A reaction diffusion system for the morphological properties of inclusion bodies in the life-cycle of the Ebola virus.

Phase separation is central to a plethora of biological processes. In the context of viral reproduction, many viruses assemble their capsids within biomolecular condensates, liquid-like phase-separated droplets which are called inclusion bodies in the case of the Ebola virus. The Ebola virus nucleocapsid is a rod-like capsid. Recent cryo tomography results suggest that assembly of the nucleocapsid within the inclusion body generates liquid crystalline nematic order. This transition induces morphological changes in the inclusion body – surface deformations and elongation, eventually leading to dramatic dissolution. Evidence suggests that these changes help Ebola spread within its host organism. In this study, we present a continuum field-theoretic approach to model the dynamic, nonequilibrium interplay among assembly, liquid-liquid phase separation, and liquid crystalline order. Our framework describes a reaction-diffusion system where two precursor fields interact to produce a third field, which drives nematic order within a condensate. The liquid crystalline degree of freedom couples to the condensate's interface, inducing alignment and hydrodynamic interactions as the liquid crystal evolves. This interaction drives morphological transformations of the condensate, yielding complex patterns reminiscent of the morphological changes observed in viral inclusion bodies during the Ebola virus lifecycle. Importantly, our framework also improves the theory for equilibrium nematic liquid crystals, and reproduces experimentally observed spindle-like geometries of nematic tactoids. Our results elucidate an essential step in the Ebola virus lifecycle, and insights into the coupling between chemical reactions and structural organization in dynamic cellular environments.