Noninvasive Measurement of Interphase Chromatin Rheology <i>In Vivo</i>

Material properties of the genome are critical for its proper function and organization inside
the cell nucleus. Chromatin, the functional form of DNA in cells, consists of DNA and
associated proteins, forming long linear fibers in the interphase nucleus of eukaryotic cells.
Traditionally, rheology of cellular components has been studied by tracking microparticles
injected inside the cell [1]. Recently, we developed an injection-free noninvasive approach to
study chromatin rheology using nuclear organelles as native probes [2]. Here, we show an
alternative noninvasive experimental strategy using intrinsic dynamics to measure chromatin
rheology across a large range of timescales, and elucidate the viscoelastic nature of
chromatin in live cells. The measured rheology is captured by a surprisingly simple model
whose few parameters have clear physical interpretations for this complex active material.

1. Wirtz, Annu. Rev. Biophys, 2009
2. Caragine et. al. Phys. Rev. Lett., 2018