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

Abstract

24Betaine as a methyl donor participates in DNA methylation. Here, we sought to investigate 25 the effects of betaine on hippocampal expression of neurogenesis genes and their DNA 26 methylation status across three generations. Pregnant rats (F0) were fed control and 27 betaine-supplemented diets throughout gestation and lactation; and female F1 and F2 28 offspring at weaning, together with the F0 dams, were used in the study. Hippocampal 29 expression of aromatase, estrogen receptor α and estrogen related receptor β was 30 down-regulated in F1, together with the estrogen-responsive IGF-2/IGFBP2 genes. 31 However, all these genes were up-regulated in F2, which follows the same pattern of F0. In 32 agreement with changes in mRNA expression, the imprinting control region (ICR) of 33 IGF-2 gene was hypomethylated in F1 but hypermethylated in F2 and F0. In contrast, the 34 promoter DNA methylation status of all the affected genes was hypermethylated in F1 but 35 hypomethylated in F2 and F0. Betaine homocysteine methyltransferase followed same 36 pattern of transgenerational inheritance. These results indicate that betaine exerts a 37 transgenerational effect on hippocampal expression of estrogen-responsive genes in rat 38 offspring, which is associated with corresponding alterations in DNA methylation on ICR 39 of IGF-2 gene and the promoter of affected genes. 40 42 43 44 3 45 Author Summary 46 Epigenetic transgenerational inheritance is defined as the phenotypic change across 47 generations and germline transmission of epigenetic information without direct genetic 48 manipulation or environmental exposure. Maternal and paternal diet has been shown to 49 have transgenerational behavioral and physiological effects. Maternal intake of methyl 50 donors, including folate, betaine, and choline during different gestation period alters 51 epigenetic modifications of many imprinted genes in the genomic DNA isolated from cord 52blood. Betaine as a methyl donor nutrition plays an important role in brain development. 53However, the effect of maternal betaine supplementation on transgenerational inheritance 54 of imprinted gene IGF-2 in offspring hippocampus is still unknown. Here, we sought to 55 investigate the effects of betaine on rat hippocampal expression of neurogenesis genes and 56 their DNA methylation status across three generations. We found that betaine significantly 57 decreased estrogen-responsive genes IGF-2/IGFBP2 expression in rat F1 offspring, yet 58 increased in F2 offspring, which is associated with corresponding alterations in DNA 59 methylation on ICR of IGF-2 gene and the promoter of affected genes. Our results 60 suggesting that maternal methyl donor nutrition supplementation may be exert an 61 epigenetic transgenerational effect on female offspring. 4 63 Introduction 64Hippocampus is the key structure governing many important functions including learning 65 and memory, as well as navigation and spatial orientation (1). Accumulated studies have 66 shown that estrogen enhances synaptic plasticity, such ...