The molecule – miR-675 – is a type of short nucleic acid called microRNA. RNA molecules have long been known to provide an intermediary in the process of translating genes from the cell’s DNA into proteins that are necessary for the cell’s function. However, there are also many RNA molecules that do not encode proteins, such as microRNAs, whose exact function remains unknown.
The noncoding RNA H19 is one of the most abundant RNA molecules found in mammals, but until now its function was unknown. This study – in collaboration with academics in France, the USA and Belgium – is the first to show that a microRNA called miR-675 is ‘cut out’ and released from the longer H19 RNA in the placenta and that this slows placental growth before birth.
Dr Andrew Keniry from the Babraham Institute, the lead author of the study, explained, “The function of the H19 noncoding RNA has proven elusive for many years. We have shown that it appears to act as an inert molecule used to store the functional miR-675 until it is required by the cell to slow placental growth.
“This is a very exciting finding and reveals a new purpose for noncoding RNA. It is also intriguing that the release of miR-675 is controlled by a stress-response protein, suggesting this may be a mechanism the developing embryo can use to regulate its growth in the womb.”
Professor Wolf Reik, senior author of the paper and a group leader at the Babraham Institute, said, “It’s interesting to see how the growth of the placenta can be regulated in this flexible way before birth. Perhaps there are environmental signals and influences from the mother’s diet on the growth of the placenta and hence the healthy baby.
“It’s also fascinating how an RNA that is so abundant in the cell can be a quick-release reservoir of a growth regulating small RNA, and this may be generally important for how cell growth is regulated by the environment.”
Professor Michael Wakelam, director of the Babraham Institute, commented, “This research gives a new insight into how placental growth can be regulated, which is important for the health of the baby and in later life.”
The study was supported by the BBSRC, Wellcome Trust, MRC, EU, Cambridge Commonwealth Trust and the Centre for Trophoblast Research.
Image: A photomicrograph of a placenta (middle trimester). Credit: Wellcome Photo Library, Wellcome Images.
Keniry A et al. The H19 lincRNA is a developmental reservoir of miR-675 that suppresses growth and Igf1r. Nat Cell Biol 2012 (epub ahead of print).