Confinement and low adhesion induce fast amoeboid migration of slow mesenchymal cells

The mesenchymal-amoeboid transition (MAT) was proposed as a mechanism for cancer cells to adapt their migration mode to their environment. While the molecular pathways involved in this transition are well documented, the role of the microenvironment in the MAT is still poorly understood. Here, we investigated how confinement and adhesion affect this transition. We report that, in the absence of focal adhesions and under conditions of confinement, mesenchymal cells can spontaneously switch to a fast amoeboid migration phenotype. We identified two main types of fast migration--one involving a local protrusion and a second involving a myosin-II-dependent mechanical instability of the cell cortex that leads to a global cortical flow. Interestingly, transformed cells are more prone to adopt this fast migration mode. Finally, we propose a generic model that explains migration transitions and predicts a phase diagram of migration phenotypes based on three main control parameters: confinement, adhesion, and contractility.

Regulation of dendritic cell migration by CD74, the MHC class II-associated invariant chain

Dendritic cells (DCs) sample peripheral tissues of the body in search of antigens to present to T cells. This requires two processes, antigen processing and cell motility, originally thought to occur independently. We found that the major histocompatibility complex II-associated invariant chain (Ii or CD74), a known regulator of antigen processing, negatively regulates DC motility in vivo. By using microfabricated channels to mimic the confined environment of peripheral tissues, we found that wild-type DCs alternate between high and low motility, whereas Ii-deficient cells moved in a faster and more uniform manner. The regulation of cell motility by Ii depended on the actin-based motor protein myosin II. Coupling antigen processing and cell motility may enable DCs to more efficiently detect and process antigens within a defined space.