We report that EphB receptors direct unique axonal behaviors required for mapping the dorsal-ventral (D-V) retinal axis along the lateral-medial (L-M) axis of the superior colliculus (SC). EphBs are expressed in a D-V gradient, ephrin-B1 in a L-M gradient in SC, and ephrin-B3 at its midline. EphBs and ephrin-Bs are expressed in countergradients in retina and SC. Developmental analyses reveal that retinal axons lack D-V ordering along the L-M axis, but directionally extend branches along it to establish ordered arbors. Directed branch extension is disrupted in EphB2; EphB3-deficient mice resulting in lateral ectopic arbors. Mice with kinase-inactive EphB2 have similar D-V mapping defects indicating that forward signaling dominates over reverse signaling. Our data suggest that branches of EphB expressing axons are attracted medially by ephrin-B1, and provide molecular mechanisms for D-V mapping in visual centers.
Hindges, R., McLaughlin, T., Genoud, N., Henkemeyer, M., & O’Leary, D. D. M. (2002). EphB forward signaling controls directional branch extension and arborization required for dorsal-ventral retinotopic mapping. Neuron, 35(3), 475–487. https://doi.org/10.1016/S0896-6273(02)00799-7