Flagellar Assembly, Organisation and Function: Insights from Trypanosomes as a Divergent Model System

Flagella, also known as cilia, are microtubule-based organelles present in most eukaryotic cell types. In humans, defects in flagella can lead to genetic diseases called ciliopathies, and flagellar function is essential for virulence and transmission of protozoan pathogens, such as African trypanosomes. Motile flagella exhibit a rhythmic "beat" that is used for cellular propulsion and for moving liquid across tissues. This beat is powered by dynein motor proteins that are fixed along the nine outer doublet microtubules of the flagellar axoneme. For the beat to be rhythmic, the activity of dynein is meticulously coordinated by a central pair (CP) of microtubules and its associated projections. Using trypanosomes as a model system, our research focuses understanding a flagellar subdomain at the axoneme base called the transition zone (TZ). The TZ is the progenitor of the axoneme and it has a central role in flagellar assembly, maintenance and function. Moreover, the TZ is a ciliopathy “hotspot”, with many TZ protein complexes being ciliopathy complexes.

Using an innovative proteomics technique combined with genome-wide protein tagging, we have comprehensively determined the composition of the flagellar TZ. We have used this knowledge to probe TZ function, identifying sets of proteins with distinct functions within the TZ structure. We identify a mechanism of TZ length regulation and discover a Central Pair Assembly Complex (CPAC) that is required for initiation of the axonemal CP. Using ultra-expansion microscopy (UExM), we determine the nanoscale organisation and orientation of CPAP components within the TZ. Finally, leveraging the trypanosome’s divergent evolutionary position, we've harnessed machine learning techniques on evolutionary data to discover new, highly conserved, ciliary gene families and we use trypanosomes as a platform to assess their function. Some of these families are linked with human ciliopathies and we hope to include them in new genetic screens.

I completed my PhD on the trypanosome life cycle with Keith Matthews in Edinburgh, where we discovered a family of proteins that transduce the trypanosome differentiation signal. Building on this success, I secured a Wellcome Trust fellowship and moved to the University of Oxford to work with Keith Gull. There, I continued my work on trypanosomes, diving deeper into their cell biology and also creating new tools for the community. During this time, I founded TrypTag (http://tryptag.org), a ground-breaking new resource that determined the location of all trypanosome proteins using fluorescent protein tags and live-cell fluorescent microscopy. Since 2020, I've been leading my group at the University of Warwick, focusing on trypanosome flagella and other aspects of their cell biology. We're also working on identifying drugs and developing new treatments for trypanosome infections. Over the years, I've published in top-tier journals, such as PNAS, eLife, and Nature, and I'm currently an early career editor for MBoC.