EPHRIN-A MEDIATES EYE-SPECIFIC PATTERNING OF RETINOGENICULATE PROJECTIONS IN REWIRED MICE
1. Dept Brain & Cognitive Sci, 2. Center for Learning and Memory, Massachusetts Inst Technology, Cambridge, MA, USA
In neonatal mice, deafferentation of the medial geniculate nucleus (MGN) induces its innervation by retinal ganglion cells. Previous work in mice demonstrated that these rewired visual projections show eye-specific segregation in the MGN. To examine factors that control the patterning of rewired projections, we injected red and green Alexa Fluor conjugated CtB into the right and left eyes, respectively, of rewired adult mice. Projections were examined using confocal microscopy. The rewired ipsilateral projection is biased toward the posterior quarter of the MGN. Ephrin-A2 and -A5 are expressed in a high anterolateral, low posteromedial gradient in the LGN and MGN. Ipsilateral projections, which arise from the ventro-temporal retina, innervate areas of low ephrin expression in the LGN. We rewired ephrin-A2/A5 double knockout mice and examined the eye-specific projections in the MGN. Rewiring is quantitatively enhanced in the double knockout. Moreover, 1) the proportion of ipsilateral projections in the MGN is preferentially enhanced compared to wildtype mice; and 2) there is an equal representation of ipsilateral projections in the anterior and posterior MGN. These findings suggest that ephrin ligands contribute to the patterning of visual projections in a novel target.
Supported by: March of Dimes and NIH EY11512.