Spatial organization of chromosomes leads to heterogeneous chromatin motion and drives the liquid- or gel-like behavior of chromatin

Chromosome organization and dynamics are involved in the regulation of many fundamental processes such as gene transcription and DNA repair. Experiments unveiled that inside cell nuclei chromatin motion is highly heterogeneous ranging from a liquid-like, mobile state to a gel-like, rigid state. Using polymer modeling, we investigated how these different physical states and dynamical heterogeneities may emerge from the same structural mechanisms. We found that the formation of topologically-associating domains (TADs) is a key driver of chromatin motion heterogeneity. In particular, we demonstrated that the local degree of compaction of the TAD regulates the transition from a weakly compact, fluid state of chromatin to a more compact, gel state exhibiting anomalous diffusion and coherent motion. Our work provides a comprehensive study of chromosome dynamics and offers a unified view of chromatin motion allowing to interpret the wide variety of dynamical behaviors observed experimentally across different biological conditions.