Live-cell imaging under centrifugation characterized the cellular force for nuclear centration in the Caenorhabditis elegans embryo.

Makoto Goda, Michael Shribak, Zenki Ikeda, Naobumi Okada, Tomomi Tani, Gohta Goshima, Rudolf Oldenbourg, Akatsuki Kimura

Proceedings of the National Academy of Sciences (PNAS) (2024) 121 (43), e2402759121 DOI:10.1073/pnas.2402759121

Press release (In Japanese only)

Genomic DNA containing genetic information is stored in the cell nucleus. The nucleus is often located near the center of the cell. This means that there is a force inside the cell that moves and maintains the nucleus at the center. Measuring the amount of force is a challenging task. In this study, the researchers succeeded in measuring the force that maintains the cell nucleus in the center by applying centrifugal force to the cell using a special microscope called centrifuge polarizing microscope (CPM). CPM enables researchers to observe cells while rotating at a high speed. Researchers found that when a cell is rotated at a high speed, the cell nucleus is displaced from the center of the cell. The greater the centrifugal force, the greater the displacement of the nucleus from the center of the cell. Another special microscope, called an orientation-independent differential interference contrast (OI-DIC) microscope, revealed the mass density of the cell nucleus and thus enabled the researcher to calculate the centrifugal force acting on the nucleus. From this relationship between force and displacement, the researchers succeeded in quantifying the tiny force generated inside the cell to keep the nucleus centered. Cells are crowded with high concentrations of large molecules such as proteins. It has been a mystery how a large structure, such as the cell nucleus, can move inside crowded cells. This research unraveled part of this mystery using CPM and OI-DIC microscopes through the international collaboration.