ABSTRACT
Fatty Acids, and Epigenetic Modulators) ............................................................................... 62 4.6 Conclusions .............................................................................................................................64 References ........................................................................................................................................64
Fetal growth needs energy. In placental species, energy originates from the food intake of the mother, who transmits nutrients to the growing fetus. This process is allowed by a specic organ, varying in shape and structure throughout mammals, the placenta (for a recent review, see Furukawa, Kuroda, and Sugiyama 2014). The placenta is a fetal transitory organ, intimately interfaced with maternal tissue, featured in metatherian (marsupials) and eutherian mammalian species; besides its nutritional function, it has major immunological and endocrine roles during pregnancy (Garratt et al. 2013). Recurrent ndings suggest that imprinted genes that are expressed from only one allele are often expressed at a high level in the placenta, stressing their role in the management of resources owing from the mother to the fetus, in a potential context of genetic conict stemming from partly contrasting Darwinian interests between the paternal and maternal genomes (Haig 1993). Interestingly, the sequencing of the platypus genome (Ornithorhynchus anatinus), an egg-laying mammal, revealed an apparent absence of imprinted genes correlated to limited acquisition of certain categories of repetitive elements (Renfree et al. 2009; Suzuki et al. 2011; Warren et al. 2008).
