Protein helps the brain connect

In the brain, as in politics and business, connections are key. When nerve cells chat, they do so via specialized links called synapses, where one nerve cell releases chemical signals to regulate the activity of its partner.

Just how do those lines of communications form? In the June 9 Cell, researchers report that a pair of proteins known as neuroligins help answer that question, which has long puzzled neuroscientists. While researchers have shown that a protein called agrin controls the creation of similar synapses between nerve cells and muscles (SN: 5/25/96, p. 327), they’ve found little evidence that agrin plays such a role in the brain.

Neuroligins may resolve this riddle, according to a research group headed by Tito Serafini of the University of California, Berkeley. The proteins normally sit on the surface of nerve cells, but in test-tube experiments, Serafini’s team genetically engineered kidney cells to make neuroligins. The manipulated cells, unlike normal kidney cells, induced nerve cells they touched to assemble structures characteristic of one side of a synapse. These data, as well as results from other experiments, persuade Serafini and his colleagues that neuroligins are the key to inducing brain synapses.

The case is far from settled, however. Mice engineered to lack one of the two neuroligins seem healthy and have no obvious brain defects. Perhaps the other neuroligin can compensate for the deficit, the researchers suggest.