Fig. 4.

Collective migration and AJs remodelling can be triggered by environmental mechanics.

A. The schematic shows how the mechanical interaction among migratory cell clusters and their surrounding tissues triggers AJs modification via cadherin switch. In this particular example, the tissue which is underneath a migratory cell population became stiffer as the developmental time progress. This stiffening is sensed by the migratory cell population which initiate an EMT-like program to modify their AJs in a switch from epithelial to mesenchymal type of cadherin, hence initiating fluid-like collective migration. This stiffening also provides an appropriate substrate for collective migration, where cells can efficiently polarise and form lamellipodia, required for their adherent migration. This mechanism was recently shown to trigger and support the collective migration of the Xenopus cephalic neural crest. This type of interactions may also operate in other systems where migratory substrate is observed. Stiffening in vivo has been shown to be mediated by, among other factors, actomyosin contractility, cell density, and ECM accumulation. Examples showing the elasticity ranges operating in the mechanical regulation of cadherins both, in vivo [165] and in vitro [228] are also shown.