The "genetic war" began in the womb

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British scientists have discovered a key signal used by a fetus to control the supply of nutrients to the placenta, thus revealing a tug-of-war between genes inherited from father and mother. The study was published In Developmental Cells on December 27.

The study in mice may help explain why some fetuses are stunted in the womb.

The placenta is a special tissue that contains cells from the baby and the mother. The fetus receives nutrients through blood vessels in the placenta. These blood vessels dilate sharply in the second and third trimesters of pregnancy. At term, the total length of blood vessels is about 320 km.

As it develops, the fetus needs to communicate its increasing food needs to the mother. However, in humans, 10% to 15% of fetuses are stunted in the womb, during which the growth of blood vessels in the placenta slows down.

The Cambridge university team used genetically engineered mice to show how fetuses produce signals that promote the growth of blood vessels within the placenta. This signal also causes changes in other cells in the placenta, which deliver more nutrients from the mother to the fetus.

"When a fetus grows in the womb, the mother is required to provide 'food', and healthy blood vessels in the placenta are essential to help the fetus get enough nutrients. We have identified a way for the fetus to communicate with the placenta to promote the correct dilation of blood vessels. Irnel Sandovici, first author of the research paper, said.

The team found that the fetus sends a signal called IGF2. This signal reaches the placenta through the umbilical cord.

During the 29th week of human pregnancy to term, the level of IGF2 in the umbilical cord gradually increases. Too much IGF2 is associated with hypergrowth, but if IGF2 is insufficient, it can cause growth to be too slow. Fetuses that are too large or too small are difficult to give birth to, and can even die. Even if born smoothly, they are at higher risk of developing diabetes and heart disease in adulthood.

"We know that IGF2 can promote organ growth. This study shows that IGF2 can also function like a classic hormone — produced by the fetus, entering the bloodstream and entering the placenta through the umbilical cord, playing a role in the placenta. Sandovici said.

More interestingly, the researchers discovered and revealed a fight that took place in the womb.

In mice, the response of placental blood vessels to IGF2 is mediated by another protein called IGF2R. The two genes that produce IGF2 and IGF2R leave a "mark", that is, the molecular switch recognizes its parental origin and controls the switch gene. In this case, only the igf2 gene copy inherited from the father or only the igf2r copy inherited from the mother is active.

Lead author Miguel Constancia of the study paper said: "Our study found that genes from the father drive the fetus to produce demand for larger blood vessels and more nutrients, while maternal genes in the placenta try to control the amount of nutrients provided by the mother. A tug-of-war at the genetic level begins. ”

Scientists say the study helps to better understand how fetuses, placentas and mothers are interconnected during pregnancy. This may help to obtain methods for measuring fetal IGF2 levels, as well as methods for normalizing their levels by drugs or promoting the normal development of the placental vascular system. (Xu Rui)

Source: China Science Daily