Dr Polleux’s group in the Neuroscience Center has recently published an article in the Public Access journal PLoS Biology (june 2008 issue) reporting the critical role of Netrin-1 signaling in the establishment of the topography of thalamocortical projections.
The first author on this study is Ashton Powell (left), a student from the UNC Neurobiology Curriculum who recently graduated.

The functional properties of each structure in the central nervous system are critically dependent on the precision of neuronal connectivity. The cerebral cortex in particular is a highly organized structure divided in many distinct cortical areas underlying important sensory, motor and cognitive functions in the brain. Each primary cortical area receives its synaptic inputs from the periphery via the dorsal thalamus. The thalamus is therefore the main relay station for sensory information to the cortex and can be divided in specific nuclei projecting topographically to individual cortical areas. How is the complex topography of thalamic axon projection to individual cortical areas specified during development? Recent evidence demonstrated that thalamic axons are routed to different cortical ‘domains’ before they enter the cortex, by putative axon guidance cues present in the ventral forebrain. In the present study, we provide evidence that a secreted axon guidance cue, Netrin-1, expressed in a long-range gradient in the ventral forebrain, plays a critical role in the establishment of the topography of thalamic projections by directing different subsets of axons to specific cortical domains. These results provide important insights into the molecular mechanisms patterning the topography of thalamocortical axon projections in mammals.

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