PhD project

Supervisor: Jordan Raff

Eukaryotic cells are packed with organelles, the number and size of which appear to be tightly regulated. In proliferating cells, the amount of each organelle typically doubles prior to cell division, but the mechanisms that ensure cells make the right amount of each organelle—at the right time and at the right place—are very poorly understood. Centrioles are an excellent model for studying this problem, as almost every cell in your body is born with a just single pair of centrioles. These tiny structures organise two crucial organelles—cilia and centrosomes—that have vital roles in many aspects of cellular organisation (e.g. cell division, cell polarity, cell signalling). The dysfunction of these organelles has been linked to a bewildering plethora of human diseases, including cancer, obesity, retinal degeneration and microcephaly/dwarfism, but the mechanisms linking these pathologies to organelle dysfunction are poorly understood. These organelles are probably composed of >400 different types of protein, yet they can assemble in just a few minutes. Our goal is to understand the principles that allow cells to build these complicated nanomachines with such precision, and how mistakes in the assembly process can lead to such a variety of human diseases.

We recently individually knocked-out most of the ~13,000 genes in fly cells and found that, surprisingly, only ~12 are actually essential for centriole and centrosome assembly (the cells we used for these studies don’t make cilia, so we couldn’t assess cilia assembly). Remarkably, similar studies in worms identified a nearly identical set of genes, indicating that these assembly pathways are highly conserved. In this project you will use advanced microscopy techniques to study the behaviour of fluorescently-tagged versions of normal and mutated versions of these key assembly proteins in living fly embryos. These embryos are ideal for studying centriole and centrosome assembly as we can observe 100s of centrioles and centrosomes as they proceed through multiple rounds of assembly in a short period of time. We are developing sophisticated tools to extract quantitative information about how centrosomes and their constituent parts behave. These studies are allowing us to work with mathematicians to formulate and test models about how these proteins work together to ensure that centrioles and centrosomes assemble at the right time, in the right place, and grow to the right size. We have also recently made exciting progress in trying to reconstitute centriole and centrosome assembly on the surface of synthetic beads. These studies are revealing some interesting and surprising principles that govern organelle assembly, providing important clues as to how these highly structured nanomachines function in health and disease.

Keywords:

• Biochemistry, Biomedical Engineering, Cell Biology/Development, Genetics, Molecular Biology, Structural Biology

Publications:

• Wong, S-S et al. (2024). Regulation of centrosome size by the cell-cycle oscillator in Drosophila embryos. EMBO J., Doi: 10.1038/s44318-023-00022-z
• Wong, S-S et al. (2022). Centrioles generate a local pulse of Polo/PLK1 activity to initiate mitotic centrosome assembly. EMBO J., Doi: 10.15252/embj.2022110891.
• Aydogan, et al. (2020). An autonomous oscillation times and executes centriole biogenesis. Cell, Doi: 10.1016/j.cell.2020.05.018. PMC7327525
• Conduit P.T., et al. (2015). Centrosome function and assembly in animal cells. Nat. Rev. Cell and Mol. Biol. Doi: 10.1038/nrm4062.