Fluid mechanics of a nucleus squeezing through a narrow constriction

Fluid mechanics plays a central role in the deformation and passage of blood cells and vesicles through narrow constrictions, including splenic slits, pulmonary capillaries, endothelial gaps, and microfluidic channels (Peng, Viallat, and Young, 2026, Annual Review of Fluid Mechanics). Here, we demonstrate that similar squeezing hydrodynamics also governs the deformation of the cell nucleus as it navigates constricted regions near the cell periphery. Building on the stoichiometric model introduced by Young et al. (2025, Physical Review Research), we investigate the hydrodynamics of the centrosome–pronucleus (CP) complex in a viscous cytoplasmic environment. Framed as a fluid–structure interaction problem, we employ a boundary integral formulation to simulate key dynamics of the CP complex, including centrosome separation around the nucleus, centering of the pronucleus, and nuclear deformation induced by centrosomal pulling forces. We extend the classical Helfrich membrane model to incorporate active force generation by nucleus-bound motors interacting with astral microtubules, and explore how nuclear positioning and deformation are modulated by cell shape and confinement geometry.