A team of scientists has uncovered details explaining how neurons, which are produced in only a few regions of the brain, push through existing brain tissue to their final destinations (Neuron 2010, 67, 213). In adult mammals, neurons generated in the subventricular zone migrate to the olfactory bulb, a journey ranging from millimeters to centimeters, depending on the species, according to Kazunobu Sawamoto of Japan’s Nagoya City University Graduate School of Medical Sciences and coworkers. Prior research showed that these immature neurons migrate through tunnels made of astrocytes, a type of glial cell. In their work with mice, Sawamoto’s team found that the neurons control the formation and organization of these tunnels by secreting the protein Slit1, which repels astrocytes by binding to Robo receptors expressed by the astrocytes. Without Slit1, outgrowths from the astrocytes clog the tunnels and neuronal migration slows significantly. In a commentary about the work, Eva S. Anton and colleagues at the University of North Carolina School of Medicine, Chapel Hill, note that the ability to modify the path taken by immature neural cells would be useful in regenerative treatments for brain injuries.