Naslov
Spindle twist culminates at anaphase onset and depends on microtubule-associated proteins along with external forces

Autori
Trupinić, Monika ; Kokanović, Barbara ; Ponjavić, Ivana ; Ivec, Arian ; Wadsworth, Patricia ; Fritz- Laylin, Lillian ; Pavin, Nenad ; Tolić, Iva.M.

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

Skup
Cell Bio Virtual 2020 | An Online ASCB|EMBO Meeting

Mjesto i datum
Sjedinjene Američke Države, 02.12.2020. - 16.12.2020

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
Mitotic spindle ; chirality ; twist ; helicity ; motor proteins

Sažetak
Equal division of the genetic material into two newly formed daughter cells is performed by the mitotic spindle, a complex micro-structure that consists of two poles, microtubule bundles extending between the poles, and a large number of associated proteins. During spindle formation, microtubule bundles adopt a ‘spindle’ shape, while navigating chromosomes to properly orientate within it. Individual microtubule bundles obtain different shapes depending on the forces acting on them, which are generated by motor proteins and microtubule dynamics. We have previously shown that the spindle shape in human cells is chiral as bundles are twisted along a left-handed helical path, and this chirality can be abolished by inactivation of the motor protein Eg5/kinesin-5 (Novak et al., Nat Commun 2018). However, it is not known how chirality changes throughout mitosis, how other microtubule- associated proteins affect it, and to what extent it is conserved. Here we show that spindles are more twisted in very late metaphase and early anaphase, compared to prometaphase and late anaphase. We also observed that round spindles are more twisted than elongated spindles, a notion that we then tested by applying an external force on the spindle poles which resulted in higher twist values. Furthermore, we tested additional motor and non- motor proteins that could be involved in spindle chirality. Among the candidate microtubule- associated proteins, we found that depletion of PRC1 or Kif18A/kinesin-8 leads to a decrease of left-handed twist, suggesting a role of these proteins in producing or maintaining spindle chirality. Similarly, depletion of the augmin subunits HAUS6 or HAUS8 resulted in either a loss of spindle chirality or in a change to right- handed twist possibly due to weakened microtubule bundles and disturbed geometry of microtubule nucleation. Finally, we show that spindle chirality is present in other organisms, specifically in the amoeba Naegleria gruberi. Although this organism has a spindle that is different from those in human somatic cells, i.e., it does not have centrosomes, microtubule bundles still adopt a helical form. Surprisingly, bundles in amoebas typically follow a right-handed helical path. In the future, it will be interesting to find out why spindle chirality is more pronounced around anaphase onset and what role it may have in chromosome segregation.

Izvorni jezik
Engleski

Znanstvena područja
Biologija

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