Complementary gradients in expression and binding of ELF-1 and Mek4 in development of the topographic retinotectal projection map.
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.
Cheng
H J
HJ
Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA.
Nakamoto
M
M
Bergemann
A D
AD
Flanagan
J G
JG
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*
D036383:Ephrin-A2; D011506:Proteins