Automatic cell topology

Soap bubbles (and coins pushed together on a tabletop) shift around until they reach an optimal packing state. But epithelial cells are not free to shift, because they maintain a constant grip on their neighbors. Instead, their predictable packing state simply emerges as a consequence of a random cell division process, according to Matthew Gibson and Norbert Perrimon (Harvard Medical School, Boston, MA), and Ankit Patel and Radhika Nagpal (Harvard University, Cambridge, MA).

The Harvard group first confirmed that epithelial neighbors did not easily reassort their contacts, even during a cell division. They then constructed a model that predicted the probability that a daughter cell would have a particular number of sides after assigning a cell division plane randomly.

Where the division plane hit the side of a neighboring cell, that neighboring cell gained an...