Difference between revisions of "Wiring The Brain"
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:The highly ordered wiring of retinal ganglion cell (RGC) neurons in the retina to neurons in the superior colliculus of the midbrain has long served as the dominant experimental system for the analysis of topographic neural maps. These maps are comprised of axonal connections in which the positional coordinates of a set of input neurons are mapped onto the corresponding coordinates of their targets. They are a feature of nearly all sensory modalities, including sight, touch, sound, taste and smell, and are seen throughout the nervous system. We describe a quantitative model for the development of one arm of the retinocollicular (retinotectal) map: the wiring of the nasal-temporal axis of the retina to the posterior-anterior axis of the SC. The model is based RGC-RGC competition that is governed by comparisons of the signaling intensity experienced by retinal ganglion cells expressing differing levels of EphA receptor protein-tyrosine kinases, whose expression is exponentially graded across the nasal-temporal axis of the retina. These comparisons are made using ratios of, rather than absolute differences in, EphA signaling intensity. Molecular genetic experiments, exploiting a combination of EphA receptor knock-in and knock-out mice, confirm the salient predictions of this 'Relative Signaling' model, and demonstrate that it both describes and predicts topographic mapping. | :The highly ordered wiring of retinal ganglion cell (RGC) neurons in the retina to neurons in the superior colliculus of the midbrain has long served as the dominant experimental system for the analysis of topographic neural maps. These maps are comprised of axonal connections in which the positional coordinates of a set of input neurons are mapped onto the corresponding coordinates of their targets. They are a feature of nearly all sensory modalities, including sight, touch, sound, taste and smell, and are seen throughout the nervous system. We describe a quantitative model for the development of one arm of the retinocollicular (retinotectal) map: the wiring of the nasal-temporal axis of the retina to the posterior-anterior axis of the SC. The model is based RGC-RGC competition that is governed by comparisons of the signaling intensity experienced by retinal ganglion cells expressing differing levels of EphA receptor protein-tyrosine kinases, whose expression is exponentially graded across the nasal-temporal axis of the retina. These comparisons are made using ratios of, rather than absolute differences in, EphA signaling intensity. Molecular genetic experiments, exploiting a combination of EphA receptor knock-in and knock-out mice, confirm the salient predictions of this 'Relative Signaling' model, and demonstrate that it both describes and predicts topographic mapping. | ||
| − | [[image:lemke. | + | [[image:lemke.jpg|Prof. Greg Lemke]] |
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Revision as of 22:55, 5 July 2009
By Prof. [Greg Lemke], Head of Molecular Neurobiology Laboratory, The Salk Institute
July 21, 2009
For us to be able to see, specific cells in our retinas must be connected in a regular fashion to specific cells in our brains. How does the brain achieve it? How does it reproducibly wire its billions of nerve cells together during embryonic development? This lectures describes how the visual system uses variable abundances of a set of receptors - called EPH proteins - to connect the eye to the brain in a regular, reproducible fashion that allows us to see.
Prof. Lemke will be introduced by Dr. Ilya Nemenman, Staff Scientist, Los Alamos National Laboratory.
- Abstract
- The highly ordered wiring of retinal ganglion cell (RGC) neurons in the retina to neurons in the superior colliculus of the midbrain has long served as the dominant experimental system for the analysis of topographic neural maps. These maps are comprised of axonal connections in which the positional coordinates of a set of input neurons are mapped onto the corresponding coordinates of their targets. They are a feature of nearly all sensory modalities, including sight, touch, sound, taste and smell, and are seen throughout the nervous system. We describe a quantitative model for the development of one arm of the retinocollicular (retinotectal) map: the wiring of the nasal-temporal axis of the retina to the posterior-anterior axis of the SC. The model is based RGC-RGC competition that is governed by comparisons of the signaling intensity experienced by retinal ganglion cells expressing differing levels of EphA receptor protein-tyrosine kinases, whose expression is exponentially graded across the nasal-temporal axis of the retina. These comparisons are made using ratios of, rather than absolute differences in, EphA signaling intensity. Molecular genetic experiments, exploiting a combination of EphA receptor knock-in and knock-out mice, confirm the salient predictions of this 'Relative Signaling' model, and demonstrate that it both describes and predicts topographic mapping.
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