Dynamic nuclear structure emerges from chromatin crosslinks and motors

TL;DR

This paper presents a minimal physical model showing that chromatin dynamics and nuclear shape fluctuations result from the interplay of motor activity and crosslinking within the nucleus.

Contribution

It introduces a new active, crosslinked polymer model that explains correlated chromosome motions and nuclear shape changes based on motor activity and crosslinks.

Findings

Correlated chromosome motions require both motors and crosslinks.

Contractile motors increase chromosome density fluctuations.

Nuclear shape fluctuations depend on motor strength, crosslinking, and lamina binding.

Abstract

The cell nucleus houses the chromosomes, which are linked to a soft shell of lamin filaments. Experiments indicate that correlated chromosome dynamics and nuclear shape fluctuations arise from motor activity. To identify the physical mechanisms, we develop a model of an active, crosslinked Rouse chain bound to a polymeric shell. System-sized correlated motions occur but require both motor activity {\it and} crosslinks. Contractile motors, in particular, enhance chromosome dynamics by driving anomalous density fluctuations. Nuclear shape fluctuations depend on motor strength, crosslinking, and chromosome-lamina binding. Therefore, complex chromatin dynamics and nuclear shape emerge from a minimal, active chromosome-lamina system.