Neuron
Volume 39, Issue 6, 11 September 2003, Pages 919-935
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Article
Ephrin-B2 and EphB1 Mediate Retinal Axon Divergence at the Optic Chiasm

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Abstract

In animals with binocular vision, retinal ganglion cell (RGC) axons either cross or avoid the midline at the optic chiasm. Here, we show that ephrin-Bs in the chiasm region direct the divergence of retinal axons through the selective repulsion of a subset of RGCs that express EphB1. Ephrin-B2 is expressed at the mouse chiasm midline as the ipsilateral projection is generated and is selectively inhibitory to axons from ventrotemporal (VT) retina, where ipsilaterally projecting RGCs reside. Moreover, blocking ephrin-B2 function in vitro rescues the inhibitory effect of chiasm cells and eliminates the ipsilateral projection in the semiintact mouse visual system. A receptor for ephrin-B2, EphB1, is found exclusively in regions of retina that give rise to the ipsilateral projection. EphB1 null mice exhibit a dramatically reduced ipsilateral projection, suggesting that this receptor contributes to the formation of the ipsilateral retinal projection, most likely through its repulsive interaction with ephrin-B2.

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5

Present address: INSERM U382, Campus de Luminy, 13288 Marseille Cedex 09, France.

6

Present address: Departments of Visual Science and Molecular Genetics, Institute of Ophthalmology, University College London, London EC1V 9EL, United Kingdom.

7

Present address: Department of Neurobiology and Neurology, Mount Sinai School of Medicine, New York, New York 10029.

8

Present address: Department of Pathology, Stanford University School of Medicine, Stanford, California 94305.