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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, JDuring 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.
History
Publication title
European Journal of NeuroscienceVolume
25Pagination
744-752ISSN
0953-816XDepartment/School
School of NursingPublisher
Blackwell Publishing LtdPlace of publication
9600 Garsington Rd, Oxford, England, Oxon, Ox4 2DgRights statement
Copyright 2007 The AuthorsRepository Status
- Restricted