title: Complementary gradients in expression and binding of ELF-1 and Mek4 in development of the topographic retinotectal projection map.
abstract: Topographic maps with a defined spatial ordering of neuronal connections are a key feature of brain organization. Such maps are believed to develop in response to complementary position-specific labels in presynaptic and postsynaptic fields. However, the complementary labeling molecules are not known. In the well-studied visual map of retinal axons projecting to the tectum, the labels are hypothesized to be in gradients, without needing large numbers of cell-specific molecules. We recently cloned ELF-1 as a ligand for Eph family receptors. Here, RNA hybridization shows matching expression gradients for ELF-1 in the tectum and its receptor Mek4 in the retina. Binding activity detected with alkaline phosphatase fusions of ELF-1 and Mek4 also reveals gradients and provides direct evidence for molecular complementarity of gradients in reciprocal fields. ELF-1 and Mek4 may therefore play roles in retinotectal development and have properties predicted of topographic mapping labels.
authors.affiliation: Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: H J
authors.initials: HJ
authors.lastname: Cheng
authors.forename: M
authors.initials: M
authors.lastname: Nakamoto
authors.forename: A D
authors.initials: AD
authors.lastname: Bergemann
authors.forename: J G
authors.initials: JG
authors.lastname: Flanagan
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001931:Brain Mapping; D002645:Chickens; D036383:Ephrin-A2; D051379:Mice; D008969:Molecular Sequence Data; D011506:Proteins / Q000302:isolation & purification / Q000502:physiology*; D012165:Retinal Ganglion Cells / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013477:Superior Colliculi / Q000196:embryology / Q000502:physiology*
chemical_list: D036383:Ephrin-A2; D011506:Proteins