Naslov
Polar chromosomes in human cells congress by microtubule pivoting

Autori
Štimac, Valentina ; Koprivec, Isabella ; Tolić, Iva M.

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, neobjavljeni rad, znanstveni

Skup
13th ÖGMBT Annual Meeting "From Molecular Machines to Translational Medicine"

Mjesto i datum
Beč, Austrija, 20.09.2021. - 14.10.2021

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Podatak o recenziji nije dostupan

Ključne riječi
Prometaphase ; Congression ; Polar

Sažetak
During mitosis, the cell forms a spindle that equally segregates chromosomes into two daughter cells. Soon after nuclear envelope breakdown (NEB), kinetochores on chromosomes are captured by microtubules nucleated at the spindle pole. Some chromosomes immediately find themselves in the area between two spindle poles, yet ~7 out of 46 human chromosomes positioned behind the pole at NEB first need to approach the spindle pole and subsequently travel to the equatorial plane. Once they approach the pole, the question remains how these unfavorably positioned chromosomes make their way across the centrosome as a physical barrier and reach the spindle body, from where they can continue their congression towards the equator. Here we show that astral microtubules attached to kinetochores of polar chromosomes pivot around the spindle pole and thereby transport polar chromosomes towards the spindle body. Stimulated emission depletion (STED) imaging of fixed samples typically showed that, during pivoting, both kinetochores of a polar chromosome laterally attach to a single microtubule, with other more complex attachments observed less frequently. This was consistent with the presence of the checkpoint protein Mad2 on both kinetochores, as well as with the analysis of end- binding protein 3 (EB3) comets which predominantly passed close to both kinetochores. The angle that the kinetochores of these chromosomes form with the spindle axis changed during a period of rapid spindle elongation, indicating the role of centrosome separation in this process. By using different kinesin-5 (Eg5) inhibitors to perturb the sliding of antiparallel microtubules and either stop or reverse spindle elongation, we confirmed that pivoting occurs due to a hydrodynamic drag force created by centrosome movement. Confocal and STED live-cell microscopy revealed that just before the end of pivoting, spindle body microtubules capture the distal kinetochore of a polar chromosome, leading to an increase in interkinetochore distance and landing of the kinetochore pair on the spindle surface. Pivoting as a mechanism of chromosome congression ensured timely mitosis, as polar chromosomes that failed to reach the spindle body by the end of spindle elongation significantly delayed anaphase onset. Altogether, we propose a model in which pivoting of microtubules around the spindle pole, driven by spindle elongation, promotes the movement of peripheral chromosomes towards the spindle body and consequently their proper congression to the spindle equator.

Izvorni jezik
Engleski

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