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bioRxiv · 10.1101/2021.08.18.456780

A mitotic screen in Indian muntjac cells unveils how Augmin drives kinetochore fiber maturation

Almeida, A. C.·Oliveira, J.·Drpic, D.·Cheeseman, L.·Damas, J.·Lewin, H. A.·Larkin, D.·Aguiar, P.·Pereira, A. J.·Maiato, H.
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Abstract

Chromosome segregation in mammals relies on the maturation of a thick bundle of kinetochore-attached microtubules known as k-fibers. How k-fibers mature from initial kinetochore-microtubule attachments remains a fundamental question. By combining functional perturbations in Indian muntjac, a placental mammal with the lowest known chromosome number (n=3) and distinctively large kinetochores, with fixed- and subsecond live-cell super-resolution CH-STED nanoscopy, we uncovered the mechanism by which Augmin mediates k-fiber maturation. Augmin promoted kinetochore microtubule turnover by sustaining microtubule formation from kinetochores and poleward flux, regardless of pioneer centrosomal microtubules. Tracking of microtubule growth events within individual k-fibers revealed a wide angular dispersion, consistent with Augmin-mediated branched microtubule nucleation. Augmin depletion reduced the frequency of microtubule growth events within k-fibers and hampered normal repair after acute k-fiber injury by laser microsurgery. Our work underscores the contribution of microtubule formation from kinetochores and Augmin-mediated microtubule amplification for k-fiber maturation and spindle assembly in mammals.

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Almeida, A. C., Oliveira, J., Drpic, D., Cheeseman, L., Damas, J., Lewin, H. A., Larkin, D., Aguiar, P., Pereira, A. J., Maiato, H.. 2021-08-18. A mitotic screen in Indian muntjac cells unveils how Augmin drives kinetochore fiber maturation. https://doi.org/10.1101/2021.08.18.456780

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