Dresden 2020 – scientific programme

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BP: Fachverband Biologische Physik

BP 20: Poster VIII

BP 20.5: Poster

Tuesday, March 17, 2020, 14:00–16:00, P2/4OG

The relative densities of cell cytoplasm, nucleoplasm, and nucleoli are robustly conserved during cell cycle and drug perturbations — •Kyoohyun Kim and Jochen Guck — Max Planck Institute for the Science of Light, 91058 Erlangen, Germany

The cell nucleus is an essential cellular compartment as the location of gene expression and DNA replication. While the large amount of its chromatin confined in the finite nuclear space could install the picture of a particularly dense organelle surrounded by less dense cytoplasm, recent studies have begun to report the opposite. However, the generality of this observation has so far not been tested. Here, we used combined optical diffraction tomography (ODT) and epi-fluorescence microscopy to systematically quantify the mass densities of cytoplasm, nucleoplasm, and nucleoli of HeLa-FUCCI and RPE-FUCCI cells being challenged by various perturbations. We found that the nucleoplasm maintains a lower mass density than cytoplasm, but lower than nucleoli, during cell cycle progression by scaling its volume to match the increase of dry mass during cell growth. Moreover, actin and microtubule depolymerization and changing chromatin condensation altered volume, shape and dry mass of the various cellular compartments, while the relative distribution of mass densities was still robustly conserved. Our findings suggest that cells regulate relative mass densities across membrane-bound and membrane-less compartments, likely by different as of yet unknown mechanisms. This surprising robustness of mass densities contributes to the increasing importance of physical properties of biological cells in current biological research.