Making streams

摘要

Cells of the slime mould Dictyostelium discoideum can move in a kind of close-order drill. New evidence suggests that they do this by secreting a chemical attractant specifically from their rear, luring the cells that follow. In 1944, the microbiologist Ernest Runyon put amoebae of the then little studied slime mould Dictyostelium discoideum on both sides of a piece of porous cellophane. Over the next few hours, the amoebae on one side started to gather at a central point, moving at first individually and then, tail to head, in streams. Astonishingly, so did the amoebae on the other side of the cellophane, forming mirror-image streams. Runyon presumed that this was due to a molecule, secreted through the cellophane, that attracted cells on the other side. This turned out to be the first observation that a diffusible attractant molecule is involved in guiding aggregation. It would be more than two decades before John Bonner and his colleagues discovered that this molecule was cyclic AMP, secreted by the migrating amoebae. Carole Parent and colleagues have continued with this line of research, and now show in Cell that the D. discoideum enzyme that produces cAMP is located specifically at the rear of the migrating cells ― perhaps explaining how they move in a stream.