Researchers from a lab in the Physics of Living Systems Section, led by Erwin J. G. Peterman, have developed an elegant fluorescence microscopy approach called small-window illumination microscopy (SWIM) that allow them to visualize the fast intracellular dynamics of individual protein molecules inside neurons of living Caenorhabditis elegans worms, over long durations of time (>1hr). This approach has helped them understand how the intricate intracellular machinery works to drive and regulate the composition and distribution of proteins within the cilia of sensory neurons — the sensory organelles of these worms.
Sensory cilia are vital, antenna-like organelles in eukaryotic cells that detect external stimuli and transmit signals, influencing gene expression and cell behaviour. They are isolated from the cell's interior by a diffusion barrier, creating a unique environment rich in membrane proteins and enzymes involved in various signalling pathways. The heterogeneity within the cilium is maintained by intraflagellar transport (IFT), which involves large protein train complexes continuously moving back and forth along the length of the cilium (a few micrometres long). IFT is essential for the entry, exit, and distribution of ciliary proteins, with disruptions leading to ciliopathies, a group of over 30 syndromic diseases affecting multiple tissues. Sensory cilia of C. elegans provide an effective model to understand the fundamental mechanisms orchestrating this transport system.
In a new study published in Science Advances [1] and another recently published one in Nature Communications [2], Aniruddha Mitra and other members of the Peterman laboratory have unravelled how different components of the IFT train complex are recruited and sorted at the base of the sensory cilia. The authors also provide a comprehensive molecular picture on how IFT trains, which are densely packed, polymeric structures (~80 MDa), self-assemble and associate with cargoes as well as motor proteins, which drive them across the diffusion barrier, into the cilium. They found that assembly of IFT trains is a highly regulated, stepwise process, indicating that each component plays a specific role in assembly.
These findings not only enhance our understanding of ciliary transport but also have implications for addressing ciliopathies such as Bardet-Biedl syndrome and polycystic kidney disease. As research progresses, the insights gained from these studies may lead to new therapeutic strategies targeting cilia-related dysfunctions.
[1] A. Mitra, E. Gioukakis, W. Mul, E.J.G. Peterman, Delivery of intraflagellar transport proteins to the ciliary base and assembly into trains. Science Advances 11(14), eadr1716 (2025)
doi: 10.1126/sciadv.adr1716
[2] A. Mitra, E. Loseva, E. J. G. Peterman, IFT cargo and motors associate sequentially with IFT trains to enter cilia of C. elegans. Nature Communications 15, 3456 (2024)
doi: 10.1038/s41467-024-47807-2
Image courtesy: Elizaveta Loseva