Investigating the regulation of processing bodies in Drosophila melanogaster oocytes

Cells are highly organised and rely on both membrane-bound and non-membrane-bound organelles to coordinate biological processes. Biomolecular condensates represent a broad class of non-membrane-bound organelles that assemble through phase separation. They exhibit diverse morphologies, compositions, material properties, and functions. A major subclass of biomolecular condensates is ribonucleoprotein (RNP) granules. These RNA-protein complexes play critical roles in mRNA localisation, translation, and degradation. Within this category, processing bodies (P bodies) are evolutionarily conserved RNP granules found in yeast to humans. In Drosophila melanogaster, P bodies play a crucial role in regulating the maternally deposited axis-determining mRNA, bicoid (bcd). In the mature oocytes, bcd is associated with P bodies and remains translationally silent. Upon egg activation, P bodies disassemble, releasing bcd into the cytoplasm where it associates with ribosomes and is translated. P body material properties are essential for this temporal control, as shown by disruptions to their properties can lead to premature bcd translation and impaired embryonic development. To understand how the material properties of P bodies are regulated in Drosophila oocytes, I used a combination of physiological stressors, genetic alterations, and imaging techniques to explore how both extrinsic and intrinsic factors impact the condensates. My work demonstrates that external stresses such as heat, starvation, and ionic imbalance promote P body assembly. At the molecular level, although the intrinsically disordered regions (IDRs) of a core P body protein are dispensable for condensate assembly, they are critical for maintaining P body integrity in the mature oocytes. In addition, RNA is also found to be essential for sustaining P body integrity. My work shows the impact of ageing on P body morphology, material properties, and functions. Using three distinct ageing models—organismal ageing, oocyte ageing, and high-protein diet (HPD)-induced premature ageing—I found that P bodies undergo a material property transition after ageing. The solidification of P bodies disrupts their disassembly upon egg activation, leading to continued bcd association and impaired translation. To explore the underlying mechanisms of this ageing-associated change, I investigated reactive oxygen species (ROS). Elevated ROS levels are sufficient to induce premature P body solidification. Conversely, reducing ROS levels effectively preserves P body function, suggesting that oxidative stress is a driver of age-related changes in P body material properties. Taken together, these findings reveal that the material properties of P bodies are regulated by both extrinsic and intrinsic factors, including stress, molecular composition, and ageing. Disruption of these properties can impair translational control during early development. More broadly, this work provides insight into the mechanisms governing biomolecular condensate regulation and offers a conceptual framework for understanding how age-related changes in condensate may contribute to cellular dysfunction across biological systems

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2025

Author dc:creator

• Hu, Tianhui

Advisor dc:contributor.advisor

• Weil, Tim

• Development
• Drosophila
• mRNA translation
• RNP granules

Licence

• https://www.repository.cam.ac.uk/bitstreams/31cd8500-7cf7-4cac-a54a-fcb5c75dccb7/download
• http://purl.org/NET/rdflicense/allrightsreserved

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.125194

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/395797