Making a visual map: mechanisms and molecules.
Visual system development utilizes global and local cues to assemble a topographic map of the visual world, arranging synaptic connections into columns and layers. Recent genetic studies have provided new insights into the mechanisms that underlie these processes. In flies, a precise temporal sequence of neural differentiation provides a global organizing cue; in vertebrates, gradients of ephrin-mediated signals, acting with neurotrophin co-receptors and neural activity, play crucial roles. In flies and mice, neural processes tile into precise arrays through homotypic, repulsive interactions, autocrine signals, and cell-intrinsic mechanisms. Laminar targeting specificity is achieved through temporally regulated cell-cell adhesion, as well as combinatorial expression of specific adhesion molecules. Future studies will define the interactions between these global and local cues.
Clandinin
Thomas R
TR
Department of Neurobiology, Fairchild D200, 299W. Campus Drive, Stanford University, Stanford, CA 94305, United States. trc@stanford.edu
Feldheim
David A
DA
D000818:Animals; D001921:Brain / Q000254:growth & development / Q000502:physiology; D009474:Neurons / Q000502:physiology; D012160:Retina / Q000254:growth & development / Q000502:physiology; D013997:Time Factors; D014795:Visual Pathways / Q000254:growth & development* / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology