Transgenerational inheritance of betaine-induced epigenetic alterations in estrogen-responsive IGF-2/IGFBP2 genes in rat hippocampus

ABSTRACT Betaine as a methyl donor participates in DNA methylation. Here, we sought to investigate the effects of betaine on hippocampal expression of neurogenesis genes and their DNA methylation status across three generations. Pregnant rats (F0) were fed control and betaine-supplemented diets throughout gestation and lactation; and female F1 and F2 offspring at weaning, together with the F0 dams, were used in the study. Hippocampal expression of aromatase, estrogen receptor α and estrogen related receptor β was down-regulated in F1, together with the estrogen-responsive IGF-2/IGFBP2 genes. However, all these genes were up-regulated in F2, which follows the same pattern of F0. In agreement with changes in mRNA expression, the imprinting control region (ICR) of IGF-2 gene was hypomethylated in F1 but hypermethylated in F2 and F0. In contrast, the promoter DNA methylation status of all the affected genes was hypermethylated in F1 but hypomethylated in F2 and F0. Betaine homocysteine methyltransferase followed same pattern of transgenerational inheritance. These results indicate that betaine exerts a transgenerational effect on hippocampal expression of estrogen-responsive genes in rat offspring, which is associated with corresponding alterations in DNA methylation on ICR of IGF-2 gene and the promoter of affected genes. Author Summary Epigenetic transgenerational inheritance is defined as the phenotypic change across generations and germline transmission of epigenetic information without direct genetic manipulation or environmental exposure. Maternal and paternal diet has been shown to have transgenerational behavioral and physiological effects. Maternal intake of methyl donors, including folate, betaine, and choline during different gestation period alters epigenetic modifications of many imprinted genes in the genomic DNA isolated from cord blood. Betaine as a methyl donor nutrition plays an important role in brain development. However, the effect of maternal betaine supplementation on transgenerational inheritance of imprinted gene IGF-2 in offspring hippocampus is still unknown. Here, we sought to investigate the effects of betaine on rat hippocampal expression of neurogenesis genes and their DNA methylation status across three generations. We found that betaine significantly decreased estrogen-responsive genes IGF-2/IGFBP2 expression in rat F1 offspring, yet increased in F2 offspring, which is associated with corresponding alterations in DNA methylation on ICR of IGF-2 gene and the promoter of affected genes. Our results suggesting that maternal methyl donor nutrition supplementation may be exert an epigenetic transgenerational effect on female offspring.