A minimal model for correlated chromatin dynamics

The multiscale spatial structure of chromatin spans several decades from the nanometer scale to the micron scale. In addition to its nontrivial spatial structure, chromatin also exhibits nontrivial dynamics. For instance, correlated motion of chromatin on the length scale of microns over the time scale of tens of seconds has been observed. Correlations are diminished in the absence of ATP, suggesting that motor/enzymatic activity promotes chromatin collective dynamics. Therefore, we construct a minimal polymeric model to study the spatiotemporal properties of chromatin by simulating a Rouse chain with excluded volume interactions confined within a rigid, spherical shell that represents the lamina. We characterize the spatiotemporal properties of the chain in the presence of motor activity, crosslinking, and binding to the shell. These components model an active chromatin network with lamin-binding domains. We find correlated motion under several conditions, without the need for long-range forces. Notably, when chromatin is bound to the lamina, crosslinking and motor activity are required for strong correlations in chromatin motion. We also study the effects of a deformable lamina shell in order to study the coupling of correlated chromatin motion to nuclear shape.