PhD defence: The final step of cell division - Molecular mechanisms of abscission regulation in mouse embryonic stem cells

PLEASE NOTE: The candidate gives a layman's talk, therefore the livestream will start fifteen minutes earlier.

The life of a multicellular organism starts as a single fertilized egg (a zygote) that must divide many times to build a functioning body. As these cells multiply, they make crucial fate decisions to specialize into different tissue types. While the original zygote can become absolutely any cell in the body or placenta, later stem cells become more restricted in what they can turn into. Interestingly, these major 'life choices' for a cell are deeply tied to the physical process of cell division.

This research specifically looks at mouse embryonic stem cells to understand why they take an unusually long time to complete the very final step of cell division, called abscission, the moment two new cells physically snip apart.

Following an introductory overview of cell division and stem cell biology, the thesis explores how delays in this final separation happen across nature. While cancer cells might delay separation due to genetic errors, stem cells do it as part of their normal physiology. To study this closely, we first developed a specialized 2D and 3D imaging protocol to get a clear look at these microscopic structures.

The core findings of this thesis reveal that a master regulator protein called Aurora B kinase, alongside stable microtubules, acts as a brake system that holds the cells together longer. Furthermore, this delay is controlled by Wnt signaling, a major cell communication pathway. When Wnt signaling is active, it keeps Aurora B levels high and stabilizes the cell's skeleton, purposefully slowing down separation to help embryonic stem cells maintain their unique, unspecialized state.