Proteins control wiring of eye to the brain - Optics - nervous system research - Brief Article

USA Today (Society for the Advancement of Education), Oct, 2002

A crucial piece of the puzzle of how the eye becomes wired to the brain has been revealed by scientists at the Salk Institute for Biological Studies, La Jolla, Calif., and the University of Texas Southwestern Medical Center at Dallas. Researchers report that a certain class of Eph receptors and ephrin ligands--proteins that cause cells to either repel or attract each other--control how nerve connections from the developing eye form maps that present what people see to visual centers in the brain.

"We knew that a certain class of Ephs, the A-class Ephs, were important in mapping the axons on the left-right, or horizontal, axis of the eye into the brain," explains Dennis O'Leary, professor of molecular neurobiology, Salk Institute, the senior author of the study. "Our new research now identifies how optic axons map the top-bottom, or vertical, axis of the retina into the brain and also defines the biochemical signals used to control this mapping through the analyses of a variety of important mutant mice."

The findings do not have immediate clinical application, but are another important step in understanding how the human nervous system develops and in particular how the retinal axons of the eye form their connections with the brain.

During eye development, axons grow from different parts of the retina and out the back of the eye, forming the optic nerve. The optic axons grow from four distinct parts of the retina--left-right and top-bottom--and terminate in corresponding specific parts of visual centers in the brain. The wiring scheme allows the brain properly to process the horizontal and vertical dimensions that compose images that are projected onto the retina.

"In my lab, we're working to understand from a basic molecular level how the nervous system becomes wired," indicates Mark Henkemeyer, an assistant professor in the Center for Developmental Biology at UT Southwestern. "If someone gave you a broken Maserati and said, `Fix it,' you'd probably like to have a manual that shows how it was put together in the first place. We're trying to develop that manual for the wiring of the nervous system."