Gestational Choline Deficiency Causes Global and Igf2 Gene DNA Hypermethylation by Up-regulation of Dnmt1 Expression

Abstract

During gestation there is a high demand for the essential nutrient choline. Adult rats supplemented with choline during embryonic days (E) 11-17 have improved memory performance and do not exhibit age-related memory decline, whereas prenatally choline-deficient animals have memory deficits. Choline, via betaine, provides methyl groups for the production of S-adenosylmethionine, a substrate of DNA methyltransferases (DNMTs). We describe an apparently adaptive epigenomic response to varied gestational choline supply in rat fetal liver and brain. S-Adenosylmethionine levels increased in both organs of E17 fetuses whose mothers consumed a choline-supplemented diet. Surprisingly, global DNA methylation increased in choline-deficient animals, and this was accompanied by overexpression of Dnmt1 mRNA. Previous studies showed that the prenatal choline supply affects the expression of multiple genes, including insulin-like growth factor 2 (Igf2), whose expression is regulated in a DNA methylation-dependent manner. The differentially methylated region 2 of Igf2 was hypermethylated in the liver of E17 choline-deficient fetuses, and this as well as Igf2 mRNA levels correlated with the expression of Dnmt1 and with hypomethylation of a regulatory CpG within the Dnmt1 locus. Moreover, mRNA expression of brain and liver Dnmt3a and methyl CpG-binding domain 2 (Mbd2) protein as well as cerebral Dnmt3l was inversely correlated to the intake of choline. Thus, choline deficiency modulates fetal DNA methylation machinery in a complex fashion that includes hypomethylation of the regulatory CpGs within the Dnmt1 gene, leading to its overexpression and the resultant increased global and gene-specific (e.g. Igf2) DNA methylation. These epigenomic responses to gestational choline supply may initiate the long term developmental changes observed in rats exposed to varied choline intake in utero.An adequate supply of essential nutrients involved in the metabolism of methyl groups, including folic acid, vitamin B 12 , and choline, is central for normal development of the fetus. This is perhaps best exemplified by the discovery that the dietary supply of folic acid, a vitamin that acts as a coenzyme in one-carbon transfer pathways, during the periconceptual period is critical in prevention of neural tube defects (1). Studies in animal models (2-5) as well as recent epidemiological investigations in humans (6) indicate that choline intake during gestation is particularly important for the normal development and function of the central nervous system. In a frequently used experimental model that employs offspring of pregnant rats or mice consuming diets of varying choline content during the 7-day period of the second half of gestation (embryonic days E11-17), prenatal choline deficiency causes deficits in certain memory tasks (7), whereas prenatal choline supplementation leads to enhanced memory and attention and prevents agerelated memory decline (7-13). These behavioral changes are accompanied by electrophysiological, neuroanatomical, and neuro...

Gestational intake of methyl donors and global LINE-1 DNA methylation in maternal and cord blood: Prospective results from a folate-replete population

“…This would be consistent with a study in rats in which a deficiency of choline, a precursor of betaine, during gestation caused increased global methylation in the brain and liver of offspring by upregulation of DNMT1 expression. 29 However, the fact that we did not find other associations of methyl donor intake at two timepoints with DNA methylation at three timepoints suggests that the findings may be due to chance. If we had corrected for multiple testing, these associations would not have been statistically significant by conventional standards (p < 0.05).…”

Dietary and supplemental maternal methyl-group donor intake and cord blood DNA methylation

“…One possible mechanism that leads to changes in LEP and RXRA methylation could be via alterations in the methylation and, thus, gene expression of DNMT1. 20 In this study, positive, negative, and no associations between maternal methyl-group donor intake and offspring DNA methylation levels were found. It seems that there is no simplistic correlation between maternal methyl-group donor intake and offspring DNA methylation.…”

“…DNMT1 produces the enzyme DNA methyltransferase, which maintains DNA methylation in newly synthesized DNA strands. 5 Animal studies [20][21][22] have shown that maternal diet can influence DNMT1 methylation/expression. For example, a choline deficiency in pregnant rats (hypo)methylates the regulatory CpGs within the DNMT1 gene, leading to its overexpression; this results in an increase of global and gene specific (IGF2) DNA methylation.…”

“…For example, a choline deficiency in pregnant rats (hypo)methylates the regulatory CpGs within the DNMT1 gene, leading to its overexpression; this results in an increase of global and gene specific (IGF2) DNA methylation. 20 The periconceptional period may be particularly susceptible to methyl-group donor intake due to global de-and re-methylation of the embryonal DNA in early development (between fertilization and implantation). However, our and other's results show that there are different windows of susceptibility (organogenesis and tissue differentiation) to epigenetic modifications by gestational methyl-group donor intake; therefore, the focus should not be solely on the periconceptional period.…”

Detection of global DNA methylation and paternally imprinted H19 gene methylation in preeclamptic placentas

“…33 Feeding pregnant rats with a choline-deficient diet led to increased global DNA methylation in fetal liver and brain. 34 Deficiency of methyl group donors like folate or choline could result in hypomethylation of the regulatory CpGs within the DNMT1 gene, leading to its overexpression and subsequent increased global DNA methylation. 35 Furthermore, Ray et al reported that pregnant women with low levels of circulating folate had an increased risk of developing PE.…”