In vivo DNA damage protection during cell migration across confining embryonic tissue environments.

Cells migrating through confined spaces can experience nuclear deformation, nuclear envelope damage and DNA lesions, but the physiological consequences of confinement in vivo remain unclear. Using the zebrafish neural crest as a model of developmental migration, we show that tissue confinement increases along the antero-posterior axis and scales with the extent of nuclear deformation. Genetic and mechanical disruption of surrounding tissues relieves confinement and restores nuclear morphology in vivo. Surprisingly, even under extreme deformation, neural crest cells exhibit nucleo-cytoplasmic leakage without nuclear envelope rupture or increased DNA damage. Instead, confinement is associated with reduced LaminB2 at the nuclear envelope. Functional perturbation of LaminB2 reveals that its depletion accelerates recovery from deformation, whereas sustained expression causes persistent nuclear distortion, identifying LaminB2 as a regulator of nuclear deformability. RNA-seq of confined trunk neural crest cells reveals broad upregulation of DNA repair pathways, suggesting that these embryonic stem-like cells are intrinsically resistant to confinement-induced mechanical stress.