Fixed genomic variation explains only a small proportion of the risk of adiposity. In animal models, maternal diet alters offspring body composition, accompanied by epigenetic changes in metabolic control genes. Little is known about whether such processes operate in humans.
Research Design and Methods
Using Sequenom MassARRAY we measured the methylation status of 68 CpGs 5′ from five candidate genes in umbilical cord tissue DNA from healthy neonates. Methylation varied greatly at particular CpGs: for 31 CpGs with median methylation ≥5% and a 5-95% range ≥10% we related methylation status to maternal pregnancy diet and to child’s adiposity at age 9 years. Replication was sought in a second independent cohort.
In cohort 1, RXRA chr9:136355885+ and eNOS chr7:150315553+ methylation had independent associations with sex-adjusted childhood fat mass (exponentiated regression coefficient (β) 17% per standard deviation change in methylation (95% confidence interval (CI) 4 to 31%), P=0.009, n=64 and β=20% (9 to 32%), P<0.001, n=66, respectively) and %fat mass (β=10% (1 to 19%), P=0.023, n=64 and β=12% (4 to 20%), P=0.002, n=66, respectively). Regression analyses including sex and neonatal epigenetic marks explained >25% of the variance in childhood adiposity. Higher methylation of RXRA chr9:136355885+, but not of eNOS chr7:150315553+, was associated with lower maternal carbohydrate intake in early pregnancy, previously linked with higher neonatal adiposity in this population. In cohort 2, cord eNOS chr7:150315553+ methylation showed no association with adiposity, but RXRA chr9:136355885+ methylation showed similar associations with fat mass and %fat mass (β=6% (2 to 10%) and β=4% (1 to 7%), respectively, both P=0.002, n=239).
Our findings suggest a substantial component of metabolic disease risk has a prenatal developmental basis. Perinatal epigenetic analysis may have utility in identifying individual vulnerability to later obesity and metabolic disease.
Our previous work has shown associations between childhood adiposity and perinatal methylation status of several genes in umbilical cord tissue, including endothelial nitric oxide synthase (eNOS). There is increasing evidence that eNOS is important in bone metabolism; we therefore related the methylation status of the eNOS gene promoter in stored umbilical cord to childhood bone size and density in a group of 9-year old children.
We used Sequenom MassARRAY to assess the methylation status of 2 CpGs in the eNOS promoter, identified from our previous study, in stored umbilical cords of 66 children who formed part of a Southampton birth cohort and who had measurements of bone size and density at age 9 years (Lunar DPXL DXA instrument).
Percentage methylation varied greatly between subjects. For one of the two CpGs, eNOS chr7:150315553+, after taking account of age and sex there was a strong positive association between methylation status and the child’s whole body bone area (r=0.28,p=0.02), bone mineral content (r=0.34,p=0.005) and areal bone mineral density (r=0.34,p=0.005) at age 9 years. These associations were independent of previously documented maternal determinants of offspring bone mass.
Our findings suggest an association between methylation status at birth of a specific CpG within the eNOS promoter and bone mineral content in childhood. This supports a role for eNOS in bone growth and metabolism and implies that its contribution may at least in part occur during early skeletal development.
Epigenetic; methylation; umbilical cord; eNOS; DXA
Environmental factors during perinatal development may influence developmental plasticity and disease susceptibility via alterations to the epigenome. Developmental exposure to the endocrine active compound, bisphenol A (BPA), has previously been associated with altered methylation at candidate gene loci. Here, we undertake the first genome-wide characterization of DNA methylation profiles in the liver of murine offspring exposed perinatally to multiple doses of BPA through the maternal diet.
Using a tiered focusing approach, our strategy proceeds from unbiased broad DNA methylation analysis using methylation-based next generation sequencing technology to in-depth quantitative site-specific CpG methylation determination using the Sequenom EpiTYPER MassARRAY platform to profile liver DNA methylation patterns in offspring maternally exposed to BPA during gestation and lactation to doses ranging from 0 BPA/kg (Ctr), 50 μg BPA/kg (UG), or 50 mg BPA/kg (MG) diet (N = 4 per group). Genome-wide analyses indicate non-monotonic effects of DNA methylation patterns following perinatal exposure to BPA, corroborating previous studies using multiple doses of BPA with non-monotonic outcomes. We observed enrichment of regions of altered methylation (RAMs) within CpG island (CGI) shores, but little evidence of RAM enrichment in CGIs. An analysis of promoter regions identified several hundred novel BPA-associated methylation events, and methylation alterations in the Myh7b and Slc22a12 gene promoters were validated. Using the Comparative Toxicogenomics Database, a number of candidate genes that have previously been associated with BPA-related gene expression changes were identified, and gene set enrichment testing identified epigenetically dysregulated pathways involved in metabolism and stimulus response.
In this study, non-monotonic dose dependent alterations in DNA methylation among BPA-exposed mouse liver samples and their relevant pathways were identified and validated. The comprehensive methylome map presented here provides candidate loci underlying the role of early BPA exposure and later in life health and disease status.
Bisphenol A; DNA methylation; Environmental epigenomics; MethylPlex
Prenatal exposure both to maternal psychiatric illness and psychiatric medication has been linked with adverse child outcomes that affect physiological, emotional and psychiatric development. Studies suggest that epigenetic mechanisms, such as DNA methylation, may facilitate these effects. In this report, we explore the association between maternal psychiatric illness and treatment during pregnancy and neonatal DNA methylation patterns in a prospectively-characterized clinical cohort of 201 dyads. Associations between the percent of umbilical cord blood DNA methylated at 27,578 CpG sites and maternal psychiatric diagnosis, symptoms and antidepressant use were evaluated by fitting a separate linear mixed effects model for each CpG site. There were no significant changes in neonatal DNA methylation attributable to maternal psychiatric diagnosis or depressive symptoms during pregnancy. Exposure to an antidepressant medication was associated with differential methylation of CpG sites in TNFRSF21 and CHRNA2 (false discovery rate < 0.05), but the average difference in methylation for both CpG sites was less than 3% between each group. The results were not specific to type of antidepressant or duration of the exposure. This study suggests that there are no large effects of maternal psychiatric illness, depressive symptoms or prenatal exposure to antidepressants on neonatal DNA methylation. Delineation of the influence of maternal psychiatric illness and pharmacological exposures on the developing fetuses has critical implications for clinical care during pregnancy.
antidepressants; depressive symptoms; DNA Methylation; HumanMethylation27 BeadChip; Infinium; prenatal exposures
Perturbation of DNA methylation is frequent in cancers and has emerged as an important mechanism involved in tumorigenesis. To determine how DNA methylation is modified in the genome of primary glioma, we used Methyl-DNA immunoprecipitation (MeDIP) and Nimblegen CpG promoter microarrays to identify differentially DNA methylation sequences between primary glioma and normal brain tissue samples.
MeDIP-chip technology was used to investigate the whole-genome differential methylation patterns in glioma and normal brain tissues. Subsequently, the promoter methylation status of eight candidate genes was validated in 40 glioma samples and 4 cell lines by Sequenom's MassARRAY system. Then, the epigenetically regulated expression of these genes and the potential mechanisms were examined by chromatin immunoprecipitation and quantitative real-time PCR.
A total of 524 hypermethylated and 104 hypomethylated regions were identified in glioma. Among them, 216 hypermethylated and 60 hypomethylated regions were mapped to the promoters of known genes related to a variety of important cellular processes. Eight promoter-hypermethylated genes (ANKDD1A, GAD1, HIST1H3E, PCDHA8, PCDHA13, PHOX2B, SIX3, and SST) were confirmed in primary glioma and cell lines. Aberrant promoter methylation and changed histone modifications were associated with their reduced expression in glioma. In addition, we found loss of heterozygosity (LOH) at the miR-185 locus located in the 22q11.2 in glioma and induction of miR-185 over-expression reduced global DNA methylation and induced the expression of the promoter-hypermethylated genes in glioma cells by directly targeting the DNA methyltransferases 1.
These comprehensive data may provide new insights into the epigenetic pathogenesis of human gliomas.
DNA methylation; MiR-185; Glioma; DNMT1
The insulin-like growth factor 2 (IGF2) and H19 imprinted genes control growth and body composition. Adverse in-utero environments have been associated with obesity-related diseases and linked with altered DNA methylation at the IGF2/H19 locus. Postnatally, methylation at the IGF2/H19 imprinting control region (ICR) has been linked with cerebellum weight. We aimed to investigate whether decreased IGF2/H19 ICR methylation is associated with decreased birth and childhood anthropometry and increased contemporaneous adiposity.
DNA methylation in peripheral blood (n = 315) at 17 years old was measured at 12 cytosine-phosphate-guanine sites (CpGs), analysed as Sequenom MassARRAY EpiTYPER units within the IGF2/H19 ICR. Birth size, childhood head circumference (HC) at six time-points and anthropometry at age 17 years were measured. DNA methylation was investigated for its association with anthropometry using linear regression.
The principal component of IGF2/H19 ICR DNA methylation (representing mean methylation across all CpG units) positively correlated with skin fold thickness (at four CpG units) (P-values between 0.04 to 0.001) and subcutaneous adiposity (P = 0.023) at age 17, but not with weight, height, BMI, waist circumference or visceral adiposity. IGF2/H19 methylation did not associate with birth weight, length or HC, but CpG unit 13 to 14 methylation was negatively associated with HC between 1 and 10 years. β-coefficients of four out of five remaining CpG units also estimated lower methylation with increasing childhood HC.
As greater IGF2/H19 methylation was associated with greater subcutaneous fat measures, but not overall, visceral or central adiposity, we hypothesize that obesogenic pressures in youth result in excess fat being preferentially stored in peripheral fat depots via the IGF2/H19 domain. Secondly, as IGF2/H19 methylation was not associated with birth size but negatively with early childhood HC, we hypothesize that the HC may be a more sensitive marker of early life programming of the IGF axis and of fetal physiology than birth size. To verify this, investigations of the dynamics of IGF2/H19 methylation and expression from birth to adolescence are required.
Childhood; Fetal programming; DNA methylation; Insulin-like growth factor; Raine Study; Head circumference
Epigenetic changes such as aberrant DNA methylation and histone modification have been shown to play an important role in the tumorigenesis of malignant melanoma.
To identify novel tumor-specific differentially methylated regions (DMRs) in human malignant melanoma.
The aberrant methylation at 14 candidate human genomic regions identified through a mouse model study with quantitative DNA methylation analysis using the Sequenom MassARRAY system was performed.
The CpG island Exon 1 region of the Zygote arrest 1 (ZAR1) gene, which is responsible for oocyte-to-embryo transition, showed frequent aberrant methylation of 28 out of 30 (93%) melanoma surgical specimens, 16 of 17 (94%) melanoma cell lines, 0% of 4 normal human epidermal melanocyte (NHEM) cell lines, 0% of 10 melanocytic nevi and 100% of 51 various cancer cell lines. According to the real-time RT-PCR, the ZAR1 gene was overexpressed in part of the hypermethylated cell lines, while its low expression with bivalent histone methylation status was seen in unmethylated cell lines.
Our findings suggest that the ZAR1 intra-genic differentially methylated region would be a useful tumor marker for malignant melanoma and may be other type of cancers. The involvement of ZAR1 in the carcinogenesis of melanoma, still remains unclear, although we have examined tumorigenic capacities by exogenous full-length ZAR1 over-expression and siRNA knock-down experiments.
Background: Epigenetic modifications, such as DNA methylation, due to in utero exposures may play a critical role in early programming for childhood and adult illness. Maternal smoking is a major risk factor for multiple adverse health outcomes in children, but the underlying mechanisms are unclear.
Objective: We investigated epigenome-wide methylation in cord blood of newborns in relation to maternal smoking during pregnancy.
Methods: We examined maternal plasma cotinine (an objective biomarker of smoking) measured during pregnancy in relation to DNA methylation at 473,844 CpG sites (CpGs) in 1,062 newborn cord blood samples from the Norwegian Mother and Child Cohort Study (MoBa) using the Infinium HumanMethylation450 BeadChip (450K).
Results: We found differential DNA methylation at epigenome-wide statistical significance (p-value < 1.06 × 10–7) for 26 CpGs mapped to 10 genes. We replicated findings for CpGs in AHRR, CYP1A1, and GFI1 at strict Bonferroni-corrected statistical significance in a U.S. birth cohort. AHRR and CYP1A1 play a key role in the aryl hydrocarbon receptor signaling pathway, which mediates the detoxification of the components of tobacco smoke. GFI1 is involved in diverse developmental processes but has not previously been implicated in responses to tobacco smoke.
Conclusions: We identified a set of genes with methylation changes present at birth in children whose mothers smoked during pregnancy. This is the first study of differential methylation across the genome in relation to maternal smoking during pregnancy using the 450K platform. Our findings implicate epigenetic mechanisms in the pathogenesis of the adverse health outcomes associated with this important in utero exposure.
epigenetics; epigenome-wide; in utero; maternal smoking; methylation
Although a lower methylation level of whole genome has been demonstrated in Tetralogy of Fallot (TOF) patients, little is known regarding changes in specific gene DNA methylation profiles and the possible associations with TOF. In current study, the promoter methylation statuses of congenital heart defect (CHD) candidate genes were measured in order to further understand epigenetic mechanisms that may play a role in the development of TOF.
The methylation levels of CHD candidate genes were measured using the Sequenom MassARRAY platform. QRT-PCR was used to analyze the mRNA levels of CHD candidate genes in the right ventricular myocardium of TOF cases and normal controls.
Methylation status analysis was performed on the promoter regions of 71 CHD candidate genes (113 amplicons). We found significant differences in methylation status, between TOF cases and controls, in 26 amplicons (26 genes) (p < 0.05). Of the 26 amplicons, 17 were up regulated and 9 were down regulated. Additionally, 14 of them were located in the CpG islands, 7 were located in the CpG island shores, and 5 were covering the regions near the transcription start site (TSS). The methylation status was subsequently confirmed and mRNA levels were measured for 7 represented candidate genes, including EGFR, EVC2, NFATC2, NR2F2, TBX5, CFC1B and GJA5. The methylation values of EGFR, EVC2, TBX5 and CFC1B were significantly correlated with their mRNA levels (p < 0.05).
Aberrant promoter methylation statuses of CHD candidate genes presented in TOF cases may contribute to the TOF development and have potential prognostic and therapeutic significance for TOF disease.
DNA methylation; Congenital heart defect candidate genes; Tetralogy of Fallot
The inheritance of DNA methylation patterns is a popular theory to explain the influence of parental genetic and environmental factors on the phenotype of their offspring but few studies have examined this relationship in humans. Using 120 paired maternal-umbilical cord blood samples randomly selected from a prospective birth cohort in Bangladesh, we quantified DNA methylation by pyrosequencing seven CpG positions in the promoter region of p16, four CpG positions in the promoter region of p53, LINE-1 and Alu. Positive correlations were observed between maternal and umbilical cord blood at p16, LINE-1, and Alu but not p53. Multiple linear regression models observed a significant association between maternal and umbilical cord blood at LINE-1 and Alu (LINE-1: β = 0.63, p<0.0001; Alu: β = 0.28, p = 0.009). After adjusting for multiple comparisons, maternal methylation of p16 at position 4 significantly predicted methylation at the same position in umbilical cord blood (β = 0.43, p = <0.0001). These models explained 48%, 5% and 16% of the observed variability in umbilical cord %5mC for LINE-1, Alu and p16 at position 4, respectively. These results suggest that DNA methylation in maternal blood was correlated with her offspring at LINE-1, Alu, and p16 but not p53. Additional studies are needed to confirm whether these observed associations were due to the inheritance of epigenetic events or the shared environment between mother and fetus. Future studies should also use a multi-generational family-based design that would quantify both maternal and paternal contributions to DNA methylation in offspring across more than one generation.
Epigenetic regulation through DNA methylation may influence vulnerability to numerous disorders, including alcohol dependence (AD).
Peripheral blood DNA methylation levels of 384 CpGs in the promoter regions of 82 candidate genes were examined in 285 African Americans (AAs; 141 AD cases and 144 controls) and 249 European Americans (EAs; 144 AD cases and 105 controls) using Illumina GoldenGate Methylation Array assays. Association of AD and DNA methylation changes were analyzed using multivariate analyses of covariance with frequency of intoxication, sex, age and ancestry proportion as covariates. CpGs showing significant methylation alterations in AD cases were further examined in a replication sample (49 EA cases and 32 EA controls) using Sequenom’s MassARRAY EpiTYPER technology.
In AAs, two CpGs in two genes (GABRB3 and POMC) were hypermethylated in AD cases compared to controls (P≤0.001). In EAs, six CpGs in six genes (HTR3A, NCAM1, DRD4, MBD3, HTR2B and GRIN1) were hypermethylated in AD cases compared to controls (P≤0.001); CpG cg08989585 in the HTR3A promoter region showed a significantly higher methylation level in EA cases than in EA controls after Bonferroni correction (P=0.00007). Additionally, methylation levels of six CpGs (including cg08989585) in the HTR3A promoter region were analyzed in the replication sample. Although the six HTR3A promoter CpGs did not show significant methylation differences between EA cases and EA controls (P=0.067–0.877), the methylation level of CpG cg08989585 was non-significantly higher in EA cases (26.9%) than in EA controls (18.6%) (P=0.139).
The findings from this study suggest that DNA methylation profile appears to be associated with AD in a population-specific way and the predisposition to AD may result from a complex interplay of genetic variation and epigenetic modifications.
Illumna GoldenGate Methylation Array; Sequenom MassARRAY EpiTYPER; Promoter CpGs; Alcohol Dependence; Peripheral Blood DNA
Major depression, because of its recurring and life-threatening nature, is one of the top 10 diseases for global disease burden. Major depression is still diagnosed on the basis of clinical symptoms in patients. The search for specific biological markers is of great importance to advance the method of diagnosis for depression. We examined the methylation profile of 2 CpG islands (I and IV) at the promoters of the brain-derived neurotrophic factor (BDNF) gene, which is well known to be involved in the pathophysiology of depression. We analyzed genomic DNA from peripheral blood of 20 Japanese patients with major depression and 18 healthy controls to identify an appropriate epigenetic biomarker to aid in the establishment of an objective system for the diagnosis of depression. Methylation rates at each CpG unit was measured using a MassArray® system (SEQUENOM), and 2-dimensional hierarchical clustering analyses were undertaken to determine the validity of these methylation profiles as a diagnostic biomarker. Analyses of the dendrogram from methylation profiles of CpG I, but not IV, demonstrated that classification of healthy controls and patients at the first branch completely matched the clinical diagnosis. Despite the small number of subjects, our results indicate that classification based on the DNA methylation profiles of CpG I of the BDNF gene may be a valuable diagnostic biomarker for major depression.
Risk for adverse neonatal outcome increases with declining gestational age (GA), and changes in DNA methylation may contribute to the relationship between GA and adverse health outcomes in offspring. To test this hypothesis, we evaluated the association between GA and more than 27,000 CpG sites in neonatal DNA extracted from umbilical cord blood from two prospectively-characterized cohorts: (1) a discovery cohort consisting of 259 neonates from women with a history of neuropsychiatric disorders and (2) a replication cohort consisting of 194 neonates of uncomplicated mothers. GA was determined by obstetrician report and maternal last menstrual period. The associations between proportion of DNA methylated and GA were evaluated by fitting a separate linear mixed effects model for each CpG site, adjusting for relevant covariates including neonatal sex, race, parity, birth weight percentile and chip effects. CpG sites in 39 genes were associated with GA (false discovery rate <0.05) in the discovery cohort. The same CpG sites in 25 of these genes replicated in the replication cohort, with each association replicating in the same direction. Notably, these CpG sites were located in genes previously implicated in labor and delivery (e.g., AVP, OXT, CRHBP and ESR1) or that may influence the risk for adverse health outcomes later in life (e.g., DUOX2, TMEM176A and CASP8). All associations were independent of method of delivery or induction of labor. These results suggest neonatal DNA methylation varies with GA even in term deliveries. The potential contribution of these changes to clinically significant postnatal outcomes warrants further investigation.
genome-wide DNA methylation; gestational age; arginine vasopressin and oxytocin
Epigenetic modifications, such as cytosine methylation in CpG-rich regions, regulate multiple functions in mammalian development. Maternal nutrients affecting one-carbon metabolism during gestation can exert long-term effects on the health of the progeny. Using C57BL/6 J mice, we investigated whether the amount of ingested maternal folic acid (FA) during gestation impacted DNA methylation in the offspring’s cerebral hemispheres. Reduced representation bisulfite sequencing at single-base resolution was performed to analyze genome-wide DNA methylation profiles.
We identified widespread differences in the methylation patterns of CpG and non-CpG sites of key developmental genes, including imprinted and candidate autism susceptibility genes (P <0.05). Such differential methylation of the CpG and non-CpG sites may use different mechanisms to alter gene expressions. Quantitative real time reverse transcription-polymerase chain reaction confirmed altered expression of several genes.
These finding demonstrate that high maternal FA during gestation induces substantial alteration in methylation pattern and gene expression of several genes in the cerebral hemispheres of the offspring, and such changes may influence the overall development. Our findings provide a foundation for future studies to explore the influence of gestational FA on genetic/epigenetic susceptibility to altered development and disease in offspring.
Low birthweight, premature birth, intrauterine growth retardation, and maternal malnutrition have been related to an increased risk of cardiovascular disease, type 2 diabetes mellitus, obesity, and neuropsychiatric disorders later in life. Conversely, high birthweight has been linked to future risk of cancer. Global DNA methylation estimated by the methylation of repetitive sequences in the genome is an indicator of susceptibility to chronic diseases. We used data and biospecimens from an epigenetic birth cohort to explore the association between trajectories of fetal and maternal weight and LINE-1 methylation in 319 mother-child dyads. Newborns with low or high birthweight had significantly lower LINE-1 methylation levels in their cord blood compared to normal weight infants after adjusting for gestational age, sex of the child, maternal age at delivery, and maternal smoking during pregnancy (p = 0.007 and p = 0.036, respectively), but the magnitude of the difference was small. Infants born prematurely also had lower LINE-1 methylation levels in cord blood compared to term infants, and this difference, though small, was statistically significant (p = 0.004). We did not find important associations between maternal prepregnancy BMI or gestational weight gain and global methylation of the cord blood or fetal placental tissue. In conclusion, we found significant differences in cord blood LINE-1 methylation among newborns with low and high birthweight as well as among prematurely born infants. Future studies may elucidate whether chromosomal instabilities or other functional consequences of these changes contribute to the increased risk of chronic diseases among individuals with these characteristics.
Preeclampsia is a common and potentially lethal pregnancy disorder with lifelong increased risk of cardiovascular disease in survivors. Our prior global gene expression microarray analysis led to a novel set of 36 candidates in first trimester placentas of women who subsequently developed preeclampsia. In this report, we present preliminary studies demonstrating biomarkers of genotype and methylation variations in a subset of these candidate genes in maternal leukocyte and fetoplacental DNA of 28 case and 27 control dyads. We tested 84 single nucleotide polymorphisms (SNPs) using MassArray iPLEX and 50 CpG sites using EpiTYPER assays. Promising prediction modeling was identified with 25 SNPs selected using Fisher's exact tests (p≤0.05) and 20 CpG sites selected on fold change. Genotype Distribution Analysis identified SNP variations that differed between 9 paired cases versus paired controls. The findings validate the examined candidate genes and support feasibility of methods for further biomarker development. The integrative approach that was implemented begins to translate the 36 candidates toward clinical utility as a screening modality for preeclampsia.
Epidemiological and animal studies have shown that maternal diet can influence metabolism in adult offspring. However, the molecular mechanisms underlying these changes remain poorly understood. Here, we characterize the phenotypes induced by maternal obesity in a mouse model and examine gene expression and epigenetic changes induced by maternal diet in adult offspring.
We analyzed genetically identical male mice born from dams fed a high- or low-fat diet throughout pregnancy and until day 21 postpartum. After weaning, half of the males of each group were fed a high-fat diet, the other half a low-fat diet. We first characterized the genome-wide gene expression patterns of six tissues of adult offspring - liver, pancreas, white adipose, brain, muscle and heart. We then measured DNA methylation patterns in liver at selected loci and throughout the genome.
Maternal diet had a significant effect on the body weight of the offspring when they were fed an obesogenic diet after weaning. Our analyses showed that maternal diet had a pervasive effect on gene expression, with a pronounced effect in liver where it affected many genes involved in inflammation, cholesterol synthesis and RXR activation. We did not detect any effect of the maternal diet on DNA methylation in the liver.
Overall, our findings highlighted the persistent influence of maternal diet on adult tissue regulation and suggested that the transcriptional changes were unlikely to be caused by DNA methylation differences in adult liver.
Motivation: DNA cytosine methylation is an important epigenetic regulator, critical for mammalian development and the control of gene expression. Numerous techniques using either restriction enzyme or affinity-based approaches have been developed to interrogate cytosine methylation status genome-wide, however these assays must be validated by a more quantitative approach, such as MALDI-TOF mass spectrometry of bisulphite-converted DNA (commercialized as Sequenom's EpiTYPER assay using the MassArray system). Here, we present an R package (‘MassArray’) that assists in assay design and uses the standard Sequenom output file as the input to a pipeline of analyses not available as part of the commercial software. The tools in this package include bisulphite conversion efficiency calculation, sequence polymorphism flagging and visualization tools that combine multiple experimental replicates and create tracks for genome browser viewing.
Supplementary information: Supplementary data are available at Bioinformatics online.
Induction of an altered phenotype by prenatal under-nutrition involves changes in the epigenetic regulation of specific genes. We investigated the effect of feeding pregnant rats a protein-restricted (PR) diet with different amounts of folic acid on the methylation of individual CpG dinucleotides in the hepatic PPARα promoter in juvenile offspring, and the effect of the maternal PR diet on CpG methylation in adult offspring. Pregnant rats (n 5 / group) were fed 180g / kg casein (Control) or 90g / kg casein (PR) with 1mg / kg folic acid, or 90g / kg casein and 5 mg / kg folic acid (PRF). Offspring were killed on postnatal d34 (n 5 males and females / group) and d80 (n 5 males / group). Methylation of 16 CpG dinucleotides in the PPARα promoter was measured by pyrosequencing. Mean PPARα promoter methylation in the PR offspring (4.5%) was 26% lower than Controls (6.1%) due to specific reduction at CpG dinucleotides 2 (40%), 3 (43%), 4 (33%) and 16 (48 %) (P < 0.05). There was no significant difference in methylation at these CpGs between Control and PRF offspring. Methylation of CpGs 5 and 8 was higher (47% and 63%, respectively, P < 0.05) in the PRF offspring than Control or PR offspring. The methylation pattern in d80 PR offspring was comparable to d34 PR offspring. These data show for the first time that prenatal nutrition induces differential changes to the methylation of individual CpG dinucleotides in juvenile rats which persist in adults.
Fetal programming; epigenetic; rat; PPARα
Maternal diet during pregnancy has been linked to offspring adiposity, but it is unclear whether maternal polyunsaturated fatty acid (PUFA) status during pregnancy affects offspring body composition.
We investigated the associations between maternal plasma n-3 and n-6 PUFA status at 34 weeks gestation and offspring body composition.
Design and setting
A prospective UK population-based mother-offspring cohort: the Southampton Women’s Survey (SWS).
12583 non-pregnant women were recruited into the SWS, of which 1987 delivered a baby before 31st December 2003. 293 mother-child pairs had complete measurements of maternal plasma PUFA concentrations in late pregnancy and offspring body composition at ages 4 and 6 years.
Main Outcomes Measured
Offspring body composition by DXA, yielding fat mass(FM), lean mass(LM), percentage fat mass(%FM) and percentage lean mass(%LM).
Maternal plasma n-6 PUFA concentration positively predicted offspring fat mass at 4 years (β=0.14 SD/SD, p=0.01) and 6 years (β=0.11 SD/SD, p=0.04), but there was no association with offspring lean mass at either age (β=0.005 SD/SD, p=0.89 & β=0.008 SD/SD, p=0.81, respectively). Maternal plasma n-3 PUFA concentration displayed no associations with offspring fat mass at 4 years (β=0.057 SD/SD, p=0.34) or 6 years (β=0.069 SD/SD, p=0.21). Maternal plasma n-3 PUFA status positively correlated with offspring lean mass on univariate analysis (4yrs β=0.11, p=0.06; 6yrs β=0.14, p=0.02), however this was confounded by a positive association with offspring height.
This observational study suggests that maternal n-6 PUFA status during pregnancy might influence offspring adiposity in childhood.
long chain polyunsaturated fatty acids; adiposity; body composition; fetal programming
We examined the association between birth weight and methylation in the imprinted IGF/H19 loci, the nonimprinted gene NR3C1 and repetitive element DNA (LINE-1 and Alu).
Materials & methods
We collected umbilical cord venous blood from 219 infants born in Mexico City (Mexico) as part of a prospective birth cohort study and analyzed DNA methylation using pyrosequencing.
Birth weight was not associated with DNA methylation of the regions studied. One of the CpG dinucleotides in the IGF2 imprinting control region (ICR)1 includes a potential C–T SNP. Among individuals with an absence of methylation at this site, probably due to a paternally inherited T allele, birth weight was associated with mean methylation status of both IGF2 ICR1 and ICR2. However, this association would not have survived adjustment for multiple testing.
While we did not detect an association between DNA methylation and birth weight, our study suggests a potential gene–epigene interaction between a T allele in the IGF2 ICR1 and methylation of ICRs of IGF2, and fetal growth.
Alu; birth weight; DNA methylation; fetal growth; glucocorticoid receptor; IGF2; imprinting; LINE-1; NR3C1; SNP
DNA methylation, an epigenetic alteration typically occurring early in cancer development, could aid in the molecular diagnosis of melanoma. We determined technical feasibility for high-throughput DNA-methylation array-based profiling using formalin-fixed paraffin-embedded tissues for selection of candidate DNA-methylation differences between melanomas and nevi. Promoter methylation was evaluated in 27 common benign nevi and 22 primary invasive melanomas using a 1505 CpG site microarray. Unsupervised hierarchical clustering distinguished melanomas from nevi; 26 CpG sites in 22 genes were identified with significantly different methylation levels between melanomas and nevi after adjustment for age, sex, and multiple comparisons and with β-value differences of ≥0.2. Prediction analysis for microarrays identified 12 CpG loci that were highly predictive of melanoma, with area under the receiver operating characteristic curves of >0.95. Of our panel of 22 genes, 14 were statistically significant in an independent sample set of 29 nevi (including dysplastic nevi) and 25 primary invasive melanomas after adjustment for age, sex, and multiple comparisons. This first report of a DNA-methylation signature discriminating melanomas from nevi indicates that DNA methylation appears promising as an additional tool for enhancing melanoma diagnosis.
melanoma; nevi; methylation profiling; diagnostic markers
The highly improved cognitive function is the most significant change in human evolutionary history. Recently, several large-scale studies reported the evolutionary roles of DNA methylation; however, the role of DNA methylation on brain evolution is largely unknown.
To test if DNA methylation has contributed to the evolution of human brain, with the use of MeDIP-Chip and SEQUENOM MassARRAY, we conducted a genome-wide analysis to identify differentially methylated regions (DMRs) in the brain between humans and rhesus macaques. We first identified a total of 150 candidate DMRs by the MeDIP-Chip method, among which 4 DMRs were confirmed by the MassARRAY analysis. All 4 DMRs are within or close to the CpG islands, and a MIR3 repeat element was identified in one DMR, but no repeat sequence was observed in the other 3 DMRs. For the 4 DMR genes, their proteins tend to be conserved and two genes have neural related functions. Bisulfite sequencing and phylogenetic comparison among human, chimpanzee, rhesus macaque and rat suggested several regions of lineage specific DNA methylation, including a human specific hypomethylated region in the promoter of K6IRS2 gene.
Our study provides a new angle of studying human brain evolution and understanding the evolutionary role of DNA methylation in the central nervous system. The results suggest that the patterns of DNA methylation in the brain are in general similar between humans and non-human primates, and only a few DMRs were identified.
DNA methylation; Brain evolution; Primates
There is relatively little methylation array data available specifically for oral
squamous cell carcinoma (OSCC). This study aims to compare the DNA methylome across a
large cohort of tumour/normal pairs.
DNA was extracted from 44 OSCCs and paired normal mucosa. DNA methylation analysis
employed the Illumina GoldenGate high-throughput array comprising 1505 CpG loci selected
from 807 epigenetically regulated genes. This data was correlated with extracapsular
spread (ECS), human papilloma virus (HPV) status, recurrence and 5-year survival.
Differential methylation levels of a number of genes distinguished the tumour tissue
sample from the matched normal. Putative methylation signatures for ECS and recurrence
were identified. The concept of concordant methylation or CpG island methylator
phenotype (CIMP) in OSCC is supported by our data, with an association between
‘CIMP-high' and worse prognosis. Epigenetic deregulation of NOTCH4
signalling in OSCC was also observed, as part of a possible methylation signature for
recurrence, with parallels to recently discovered NOTCH mutations in HNSCC.
Differences in methylation in HPV-driven cases were seen, but are less significant than
that has been recently proposed in other series.
Although OSCC seems as much an ‘epigenetic' as a genetic disease, the
translational potential of cancer epigenetics has yet to be fully exploited. This data
points to the application of epigenetic biomarkers and targets available to further the
development of therapy in OSCC.
oral squamous cell carcinoma; DNA methylation; microarray; prognosis
Colorectal cancer (CRC) arises as a consequence of genetic events such as gene mutation and epigenetic alteration. The aim of this study was to identify new hypermethylated candidate genes and methylation-based therapeutic targets using vincristine in CRC.
We analyzed the methylation status of 27,578 CpG sites spanning more than 14,000 genes in CRC tissues compared with adjacent normal tissues and normal colon tissues using Illumina bead chip array. Twenty-one hypermethylated genes and 18 CpG island methylator phenotype markers were selected as candidate genes. The methylation status of 39 genes was validated by quantitative methylation-specific polymerase chain reaction in CRC tissues, adjacent normal tissues, normal colon cells, and three CRC cell lines. Of these, 29 hypermethylated candidate genes were investigated using the demethylating effects of 5-aza-2′-deoxycytidine (5-aza-dC) and vincristine in CRC cells.
Thirty-two out of 39 genes were hypermethylated in CRC tissues compared with adjacent normal tissues. Vincristine induced demethylation of methylated genes in CRC cells to the same extent as 5-aza-dC. The mRNA expression of AKR1B1, CHST10, ELOVL4, FLI1, SOX5, STK33, and ZNF304 was restored by treatment with 5-aza-dC and vincristine.
These results suggest that these novel hypermethylated genes AKR1B1, CHST10, ELOVL4, SOX5, STK33, and ZNF304 may be potential methylation biomarkers and therapeutic targets of vincristine in CRC.
Colorectal cancer; Hypermethylated genes; Therapeutic targets; CIMP markers; 5-aza-2′-deoxycytidine; Vincristine