From nuclear pores to kinetochores: non-canonical roles of nucleoporins in mitosis

The human body is comprised of trillions of cells that all originate from a single cell by a process of division. Before a cell divides by mitosis, it duplicates its DNA i.e. doubles the number of chromosomes it carries. The two duplicates of a chromosome, known as sister chromatids, are held together. A protein complex known as the kinetochore (KT) fully assembles onto chromosomes in early mitosis and is then used to form attachments to spindle microtubules (MTs). Spindle MTs pull the sister chromatids to opposite poles of the cell before the cell is split into two daughter cells, each carrying one full set of chromosomes. If problems arise in chromosome segregation (e.g. both sister chromatids are pulled to the same cell pole), the daughter cells might end up with the wrong number of chromosomes. This state is known as aneuploidy. Aneuploidy is the cause of many genetic conditions, e.g. Down syndrome, but is also the leading cause of miscarriages, and can lead to cancer or infertility (Li & Zhu, 2022). One outstanding question in mitosis regards the role of nucleoporins in mitosis. Nucleoporins are the components of nuclear pore complexes (NPCs), macromolecular protein assemblies that facilitate transport across the nuclear envelope (NE) in interphase. Loïodice et al. (2004) reported that upon NE breakdown at the start of mitosis, the NPC subcomplex known as Y-complex relocates to KTs. Its recruitment mechanism and role at the KT remain undefined.

By combining microscopy across a range of perturbation experiments of fluorescently marked RPE1 cells with detection and tracking of individual KTs, this project aims to quantitatively characterise the (un)loading of the Y-complex at mitotic KTs, investigate its recruitment mechanism and define its mitotic function. By broadening our understanding of chromosome segregation, we hope to directly contribute to the knowledge of the numerous human diseases caused by the failure of this process.