A new study led by the University of Cambridge has identified a key signal that fetuses use to control their supply of nutrients from the placenta, revealing a tug-of-war between genes inherited from the father and from the mother.
As the fetus grows, it receives nourishment via blood vessels in the placenta, a specialized organ containing cells from both child and mother. The fetus is producing a signal to encourage growth of blood vessels within the placenta, allowing for more nutrients from the mother to go through to the fetus.
“We’ve identified one way that the fetus uses to communicate with the placenta to prompt the correct expansion of these blood vessels. When this communication breaks down, the blood vessels don’t develop properly and the baby will struggle to get all the food it needs,” explained study lead author Dr. Ionel Sandovici, a postdoctoral researcher at the University of Cambridge.
Dr. Sandovici and his colleagues discovered that the fetus sends a signal called IGF2 which reaches the placenta through the umbilical cord and promotes the growth of the fetus’s organs. Both too much and too little IGF2 can cause developmental problems and lead to increased risk of diabetes and cardiovascular problems in adulthood.
By analyzing developmental processes in mice, the scientists have found that the response to IGF2 is mediated by another protein, IGF2R. The two genes that produce IGF2 and IGF2R are “imprinted” (a process through which molecular switches on the genes identify from which parent they come from and can turn the genes on or off). In this particular case, only the copy of the IGF2 gene inherited from the father is active, while only the copy of IGFR2 inherited from the mother is active.
“One theory about imprinted genes is that paternally-expressed genes are greedy and selfish. They want to extract the most resources as possible from the mother. But maternally-expressed genes act as countermeasures to balance these demands,” said co-lead author Dr. Miguel Constância, an expert on imprinting at Cambridge.
“In our study, the father’s gene drives the fetus’s demands for larger blood vessels and more nutrients, while the mother’s gene in the placenta tries to control how much nourishment she provides. There’s a tug-of-war taking place, a battle of the sexes at the level of the genome.”
These findings, published in the journal Developmental Cell, shed more light on how the fetus, the mother, and the placenta communicate during pregnancy, and open new ways of medically promoting normal development of placental vasculature.
By Andrei Ionescu, Earth.com Staff Writer