Effect of EphA3 in retinal axon guidance

SCICOLONE G; ORTALLI AL; CARRI NG; LUJILDE N; ALVAREZ G; PASQUALE EB; FLORES V

San Diego, USA

Congreso; Society for Neuroscience, 34th Annual Meeting; 2004

Society for Neuroscience

  EFFECT OF EPHA3 IN RETINAL AXON GUIDANCE G.E.Scicolone1*; A.Ortalli1; N.Carri2; N.Lujilde1; G.Alvarez1; E.B.Pasquale3; V.Flores1 1. Inst Cell Biol, Med Sch. UBA, Bs As, Argentina 2. IMBICE, La Plata, Argentina 3. The Burnham Inst, La Jolla, CA, USA The retinotectal system is useful to study topographic map formation because nasal retinal ganglion cells connect to the caudal optic tectum and temporal ones connect to the rostral tectum in a spatially organized manner. Eph receptor tyrosine kinases and their ligands, the ephrins, are expressed in complementary gradients in both the retina and the tectum and help guide retinotectal projections to their targets. Ephrin-A ligands located in the caudal tectum repel temporal axons by activating the EphA3 receptor expressed on these axons. However, it is not known whether EphA3 expressed in the rostral tectum also participates in retinal axon guidance. Therefore, we investigated the effects of the extracellular domain of EphA3 fused to Fc on retinal ganglion cell neurite outgrowth in vitro. For these assays, we used dissociated retinal neurons and retinal explants prepared from chicken embryos at 6 days of development. We found that both nasal and temporal axons grow longer on EphA3 Fc than on Fc substrates and that this effect is concentration dependent. In addition, we performed time-lapse experiments to examine the behavior of growth cones extending on 293 cells transfected with EphA3 and on control transfected cells. These experiments showed that the majority of growth cones expand when contacting cells expressing EphA3 but not control cells. Furthermore, the majority of nasal growth cones extend on 293 cells expressing EphA3 while the majority of temporal growth cones adhere without extending. While EphA3 could influence nasal retinal axons by binding to ephrins expressed on these axons, the EphA3 target on temporal growth cones is unknown. Nevertheless, our results suggest that EphA3 expressed in the rostral optic tectum could promote nasal axon growth to the caudal tectum and adhesion of temporal axons to the rostral tectum.Support Contributed By: Antorchas, CONICET, UBA. Citation:G.E. Scicolone, A. Ortalli, N. Carri, N. Lujilde, G. Alvarez, E.B. Pasquale, V. Flores. EFFECT OF EPHA3 IN RETINAL AXON GUIDANCE Program No. 724.3. 2004 Abstract Viewer/Itinerary Planner. Washington, DC: Society for Neuroscience, 2004. Online. 2004 Copyright by the Society for Neuroscience all rights reserved. Permission to republish any abstract or part of any abstract in any form must be obtained in writing from the SfN office prior to publication