Abstract 5354: Altered DNA methylation at imprinted insulin-like growth factor-2 (IGF2) resulting from heavy metal exposure in vitro and in vivo in infants from the newborn epigenetic study (NEST).
Authors: Nye Monica D. , Vidal Adriana , Hoyo Cathrine , Murphy Susan K. 
Published: August 2014

Early life exposure to heavy metals, including lead, has adverse consequences on health and development but the mechanism(s) underlying these effects are unclear. Epigenetic deregulation resulting from lead exposure may underlie these effects, and imprinted genes may be particularly vulnerable since imprinting is established and maintained in large part through DNA methylation. Imprinted genes are powerful regulators of growth and energy utilization. The best studied imprinted genes are insulin-like growth factor 2 (IGF2) and H19 which are regulated by at least two differentially methylated regions (DMRs). Altered methylation at the IGF2/H19 DMRs has been associated with obesity, neurodevelopmental disorders, and cancer. Data from the Newborn Epigenetics STudy (NEST), which is focused on the influence of early life environmental exposures on children's health, has indicated that epigenetic alterations resulting from environmental exposures can be sex-specific and exacerbated in African Americans as compared to whites.

We sought to determine if in vitro exposure to lead alters DNA methylation at two regulatory DMRs important to imprinting and expression of IGF2 and to assess how these results compared to the effects of lead exposure in the NEST cohort.

Immortalized normal human embryonic kidney cells (HEK-293) were exposed to lead acetate (0-25 μg/dL) for up to 72 hours followed by purification of genomic DNA. Bisulfite modification of HEK-293 and NEST cohort DNA specimens was followed by pyrosequencing to quantify DNA methylation. The North Carolina State Laboratory for Public Health performed the blood lead level testing as part of a routine check-up for children between the ages of 1-3 years old. The NEST cohort participants were born between 2005-2008 at obstetrics-care facilities in Durham County, North Carolina. For this study we used a sub-population of participants whose mother lived at the same address since conception in order to more accurately determine early and consistent environmental lead exposure. Analysis of variance (ANOVA) testing was done on the in vitro data to examine the difference between mean values of the lead treatment conditions. For the NEST samples we used generalized linear models in a sample of n=182 participants to examine aberrant methylation at the IGF2 DMRs in children exposed to environmental lead from conception to ages 1-3 years.

In our in vitro model of early environmental lead exposure we saw a 3-5% decrease in IGF2 DMR methylation with increasing lead acetate concentration. Similar to the hypomethylation seen in the in vitro studies, within the NEST cohort we observed a 4% decrease in methylation at the H19 DMR in female children with blood lead levels between 2-4 μg/dL and an 8% decrease in methylation for female infants with blood lead levels equal to or higher than 5 μg/dL of lead.

Citation Format: Monica D. Nye, Adriana Vidal, Cathrine Hoyo, Susan K. Murphy. Altered DNA methylation at imprinted insulin-like growth factor-2 (IGF2) resulting from heavy metal exposure in vitro and in vivo in infants from the newborn epigenetic study (NEST). [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5354. doi:10.1158/1538-7445.AM2013-5354