RNA-protein granules as a mechanism for translational control

Image caption: Drosophila nurse cells and oocyte, actin (orange), cytoplasm (cyan), nuclei (blue).

Supervisor: Professor Tim Weil

The establishment of the body axes in many animals depends on the spatiotemporal regulation of mRNAs. Throughout development mRNAs are bound by regulatory proteins, and under certain conditions, these complexes can assemble into larger biomolecular condensates. Also referred to granules, these membraneless macromolecular compartments function as subcellular organisational hubs and reaction crucibles. Examples of condensates include the mitochondrial cloud in Xenopus, Balbiani bodies in zebrafish, P granules in C. elegans, and Processing bodies, which are conserved from plants to yeast to mammals. While many condensates are present in oocytes and early embryos, the precise biological functions of these complexes remain unclear. More broadly, condensates have been implicated in various human diseases, including Fragile X Syndrome, schizophrenia, spinal muscular atrophy, and cancer. 

This project aims to establish: (1) that mRNA association with a condensate restricts translation, (2) that mRNA disassociation from a condensate permits translation, and (3) the mRNA sequences, protein domains, and environmental requirements for translational regulation via condensates.

These aims will be met using Drosophila egg chambers and early embryos to enable a detailed mechanistic analysis of condensates in vivo. A combination of approaches will be applied to this model  system, these include: monitoring active translation with the SunTag system, analysing colocalisation between mRNA and condensates with single molecular fluorescent in situ hybridisation (smFISH) and immunolabeling with nanobodies, manipulation of protein and mRNA expression with mutant and RNAi expressing animals, alteration condensate physical states with chemicals and changes to the intracellular environment, and visualisation with high-resolution microscopy.

By experimenting on the dynamic relationship between mRNA and condensates inside of developing cells, this project will further our understanding of the spatiotemporal regulation of translation and plasticity of condensates in time. Overall, this work will address fundamental questions relating to the function of in vivo biomolecular condensates as they relate to developing organisms, stress and disease.

For more information, please visit Weil Lab or contact Prof Tim Weil.

References

Wilby EL and Weil TT, Relating the Biogenesis and Function of P Bodies in Drosophila to Human Disease. Genes. 2023; 14(9):1675. doi.org/10.3390/genes14091675

Sankaranarayanan M et al., Adaptable P body physical states differentially regulate bicoid mRNA storage during early Drosophila development. Dev Cell. 2021; 56(20). doi: 10.1016/j.devcel.2021.09.021

Shin Y and Bragwynne CP, Liquid phase condensation in cell physiology and disease. Science. 2017; 357(6357). doi: 10.1126/science.aaf4382.