The nuclear lamin network passively responds to both active or passive cell movement through confinements.

Physical models of cell motility rely mostly on cytoskeletal dynamical assembly. However, when cells move through the complex 3D environment of living tissues, they have to squeeze their nucleus that is stiffer than the rest of the cell. The lamin network, organised as a shell right underneath the nuclear membrane, contributes to the nuclear integrity and stiffness. Yet, its response during squeezed cell motility has never been fully characterised. As a result, up to now, the interpretations on the lamin response mechanism are mainly speculative. Here, we quantitatively map the lamin A/C distribution in both a microfluidic migration device and a microfluidic aspiration device. In the first case, the cell is actively involved in translocating the nucleus through the constriction, while in the second case, the cell behaves as a passive object that is pushed through the constriction by an external pressure. Using a quantitative description of the lamin shell response based on mass conservation arguments applied on the fluorescence signal of lamin, we show that in both cases of migration and aspiration, the response of the lamin network is passive. In this way, our results not only further elucidate the lamin response mechanism, but also allow to characterise that this deformation is passive even when the cell is actively migrating, thus paving the way to further investigate which active nuclear responses may occur when cells migrate in confinement.