Placental insufficiency causes fetal growth restriction in mice lacking Delta-like homologue 1

Fetal growth restriction (FGR) affects between 3-7% of pregnancies, is associated with increased perinatal morbidity and mortality, and linked to failure of placental function. The placenta is the key transient organ in pregnancy that directs nutrient transfer, intermediary metabolism and the production of hormones that drive maternal metabolic adaptations essential for pregnancy and lactation. The exchange surface of the placenta is formed in early development by the interaction between trophoblast cells that enclose the maternal blood and extraembryonic mesodermal cells that comprise the fetal vasculature. Despite recent insights into trophoblast development derived from novel in-vitro approaches, the processes driving extraembryonic mesoderm development are not well explored. This is due to a dearth of studies employing unbiased approaches to interrogate extraembryonic mesoderm cell populations. Here we use genetic labelling techniques to separate molecular events occurring in the trophoblast from those in the mesodermal layers of the placenta. In combination with conditional targeting, we show that the imprinted gene Dlk1 is a key player in providing nutrients to the embryo by controlling the placental surface area available for nutrient exchange, and by modulating the production of placental hormones that promote maternal nutrient provision in pregnancy.