This symposium, initiated in 2010, takes place every second year. Ever since, it brings together early-career and established researchers from all over the world who are interested in microtubule biology and its impact on human health and disease.

Last month, we had the pleasure to host another successful edition of ‘Microtubules: from atoms to complex systems’, welcoming on-site and virtual participants, bringing together researchers from different disciplines interested in microtubule research. The 2024 edition of the symposium featured inspirational keynote and landmark lectures, a large number of short talks, networking activities , and, among other highlights , two poster sessions. From 219 posters presented during the event, the participants had the opportunity to vote for the best ones. Three best posters were selected, and we are thrilled to present our winners’ research.

Please give a round of applause to these brilliant minds!

We are pleased to share with you two of the awarded abstracts

Microtubules adopt a new type of lateral interaction in response to excessive protofilament skew

Presenter: Clément Bousquet

Collaborators: Romain Gibeaux, Matthieu Benoit, Denis Chrétien, Charlotte Guyomar

Abstract:

Departure from the classical 13 protofilaments, 3-start lateral monomer helix architecture, is common in microtubules assembled from purified tubulin, but also occurs in different organisms and cells types. The microtubule lattice accommodates this structural polymorphism by a global skew of the protofilaments in order to preserve the lateral and longitudinal interactions between tubulin subunits, a mechanism geometrically described by the ‘microtubule lattice accommodation model’. Here, we analyzed by cryo-electron microscopy microtubules assembled in the presence of GDP-BeF3- and GTPγS, two slowly hydrolysable GTP-analogues. We find that in the presence of these analogues, microtubules can adopt configurations with protofilament skew angles up to 3°, but most of them relax to lower values likely as a response to tortional stress. Abrupt transitions between stressed and relaxed lattices are occasionally observed within the same microtubules, suggesting a cooperative relaxation process. To visualize this mechanism, we decorated microtubules with kinesin motor domains, analyzed their structure by cryo-electron tomography, and performed segmented sub-tomogram averaging to reveal the underlying tubulin dimer organization within individual microtubules. This analysis revealed long-range dislocations of about 20 Å between two protofilaments, not necessarily at the seams made of heterotypic αβ-lateral interactions. We propose that this relaxation mechanism preserves microtubules from torsional stress induced by high protofilament skew, which could otherwise destabilize the microtubule lattice and induce their depolymerization in dynamic assembly conditions, a stochastic event know as catastrophes

Due to the confidentiality of the unpublished data, we cannot share the poster.

Center on centrosomes: how CLASPs control microtubule density

Presenter: Lilian Sluimer

Collaborators: Keri Schmidt, Robin Hoogebeen, Dipti Rai, Misko Bobeldijk, Arianna Sandron, Fangrui Chen, Anna Akhmanova

Abstract:

Cytoplasmic linker-associated proteins (CLASPs) are critical for microtubule stabilization, nucleation and lattice repair, and are therefore considered core regulatory factors of the microtubule network. Due to their essential role in mitosis, a partial depletion of both mammalian CLASP homologs leads to mitotic arrest and a double gene knock out is lethal.

In order to gain a full understanding of their function we have developed a cellular system in which both CLASPs are severely depleted. Upon knockdown, we note a striking reduction in microtubule density, which can be partially attributed to a decrease in microtubule nucleation from the Golgi and microtubule plus-end stabilization. Interestingly, we also observe impaired microtubule nucleation from the centrosome. Previously, mass spectrometry data reported centriolar proteins Ninein and CPAP to be novel candidate binding partners of CLASP1. Ninein is crucial for nucleating and anchoring microtubules at the subdistal appendages of the mother centriole, whereas CPAP regulates centriole assembly and length. In light of the disrupted centrosome function observed upon CLASP knockdown, we are currently investigating the interactions between CLASP-Ninein and CLASP-CPAP to explore its potential involvement in centriole biogenesis.

View poster

The EMBO | EMBL Symposium ‘Microtubules: from atoms to complex systems’ took place from 5 – 8 June 2024 at EMBL Heidelberg and virtually.