The “tubulin code” in control of molecular train logistics in cilia

By developing a sophisticated in vitro system coupled with advanced imaging techniques and CRISPR genome editing, an international team of researchers from Human Technopole (Italy) and the TUD Dresden University of Technology (Germany) shows that tubulin tyrosination/detyrosination regulates the bidirectional IFT train movement and avoids collision between trains moving in opposite directions along the cilium. The research was funded by the ERC and the DFG “Physics of Life” Excellence Cluster. The results are published in Nature Communications.

Cilia are hair-like organelles found on nearly all eukaryotic cells, playing crucial roles in cell signalling, movement, and fluid transport. Proper assembly and function of cilia rely on a sophisticated bidirectional transport system called intraflagellar transport (IFT). Just like in a railway station, this system uses microtubule tracks to ensure the ordered movement of molecular cargoes between the cell body and the tip of the cilium. Disruptions in IFT are linked to a variety of disorders, collectively known as ciliopathies, which include respiratory diseases, infertility, obesity, diabetes and metabolic disorders, cardiovascular disease, sensory impairments, neurological disorders and developmental abnormalities.

The groups of Gaia Pigino – Associate Head of the Structural Biology Research Centre at Human Technopole, Milan – and Stefan Diez – Professor for BioNanoTools at the B CUBE – Center for Molecular Bioengineering, Dresden – investigated the role of tubulin post-translational modifications, specifically tyrosination and detyrosination, in regulating IFT. The researchers demonstrated that detyrosination of specific microtubules within the cilium is critical for the smooth operation of IFT. Using Chlamydomonas reinhardtii green alga mutants lacking tubulin detyrosination, they observed frequent stoppages of IFT trains and misrouting of cargos. These disruptions caused collisions among trains moving in opposite directions and hindered ciliary growth.

Further experiments using synthetic microtubules in vitro revealed that anterograde IFT trains (which move toward the ciliary tip) prefer detyrosinated microtubules. In contrast, retrograde trains (which move back to the cell body) favour tyrosinated ones. This differential affinity helps segregate the two train types onto distinct microtubules, ensuring collision-free transport. In mutant cells, this segregation was no longer there, causing traffic jam and functional impairment of the cilia.

Pigino, Diez and colleagues identified a novel regulatory mechanism for IFT, where the “tubulin code”– encoded by post-translational modifications – acts as a molecular signal for sorting transport trains. This is the first evidence linking tubulin detyrosination to the spatial organisation of IFT trains. Moreover, the study introduces a cutting-edge method to reconstitute IFT train motility on synthetic microtubules, providing a controlled system to study these interactions at a molecular level.

This work marks a significant advance in our understanding of the molecular underpinnings of ciliary transport. By revealing how tubulin modifications direct IFT logistics, it addresses a long-standing question in the field of cilia biology. The results may have implications beyond basic science, as defects in ciliary transport are central to ciliopathies, such as polycystic kidney disease, primary ciliary dyskinesia, and retinal degeneration.

Additionally, the approach to reconstitute IFT in vitro offers a versatile platform for future research, because this method can be adapted to study other post-translational modifications and their effects on microtubule-associated processes

Cilia are not just crucial for cellular maintenance but also for embryonic development, sensory reception, and tissue homeostasis. Tubulin modifications play pivotal roles in maintaining these functions by influencing microtubule stability and motor protein behaviour. The study’s findings highlight how molecular fine-tuning within cilia is critical for their proper function, with broader implications for understanding diseases beyond ciliopathies, such as neurodegenerative disorders and cancer.

In summary, this research provides compelling evidence of how tubulin tyrosination and detyrosination regulate IFT, ensuring smooth and efficient ciliary transport. The findings deepen our understanding of the “tubulin code” and its functional significance in ciliary biology. Moreover, the development of an in vitro system to study IFT train motility is a methodological breakthrough that promises to accelerate research in this field.

Chhatre, A., Stepanek, L., Nievergelt, A.P. et al. Tubulin tyrosination/detyrosination regulate the affinity and sorting of intraflagellar transport trains on axonemal microtubule doublets. Nat Commun 16, 1055 (2025). https://doi.org/10.1038/s41467-025-56098-0