Neurons shouldn’t always stick together

The cerebral cortex is organized into contiguous cellular columns—the sort of ordering a dozen pencils takes on if tightly wrapped with a rubber band. These columns form during embryonic development, when neurons shimmy up spoke-like radial glial cells until they reach their proper location in the cortex.

However, some neurons in each column shift away from the glial spoke to form interconnections with neurons in neighboring columns, ensuring a proper neuronal “blend” to perform specific functions. Scientists believe that disturbances in this process may cause psychiatric disorders.

In the September 24 issue of Nature, a group led by Pasko Rakic, M.D., Ph.D., the Dorys McConnell Duberg Professor of Neurobiology, reports that in mice lacking genes for the receptor EphA, neurons formed tight, even single-file columns, while overexpression of EphA caused too much lateral drift (green in image). In normal mice, appropriate numbers of neurons drifted to neighboring columns to perform their assigned duties.

“This so-far unrecognized mechanism … seems to be essential for the proper intermixing of neuronal types in the cortical columns,” the authors write.