[show abstract][hide abstract] ABSTRACT: Literature on maternal exposures and the risk of epigenetic changes or diseases in the offspring is growing. Paternal contributions are often not considered. However, some animal and epidemiologic studies on various contaminants, nutrition, and lifestyle-related conditions suggest a paternal influence on the offspring's future health. The phenotypic outcomes may have been attributed to DNA damage or mutations, but increasing evidence shows that the inheritance of environmentally induced functional changes of the genome, and related disorders, are (also) driven by epigenetic components. In this essay we suggest the existence of epigenetic windows of susceptibility to environmental insults during sperm development. Changes in DNA methylation, histone modification, and non-coding RNAs are viable mechanistic candidates for a non-genetic transfer of paternal environmental information, from maturing germ cell to zygote. Inclusion of paternal factors in future research will ultimately improve the understanding of transgenerational epigenetic plasticity and health-related effects in future generations.
[show abstract][hide abstract] ABSTRACT: Background:Several epidemiologic studies have demonstrated associations between periconceptional environmental exposures and health status of the offspring in later life. Although these environmentally related effects have been attributed to epigenetic changes, such as DNA methylation shifts at imprinted genes, little is known about the potential effects of maternal and paternal preconceptional overnutrition or obesity.Objective:We examined parental preconceptional obesity in relation to DNA methylation profiles at multiple human imprinted genes important in normal growth and development: MEG3, MEST, PEG3, PLAGL1, SGCE/PEG10, and NNAT.Methods:We measured methylation percentages at the DMRs by bisulfite pyrosequencing in DNA extracted from umbilical cord blood leukocytes of 92 newborns. Preconceptional obesity, defined as BMI 30 kg/m(2), was ascertained through standardized questionnaires.Results:After adjusting for potential confounders and cluster effects, paternal obesity was significantly associated with lower methylation levels at the MEST (β=-2.57; s.e.=0.95; P=0.008), PEG3 (-1.71; SE=0.61; P=0.005), and NNAT (-3.59; SE=1.76; P=0.04) DMRs. Changes related to maternal obesity were detected at other loci: β-coefficient was +2.58 (s.e.=1.00; P=0.01) at PLAGL1 DMR, and -3.42 (s.e.=1.69; P=0.04) at the MEG3 DMR.Conclusion:We found altered methylation outcomes at multiple imprint regulatory regions in children born to obese parents, compared to children born to non-obese parents. In spite of the small sample size, our data suggest a preconceptional influence of parental life-style or overnutrition on the reprogramming of imprint marks during gametogenesis. More specifically, the significant and independent association between paternal obesity and the offspring's methylation status suggests the susceptibility of the developing sperm for environmental insults. The acquired imprint instability may be carried on to the next generation and increase the risk for chronic diseases in adulthood.International Journal of Obesity accepted article preview online, 25 October 2013; doi:10.1038/ijo.2013.193.
International journal of obesity (2005) 10/2013; · 5.22 Impact Factor
[show abstract][hide abstract] ABSTRACT: At birth, elevated IGF-I levels have been linked to birth weight extremes; high birth weight and low birth weight are risk factors for adult-onset chronic diseases including obesity, cardiovascular disease, and type 2 diabetes. We examined associations between plasma IGF-I levels and birth weight among infants born to African American and White obese and nonobese women. Prepregnancy weight and height were assessed among 251 pregnant women and anthropometric measurements of full term infants (≥37 weeks of gestation) were taken at birth. Circulating IGF-I was measured by ELISA in umbilical cord blood plasma. Linear regression models were utilized to examine associations between birth weight and high IGF-I, using the bottom two tertiles as referents. Compared with infants with lower IGF-I levels (≤3rd tertile), those with higher IGF-I levels (>3rd tertile) were 130 g heavier at birth, (β-coefficient = 230, se = 58.0, P = 0.0001), after adjusting for gender, race/ethnicity, gestational age, delivery route, maternal BMI and smoking. Stratified analyses suggested that these associations are more pronounced in infants born to African American women and women with BMI ≥30 kg/m(2); the cross product term for IGF-I and maternal BMI was statistically significant (P ≤ 0.0004). Our findings suggest that the association between IGF-I levels and birth weight depends more on maternal obesity than African American race/ethnicity.
[show abstract][hide abstract] ABSTRACT: Objectives:Low birth weight (LBW) has been associated with common adult-onset chronic diseases, including obesity, cardiovascular disease, type II diabetes and some cancers. The etiology of LBW is multi-factorial. However, recent evidence suggests exposure to antibiotics may also increase the risk of LBW. The mechanisms underlying this association are unknown, although epigenetic mechanisms are hypothesized. In this study, we evaluated the association between maternal antibiotic use and LBW and examined the potential role of altered DNA methylation that controls growth regulatory imprinted genes in these associations.Methods:Between 2009-2011, 397 pregnant women were enrolled and followed until delivery. Prenatal antibiotic use was ascertained through maternal self-report. Imprinted genes methylation levels were measured at differentially methylated regions (DMRs) using bisulfite pyrosequencing. Generalized linear models were used to examine associations among antibiotic use, birth weight and DMR methylation fractions.Results:After adjusting for infant gender, race/ethnicity, maternal body mass index, delivery route, gestational weight gain, gestational age at delivery, folic acid intake, physical activity, maternal smoking and parity, antibiotic use during pregnancy was associated with 138 g lower birth weight compared with non-antibiotic use (β-coefficient=-132.99, s.e.=50.70, P=0.008). These associations were strongest in newborns of women who reported antibiotic use other than penicillins (β-coefficient=-135.57, s.e.=57.38, P=0.02). Methylation at five DMRs, IGF2 (P=0.05), H19 (P=0.15), PLAGL1 (P=0.01), MEG3 (P=0.006) and PEG3 (P=0.08), was associated with maternal antibiotic use; among these, only methylation at the PLAGL1 DMR was also associated with birth weight.Conclusion:We report an inverse association between in utero exposure to antibiotics and lower infant birth weight and provide the first empirical evidence supporting imprinted gene plasticity in these associations.International Journal of Obesity advance online publication, 23 April 2013; doi:10.1038/ijo.2013.47.
International journal of obesity (2005) 03/2013; · 5.22 Impact Factor
[show abstract][hide abstract] ABSTRACT: BACKGROUND: Data from epidemiological and animal model studies suggest that nutrition during pregnancy may affect the health status of subsequent generations. These transgenerational effects are now being explained by disruptions at the level of the epigenetic machinery. Besides in vitro environmental exposures, the possible impact on the reprogramming of methylation profiles at imprinted genes at a much earlier time point, such as during spermatogenesis or oogenesis, has not previously been considered. In this study, our aim was to determine associations between preconceptional obesity and DNA methylation profiles in the offspring, particularly at the differentially methylated regions (DMRs) of the imprinted Insulin-like Growth Factor 2 (IGF2) gene. METHODS: We examined DNA from umbilical cord blood leukocytes from 79 newborns, born between July 2005 and November 2006 at Duke University Hospital, Durham, NC. Their mothers participated in the Newborn Epigenetics Study (NEST) during pregnancy. Parental characteristics were obtained via standardized questionnaires and medical records. DNA methylation patterns at two DMRs were analyzed by bisulfite pyrosequencing; one DMR upstream of IGF2 (IGF2 DMR), and one DMR upstream of the neighboring H19 gene (H19 DMR). Multiple regression models were used to determine potential associations between the offspring's DNA methylation patterns and parental obesity before conception. Obesity was defined as body mass index (BMI) [greater than or equal to]30 kg/m2. RESULTS: Hypomethylation at the IGF2 DMR was associated with paternal obesity. Even after adjusting for several maternal and newborn characteristics, we observed a persistent inverse association between DNA methylation in the offspring and paternal obesity (beta-coefficient was -5.28, P = 0.003). At the H19 DMR, no significant associations were detected between methylation patterns and paternal obesity. Our data suggest an increase in DNA methylation at the IGF2 and H19 DMRs among newborns from obese mothers, but a larger study is warranted to further explore the potential effects of maternal obesity or lifestyle on the offspring's epigenome. CONCLUSIONS: While our small sample size is limited, our data indicate a preconceptional impact of paternal obesity on the reprogramming of imprint marks during spermatogenesis. Given the biological importance of imprinting fidelity, our study provides evidence for transgenerational effects of paternal obesity that may influence the offspring's future health status. See related commentary article here http://www.biomedcentral.com/1741-7015/11/30.
BMC Medicine 02/2013; 11(1):29. · 6.68 Impact Factor
[show abstract][hide abstract] ABSTRACT: Imprinted genes form a special subset of the genome, exhibiting monoallelic expression in a parent-of-origin-dependent fashion. This monoallelic expression is controlled by parental-specific epigenetic marks, which are established in gametogenesis and early embryonic development and are persistent in all somatic cells throughout life. We define this specific set of cis-acting epigenetic regulatory elements as the imprintome, a distinct and specially tasked subset of the epigenome. Imprintome elements contain DNA methylation and histone modifications that regulate monoallelic expression by affecting promoter accessibility, chromatin structure, and chromatin configuration. Understanding their regulation is critical because a significant proportion of human imprinted genes are implicated in complex diseases. Significant species variation in the repertoire of imprinted genes and their epigenetic regulation, however, will not allow model organisms solely to be used for this crucial purpose. Ultimately, only the human will suffice to accurately define the human imprintome.
ILAR journal / National Research Council, Institute of Laboratory Animal Resources 12/2012; 53(3-4):341-58. · 1.58 Impact Factor
[show abstract][hide abstract] ABSTRACT: Humans are exposed to low-dose ionizing radiation (LDIR) from a number of environmental and medical sources. In addition to inducing genetic mutations, there is concern that LDIR may also alter the epigenome. Such heritable effects early in life can either be positively adaptive or result in the enhanced formation of diseases, including cancer, diabetes, and obesity. Herein, we show that LDIR significantly increased DNA methylation at the viable yellow agouti (A(vy)) locus in a sex-specific manner (P=0.004). Average DNA methylation was significantly increased in male offspring exposed to doses between 0.7 and 7.6 cGy, with maximum effects at 1.4 and 3.0 cGy (P<0.01). Offspring coat color was concomitantly shifted toward pseudoagouti (P<0.01). Maternal dietary antioxidant supplementation mitigated both the DNA methylation changes and coat color shift in the irradiated offspring. Thus, LDIR exposure during gestation elicits epigenetic alterations that lead to positive adaptive phenotypic changes that are negated with antioxidants, indicating they are mediated in part by oxidative stress. These findings provide evidence that in the isogenic A(vy) mouse model, epigenetic alterations resulting from LDIR play a role in radiation hormesis, bringing into question the assumption that every dose of radiation is harmful.-Bernal, A. J., Dolinoy, D. C., Huang, D., Skaar, D. A., Weinhouse, C., Jirtle, R. J. Adaptive radiation-induced epigenetic alterations mitigated by antioxidants.
[show abstract][hide abstract] ABSTRACT: BACKGROUND: Genomic imprinting is an epigenetic phenomenon resulting in parent-of-origin specific monoallelic gene expression. It is postulated to have evolved in placental mammals to modulate intrauterine resource allocation to the offspring. In this study, we determined the imprint status of metatherian orthologues of eutherian imprinted genes. RESULTS: L3MBTL and HTR2A were shown to be imprinted in Monodelphis domestica (the gray short-tailed opossum). MEST expressed a monoallelic and a biallelic transcript, as in eutherians. In contrast, IMPACT, COPG2, and PLAGL1 were not imprinted in the opossum. Differentially methylated regions (DMRs) involved in regulating imprinting in eutherians were not found at any of the new imprinted loci in the opossum. Interestingly, a novel DMR was identified in intron 11 of the imprinted IGF2R gene, but this was not conserved in eutherians. The promoter regions of the imprinted genes in the opossum were enriched for the activating histone modification H3 Lysine 4 dimethylation. CONCLUSIONS: The phenomenon of genomic imprinting is conserved in Therians, but the marked difference in the number and location of imprinted genes and DMRs between metatherians and eutherians indicates that imprinting is not fully conserved between the two Therian infra-classes. The identification of a novel DMR at a non-conserved location as well as the first demonstration of histone modifications at imprinted loci in the opossum suggest that genomic imprinting may have evolved in a common ancestor of these two Therian infra-classes with subsequent divergence of regulatory mechanisms in the two lineages.
[show abstract][hide abstract] ABSTRACT: Depressed mood in pregnancy has been linked to low birth weight (LBW, < 2,500 g), a risk factor for adult-onset chronic diseases in offspring. We examined maternal depressed mood in relation to birth weight and evaluated the role of DNA methylation at regulatory sequences of imprinted genes in this association. We measured depressed mood among 922 pregnant women using the CES-D scale and obtained birth weight data from hospital records. Using bisulfite pyrosequencing of cord blood DNA from 508 infants, we measured methylation at differentially methylated regions (DMRs) regulating imprinted genes IGF2/H19, DLK1/MEG3, MEST, PEG3, PEG10/SGCE, NNAT and PLAGL1. Multiple regression models were used to examine the relationship between depressed mood, birth weight and DMR methylation levels. Depressed mood was associated with a more that 3-fold higher risk of LBW, after adjusting for delivery mode, parity, education, cigarette smoking, folic acid use and preterm birth. The association may be more pronounced in offspring of black women and female infants. Compared with infants of women without depressed mood, infants born to women with severe depressed mood had a 2.4% higher methylation at the MEG3 DMR. Whereas LBW infants had 1.6% lower methylation at the IGF2 DMR, high birth weight (> 4,500 g) infants had 5.9% higher methylation at the PLAGL1 DMR compared with normal birth weight infants. Our findings confirm that severe maternal depressed mood in pregnancy is associated with LBW, and that MEG3 and IGF2 plasticity may play important roles.
Epigenetics: official journal of the DNA Methylation Society 07/2012; 7(7):735-46. · 4.58 Impact Factor
[show abstract][hide abstract] ABSTRACT: Altered methylation at Insulin-like Growth Factor 2 (IGF2) regulatory regions has previously been associated with obesity, and several malignancies including colon, esophageal, and prostate adenocarcinomas, presumably via changes in expression and/or loss of imprinting, but the functional significance of these DNA methylation marks have not been demonstrated in humans. We examined associations among DNA methylation at IGF2 differentially methylated regions (DMRs), circulating IGF2 protein concentrations in umbilical cord blood (UCB) and birth weight in newborns.
Questionnaire data were obtained from 300 pregnant women recruited between 2005 and 2009. UCB DNA methylation was measured by bisulfite pyrosequencing. UCB plasma concentrations of soluble IGF2 were measured by ELISA assays. Generalized linear regression models were used to examine the relationship between DMR methylation and IGF2 levels.
Lower IGF2 DMR methylation was associated with elevated plasma IGF2 protein concentrations (β = -9.87, p < 0.01); an association that was stronger in infants born to obese women (pre-pregnancy BMI > 30 kg/m(2), β = -20.21, p < 0.0001). Elevated IGF2 concentrations were associated with higher birth weight (p < 0.0001) after adjusting for maternal race/ethnicity, pre-pregnancy BMI, cigarette smoking, gestational diabetes, and infant sex. These patterns of association were not apparent at the H19 DMR.
Our data suggest that variation in IGF2 DMR methylation is an important mechanism by which circulating IGF2 concentrations, a putative risk factor for obesity and cancers of the colon, esophagus, and prostate, are modulated; associations that may depend on pre-pregnancy obesity.
Cancer Causes and Control 03/2012; 23(4):635-45. · 3.20 Impact Factor
[show abstract][hide abstract] ABSTRACT: Activation of germline promoters is central to V(D)J recombinational accessibility, driving chromatin remodeling, nucleosome repositioning, and transcriptional read-through of associated DNA. We have previously shown that of the two TCRβ locus (Tcrb) D segments, Dβ1 is flanked by an upstream promoter that directs its transcription and recombinational accessibility. In contrast, transcription within the DJβ2 segment cluster is initially restricted to the J segments and only redirected upstream of Dβ2 after D-to-J joining. The repression of upstream promoter activity prior to Tcrb assembly correlates with evidence that suggests DJβ2 recombination is less efficient than that of DJβ1. Because inefficient DJβ2 assembly offers the potential for V-to-DJβ2 recombination to rescue frameshifted V-to-DJβ1 joints, we wished to determine how Dβ2 promoter activity is modulated upon Tcrb recombination. In this study, we show that repression of the otherwise transcriptionally primed 5'Dβ2 promoter requires binding of upstream stimulatory factor (USF)-1 to a noncanonical E-box within the Dβ2 12-recombination signal sequence spacer prior to Tcrb recombination. USF binding is lost from both rearranged and germline Dβ2 sites in DNA-dependent protein kinase, catalytic subunit-competent thymocytes. Finally, genotoxic dsDNA breaks lead to rapid loss of USF binding and gain of transcriptionally primed 5'Dβ2 promoter activity in a DNA-dependent protein kinase, catalytic subunit-dependent manner. Together, these data suggest a mechanism by which V(D)J recombination may feed back to regulate local Dβ2 recombinational accessibility during thymocyte development.
The Journal of Immunology 03/2012; 188(5):2266-75. · 5.52 Impact Factor
[show abstract][hide abstract] ABSTRACT: Chromosome 22q11.2 deletion syndrome (22q11DS) is the most common microdeletion syndrome in humans. It is typified by highly variable symptoms, which might be explained by epigenetic regulation of genes in the interval. Using computational algorithms, our laboratory previously predicted that DiGeorge critical region 6 (DGCR6), which lies within the deletion interval, is imprinted in humans. Expression and epigenetic regulation of this gene have not, however, been examined in 22q11DS subjects. The purpose of this study was to determine if the expression levels of DGCR6 and its duplicate copy DGCR6L in 22q11DS subjects are associated with the parent-of-origin of the deletion and childhood psychopathologies. Our investigation showed no evidence of parent-of-origin-related differences in expression of both DGCR6 and DGCR6L. However, we found that the variability in DGCR6 expression was significantly greater in 22q11DS children than in age and gender-matched control individuals. Children with 22q11DS who had anxiety disorders had significantly lower DGCR6 expression, especially in subjects with the deletion on the maternal chromosome, despite the lack of imprinting. Our findings indicate that epigenetic mechanisms other than imprinting contribute to the dysregulation of these genes and the associated childhood psychopathologies observed in individuals with 22q11DS. Further studies are now needed to test the usefulness of DGCR6 and DGCR6L expression and alterations in the epigenome at these loci in predicting childhood anxiety and associated adult-onset pathologies in 22q11DS subjects.
[show abstract][hide abstract] ABSTRACT: To determine whether aberrant DNA methylation at differentially methylated regions (DMRs) regulating insulin-like growth factor 2 (IGF2) expression in umbilical cord blood is associated with overweight or obesity in a multiethnic cohort.
Umbilical cord blood leukocytes of 204 infants born between 2005 and 2009 in Durham, North Carolina, were analyzed for DNA methylation at two IGF2 DMRs by using pyrosequencing. Anthropometric and feeding data were collected at age 1 year. Methylation differences were compared between children >85th percentile of the Centers for Disease Control and Prevention growth charts weight-for-age (WFA) and children ≤ 85th percentile of WFA at 1 year by using generalized linear models, adjusting for post-natal caloric intake, maternal cigarette smoking, and race/ethnicity.
The methylation percentages at the H19 imprint center DMR was higher in infants with WFA >85th percentile (62.7%; 95% CI, 59.9%-65.5%) than in infants with WFA ≤ 85th percentile (59.3%; 95% CI, 58.2%-60.3%; P = .02). At the intragenic IGF2 DMR, methylation levels were comparable between infants with WFA ≤ 85th percentile and infants with WFA >85th percentile.
Our findings suggest that IGF2 plasticity may be mechanistically important in early childhood overweight or obese status. If confirmed in larger studies, these findings suggest aberrant DNA methylation at sequences regulating imprinted genes may be useful identifiers of children at risk for the development of early obesity.
The Journal of pediatrics 02/2012; 161(1):31-9. · 4.02 Impact Factor
[show abstract][hide abstract] ABSTRACT: The Mannose 6 Phosphate/Insulin-like Growth Factor Receptor-2 (IGF2R) encodes a type-1 membrane protein that modulates availability of the potent mitogen, IGF2. We evaluated the associations between IGF2R non-synonymous genetic variants (c.5002G>A, Gly1619Arg(rs629849), and c.901C>G, Leu252Val(rs8191754)), circulating IGF2 levels, and colon cancer (CC) risk among African American and White participants enrolled in the North Carolina Colon Cancer Study (NCCCS). Generalized linear models were used to compare circulating levels of IGF2 among 298 African American and 518 White controls. Logistic regression models were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association of IGF2R genetic variants and CC risk. Women homozygous for the IGF2R c.5002 G>A allele, had higher mean levels of circulating IGF2, 828 (SD=321) ng/ml compared to non-carriers, 595 (SD=217) ng/ml (p-value=0.01). This pattern was not apparent in individuals homozygous for the IGF2R c.901 C>G variant. Whites homozygous for the IGF2R c.901 C>G variant trended towards a higher risk of CC, OR=2.2 [95% CI(0.9-5.4)], whereas carrying the IGF2R c.5002 G>A variant was not associated with CC risk. Our findings support the hypothesis that being homozygous for the IGF2R c.5002 G>A modulates IGF2 circulating levels in a sex-specific manner, and while carrying the IGF2R c.901 C>G may increase cancer risk, the mechanism may not involve modulation of circulating IGF2.
[show abstract][hide abstract] ABSTRACT: Epigenetic alterations may mechanistically explain the developmental origins of adult disease, namely the hypothesis that many complex adult chronic diseases originate as a result of conditions encountered in utero. If true, epigenetically regulated imprinted genes, critical to normal growth and development, may partially mediate these outcomes. We determined the influence of in utero exposure to cigarette smoking on methylation at two differentially methylated regions (DMRs) regulating Insulin-like Growth Factor 2 (IGF2) and H19, and how this might relate to birth weight of infants born to 418 pregnant women. Smoking status was ascertained through self-report and medical records. Bisulfite pyrosequencing was used to measure methylation in umbilical cord blood DNAs. Least squares DNA methylation means at each DMR and birth weight were compared between infants of smokers and non-smokers, using generalized linear models. While there were no significant differences at the H19 DMR, infants born to smokers had higher methylation at the IGF2 DMR than those born to never smokers or those who quit during pregnancy (49.5%, SD=8.0 versus 46.6%, SD=5.6 and 45.8%, SD=6.3, respectively; p=0.0002). The smoking-related increase in methylation was most pronounced in male offspring (p for sex interaction=0.03), for whom approximately 20% of smoking-related low birth weight was mediated by DNA methylation at the IGF2 DMR. Our findings suggest that IGF2 DMR plasticity is an important mechanism by which in utero adjustments to environmental toxicants are conferred. Larger studies to replicate these findings are required.
[show abstract][hide abstract] ABSTRACT: Genetic loci displaying environmentally responsive epigenetic marks, termed metastable epialleles, offer a solution to the paradox presented by genetically identical yet phenotypically distinct individuals. The murine viable yellow agouti (A (vy) ) metastable epiallele exhibits stochastic DNA methylation and histone modifications associated with coat color variation in isogenic individuals. The distribution of A (vy) variable expressivity shifts following maternal nutritional and environmental exposures. To characterize additional murine metastable epialleles, we utilized genome-wide expression arrays (N = 10 male individuals, 3 tissues per individual) and identified candidates displaying large variability in gene expression among individuals (Vi = inter-individual variance), concomitant with a low variability in gene expression across tissues from the three germ layers (Vt = inter-tissue variance), two features characteristic of the A (vy) metastable epiallele. The CpG island in the promoter of Dnajb1 and two contraoriented ERV class II repeats in Glcci1 were validated to display underlying stochasticity in methylation patterns common to metastable epialleles. Furthermore, liver DNA methylation in mice exposed in utero to 50 mg bisphenol A (BPA)/kg diet (N = 91) or a control diet (N = 79) confirmed environmental lability at validated candidate genes. Significant effects of exposure on mean CpG methylation were observed at the Glcci1 Repeat 1 locus (p < 0.0001). Significant effects of BPA also were observed at the first and fifth CpG sites studied in Glcci1 Repeat 2 (p < 0.0001 and p = 0.004, respectively). BPA did not affect methylation in the promoter of Dnajb1 (p = 0.59). The characterization of metastable epialleles in humans is crucial for the development of novel screening and therapeutic targets for human disease prevention.
Epigenetics: official journal of the DNA Methylation Society 09/2011; 6(9):1105-13. · 4.58 Impact Factor
[show abstract][hide abstract] ABSTRACT: Folic acid (FA) supplementation before and during pregnancy has been associated with decreased risk of neural tube defects although recent reports suggest it may also increase the risk of other chronic diseases. We evaluated exposure to maternal FA supplementation before and during pregnancy in relation to aberrant DNA methylation at two differentially methylated regions (DMRs) regulating Insulin-like Growth Factor 2 (IGF2) expression in infants. Aberrant methylation at these regions has been associated with IGF2 deregulation and increased susceptibility to several chronic diseases. Using a self-administered questionnaire, we assessed FA intake before and during pregnancy in 438 pregnant women. Pyrosequencing was used to measure methylation at two IGF2 DMRs in umbilical cord blood leukocytes. Mixed models were used to determine relationships between maternal FA supplementation before or during pregnancy and DNA methylation levels at birth. Average methylation at the H19 DMR was 61.2%. Compared to infants born to women reporting no FA intake before or during pregnancy, methylation levels at the H19 DMR decreased with increasing FA intake (2.8%, p=0.03, and 4.9%, p=0.04, for intake before and during pregnancy, respectively). This methylation decrease was most pronounced in male infants (p=0.01). Methylation alterations at the H19 DMR are likely an important mechanism by which FA risks and/or benefits are conferred in utero. Because stable methylation marks at DMRs regulating imprinted genes are acquired before gastrulation, they may serve as archives of early exposures with the potential to improve our understanding of developmental origins of adult disease.
Epigenetics: official journal of the DNA Methylation Society 07/2011; 6(7):928-36. · 4.58 Impact Factor
[show abstract][hide abstract] ABSTRACT: Differentially methylated regions (DMRs) are stable epigenetic features within or in proximity to imprinted genes. We used this feature to identify candidate human imprinted loci by quantitative DNA methylation analysis. We discovered a unique DMR at the 5'-end of FAM50B at 6p25.2. We determined that sense transcripts originating from the FAM50B locus are expressed from the paternal allele in all human tissues investigated except for ovary, in which expression is biallelic. Furthermore, an antisense transcript, FAM50B-AS, was identified to be monoallelically expressed from the paternal allele in a variety of tissues. Comparative phylogenetic analysis showed that FAM50B orthologs are absent in chicken and platypus, but are present and biallelically expressed in opossum and mouse. These findings indicate that FAM50B originated in Therians after divergence from Prototherians via retrotransposition of a gene on the X chromosome. Moreover, our data are consistent with acquisition of imprinting during Eutherian evolution after divergence of Glires from the Euarchonta mammals. FAM50B expression is deregulated in testicular germ cell tumors, and loss of imprinting occurs frequently in testicular seminomas, suggesting an important role for FAM50B in spermatogenesis and tumorigenesis. These results also underscore the importance of accounting for parental origin in understanding the mechanism of 6p25-related diseases.
Nucleic Acids Research 03/2011; 39(13):5388-400. · 8.28 Impact Factor
[show abstract][hide abstract] ABSTRACT: Folic acid (FA) added to foods during fortification is 70-85% bioavailable compared to 50% of folate occurring naturally in foods. Thus, if FA supplements also are taken during pregnancy, both mother and fetus can be exposed to FA exceeding the Institute of Medicine's recommended tolerable upper limit (TUL) of 1,000 micrograms per day (μg/d) for adult pregnant women. The primary objective is to estimate the proportion of women taking folic acid (FA) doses exceeding the TUL before and during pregnancy, and to identify correlates of high FA use.
During 2005-2008, pre-pregnancy and pregnancy-related data on dietary supplementation were obtained by interviewing 539 pregnant women enrolled at two obstetrics-care facilities in Durham County, North Carolina.
Before pregnancy, 51% of women reported FA supplementation and 66% reported this supplementation during pregnancy. Before pregnancy, 11.9% (95% CI = 9.2%-14.6%) of women reported supplementation with FA doses above the TUL of 1,000 μg/day, and a similar proportion reported this intake prenatally. Before pregnancy, Caucasian women were more likely to take FA doses above the TUL (OR = 2.99; 95% = 1.28-7.00), compared to African American women, while women with chronic conditions were less likely to take FA doses above the TUL (OR = 0.48; 95%CI = 0.21-0.97). Compared to African American women, Caucasian women were also more likely to report FA intake in doses exceeding the TUL during pregnancy (OR = 5.09; 95%CI = 2.07-12.49).
Fifty-one percent of women reported some FA intake before and 66% during pregnancy, respectively, and more than one in ten women took FA supplements in doses that exceeded the TUL. Caucasian women were more likely to report high FA intake. A study is ongoing to identify possible genetic and non-genotoxic effects of these high doses.
BMC Public Health 01/2011; 11(1):46. · 2.08 Impact Factor