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bioRxiv · 10.1101/2021.11.13.468347

Three-dimensional structure of the kinetochore-fibers in human mitotic spindles

Kiewisz, R.·Fabig, G.·Conway, W.·Needleman, D.·Muller-Reichert, T.
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Abstract

During cell division, kinetochore microtubules (KMTs) provide a physical linkage between the chromosomes and the rest of the spindle. KMTs in mammalian cells are organized into bundles, so-called kinetochore-fibers (k-fibers), but the ultrastructure of these fibers is currently not well characterized. Here we show by large-scale electron tomography that each k-fiber in HeLa cells in metaphase is composed of approximately nine KMTs, only half of which reach the spindle pole. Our comprehensive reconstructions allowed us to analyze the three-dimensional (3D) morphology of k-fibers and their surrounding MTs in detail. We found that k-fibers exhibit remarkable variation in circumference and KMT density along their length, with the pole-proximal side showing a broadening. Extending our structural analysis then to other MTs in the spindle, we further observed that the association of KMTs with non-KMTs predominantly occurs in the spindle pole regions. Our 3D reconstructions have implications for KMT growth and k-fiber self-organization models as covered in a parallel publication applying complementary live-cell imaging in combination with biophysical modeling (Conway et al., 2022). Finally, we also introduce a new visualization tool allowing an interactive display of our 3D spindle data that will serve as a resource for further structural studies on mitosis in human cells.

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Kiewisz, R., Fabig, G., Conway, W., Needleman, D., Muller-Reichert, T.. 2021-11-13. Three-dimensional structure of the kinetochore-fibers in human mitotic spindles. https://doi.org/10.1101/2021.11.13.468347

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