Naslov
Microtubule pivoting ensures passage of polar chromosomes across the centrosome required for timely alignment

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

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Skup
Biophysics of Spindle Assembly

Mjesto i datum
Zagreb, Hrvatska, 10.10.2022. - 11.10.2022

Vrsta sudjelovanja
Predavanje

Vrsta recenzije
Podatak o recenziji nije dostupan

Ključne riječi
Polar chromosomes ; Congression ; Prometaphase

Sažetak
To ensure faithful mitosis, chromosomes located at different nuclear positions during nuclear envelope breakdown need to properly congress to the metaphase plate. The most unfavorably positioned chromosomes are polar chromosomes, located behind the spindle pole at nuclear envelope breakdown. These chromosomes first need to approach the spindle pole from the back and at a later point slide towards the metaphase plate in a motor-dependent manner. However, the mechanism of their passage across the polar region and its importance for faithful mitosis remain unknown. Here we show, by using live-cell confocal microscopy with high spatial and temporal resolution, that polar chromosomes are the last to reach the metaphase plate. They stall behind the pole, indicating that the centrosome creates a physical barrier to their movement. To test this hypothesis, we removed one centrosome using centrinone, which resolved the observed delay in the congression of polar chromosomes and suggested the existence of an additional and distinct mechanism of congression in a polar region. By imaging the microtubule plus end marker EB3, we reveal that this mechanism is based on pivoting of astral microtubules with attached chromosomes around the spindle pole. 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 either stop or reverse spindle elongation, we confirmed that pivoting occurs due to a hydrodynamic drag force created by centrosome movement. Superresolution STED microscopy of astral microtubules and Mad2, a marker of unstable attachments, revealed that polar chromosomes are mostly laterally attached to one astral microtubule emanating from the pole behind which they are situated, with other more complex attachments observed less frequently. Finally, we show that polar chromosomes are prone to misalignment and cause aneuploidy in the majority of cases when the spindle checkpoint is weakened, highlighting their importance in faithful chromosome segregation. 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.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

POVEZANOST RADA