MiRNA, short non-coding RNA, play a critical role in cell homeostasis by negatively regulating target mRNA and corresponding protein expression. Thus, any loss of regulation associated with miRNA may have important consequences on essential biologic systems like embryogenesis or ageing or cancer.
The aim of this project was to study new mechanisms of physiologic regulation of miRNA during cellular processes or intercellular exchange of material. Indeed, research field on microvesicles dramatically expanded over the last years, mainly in the topic of intercellular transfer of molecules. However, the fate of extracellular miRNA (ex-miRNA), phagocytosed by recipient cells was not known. Here, our work highlights the rapid decay of these ex-miRNAs by XRN1 exonuclease during an extremely dynamic process. This model not only underlines that the reprogramming to a new phenotype could be imprinted by miRNAs transferred from one cell to the next one but importantly for only a short period of time. Obviously, this discovery helps us to rethink significantly our vision of the function of ex-miRNA in diverse biologic systems based on intercellular communications.
In order to show the intercellular transfer of miRNA, we setup a model in witch miRNAs (Mir-223-3p et miR-143-3p) were 1/specifically expressed in donor cell (neutrophils) and 2/undetectable in recipient cell (epithelial cell). This smart approach allowed quantifying the level of transferred miRNA with a high sensitivity and specificity.
This model helps us to confirm the transfer of miRNA between adjacent cells was very active. Interestingly, in the case of the donor cells are removed or the transfer is stopped, the level in recipient cells of the phagocytosed extracellular miRNA decays faster than endogenous miRNA. Thanks to a screening by siRNA of most exonucleases present in human cells, our system allows us to identify XRN1 exonuclease as a major regulator of the phagocytosed extracellular miRNA half-life. In conclusion, this is the first demonstration of the role of an exonuclease in the specific decay of extracellular miRNAs. Such results are particularly important in term of miRNA deregulation that could occur in numerous pathologies.
Based on our results, we suggest that we have to revise our vision about miRNA and intercellular communications. This highlights a novel process of regulation of ex-miRNA by XRN1 exonuclease, which function on miRNA in humans was unknown. Moreover, it seems that numerous subpopulations of miRNA exist in the cell and may have different half-life given some modifications that could occur, but many efforts have to be done to understand the role of these subspecies and their functions.
These results have been published in an international peer-reviewed journal (Nucleic Acid Research. 2017), one review (Médecine et Sciences), and have been presented in prestigious institutes (ex : NIH, Bethesda ; IGR, Villejuif) and international congress (ex : AACR, 2017). In a socio-economic point of view, all these results conducted to a scientific collaboration with TELOMIUM start-up started in 2016.
A large number of human diseases such as cancer have a multifactorial etiology which involves both genetic and environmental factors. Genome wide association studies have already identified a huge number of genetic variants associated with diseases. However, the “genopathology” (ie. the molecular mechanisms associating Single Nucleotide Polymorphism (SNP) with compromised pathways and diseases) of these alleles remain to be determined.
Our recent work (Nature Genetics) leads to a description of mechanism involving synonymous SNP and their consequences on mRNA expression. Therefore, our studies highlight microRNA “misbinding” as an integrative complex model of interaction between genetic determinism and environmental factors (that are possibly involved in miRNA expression regulation).
Our project aims to confirm this model of miRNA/SNP interaction on new targets by combining bioinformatics, and cellular and molecular biology in vitro and ex vivo
On the genetic field (Aim 1), the goal of this project is to analyze the consequences of microRNA misuse by synonymous polymorphisms on well-known associated cancer TERT gene expression.
In parallel, on the oncogenesis field, the consequences of synonymous polymorphism on TERT expression will be investigated ex vivo on melanoma and lung cancers, and combined with patient clinical features (Aim 2). The combined aims of our project will give new clues to develop potential biomarkers and therapy in personalized medicine based on genotype and microRNA expression.
In order to fulfill these ambitious objectives, we have developed complementary approaches bioinformatics algorithm, in vitro experiments and ex vivo validation in human samples. To be done, the project will be completed by a team composed by a young INSERM researcher (Principal Investigator), a INSERM technician, a postdoc, and a Ph.D student, all full-time associated with the project, and with a bioinformatics researcher, biology researchers, hospital patricians and technicians for scientific and technic help.
Monsieur Patrick Brest (Centre Cancer et Vieillissement) – email@example.com
The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.
IRCAN UMR7284 Centre Cancer et Vieillissement
Help of the ANR 280,840 euros
Beginning and duration of the scientific project: December 2012 - 36 Months