Many cell types within the organism bind to their environment via specific adhesion molecules (integrins); these either stabilize cells that need to remain immobile, or serve as anchors when cell crawls through tissues.

In a recent study published in Nature, led by the group of Michael Sixt at IST Austria, the group of R. Voituriez (LJP, IBPS) proposed a new physical mechanism of cell migration that works in absence of any adhesion to the environment. Instead, the study, which combines physical modeling and cell biology experiments in engineered microfluidics set-ups, reveals that leukocytes can use the irregular topography of the environment to propel themselves.

The study concludes that adhesion-dependent and adhesion-independent migration are not mutually exclusive, but rather variants of the same principle of locomotion based on retrograde actin flows and thus can operate interchangeably or simultaneously. As adhesion-free migration is independent of the chemical composition of the environment, it renders cells completely autonomous in their locomotive behavior.

Illustration of a leukocyte migrating in absence of adhesions in a smooth or irregular topography (cytoplasm in grey, nucleus in blue, actin cytoskeleton in red). The retrograde actin flow is shown by the red arrows in the left panel: in both cases, fast retrograde flow is generated from the front of the cell to the back. However, the flow only generates the necessary force that pushes on the channel when there are bumps, and the cell can move forward (right panel, bottom). © Anne Reversat