Science
By Russell Hodge
Decision at the crossroads
Compared to the human nervous system, the circuitry of the most advanced computer looks simple – even though nerve cells have to wire themselves up without the help of designers or engineers. As an embryo develops, each neuron engages in a dialogue with molecules on neighboring cells. These encounters tell its axon – a long, trunk-like transmitter – where to go, when to fork into branches, and which nerves it should make contact with. Scientists have identified many of the signals that help the axon find precise target cells, often in distant regions of the body. But little is known about how they fork, which allows one cell to broadcast information to many others. In the Sept. 29 issue of PNAS, Fritz Rathjen's laboratory at the MDC reports the discovery of a new protein signal that triggers the axons of some nerve cells to split.