The discovery of microRNAs, awarded the Nobel Prize in Medicine on Monday, shows how complex our genes work. However, it remains to be seen to what extent their knowledge can help develop effective treatments.
What is a microRNA?
These are pieces of ribonucleic acid (RNA). Present in all our cells, RNA is synthesized by our body from the genes gathered in our DNA.
MicroRNAs do not play the best-known role of RNA, that of intermediary between our genes and the production of the myriad proteins that make our bodies function, for which we speak of messenger RNA.
MicroRNAs are part of so-called "non-coding" RNA: they are not translated into proteins.
But that doesn't mean they don't play a role. The discovery of microRNAs in the 1990s by Victor Ambros and Gary Ruvkun, both Nobel laureates on Monday, showed that our genome is not just a straight line between DNA, RNA and then proteins.
How do microRNAs work?
" The discovery of microRNAs has brought an additional level of complexity by revealing that regions that were thought to be non-coding play a role in gene regulation," Benoît Ballester, a researcher at Inserm and specialist in the non-coding genome, explained to AFP.
These microRNAs interfere with the functioning of messenger RNA: " It's like a Velcro that attaches to it and prevents it from being translated into proteins," says Mr. Ballester.
Consequence: some genes are expressed little or not at all - they are inhibited -, and others in a more marked manner - they are intensified.
However, we should not imagine micro-RNAs as a form of internal parasites that would spoil the proper functioning of our genome.
They form " an integral part of the regulation of our genome, it is as important as the classic translation of a gene into protein ", underlines the specialist in the non-coding genome.
Why is this so interesting?
The discovery of the first microRNA by Victor Ambros in 1993 was not immediately hailed as a major breakthrough.
The researcher was a specialist in the biology of certain worms, and it was in one of them (a one-millimeter roundworm called C. elegans) that he identified the existence of micro-RNA.
" Nobody really paid attention," Eric Miska, a geneticist at the University of Cambridge, told AFP, admitting that it took years to see anything other than " a weird thing in worms."
It was in 2000 that Gary Ruvkun identified the existence of similar mechanisms in humans, opening the way to a whole new area of genomics.
" This tiny piece of RNA, so important for the development of this little worm, we also have it, you and I," underlines Eric Miska. " And it even plays an essential role, since it prevents the appearance of tumors."
What concrete repercussions?
While knowledge of microRNAs already allows us to better understand our genome, it remains to be seen whether they can be used as a lever for action to cure diseases. For several years, many biotechnology companies have been banking on this avenue.
This is particularly a promising area against cancers, with the idea of establishing highly targeted treatments. This research is part of a broader context in which we understand better and better how tumors can develop differently at the molecular level from one patient to another.
However, against cancer or other pathologies, there is still " nothing that is close to a real application ", Gunilla Karlsson Hedestam, professor at the Karolinska Institute, told the press during the announcement of the Nobel Prize in Stockholm.
MicroRNAs are indeed a complex target to manage due to their instability.
But, without necessarily making them the basis of a drug, many researchers hope first to use them as a "biomarker", that is to say a diagnostic tool which would allow, for example, the identification of what type of cancer the patient is facing.
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