Imprinted genes in mouse placental development and the regulation of fetal energy stores

Abstract

Imprinted genes, which are preferentially expressed from one or other parental chromosome as a consequence of epigenetic events in the germline, are known to functionally converge on biological processes that enable in utero development in mammals. Over 100 imprinted genes have been identified in the mouse, the majority of which are both expressed and imprinted in the placenta. The purpose of this review is to provide a summary of the current knowledge regarding imprinted gene function in the mouse placenta. Few imprinted genes have been assessed with respect to their dosage-related action in the placenta. Nonetheless, current data indicate that imprinted genes converge on two key functions of the placenta, nutrient transport and placental signalling. Murine studies may provide a greater understanding of certain human pathologies, including low birth weight and the programming of metabolic diseases in the adult, and complications of pregnancy, such as pre-eclampsia and gestational diabetes, resulting from fetuses carrying abnormal imprints.Reproduction (2013) 145 R117-R137

Inuteroarsenic exposure and epigenome-wide associations in placenta, umbilical artery, and human umbilical vein endothelial cells

“…Furthermore, the placenta is a unique epigenetic target organ as the majority of imprinted genes in animal models are both expressed and imprinted in the placenta and hypothesized to contribute to fetal neurodevelopment. 37,38 In unadjusted analyses a CpG located in the body of the glucocorticoid receptor gene (NR3C1) was significantly hypermethylated in the placenta relative to prenatal arsenic exposure. Previous studies have shown that hypermethylation of the NR3C1 gene influences cortisol response, infant behavior and self-regulation.…”

Placental 5-methylcytosine and 5-hydroxymethylcytosine patterns associate with size at birth

“…Aberrant imprinting leads to abnormalities of both placental and fetal growth in animal models. [4][5][6][7] In addition, altered placental expression of imprinted genes has been reported in association with human fetal growth restriction. [8][9][10] The imprinted insulin-like growth factor 2 (IGF2) gene has a major role in the matching of placental nutrient supply to fetal demand, 4 and altered IGF2 expression has been reported in association with fetal growth restriction in humans.…”

Mammalian viviparity: a complex niche in the evolution of genomic imprinting

“…Only six genes have been identified as imprinted in the marsupials and all are expressed in the placenta, while a number of genes imprinted in the eutherian mammalian placenta are expressed but not imprinted in the marsupial placenta. In eutherian mammals, some 55 imprinted genes have been reported as expressed in the more invasive, longer-lived placenta (Tunster et al, 2013). Therefore, it seems likely that as placental complexity evolved with longer in utero development, the need for tighter control of gene networks resulted in the imprinting of regulatory genes already expressed in the metatherian placenta.…”

“…However, as pregnancy progresses, other invasive interstitial trophoblast cells do express polymorphic leukocyte antigens, but these facilitate both implantation (decidual natural killer (NK) cells) and invasive capacity (uterine NK cells). Decidualisation of the maternal uterus is a necessary prelude to embryonic implantation and formation of the placenta with some 11 imprinted genes now identified as expressed in the maternal decidua (Tunster et al, 2013).…”