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bioRxiv · 10.1101/2025.02.17.638590

The Mn-motif protein MAP6d1 assembles ciliary doublet microtubules

Gopal, D.·Wu, J.·Delaroche, J.·Bosc, C.·de Andrade, m.·Denarier, E.·Effantin, G.·Andrieux, A.·Gory-Faure, S.·serre, l.·Arnal, I.
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Abstract

Most eukaryotic cells have cilia that serve vital functions in sensing, signaling, motility. The core architecture of cilia is an array of microtubule doublets, which consist of a complete A-tubule and an incomplete B-tubule. The mechanisms governing the assembly of this complex structure remain poorly understood. Here, using total internal reflection fluorescence microscopy and cryo-electron tomography, we investigate the role of MAP6d1, a brain-specific protein containing microtubule lumen-targeting Mn-motifs. We show that MAP6d1 assembles stable microtubule doublets by recruiting tubulin dimers onto the lattice of the A-tubule to initiate the nucleation of the B-tubule. MAP6d1 also promotes the formation of luminal protofilaments in singlet and doublet microtubules, a previously undescribed phenomenon that likely enhances microtubule stability. In neurons, MAP6d1 localises to the proximal part of primary cilia via its Mn-motif, with its loss resulting in shortened cilia, a characteristic of ciliopathies. MAP6d1 is thus the first microtubule-associated protein found to assemble microtubule doublets, uncovering new functions for Mn-motif proteins in neurons.

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Gopal, D., Wu, J., Delaroche, J., Bosc, C., de Andrade, m., Denarier, E., Effantin, G., Andrieux, A., Gory-Faure, S., serre, l., Arnal, I.. 2025-02-17. The Mn-motif protein MAP6d1 assembles ciliary doublet microtubules. https://doi.org/10.1101/2025.02.17.638590

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