Inactivation of axonal EphA4 stimulates axon growth of nasal retinal ganglion cells

DI NAPOLI, JENNIFER; FIORE, LUCIANO; ALONSO C; RODRIGUEZ CELIN, AJ; PASQUALE E.B.; CARRI, NÉSTOR GABRIEL; SCICOLONE, GABRIEL

New York

Congreso; SfN; 2010

SfN

Retinotopic projection onto the tectum constitutes the most detailed studied model of topographic mapping and Ephs and their ligands, the ephrins, constitute the main molecular system involved in this process. Ephrin-As, expressed in an increasing rostrocaudal gradient in the tectum, repel temporal retinal ganglion cells (RGCs) from the caudal tectum. Using retinal cultures and producing in vivo EphA3 misexpression, we demonstrated that EphA3, expressed in a decreasing rostrocaudal gradient in the tectum, stimulates the nasal axon growth toward the caudal tectum. Therefore, we proposed a general model for topographic mapping in which the same molecules functioning as membrane-bound ligands and receptors label both the topographic addresses onto the target and the relative sensitivity of the projections according to their topographic origin. However, it is not known which molecule/s mediates the EphA3-mediated effect on RGCs axons. We postulated that EphA4 activation decreases axon growth and that tectal EphA3 increases axon growth by reducing EphA4 activation through competing with axonal EphA4 for axonal ephrin-As binding.