An alternative hypothesis for the deformation of a cell nucleus

A cell’s nucleus is significantly more rigid than most of its other structures, which presents difficulties when the cell needs to dramatically alter its shape. This can happen, for instance, when the cell passes through a narrow opening or flattens itself against a surface.

In these situations, the nucleus deforms, but its rigid nature led many to presume this deformation was elastic. A perspective by Dickinson et al. examined this presumption and provided evidence of an alternative hypothesis.

“We found that removing the cellular forces on the nucleus does not cause the nucleus to relax its elongated or flattened shape,” said author Tanmay Lele. “These experiments led us to propose an entirely new model for how the nucleus behaves mechanically in the cell, and how the cell applies force to the nucleus to shape it.”

The team dissected the conventional elastic nucleus hypothesis, which assumes the nucleus is rigid and deformed by forces transmitted along the cell’s cytoskeleton. In the researchers’ alternative hypothesis, the nucleus is much softer and governed instead by viscous forces transmitted from the cytoplasm.

A key part of the new hypothesis is that the shell-like nuclear lamina stays at constant surface area when the nucleus changes shape. The lamina contains excess surface area compared to that of a sphere of the same volume, which allows the nucleus to flatten with little resistance. Also, the nuclear volume remains constant during shape changes.

The researchers hope their insights can be used to study diseased cells in humans, such as cancer or progeria.

“Our main interest right now is to devise molecular explanations for why cancer nuclei become so abnormal in shape,” said Lele.

Source: “Viscous shaping of the compliant cell nucleus,” by Richard B. Dickinson, Aditya Katiyar, Christina R. Dubell, and Tanmay P. Lele, APL Bioengineering (2021). The article can be accessed at https://doi.org/10.1063/5.0071652 .

This paper is part of the Mechanobiology of the Cell Nucleus Collection, learn more here .