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, sažetak, znanstveni

Skup
EMBO Workshop Dynamic kinetochore

Mjesto i datum
Oslo, Norveška, 28.06.2022. - 01.07.2022

Vrsta sudjelovanja
Poster

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 approximately 7 out of 46 chromosomes, termed polar chromosomes, are positioned behind the pole at NEB in human cells. These polar chromosomes first approach the spindle pole with the help of kinetochore dynein and subsequently undergo CENP-E mediated sliding towards the equator [1, 2]. However, the mechanism of their passage across the polar region and its importance for faithful cell division remain unknown. Here we show that polar chromosomes are particularly prone to missegregation when the checkpoint is weakened. These chromosomes stall behind the pole and acquire speed similar to non- polar chromosomes once they reach the spindle body, indicating that the centrosome creates a physical barrier for chromosome movement in this area. To test this hypothesis, we removed one centrosome using centrinone, which indeed resolved the observed delay in the congression of polar chromosomes and suggested that they must have an additional and distinct mechanism of congression. Imaging of EB3, a microtubule plus end marker, revealed that astral microtubules attached to kinetochores of polar chromosomes pivot around the spindle pole and thereby transport polar chromosomes towards the spindle body. The angle that the kinetochores of these chromosomes form with the spindle axis changed during the period of rapid spindle elongation, indicating a role of centrosome separation in this process. By using different kinesin-5 (Eg5) inhibitors to perturb the sliding of antiparallel microtubules and consequently stop or reverse spindle elongation, we confirmed that pivoting occurs due to a hydrodynamic drag force created by centrosome movement. Stimulated emission depletion (STED) imaging of astral microtubules and Mad2, a marker for absent or immature end-on attachments, showed that during pivoting, both kinetochores of a polar chromosome typically attach to a single microtubule laterally, with more complex attachments observed less frequently. Altogether, we propose a model in which pivoting of microtubules around the spindle pole, driven by spindle elongation, promotes the movement of polar chromosomes towards the spindle body and consequently their proper congression to the spindle equator. [1] Barisic et al. Kinetochore motors drive congression of peripheral polar chromosomes by overcoming random arm-ejection forces. Nat Cell Biol, 16(12): 1249-1256 (2014) [2] Kapoor et al. Chromosomes can congress to the metaphase plate before biorientation. Science, 311(5759): 388-391 (2006)

Izvorni jezik
Engleski

Znanstvena područja
Biologija, Interdisciplinarne prirodne znanosti

POVEZANOST RADA