A nucleus is not necessary for cell movement in culture, at least not for several hours. A large fragment of an OK epithelial cell that does not appear to have a nucleus, though it seems to contain a small number of mitochondria, can be observed migrating across the field of view throughout most of this digital video, which was produced from a time-lapse sequence of images captured over the course of more than ten hours. The active cell fragment changes shape, extends ruffling lamellipodia, and demonstrates contact inhibition similar to intact OK epithelial cells.

The cell fragment’s exploits come to a sudden end, however, when it attempts to divide. Though it successfully retracts its tiny surface extensions and assumes a roughly spherical geometry similar to that undertaken by many animal cells prior to mitosis, the fragment is not able to divide or to reassume its former active form. The small segment of material dies and, with no adhesions to bind it to the substratum, begins to be carried off by currents in the culture medium.

A second migrating segment of a cell enters the lower part of the field of view about midway through the time-lapse sequence. Unlike the previously discussed fragment, it is still alive and traveling across the chamber surface at the end of the video. The activity of the nucleus-less cell pieces is a testament to the fact that it is the cytoskeleton, not organelles, that chiefly control cell migration. More specifically, a meshwork of actin filaments located directly beneath the plasma membrane is responsible for lamellipodial activity and most other cell surface dynamics.