84% of the human genome. Our study is complimented with Ovarian Teratoma DNA (maternal DNA) and Complete hydatidiform Mole (paternal DNA). DNA methylation was profiled using Illumina Infinium 450K Methylation BeadArrays. Imprinted DMRs were defined by sites at which the maternal and paternal methylation levels diverged significantly from the biparental average. We confirmed novel DMRs by bisulfite sequencing of informative trios and SequenomEpiTYPER assays. Allelic specific gene expression studies were also performed by RNA sequencing in independent biparental controls. Findings: Our results provide for the first comprehensive map of the human imprintome, doubling the number of known imprinted regions. We identified a total of 71 DMRs, 41 of which were novel. 27 novel DMRs were maternally methylated and 14 were paternally methylated. We identified DMRs on chromosomes 5, 21 and 22 previously considered devoid of imprinting, highlighting potential parent-of-origin effects in chromosomal aneuploidies such as Down syndrome. We also found DMRs in genes associated with Schizophrenia and epilepsy. Interpretation: Our data provide the first comprehensive genome-wide map of imprinted sites in the human genome, and provide novel insights into potential parent-of-origin effects in human disorders. 66 UPD samples analyzed in total, From each individual, whole bllod DNA was extracted and global DNA methylation levels were assessed using Illumina Infinium HumanMethylation450 BeadChip.

Project description:The maternal and paternal copies of the genome are both required for mammalian development and this is primarily due to imprinted genes, those that are mono-allelically expressed based on parent-of-origin. Typically, this pattern of expression is regulated by differentially methylated regions (DMRs) that are established in the germline and maintained after fertilisation. There are a large number of germline DMRs that have not yet been associated with imprinting and their function in development is unknown. In this study, we developed a genome-wide approach to identify novel imprinted DMRs, specifically in the human placenta, and investigated the dynamics of imprinted DMRs during development in somatic and extra-embryonic tissues. DNA methylation was evaluated using the Illumina HumanMethylation450 array in 116 human tissue samples, publically available reduced representation bisulfite sequencing in the human embryo and germ cells, and targeted bisulfite sequencing in term placentas. 43 known and 101 novel imprinted DMRs were identified in the human placenta, by comparing methylation between diandric and digynic triploids and female and male gametes. 72 novel DMRs showed a pattern consistent with placental-specific imprinting and this mono-allelic methylation was entirely maternal in origin. Strikingly, these DMRs exhibited polymorphic imprinted methylation specifically in placenta. These data suggest that imprinting in human development is far more extensive and dynamic than previously reported and that the placenta preferentially maintains maternal germline-derived DNA methylation For the identification of imprinted DMRs in the placenta, chorionic villous samples from 5 diandric and 5 digynic triploids pregnancies were assayed, along with a pooled sample of complete hydatiform moles (CHM). Placental chorionic villous samples (n=63) included 29 control pregnancies delivered at term, while the remaining 34 were delivered preterm or miscarried, or had abnormal MSS results, IUGR or LOPET. The preterm births were associated with one or more of: preterm labour, premature rupture of membranes (PROM), chorioamnionitis, placental abruption, and incompetent cervix. All samples were determined to be chromosomally normal using standard karyotyping or comparative genome hybridization, as previously described (Robinson et al. 2010). Two to four independent sites were taken from each placenta and after DNA extraction from chorionic villous, the DNA was pooled before being utilized in this study. Thirty-three fetal tissues, including brain (n=8), spinal cord (n=7), muscle (n=9), and kidney (n=9) were collected from second trimester foetuses, as previously described (Price et al. 2012). Adult female whole blood samples (n=10) were collected from control women. Extra-embryonic cell types (n=19), including cord blood (embryonic), cord, amniotic membrane, chorionic membrane, 1st, 2nd and 3rd trimester trophoblast and mesenchyme, and decidua (maternal), were isolated from control placental samples.

Project description:Background: Maternal smoking during pregnancy is a major risk factor for adverse health outcomes. The main objective of the study was to assess the impact of in utero tobacco exposure on DNA methylation in children born at term with appropriate weight at birth. Methods: Twenty mother-newborn dyads, after uncomplicated pregnancies, in the absence of perinatal illness were included. All mothers were healthy with no cardiovascular risk factors, except for the associated risks among those mothers who smoked. Umbilical cord blood (for methylation arrays) and maternal peripheral venous blood (for cotine level measurement) were collected and an epigenome-wide association study was performed using a 450K epigenome-wide scan (Illumina Infinium HumanMethylation 450BeadChip) with adjustment to normalize the DNA methylation for data cell variability in whole blood. Results: The maternal plasmatic cotinine levels ranged from 10.70-115.40 ng/ml in the exposed group to 0-0.59 ng/ml in the non-exposed group. After adjusting for multiple comparisons in 427102 probes, statistically significant differences for 31 CpG sites, associated to 25 genes were observed. There was a greater than expected proportion of statistically-significant loci located in CpG islands (FisherM-bM-^@M-^Ys exact test, p=0.029) and of those CpG islands, 90.3% exhibit higher methylation levels in the exposed group. The most striking and significant CpG site, cg05727225, is located in the chromosome 11p15.4, within the adrenomedullin gene. Conclusions: In utero tobacco exposure, even in the absence of fetal growth restriction, may alter the epigenome, contributing to global DNA hypomethylation. Therefore, DNA status can be used as a biomarker of prenatal insults. Considering the possibility to reverse epigenetic modifications, a window of opportunity exists to change the programmed chronic disease. Twenty mother-newborn dyads, after uncomplicated pregnancies, in the absence of perinatal illness were included. All mothers were healthy with no cardiovascular risk factors, except for the associated risks among those mothers who smoked. Umbilical cord blood were collected and an epigenome-wide association study was performed using a 450K epigenome-wide scan (Illumina Infinium HumanMethylation 450BeadChip) with adjustment to normalize the DNA methylation for data cell variability in whole blood.

Project description:The effect of pre and periconceptional multiple micronutrient supplementation on methylation of CpG loci within CpG islands associated with 14,000 genes across the human genome has been investigated in the offspring of a cohort of Gambian women participating in a controlled double blinded trial. Methylation levels in placebo and micronutrient supplemented cohorts were compared in genomic DNA from cord blood (35 placebo and 21 micronutrient supplemented) and in circulating blood samples (14 placebo and 9 micronutrient supplemented) drawn from the same cohort at 9 months old. A small number of differentially methylated CpG loci were identified in cord blood (14 in males and 21 in females) and a larger number in the 9 month infant comparison (108 in males and 106 in females). Seven differentially methylated loci in males and 8 in females persisted from cord to infant. These findings indicate that micronutrient supplementation pre-conception or early in embryonic development is potentially associated with programming of gene activity at birth, which is maintained into early infanthood. Strikingly, the loci affected by micronutrient supplementation differed between males and females, with no shared changes in cord blood and only 5 shared changes at 9 months. Additionally, a large number of CpG loci showed variation in methylation level when comparing 9-month samples to cord blood samples. These postnatal changes were more consistent between sexes, with 85% of female alterations being found as a subset of male changes in the placebo cohort and 62% of the female changes shared with males in the supplemented cohort. Taken together, the results suggest that there is a core developmental program shared between the sexes that is unaffected by nutrient supplementation, but that there are also sex-specific developmental changes which are altered under conditions of micronutrient supplementation and deficiency. Bisulphite converted DNA from 59 cord (36 placebo and 23 treated) and 25 infant peripheral blood (15 placebo and 10 treated) samples were hybridised to the Illumina Infinium 27k Human Methylation Beadchip v1.2. (For further analysis, five were excluded during quality control leaving 56 cord (35 placebo and 21 treated) and 23 infant peripheral blood (14 placebo and 9 treated) samples. Full data set of 84 samples were submitted to GEO)

Dataset Information

Effects of Cadmium Exposure on DNA Methylation at Imprinting Control Regions and Genome-Wide in Mothers and Newborn Children.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure