CONICET | Buscador de Institutos y Recursos Humanos

Introduction EphAs and ephrinAs play a key role in the establishment of retinotopic projections onto the optic tectum (OT). Still, their developmental pattern of expression has not been described in detail. Objective Our objective was to describe the developmental pattern of expression of EphA3 and ephrinA2 in the chicken retinotectal system. Methods We used immunocytochemistry in cultured retinal explants and in paraffinsections since 3 days embryos (E3) to postnatal day 2 (P2). Results EphA3 and ephrinA2 are expressed in the plasma membrane of neuroepithelial cells of the retina and the OT since E5. As lamination processoccurs, they are seen along all the radial retinal and tectal extension. The differential expression patterns of the EphA3 and the ephrinA2 in the retinal ganglion cells (RGCs) and in the intermediate and superficial layers of the OT might lead to the opposed gradients observed along the temporo-nasal axis in the retina and along the rostro-caudal axis in the OT, respectively. EphA3 gradients are noticed since E6 to E18 while ephrin-A2 gradients are evident since E6 to P2 in the retina and between E5 and P2 in the OT. In both organs differentiated postmigratory neurons present a patch-like expression pattern of EphA3 and ephrinA2 whereas ephrinA2 presents the same pattern in premigratory cells. Discussion EphA3 and ephrinA2 present differential developmental patterns of expression, but both of them are high when axon guidance of RGCs takes place over tectal surface. The disappearance of EphA3 gradient could be one of the reasons of lack of regeneration in adult chicken retinotectal system. Hence, manipulationof this system could be useful in regenerative strategies. Funded by CONICET and UBA.