Maternal Diet during Pregnancy Induces Gene Expression and DNA Methylation Changes in Fetal Tissues in Sheep

Abstract

Studies in rats and mice have established that maternal nutrition induces epigenetic modifications, sometimes permanently, that alter gene expression in the fetus, which in turn leads to phenotypic changes. However, limited data is available on the influence of maternal diet on epigenetic modifications and gene expression in sheep. Therefore, the objectives of this study were to investigate the impact of different maternal dietary energy sources on the expression of imprinted genes in fetuses in sheep. Ewes were naturally bred to a single sire and from days 67 ± 3 of gestation until necropsy (days 130 ± 1), they were fed one of three diets of alfalfa haylage (HY; fiber), corn (CN; starch), or dried corn distiller's grains (DG; fiber plus protein plus fat). A total of 26 fetuses were removed from the dams and longissimus dorsi, semitendinosus, perirenal adipose depot, and subcutaneous adipose depot tissues were collected for expression and DNA methylation analyses. Expression analysis of nine imprinted genes and three DNA methyltransferase (DNMTs) genes showed significant effects of the different maternal diets on the expression of these genes. The methylation levels of CpG islands of both IGF2R and H19 were higher in HY and DG than CN fetuses in both males and females. This result is consistent with the low amino acid content of the CN diet, a source of methyl group donors, compared to HY and DG diets. Thus, results of this study provide evidence of association between maternal nutrition during pregnancy and transcriptomic and epigenomic alterations of imprinted genes and DNMTs in the fetal tissues.

Keywords: DNA methylation; gene expression; maternal nutrition; pregnancy.

Figure 1

Fold change differences in expression of IGF2, IGF2R, and GRB10 in sheep fetal perirenal fat using quantitative real-time PCR (qRT-PCR). Data are shown as mean ± maximum- and minimum-fold changes between maternal diets. HY, ad libitum fed alfalfa haylage; CN, limit-fed whole shell corn; DG, limit-fed corn dried distillers grains.

Figure 2

Fold change differences in expression of CEBPA, PPARG, and IGF2 in sheep fetal subcutaneous adipose tissue using quantitative real-time PCR (qRT-PCR). Data are shown as mean ± maximum- and minimum-fold changes between maternal diets and fetus sex. HY, ad libitum fed alfalfa haylage; CN, limit-fed whole shell corn; DG, limit-fed corn dried distillers grains.

Figure 3

Fold change differences in expression of IGF2R, DLK1, and DIO3 in sheep fetal longissimus dorsi muscle using quantitative real-time PCR (qRT-PCR). Data are shown as mean ± maximum- and minimum-fold changes between maternal diets. HY, ad libitum fed alfalfa haylage; CN, limit-fed whole shell corn; DG, limit-fed corn dried distillers grains.

Figure 4

Fold change differences in expression of H19, PEG1.2, MEG8, and DLK1 in sheep fetal semitendinosus muscle using quantitative real-time PCR (qRT-PCR). Data are shown as mean ± maximum- and minimum-fold changes between maternal diets. HY, ad libitum fed alfalfa haylage; CN, limit-fed whole shell corn; DG, limit-fed corn dried distillers grains.

Figure 5

DNA methylation of DMR2 region of IGF2R in sheep fetal longissimus dorsi muscle according to fetus sex (M, male; F, female) and maternal diet (HY, ad libitum fed alfalfa haylage; CN, limit-fed whole shell corn; DG, limit-fed corn dried distillers grains). Numbers below the circles indicate the portions of methylated CpGs versus unmethylated CpGs and percentages below diet types represent the percentage of methylated CpGs in each pool.

Figure 6

Fold change differences in expression of DNMT3b in sheep fetal longissimus dorsi muscle and subcutaneous adipose tissue using quantitative real-time PCR (qRT-PCR). Data are shown as mean ± maximum- and minimum-fold changes between maternal diets. HY, ad libitum fed alfalfa haylage; CN, limit-fed whole shell corn; DG, limit-fed corn dried distillers grains.