The Journal of Neuroscience, October 1, 2001, 21(19):7684-7690
Enhanced Plasticity of Retinothalamic Projections in an
Ephrin-A2/A5 Double Mutant
Alvin W.
Lyckman1,
Sonal
Jhaveri1,
David A.
Feldheim2,
Pierre
Vanderhaeghen2, 3,
John G.
Flanagan2, and
Mriganka
Sur1
1 Department of Brain and Cognitive Science,
Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, 2 Department of Cell Biology and Program in Neuroscience,
Harvard Medical School, Boston, Massachusetts 02115, and
3 Institute of Interdisciplinary Research, University of
Brussels, B-1070 Brussels, Belgium
Ascending sensory information reaches primary sensory cortical
areas via thalamic relay neurons that are organized into
modality-specific compartments or nuclei. Although the sensory relay
nuclei of the thalamus show consistent modality-specific segregation of
afferents, we now show in a wild-type mouse strain that the
visual pathway can be surgically "rewired" so as to induce
permanent retinal innervation of auditory thalamic cell groups.
Applying the same rewiring paradigm to a transgenic mouse lacking the
EphA receptor family ligands ephrin-A2 and ephrin-A5 results in more
extensive rewiring than in the wild-type strain. We also show for the
first time that ephrin-A2 and ephrin-A5 define a distinct border
between visual and auditory thalamus. In the absence of this
ephrin-A2/A5 border and after rewiring surgery, retinal afferents are
better able to invade and innervate the deafferented auditory thalamus. These data suggest that signals that induce retinal axons to innervate the denervated auditory thalamus may compete with barriers, such as the
ephrins, that serve to contain them within the normal target. The
present findings thus show that the targeting of retinothalamic projections can be surgically manipulated in the mouse and that such
plasticity can be controlled by proteins known to regulate topographic mapping.
Key words:
medial geniculate body; medial geniculate nucleus; inferior colliculus; cross-modal; rewiring; compartmentalization; ephrins; Eph receptors; target specificity
Copyright © 2001 Society for Neuroscience 0270-6474/01/21197684-07$05.00/0