Many kinds of animal cells form focal adhesions with suitable culture media. Each of the sites of linkage involves actin filaments bundled into a stress fiber, which anchor the cell to the substratum via specialized proteins. Focal adhesions function in cell locomotion, acting similar to microscopic feet that are fixed in place as the cell travels over them, but are pulled up by the cell as they become increasingly distant from the cell’s leading margin. Sometimes, however, the adhesions are not detached from the substratum quickly enough and a cell is forced to sever small fragments of material in order to continue on its migratory path, as demonstrated by several of the OK cells featured in this digital video.

Focal adhesions also function in a communicatory capacity. The sites of linkage are capable of receiving signals from the environment and sending them to the main process of a cell. For example, when a cell affixes to a suitable surface and focal adhesions are produced, signals are sent to the cell that indicate that it is ready to grow or undergo differentiation. Dividing animal cells generally retract all of their surface extensions and, therefore, usually do not form focal adhesions. When daughter cells are successfully produced and begin to settle on the substratum, they typically reform the adhesions.

Cells unable to make contact with the substratum appear to have difficulty completing cell division. Notably, several different OK epithelial cells in the crowded field of view initiate the process, as evidenced by the spherical geometries they assume, but are unable to conclude it. Instead of producing daughter cells, some of the cells appear to be frozen in their spherical shape atop other OK cells. One of the cells attempting to divide that seems to be trapped away from the culture medium contorts in a frenzied manner as if enjoying a bacchanalian dance.