Determining Effects of Maternal Methyl Donor Nutrient Deficiency and DNA Sequence Differences on Methylation Potential and Offspring Developmental Outcomes

Abstract

Methyl donor nutrients folate, choline, betaine, methionine, and vitamin B12 play a critical role in epigenetic modifications. These nutrients and their metabolites carry methyl groups required for generating S‐adenosylmethionine (SAM), the major methyl group contributor for DNA and histone methylation. Here, we assess the role of maternal dietary methyl donor deficiency with and without antibiotic (succinyl sulfathiozole, 1% SS) in determining methylation potential and offspring developmental outcomes. We also assess the role of cis‐acting DNA sequences in determining DNA methylation outcomes in response to methyl donor deficiency using mouse lines carrying mutations at the growth‐regulating H19/Igf2 imprinted domain compared to wild type C57BL/6J (B6) mice. Mice were treated with four diet groups (1) Methyl Sufficient (MS), (2) MS+1%SS, (3) Methyl Deficient (MD) and (4) MD+1%SS for 5 weeks before pregnancy and throughout gestation. We observed a significant decrease in the plasma folate levels of mice within the MD group compared to MS in the presence or absence of 1% SS. However, 1% SS alone did not cause significant reduction in plasma folate levels in mice fed the MS diet. Average liver SAM levels were significantly lower in MD groups compared with MS diet group only in the presence of the antibiotic. Liver SAH levels and SAM/SAH ratios remained relatively constant across the 4 different diet groups. Despite the significant reduction in maternal plasma folate levels, dietary methyl deficiency alone did not affect average litter size or male to female ratios. However, addition of antibiotic (1% SS) in the respective diets led to a significant decline in average litter size and litter success. Both methyl sufficient diets had a larger percentage of litter surviving till weaning as compared to the methyl deficient diets. Effects of the methyl depleted diet alone had insignificant effects on development while the presence of the antibiotic (1% SS) in the diet significantly altered pup body weight at postnatal day 5 (PND5) and PND21. Adult (8 wk) body weights were seemingly unaffected while testes weight mirrored body weight even after correction. Interestingly, dietary effects on body weight were inversely affected when mutant lines were compared to wild‐type lines. In conclusion, a maternal methyl donor deficient diet likely leads to a decrease in methylation potential due to lower plasma folate and liver SAM levels. Phenotypic outcomes are influenced by an aggregate effect of dietary deficiency, antibiotic treatment and maternal genotype. Studies are ongoing to determine the effect of methyl donor deficiency on epigenetic reprogramming and gene expression at imprinted loci across the genome. These effects will be further characterized to determine whether there is an additional role of 1% SS in the diet and whether genetic changes in cis influences susceptibility to epigenetic outcomes.