Compartmentation and intracellular traffic of mRNPs

In eukaryotic cells, cytoplasmic mRNAs can be translated, degraded or stored, depending on the proteins that are bound to them. These proteins mediate a variety of post-transcriptional regulation pathways, which are essential for many aspects of cell physiology. Remarkably, many implicated factors and their target mRNAs accumulate in cytoplasmic membrane-less ribonucleoprotein (RNP) granules: P-bodies, stress granules, germ granules, neuronal granules, etc. These granules are also called condensates, as they form following liquid-liquid phase separation. Despite names, morphologies and molecular composition being different depending on the model organism, the cell type and the environmental conditions, all these granules contain repressed mRNAs. Our main goal is to understand how the molecular, cellular and physiological functions of these condensates differ from the functions of identical mRNPs diffuse in the cytoplasm. We want to decipher how do these granules assemble? What are their protein and RNA content and the dynamics of such content? What is their function in RNA metabolism, and more broadly in cell physiology?

We tackle these questions using a combination of experimental approaches including biochemical and cell imaging techniques, as well as proteomic and transcriptomic analyses. Most of our studies focus on P-bodies in human cells [1].

- How do they assemble? We have shown that three proteins are required for P-body assembly in human cells: the RNA helicase DDX6 and its partners LSM14A and 4E-T [2-5]. However, further progressing on the assembly mechanisms is limited by the high complexity of P-body composition (a hundred of proteins and thousands mRNAs). We therefore also turned to a synthetic biology approach, allowing us to study artificial granules that are made of a limited and controlled number of proteins and RNAs (collaboration with Zoher Gueroui, ENS Chimie). As a result we have shown how RNA at the surface of condensates impacts their number, their size and their physical properties [6,7]

- What is their protein and RNA content? What is their function in RNA metabolism? We have pioneered a method to purify P-bodies from cells, called Fluorescence Activated Particle Sorting (FAPS). This allowed us to identify their protein and RNA content by mass spectrometry and RNAseq, respectively. Their analysis, combined with polysome profiling experiments and in silico investigations, led us to draw two major conclusions: P-bodies store a large diversity of RNAs, most of them are coding but inefficiently translated, and they code for proteins with regulatory functions [1,8,9]; the mRNA GC-content is key to their localization in P-bodies (P-bodies only contain AU-rich mRNAs) and to post-transcriptional regulation in general (translation repression, mRNA decay pathways) [10,11]. This kind of approach opens up the possibility to investigate the dynamics of the P-body content in different conditions, diverse cellular environments and various cell types.

- What is their function in cell physiology? Established cell lines grow well in the absence of DDX6 expression, and therefore in the absence of P-bodies. However, in human, several heterozygous mutations in the DDX6 gene are responsible for mental retardation associated to neurodevelopmental defects. We have shown that the DDX6 mutations lead to a strong P-body defect in the patient cells, as well as to some mRNA post-transcriptional deregulation [12,13]. These findings constitute a unique entry point to understand the function of P-bodies and/or DDX6 during development.

Poster flash talk (5 min)


Poster presentation during the virtual meeting CSHL Translational Control

(Sept. 2020)


Lecture (1h30)


Lecture about mRNA cytoplasmic metabolism in mammalian cells for Master 1 students (in french)

(Feb. 2019)


1 Standart, N. and Weil, D. (2018) Trends Genet. 34, 612–626

2 Ayache, J. et al. (2015) Mol. Biol. Cell 26, 2579–2595

3 Kamenska, A. et al. (2016) Nucleic Acids Res. 44, 6318–6334

4 Vindry, C. et al. (2017) Cell Rep. 20, 1187–1200

5 Chauderlier, A. et al. (2018) Biochim. Biophys. Acta 1861, 762–772

6 Garcia-Jove Navarro, M. et al. (2019) Nat. Commun. 10, 3230

7 Cochard, A. et al. (2022) Biophys. J. 121, 1675-1690

8 Hubstenberger, A. et al. (2017) Mol. Cell 68, 144-157.e5

9 Courel, M. et al. (2018) Med. Sci. MS 34, 306–308

10 Courel, M. et al. (2019) eLife 8:e49708

11 Vindry, C. et al. (2019) Wiley Interdiscip. Rev. RNA 10(6):e1557

12 Balak, C. et al. (2019) Am. J. Hum. Genet. 105, 509-525

13 Weil et al. (2020) Biochem. Soc. Trans. 48, 1199-1211


  • Edouard Bertrand: IGMM, Montpellier, France
  • Nadège Bondurand: Institut Imagine, Paris, France
  • Daniel Gautheret: I2BC Saclay, France
  • Zoher Gueroui: ENS Paris, France
  • Judith Miné-Hattab: LCQB, IBPS
  • Gérard Pierron: Institut Gustave Roussy, Villejuif, France
  • Amélie Piton: IGBMC, Strasbourg, France
  • Hugues Roest Crollius: ENS Paris, France
  • Nancy Standart: University of Cambridge, UK
  • Izabela Sumara: IGBMC, Strasbourg, France