Active Polymer Models: Unravelling the 3D Organization and Dynamics of Chromosomes

Abstract

Genome organization refers to how genetic material (DNA) is arranged, packaged, and regulated inside a cell. It operates at multiple hierarchical levels - nucleotide sequence to 3D spatial arrangement in the nucleus, and is crucial for gene regulation, replication, and evolution. Recent studies on chromosomal dynamics reveal that chromatin behaves neither like a passive elastic fiber nor a perfectly orderly folded structure, but as an active, viscoelastic polymer driven by both thermal fluctuations and energy-consuming (ATP-dependent) processes [3]. Polymer based models of chromosomal loci show how stress propagates along the DNA backbone, generating correlated motion across genomic distances and explaining sub diffusive behaviour characteristic of bacterial and eukaryotic nuclei [1,3]. Complementary approaches using Hi-C derived microrheology translate static contact maps into dynamic mechanical spectra, revealing rigid TAD (Topologically Associating Domain) boundaries and liquid-like mixing within domains essentially turning chromosomes into rheological landscapes [2]. At larger scales, fractal folding and loop extrusion further build genome architecture, enabling local insulation while permitting global reconfiguration during cell differentiation or signalling. These genome studies resonate strikingly with advances in active-polymer physics [1], where simulations of driven monomers and hydrodynamic coupling uncover activity-induced phenomena like stiffening, collapse, and enhanced transport. Much like chromatin, active chains exhibit tuneable persistence, long-range correlations, and dynamic restructuring in response to localized forces. Together, these works outline a unifying view: chromosomes behave as active polymers embedded in an active bath, where motor proteins, enzymatic remodelling, and hydrodynamics collectively coordinate 3D genome organization. Understanding this complex interplay opens the door to truly predictive models that directly link molecular activity to emergent nuclear architecture an exciting and crucial border for both biologists and physicists.