Regensburg 2022 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 13: Cytoskeleton

BP 13.5: Vortrag

Mittwoch, 7. September 2022, 10:45–11:00, H15

Length-dependent poleward flux of sister kinetochore fibres promotes chromosome alignment — •Domagoj Božan — Department of Physics, Faculty of Science, University of Zagreb, Bijenička cesta 32, 10000 Zagreb, Croatia

Chromosome alignment at the spindle equator promotes proper chromosome segregation and depends on pulling forces exerted at kinetochore fiber tips together with polar ejection forces. However, kinetochore fibers are also subjected to forces exerted by motor proteins that drive their poleward flux. Here we introduce a flux-driven centering model that relies on flux generated by forces within the overlaps of bridging and kinetochore fibers. This centering mechanism works so that the longer kinetochore fiber fluxes faster than the shorter one, moving the kinetochores towards the center. Our collaborators developed speckle microscopy in human spindles and confirmed the key prediction that kinetochore fiber flux is length-dependent. The experiments also confirmed that kinetochores are better centered when overlaps are shorter and the kinetochore fiber flux markedly slower than the bridging fiber flux. Furthermore, we extend the model to describe congression of chromosomes by considering dynamics of microtubule-kinetochore attachments and motor proteins at kinetochores and find that the length-dependent forces exerted by microtubules from farther pole can overcome the forces exerted by the greater number of microtubules from nearer pole. Thus, length-dependent sliding forces exerted by the bridging fiber onto kinetochore fibers promote chromosome congression and alignment.