The final event in cell division, termed cytokinetic abscission, promotes the physical separation of the daughter cells by severing of the midbody, a thin membranous bridge that connects the dividing cells. This final cut is facilitated by the endosomal sorting complex required for transport (ESCRT) machinery, a membrane remodelling machinery. ESCRT proteins form four multiprotein complexes termed ESCRT-0, ESCRT-I, ESCRT-II, and ESCRT-III. Current models propose that ESCRT-III subunits form high order filaments that draw together the opposing membranes at the midbody to facilitate abscission. This filament growth requires the rapid turnover of ESCRT-III subunits by VPS4.
Despite this progress, how functional ESCRT filaments are formed remains poorly understood. We have now identified UMAD1 as a new ESCRT-I subunit that regulates the dynamic exchange of ESCRT-III subunits at the midbody. This project will explore how UMAD1 shapes ESCRT-III filaments during abscission. Imaging ESCRT-III filaments in cells require high resolution, but current super-resolution approaches are limited as these can achieve resolutions of 15-20 nm. Recent breakthrough techniques exploit orthogonal DNA barcodes to achieve Ångström-resolution (PMID: 37225882). This project will take advantage of this pioneering technique to image ESCRT-III filaments in cells at Ångström-resolution for the first time.
The student will:
1) Use basic molecular biology and cell biology techniques (including DNA manipulation, siRNA depletion of target genes or gene editing) to generate bespoke imaging tools, and express these in live cells to perform microscopy studies under physiological conditions (Year 1).
2) Resolve the spatial relationship between ESCRT-III, UMAD1 and other ESCRT factors at sub-nanoscale resolution using advanced live-cell microscopy. (Year 2)
3) Learn quantitative imaging approaches to study the role of UMAD1 on the polymeric state of ESCRT-III. (Year 3)
This multidisciplinary project will reveal basic principles in the formation of functional ESCRT-III polymers, and how these facilitate the last step in cell division.