stylistic:style_transfer, quality:correction
Actin retrograde flow

The assembly of nascent focal adhesions is highly dependent on the process of retrograde actin flow. This is the phenomenon in a migrating cell where actin filaments polymerize at the leading edge and flow back towards the cell body. This is the source of traction required for migration; the focal adhesion acts as a molecular clutch when it tethers to the ECM and impedes the retrograde movement of actin, thus generating the pulling (traction) force at the site of the adhesion that is necessary for the cell to move forward. This traction can be visualized with traction force microscopy. A common metaphor to explain actin retrograde flow is a large number of people being washed downriver, and as they do so, some of them hang on to rocks and branches along the bank to stop their downriver motion. Thus, a pulling force is generated onto the rock or branch that they are hanging on to. These forces are necessary for the successful assembly, growth, and maturation of focal adhesions.