In findings published in today's edition of Neuron, the 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 we see to visual centers in the brain.
Neurobiologists had long sought to answer how neural maps are established.
"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," said Dr. Dennis O'Leary, professor of molecular neurobiology at the Salk Institute and the study's senior author. "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 generated by our colleagues at UT Southwestern."
Earlier work by O'Leary had implicated the B-class Ephs and ephrins, leading to collaboration with Dr. Mark Henkemeyer, assistant professor in the Center for Developmental Biology at UT Southwestern and a co-author of the study. Henkemeyer, whose work focuses on the role of Ephs and ephrins, particularly B-class, in a variety of developmental processes, provided mice that carried mutations in the genes for the EphB receptors.
Today's published findings don't have immediate clinical application, Henkemeyer said, 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.