"We found very strong evidence that this signaling protein directs the development of the cortex," said Fukuchi-Shimogori. With increased expression of this protein the sizes and locations of the areas changed. Areas that are towards the front of the cortex and closer to the source of the molecule were enlarged at the expense of areas further away from the source. Reducing the signaling protein caused shifts in the opposite direction. "Most dramatic, when a new source of the signaling protein was generated close to the back of the embryonic cortex, the whole program changed," said Grove. "Now, a region near the back of the cortex was reprogrammed to form a duplicate of a more central region, a second touch area. We saw a identical array of patches that correspond on a one-to-one basis with the mouse's whiskers." (see illustration) The generation of a new cortical area by a molecular manipulation has not been seen before and may provide a clue about how the cerebral cortex changes in evolution. One way that evolution seems to generate more functionally complex brains is by adding new areas to the cortex.

"We have had no idea how evolution achieved this kind of change," said Grove. "So it is exciting to find that you can add a new area by modifying signaling by a single protein."

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Contact: Jeanne Galatzer-Levy
jgalatz@uchospitals.edu
773-702-6241
University of Chicago Medical Center
20-Sep-2001