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EphA5 and ephrin-A2 expression during optic nerve regeneration: a 'two-edged sword'

journal contribution
posted on 2023-05-18, 08:21 authored by Symonds, ACE, Carolyn KingCarolyn King, Bartlett, CA, Sauve, Y, Lund, RD, Beazley, LD, Dunlop, SA, Rodger, J
During development, gradients of EphA receptors (nasal(low)-temporal(high)) and their ligands ephrin-As (rostral(low)-caudal(high)) are involved in establishing topography between retinal ganglion cells (RGCs) and the superior colliculus (SC). EphA5-expressing RGC axons are repulsed by ephrin-A2-expressing SC neurones. In adult rats RGCs maintain graded EphA5 expression but ephrin-A2 expression is down-regulated in the SC to a weak gradient. At 1 month after optic nerve transection, EphA5 expression is reduced in the few remaining RGCs and is no longer graded; by contrast, SC ephrin-A2 is up-regulated to a rostral(low)-caudal(high) gradient. Here we examined expression in adult rat 1 month after bridging the retina and SC with a peripheral nerve graft, a procedure that enhances RGC survival and permits RGC axon regeneration. Double labelling with cell markers revealed preservation of a nasal(low)-temporal(high) EphA5 gradient in RGCs and establishment of a rostral(low)-caudal(high) ephrin-A2 gradient within neurones of the SC. The results suggest a potential for guidance cues to restore the topography of RGC axons in the SC. However, high ephrin-A2 levels were also found in astrocytes surrounding the peripheral nerve graft insertion site. The repulsive ephrin-A2 environment offers at least a partial explanation for the observation that only a limited number of RGC axons can exit the graft to enter target central nervous system tissue.


Publication title

European Journal of Neuroscience








School of Nursing


Blackwell Publishing Ltd

Place of publication

9600 Garsington Rd, Oxford, England, Oxon, Ox4 2Dg

Rights statement

Copyright 2007 The Authors

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Clinical health not elsewhere classified

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