Biologists gain new insights into brain circuit wiring

Neurobiologists at University of California at San Diego have discovered new ways by which nerves are guided to grow in highly directed ways to wire the brain during embryonic development.

UC San Diego biologists discovered how growth cones at the tips of growing nerves are guided to wire the developing brain. Credit: Yimin Zou,

Their finding, detailed in a paper in the February 15 issue of the journal Developmental Cell, provides a critical piece of understanding to the longstanding puzzle of how the human brain wires itself into the complex networks that underlie our behavior.

The discovery concerns the movements of a highly sensitive and motile structure at the tips of growing nerves called a growth cone. For more than a century, biologists have known that growth cones find their targets by detecting chemical cues in the developing nervous system.

They do that by responding to gradients of chemical concentration and steering nerve cells either up or down the gradient to eventually find the right targets to make the proper nerve connections that then establish neuronal networks.

While many of these chemical guidance cues have been identified over the past decade, scientists still don't fully understand how the growth cone picks up small concentration differences in the developing embryo or how guidance cues enter the growth cone to regulate the cellular machinery to turn growth cones in one direction or another.

Yimin Zou, an associate professor of neurobiology at UC San Diego, and his colleagues had previously shown that a family of proteins known as ''Wnt morphogens'' provide the directional cues for the wiring of circuits in many parts of the developing brain.