Universality of the network-dynamics of the cell nucleus at high frequencies.

The interior of the cell nucleus is comparable to a solid network bathed in an interstitial fluid. From the extrapolation of low frequency data, it is expected that such network should dictate the response of the nucleus to mechanical stress at high frequencies, described by unique elastic moduli. However, none of the existing techniques that can probe the mechanical properties of cells can exceed the kHz range, and the mechanics of the nuclear network remain poorly understood. We use laser-generated acoustic waves to probe remotely the stiffness and viscosity of nuclei in single cells in the previously unexplored GHz range with a ∼100 nm axial resolution. The probing of cells at contrasted differentiation stages, ranging from stem cells to mature cells originating from different tissues, demonstrates that the mechanical properties of the nuclear network are common across various cell types. This points to an asymptotically increasing influence of a solid meshwork of connected chromatin fibers.