Remodelling of the Endomembrane System During Mitotic Exit

During division, eukaryotic cells perform a dramatic reorganisation of their cytoskeleton and their internal membranes. Whilst we know much about how the genome is separated, our understanding of how the cell reorganises, partitions and separates its organelles remains poorly understood. During division, the nuclear envelope (NE) is dismantled and regresses into the endoplasmic reticulum (ER), a major organelle occupying over a third of the cellular volume. This hybrid organelle is distributed as a continuous membrane system between daughter cells as cells leave division, but how this membrane is actually separated is unknown. This hybrid membrane also envelops the separating chromatin discs and a machinery called ESCRT-III assembles transiently at the reforming NE to seal gaps in this membrane. We will use quantitative proteomics and structural mass spectrometry to identify control mechanisms allowing spatiotemporally controlled assembly of ESCRT-III at the reforming NE. We will use whole-cell volumetric EM correlated with live-cell imaging measurements of ER-connectivity to understand how the ER is physically separated during mitotic exit. We will use these approaches to examine how ER-separation and NE-reformation are coordinated and integrated with the inheritance of other major organelles, giving us new insight into the cellular reorganisation occurring as cells complete division.