Staying connected

Learning spurs axons in the brain to grow and connect with other neurons. However, scientists know little about what maintains these connections, which sometimes last a lifetime. A new study reveals that a protein known as p190 RhoGAP stabilizes the axon. The authors report that p190 works by stifling a built-in “retraction pathway” that causes axons to shrivel.

Liqun Luo of Stanford University, Palo Alto, CA, and colleagues investigated p190's function in the Drosophila mushroom body, the part of the brain responsible for olfactory learning and memory. When they inhibited p190 in neurons, the axon branches shrank or even disappeared. They got the same results by activating the RhoA pathway, which p190 normally blocks. “The idea that in mature neurons there is a pathway whose job is to destroy the axon...