Until now, neurobiologists have had little luck in finding the matchmakers of nerve cell connections, called synapses, in the brain. In today's issue of Cell, researchers report that a single protein can apparently trigger synapse formation between brain neurons isolated from mice and grown in culture. If the finding is borne out in living animals, it could provide fresh insights into how the brain is wired during embryonic development and might eventually provide new ways to enhance or at least maintain synapse formation in the brains of patients suffering from neurodegenerative diseases such as Parkinson's or Alzheimer's.