Revealing the structure and mechanism of mitotic chromosome folding inside the cell

ongoing

Mitosis is a fundamental biological process every cell undergoes at least once. It requires a dynamic and dramatic restructuring of the genome from extended interphase chromatin to compact individual mitotic chromosomes capable of faithful segregation. Altered nucleosome interactions, phase separation and loop extrusion have all been proposed to play important roles in shaping mitotic chromosomes. However, what the internal architecture of single mitotic chromosomes is, and how this architecture is established in space and time by different forces inside the cell remains unclear. This lack of knowledge precludes a comprehensive mechanistic understanding of mitotic chromosome folding and unfolding. This project aims to resolve the folding principles of chromosomes during mitotic compaction and decompaction in situ, in single human cells. To achieve this, we will combine newly developed nanoscale DNA tracing technology with quantitative single protein imaging approaches to achieve a systematic structural analysis of mitotic chromosome folding throughout mitosis. We will investigate when and where which structural features are first established, and then use targeted, acute perturbations to dissect which regulators are required to form and maintain them. The resulting data will provide an in situ structure-based model to explain the essential function of the genome in mitosis and will allow us to understand the spatio-temporal coordination of the underlying molecular and physical mechanisms. Overall, the proposed project will provide a new framework for understanding the physiological and pathological roles of mitotic chromosome restructuring during cell division.